Circulatory System Flashcards
what does the circulatory system consist of?
heart, blood vessels, & lymphatics
what layers do blood vessels have?
tunica intima, tunica media, tunica adventitia
vasa vasorum
small branched blood vessels through adventitia & outer part of media (veins have more)
nervi vascularis
larger vessels have nerves & lymphatics in adventitia
tunica intima
endothelium, underlying subendothelial CT, internal elastic lamina in large vessels
tunica media
primarily smooth muscle cells & also external elastic lamina
tunica adventitia
fibroelastic CT (dense irregular CT with small amounts of elastic fibers)
elastic (conducting) arteries
arteries that conduct blood to muscular arteries; aorta, pulmonary, brachiocephalic, common carotid, subclavian, common iliac
characteristics of elastic arteries
incomplete internal elastic lamina, thick tunica media, thin adventitia; no distinct external elastic lamina
muscular (distributing) arteries
delivers blood to organs; innervated by postganglionic sympathetic nerve fibers
characteristics of muscular arteries
well developed internal elastic lamina, thick external elastic lamina
arteriole
small artery, tunica media has 1-3 layers of smooth muscle & some elastic fibers
capillaries
- very small arteries that drain blood into organ and into veins
- single layer of endothelial cells
- surrounded by pericytes, reticular/collagenous fibers
continuous (somatic) capillary
- continuous endothelium & basal lamina (no fenestrae)
- pinocytotic
- location: muscle, CT, CNS, exocrine pancreas, gonads
in CNS, what type of tight junction do continuous capillaries have that contributes to the BBB?
occluding junction
fenestrated (visceral) capillaries
- attenuated endothelium with large windows with diaphragms covering them (continuous basal lamina)
- location: mucosa of GI tract, endocrine glands, renal, kidney, choroid plexus, & ciliary body
where do fenestrated endothelium have no diaphragms?
glomerular capillaries
discontinuous (sinusoidal) capillaries
- location: liver & hemopoietic organs such as bone marrow and spleen
- wide gaps between cells (incomplete basal lamina)
veins
vessels that return deoxygenated blood to heart (start as venules)
layers of veins
- intima: endothelial cells
- media: 1-2 layers of smooth muscle
- adventitia: collagen fibers
postcapillary venules
- receive blood from capillaries
- incomplete layer of pericytes
- vasoactive compounds such as histamine & serotonin
muscular venules
no pericytes
small/medium veins have?
- intima: thin subendothelial CT
- media: reticular/elastic fibers with smooth muscle cells
- adventitia: well developed with smooth muscle & elastic fibers
large veins
- superior/inferior vena cava, portal trunk
- thin intima & media
- thick adventitia
venous valves
- small to medium size veins have valves to prevent retrograde blood flow (mostly in lower limb)
- semilunar folds of intima
arteriovenous anastomoses
connections between arterioles & venules with specialized tunica media with a sphincter
what controls the amount of blood flowing into capillaries?
precapillary sphincters
lymphatic vessels
plasma proteins, fluid, enzymes, lipids, antibodies, hormones etc leak from blood vessels & bathe tissues & interstitial spaces
where is lymph recycled to?
back into venous circulation at the base of the neck
what are lacteals important for?
important route of fat absorption in intestine
where do lymphatic vessels originate?
in CT as closed end anastomosing capillaries
what layer do lymphatic vessels do NOT have?
basal lamina
what tissues have no lymphatic system?
CNS & bone marrow
what prevents the back flow of lymph?
paired cusp valves
where are the lymphatics in skeletal muscle located?
only in perimysium
atherosclerosis
lipid laden macrophage formation & fatty deposits in intima that may block the vessel
restenosis
smooth muscle cell proliferation that follows angioplasty procedure that may occlude vessel
aneurysm
ballooning of artery/weakness in artery wall caused by atherosclerosis, syphilis, CT disorders such as ehler’s danlos & marfan’s
varicose veins
tortuous, dilated veins mostly in older people caused by decrease in muscle tone and failure of venous valves
prostacyclin
- from arachidonic acid that functions in the regulatory role of endothelial cells
- inhibits platelet adhesion & clot formation
endothelial cells secrete what compound that causes smooth muscle in tunica media to relax?
nitric oxide (vasodilation)
maternal-fetal circulation
maternal blood is NOT continuous with fetal blood except at placenta/umbilical cord
