Ch 13/14 Cardiovascular Physiology (Day 3)

Question 1

Functional Model of CV System

Answer 1

diagram

• single, closed loop
• valves in veins and heart assure one way-flow
• each side of heart functions as interdependent pump

1. systemic arteries: pressure reservoir (maintains blood flow during ventricular relaxation
2. arterioles: site of variable resistance (adjustable diameters, where biggest drop in pressure occurs)
3. capillaries: gas exchange between blood and cells/tissues
4. post capillary venues: exchange and support leukocyte adhesion and emigration (site of most inflammation)
5. systemic veins: expandable volume reservoir

Question 2

Distribution of Blood in Body at Rest

Answer 2

• know that lungs get 100% of blood output –> distributed to right and left heart
• kidneys get approx 20% from every heartbeat
• skeletal muscle approx 20% –>altered during exercise, redistributed

controlled by diameter of the arterioles

Question 3

Velocity of Blood Flow

Answer 3

see diagram

• velocity of blood flow depends on total cross-sectional area
• highest in aorta (smaller cross-sectional area)
• total blood flow in system in same in aorta as rest of system, even though velocity drops

Question 4

Blood Vessel Structure

Answer 4

• all have layer of endothelial cells, barrier
• arteries have TONS of elastic tissue, thick
• veins have less, more collapsable
• no fibrous tissue in arterioles or capillaries
• capillaries are just single layer of endothelial tissue = greater diffusion
• arterioles have LOTS of smooth muscle

–>see diagram

Question 5

Elastic Arteries

Answer 5

closer to the heart; stretch as blood is pumped into them and recoil when ventricles relax

Question 6

Muscular Arteries

Answer 6

farther from the heart; have more smooth muscle in proportion to diameter; also have more resistance due to smaller lumen

Question 7

Arterioles

Answer 7

20−30 µm in diameter; provide the greatest resistance; control blood flow through the capillaries

Question 8

Ventricular Contraction

Answer 8

1. ventricle contracts
2. semilunar valve opens. blood ejected from ventricles –> arteries
3. aorta and arteries expand and store pressure in elastic walls

Question 9

Ventricular Relaxation

Answer 9

1. isovolumic ventricular relaxation
2. semilunar valve shuts, preventing back flow into ventricle
3. elastic recoil fo arteries sends blood forward into rest of circulatory system

Question 10

systemic circulation pressures

Answer 10

Pressure waves created by ventricular contraction travel into the blood vessels. Pressure in the arterial side of the circulation cycles, but the pressure waves diminish in amplitude with distance and disappear at the capillaries.

Question 11

pulse pressure

Answer 11

pulse pressure = systolic pressure - diastolic pressure

• ->reflects amount of blood that heart is able to pump
• high BP = low pulse pressure

Question 12

mean arterial pressure

Answer 12

MAP = diastolic pressure + 1/3 (pulse pressure)

Question 13

pre capillary sphincters

Answer 13

can close off capillaries in response to local signals

Question 14

blood flow to capillaries regulated by:

Answer 14

• vasoconstriction/vasodilation of arterioles

- precapillary sphincters

Question 15

Capillaries

Answer 15

• smallest vessels: 7-10 µM diameter; have thinnest walls (single layer of flattened endothelial cells supported by basal lamina)
• No smooth muscle, no elastic tissue reinforcement facilitates exchange, as does the large aggregate surface area
• Thin walls and huge total surface area –> diffusion distance from lumen to tissue cells is small
• Plasma and cells exchange materials across thin capillary walls
• Capillary density related to metabolic activity of cells in the tissue (more active = more capillaries, ex. the heart)

Question 16

Continuous Capillaries

Answer 16

Adjacent ECs close together [ex. muscles, heart, skin, adipose tissue & CNS]
–>very little leakage

-Transcytosis may be ONLY mechanism for exchange within CNS—blood-brain barrier

Question 17

Fenestrated Capillaries

Answer 17

Pores in vessel wall [ex. kidneys, intestines & endocrine glands]

Basement membrane: mucoprotein which restricts passage of large molecules (especially proteins)

Question 18

Discontinuous (Sinusoidal) Capillaries

Answer 18

Gaps between cells [ex. bone marrow, liver & spleen; allow the passage of proteins, cells]

–>leakage possible

Question 19

Capillary Exchange

Answer 19

• Exchange between plasma and interstitial fluid via paracellular pathway or endothelial transport
• Small dissolved solutes and gases move by diffusion, depending on lipid solubility and concentration gradient
• Larger solutes and proteins move mostly by vesicular transport and by bulk flow—mass movement in response to hydrostatic or osmotic pressure gradients

Question 20

Filtration

Answer 20

fluid movement out of capillaries

• Caused by hydrostatic pressure (pressure of fluid against vesicle wall)
• Net filtration at arterial end (fluid pushed out of the system)

Question 21

Absorption

Answer 21

fluid movement into capillaries

• Net absorption at venous end (fluid back into the vesicle)
• Caused by colloid osmotic pressure

Question 22

Capillary Beds

Answer 22

• pressure drop across
• arteriole side (net filtration)/venule side (net absorption)
• by the time we get to venous end, net volume of fluid flow is back towards reabsorption

–>see diagram

Question 23

Starling Forces

Answer 23

Net Driving Force = (PH-PT) – σ(πC-πT)
PH = capillary hydrostatic pressure, PT = tissue hydrostatic pressure
πC = capillary oncotic pressure, πT = tissue oncotic pressure,
σ = reflection coefficient
π = colloid osmotic pressure = oncotic pressure (osmotic pressure due to proteins)

• When NDF > 0 Filtration
• When NDF

Question 24

What is the equation for net pressure?

Answer 24

net pressure = hydrostatic pressure (PH) - colloid osmotic pressure (π)

Question 25

Hydrostatic Pressure

Answer 25

forces fluid out of capillary

Question 26

Colloid Osmotic Pressure

Answer 26

of proteins within capillary pulls fluid into the capillary

Question 27

Veins

Answer 27

t-Most of the total blood volume

• Lower pressure (2 mmHg compared to 100 mmHg average arterial pressure)
• Thinner walls than arteries = less elastic, larger lumen; collapse when cut
• need help to return blood to heart

Question 28

What helps veins return blood to heart?

Answer 28

–skeletal muscle pumps: contraction of muscles surrounding veins help force blood towards heart

–venous valves: ensure one-way directional flow (pooling = high BP)

–breathing: diaphragm flattens upon inhalation: increases abdominal pressure compared with thoracic pressure, also moving blood –> hear

Question 29

Lymphatic System

Answer 29

• Returns fluid and proteins to circulatory system [lymphatic endothelium has very porous junctions, and so is much “leakier” than vascular endothelium]
• Transports absorbed fat from intestines –> blood
• Serve as filter for pathogens
• Produces & houses lymphocytes for the immune response

Question 30

Thoracic trunk/right lymphatic trunk

Answer 30

formed from merging lymphatic ducts; deliver lymph into right and left subclavian veins

Question 31

Lymph ducts

Answer 31

formed from merging capillaries

• Similar in structure to veins
• Lymph is filtered through lymph nodes
• when blocked –> edema

Question 32

Lymphatic Capillaries

Answer 32

• smallest; found within most organs

- interstitial fluids, proteins, microorganisms, and fats can enter.

Question 33

Edema

Answer 33

–> fluid buildup

Two main causes:
1. Inadequate drainage of lymph

2. Filtration far greater than absorption
   - -Increase in capillary hydrostatic pressure
   - -Decrease in plasma protein concentration
   - -Increase in interstitial proteins
   - -Increased permeability