Chapter 21: The Cardiovascular System: Blood Vessels and Hemodynamics

Question 1

Define hemodynamics

Answer 1

The forces involves in circulating blood throughout the body and on the blood vessels that constitute the major circulatory routes

Question 2

List and describe the 5 main types of blood vessels

Answer 2

Arteries - carry blood away
Arterioles - small branches arteries
Capillaries - small vessels within tissues
Venules - groups fo capillaries that form small veins
Veins - carry blood toward hearts

Question 3

List the 3 structural layers of a blood vessel from innermost to outermost

Answer 3

Tunica internal - forms the inner lining of a blood vessel and is in direct contact with the blood as it flows through the lumen; consists of 3 layers: endothelium (inner): basement membrane, and internal elastic lamina (outer) that is a thin elastic sheet with window like openings giving a swiss cheese appearance

Tunica media - muscular and connective tissue layer that displays the greatest variation among the different vessel types; separated from the tunica externa by the external elastic lamina

Tunica externa - outer covering of the blood vessel that consist of elastic and collagen fibers that have tiny blood vessels that supply blood to the tissues, called vasa vasorum

Question 4

Describe how sympathetic stimulation is associated with vasoconstriction and vasolidation

Answer 4

Vasoconstriction - sympathetic stimulation stimulates smooth muscle to contract, decreasing the diameter of the lumen of blood vessel

Vasodilation - sympathetic stimulation decreases causing smooth muscle to relax, increasing the diameter of the lumen of blood vessel

Question 5

Define arterial compliance

Answer 5

Arterial walls stretch easily or expand without tearing in response to a small increase in pressure

Question 6

Describe elastic arteries

Answer 6

Largest arteries in body but have relatively think vessel walls

Characterized by well-defined internal and external elastic laminae, alone with a thick tunica media that is dominated by elastic fibers, called the elastic lamellae

As blood is ejected from the hard into elastic arteries, their walls stretch, and the fibers momentarily store mechanical energy, functioning as a pressure reservoir - this stored energy is then covered into kinetic energy of the blood

Question 7

Describe muscular arteries

Answer 7

Their tunica media contains more smooth muscle and fewer elastic fibers compared to elastic arteries

They have thick walls due to the muscle and are capable of greater vasoconstriction and vasodilation

They are referred to as distribution arteries as they contain to branch and ultimately distribute blood to each of the various organs

Question 8

Define anastomoses

Answer 8

Union of the branches of two or more arteries suppling the same body region

They allow for collateral circulation as blood can take an alternate rote to its destination

Question 9

Define end arteries

Answer 9

arteries that do not anastomose

Question 10

Describe the structural components of an arteriole

Answer 10

Arteriole = small artery

The terminal end of an arteriole is called the metarteroile, which tapers toward the capillary junction where the distal most muscle cell forms the precapillary sphincter which monitors the blood flow into the capillary

Question 11

How to arterioles play a role in resistance?

Answer 11

They regulate resistance, the opposition to blood flow due to duration between blood and walls of the blood

Contraction of the smooth muscle of an arteriole causes vasoconstriction, which increases resistance and by contrast relaxation causes vasodilation which decreases resistance

Question 12

The flow of blood from a metarteriole through capillaries and into a postcapilarry venue is called ______

Answer 12

microcirculation

Question 13

Define capillary bed and describe the flow of bloodfrom an arteriole into a venule

Answer 13

Capillary bed is a network of 10-100 capillaries that arises from a single metarteriole

1. Through capillaries: When precapillary sphincters are relaxed (open), blood flows into the capillaries nd when the spinsters are contracted (closed), blood flow ceases

Blood flows intermittently through capillaries due to alternating contraction and relaxation of the smooth muscles, 5 to 10 times per minute, known as vasomotion

2. Throughfare channel: At the distal end of the vessel there is no smooth muscle; it resembles a capillary and is called a thoroughfare channel which provides a direct route for blood from an arteriole to a venue, bypassing capillaries

Question 14

What are the 3 different types of capillaries?

Answer 14

1. Continuous capillaries: the plasma membranes of endothelial cells form a continuous tube that is interrupted only be intercellular clefts, gaps between neighbouring endothelial cells; found in CNS, lungs, muscle tissue, skin
2. Fenestrated capillaries: plasma membranes of endothelial cells in these have many fenestrations (small pores); found in kidneys, small I, choroid plexuses, endocrine glands
3. Sinusoids: widers and more winding that others, the plasma has unusually large fenestrations and large intercellular clefs that allow blood cels to pass from tissue into bloodstream, and has an incomplete or absent basement membrane; found in liver spleen, anterior pituitary, parathyroid and adrenal glands

Question 15

In some parts of the body blood passes from one capillary network into another thorough a vein. This type of circulation is called a _______

Answer 15

portal system

Question 16

Venules that initially receive blood from capillaries are called ________

Answer 16

post capillary venules

Question 17

How do muscular venules differ from postcapilary venules?

Answer 17

Muscular venues are further away from capillaries, they have thicker walls and thus exchanges with interstitial fluid can no longer occur

They have one or two layers of circularly arranged smooth muscle cells

Question 18

How do veins structurally differ from arteries? ?

Answer 18

Veins generally have thin walls compared to their total diameter, having a overall larger lumen

They have a thinner layer of tunica interna and tunica media compared to arteries but have a thick tunica externa compared to arteries

Veins lack the internal or external elastic laminae around in arteries

They withstand lower blood pressure and blood exits in a slow and even flow, compared to rapid bursts

Question 19

What is the purpose of valves in veins?

Answer 19

the low BP allows blood returning to the heart to slow and even back up; the valves aid in venous return by preventing back flow

Question 20

Describe the following veins: vascular sinus, anastomotic veins, superficial veins, deep veins:

Answer 20

Vascular sinus: Endothelial wall lacks smooth muscle to alter in its diameter - the surrounding dense connective tissue replaces the tunica media and externa in providing support

Anastomotic veins: paired sets of veins that chess the accompanying artery to form ladder like rungs between paired veins

Superficial veins: located in the subcutaneous layer of skin and are unaccompanied by parallel arteries but form small connections (anastomoses) with deep veins that travel between skeletal muscles

Question 21

Why are veins and venues known to function as blood reservoirs?

Answer 21

They contain a large percentage of blood volume (64%)

Venoconstriction can reduces volume in reservoirs allowing flow to skeletal muscles and help counteract from in BP to prevent haemorrhage

Question 22

Describe the 3 ways in which capillary change (movement of substances between blood and interstitial fluid) occurs

Answer 22

1. Diffusion: nutrient diffuse down their concentration gradients into interstitial fluids and then into body cells; waste products diffuse down their concentration gradients into blood from body cells; diffuse through fenestrations or intercellular clefts (water soluble), or endothelial cells (lipid soluble)
2. Transcytosis: substances in plasma become encoded within pinocytic vesicles that enter the endothelial cells by endocytosis, and move across the cell and exit the other side via exocytosis
3. Build flow: a passive process in which large #s of particles move rogher in the same direction from areas of higher pressure to lower pressure (filtration or reabsorption); important for regulation of relative volumes of blood and ISF

Question 23

What is the different between filtration and reabsorption during bulk flow?

Answer 23

Filtration: pressure driven movements of fluid and solutes from blood capillaries into ISF

Reabsorption: pressure-drive movement from ISF into blood capillaries

Question 24

Define the following:

net filtration pressure (NFP)
blood hydrostatic pressure (BHP)
interstitial fluid hydrostatic pressure (IFHP)
blood colloid pressure (BCOP)
interstitial fluid osmotic pressure (IFOP)

Answer 24

NFP - determines whether volumes of blood and ISF remain steady or change and thus dictate direction of fluid movement [NFP = (BHP + IFOP) - (BCOP + IFHP)]

BHP (16 mmHg) pushes fluid out of capillaries into ISF whereas IFHP (0 mmHg) opposes pushing fluid from ISF into capillaries

BCOP (26 mmHg) pulls fluid from ISF into capillaries due to colloidal suspension of large proteins that cannot diffuse whereas IFOP (0.1-5 mmHg) opposes and pulls fluid out of capillaries

Question 25

Overall, the volume of fluid and solubles reabsorbed normally is almost as large as the volume filtered. What is this equilibrium referred as?

Answer 25

Starling’s Law of the Capillaries

Question 26

What is an edema?

Answer 26

when filtration greatly exceeds reabsorption, resulting in abnormal increase in ISF volume

Caused by increased capillary blood pressure or increases permeability of capillaries

Question 27

What are the 2 factors that affect how cardiac output becomes distributed into circulatory routes ?

Answer 27

Blood pressure and resistance

The greater the pressure different, the greater the flow but the higher the resistance, the smaller the flow

Question 28

Define blood pressure, systolic blood pressure, and diastolic blood pressure

Answer 28

BP: hydrostatic pressure exerted by blood on the walls of a blood vessel

SBP: highest pressure attained in arteries during systole

DBP: lowest arterial pressure during diastole

As BP leaves the aorta and flows through the systemic circulation, its pressure progressively falls

Question 29

Define mean arterial pressure (MAP)

Answer 29

The average blood pressure in arteries is roughly 1/3 of the way between the DBP and SBP

MAP = diastolic BP + 1/3 (systolic BP - diastolic BP)

Question 30

What 3 factors does vascular resistance depend on?

Answer 30

Size of lumen - the smaller, the greater resistance

Blood viscosity - the higher, the greater resistance

Total blood vessel length - the longer, the greater resistance

Question 31

Define systemic vascular resistance (SVR) or total peripheral resistance (TPR)

Answer 31

All of the vascular resistances offered by systemic blood vessels

Arterioles work to control SVY by changing their diameters

Question 32

Besides the heart, what are two other mechanisms that pump blood from the lower body back to the heart?

Answer 32

1. Skeletal muscle pump - contraction of leg compresses vein, pushing blood through the proximal valve (milking) and the distal valve closes as blood is pushed against it to prevent back flow
2. Respiratory pump - inhalation causes compression of abdominal veins and a greater volume of blood moves into the decompresses thoracic veins and into the right atrium

Question 33

What affects the velocity of blood flow?

Answer 33

Velocity (speed) is slowest where the total cross-sectional area is greatest

Each time an artery branches, the total cross-sectional area becomes larger; each time a venue unites to form veins, the total cross-sectional area becomes smaller

Question 34

What is the normal circulation time?

Answer 34

1 min

pass from the right atrium through pulmonary circulation, back to left atrium, through systemic circulation, down to the foot and back to the right atrium

Question 35

What is the role of the cardiovascular center in blood pressure and blood flow?

Answer 35

Receives input from proprioceptors, baroreceptors and chemoreceptors

Output flows along sympathetic ANS to the heart via cardiac accelerator nerves

Output flows along parasympathetic ANS to the heart via vagus (X) nerves

Output flows also to vasomotor nerves - sympathetic smooth muscle neurons that exit the spinal cord through all thoracic and 1-2 lumbar spinal nerved and then passes into the sympathetic trunk ganglia where it innervates blood vessels in viscera and peripheral areas

Question 36

What is vasomotor tone?

Answer 36

A moderate state of tonic contraction that sets the resulting level of systemic vascular resisitance

Occurs dow to the vasomotor region of cardiovascular center continually sending impulses via the vasomotor nerves

Question 37

Describe how the nervous system regulates blood pressure via negative feedback loops using baroreceptor reflexes

Answer 37

Baroreceptors in the wall of the carotid sinuses initiate the carotid sinus reflex which sends nerve impulses via the glossopharyngeal (IX) nerves to the cardiovascular center which helps regulate blood pressure in the brain

Baroreceptors in the wall of the ascending aorta and arch initiate the aortic reflex which sends nerve impulses via the vagus (X) nerves to the cardiovascular centre which regulates systemic blood pressure

As pressure falls, baroreceptors are stretched less and send impulses at a slower rate and the CV centre decreases parasympathetic stimulation and increases sympathetic stimulation to increase BP and vice versa

Question 38

Describe how the nervous system regulates blood pressure via negative feedback loops using chemoreceptor reflexes

Answer 38

chemoreceptors in the carotid sinus are called carotid bodies and chemoreceptors in the arch of the aorta are aortic bodies

When they detect changes in chemical composition of blood they send impulses to CV centre that increases sympathetic stimulation to arterioles and veins, producing vasoconstriction to increase BP

Question 39

How does renin-agionotensin-aldosterone (RAA) system regulate blood pressure?

Answer 39

When blood volume/flow decreases kidneys secrete renin into bloodstream that interacts with angiotensin-converting enzyme (ACE) to produce the active hormone angiotensin II which raises BP by increasing vascular resistance and stimulating aldosterone which increase Na+ and water reabsorption into kidneys that increase BP and volume

Question 40

How does epinephrine and norepinephrine help regulate blood pressure?

Answer 40

These hormones increase cardiac output by increasing HR and force of contractions as well as cause vasoconstriction of arterioles and veins to increase blood flow during exercise

Question 41

How does antidiuretic hormone (ADH) help regulate blood pressure?

Answer 41

ADH is released by posterior pituitary in response to dehydration or decreased blood vL - it causes vasoconstriction, which increased BP and promotes movement of water from kidneys into bloodstream to increase blood vL

Question 42

How does atrial natriuretic peptide (ANP) help regulate blood pressure?

Answer 42

lowers BP by causing vasodilation and by promoting the loss of salt and water in using which reduces blood vL

Question 43

Describe autoregulation of blood flow

Answer 43

Ability of a tissue to automatically adjust its blood flow to match its metabolic demands that is caused by 2 general types of stimuli:

1. physical changes: warming promotes vasodilation and cooling causes vasoconstriction; smooth muscles exhibits a myogenic response - it contractions more forcefully when it is stretched and relaxes when stretching lessens
2. vasodilation and vasoconstricting chemicals

Question 44

What does your pulse refer to?

Answer 44

The alternate expansion and recoil of elastic arteries after each systole of the left ventricle

Question 45

What does a sphygmomanometer measure?

Answer 45

Typically measures the BP in the racial artery in the left arm as in clinical use, BP refers to the pressure in arteries generated by the left ventricle during systole and diastole

The first sound corresponds to a SBP - the force of BP on arterial walls just after ventricular contraction

Sounds while taking BP are called korotkoff sounds

Question 46

What is the pulse pressure?

Answer 46

The difference between systolic and diastolic pressure - normally about 40 mmHg

Question 47

What is shock and decrribe the 4 types :

hypovolemic shock
cariogenic shock
vascular shock
obstructive shockWhat

Answer 47

Shock: failure of CVS to deliver enough O2 and nutrients to meet cellular metabolic needs

hypovolemic shock - decreased blood volume

cariogenic shock - due to poor heart function

vascular shock - inappropriate vasodilation

obstructive shock - obstruction of blood flow

Question 48

What negative feedback systems are activated in response to shock that return cardiac output and arterial pressure to normal?

Answer 48

1. activation of the renin-angiotensin-aldosterone system
2. Secretion of antidiuretic hormone (ADH)
3. Activation of the sympathetic division of ANS
4. Release of local vasodilators

Question 49

Which of the following is not a common sign or symptom of shock?

A) SBP lower than 90mmHg 
B) rapid resting heart rate 
C) weak and rapid pulse 
D) Cool, pale, and clammy skin 
E) Reduced urine production 
F) SBP lower than 50 mmHg
G) low blood pH

Answer 49

F) SBP lower than 50 mmHg

Question 50

What is systemic circulation and what the subdivisions?

Answer 50

Includes all arteries and arterioles that carry oxygenated blood from the left ventricle to systemic capillaries, plus the veins and venues that return deoxygenated blood to the right atrium after flowing though body organs

Subdivisions:

• coronary circulation supplies myocardium of heart
• cerebral circulation supplies the brain
• Hepatic portal circulation extends from GI tract to liver

Question 51

What is pulmonary circulation?

Answer 51

When blood returns to the heart from the systemic route, it is pumped out of the right ventricle to the pulmonary circulation to the lungs

deoxygenated blood from R ventricle –> pulmonary trunk –> right and left pulmonary arteries –> alveoli of lungs –> return by four pulmonary veins which deliver oxygenate blood to the left atrium

Question 52

What is fetal circulation?

Answer 52

Exisits only in the fetus and contains special structures that allow the developing fetus to exchange materials with its mother

Question 53

What is hepatic portal circulation?

Answer 53

Nutrient-rich (deoxygenated) blood from the digestive organs is carried o the liver by the hepatic portal vein

Question 54

Define hypertension

Answer 54

Persistently high blood pressure