Circulation and Respiration

Chapter 22

The Circulatory System

• Works with other organ systems• Maintains volume, solute concentration and

temperature of interstitial fluid• Interstitial fluid and blood are body’s internal

environment

Blood Circulation

• Blood flows through blood vessels• Heart generates force to keep

blood moving• Closed system – Blood is confined to vessels and heart

• Open system– Blood mingles with fluid in tissues

aorta

heart

Fig. 22-1a, p.361

Open and Closed Systems

spaces orcavitiesin bodytissues

pump

Fig. 22-1b, p.361

Open and Closed Systems

dorsal blood vessel

two of fivehearts

ventral bloodvessels

gut cavity

Fig. 22-1c, p.361

Open and Closed Systems

large-diameterblood vessels(rapid flow)

large-diameterblood vessels(rapid flow)

small-diameter blood vessels(leisurely flow in diffusion zone)

pump

Fig. 22-1d, p.361

Open and Closed Systems

Blood Flow and Gas Exchange

• Rate of blood flow varies with diameter of blood vessels

• Slowest flow in smallest vessels, the capillaries

• Gases are exchanged between blood and interstitial fluid across capillary walls

Vertebrate Circulatory Systems

• Fish– Two-chambered heart, one circuit

• Amphibians– Three-chambered heart, two partially

separate circuits• Birds and mammals– Four-chambered heart, two entirely separate

circuits

capillary beds of gills

heart

rest of body

a In fishes, a two-chambered heart (atrium, ventricle) pumps blood in one circuit. Blood picks up oxygen in gills, delivers it to rest of body. Oxygen-poor blood flows back to heart.

Fig. 22-2a, p.362

Vertebrate Circulatory Systems

rightatrium

leftatrium

heart

rest of body

lungs

b In amphibians, a heart pumps blood through two partially separate circuits. Blood flows to lungs, picks up oxygen, returns to heart. But it mixes with oxygen-poor blood still in the heart, flows to rest of body, returns to heart.

Fig. 22-2b, p.362

Vertebrate Circulatory Systems

rest of body

lungs

rightatrium

leftatrium

right ventricle left ventricle

c In birds and mammals, the heart is fully partitioned into two halves. Blood circulates in two circuits: from the heart’s right half to lungs and back, then from the heart’s left half to oxygen-requiring tissues and back.

Fig. 22-2c, p.362

Vertebrate Circulatory Systems

Double Circuits

• In birds and mammals• Right half of heart– Pulmonary circuit– Heart to lungs and return

• Left half of heart– Systemic circuit– Heart to body tissues and return

Functions of Blood

• Transports oxygen and nutrients to cells• Carries carbon dioxide and wastes away from

cells• Helps stabilize internal pH• Carries infection-fighting cells• Helps equalize temperature

Components of Blood

• Plasma– Water– Proteins– Dissolved materials

• Cells– Red blood cells– White blood cells– Platelets

Components Relative AmountsPlasma Portion (50%–60% of total volume):

1. Water

3. Ions, sugars, lipids, amino acids, hormones, vitamins, dissolved gases

91%–92% ofplasma volume

7%–8%

1%–2%

Cellular Portion (40%–50% of total volume):

1. Red blood cells

2. White blood cells: Neutrophils Lymphocytes Monocytes (macrophages) Eosinophils Basophils

3. Platelets

4,800,000–5,400,000per microliter

3,000–6,7501,000–2,700

150–720100–360

25–90

250,000–300,000

Fig. 22-3b, p.363

2. Plasma proteins (albumin, globulins, fibrinogen, etc.

Components of Blood

Blood Cell Development

• Stem cells in bone marrow produce blood cells and platelets

• Body continually replaces blood cells

red blood cell

white blood cell

platelets

Fig. 22-3a, p.363

Blood Cell Development

Erythrocytes (Red Cells)

• Most numerous cells in blood• Transport oxygen and carbon dioxide• Colored red by oxygen-binding pigment

(hemoglobin)• Have no nucleus when mature

Leukocytes (White Cells)

• Function in housekeeping and defense• Cell types

Basophils Dendritic cells

Eosinophils B cells

Neutrophils T cells

Macrophages

Platelets

• Membrane-bound cell fragments• Derived from megakaryocytes, which arise

from stem cells• Release substances that initiate

blood clotting

Human Heart Is a Double Pump

• Partition separates heart into left and right sides

• Each pumps blood through a different circuit

Pulmonary Circuit

Heart to lungs

Oxygenates blood

right pulmonary artery left pulmonary artery

capillarybed ofrightlung

pulmonarytrunk

capillary bedof left lung

(to systemic circuit)

pulmonary veins

lungs

(fromsystemiccircuit)

heart

Systemic Circuit

Starts at aorta

Carries oxygenated blood to body tissues

capillary beds of headand upper extremities

(to pulmonarycircuit)

aorta

(frompulmonarycircuit)

heart

capillary beds of otherorgans in thoracic cavity

capillary bed of liver

capillary beds of intestines

capillary beds of other abdominalorgans and lower extremities

jugular veins

superior vena cava

pulmonary veins

hepatic portal vein

renal vein

inferior vena cava

iliac veins

femoral vein

carotid arteries

ascending aorta

pulmonary arteries

coronary arteries

renal artery

brachial artery

abdominal aorta

iliac arteries

femoral artery

Major Vessels

Four Chambers

• Each side has two chambers

–Upper atrium

– Lower ventricle

• Valves between atria and ventricles

Heart Anatomysuperior vena cava

right semilunar valve

right pulmonary veins

right atrium

right AV valve

right ventricle

inferior vena cava

septum myocardium heart’s apex

arch of aorta

trunk of pulmonaryarteriesleft semilunar valve

left pulmonaryveinsleft atrium

left AV valve

left ventricle

endothelium and connective tissue

inner layer ofpericardium

Major Vessels

Cardiac Cycle

Diastole(mid to late).Ventricles fill,atria contract.

Diastole(early). Bothchambersrelax.

Ventricularsystole (atria arestill in diastole).Ventricles eject.

Conduction and Contraction

• SA node in right atrium is pacemaker

• Electrical signals cause contraction of atria

• Signal flows to AV node and down septum to ventricles

SA node

Blood Vessels

• Arteries: carry blood away from heart

• Arterioles: diameter is adjusted to regulate blood flow

• Capillaries: diffusion occurs across thin walls

Blood Pressure• Highest in arteries, lowest in veins• Usually measured in the brachial artery• Systolic pressure is peak pressure – Ventricular contraction

• Diastolic pressure is the lowest pressure– Ventricular relaxation

Measuring Blood Pressure

Resistance

• Adjusted at arterioles• Vasodilation– Increases vessel diameter– Lowers blood pressure

• Vasoconstriction– Decreases vessel diameter– Increases blood pressure

lungs

heart’s right half heart’s left half

liver

digestive tract

kidneys

skeletal muscle

brain

skin

bone

cardiac muscle

all other regions

100%

6%

21%

20%

15%

13%

9%

5%

3%

8%

Fig. 22-10, p.367

Distribution

Capillary Beds

• Diffusion zone; site of exchange between blood and interstitial fluid

• Capillary wall is one cell thick• Flow is slow; allows gases to diffuse across

membranes of blood cells and across endothelium

Bulk Flow in Capillary Bed

blood tovenule

inward-directedosmotic movement

cells oftissue

outward-directedbulk flowblood

from arteriole

Net Bulk Flow

• Normally, ultrafiltration only slightly exceeds reabsorption

• Fluid enters interstitial fluid and returned to blood via the lymphatic system

• High blood pressure causes excessive ultrafiltration and results in edema

The Venous System

• Blood flows from capillaries to venules to veins• Veins are large-diameter vessels with some

smooth muscle in wall

Vein Function

• Valves in veins prevent blood from flowing backward

blood flow to heart

valve open

valveclosed

valve closed

valve closed

venous valve

Fig. 22-13, p.369

Vein Function

Hemostasis

• Processes that stop blood loss and repair vessels– Blood vessel spasm– Platelet plug formation– Blood coagulation– Clotting

Clotting Mechanism

• Prothrombin is converted to thrombin

• Fibrinogen is converted to fibrin• Fibrin forms net that entangles

cells and platelets

Hypertension

• Blood pressure above 140/90• Tends to be genetic• May also be influenced by diet• Contributes to atherosclerosis• “Silent killer”, few outward signs

Atherosclerosis

• Arteries thicken, lose elasticity

• Fill up with cholesterol and lipids

• High LDL increases risk

wall of artery, cross-section

unobstructed lumen of normal artery

Fig. 22-15a, p.370

atherosclerotic plaque

blood clot sticking to plaque

narrowed lumen

Fig. 22-15b, p.370

• Atherosclerosis in arteries of heart• Causes heart attacks

Coronary Artery Disease

coronary artery

aorta

location of a shunt made of a section taken from one of the patient’s other blood vessels

coronary artery blockage

Fig. 22-16, p.371

Coronary Artery Disease

Risk Factors

Smoking GeneticsHigh cholesterol High blood pressureObesity DiabetesAge Gender

Respiration

• Respiration– Physiological process by which oxygen moves into

an animal’s internal environment and carbon dioxide moves out

• Aerobic respiration– Cellular process, produces ATP– Oxygen is used– Carbon dioxide is produced

Respiratory System

• Works with the circulatory system to deliver oxygen and remove carbon dioxide

• Also helps regulate acid-base balance

Pressure Gradients

• Concentration gradients for gases• Gases diffuse down their pressure gradients• Gases enter and leave the body by diffusing

down pressure gradients across respiratory membranes

Factors In Gas Exchange

• Surface-to-volume ratio– Small, flat animals

• Ventilation– Adaptations enhance exchange rate

• Respiratory pigments– Hemoglobin and myoglobin

Surface-to-Volume Ratio

• As animal size increases, surface-to-volume ratio decreases

• Small, flat animals can use the body surface as their respiratory surface

• Larger animals have special structures to increase respiratory surface, such as gills or lungs

Respiratory Surfaces

• In flat animals

CO2 O2

Fish Gills

• Usually internal• Water is drawn in

through mouth and passed over gills

water flows in through mouth FISH GILL

water flowsover gills,then out

water flows into mouth

FISH GILL

water flowsover gills,then out.

mouthopen

lid closed

mouthclosed

lid open

gill arch

gill filament direction of

water flow

respiratory surface

direction of blood flow

oxygen-poor blood from deep

in body

oxygenated blood back toward body

a b c

d e

Fig. 22-18, p.372

Countercurrent Flow

• Blood flows in the opposite direction of water flow over the filaments

• Enhances movement of oxygen from water to blood

direction of water flow

respiratory surface

direction of blood flow

oxygen-poor blood from deep in body

oxygenated blood back toward body

Vertebrate Lungs

• Originated in some fishes as outpouching from gut wall

• Allow gas exchange in air and in oxygen-poor aquatic habitats

salamander

reptile

Avian Respiration

• Lungs are inelastic and connect to a series of air sacs

• Air is drawn continually though each lung

airsacs

airsacs

lungs

airsacs

MammalHuman; adapted

to dry habitats

Fig. 22-20c, p.373

Mammals

Human Respiratory System

pharynx (throat)

larynx (voice box)

trachea (windpipe)pleural membrane

intercostal muscle

diaphragm

epiglottis

Bronchiole

Alveoli

NASAL CAVITY

PHARYNX (THROAT)

EPIGLOTTIS

LARYNX (VOICE BOX)

TRACHEA (WINDPIPE)

LUNG (ONE OF A PAIR)

BRONCHIAL TREE

PLEURAL MEMBRANE

ORAL CAVITY (MOUTH)

INTERCOSTAL MUSCLES

DIAPHRAGM

Fig. 22-21a, p.374

bronchiole

alveolar duct

alveoli

alveolar sac(sectioned)

Fig. 22-21b, p.374

alveolar sac

pulmonarycapillary

Fig. 22-21c, p.374

Speech Production

• Vocal cords stretch across laryngeal opening; opening between them is glottis

• Position of cords is varied to create different sounds

vocal cords

glottis (closed)

epiglottis

tongue’s base

Fig. 22-22a, p.375

Breathing

• Moves air into and out of lungs• Occurs in a cyclic pattern called the

respiratory cycle• One respiratory cycle consists of

inhalation and exhalation

Inhalation

• Diaphragm flattens • External intercostal

muscles contract• Volume of thoracic cavity

increases• Lungs expand• Air flows down pressure

gradient into lungs

Normal (Passive) Exhalation

• Muscles of inhalation relax

• Thoracic cavity recoils

• Lung volume decreases

• Air flows down pressure gradient and out of lungs

INWARD BULK FLOW OF AIR

OUTWARD BULK FLOW OF AIR

b Inhalation. The diaphragm contracts, moves down. External intercostal muscles contract and lift rib cage upward and outward. The lung volume expands.

Fig. 22-23, p.376

c Exhalation. Diaphragm, external intercostal muscles return to resting positions. Rib cage moves down. Lungs recoil passively.

Active Exhalation

• Abdominal and internal intercostal muscles contract• Contraction decreases thoracic cavity volume more

than passive exhalation• Greater volume of air flows out to equalize

intrapulmonary pressure with atmospheric pressure

red blood cell

air spaceinsidealveolus

pore for airflowbetween alveoli

Cutaway View of Alveolus

(see next slide)

Respiratory Membrane

• Area between an alveolus and a pulmonary capillary

• Oxygen and carbon dioxide diffuse across easily

alveolarepithelium

capillaryendothelium

fusedbasementmembranesof bothepithelialtissues

Oxygen Transport

• Most oxygen is bound to heme groups in hemoglobin in red blood cells

• Hemoglobin has higher affinity for oxygen when it is at high partial pressure (in pulmonary capillaries)

• Lower affinity for oxygen in tissues, where partial pressure is low

Bicarbonate Formation

CO2 + H2O H2CO3carbonic acid

HCO3–

bicarbonate+ H+

• Most carbon dioxide is transported as bicarbonate• Some binds to hemoglobin• Small amount dissolves in plasma

alveolar sacs

cells of body tissue

DRYINHAILED AIR

160 0.03

MOISTEXHAILED AIR

120 27

pulmonaryveins

100 40

104 40pulmonary

arteries

40 45

start ofsystematic

veins

40 45

less than 40 more than 45

start ofsystemic

capillaries

100 40

Partial Pressure Gradients

Control of Breathing

• Nervous system controls rhythm and magnitude of breathing

• Breathing is adjusted as a result of changes in– Carbon dioxide levels– Oxygen levels– Blood acidity