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80 Cards in this Set

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Name five functions of the peripheral circulatory system.
1) Carry blood
2) Exchange nutrients
3) Transport
4) Regulate blood pressure
5) Direct blood flow
Endothelium
the innermost lining of blood vessels;
composed of simple squamous epithelial cells, continuous with the endocardium of the heart
Pericapillary cells
cells scattered throughout the length of the blood vessel, associated with the endothelial cells;
generally fibroblasts, macrophages, or undifferentiated smooth muscle cells
Continuous capillaries
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
Fenestrated capillaries
endothelial cells with numerous fenestrae;
found in tissues where capillaries are highly permeable
Fenestrae
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
Sinusoidal capillaries
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
Sinusoids
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
Venous sinuses
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
Arterial capillaries
the ends of capillaries closest to the arterioles
Venous capillaries
ends of capillaries closes to the venules
Metarterioles
vessel through which blood flows from arterioles into a thoroughfare channel;
have isolated smooth muscle cells along their walls
Thoroughfare channel
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
Precapillary sphincters
smooth muscle cells located at the origin of capillary branches that regulate the flow of blood through the capillaries
Tunica intima
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
Internal elastic membrane
a fenestrated layer of elastic fibers that separates the tunica intima from the tunica media
Tunic media
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
Vasoconstriction
a decrease in blood vessel diameter caused by smooth muscle contraction;
results in a decrease of blood flow
Vasodilation
an increase in blood vessel diameter because of smooth muscle relaxation ;
results in an increase of blood flow through the vessel
External elastic membrane
a fenestrated layer of elastic fibers which separates the tunica media from the tunica adventitia
Tunica adventitia
the outer layer of a blood vessel wall;
composed of connective tissue of varying thickness
Elastic arteries
blood vessels with the largest diameter, relatively high pressure and a greater amount of elastic tissue and less smooth muscle tissue
Medium arteries
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
Arterioles
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
Venules
vessels composed of endothelium resting on a delicate basement membrane;
Small veins
veinous vessels in which a continuous layer of smooth muscle surrounds the vessel, and a tunica adventitia composed of collagenous connective tissue
Medium veins
collect blood from small veins and deliver it to large veins;
Large veins
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
Valves
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
Vasa vasorum
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
Arteriovenous anastomoses
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
Glomus
an arteriovenous anastomosis that consists of arterioles arranged in a convoluted fashio surrounded by collagenous connective tissue
Pathologic arteriovenous anastomoses
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
Portal veins
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
Arteriosclerosis
a term used to describe degenerative changes in arteries that make them less elastic
Atherosclerosis
refers to the deposition of material in the walls of arteries to form plaques
Laminar flow
flow in a streamlined fashion, with the outer layers of blood flowing more slowly and the innermost layers flowing the fastest
Turbulent flow
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
Blood pressure
a measure of the force blood exerts against blood vessel walls
Cannula
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
Auscultatory method
used to measure blood pressure without surgical procedures or causing discomfort;
used under most clinical conditions
Korotkoff sounds
vibrations produced by turbulent blood flow during systolic surges of blood through a constricted vessel that can be heard through a stethoscope
Systolic pressure
the pressure at which Korotkoff sounds can first be heard
Diastolic pressure
the pressure at which continuous laminar blood flow is reestablished and Korotkoff sounds can no longer be heard
Rate
the volume that passes a specifc point per unit time, usually measured in L/min
Mathematically describe the rate of blood flow
P1 and P2 are the pressures in the vessel at points one and two, respectively, and R is the resistance to flow
Viscosity
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
Hematocrit
the percentage of the total blood volume composed of red blood cells;
as the hematocrit increases, the viscosity of blood increases logarithmically
Critical closing pressure
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
Laplace's law
states that the force that stretches the vascular wall is proportional to the diameter of the vessel times the blood pressure;
Aneurysm
a bulge of the vascular wall in weakened blood vessels;
in danger of rupturing
Compliance
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
Pulse pressure
the difference between systolic and diastolic pressures;
about 40 mm Hg;
stroke volume of the heart and vascular compliance both affect pulse pressure
Capillary exchange
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
Diffusion
the passive movement of substances from a high concentration to a lower concentration;
primary method of capillary exchange
Net filtration pressure (NFP)
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
Net hydrostatic pressure
the difference in pressure between the blood and interstitial fluid
Interstital fluid pressure
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
Net osmotic pressure
the difference in osmotic pressure between the blood and the interstital fluid
Blood colloid osmotic pressure (BCOP)
the osmotic pressure caused by the plasma proteins;
several times larger than the ICOP;
remains relatively constant across capillary bed
Interstitial colloid osmotic pressure (ICOP)
the osmotic pressure caused by proteins in the interstitial spaces
Venous tone
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
Vasodilator substances
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
Vasomotion
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
Autoregulation
the maintenance of blood flow by tissues; mechanisms operate in response to conc. of nutrients in the interstitial fluid;
utilizes same mechanisms as vasomotion
Vasomotor center
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
Vasomotor tone
a condition of constant partial constriction;
produced in response to tonic stimulation from the vasomotor center
Chemoreceptor reflex
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
Central nervous system ischemic response
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
Renin-angiotensin-aldosterone mechanism
a long-term blood pressure regulatory system that helps regulate kidney function and can also influence peripheral resistance by causing vasoconstriction
Renin
an enzyme released by the kidneys into the circulatory system;
acts angiotensinogen to split a fragment off of one end
Angiotensinogen
a plasma protein produced by the liver which is acted on by renin to produce angiotensin I
Angiotensin I
a fragment cleaved off of angiotensinogen by renin;
a protein that is about 10 amino acids long
Angiotensin-converting enzyme
an enzyme found primarily in small blood vessels of the lung;
cleaves two additional amino acids from angiotensin I to produce angiotensin II
Angiotensin II (active angiotensin)
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
Aldosterone
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
Vasopressin mechanism
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
Atrial natriuretic hormone
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
Fluid shift mechanism
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
Stress-relaxation response
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