Histology Flashcards
Epicardium (what it is and 2 layers)
Visceral layer of serous pericardium (mesothelium)
Subepicardial layer - loose connective tissue w/ nerves/vessels/fat
Pericardial cavity - serous fluid
Myocardium
Thickest layer, w/ muscles and electrical/hormone components
Endocardium (4 layers)
Simple squamos epithelium
Fibroelastic layer
Dense connective tissue layer w/ elastic fibers
Subendocardial layer w/ Purkinje fibers and nerves
3 Layers of Vessels (inside out and general components)
Tunica Intima - endothelium/subendothelium/internal elastic lamina
Tunica Media - smooth muscle layers, external elastic lamina
Tunica Adventitia - loose connective tissue, vessels, and nerves
5 Functions of Endothelial Cells in Tunica Intima
Transcytosis (pinocytosis), diapedesis, clotting secretions, vessel tone, blood cell movements (marginalization)
Tunica Media (2)
Has variable thickness of helically-arranged muscle cells
External elastic lamina only in large arteries
Vaso vasorum
Vessels that supply large vessels, in tunica adventitia
Elastic Arteries
Largest arteries, w/ >40 layers of smooth muscle and shittons of elastic fibers
Muscular Arteries
Virtually all “named” arteries, vessels w/ 3-40 layers of smooth muscle and few elastic fibers that serve as distributing a.s. Also thick external elastic lamina
Arterioles
Greatest resistance due to 1-2 layers of smooth muscle and very small lumen - largest muscle/lumen ratio
Metarterioles
Discontinuous smooth muscle - capillary sphincter to regulate flow across capillary beds
3 Specialized ChemoR and BaroR structures
Carotid Sinus - BaroR via IX
Carotid Body (b/w int and ext carotid a.s) - ChemoR via IX and X
Aortic Bodies - ChemoR via X
Capillary General Structure
Single layer of simple squamos w/ lots of pinocytotic vesicles and TJs that sits right on basal lamina w/ no muscle layer or anything. About 7-7.5 microns wide to squeeze one RBC through at a time
Pericytes
Stem cells for capillaries that sit on basal lamina just below
3 Kinds of Capillaries (& locations)
Type I - Continuous Capillaries, in muscle/lung/nervous & connective tissue
Type II - Fenestrated, pores w/ diaphragms (2 layers of PM w/ no cytoplasm) in intestines/pancreas/kidneys/endocrine glands
Type III - Sinusoidal - large pores w/out diaphragms in liver, bone marrow, spleen, lymphoid organs, and some others
Big Difference(s) b/w Type II and III Capillaries
II has complete basal lamina and diaphragms (except renal glumeruli), III does not
Arteriovenous Anastomoses
Shunt around capillary beds for thermoreg and erectile tissue and some glomerula and metarteriole shit
High Endothelial Venules
Specialized in lymph nodes w/ cuboidal cells for diapedesis of WBCs
2 Valved Veins
Medium and large veins
Muscle in Veins
Less, but might have some normal helically arranged in tunica media or longitudinally arranged in adventitia to peristals blood up from lower extremity
