Blood and Blood Vessels

Module 17.3: Red blood cell production and recycling• RBC production and recycling

• Events occurring in red bone marrow• Blood cell formation (erythropoiesis) occurs only in red

bone marrow (myeloid tissue)• Located in vertebrae, ribs, sternum, skull, scapulae, pelvis, and

proximal limb bones

• Fatty yellow bone marrow can convert to red bone marrow in cases of severe, sustained blood loss

• Developing RBCs absorb amino acids and iron from bloodstream and synthesize Hb

Module 17.3: Red blood cell production and recycling

• Stages• Proerythroblasts• Erythroblasts

• Actively producing Hb• After four days becomes normoblast

• Reticulocyte (80% of mature cell Hb)• Ejects organelles including nucleus• Enters bloodstream after two days• After 24 hours in circulation, is mature RBC

Module 17.3: Red blood cell production and recycling• Events occurring at macrophages

• Engulf old RBCs before they rupture (hemolyze)• Hemoglobin recycling

• Iron• Stored in phagocyte• Released into bloodstream attached to plasma protein

(transferrin)

• Globular proteins disassembled into amino acids for other uses

• Heme biliverdin bilirubin bloodstream • Hemoglobin not phagocytized breaks down into protein

chains and eliminated in urine (hemoglobinuria)

Module 17.3: Red blood cell production and recycling

• Events occurring at liver• Bilirubin excreted into bile

• Accumulating bile due to diseases or disorders can lead to yellowish discoloration of eyes and skin (jaundice)

• Events occurring at the large intestine• Bacteria convert bilirubin to urobilins and

stercobilins which become part of feces• Give feces yellow-brown or brown coloration

Module 17.3: Red blood cell production and recycling• Events occurring at kidneys

• Excrete some hemoglobin and urobilins• Give urine its yellow color

• Presence of intact RBCs in urine (hematuria)• Only after urinary tract damage

Figure 17.3

Events in the life cycle of RBCs

Events Occurring inMacrophages

Macrophages in liver,spleen, and bone marrow

Fe2+

90%

10%

Fe2+ transported in circulationby transferrin

Average life span ofRBC is 120 days

Old anddamagedRBCs In the bloodstream,

the rupture of RBCsis called hemolysis.

Heme

Biliverdin

Bilirubin

Amino acids

Bilirubin boundto albumin inbloodstream

Bilirubin

Hemoglobin that is not phagocytizedbreaks down, and the alpha and betachains are eliminated in urine. Whenabnormally large numbers of RBCsbreak down in the bloodstream, urinemay turn red or brown. This conditionis called hemoglobobinuria.

Liver

Excretedin bile

Bilirubin

Events Occurring inthe Liver

Events Occurring in the Large Intestine

Urobilins,sterconilins

Eliminatedin feces

Absorbed into the circulation

Eliminatedin urine

Urobilins

Hb

Events Occurring in the Kidney

New RBCsreleased intocirculation

RBCformation

Ejection ofnucleus

Events Occurring in the Red Bone Marrow

Developing RBCs absorb aminoacids and Fe2+ from the bloodstreamand synthesize new Hb molecules.

Cells destines to become RBCs firstdifferentiate into proerythroblasts.

Proerythroblasts then differentiateinto various stages of cells callederythroblasts, which activelysynthesize hemoglobin.Erythroblasts are namedaccording to total size, amount ofhemoglobin present, and size andappearance of the nucleus.

After roughly four days of differentiation, theerythroblast, now called a normoblast, shedsits nucleus and becomes a reticulocyte(re-TIK-ū-lō-sīt), which contains 80 percent ofthe Hb of mature RBC.

After two days in the bone marrow,reticulocytes enter the bloodstream. After 24hours in circulation, the reticulocytescomplete their maturation and becomeindistinguishable from other mature RBCs.

Start

Module 17.3 Reviewa. Define hemolysis.

b. Identify the products formed during the breakdown of heme.

c. In what way would a liver disease affect the level of bilirubin in the blood?

Module 17.4: Blood types• Blood types

• Determined by presence or absence of cell surface markers (antigens)

• Are genetically determined glycoproteins or glycolipids• Can trigger a protective defense mechanism (immune

response)• Identify blood cells as “self” or “foreign” to immune system• More than 50 blood cell surface antigens exist

• Three particularly important• A, B, Rh (or D)

Module 17.4: Blood types• Four blood types (AB antigens)

1. Type A (A surface antigens)• Anti-B antibodies in plasma

2. Type B (B surface antigens)• Anti-A antibodies in plasma

3. Type AB (Both A and B surface antigens)• No anti-A or anti-B antibodies in plasma

4. Type O (no A or B surface antigens)• Both anti-A and anti-B antibodies in plasma

Figure 17.4 1

The characteristics of blood for each of the four blood types

Type A Type AB Type O

Type O blood has RBCslacking both A and Bsurface antigens.

Type A blood has RBCswith surface antigen A only.

Type B blood has RBCswith surface antigen B only.

Type AB blood has RBCswith both A and B surfaceantigens.

Type B

Surfaceantigen A

Surfaceantigen B

If you have Type A blood,your plasma contains anti-Bantibodies, which will attackType B surface antigens.

If you have Type B blood,your plasma contains anti-Aantibodies.

If you have Type AB blood,your plasma has neitheranti-A nor anti-B antibodies.

If you have Type O blood,your plasma contains bothanti-A and anti-B antibodies.

Module 17.4: Blood types• Rh surface antigens

• Separate antigen from A or B• Presence or absence on RBC determines positive or

negative blood type respectively• Examples: AB+, O–

Figure 17.4 3

Module 17.4 Review

a. What is the function of surface antigens on RBCs?

b. Which blood type(s) can be safely transfused into a person with Type O blood?

CLINICAL MODULE 17.5: Newborn hemolytic disease• Newborn hemolytic disease

• Genetically determined antigens mean that a child can have a blood type different from either parent

• During pregnancy, the placenta restricts direct transport between maternal and infant blood

• Anti-A and anti-B antibodies are too large to cross• Anti-Rh antibodies can cross

• Can lead to mother’s antibodies attacking fetal RBCs

CLINICAL MODULE 17.5: Newborn hemolytic disease• First pregnancy with Rh– mother and Rh+ infant

• During pregnancy, few issues occur because no anti-Rh antibodies exist in maternal circulation

• During birth, hemorraging may expose maternal blood to fetal Rh+ cells

• Leads to sensitization or activation of mother’s immune system to produce anti-Rh antibodies

Figure 17.5

First Pregnancy of an Rh– Motherwith an Rh+ infant

The most common form of hemolytic disease ofthe newborn develops after an Rh– women hascarried an Rh+ fetus.

Problems seldom develop during afirst pregnancy, because very few fetalcells enter the maternal circulationthen, and thus the mother’s immunesystem is not stimulated to produceanti-Rh antibodies.

Exposure to fetal red blood cellantigens generally occurs duringdelivery, when bleeding takes place atthe placenta and uterus. Such mixingof fetal and maternal blood canstimulate the mother’s immune systemto produce anti-Rh antibodies, leadingto sensitization.

Roughly 20 percent of Rh– motherswho carried Rh+ children becomesensitized within 6 months of delivery.Because the anti-Rh antibodies are notproduced in significant amounts untilafter delivery, a woman’s first infant isnot affected.

During First Pregnancy

Hemorrhaging at Delivery

Maternal Antibody Production

Rh antigen onfetal red blood cells

Maternal antibodiesto Rh antigen

Maternal blood supplyand tissue

Fetal blood supplyand tissue

Maternal blood supplyand tissue

Fetal blood supplyand tissue

Maternal blood supplyand tissue

Placenta

Rh+

fetus

Rh–

mother

CLINICAL MODULE 17.5: Newborn hemolytic disease• Second pregnancy with Rh– mother and Rh+ infant

• Subsequent pregnancy with Rh+ infant can allow maternal anti-Rh antibodies to cross placental barrier

• Attack fetal RBCs and cause hemolysis and anemia• = Erythroblastosis fetalis

• Full transfusion of fetal blood may be necessary to remove maternal anti-Rh antibodies

• Prevention• RhoGAM antibodies can be administered to maternal

circulation at 26–28 weeks and before/after birth• Destroys any fetal RBCs that cross placenta• Prevents maternal sensitization

Figure 17.5

During Second Pregnancy

Rh–

mother

Rh+

fetus

Maternal blood supplyand tissue

Fetal blood supplyand tissue

Maternal anti-Rhantibodies

Hemolysis offetal RBCs

Second Pregnancy of an Rh– Motherwith an Rh+ Infant

If a subsequent pregnancy involves an Rh+ fetus,maternal anti-Rh antibodies produced after thefirst delivery cross the placenta and enter thefetal bloodstream. These antibodies destroyfetal RBCs, producing a dangerous anemia.The fetal demand for blood cells increases,and they begin leaving the bone marrow andentering the bloodstream before completingtheir development. Because these immatureRBCs are erythroblasts, HDN is also knownas erythroblastosis fetalis. Fortunately, themother’s anti-Rh antibody production canbe prevented if such antibodies (availableunder the name RhoGAM) are administeredto the mother in weeks 26–28 of pregnancyand during and after delivery. Theseantibodies destroy any fetal RBCs thatcross the placenta before they can stimulatea maternal immune response. Becausematernal sensitization does not occur, noanti-Rh antibodies are produced.

CLINICAL MODULE 17.5 Reviewa. Define hemolytic disease of the newborn (HDN).

b. Why is RhoGAM administered to Rh– mothers?

Module 17.6: White blood cells• White blood cells (leukocytes)

• Spend only a short time in circulation• Mostly located in loose and dense connective tissues where

infections often occur• Can migrate out of bloodstream

• Contact and adhere to vessel walls near infection site• Squeeze between adjacent endothelial cells• = Emigration • Are attracted to chemicals from pathogens, damaged tissues, or

other WBCs• = Positive chemotaxis

Module 17.6: White blood cells• White blood cell types

1. Granular leukocytes (have cytoplasmic granules)• Neutrophil• Eosinophil• Basophil

2. Agranular leukocytes (lacking cytoplasmic granules)• Monocyte• Lymphocyte

• Changing populations of different WBC types associated with different conditions can be seen in a differential WBC count

Module 17.6: White blood cells• Granular leukocytes

• Neutrophils• Multilobed nucleus• Phagocytic cells that engulf pathogens and debris

• Eosinophils• Granules generally stain bright red• Phagocytic cells that engulf antibody-labeled materials

• Increase abundance with allergies and parasitic infections

• Basophils• Granules generally stain blue• Release histamine and other chemicals promoting

inflammation

Figure 17.6

The structure and function of whiteblood cells (leukocytes)

GRANULAR LEUKOCYTES

Neutrophil

Eosinophil

Basophil

AGRANULAR LEUKOCYTES

Monocyte

Lymphocyte

WBCs can bedivided intotwo classes

Shared Properties of WBCs• WBCs circulate for only a short portion of their life span, using the bloodstream primarily to travel between organs and to rapidly reach areas of infection or injury. White blood cells spend most of their time migrating through loose and dense connective tissues throughout the body.

• All WBCs can migrate out of the bloodstream. When circulating white blood cells in the bloodstream become activated, they contact and adhere to the vessel walls and squeeze between adjacent endothelial cells to enter the surrounding tissue. This process is called emigration, or diapedesis (dia, through; pedesis, a leaping).

• All WBCs are attracted to specific chemical stimuli. This characteristic, called postive chemotaxis (kē-mō-TAK-sis), guides WBCs to invading pathogens, damaged tissues, and other active WBCs. • Neutrophils, eosinophils, and monocytes are capable of phagocytosis. These phagocytes can engulf pathogens, cell debris, or other materials. Macrophages are monocytes that have moved out of the bloodstream and have become actively phagocytic.

Module 17.6: White blood cells• Agranular leukocytes

• Monocytes• Large cells with bean-shaped nucleus• Enter tissues and become macrophages

(phagocytes)

• Lymphocytes• Slightly larger than RBC with large round nucleus• Provide defense against specific pathogens or toxins

Module 17.6 Review

a. Identify the five types of white blood cells.

b. How do basophils respond during inflammation?

Module 17.7: Formed element production• Formed elements

• Appropriate term since platelets are cell fragments

• Platelets• Structure: flattened

discs that appear round when viewed from top but spindle-shaped in blood smear

• Function: clump together and stick to damaged vessel walls where they release clotting chemicals

• Immediate precursor cell is megakaryocyte (mega-, big + karyon, nucleus + -cyte, cell)

Module 17.8: Hemostasis• Hemostasis (haima, blood + stasis, halt)

• Stops blood loss from damaged blood vessel walls• Establishes framework for tissue repairs

Fig. 18.1

Neutrophil

Erythrocyte

Eosinophil

Monocyte

Neutrophil

Basophil

Neutrophil

Platelets

Monocyte

Smalllymphocyte

Young (band)neutrophil

Smalllymphocyte

Largelymphocyte

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Section 2: Functional Anatomy of Blood Vessels• Blood vessels conduct blood between heart and

peripheral tissues• Two circuits

1. Pulmonary circuit (to and from lungs)2. Systemic circuit (to and from rest of body)• Each circuit begins and ends with heart

• Occur in sequence

Section 2: Functional Anatomy of Blood Vessels• Specific vessels

• Arteries (transport blood away from heart)• Veins (transport blood to the heart)• Capillaries (exchange substances between blood

and tissues)• Interconnect smallest arteries and smallest veins

Section 2: Functional Anatomy of Blood Vessels• General circulation pathway through circuits

1. Right atrium (entry chamber) from systemic circuit to right ventricle, to pulmonary circuit

2. Pulmonary circuit• Pulmonary arteries to pulmonary capillaries to pulmonary

veins3. Left atrium from pulmonary circuit to left ventricle, to

systemic circuit4. Systemic circuit

• Systemic arteries to systemic capillaries to systemic veins

Figure 17 Section 2

Module 17.10: Arteries and veins

• Both arteries and veins have three layers1. Tunica intima (tunica interna)

• Innermost layer• Endothelial cells with connective tissue with elastic

fibers• In arteries, outer margin has layer of elastic fibers

(internal elastic membrane)

2. Tunica media • Middle layer• Contains concentric sheets of smooth muscle

• Capable of vasoconstriction or vasodilation• Collagen fibers connect tunica media to other layers

Module 17.10: Arteries and veins• Both arteries and veins have three layers

(continued)3. Tunica externa

• Outermost layer• Connective tissue sheath with collagen and elastic

fibers• Generally thicker in veins• Anchor vessel to surrounding tissues

Figure 17.10 1

LM x 60

Vein

Artery

A photomicrograph of an arteryand an adjacent vein

Figure 17.10 1

The structure of the wall of an artery

Artery

Tunica intima

Tunica media

Tunica externa

Smoothmuscle

Internal elasticmembrane

Externalelasticmembrane

Endothelium

Elastic fiber

Figure 17.10 1

Tunica externa

Tunica media

Tunica intima

Endothelium

Smooth muscle

VeinThe structure of the wall of a vein

Module 17.10: Arteries and veins• Five general blood vessel classes

1. Arteries• Elastic arteries (large vessels close to the heart

that stretch and recoil when heart beats)• Muscular arteries (medium-sized arteries,

distribute blood to skeletal muscles and internal organs)

2. Arterioles• Poorly defined tunica externa and tunica media

only 1–2 smooth muscle cells thick3. Capillaries

• Thin, exchange vessels

Module 17.10: Arteries and veins• Five general blood vessel classes (continued)

4. Venules (small veins lacking tunica media, collect blood from capillaries)

5. Veins • Medium-sized veins (tunica media is thin but tunica

externa is thick with longitudinal collagen and elastic fibers)

• Large veins (superior and inferior venae cavae and tributaries having thin tunica media)

Figure 17.10 2

The five general classes of blood vessels:arteries, arterioles, capillaries, venules, and veins

Large Veins

Medium-sized Veins

Venules

Capillaries

Arterioles

Muscular Arteries

Elastic Arteries

Large vessels that transport blood away fromthe heart; include the pulmonary trunk andthe aorta and its major branches; are resilent,elastic vessels capable of stretching and recoiling as the heart beats and arterial pressures change

Internal elastic layer

Tunica intimaTunica mediaTunica externa

Tunica intima

Tunica media

Tunica externa

Medium-sized arteries that distribute bloodto the body’s skeletal muscles and internalorgans

Have a poorly defined tunica externa, and the tunica media consists of only one or two layers of smooth muscle cells

Smooth muscle cells

Endothelium

The only blood vessels whose walls permit exchangebetween the blood and the surrounding interstitial

fluids due to thin walls and shortdiffusion distances

Endothelial cells

Basal laminaBasal lamina

Endothelial cells

Pores

EndotheliumTunica externa

Tunica externaTunica mediaTunica intima

Collect blood from capillary beds and are thesmallest venous vessels; those smaller than50 μm lack a tunica media andresemble expanded capillaries

Range from 2 to 9 mm in internal diameter;the tunica media is thin and containsrelatively few smooth muscle cells; thethickest layer is the tunica externa, whichcontains longitudinal bundles ofelastic and collagen fibers

Include the superior and inferior venae cavaeand their tributaries; contain all three vesselwall layers; have a slender tunica mediacomposed of a mixture of elastic andcollagen fibers

Tunica externaTunica mediaTunica intima

Module 17.10 Review

a. List the five general classes of blood vessels.

b. Describe a capillary.

c. A cross section of tissue shows several small, thin-walled vessels with very little smooth muscle tissue in the tunica media. Which type of vessels are these?

Module 17.11: Capillaries• Typical capillary consists of tube of endothelial cells

with delicate basal lamina• Neither tunica intima nor externa are present

• Average diameter = 8 µm• About the same as an RBC

• Two major categories1. Continuous capillaries2. Fenestrated capillaries

Module 17.11: Capillaries• Continuous capillaries

• Endothelium is a complete lining• Located throughout body in all tissues except epithelium

and cartilage• Permit diffusion of water, small solutes, and lipid-soluble

materials• Prevent loss of blood cells and plasma proteins• Some selective vesicular transport

• Some capillaries have endothelial tight junctions• Restricted and regulated permeability

Module 17.11: Capillaries• Fenestrated capillaries

• Contain windows or pores penetrating endothelium• Permit rapid exchange of water and larger solutes• Examples: capillaries in brain and endocrine organs,

absorptive areas of GI tract, kidney filtration sites

Figure 17.11 1 – 2

The two major types of capillaries:continuous capillaries and fenestrated capillaries

Basal lamina

Endothelial cell

Nucleus

A continuous capillary A fenestrated capillary

Basallamina

Boundarybetween

endothelialcells

Vesicles containingmaterials transported

across the endothelial cell

Boundarybetween

endothelialcells

Basallamina

Fenestrations,or pores

Module 17.11: Capillaries• Sinusoids

• Resemble fenestrated capillaries that are flattened and irregularly shaped

• Commonly have gaps between endothelial cells• Basal lamina is thin or absent• Permit more water and solute (plasma proteins)

exchange• Occur in liver, bone marrow, spleen, and many endocrine

organs

Figure 17.11 3

A sinusoid

Gap betweenadjacent cells

Module 17.11: Capillaries• Capillary bed

• Network of capillaries with several connections between arterioles and venules

• Can have collateral arteries (functionally redundant) fusing to one arteriole (forming an arterial anastomosis) leading to capillary bed

• Can be bypassed by arteriovenous anastomosis that directly connects arteriole to venule

Module 17.11: Capillaries• Capillary bed (continued)

• Thoroughfare channels (direct passages through capillary bed)

• Begin with metarteriole segment that can constrict or dilate to control flow

• Has multiple capillaries connecting to venules• Have bands of smooth muscle (precapillary sphincters) to

control flow into capillary bed• Vasomotion (cycling contraction and relaxing changing

capillary bed flow)

Figure 17.11 4

Smoothmuscle cells

Precapillarysphincter

Arteriovenousanastomosis

Precapillary sphincters

Arteriole Metarteriole

Variableblood flow

Continuousblood flow

KEY

Smallvenules

Thoroughfarechannel

Capillaries

Venule

Vein

Collateral arteries

A capillary bed

Module 17.11 Review

a. Identify the two types of capillaries.

b. At what sites in the body are fenestrated capillaries located?

c. Why do capillaries permit the diffusion of materials, whereas arteries and veins do not?

Module 17.12: Venous functional anatomy• Venous functional anatomy and pressure

• Blood pressure in venules and medium veins is <10% of that in ascending aorta (largest artery)

• These vessels contain valves (folds of tunica intima) that ensure one-way flow of blood toward heart

• Malfunctioning valves can lead to varicose veins (enlarged superifical thigh and leg veins) or distortion of adjacent tissues (hemorrhoids)

Figure 17.12 1

Module 17.12: Venous functional anatomy• Increasing venous blood flow

• Skeletal muscle contractions squeezing veins with valves

• Sympathetically controlled constriction of veins (venoconstriction)

• Venoconstriction can maintain arterial blood volume despite hemorrhaging

Figure 17.12 2

• Total blood volume distribution

• Unevenly distributed between arteries, veins, and capillaries

• Systemic venous system contains nearly 2/3 of total blood volume (~3.5 L)

• Of that , ~1 L is in venous networks of liver, bone marrow, and skin

venous

Systemicvenoussystem Pulmonary

circuit

Heart

Systemicarterialsystem

Systemiccapillaries

The distribution of blood volume within the body

Module 17.12 Review

a. Define varicose veins.

b. Why are valves located in veins, but not in arteries?

c. How is blood pressure maintained in veins to counter the force of gravity?

Module 17.13: Pulmonary circuit

• Arteries of pulmonary circuit differ from those in systemic circuit

• Pulmonary arteries carry deoxygenated bloodRight ventricle pulmonary trunk (large artery) pulmonary arteries pulmonary arterioles pulmonary capillaries (surrounded by alveoli, where gas exchange occurs) pulmonary venules pulmonary veins left atrium

Fig. 19.1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Systemic circuit

Pulmonary circuit

O2-poor,CO2-richblood

O2CO2

O2-rich,CO2-poorblood

CO2 O2

Figure 17.13 3

Ascending aorta

Superior vena cava

Right lung

Rightpulmonary

arteries

Rightpulmonary

veins

Inferior vena cava

Descending aorta

Aortic arch

Pulmonary trunk

Left lung

Leftpulmonaryarteries

Leftpulmonaryveins

Alveolus

Capillary

The path of blood flow through the pulmonary circuit

Module 17.13: Pulmonary circuit• Major patterns of blood vessel organization

1. Peripheral arteries and veins are generally identical between left and right sides except near heart

2. Vessels change names as they branch or move into new areas

3. Tissues and organs are usually served by many arteries and veins

• Anastomoses reduce impact of potential blockages (occlusions)

Module 17.13 Review

a. Identify the two circulatory circuits of the cardiovascular system.

b. Briefly describe the three major patterns of blood vessel organization.

c. Trace a drop of blood through the lungs, beginning at the right ventricle and ending at the left atrium.

Module 17.14: Systemic vessels• Systemic vessels

• Arterial system• Originates from aorta (largest elastic vessel exiting left

ventricle)

• Venous system• All drain into:

• Superior vena cava (upper limbs, head, and neck)

• Inferior vena cava (trunk and lower limbs)

Figure 17.14 1

An overview of the systemic arterial system

VertebralCommon carotid

Subclavian

Brachiocephalictrunk

Axillary

Ascendingaorta

Brachial

Radial

Ulnar

Digitalarteries

Palmararches

Popliteal

Fibular

Dorsalis pedis

Plantar arch

Deepfemoral

Femoral

Posterior tibial

Anterior tibial

Aortic arch

Descending aorta

Diaphragm

Celiac trunk

Renal

Gonadal

Lumbar

Common iliac

Internal iliac

External iliac

Figure 17.14 2

Vertebral

An overview of the systemic venous system

External jugular

Internal jugular

Subclavian

Brachiocephalic

Axillary

Brachial

Cephalic

Basilic

Radial

Medianantebrachial

Ulnar

Palmarvenousarches

Digitalveins

Great saphenous

Popliteal

Small saphenous

Fibular

Plantar venous arch

Dorsal venous arch

Femoral

Posterior tibial

Anterior tibial

KEYSuperficial veinsDeep veins

Deepfemoral

Superior vena cava

Diaphragm

Inferior vena cava

Renal

Gonadal

Lumbar

Common iliac

InternaliliacExternaliliac

Module 17.14: Systemic vessels• Systemic vessels

• Arteries and veins are usually similar on both sides of body

• One significant difference between arteries and veins is distribution in the neck and limbs

• Arteries: deep in skin, protected by bones and soft tissues

• Veins: generally two sets, one deep and one superficial• Important in controlling body temperature

• Venous blood flows superficially in hot weather to radiate heat

• Venous blood flows deep in cold weather to conserve heat

Module 17.14 Review

a. Name the two large veins that collect blood from the systemic circuit.

b. Identify the largest artery in the body.

c. Besides containing valves, cite another major difference between the arterial and venous systems.

Module 17.15: Upper limb vessels• Upper limb vessels

• Arteries• Branches of aortic arch

• Brachiocephalic trunk

• Right subclavian (right arm)

• Right common carotid artery (right side head & neck)

• Left common carotid artery (left side head & neck)

• Left subclavian artery (left arm)

Module 17.15: Upper limb vessels• Arteries

(continued)• Right subclavian

artery branches• Internal thoracic

artery (pericardium, anterior chest wall)

• Vertebral artery (brain, spinal cord)

• Arteries of the arm• Axillary artery

(through axilla)• Brachial artery

(upper limb)

Module 17.15: Upper limb vessels• Arteries (continued)

• Arteries of the forearm• Radial artery (follows radius)• Ulnar artery (follows ulna)• Palmar arches (hand)• Digital arteries (thumb and fingers)

Figure 17.15

The branches of the aortic arch and thearteries they give rise to

Branches of the Aortic Arch

The Right Subclavian Artery

Arteries of the Arm

Arteries of the Forearm

Major branches of thesubclavian artery

Digital arteries

Superficial palmar arch

Deep palmar arch

Radial

Ulnar

Descendingaorta

Ascendingaorta

Aortic arch

Heart

Ulnarcollateral

arteries

Brachial

Deepbrachial

Axillary

Internalthoracic

Vertebral

Brachiocephalictrunk

Left common carotid artery

Left subclavianartery

Start

Figure 17.15

Start

The veins that drain into the superior vena cava

The Right Subclavian Vein

Veins of the Neck

Veins of the Arm

Veins of the Forearm

Axillary vein

Cephalic vein

Median cubital vein

Median antebrachial vein

Digital veins

Superficialpalmar arch

Deep palmar arch

Ulnar

Basilic

Radial

Cephalic

Brachial

Basilic

Deep veins

Superficial veins

KEY

Superior vena cava

Superior vena cava

Brachiocephalic vein

Externaljugular vein

Internaljugular vein Vertebral vein

Module 17.15: Upper limb vessels• Veins

• Digital veins (empty from thumb and fingers)• Veins of the forearm

• Superficial palmar arch (hand)• Median antebrachial vein (anterior forearm)• Cephalic vein• Basilic vein• Median cubital vein (interconnects cephalic and

basilic veins)• Venous samples usually collected here

Module 17.15: Upper limb vessels• Veins (continued)

• Veins of the arm• Cephalic vein (lateral side of arm)• Basilic vein (median side of arm)• Brachial vein (median area of arm)

• Right subclavian vein• Merging of axillary vein and cephalic vein

Module 17.15: Upper limb vessels• Veins (continued)

• Veins of the neck• External jugular vein (drains superficial head & neck)• Internal jugular vein (drains deep head & neck)• Vertebral vein (cervical spinal cord and posterior skull)

• Veins draining into superior vena cava (SVC)• Internal thoracic vein (intercostal veins)• Brachiocephalic vein (jugular, axillary, vertebral, and

internal thoracic veins)

Module 17.15 Reviewa. Name the two arteries formed by the division of the

brachiocephalic trunk.

b. A blockage of which branch from the aortic arch would interfere with blood flow to the left arm?

c. Whenever Thor gets angry, a large vein bulges in the lateral region of his neck. Which vein is this?

Module 17.16: Head and neck vessels• Head and neck vessels

• Arteries• Common carotid artery (head and neck)

• Palpated alongside trachea (windpipe)• Contains carotid sinus (with baroreceptors monitoring blood

pressure)• Branches of common carotid artery

• External carotid artery (neck, esophagus, pharynx, larynx, lower jaw, cranium, and face on that side)

• Internal carotid artery (brain and eyes)• Vertebral artery (enters cranium and fuses with basilar

artery along ventral medulla oblongata)

Figure 17.16 1

Areas supplies by the external carotid, internal carotid, and vertebral arteries

Common carotid artery

Carotid sinus

Externalcarotid

Lingual

Facial

Occipital

Maxillary

Superficialtemporal

Branches of theExternal Carotid

Brachiocephalic trunkSubclavianAxillary

Vertebral artery

Internal carotidartery

Basilar

Carotid canal

ClavicleFirst rib

Module 17.16: Head and neck vessels• Veins

• External jugular vein (cranium, face, lower jaw, and neck on that side)

• Internal jugular vein (various cranial venous sinuses)

• Vertebral vein (cervical spinal cord and posterior skull)

Figure 17.16 2

Areas drained by the external and internal jugular veins

Dural sinusesdraining the brain

Jugular foramen

Vertebral vein

Axillary Rightsubclavian

Superiorvena cava

Left brachiocephalic

Right brachiocephalic

Internal jugular vein

External jugular

Occipital

Facial

Maxillary

Temporal

Branches of theExternal Jugular

Clavicle

Module 17.16 Reviewa. Name the arterial structure that contains

baroreceptors.

b. Identify branches of the external carotid artery.

c. Identify the veins that combine to form the brachiocephalic vein.

Module 17.18: Vessels of the trunk

• Vessels of the trunk• Arteries

• Somatic branches of thoracic aorta• Intercostal arteries (chest muscles and vertebral column)• Superior phrenic artery (superior diaphragm)

• Visceral branches of thoracic aorta• Bronchial arteries (lung tissues not involved in gas exchange)• Esophageal arteries (esophagus)• Mediastinal arteries (tissues of mediastinum)• Pericardial arteries (pericardium)

Module 17.18: Vessels of the trunk• Arteries (continued)

• Major paired abdominal aorta branches• Inferior phrenic arteries (inferior diaphragm and

esophagus)• Adrenal arteries (adrenal glands)• Renal arteries (kidneys)• Gonadal arteries (gonads)• Lumbar arteries (vertebrae, spinal cord, abdominal

wall)

Module 17.18: Vessels of the trunk

• Arteries (continued)• Major unpaired branches of abdominal aorta

• Celiac trunk (three branches)1. Left gastric artery (stomach and inferior esophagus)2. Splenic artery (spleen and stomach arteries)3. Common hepatic artery (arteries to liver, stomach, gallbladder,

and proximal small intestine)

• Superior mesenteric artery (pancreas, duodenum, most of large intestine)

• Inferior mesenteric artery (colon and rectum)

Figure 17.18 1

The branches of the thoracic aorta and the abdominal aorta

Somatic Branches ofthe Thoracic Aorta

Visceral Branches ofthe Thoracic Aorta

Aortic arch

Internal thoracic

Thoracic aorta

Intercostal arteries

Superior phrenic artery

Diaphragm

Inferior phrenic

Adrenal

Renal

Gonadal

Lumbar

Common iliac

Inferior mesenteric

Abdomial aorta

Superior mesenteric

Commonhepatic

SplenicLeft gastric

Celiac trunk

Branches ofthe celiactrunk

Pericardial artery

Mediastinal artery

Esophageal arteries

Bronchial arteries

Module 17.18: Vessels of the trunk• Veins

• Azygos and hemiazygos veins (most of thorax)1. Intercostal veins (chest muscles)2. Esophageal veins (inferior esophagus)3. Bronchial veins (passageways of lungs)4. Mediastinal veins (mediastinal structures)

Module 17.18: Vessels of the trunk• Veins (continued)

• Major tributaries of inferior vena cava• Lumbar veins (lumbar portion of abdomen)• Gonadal veins (gonads)• Hepatic veins (liver)• Renal veins (kidneys)• Adrenal veins (adrenal glands)• Phrenic veins (diaphragm)

Figure 17.18 2

The Azygos andHemiazygos Veins

The major tributaries of the superior and inferior venae cavae

Superior vena cava

Internal thoracic

Inferior vena cava

Hepatics

Phrenic

Adrenal

Renal

Gonadal

Lumbar

Common iliac

Esophageal, bronchial,and mediastinal veins

Intercostal veins

Tributaries:

Hemiazygos vein

Azygos vein

Brachiocephalic

Major Tributaries of the Inferior Vena Cava

• Lumbar veins drain the lumbar portion of the abdomen, including the spinal cord and muscles of the body wall.• Gonadal (ovarian or testicular) veins drain the ovaries of testes. The right gonadal vein empties into the inferior vena cava; the left gonadal vein generally drains into the left renal vein.• Hepatic veins drain the sinusoids of the liver.

• Renal veins, the largest tributaries of the inferior vena cava, collect blood from the kidneys.

• Adrenal veins drain the adrenal glands. In most individuals, only the right adrenal vein drains into the inferior vena cava; the left adrenal vein drains into the left renal vein.• Phrenic veins drain the diaphragm. Only the right phrenic vein drains into the inferior vena cava; the left drains into the left renal vein.

Module 17.18 Review

a. Which vessel collects most of the venous blood inferior to the diaphragm?

b. Identify the major tributaries of the inferior vena cava.

c. Grace is in an automobile accident, and her celiac trunk is ruptured. Which organs will be affected most directly by this injury?

Module 17.19: Vessels of the viscera• Vessels of the viscera

• Arteries• Branches of common hepatic artery

• Hepatic artery proper (liver)• Cystic (gallbladder)• Gastroduodenal (stomach and duodenum)• Right gastric (stomach)• Right gastroepiploic (stomach and duodenum)• Superior pancreaticoduodenal (duodenum)

Module 17.19: Vessels of the viscera• Arteries (continued)

• Superior mesenteric artery• Inferior pancreaticoduodenal (pancreas and duodenum)• Right colic (large intestine)• Ileocolic (large intestine)• Middle colic (large intestine)• Intestinal arteries (small intestine)

Module 17.19: Vessels of the viscera• Arteries (continued)

• Inferior mesenteric artery• Left colic (colon)• Sigmoid (colon)• Rectal (colon)

• Branches of the splenic artery• Left gastroepiploic (stomach)• Pancreatic (pancreas)

Figure 17.19 1

The locations of the celiac trunk, the superior and inferior mesenteric arteries, and their branches

The Celiac Trunk

Branches of theCommon Hepatic Artery

Hepatic artery proper (liver)

Cystic (gallbladder)

Gastroduodenal (stomachand duodenum)

Right gastric (stomach)

Right gastroepiploic(stomach and duodenum)

Superior pancreatico-duodenal (duodenum)

Ascending colon

Superior MesentericArtery

Inferiorpancreaticoduodenal(pancreas andduodenum)

Right colic (largeintestine)

Ileocolic (largeintestine)

Middle colic (cut)(large intestine)

Intestinal arteries (smallintestine)

Rectal (rectum)

Sigmoid (colon)

Left colic (colon)

Spleen

Pancreatic (pancreas)

Left gastroepiploic(stomach)

Inferior MesentericArtery

Branches of theSplenic Artery

Rectum

Sigmoid colon

Small intestine

Panceas

Stomach

Liver

Common hepatic artery Left gastric artery Splenic artery

The celiac trunk

Module 17.19: Vessels of the viscera• Veins

• Hepatic portal vein tributaries• Superior mesenteric vein and tributaries

• Pancreaticoduodenal• Middle colic (transverse colon)• Right colic (ascending colon)• Ileocolic (Ileum and ascending colon)• Intestinal (small intestine)

Module 17.19: Vessels of the viscera• Veins (continued)

• Hepatic portal vein tributaries (continued)• Splenic vein and tributaries

• Left gastroepiploic (stomach)• Right gastroepiploic (stomach)• Pancreatic

• Inferior mesenteric vein and tributaries• Left colic (descending colon)• Sigmoid (sigmoid colon)• Superior rectal (rectum)

Figure 17.19 2

Superior MesentericVein and Its Tributaries

The veins (and their tributaries) that form the hepatic portal vein

Inferior vena cava

Hepatic

Cystic

Hepatic portal

Pancreaticoduodenal

Middle colic (fromtransverse colon)

Right colic (ascendingcolon)

Ileocolic (ileum andascending colon)

Intestinal (small intestine)

Left gastric

Right gastric

Right gastroepiploic(stomach)

Left gastroepiploic(stomach)

Pancreatic

Left colic (descendingcolon)

Sigmoid(sigmoid colon)

Superior rectal (rectum)

Descending colonPancreas

Spleen

StomachLiver

Inferior MesentericVein and Its Tributaries

Splenic Vein and ItsTributaries

Tributaries of the Hepatic Portal Vein

• The inferior mesenteric vein collects blood from capillaries along the inferior portion of the large intestine. It drains the left colic vein and the superior rectal veins, which collect venous blood from the descending colon, sigmoid colon, and rectum.

• The splenic vein is formed by the union of the inferior mesenteric vein and veins from the spleen, the lateral border of the stomach (left gastroepiploic vein), and the pancreas (pancreatic veins).

• The superior mesenteric vein collects blood from veins draining the stomach (right gastroepiploic vein), the small intestine (intestinal and pancreaticoduodenal veins), and two-thirds of the large intestine (ileocolic, right colic, and middle colic veins).

Module 17.19 Reviewa. List the unpaired branches of the abdominal aorta

that supply blood to the visceral organs.

b. Identify the three veins that merge to form the hepatic portal vein.

c. Identify two veins that carry blood away from the stomach.

Module 17.20: Lower limb vessels• Lower limb vessels

• Arteries• Common iliac artery

• Internal iliac artery (bladder, pelvic walls, external genitalia, medial side of thigh, in females, uterus and vagina)

• Lateral sacral artery• Internal pudendal artery• Obturator artery• Superior gluteal artery

Module 17.20: Lower limb vessels• Arteries (continued)

• Common iliac artery (continued)• External iliac artery

• Femoral artery• Deep femoral artery• Femoral circumflex arteries (ventral and lateral skin and deep

muscles of thigh)• Popliteal artery (posterior knee)• Posterior and anterior tibial arteries (leg)• Fibular artery (lateral leg)

Module 17.20: Lower limb vessels• Arteries (continued)

• Arteries of the foot• Dorsalis pedis• Dorsal arch• Plantar arch• Medial plantar• Lateral plantar

Figure 17.20 1

The arteries that supply the pelvis and lower limb

Anterior View Posterior ViewInternal Iliac and Its Branches

Arteries of the Foot

Dorsalis pedis

Medial plantar

Lateral plantar

Dorsal arch

Plantar arch

Fibular

Anterior tibial

Posterior tibial

Popliteal

Femoral circumflex

Deep femoral

Femoral

External iliac

Common iliacInternal iliac

Lateral sacral

Internal pudendal

Obturator

Superior gluteal

Femoral

Descending genicular artery

Fibular (peroneal)

Posterior tibial

Anterior tibial

Popliteal

Femoral circumflex

Deep femoral

Right externaliliac

Module 17.20: Lower limb vessels• Veins

• External iliac veins (lower limbs, pelvis, and lower abdomen)

• Internal iliac veins (pelvic organs)• External and internal iliac fuse to form common iliac

veins

Figure 17.20 2

Deep femoral

Popliteal

Anterior tibial

Posterior tibial

Fibular

Dorsal venous arch

Digital

Plantar venousarch

Small saphenous

Great saphenous

Femoral

Femoral circumflex

Femoral

Obturator

Lateral sacral

Internal pudendal

Internal iliac

Common iliac

External iliac

Gluteal

Posterior ViewAnterior View

The veins that drain the pelvis and lower limb

Femoral

Convergence of the greatsaphenous, the deepfemoral, and the femoralcircumflex veins

Module 17.20 Review

a. Name the first two divisions of the common iliac artery.

b. The plantar venous arch carries blood to which three veins?

c. A blood clot that blocks the popliteal vein would interfere with blood flow in which other veins?

CLINICAL MODULE 17.21: Fetal circulation and defects• Unique fetal circulation structures

• Umbilical arteries (internal iliac arteries to placenta)• Umbilical vein (placenta to ductus venosus)• Ductus venosus (drains liver and umbilical vein into

inferior vena cava)• Ductus arteriosus (pulmonary trunk to aorta)

• Sends blood from right ventricle to systemic circuit• Foramen ovale (right to left atrium)

• Has one-way valve to prevent backflow

Figure 17.21 1

The path of blood flow in a full-term fetus before birth

Foramen ovale

Ductus arteriosus

Pulmonarytrunk

Inferior vena cava

Ductus venosus

Umbilical arteries

Umbilical vein

Umbilicalcord

Placenta

Aorta

Liver

CLINICAL MODULE 17.21: Fetal circulation and defects• At birth, fetal circulation changes due to activated

pulmonary circulation• Resulting pressure closes foramen ovale

• Fossa ovalis (shallow depression, adult remnant)

• Rising oxygen levels cause ductus arteriosus to constrict and close

• Ligamentum arteriosum (fibrous adult remnant)

Figure 17.21 2

The flow of blood through the heart upon the closingof the ductus arteriosus and foramen ovale at birth

Ductus arteriosus(closed)

Pulmonary trunk

Left atrium

Foramen ovale(closed)

Right atrium

Left ventricle

Right ventricleInferior

vena cava

CLINICAL MODULE 17.21: Fetal circulation and defects

• Congenital cardiac defects• Ventricular septal defects

• Openings in interventricular septum• Patent foramen ovale

• Passageway remains open• Left ventricle must work harder to provide adequate systemic

flow• Patent ductus arteriosus

• Passageway remains open• Blood is not adequately oxygenated and skin bluish

CLINICAL MODULE 17.21 Reviewa. Describe the pattern of fetal blood flow to and from the

placenta.

b. Identify the six structures that are necessary in the fetal circulation but cease to function at birth, and describe what becomes of these structures.

Module 18.4: Coronary circulation• Coronary circulation

• Provides cardiac muscle cells with reliable supplies of oxygen and nutrients

• During maximum exertion, myocardial blood flow may increase to 9× resting levels

• Blood flow is continuous but not steady

• With left ventricular relaxation, aorta walls recoil (elastic rebound), which pushes blood into coronary arteries

Module 18.4: Coronary circulation• Coronary arteries

• Right coronary artery (right atrium, portions of both ventricles and conduction system of heart)

• Marginal arteries (right ventricle surface)• Posterior interventricular artery (interventricular

septum and adjacent ventricular portions)

• Left coronary artery (left ventricle, left atrium, and interventricular septum)

• Circumflex artery (from left coronary artery, follows coronary sulcus to meet right coronary artery branches)

• Anterior interventricular artery (interventricular sulcus)

Figure 18.4 1 – 2

The locations of the arterial supply to the heart

An anterior view of the coronary arteries

Right Coronary Artery

Right coronary artery in the coronary sulcus

Marginal arteries

The branches of the coronary arterieson the posterior surface of the heart

Marginalartery

Right coronary artery

Rightatrium

Rightventricle

Leftatrium

Leftventricle

Rightatrium

Rightventricle

Leftatrium

Leftventricle

Posteriorinterventricularartery

Anteriorinterventricularartery

Left coronary artery

Circumflex artery

Arterial anastomosesbetween the anteriorand posteriorinterventricular arteries

Left Coronary Artery

Aorticarch

Pulmonarytrunk

Circumflex artery

Posterior view

Anterior view

Module 18.4: Coronary circulation

• Coronary veins• Great cardiac vein (drains area supplied by

anterior interventricular artery, empties into coronary sinus on posterior)

• Anterior cardiac veins (drains anterior surface of right ventricle, empties into right atrium)

Figure 18.4 3

Leftatrium

Leftventricle

Rightatrium

Rightventricle

Aorticarch

Anterior view

Greatcardiac vein

Anterior cardiac veins

The major collecting vessels on the anteriorsurface of the heart

Module 18.4: Coronary circulation• Coronary veins (continued)

• Coronary sinus (expanded vein, empties into right atrium)

• Posterior cardiac vein (drains area supplied by circumflex artery)

• Small cardiac vein (drains posterior right atrium and ventricle, empties into coronary sinus)

• Middle cardiac vein (drains area supplied by posterior interventricular artery, drains into coronary sinus)

Figure 18.4 4

Leftventricle

Rightventricle

Rightatrium

Leftatrium

Posterior view

Posteriorcardiac vein

Greatcardiac vein

Middlecardiac vein

Smallcardiac vein

Coronary sinus

The major collecting vessels onthe posterior surface of the heart

Module 18.4 Review

a. List the arteries and veins of the heart.

b. Describe what happens to blood flow during elastic rebound.

c. Identify the main vessel that drains blood from the myocardial capillaries.

Module 18.5: Internal heart anatomy• Internal heart anatomy

• Four chambers• Two atria (left and right separated by interatrial

septum)• Two ventricles (left and right separated by

interventricular septum)• Left atrium flows into left ventricle• Right atrium flows into right ventricle

Module 18.5: Internal heart anatomy

• Right atrium• Receives blood from superior and inferior venae

cavae and coronary sinus• Fossa ovalis (remnant of fetal foramen ovale)• Pectinate (pectin, comb) muscles (muscular ridges

on anterior atrial and auricle walls)• Left atrium

• Receives blood from pulmonary veins

Module 18.5: Internal heart anatomy• Right ventricle

• Receives blood from right atrium through right atrioventricular (AV) valve

• Also known as tricuspid (tri, three)• Has three flaps or cusps attached to tendinous connective

fibers• Fibers connect to papillary muscles

• Innervated to contract through moderator band which keeps “slamming” of AV cusps

• Prevents backflow of blood to atrium during ventricular contraction

Module 18.5: Internal heart anatomy• Left ventricle

• Receives blood from left atrium through right atrioventricular valve

• Also known as bicuspid and mitral (mitre, bishop’s hat) valve

• Prevents backflow of blood to atrium during ventricular contraction

• Has paired flaps or cusps• Trabeculae carneae (carneus, fleshy)

• Muscular ridges on ventricular walls• Aortic valve

• Allows blood to exit left ventricle and enter aorta

Figure 18.5 1

The internal anatomy of the heart andthe direction of blood flow betweenthe chambers

Inferiorvena cava

Left AtriumRight Atrium

Left Ventricle

Aortic arch

Pulmonarytrunk

Superiorvena cava

Aortic valve

Ascendingaorta

Moderatorband

Interventricularseptum

Fossa ovalis

Pectinate muscles on the innersurface of the auricle

Opening of the coronary sinus

Receives blood from the superiorand inferior venae cavae and fromthe cardiac veins through thecoronary sinus

Right Ventricle

Left pulmonary veins

Receives blood fromthe pulmonary veins

Thick wall of left ventricle

Left atrioventricular (AV)valve (bicuspid valve)

Trabeculae carneae

Chordae tendineae

Right atrioventricular (AV)valve (tricuspid valve)

Papillary muscle

Pulmonary valve (pulmonarysemilunar valve)

Module 18.5: Internal heart anatomy

• Ventricular comparisons• Right ventricle has relatively thin wall

• Ventricle only pushes blood to nearby pulmonary circuit

• When it contracts, it squeezes against left ventricle wall forcing blood out pulmonary trunk

• Left ventricle has extremely thick wall and is round in cross section

• Ventricle must develop 4–6× as much pressure as right to push blood around systemic circuit

• When it contracts1. Diameter of chamber decreases2. Distance between base and apex decreases

Figure 18.5 2

A sectional view of the heart showingthe thicknesses of the ventricle wallsand the shapes of the ventricularchambers

The relatively thin wallof the right ventricleresembles a pouchattached to the massivewall of the left ventricle

The left ventricle hasan extremely thickmuscular wall and isround in cross section.

Fat in anteriorinterventricular sulcus

Posteriorinterventricular sulcus

Figure 18.5 3

Leftventricle

Rightventricle

The changes in ventricleshape during ventricularcontraction

Dilated (relaxed)

Contracted

Contraction of rightventricle squeezesblood against the thickwall of the left ventricle.

Contraction of left ventricledecreases the diameter of theventricular chamber and reducesthe distance between the baseand apex

Module 18.5 Review

a. Damage to the semilunar valves on the right side of the heart would affect blood flow to which vessel?

b. What prevents the AV valves from swinging into the atria?

c. Why is the left ventricle more muscular than the right ventricle?

Module 18.6: Heart valves

• Semilunar (half-moon shaped) valves• Aortic and pulmonary semilunar valves

• Allow blood to exit ventricles and enter aorta or pulmonary trunk

• Do not require muscular braces because cusps are stable• All three symmetrical cusps support each other

Module 18.6: Heart valves

• Valve action during atrial contraction and ventricular relaxation• AV valves

• Open• Blood pressure from contracting atria pushes cusps apart• Chordae tendineae are loose, offering no resistance

• Semilunar valves (aortic and pulmonary)• Closed

• Little pressure from ventricles• Blood pressure from aorta and pulmonary arteries keep closed

Figure 18.6 1

The positions of the valves and associatedstructures when the ventricles are relaxed

Rightventricle

Leftatrium

Right AV (tricuspid)valve (open)

Aortic valve (closed)

Pulmonary valve (closed)

Aortic valve (closed)

Pulmonaryveins

Left AV (bicuspid)valve (open)

Left ventricle(dilated)

Superior viewof cardiac valves

Chordae tendineae(loose)

Papillary muscles(relaxed)

KEY

Oxygenatedblood

Deoxygenatedblood

Module 18.6: Heart valves

• Valve action during atrial relaxation and ventricular contraction• AV valves

• Closed• Blood pressure from contracting ventricles pushes cusps

together• Papillary muscles tensing prevent cusps from swinging into

atria (would allow backflow or regurgitation)

• Semilunar valves (aortic and pulmonary)• Open

• High blood pressure from ventricles overcome blood pressures from aorta and pulmonary arteries

Animation: The Heart: Valves

Figure 18.6 2

The positions of the valves and associatedstructures when the ventricles contract

Leftatrium

Aorta

Aortic sinus

Aortic valve (open)

Aortic valve (open)

Pulmonary valve (open)

Right AV (tricuspid)valve (closed)

Left AV (bicuspid)valve (closed)

Left ventricle(contracted)

Ventricular contraction

Frontal section throughleft atrium and ventricle

Papillary muscles(contracted)

Chordae tendineae(tense)

Superior viewof cardiac valves

KEY

Oxygenatedblood

Deoxygenatedblood

Module 18.6: Heart valves

• Cardiac skeleton• Flexible connective tissues in which all valves are

encircled and supported • Also surrounds aorta and pulmonary trunk

• Separates atrial and ventricular myocardium• Contains dense bands of tough elastic tissue

Figure 18.6 3

A superior view of the heartshowing the cardiac skeleton

Cardiacskeleton

Module 18.6 Review

a. Define cardiac regurgitation.

b. Compare the structure of the tricuspid valve with that of the pulmonary valve.

c. What do semilunar valves prevent?

Section 2: The Cardiac Cycle

• Cardiac cycle• Period from one heartbeat to the beginning of next

• Alternating periods of contraction (systole) and relaxation (diastole)

• Atria contract as a pair first• As ventricles are relaxed and filling

• Ventricles contract as a pair next• As atria are relaxed and filling

• Cardiac pacemaker system coordinates• Typical cardiac cycle lasts 800 msec

ContractionRelaxation

A cardiac cycle: a heartbeat (contraction)followed by a brief period of relaxation

Figure 18 Section 2 1

RelaxationAtria contract Ventricles contractRelaxation

The sequence of events during a single heartbeat

Figure 18 Section 2 2

Start0

msec100

msec

800msec

370msec

dia

sto

le

systole

syst

ole

Atrial

Cardiaccycle

The two phases of the cardiac cycle for agiven chamber in the heart: systole(contraction) and diastole (relaxation)

Atrial

Ven

tric

ula

r

diastole

Ven

tric

ula

r

Figure 18 Section 2 3

Module 18.8: Cardiac cycle phases

• Steps of cardiac cycle (for 75 bpm heart rate)1. When cycle begins, all four chambers are relaxed2. Atrial systole (100 msec)

• Contracting atria fill relaxed ventricles with blood3. Atrial diastole (270 msec)

• Concurrent with ventricular systole (2 phases)4. Ventricular systole – first phase

• Contracting ventricles push AV valves open but not enough pressure to open semilunar valves

• = Isovolumetric contraction

Module 18.8: Cardiac cycle phases• Steps of cardiac cycle (continued)

5. Ventricular systole – second phase• As ventricular pressure rises, semilunar valves open

and blood leaves ventricle (= ventricular ejection)6. Ventricular diastole – early

• Ventricles relax and blood pressure in them drops allowing closure of semilunar valves

• Isovolumetric relaxation occurs with AV valves still closed

7. Ventricular diastole – late• All chambers relaxed• Ventricles fill passively to roughly 70%

Animation: The Heart: Cardiac Cycle

Figure 18.8 1

The phases of the cardiac cycle for a heart rate of 75 beats per minute

Start

Ventricular diastole lasts 530msec (the 430 msec remaining inthis cardiac cycle, plus the first100 msec of the next). Throughoutthe rest of this cardiac cycle,filling occurs passively, and boththe atria and the ventricles arerelaxed. The next cardiac cyclebegins with atrial systole and thecompletion of ventricular filling.

When the cardiac cyclebegins, all four chambersare relaxed, and theventricles are partiallyfilled with blood.

During atrial systole, theatria contract, completelyfilling the relaxedventricles with blood.Atrial systole lasts100 msec.

Atrial systoleends and atrialdiastole beginsand continues untilthe start of the nextcardiac cycle.

As atrial systole ends,ventricular systole begins.This period, which lasts270 msec, can be dividedinto two phases.

Ventricular systole—first phase: Ventricularcontraction pushes theAV valves closed butdoes not create enoughpressure to open thesemilunar valves. This isknown as the period ofisovolumetriccontraction.

Ventricular systole—second phase: Asventricular pressure risesand exceeds pressure inthe arteries, the semilunarvalves open and bloodis forced out of theventricle. This isknown as the periodof ventricularejection.

Ventricular diastole—early: As the ventriclesrelax, the pressure in themdrops; blood flows backagainst the cusps of thesemilunar valves and forcesthem closed.

Blood flows into therelaxed atria but theAV valves remainclosed. This is knownas the period ofisovolumetricrelaxation.

Ventricular diastole—late: All chambers arerelaxed. The ventriclesfill passively to roughly70% of their finalvolume.

800msec

0msec 100

msec

370msec

Atrial

Cardiaccycle

systole

dia

sto

le

syst

ole

diastole

Ven

tric

ula

r

Atrial

Ven

tric

ula

r

Figure 18.8 2

Time (msec)

0

0 100 200 300 400 500 600 700 800

30

60

90

120

Left AVvalve closes.

Aortic valveopens.

Aortic valve closes.

Left AV valve opens.

Dicrotic notch

Pre

ssu

re (

mm

Hg

)

The correspondence of the heart sounds with events during the cardiac cycle

Heart sounds

S4

S1 S2S3

S4

“Dubb”“Lubb”

KEY

Atrial contraction begins.

Atria eject blood into ventricles.

Atrial systole ends; AV valves close.

Isovolumetric contraction.

Ventricular ejection occurs.

Semilunar valves close.

Isovolumetric relaxation occurs.

AV valves open; passive ventricularfilling occurs.

Leftventricle

Left atrium

The pressure changes within the aorta, left atrium, and left ventricle during the cardiac cycle

ATRIALDIASTOLE

ATRIALSYSTOLE

ATRIAL DIASTOLE

VENTRICULARDIASTOLE

VENTRICULARSYSTOLE VENTRICULAR DIASTOLE

ATRIALSYSTOLE

Aorta

Module 18.8: Cardiac cycle phases• Heart sounds

• S1 (known as “lubb”)• Start of ventricular contraction and closure of AV valves

• S2 (known as “dupp”)• Closure of semilunar valves

• S3 and S4

• Very faint and rarely heard in adults• S3 (blood flowing into ventricles)• S4 (atrial contraction)

Module 18.8 Review

a. Provide the alternate terms for heart contraction and heart relaxation.

b. List the phases of the cardiac cycle.

c. Is the heart always pumping blood when pressure in the left ventricle is rising? Explain.

Module 18.9: Cardiac output and conduction system• Conduction system

• Network of specialized cardiac muscle cells• Responsible for initiating and distributing stimulus to

contract• Can do so on their own (= automaticity)

• Components1. Sinoatrial (SA) node

• Embedded in posterior wall of right atrium• Impulse generated by this pacemaker is distributed

through other components2. Internodal pathways

• Distribute signal to atria on way to ventricles

Module 18.9: Cardiac output and conduction system• Conduction system (continued)

3. Atrioventricular (AV) node• Located at junction of atria and ventricles• Also contains pacemaker cells• If SA node damaged, can maintain heart rate at 40–60

bpm• Can conduct impulses at maximum rate of 230/min

• = Maximum heart rate

4. AV bundle and branches• Located in interventricular septum• Normally only electrical connection between atria and

ventricles• Branches relay signal to ventricles toward heart apex

Module 18.9: Cardiac output and conduction system

• Conduction system (continued)5. Purkinje fibers

• Large-diameter conducting cells• As fast as small myelinated axons

• Final part of conduction system that triggers ventricular systole

Animation: The Heart: Conduction System

Figure 18.9 3

The components of the conducting system and their specific functions

Moderatorband

Purkinje fibers are large-diameterconducting cells that propagate actionpotentials very rapidly—as fast as smallmyelinated axons. Purkinje cells are thefinal link in the distribution network, andthey are responsible for the depolarizationof the ventricular myocardial cells thattriggers ventricular systole.

The AV node delivers the stimulusto the AV bundle, located within theinterventricular septum. The AV bundle isnormally the only electrical connectionbetween the atria and the ventricles.

The AV bundle leads to the right and leftbundle branches. The left bundlebranch, which supplies the massive leftventricle, is much larger than the rightbundle branch. Both branches extendtoward the apex of the heart, turn, andfan out deep to the endocardial surface.

The atrioventricular (AV) node is located at the junctionbetween the atria and ventricles. The AV node also containspacemaker cells, but they do not ordinarily affect the heartrate. However, if the SA node or internodal pathways aredamaged, the heart will continue to beat because in theabsence of commands from the SA node, the AV node willgenerate impulses at a rate of 40–60 beats per minute.

In the atria, conducting cells arefound in internodal pathways,which distribute the contractilestimulus to atrial muscle cells as theimpulse travels toward the ventricles.

Each heartbeat begins with an actionpotential generated at the sinoatrial(sī-nō-Ā-trē-al) node, or simply theSA node. The SA node is embeddedin the posterior wall of the rightatrium, near the entrance of thesuperior vena cava. The electricalimpulse generated by this cardiacpacemaker is then distributed byother cells of the conducting system.

Figure 18.9 4

Moderatorband

Purkinje fibers Elapsed time = 225 msec

Elapsed time = 175 msec

Elapsed time = 150 msec

Elapsed time = 50 msec

Time = 0

SA node

AV node

AVbundle

Bundlebranches

An action potential isgenerated at the SAnode, and atrialactivation begins.

The stimulus spreadsacross the atrialsurfaces by cell-to-cellcontact within theinternodal pathwaysand soon reaches theAV node.

A 100-msec delayoccurs at the AVnode. During thisdelay, atrialcontraction begins.

As atrial contractioncontinues, the impulsetravels along theinterventricular septumwithin the AV bundle andthe bundle branches tothe Purkinje fibers and, viathe moderator band, tothe papillary muscles ofthe right ventricle.

The impulse is distributedby Purkinje fibers andrelayed throughout theventricular myocardium.Atrial contraction iscompleted, andventricular contractionbegins.

The distribution of thecontractile stimulus, andhow the conducting systemcoordinates the contractionsof the cardiac cycle

Module 18.9 Review

a. Define automaticity.

b. If the cells of the SA node failed to function, how would the heart rate be affected?

c. Why is it important for impulses from the atria to be delayed at the AV node before they pass into the ventricles?

Module 18.11: Autonomic control of heart function

• Autonomic control of heart function• Pacemaker cells in the SA and AV nodes cannot

maintain a stable resting potential• Always gradual depolarization leading to threshold (=

prepotential or pacemaker potential)• Fastest rate at SA node (80–100 bpm)

• Brings other conduction system components to threshold

Figure 18.11 1

Heart rate under three conditions: at rest, under parasympatheticstimulation, and under sympathetic stimulation

A prepotential or pacemaker potentialin a heart at rest

+20

0

–30

–60

Threshold

Heart rate: 75 bpm

Membranepotential

(mV)

Normal (resting) Prepotential(spontaneousdepolarization)

Time (sec)2.41.60.8

Module 18.11: Autonomic control of heart function

• Autonomic changes to intrinsic heart rate• Factors that change rate of depolarization and

repolarization will change time to threshold• Leads to change in heart rate

• Bradycardia (heart rate slower than normal, <60 bpm)• Tachycardia (heart rate faster than normal, >100 bpm)

• Parasympathetic stimulation• Binding of ACh from parasympathetic neurons opens K+

channels, slows heart rate• Slows rate of depolarization• Extends duration in repolarization

Module 18.11: Autonomic control of heart function

• Autonomic changes to intrinsic heart rate (continued)

• Sympathetic stimulation• Binding of noepinephrine to beta-1 receptors leads to opening

of ion channels, and increases heart rate• Increases rate of depolarization• Shortens duration in repolarization

Figure 18.11 2

Increased heart rate resulting whenACh released by parasympatheticneurons opens chemically gated K+

channels, thereby slowing the rateof spontaneous depolarization

Threshold

+20

–30

0

–60

Heart rate: 40 bpm

Membranepotential

(mV)

Slower depolarization

Hyperpolarization

Parasympathetic stimulation

Heart rate under three conditions: at rest, under parasympatheticstimulation, and under sympathetic stimulation

A prepotential or pacemaker potentialin a heart at rest

2.41.60.8

Time (sec)

CLINICAL MODULE 18.14: Electrocardiograms (ECG)

• Electrocardiograms record electrical activities of heart from body surface through time

• Can be used to assess performance of:• Nodes• Conduction system• Contractile components

• Appearance varies with placement and number of electrodes or leads

Figure 18.14 1

An electrocardiogram: a standard placement ofleads and the tracing that results

One of the standard configurations for theplacement of leads for an ECG

The features of a typical electrocardiogram

800 msec

T waveP wave QRS complex

Millivolts

P–R interval Q–T interval

+1

+0.5

0

–0.5

P

R

T

Q S

CLINICAL MODULE 18.14: Electrocardiograms (ECG)

• Typical ECG features• P wave (atrial depolarization)

• Atria begin contracting ~25 msec after P wave start

• QRS complex (atrial repolarization and ventricular depolarization)

• Larger wave due to larger ventricles added to atrial activity• Ventricles begin contracting shortly after R wave peak

• T wave (ventricular repolarization)

CLINICAL MODULE 18.14: Electrocardiograms (ECG)

• Typical ECG features (continued)• P-R interval (start of atrial depolarization to start of

ventricular depolarization)• >200 msec may indicate damage to conducting

pathways or AV node

• Q-T interval (time for ventricles to undergo a single cycle)

• Starts at end of P-R interval to end of T wave

Module 18.16: Blood pressure and flow

• Blood flow (F) is directly proportional to blood pressure

• Increased pressure = increased flow

• The pressure gradient (difference from one end of vessel to other) is more important

• Large gradient from aorta to capillaries• Smaller, more numerous vessels produce more

resistance, reducing pressure and flow• At aorta: 2.5 cm diameter and 100 mm Hg pressure• At capillaries: 8 µm diameter and 25 mm Hg pressure

Module 18.16: Blood pressure and flow

• Arterial pressure is variable• Rising during ventricular systole (systolic

pressure)• Declining during ventricular diastole (diastolic

pressure)• Commonly written with a “/” between pressures

• Example: 120/90

• Pulse pressure (difference between systolic and diastolic)• Example: 120 – 90 = 30 mm Hg

• Mean arterial pressure (MAP)• Adding 1/3 of pulse pressure to diastolic pressure• Example: 90 + (120 – 90)/3 = 100 mm Hg

Figure 18.16 4

The calculation of meanarterial pressure

Pulse pressure,the differencebetween systolicand diastolicpressures

Systolic

Diastolic

Mean arterial pressure(MAP), the sum of thediastolic pressure andone-third of the pulsepressure

Here, MAP is

90 + (120 – 90 )/3

90 + 10 = 100 mm Hgor

mm Hg

0

20

40

60

80

100

120

Aorta Elasticarteries

Musculararteries

Arterioles Capillaries Venules Largeveins

Venaecavae

Medium-sized veins

Module 18.16: Blood pressure and flow

• Capillary exchange• Involves:

• Filtration• Capillary hydrostatic pressure (CHP) provides driving

force• Water and small solutes leave capillaries• Larger molecules (like plasma proteins) remain in blood

• Diffusion• Osmosis

Figure 18.16 5

Endothelialcell 1

Endothelialcell 2

Water molecule

Hydrogen bond

Small solutes

Interstitial fluid

Ions

Glucose

Blood protein

Amino acid

Capillaryhydrostatic

pressure(CHP)

The effect of capillaryhydrostatic pressure onwater and small solutes

Module 18.16 Review

a. Define blood flow, and describe its relationship to blood pressure and peripheral resistance.

b. In a healthy individual, where is blood pressure greater: in the aorta or in the inferior vena cava? Explain.

c. For an individual with a blood pressure of 125/70, calculate the mean arterial pressure (MAP).