Chapter 21 - Cardiovascular System: Peripheral Circulation And Regulation

Front 1

Name five functions of the peripheral circulatory system.

Back 1

1) Carry blood
2) Exchange nutrients
3) Transport
4) Regulate blood pressure
5) Direct blood flow

Front 2

Endothelium

Back 2

the innermost lining of blood vessels;
composed of simple squamous epithelial cells, continuous with the endocardium of the heart

Front 3

Pericapillary cells

Back 3

cells scattered throughout the length of the blood vessel, associated with the endothelial cells;
generally fibroblasts, macrophages, or undifferentiated smooth muscle cells

Front 4

Continuous capillaries

Back 4

approx. 7-9 micrometers in diameter and their walls exhibit no gaps between the endothelial cells;
less permeable to large molecules than other vessels;
found in muscle, nervous, and other tissues

Front 5

Fenestrated capillaries

Back 5

endothelial cells with numerous fenestrae;
found in tissues where capillaries are highly permeable

Front 6

Fenestrae

Back 6

areas approximately 70-100 nm in diameter in which the cytoplasm is absent and the plasma membrane consists of a porous diaphragm that's thinner than the nromal plasma membrane

Front 7

Sinusoidal capillaries

Back 7

larger in diameter than either continuous or fenestrated capillaries, and basement membrane is less prominent;
occur in such places as endocrine glands, where large molecules cross their walls

Front 8

Sinusoids

Back 8

large-diameter sinusoidal capillaries;
structure suggests that large molecules and sometimes cells can move readily across their walls between the endothelial cells;
common in liver and bone marrow

Front 9

Venous sinuses

Back 9

similar in structure to the sinusoidal capillaries but are larger in diameter;
occur primarily in the spleen, and they have large gaps between the endothelial cells that make up their walls

Front 10

Arterial capillaries

Back 10

the ends of capillaries closest to the arterioles

Front 11

Venous capillaries

Back 11

ends of capillaries closes to the venules

Front 12

Metarterioles

Back 12

vessel through which blood flows from arterioles into a thoroughfare channel;
have isolated smooth muscle cells along their walls

Front 13

Thoroughfare channel

Back 13

a vessel that extends in a relatively direct fashion from a metarteriole to a venule, capillaries branch off of thoroughfare channel;
blood flow through thoroughfare is usually continuous

Front 14

Precapillary sphincters

Back 14

smooth muscle cells located at the origin of capillary branches that regulate the flow of blood through the capillaries

Front 15

Tunica intima

Back 15

the inner layer of a blood vessel wall;
consists of endothelium, a delicate connective tissue membrane, a thin layer of connective tissue (lamina propria), and the internal elastic membrane

Front 16

Internal elastic membrane

Back 16

a fenestrated layer of elastic fibers that separates the tunica intima from the tunica media

Front 17

Tunic media

Back 17

the middle layer of a blood vessel wall;
consists of smooth muscles cells arranged circularly around the blood vessel, and variable amounts of elastic and collagen fibers, as well as an external elastic membrane;
smooth muscle in this layer helps regulate blood flow through vasomotion

Front 18

Vasoconstriction

Back 18

a decrease in blood vessel diameter caused by smooth muscle contraction;
results in a decrease of blood flow

Front 19

Vasodilation

Back 19

an increase in blood vessel diameter because of smooth muscle relaxation ;
results in an increase of blood flow through the vessel

Front 20

External elastic membrane

Back 20

a fenestrated layer of elastic fibers which separates the tunica media from the tunica adventitia

Front 21

Tunica adventitia

Back 21

the outer layer of a blood vessel wall;
composed of connective tissue of varying thickness

Front 22

Elastic arteries

Back 22

blood vessels with the largest diameter, relatively high pressure and a greater amount of elastic tissue and less smooth muscle tissue

Front 23

Medium arteries

Back 23

include most of the smaller unnamed arteries;
walls are relatively thick compared to their diameter;
large numbers of smooth muscle cells that allow these vessels to partially regulate blood supply to different regions of the body

Front 24

Arterioles

Back 24

vessels that transport blood from small arteries to capillaries;
the smallest arteries in which the three tunics can be identified;
capable of vasodilation and vasoconstriction

Front 25

Venules

Back 25

vessels composed of endothelium resting on a delicate basement membrane;

Front 26

Small veins

Back 26

veinous vessels in which a continuous layer of smooth muscle surrounds the vessel, and a tunica adventitia composed of collagenous connective tissue

Front 27

Medium veins

Back 27

collect blood from small veins and deliver it to large veins;

Front 28

Large veins

Back 28

transport blood from the medium veins to the heart;
tunica intima is thin and composed of endothelial cells, a thin layer of collagenous connective tissue, and a few scattered elastic fibers

Front 29

Valves

Back 29

present in veins with a diameter greater than 2 mm;
allow blood to flow toward the heart but not in the opposite direction;
consist of folds in the tunica intima that form two flaps that are shaped and function like the semilunar valves of the heart

Front 30

Vasa vasorum

Back 30

small blood vessels that supply nutrients to thick blood vessel walls by penetrating from the exterior of the vessel and forming a capillary network in the tunica adventitia and the tunica media

Front 31

Arteriovenous anastomoses

Back 31

allow blood to flow from arterioles to small veins without passing through capillaries;
present in large numbers in soles of feet, palms, terminal phalanges, and nail beds;
function in temperature regulation

Front 32

Glomus

Back 32

an arteriovenous anastomosis that consists of arterioles arranged in a convoluted fashio surrounded by collagenous connective tissue

Front 33

Pathologic arteriovenous anastomoses

Back 33

can result from injury or tumors;
can cause direct flow of blood from arteries to veins, and if sufficiently large, lead to heart failure because of tremendous venous return to the heart

Front 34

Portal veins

Back 34

veins that begin in a primary capillary network, extend some distance and end in a secondary capillary network;
two portal vein systems in humans, the hepatic and hypothalamohypophyseal portal systems

Front 35

Arteriosclerosis

Back 35

a term used to describe degenerative changes in arteries that make them less elastic

Front 36

Atherosclerosis

Back 36

refers to the deposition of material in the walls of arteries to form plaques

Front 37

Laminar flow

Back 37

flow in a streamlined fashion, with the outer layers of blood flowing more slowly and the innermost layers flowing the fastest

Front 38

Turbulent flow

Back 38

results when the rate of flow exceeds a critical velocity or when the fluid passes a constriction, a sharp turn, or a rough surface;
occurs primarily in the heart and to a lesser extent where arteries branch

Front 39

Blood pressure

Back 39

a measure of the force blood exerts against blood vessel walls

Front 40

Cannula

Back 40

a tube used to measure blood pressure by placing it into a blood vessel and connecting it to a manometer or an electronic pressure transducer

Front 41

Auscultatory method

Back 41

used to measure blood pressure without surgical procedures or causing discomfort;
used under most clinical conditions

Front 42

Korotkoff sounds

Back 42

vibrations produced by turbulent blood flow during systolic surges of blood through a constricted vessel that can be heard through a stethoscope

Front 43

Systolic pressure

Back 43

the pressure at which Korotkoff sounds can first be heard

Front 44

Diastolic pressure

Back 44

the pressure at which continuous laminar blood flow is reestablished and Korotkoff sounds can no longer be heard

Front 45

Rate

Back 45

the volume that passes a specifc point per unit time, usually measured in L/min

Front 46

Mathematically describe the rate of blood flow

Back 46

P1 and P2 are the pressures in the vessel at points one and two, respectively, and R is the resistance to flow

Front 47

Viscosity

Back 47

a measure of the resistnace of a liquid to flow;
as viscosity increases, the pressure required to force it to flow increases;
when above its normal range, increases the workload of the heart and can result in heart failure

Front 48

Hematocrit

Back 48

the percentage of the total blood volume composed of red blood cells;
as the hematocrit increases, the viscosity of blood increases logarithmically

Front 49

Critical closing pressure

Back 49

the pressure, specific to each vessel, below which the vessel collapses and blood flow through the vessel stops;
during shock, if blood pressure decreases below this value, the vessel will collapse

Front 50

Laplace's law

Back 50

states that the force that stretches the vascular wall is proportional to the diameter of the vessel times the blood pressure;

Front 51

Aneurysm

Back 51

a bulge of the vascular wall in weakened blood vessels;
in danger of rupturing

Front 52

Compliance

Back 52

the tendency for blood vessel volume to increase as the blood pressure increases;
the more easily a vessel stretches, the greater is its compliance, the less easily is stretches, the smaller is its compliance

Front 53

Pulse pressure

Back 53

the difference between systolic and diastolic pressures;
about 40 mm Hg;
stroke volume of the heart and vascular compliance both affect pulse pressure

Front 54

Capillary exchange

Back 54

the movement of substances into and out of capillaries;
the process by which cells receive everything they need to survive and to eliminate metabolic waste products;
must be maintained for cells to survive

Front 55

Diffusion

Back 55

the passive movement of substances from a high concentration to a lower concentration;
primary method of capillary exchange

Front 56

Net filtration pressure (NFP)

Back 56

the force responsible for moving fluid across capillary walls;
the difference between net hydrostatic pressure and net osmotic pressure;
13 mm Hg at arterial end of capillary;
-7 mm Hg at venous end of capillary

Front 57

Net hydrostatic pressure

Back 57

the difference in pressure between the blood and interstitial fluid

Front 58

Interstital fluid pressure

Back 58

the pressure of interstitial fluid within tissue spaces;
negative because of the suction effect of excess fluids being pulled from the interstital spaces by lymphatic vessels

Front 59

Net osmotic pressure

Back 59

the difference in osmotic pressure between the blood and the interstital fluid

Front 60

Blood colloid osmotic pressure (BCOP)

Back 60

the osmotic pressure caused by the plasma proteins;
several times larger than the ICOP;
remains relatively constant across capillary bed

Front 61

Interstitial colloid osmotic pressure (ICOP)

Back 61

the osmotic pressure caused by proteins in the interstitial spaces

Front 62

Venous tone

Back 62

a contiual state of partial contraction of the veins as a result of sympathetic stimulation; increased sympathetic stimulation increases venous tone; decreased sympathetic stimulation decreases venous tone

Front 63

Vasodilator substances

Back 63

chemicals such as carbon dioxide, lactic acid, adenosine, AMP, ADP, K+, H+ that are produced as metabolism increases, diffuse from the tissues supplied by the capillary to the areas of the precapillary sphincter, the metarterioles, and the arterioles, to cause vasodilation

Front 64

Vasomotion

Back 64

periodic contraction and relaxation of the precapillary sphincters in response to conc. of nutrients in the interstitial fluid;
results in a cyclic blood flow through capillaries

Front 65

Autoregulation

Back 65

the maintenance of blood flow by tissues; mechanisms operate in response to conc. of nutrients in the interstitial fluid;
utilizes same mechanisms as vasomotion

Front 66

Vasomotor center

Back 66

an area of the lower pons and upper medulla oblongata that is tonically active and contributes to vasomotor tone;
can be stimulated or inhibited by areas throughout the brain

Front 67

Vasomotor tone

Back 67

a condition of constant partial constriction;
produced in response to tonic stimulation from the vasomotor center

Front 68

Chemoreceptor reflex

Back 68

a relfex that helps maintain homeostasis when oxygen tension in the blood decreases or when carbon dioxide and hydrogen ion conc. increase;
chemoreceptors found in the carotid and aortic bodies produce afferent APs that travel to the medulla and result in increased vasomotor tone

Front 69

Central nervous system ischemic response

Back 69

elevation of blood pressure in response to a lack of blood flow to the medulla oblongata;
functions in response to emergency situations in which blood flow to the brain is severely restricted

Front 70

Renin-angiotensin-aldosterone mechanism

Back 70

a long-term blood pressure regulatory system that helps regulate kidney function and can also influence peripheral resistance by causing vasoconstriction

Front 71

Renin

Back 71

an enzyme released by the kidneys into the circulatory system;
acts angiotensinogen to split a fragment off of one end

Front 72

Angiotensinogen

Back 72

a plasma protein produced by the liver which is acted on by renin to produce angiotensin I

Front 73

Angiotensin I

Back 73

a fragment cleaved off of angiotensinogen by renin;
a protein that is about 10 amino acids long

Front 74

Angiotensin-converting enzyme

Back 74

an enzyme found primarily in small blood vessels of the lung;
cleaves two additional amino acids from angiotensin I to produce angiotensin II

Front 75

Angiotensin II (active angiotensin)

Back 75

a fragment of angiotensin I that has been cleaved by ACE to produce an 8 amino acid fragment;
causes vasoconstriction in arterioles and to some degree in veins, thereby increasing PR and venous return to the heart, raising blood pressure;
also stimulates aldosterone release from the adrenal cortex;
also increases salt appetite, thirst, and ADH secretion

Front 76

Aldosterone

Back 76

a mineralocorticoid released from the adrenal cortex that acts on kidneys to increase the reabsorption of Na+ and Cl- from the filtrate into the extracellular fluid;
with ADH, dereases urine production, raising blood volume and pressure

Front 77

Vasopressin mechanism

Back 77

a blood pressure regulatory mechanism that works in harmony with the renin-angiotensin-aldosterone mechanism in response to changes in blood pressure;
decreases in blood pressure detected by baroreceptors results in ADH seretion by post. pit.;
ADH acts directly on blood vessels to cause vasoconstriction

Front 78

Atrial natriuretic hormone

Back 78

a polypeptide hormone that is released from cells in the atria of the heart in resposne to increased venous return, stretching cardiac muscle cells;
acts on kidneys to increase the rate of urine production and Na+ in the urine, causing blood volume and venous return and vasodilation decreases PR

Front 79

Fluid shift mechanism

Back 79

a blood pressure regulatory mechanism that occurs in response to small changes in pressures across capillary walls, allowing fluid to move to and from interstitial spaces;
begins to act within a few minutes but requires hours to achieve its full functinoal capacity

Front 80

Stress-relaxation response

Back 80

a response characteristic of smooth muscle cells; in which dereases of blood volume cause a decrease in the force applied to the vessel by the blood, the vessel responds by contracting to decrease vessel volume and maintain blood pressure