Flashcards in Histo Exam 2-Blood & lymph vessels study guide Deck (72)
What classifies a macrovasculature?
>0.1mm in diameter
What are examples of macrovessels?
elastic and muscular arteries, large arterioles and veins
What classifies a microvessel?
<0.1mm in diameter
What are examples of microvessels?
arterioles, capillaries, and post-capillary venules
What is the order of blood flow in the heart?
How are blood vessels organized?
according to type and size
what is the purpose of smooth muscle in arteries?
it's important in maintaining high hydrostatic pressure
Why is there little to no smooth muscle in veins?
due to lower pressure in venules
What does smooth muscle do in association with capillary beds?
regulates how much blood can be in capillary beds
What are the basic layers of the vascular wall?
Intima, Media, Adventitia
What is the tunica intima?
single layer of simple squamous epithelia called endothelium.plus a basal lamina and subendothelial layer of loose connective tissue
What is another layer that might be found in the Tunica intima?
internal elastic lamina beneath the subendothelium
What types of vessels would this internal elastic lamina be found?
most prominent in muscular arteries
What is the tunical media?
concentric layer of smooth muscle fibers with interspersed elastic fibers and type 3 collagen
What is found in the tunica media of arteries?
external elastic lamina
What is the tunica adevenitia?
fibroblasts, type 1 collagen, and elastic fibers oriented along the longitudinal axes
What do arteries do?
transport blood away from the heart
What are the two types of arteries?
elastic and muscular
What are examples o elastic arteries?
aorta and its branches
What are the characteristics of elastic arteries?
very thick high walls with high elasticity
What is the purpose of elasticiy in elastic arteries?
elasticity helps stabilize and maintain blood flow during systole and diastole
What are weibel-palade bodies?
rodlike inclusions within the tightly packed endothelial cells specific for elastic fiber
What does the media of elastic arteries consist of?
mostly elastic fibers and concentrically arranged fenestrated elastic lamellae
What happens to the fibers of media in elastic arteries with age?
increase with age
What are the multiple layers of tunical media in elastic arteries?
multiple layers of concentrically arranged smooth muscle fibers and vasa vasorum
What is a vasa vasorum?
small vessesl within the wall of larger vessels
What is adventitia like in elastic arteries?
thin and underdeveloped with mainly fibrocytes, type 1 collagen, elastic fibers, and some vasa vasorum
What do the Weibel-Palade bodies do?
contain secretory granules used for post-synthesis storage of endothelial proteins involved in hemostasis and inflammation
What do WPBs contain?
P-selectin and von Willebrand Factor
What is the purpose of P-selectin?
recruits circulating leukocytes to site of injury
What is he purpose of von Willebrand Factor?
plays a major role in blood coagulation
What is the purpose of vasa vasorum?
supply the thick vessel layers with oxygen and nutrients
What are nervi vasorum?
small unmyelinated sympathetic nerve fibers that stimulate vasoconstriction through release of norepinephrine
What are muscular arteries?
Distributing branches of elastic arteries
What is the purpose of muscular arteries?
control blood flow to organs by contracting and relaxing smooth muscle within the tunica media
What is the tunica intima in muscular arteries like?
prominent internal elastic lamina that sometimes appears undulated/wavy
What is the tunica media like in muscular arteries?
contains up to 40 concentric layers of smooth muscle fibers enveloped by their own basal lamina, type III collagen and may have outer external elastic lamina
What is the tunica adventicia like in muscular arteries?
thin consisting of loosely arranged collagen and elastic fibers, fibrocytes and nerves
What is an aneurysm?
abnormal widening of a portion of an artery due to weakness within the vessel wall
What are common locations for aneurysms?
aorta, popliteal, mesenteric spenic and cerebral arteries
What are characteristics of an arteriole?
endothelium with flat to rounded nuclei and thin subendothelium
What are the tunics like in arterioles?
generally only 1-2 smooth muscle layers thick, no internal or external laminal and sparse adventitia
What are capillaries composed of?
single layer of endothelial cells rolled into a tube and pericytes
What are pericyts?
specialized contractile cells with rounder nuclei that can differentiate into smooth muscle cells in arterioles and venules
What is the purpose of capillaries?
allow for exchange of molecules between blood and tissues
What portion of blood vessels do capillaries comprise?
What are continuous capillaries?
smooth, continuous endothelium with no gaps or pores
How are these continuous capillary cells connected?
through tight occluding junctions with a continuous basal lamina
How do continuous capillaries transport molecules?
Only through transcytosis or diffusion across endothelial cell membranes
Where are continuous capillaries found?
muscle, brain, peripheral nerves, exocrine glands
What are fenestrated capillaries?
endothelial cells held together by tight junctions but have perforated pores with a continuous external basal lamina
Where are fenestrated capillaries found?
kidneys, intestines, endocrine glands
What are discontinuous capillaries?
gaps between endothelial cells that are large enough to allow cells to pass through
Sinusoidal capillaries have_____ fenestrations with _________basal lamina.
Where are sinusoidal capillaries found?
liver, spleen, some endocrine glands, bone marrow
What are postcapillary venules?
resemble large capillaries, lumens are much larger than capillaries or arterioles
What are the puprose of postcapillary venules?
sites at which white blood cells leave circulation and move into tissues
What is the purpose of venules?
allow for gradual transition from capillary to venule
What are characteristics of arterioles?
large lumen diameter with very thin wall
Where do you find veins in relation to arteries?
usually travel near arteries and are sometimes parallel
How do veins differ from arteries?
lumen is less spherical and more irrgularly shaped appear collapsed
What is the reason for the difference in veins vs arteries?
lower blood pressure in veins
How are veins classified?
small, medium, and large depending on their diameter
What are the three tunics in veins?
same as arteries just not well defined
What do the valves in veins consist of?
consist of fibroelastic connective tissue covered on both sides by endothelium
What is the purpose of vein valves?
prevent backflow of blood due to low pressure
Why are valves more prominent in large veins?
wider and under the least amount of pressure
What are varicose veins?
weakness in the media caused by increased intraluminal pressure or a defect in the structure or function of a valve
Where are varicose veins typically found?
hemorrhoids, esophageal varices and spermatic cord
What is the purpose of lymphatic vessels?
transport lymph which flows in one direction toward the heart
What do lymph capillaries consits of?
a single layer of endothelium and a thin incomplete basal lamina