Chapter 20 Study Guide Flashcards
1) Define flow.
2) Define perfusion.
3) Can a large organ have a greater flow but less perfusion than a small organ? Explain.
1) Flow is amount of blood flowing through an organ, tissue, or blood vessel in a given time (mL/min/g)
2) Perfusion is the flow per given volume or mass of tissue in a given time (mL,min,g)
3) Yes, because while the flow may be normal, parts of a tissue’s perfusion could be affected by abnormalities such as clots.
1) The blood vessel walls of arteries and veins are composed of how many layers or tunics?
2) The tunica interna (tunica intima) is found where? What is it exposed to What type of tissue does it consist of? The endothelium acts as a what? It secretes chemicals that stimulate what?
1) 3 layers of tunics
2) Tunic interna (intima) is the inner layer, and it is endothelium. It is a selectively permeable barrier and secretes chemicals that stimulate dilation or constriction. It normally repels blood cells and platelets.
1) What layer is the tunica media? What tissue does it consist of? What nervous system regulates it, sympathetic or parasympathetic? Why is this layer important in terms of blood pressure? What does it do?
2) What happens to the lumen diameter during vasoconstriction or vasodilation?
1) Tunica Media: smooth muscle, collagen, and elastic tissue. Regulated in part by sympathetic nervous system; controls vasoconstriction and vasodilation
2) During vasoconstriction the lumen diameter decreases, during dilation the diameter increases. The larger the diameter, the lower the blood pressure
1) What is the outmost layer called besides tunica externa? Why does it have collagen fibers?
2) What does it anchor and who does it provide a passage for?
3) Small vessels called the vasa vasorum supply blood to?
1) Tunica externa or adventitia: Made of collagen fibers, which protect and reinforce blood vessels.
2) It anchors the vessel and provides passage for small nerves and lymphatic vessels
3) The small vessels called Vasa vasorum supply blood to outer part of larger vessels
1) Arteries are built to withstand the surges of?
2) Conducting (elastic or large) arteries are what in terms of size? Can you describe them (for example their tunica media) and how they help with pressure?
3) Can you name some examples?
1) They’re built to withstand surges of blood
2) Conducting arteries: They’re the biggest arteries Have layers of elastic tissue. They expand during systole, taking pressure, and recoil during diastole to help maintain pressure inside of arteries to keep blood flowing.
3) Examples: aorta, common carotid, subclavian, pulmonary trunk, and common iliac arteries.
Distributing (muscular or medium) arteries are smaller branches that distribute blood to specific organs. What are some examples?
Distributing or medium arteries: Distribute blood to specific organs; smooth muscle layers make up 3/4 of their wall’s thickness.
1) Examples: Brachial, Femoral, renal, and splenic arteries.
The smallest of the resistance (small) arteries are called what?
What are metarterioles?
Why do metarterioles have a precapillary sphincter?
1) Arterioles are the smallest arteries. They have a thicker tunica media in proportion to their lumen, and very little tunica externa.
2) Metarterioles are located in some places, and are short vessels that link arterioles to capillaries.
3) They have a precapillary sphincter.that controls blood going into the bed
What is an aneurysm? Where are common sites?
1) A weak point in artery or heart wall. Forms a thin-walled bulging sac that pulsates with each heartbeat and may rupture at any time.
2) Most common sites: abdominal aorta, renal arteries, and arterial circle at base of brain.
1) Sensory structures transmit signals to the brainstem to regulate what 3 things?
2) What do the carotid sinuses measure and what is the name of their receptors?
3) What do the carotid bodies measure and what is the name of their receptors?
4) What do the aortic bodies measure and what is the name of the receptors?
1) Heart rate, blood vessel diameter, and respiration.
2) The carotid sinuses have baroreceptors that measure blood pressure
3) The carotid bodies have chemoreceptors that measure chemical changes in blood composition
4) Aortic bodies have chemoreceptors and they measure chemical changes in blood composition
Why are capillaries sometimes called exchange vessels? What layers or tunica are found in blood capillaries?
1) Capillaries are sometimes called exchange vessels because of the exchange process that happens here between the capillaries and tissues; nutrients and oxygen enter the tissues and wastes and carbon dioxide enter the capillaries.
2) They’re composed of endothelium and basal lamina
Describe the 3 types of capillaries and where they’re found
1) Continuous occurs in most tissues, and have tight junctions to hold endothelial cells together; the least permeable.
2) Fenestrated has lots of tiny holes and occurs in places where filtration occurs, such as the kidneys. 3) Sinusoids have the largest holes and are the most permeable; their holes are big enough to allow RBCs and proteins to escape, so they’re found in the bone marrow and liver.
Capillaries are organized into networks called what? What vessel supplies the capillary network?
Capillaries are organized into capillary beds, which are networks of 10-100 capillaries supplied by a single arteriole or metarteriole.
What structure controls the flow into the capillary network? About three-quarters of the body’s capillaries are shut down at any given time, why is this?
1) Precapillary sphincters control flow as well as the constriction of arterioles upstream.
2) About 3/4 of capillaries are shut down at any given time because we don’t have enough blood to fill them all up at the same time.
At their distal end, capillaries transition into what vessel?
At their distal end, capillaries transition into veins.
Veins are considered the capacitance vessels of the cardiovascular system. Why is this?
Veins are considered the capacitance vessels because they have greater capacity for blood than arteries because their lumen are bigger.
1) Are the walls of veins thin or thick?
2) What structure is found in veins that is not in arteries? In what layer or tunic is this structure in, and what purpose does it serve?
1) They have thinner walls so they can collapse when empty and expand easily.
2) They have valves in their tunica intima, which arteries do not, to ensure a lack of backflow (due to their low pressure).
Postcapillary venules are the smallest of the veins and they received blood from what vessels?
Post capillary venules: receive blood from capillaries.
1) What are venous sinuses? Are they able to vasoconstrict?
2) What venous sinus did you learn with the heart?
1) Venous sinuses: veins with especially thin walls, large lumens, and no smooth muscle (so they cannot vasoconstrict).
2) Examples include the dural venous sinus (brain) and coronary sinus of the heart (wall of heart.)
Large veins are denoted by diameter, what are some of the large veins?
Larger than 10mm in diameter. Ex: venae cavae, pulmonary veins, internal jugular veins, and renal veins.
In a resting adult most of blood is in ________
veins
What are varicose veins? What are causes?
1) Varicose veins are when blood pools in the veins of lower legs due to backflow.
2) Typically occurs in people who stand for long periods of time; this stretches veins and pulls them down, so one way valves fail and blood back flows, further distends the vessels, and their walls grow weak.
Also occurs due to hereditary weakness, obesity, and pregnancy
Hemorrhoids are varicose veins located where?
In the anal canal
The simplest and most common route for blood is what?
Heart> arteries > arterioles > capillaries.> venules> veins > Heart
In a portal system, blood is flowing through how many capillary networks? Where do portal systems occur?
1) In a portal system, blood flows through two consecutive capillary networks before returning to heart
2) Examples include: Between hypothalamus and anterior pituitary; in kidneys; between intestines to liver
1) What is an anastomosis?
2) In an arteriovenous anastomosis (shunt), blood flows from an ______________ directly into a _________________, bypassing capillaries.
1) An anastomosis is a convergence point between two blood vessels other than capillaries.
2) In an arteriovenous anastomosis (shunt), blood flows from an artery directly into a vein, bypassing capillaries.
The most common anastomoses are what? What advantage does this have when a blockage occurs?
Venous anastomosis are most common; vein blockage is less serious than arterial anastomosis.
What is an arterial anastomoses? Why is this important in the coronary circulation?
An arterial anastomosis provides collateral or alternative routes of blood supply to a tissue; this is important in coronary circulation because it provides alternate routes in case of a blockage.
1) Define flow.
2) Define perfusion.
3) Can a large organ have a greater flow but less perfusion than a small organ?
1) Flow is amount of blood flowing through an organ, tissue, or blood vessel in a given time (mL/min/g)
2) Perfusion is the flow per given volume or mass of tissue in a given time (mL,min,g)
3) Yes, because while the flow may be normal, parts of a tissue’s perfusion could be affected by abnormalities such as clots.
What is the typical value for cardiac output in L/min?
5.25 L/min at rest
What two properties is blood flow based on?
Pressure and resistance.
1) The greater the pressure difference between two points, what does that do to flow?
2) The greater the resistance, what does that do to flow?
1) The greater the pressure difference b/t two points then the greater the flow.
2) The greater the resistance the less the flow.
