Human Anatomy - Chapter 21

What is hemodynamics?

the means by which blood flow is altered and distributed and by which blood pressure is regulated

What are the three layers of a blood vessel?

1. tunica intima (tunica interna)
2. tunica media
3. tunica externa (tunica adventitia)

What is the tunica intima?

1. innermost layer
2. adjeacent to lumen
3. inner endothelium and basement membrane

What is the tunica media?

1. middle layer
2. smooth muscle and elastic fibres
3. vasoconstriction and vasodilation

What is the tunica externa?

1. outermost layer
2. adjacent to surrounding tissue
3. elastic and collagen fibres

What is angiogenesis?

1. formation of new blood vessels
2. stimulated by some cancers

What are the different types of blood vessels?

1. arteries
2. arterioles
3. blood capillaries
4. venules
5. veins

What are arteries?

carry blood away from the heart to other organs

What are arterioles?

1. small arteries
2. regulate flow into capillary network
3. has precapillary sphincters
4. regulate resistance

What are blood capillaries?

1. tiny vessels that allow the exchange of substances between the blood and body tissues
2. found near almost every cell in the body but varies with the metabolic activty of the tissue
3. micocirculation

What are venules?

small veins

What are veins?

1. blood vessels that carry blood from the tissues back to the heart
2. has valves
3. thinner tunica intima and media; thicker tunica externa

What allows arteries to regulate their diameter?

smooth muscle in the tunica media

What are the types of arteries?

1. elastic (conducting)
2. muscular (distributing)

What are elastic arteries?

1. large diameter
2. more elastic fibres
3. walls function as pressure reservoirs

What are muscular arteries?

1. medium diameter
2. more smooth muscle
3. distribute blood to various parts of the body
4. can contract and relax

Is the aorta muscular or elastic?

elastic

What are anastomoses?

the union of the branches of two or more arteries supplying the same region of the body

What is collateral circulation?

the alternate flow of blood to a body part through an anastomosis

What are end arteries?

arteries that do not form an anastomosis

What can happen if an end artery becomes blocked?

blood cannot flow to the particular region and necrosis can occur

What are the different types of capillaries?

1. continuous
2. fenestrated
3. sinusoids

What are continuous capillaries?

1. endothelial cells form a contiuous tube that is interrupted only by intercellular clefts
2. most capillaries
3. found in CNS, lungs, muscle tissue, and skin

What are fenestrated capillaries?

1. endothelial cells in these capillaries have many fenestrations (pores)
2. found in kidneys, small intestine villi, choroid plexuses of the brain, parts of the eyes, and most endocrine glands

What are sinusoids?

1. wider and more winding
2. endothelial cells may have unusually large fenestrations
3. incomplete or absent basement membrane
4. found in red bone marrow, liver, spleen, anterior pituitary, parathyroid, and adrenal glands

What are considered blood reservoirs?

veins and venules; where most blood is found at rest

What are the different types of capillary exchange?

1. diffusion
2. transcytosis
3. bulk flow

What is diffusion in relation to capillary exchange?

1. all plasma solutes except large proteins crossing the capillary wall
2. prime exception of diffusion of water-soluble materials is in the brain where the BBB exist

What is transcytosis in relation to capillary exchange?

1. all large, lipid-insoluble molecules crossing through the capillary

What is bulk flow in relation to capillary exchange?

1. passive process in which water and dissolved substances (except proteins) pass through the cappilaries (high pressure to low pressure)
2. important for regulation of the relative volumes of blood and interstitial fluid

What does bulk flow depend on in the capillaries?

1. hydrostatic pressure
2. osmotic pressure

What is hydrostatic pressure?

1. from blood/interstitial fluid
2. “fluid pushing” pressure

What is osmotic pressure?

1. from blood colloids/interstitial fluid
2. “fluid pulling” pressure

What is filtration?

1. pressure-driven movement of fluid and solutes from blood capillaries into interstitial fluid
2. blood hydrostatic pressure (BHP) and interstitial fluid osmotic pressure (IFOP)

What is reabsorption?

1. pressure-driven movement of fluid and solutes from interstitial fluid into blood capillaries
2. interstitial fluid hydrostatic pressure (IFHP) and blood colloid osmotic pressure (BCOP)

What is starling’s law of the capillaries?

the near equilibrium at the arterial and venous ends of a capillary by which flow exit and enter

What is edema?

the balance of filtration and reabsorption between interstitial fluid and plasma is disrupted causing and increase in interstitial fluid

What may be the cause of edema?

1. increased blood hydrostatic pressure in capillaries due to an increase in venous pressure
2. decreased concentration of plasma proteins that lower blood colloid osmotic pressure
3. increased permeability of capillaries which allows greater amounts of plasma proteins to leave the blood and enter tissue fluid
4. increased extracellular fluid volume as a result of fluid retention
5. blockage of lymphatic vessels postoperatively or due to filarial worm infection

Where does BHP take place most of the time?

farthest towards the arterial end

Where does IFHP take place most of the time?

toward the arterial end

Where does BCOP take place most of the time?

towards the venous end

Where does IFOP take place most of the time?

farthest towards the venous end

What is blood flow?

the volume of blood that flows through any tissue in a given time period (mL/min)

What does blood distribution depend on?

1. pressure difference driving blood through tissue
2. restistance to flow in blood vessels

What is cardiac output?

1. total blood flow
2. volume of blood that circulates through systemic (or pulmonary) blood vessels each minute

What is blood pressure

pressure exerted on the walls of a blood vessel (pressure in arteries)

What is systolic blood pressure (SBP)?

the highest pressure attained in arteries during systole

What is diastolic blood pressure (DBP)

the lowest arterial pressure during diastole

What is mean arterial pressure (MAP)?

1. the average pressure in the arteries throughout the cardiac cycle
2. MAP = diastolic BP + 1/3 (systolic BP - diastolic BP)

What generates blood pressure?

contraction of the ventricles

What factors effect blood pressure?

cardiac output, blood volume, viscosity, resistance, and elasticity of arteries

What happens to the pressure of blood after it leaves the aorta?

progressively falls to 0 mmHg by the time it reaches the right atrium

What is vascular resistance (R)?

1. the opposition to blood flow due to friction between blood and the walls of blood vessels
2. high R; smaller blood flow

What does vascular resistance depend on?

1. size of the blood vessel lumen (lower the lumen; increased R)
2. blood viscosity (higher viscosity; higher R)
3. total blood vessel length (higher length; higher R)

What is systemic vascular resistance (total peripheral resistance)?

1. all of the vascular resistances offered by systemic blood vessels
2. mostly found in arterioles, capillaries, and venules

What is viscosity?

thick fluids move more slowly and cause greater resistance to flow than thin fluids

What is venous return?

1. the volume of blood flowing back to the heart throught the systemic veins
2. occurs because of the pressure gradient between the venules and the right atrium

How is venous return assisted?

1. valves
2. respiratory pump
3. skeletal muscle pump

How does the skeletal muscle pump operate?

1. while standing at rest, bother proximal valve and distal valve in the leg are open and blood flows upward toward heart
2. contraction of leg muscles compresses the vein and the pushes the blood through the proximal valve (milking)
3. just after muscle relaxation, pressure falls in the previously compressed section of vein causing he proximal valve to close and the distal valve open because the bp in the foot is higher than the leg

How does the respiratory pump operate?

during inhalation:


1. diaphragm moves downward
2. decreses pressure in thoracic cavity
3. increase in pressure in the abdominal cavity

\
result:


1. abdominal veins are compressed
2. greater volume of blood moves from compressed abdominal veins into decompressed thoracic veins and then into the right atrium

How is velocity of blood flow shown?

the increase or decreases of the cross-sectional areas of blood vessels

What is syncope?

sudden loss of consciousness that is not due to head trauma followed by spontaneous recovery

What is the most common cause of syncope?

cerebral ischemia

What is the cardiovascular centre?

a group of neurons in the medulla that regulates heart rate, contractility, and blood vessel diameter

How is the cardiovascular centre controlled?

the higher brain regions and sensory receptors (baroreceptors and chemoreceptors)

What does the output of the cardiovascular centre flow along?

sympathetic and parasympathetic fibres

What does the sympathetic impulses of the cardioaccelerator nerves drive?

increased heart rate and contractility

What does the sympathetic impulses of the vasomotor nerves drive?

moderate state of tonic contraction or vacoconstriction in smooth muscle

What does the parasympathetic impulses of the vagus nerve drive?

decrease heart rate

What is the carotid sinus reflex?

maintaining normal blood pressure in the brain and is intitiated by baroreceptors in the wall of the carotid sinus

What is the aortic reflex?

general systemic blood pressure and is initiated by baroreceptors in the wall of the arch of the aorta or attached to the arch

What happens if blood pressure falls?

1. baroreceptor reflexes accelerate heart rate
2. increase the force of contraction
3. promote vasoconstriction

What do chemoreceptors do to regulate blood pressure?

1. detect change in blood level of O2, CO2, and H+
2. hypoxia, acidosis, and hypercapnia stimulate the chemoreceptors to send impulses to the cardiovascular centre increasing parasympathetic stimulation

What hormones regulate blood pressure?

1. angiotensin II
2. epinephrine
3. norepinephrine
4. antidiuretic hormone
5. atrial natriuretic peptide

How do hormones regulate blood pressure?

1. cardiac output
2. changing systemic vascular resistance
3. adjusting the total blood volume

What hormones affect what about blood pressure?

norepinephrine and epinephrine:


1. increase heart rate and contractility; increased BP

angiotensin II, antidiuretic hormone (ADH), norepinephrine, and epinephrine:


1. vasoconstriction; increased BP

atrial natriuetic peptide (ANP), epinephrine, and nitric oxide:


1. vasodilation; decreased BP

aldosterone and antidiuretic hormone:


1. blood volume increase; increased BP

atrial natriuretic peptide:


1. blood volume decrease; decrease BP

What is autoregulation?

the ability of a tissue to automatically adjust its own blood flow to match its metabolic demand for delivery of oxygen and nutrients and removal of waste

What is often the principal stimulus for autoregulation?

oxygen

What is pulse?

the alternate expansion and elastic recoil of arteries with each heartbeat

What arteries can you feel a pulse?

1. superficial temporal artery
2. facial artery
3. common carotid artery
4. brachial artery
5. femoral artery
6. popliteal artery
7. radial artery
8. dorsalis pedis

Where is the superficial temporal artery found?

medial to ear

Where is the facial artery found?

mandible on line with corner of mouth

Where is the common carotid artery found?

lateral to larynx

Where is the brachial artery found?

medial side of biceps

Where is the femoral artery found?

inferior to inguinal ligament

Where is the popliteal artery found?

posterior to knee

Where is the radial artery found?

lateral aspect of wrist

Where is the dorsalis pedis found?

superior to instep of foot

What is pulse pressure?

the difference between systolic and diastolic pressure

What is the normal average pulse pressure?

40 mmHg

What is shock?

an inadequate cardiac output that results in failure of the cardiovascular system to deliver adequate amounts of oxygen and nutrients to meet the metabolic needs of body cells

What happens because of shock?

1. cellular membranes dysfunction
2. cellular metabolism is abnormal
3. cellular death

What are the types of shock?

1. hypovolemic
2. cardiogenic
3. vascular
4. obstructive

What is hypovolemic shock?

decreased blood volume

i.e. hemorrhage, sweating, diarrhea

What is cardiogenic shock?

poor heart function

i.e. myocardial infarction

What is vascular shock?

inappropriate vasodilation

i.e. anaphylactic shock, neurogenic shock, septic shock

What is obstructive shock?

obstruction of blood flow

i.e. pulmonary embolism

What are the homeostatic responses to shock?

1. activation of the renin-angiotensin-aldosterone system
2. secretion of antidiuretic hormone
3. activation of the sympathetic division of the autonomic nervous system
4. release of local vasodilators

What ar ethe signs and symptoms of shock?

1. clammy, cool, pale skin
2. tachycardia
3. weak, rapid pulse
4. sweating
5. hypotension
6. altered mental status
7. decreased urinary output
8. thirst acidosis

What are the circulatory routes?

1. systemic circulation
2. pulmonary circulation
3. hepatic portal circulation
4. fetal circulation