Biology 12

Chapter 10 Circulation Class Notes

The circulatory system is the organ system that is largely responsible for the transport of materials such as nutrients, gases, and waste material throughout the body

It consists of the following components:

A. Blood Vessels(i) Arteries & Arterioles

Arteries larger than arterioles in diameter

Arterial layers:-inner endothelium layer (squamous epithelium)-- elastic tissue layer---outer fibrous connective tissue layer

Figure 1: Walls of artery

Arteries can regulate blood pressure: Constriction of arteries →

Dilation of arteries →

(ii) Capillaries Made up of a single layer of endothelial cells

(squamous epithelium) and basement membrane

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Where nutrients, wastes and gases are exchanged from blood to and from tissues surrounding capillaries

Capillary beds (or networks) open and close via pre-capillary sphincter to shunt blood from one body system to another→ known as the ____________ ________ (or _________ ________)

Thus, capillary beds can be bypassed in certain areas to allow blood to move to or concentrate in areas where it is needed more (e.g. digestion vs. Exercise)

Figure 2: Diagram of Capillary bed

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(iii) Veins & Venules

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Veins function to return blood from capillary beds to heart and to act as reservoir for blood as at any time over 70% of blood is found in veins

Walls of veins thinner than arteries

Veins also have valves to prevent back flow of blood which are not present in arteries

Figure 3: Valves in veins

Nervous stimulation of veins can cause t

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in case of injury and bleeding blood moves away from veins in areas of bleeding to areas where there is no injury (this is how veins and venules act as reservoirs)

the two largest veins in body are the superior vena cava (drains head and neck) and inferior vena cava (drains rest of body) which are about 20 mm in diameter

B. Heart A cone shaped muscular organ Located behind the sternum (breast bone)

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Figure 4: Anatomy of the Heart

(a)External Structure Lies within thin membranous fluid filled sac called pericardium-

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Middle layer is made of ____________ which consists of cardiac muscle cells branched and connected via gap junctions

Outer layer called the ____________, ( a.k.a. ________ ____________) is made of squamous epithelial cells and underlying loose connective tissue

(b) Internal Structure

Two thick walled ___________ Both atria and ventricles separated by thick walled _________ Upper atria and lower ventricles separated by __________________

_________ ______________ valve—a.v. valve separating R.A. and R.V. ________ or ________ valve—a.v. valve separating L.A. and L.V. ____________ valves separate ventricles from their blood vessels ________________________—separates R.V. from pulmonary trunk _________________________________—separates L.V. from Aorta _______________________—are fibrous strings that are connected

to the valves and papillary muscles in heart to anchor valves and prevent inversion during contraction of heart

Figure 5: Internal Anatomy of Heart

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C. Path of Blood Through Heart

Superior/Inferior Vena Cava → R.A. → tricuspid valve → R.V. → pulmonary semilunar valve →Pulmonary Trunk → Pulmonary arteries → Lungs → Pulmonary Veins → L.A. → bicuspid or mitral valve →L.V. → aortic semilunar valve → Aorta

Note: heart is double pump with 2 separate paths where oxygenated and deoxygenated blood never mix

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D. Heartbeat

Each heartbeat represents a cardiac cycle It consists of the contraction (__________) and relaxation (_______)

of heart muscle

Each heartbeat lasts about 0.85 seconds

Table 1: Cardiac Cycle: Cardiac Cycle

Time (sec) Atria Ventricles0.15 Systole Diastole0.30 Diastole Systole0.40 Diastole Diastole

E. Heart Sounds Typically has a “lub-dup” sound “lub” _____________________________________________ “dup” _____________________________________________ ____________________ are slushy sounds that occur after the lub—

often due to damaged or ineffective AV-valves that allow blood to pass back into atria

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____________________ results from bacterial infection causing faulty valves, usually the bicuspid and may require surgery to correct (replaced with artificial valves)

F. Pulse

Often measured on radial artery near outer border of palm side of wrist

Arterial wall pulse whenever left ventricle contracts

G. Conduction System: Intrinsic Control of Heartbeat

Figure 6: S.A. and A.V. nodes

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(a) S.A. Node (Sinoatrial) Found in upper dorsal wall of right atrium

(b) A.V. (Atrioventricular) Node

When receives stimulation from SA node, AV node signals ventricles to contract by way of Purkinje fibers

(c) Artificial Pacemaker

(d) Electrocardiogram (ECG or EKG)

Figure 7: EKG

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Records ionic changes that occur with contraction of heart muscle

P wave QRS wave T wave show repolarization of ventricles causing

recovery/relaxation of the ventricles(e) Ventricular Fibrilation

Figure 8: Ventricular Fibrilation

Can be due to drug overdose but cause mostly unknown Can be corrected by defibrillation—

(f) Nervous Control of Heartbeat: Extrinsic Control

Autonomic nervous______________________________________

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Autonomic nervous system made of _______________ and

__________________ nervous system Sympathetic component promotes speeding up heartbeat A variety of factors: increased blood pressure, need for oxygen,

perceived threat or danger or other reasons may activate these systems

Figure 9: Autonomic Nervous System

(g) Blood Pressure and Swiftness of Flow

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Systolic blood pressure is the highest blood pressure and results from blood being pumped out of left ventricle into arteries

Blood pressure decreases with distance from left ventricle

Blood pressure highest in aorta, then drops in arterioles and also again in capillaries due to increase in cross sectional area of blood vessels (see diagram on page 233)

Figure 10: Diagram of how velocity, surface area and blood pressure are related

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As pressure decreases, due to increased cross-sectional area, so does velocity

Slow capillary velocity allows more time for exchange of nutrients, gases, and waste products with tissues

In the veins, blood velocity increases due to:i)

ii) Reduction in cross-sectional area as small venules join to form veins which results in increased velocity

iii)

H.Vascular Pathways

(i) Pulmonary circuit Deoxygenated blood enters via pulmonary arteries Oxygenated blood leaves lungs via pulmonary veins to L.A.

(ii) Systemic Circuit

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Deoxygenated blood enters R.A. via the inferior and superior

vena cava (largest veins)

(iii) Coronary Arteries Are R and L coronary arteries and R & L cardiac veins Found on hearts surface Are small diameter arteries and can become blocked

(iv) Hepatic Portal System

Capillaries in villi of small intestine → converge into venules → hepatic portal vein → divides into smaller venules in liver → sinusoids → central vein → hepatic vein → inferior vena cava

I—Blood

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(i) Helps maintain homeostasis Guards body against microbial invasion Reduces blood loss by clotting

(ii) Blood Components

(a)Plasma Made of suspended or dissolves inorganic & organic

substances in water (see table 10.1 page 301) plasma proteins (7-8 %) of plasma function in:

-- --e.g. bilirubin transported by albumin and ---- maintains blood volume as proteins are too large to pass through capillary walls→ thus, are hyperosmotic with respect to their surrounding tissue fluids-- fibrinogen--immunoglobulins

(b) Red Blood Cells (Erythrocytes)

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4—6 million r.b.c.’s per mm3 of blood Iron from broken haemoglobin is reused Hgb made of four polypeptide chains (2α and 2β chains) that

form the protein __________

Figure 11: haemoglobin molecule

Each polypeptide chain has an iron containing ______ group associated with it—carries oxygen on iron

When rbc’s destroyed in liver, ________ is degraded and excreted by liver to become bile pigments

rbc numbers increase when there is reduced oxygen concentration in blood

Kidneys produce _________________ that stimulates rbc formation in stem cells (erythroblasts) of red bone marrow

Anemia

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is a disease of the blood whereby not enough r.b.c.’s are produced, too much blood is lost or too little haemoglobin per r.b.c.→ symptoms are fatigue and weakness

iron-deficiency anemia—

pernicious anemia—

cured through vitamin B12 injections

(c) White Blood Cells (leukocytes) Larger than r.b.c.’s Have nucleus Fewer than r.b.c.’s (5,000 – 11,000/mm3) Life span ranges from days to years

Types of W.B.C.’s Granules are proteins

Figure 12: Granular vs Agranular Leukocytes

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(a) Granular leukocytes Made of basophils, neutrophils and eosinophils

(i) Neutrophils known as polymorphonuclear leukocytes

(iii) Basophils release chemicals called histamines resulting in increased

blood flow to an area of injury(iv) Eosinophils

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act as phagocytes for pathogens and antibody covered antigens (i.e. foreign bodies)

Both basophils and eosinophils are important in attacking foreign bodies

(b) Agranular leukocytes Spherical or kidney shaped nucleus Made of ___________ and ________________

(i) Monocytes largest of wbc’s Monocytes become _________________ in tissues and

phagocytose bacteria

(ii) lymphocytes Produce antibodies and other immune cells

Leukemia Result is they crowd out other blood cells such as rbc’s

Infectious mononucleosis Viral disease resulting in excess of B-lymphocytes

AIDS

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Platelets (Thrombocytes)

Originate from fragmentation of _____________ in bone marrow 150 000 – 300 000 per ml

Note: when blood clots in a test tube, a yellow fluid forms over the clot which is called _________= plasma without fibrinogen

Steps in the Blood Clotting Process

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Exchange Between Blood And Tissue Fluid

Interstitial fluid is the fluid (similar in composition to blood plasma) that exists between a capillary and the cells surrounding it:

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Two forces control fluid movement (and therefore substances) across capillary walls

i. ____________ Pressure causes water to move from tissue fluid to blood

ii. _________ pressure causes water to move from blood to tissue

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Arterial process is termed filtration because large red blood cells and plasma proteins stay in blood, water and small molecule nutrients can leave however

Substances leaving capillaries contribute to ______ fluid or ________ fluid which exists between cells

Midway in capillaries, blood pressure and osmotic pressures are about equal; solutes such as salts and amino acids diffuse along concentration gradients with nutrients (glucose and oxygen) moving into tissues and wastes (including carbon dioxide) diffuse into capillary blood

In venule side of capillaries, osmotic pressure is greater than blood

pressure; water moves into capillary along with other material

Lymph is returned to venous blood when lymph vessels join _________ ________ in shoulder region

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Circulatory Disorders

a) Hypertension Women = 160/95 Diastolic pressure more critical in treatment Some people have 2 genes that can result in high b.p—one

gene produces angiotensinogen which is converted into a vasoconstrictor by enzyme product of second gene – causes hypertension

b) Hypotension Symptoms: Can be caused by low blood volume (hemorrhage, excessive

fluid loss from diarrhea or vomiting), excessive vasodilation (due to increased parasympathetic, or decreased sympathetic stimulation)

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c) Atherosclerosis

Can occlude blood vessels and prevent blood from reaching different tissues and organs resulting in necrosis of affected tissue

When attached to blood vessel called a _________ If becomes dislodged it is called an ___________

Treatment is proper diet (low in saturated fats and cholesterol) and exercise

d) Stroke and heart Attack

i) Strokes (also called cardiovascular accident)—caused by part of brain being starved of oxygen Causes of stroke are:

-- --

Can cause variety of symptoms depending on what part of brain affected (e.g. speech, motor, sensory, etc.)

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iii. Heart attack (also called myocardial infarction) If coronary artery is only partially blocked, can experience

angina pectoris (left arm pain) Tx. = If completely block coronary artery, major heart attack

results

e) Dissolving Blood Clots ______ (tissue plasminogen activator) both above convert plasminogen into plasmin which can

dissolve clots _____________ (anticoagulant) can also be used to inhibit

stickiness of platelets

f) Clearing Clogged Arteries

i. Angioplasty

Risk of reclosing due to smooth muscle growing in response to trauma

ii. Coronary Bypass Surgery

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Angioplasty

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Coronary bypass surgery

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