Ch. 14 Blood Vessles and Fetal Circulation Flashcards
1
Q
Tunica Interna (intima)
A
- forms inner lining of a blood vessel and is in direct contact with the blood
endothelium: composed of simple squamous epithelium and is continuous with the endocardial lining of the entire cardiovascular system
basement membrane: provides a physical support base for the epithelial layer, collagen fibers affords the basal lamina significant tensile strength, and resilience for stretching and recoil - basal lamina anchors the endothelium to the underlying connective tissue while also regulating molecular movement
Internal elastic lamina: outermost part of the tunica interna, which forms the boundary between the tunica interna and tunica media (diffusion)
2
Q
Tunic Media
A
- muscular and connective tissue that offers the greatest veriation among the different vessel types
- relatively thick; comprised mainly of smooth muscle cells and large amounts of elastic fibers
- role of smooth muscle cells is to regulate the diameter of the lumen wall to regulate the blood flow and blood pressue
- smooth muscle cells causes vascular spasm to prevent the loss of the blood from an injured blood vessel
- causes vasodilation (low pressure) and vasoconstriction (high pressure)
3
Q
Tunica Externa
A
- outer covering of a blood vessel and consists of elastic and collagenous fibers
- external elastic lamina seperates the tunica externs from the tunica media (in arteries)
- contains numerous nerves
- *tiny blood vessels supply tissue of the vessel wall are called vasa vasorum, or vessels to the vessels
- easily seen on large vessels such as the aorta
4
Q
Anatomy of Blood Vessels Types
A
Arteries: carry blood away from the heart to other organs
Arterioles: enter a tissue and small arteries
Capillaries: branch of arterioles that branch into a myriad of tiny vessels, thin walls of capillaries allow exchange of substances between the blood and body tissues
Venules: capillaries within a tissue reunite to form small venules
Veins: venules in turn merge to form progressively larger blood vessels called veins, blood vessels that convey blood from the tissue back to the heart
5
Q
Elastic Arteries
A
- largest arteries and diameter, look yellow (elastic lamina)
- well defined interior and external elastic laminae, with a thick tunica media dominated by elastic fibers, the elastic lamellae
- propel blood onward while the ventricles are relaxing
- elastic fibers momentarily store mechanical energy, functioning as a pressure reservoir
- recoil and convert stored potential energy in the vessel into kinectic energy of the blood
ex. pulmonary trunk and aorta, brachiochephalic, subclvain, common carotid and common iliac
6
Q
Muscular Arteries (distribution)
A
- medium sized that contain more smooth muscle and fewer elastic fibers
- capable of greater vasoconstriction and vasodilation to adjust rate of blood flow
- well defined internal elastic lamina and a thin external elastic lamina
- reduced amount of elastic tissues prevent vessels from recoiling and help propel blood
- muscular lunica media is primarily responsible for the functions of muscular arteries
- vascular tone is contract and maintain state of partial contraction
ex. brachial, radial , femoral and axillary
7
Q
Anastomoses
A
- recieve blood from more than one artery
- alternative route of blood flow is called collateral circulation (coronary bypass)
- can occur between veins and between arterioles and venules
- arteries that do not have anastomoses are called end arteries
- *obstruction of end artery interrupts the blood supply to a whole segment of an organ, producing necrosis of that segment
8
Q
Arterioles/resistance Vessels
A
- microscopic vessels that regulate flow of blood into capillary networks
- have t. interna with a thin elastic laminal tunic media consists of one to two layers of smooth muscle cells having circular orientation in the vessel wall
- terminal end of the arteroile is called metarteriole
- at mertarteriole- capillary junction, precapillary sphincter monitors the blood flow into the capillary
- arterioles play a key role in regulating blood flow from arteries into capillaries by regulating resistance, known as resistance vessels
9
Q
Capillaries (exchange) Vessels
A
- smallest blood vessels
- extensive network of short branched, interconnecting vessels that course among the individual cells of the body
- flow of blood from metarteriole through capillary and into postcapillary venule
- exchange of substances between blood and interstitial fluid
- found near cells in body, but number varies with metabolic activity of the tissue they serve
- contain single layer endothelium and basement membrane but lack both t. externa and t. media
10
Q
Continuous Capillaries
A
- plasma membrane of endothelial cells form a continuous tube that is interrupted only by intercellular cells, gaps between neighbouring endothelial cells
- located: CNS, skeletal and sooth muscle, connective tissue, and the lungs
11
Q
Fenestrated Capillaries
A
- plasma membranes of the endothelial cells in these capillaries have many fenestrations, small pores ranging from 70-100nm
location: kidneys, villi of the small intestine, choroid plexuses of the ventricles in the brain, ciliary processes of the eyes, endocrine glands
12
Q
Sinusoids
A
- wider and more winding than other capillaries
- their endothelial cells may have unusually large fenestrations
- contains an incomplete or absent basement membrane
- very large intercellular clefts that allow proteins and in some cases even blood cells to pass from a tissue into the bloodstream
location: spleen, liver, anterior pituitary gland, parathyroid, adrenal
13
Q
Venules
A
- venules and veins have thin walls that do not readily maintain their shape
- drain capillary blood and begin the return flow of blood back toward the heart
- initially receive blood from capillaries are called postcapillary venules
- smallest venules and have loosely organized intercellular junctions and thus are very porus
- sites of exchange of nutrients and wastes and white blood cell emigration
- postcapillary venules continue to enlarge, acquire one or two layers of circularly arranged smooth muscle cells
- muscular venules have thicker walls and exchanges with the interstital fluid can no longer occur
14
Q
Veins
A
- small veins in the superior and inferior vena cava entering the heart
- have same essential three layers as arteries with little smooth muscle and elastic fibers. tunica externa of a vein is its thickest layer and consists of collagen and elastic fibers
- lack the external or internal elastic laminae; distensible enough to adapt to variations the volume and pressure of blood passing through them, but are not designed to withstand high pressure
- lumen of a vein is larger, and often collapsed when sectioned
- pumping action of the heart is a major factor in moving venous blood back to heart; contraction of skeletal muscles in the free lower limbs helps boost venus return to the heart
- blood pressure is lower than arteries
15
Q
Veins Anatomy
A
- contain valves, thin folds of tunica interna that form flaplike cusps
- project into the lumen, pointing toward the heart
- low blood pressure allows blood returning to the heart to slow and even back up; valves aid in venus return by preventing backflow
- vascular (venus) sinus is a vein with a thin endothelial wall that has no smooth muscle to alter its diameter; surrounding dense connective tissue replaces the tunica media dn tunica externa in providing support
ex. vascular sinus is the coronary sinus of the heart - more numerous than arteries
