Chapter 20 - Cardiovascular System: Vessels & Circulation

Question 1

What are tunics?

Answer 1

Layers of blood vessel walls

Question 2

What is the Lumen of a blood vessel?

Answer 2

Inside space of vessel through which blood flows (surrounded by tunics)

Question 3

What is the tunica intima?

Answer 3

Innermost layer of blood vessel
- composed of endothelium
- thin subendothelial layer of areolar connective tissue

Question 4

What is the tunica media?

Answer 4

Middle layer of blood vessel wall
- composed primarily of circularly arranged layers of smooth muscle cells supported by elastic fibers

Question 5

What is the tunica externa (“tunica adventitia”)?

Answer 5

outermost layer of blood vessel wall
- composed of areolar connective tissue that has elastic and collagen fibers
- helps anchor vessel to other structures

Question 6

What is the vasa vasorum?

Answer 6

a network of small arteries that supply blood to the tunica externa

Question 7

What are companion vessels?

Answer 7

arteries and veins that supply the same body region and typically lie next to each other

Question 8

Elastic arteries (“conducting arteries”)

Answer 8

• largest type
• conduct blood from the heart to smaller muscular arteries
• large amount of elastic fibers

Question 9

Muscular arteries (“distributing arteries”)

Answer 9

• medium sized arteries
• distribute blood to specific regions and organs
• elastic fibers are confined to internal elastic lamina (btwn media & intima) and external elastic lamina (btwn media & externa)

Question 10

What are arterioles?

Answer 10

• smallest arteries

Question 11

Vasomotor tone

Answer 11

contracted state of blood vessels (regulated by medulla oblongata)

Question 12

Sympathetic motor tone

Answer 12

• results in vasoconstriction

Question 13

Capillaries

Answer 13

• smallest blood vessels
• connect arterioles to venules (smallest veins)
• consist solely of endothelium

Question 14

What are continuous capillaries?

Answer 14

• most common type
• continuous endothelial lining around lumen that rests on complete basement membrane
• found in muscle, skin, thymus, lungs, brain, spinal cord

Question 15

What are fenestrated capillaries?

Answer 15

• composed of continuous lining of endothelial and complete basement membrane
• small regions of endothelial cells are extremely thin to prevent formed elements from passing through
• found in small intestine, eye, choroid plexus of brain

Question 16

What are sinusoids (“discontinuous capillaries”)?

Answer 16

• more permeable
• incomplete lining of endothelial cells with large gaps and either an absent of discontinuous basement membrane
• allows transport of large substances
• found in red bone marrow, spleen, some endocrine glands

Question 17

What are capillary beds?

Answer 17

• group of capillaries
• blood delivered by a metarteriole
• thoroughfare channels of metarteriole connects to postcapillary venule

Question 18

What are true capillaries?

Answer 18

• branch from metarteriole and make up most of capillary bed

Question 19

What is the precapillary sphincter?

Answer 19

controls blood flow into true capillaries

Question 20

What are venules?

Answer 20

• smallest veins
• companion vessels to arterioles

Question 21

What is a simple pathway?

Answer 21

one major artery delivers blood to a region or organ and then branches into smaller arteries to become arterioles.

Question 22

What are alternative pathways>

Answer 22

• anastomosis (joining of two blood vessels to supply blood to same region)
• arterial: 2+ arteries supply
• venous: 2+ veins drain
• arteriovenous (“shunt”): transports blood from an artery directly into a vein (bypasses capillary bed)

Question 23

What is a portal system?

Answer 23

blood flows through 2 capillary beds, separated by a portal vein (delivers blood to another organ first before being sent back to heart)

Question 24

What is blood flow velocity?

Answer 24

Rate of blood transported per unit time (usually measured in cm/sec)

Question 25

What is vesicular transport?

Answer 25

endothelial cells use pinocytosis to form fluid-filled vesicles which transport to other side of cell and released by exocytosis

Question 26

What is bulk flow?

Answer 26

movement of large amounts of fluids/dissolved substances in a direction down pressure gradient

Question 27

What is hydrostatic pressure (HP)?

Answer 27

physical force exerted by fluid on a structure

Question 28

What is colloid osmotic pressure?

Answer 28

pull of water back into a tissue by the tissue’s concentration of proteins (colloids)

Question 29

What is net filtration pressure (NFP)?

Answer 29

difference between the net hydrostatic pressure and the net colloid osmotic pressure

Question 30

What is local blood flow?

Answer 30

blood delivered locally to capillaries of a specific tissue and is measured in mL/min

Question 31

What is perfusion?

Answer 31

amount of blood entering capillaries per unit time per gram of tissue

Question 32

Degree of vascularization

Answer 32

extent of blood vessel distribution within a tissue
- determines potential ability of blood delivery
- active organs like brain and heart are generally highly vascularized

Question 33

Angiogenesis

Answer 33

formation of new blood vessels in tissues that require them
- amount of vascularization in given tissue may change over time via this process

Question 34

Myogenic response

Answer 34

contraction and relaxation of smooth muscle within blood vessels in response to changes in stretch of vessel

Question 35

What are vasodilators?

Answer 35

substances that cause smooth muscle relaxation which opens arterioles and precapillary sphincters

Question 36

What are vasoconstrictors?

Answer 36

substances that cause smooth muscle contraction which close arterioles and precapillary sphincters

Question 37

What is autoregulation?

Answer 37

process in which tissue regulates or controls its local blood flow in response to changes in metabolic needs
- typically initiated due to inadequate perfusion due to increased tissue metabolic activity

Question 38

What is total blood flow?

Answer 38

amount of blood transported throughout the entire vasculature in a given period of time (usually L/min)
- equals cardiac output

Question 39

What is blood pressure>

Answer 39

the force per unit area that blood exerts against the inside wall of vessels

Question 40

What is a blood pressure gradient?

Answer 40

the change in blood pressure from one end of the vessel to the other
- highest in the arteries as the heart contracts and lowest in the veins
- propels blood through the vessels

Question 41

Pulse pressure

Answer 41

additional pressure placed on arteries from when the heart is resting (diastolic pressure) to when the heart is contracting (systolic pressure)
- measure of eleasticity and recoil of arteries

Question 42

Mean arterial pressure (MAP)

Answer 42

measure of blood pressure on arteries

Question 43

Capillary blood pressure

Answer 43

• pulse pressure disappears by time it reaches arteries
• must be sufficient for exchange of substances

Question 44

Venous blood pressure

Answer 44

movement of blood from capillaries back to the heart via veins: venous return
- veins also have no pulse pressure

Question 45

What is a skeletal muscle pump?

Answer 45

assist movement of blood primarily in limbs
- blood propelled via muscles contracting around veins

Question 46

Respiratory pump

Answer 46

assists movement of blood in thoracic cavity
- diaphragm contracts and flattens, pressure on vessels

Question 47

What is resistance?

Answer 47

amount of friction the blood experiences as it is transported through blood vessels