Blood Vessels Flashcards
what does circulatory system consist of
heart - pumps blood
vascular system of afferent and efferent blood vessels
what are efferent vessels
arteries that conduct oxygen and nutrients to tissues that diffuse out through capillaries
what are afferent vessels
veins which convey to the heart carbon dioxide and waste products of metabolism of tissues
what are lymphatics
anastomotic network of vessels that start as blind capillaries which converge into larger lymphatics and drain into large veins
what do lymphatics do
conduct lymph
formed by plasma enriched with immunoglobulins and lymphocytes
produced by lymphatic organs
no RBCS
describe pathway of blood from heart and back around
heart –> large (elastic) arteries –> muscular arteries –> arterioles –> metarterioles –> capillary network –> post capillary venule –> venules –> medium/small size veins (muscular veins) –> large veins –> heart
describe what can be seen in cross section
may find artery and vein as they run parallel
may find artery and vein in same plane of section
describe what can be seen in longitudinal section
may find artery and vein in same plane of section
may find only vein or artery if they are not in same plane of section
may find 2 or more profiles of same artery = structures often wavy, like elbow
name layers of general plan of blood vessels
intima
media
adventitia
describe intima - general plan
endothelium - simple squamous
subendothelial layer
IELM (aka internal elastic lamina)
describe media - general plan
elastic membranes - in elastic arteries
smooth muscle cells
reticular fibers
proteoglycans
describe adventitia - general plan
dense irregular ct
vasa vasorum
sometimes a poorly defined external elastic lamina may exist near media
describe intima of muscular artery
endothelium
subendotheliu layer
IELM - very stained = internal elastic limiting membrane
describe media of muscular artery
4 or more concentric layers smooth muscle
thicker in artery
one mm or more in diameter
describe adventita of muscular artery
dense irregular ct
vasa vasorum
what are vasa vasorum
rich capillary network
blood vessels of the vessels
provides irrigation to half of the media
describe collagen fibers of muscular artery
running in different directions
verhoeff’s hematoxylin highlights elastin and elastic fibers
describe middle sized vein - muscular vein (all layers)
endothelium
no IELM
incomplete media of smooth muscle - often separated by ct
collapsed lumen
adventitia with vasa vasorum
thinner wall
fibers not distinct
what does endothelium sometimes have
tight junctions
describe peculiarities of plane of section for smooth muscle cells
in cross section smooth muscle appears longitudinally
in longitudinal section smooth muscle appears cut transversally
what are fenestrations
wavy structure like sleeve with holes
describe intima of elastic artery
endothelium
subendothelium
IELM
describe media of elastic artery
concentric layers of smooth muscle and elastic membranes
describe smooth muscle cells of elastic artery
extremities with numerous projections
incomplete BM
contains actin and myosin
contains vimentin instead of desmin as in other smooth muscle cells
describe fenestrated elastic membranes of elastic artery
50/60 in humans
5/7 in mouse
Corrugated and hairy elastic fibers due to presence of microfibrils and reticular fibers
describe elastic lamellae of elastic artery
not smooth but hairy due to small elastic fibers protruding from lamellae - fibers inserted between smooth muscle cells
describe plane of section of elastic artery
most muscle cells cut obliquely, some in cross ot longitudinal
shows their extremities reaching adjacent elastic lamellae
describe the smooth muscle and elastic lamellae of elastic artery
smooth muscle cells between fenestrated elastic lamellae
cells are short with pointed extremities attached to elastic lamellae, arranged in groups with different orientations
what do the many smooth muscle cells and many attached elastic lamellae do in elastic artery
contribute to solidity and resilience of wall of arteries submitted to strong rhythmic pulsations of heart
describe verhoeff’s hematoxylin
stains elastic fibers in black
describe masson’s trichome
blue - bright and purple staining
describe hart’s technique
beige with elastic membranes in darker brown
name and describe 2 related diseases
aneurysm - elhers danlos syndrome, reticular fibers mutation = causes rupture of digestive organs and aneurysm
Atherosclerosis = infiltration of intima and media with foam cells, macrophages with cholesterol go to initma and pushes endothelium towards center
describe large vein
no IELM
media = a few layers smooth muscle and no elastic membranes
had intima, media and adventitia
describe arterioles
IELM mainly absent - some elastic fibers
media = 1-2 layers concentric smooth muscle
diameter = 0.5 rbcs or less
describe venules
endothelial cell
absent media
collapsed lumen
no smooth muscle
thin layer adventitia
presence of pericytes
can we ever see rbcs in blood vessels
Sometimes can see them filled with blood - immersion fixation
but if done with perfusion= pushes away all rbcs and causes collasped veins
describe metarterioles and post capillary venules
capillary network found between
very small and difficult to see
ALWAYS consider plane of section
describe intima of arteriole
endothelium
thin layer ct with branching elastic fibers oriented longitudinally
describe media of arteriole
1-2 layers smooth muscle
at sites where arteriole branches into capillaries = smooth muscle cells form pre capillary sphincters which regulate blood flow in capillary network
describe adventitia of arteriole
thin adventitia
ct fibers or fibrils and fibrocytes
where are capillaries found
between metarteriole and post capillary venule
describe volume of capillaries
800 times larger than aorta
describe flow of aorta vs capillaries
aorta = 320mm/sec
capillary = 0.3mm/sec
slow flow is good = allows metabolic exchange between blood and surrounding tissues
lake within flowing river
name 5 functions of capillaries
exchange
nutrition
thermoregulation
blood pressure regulation
Inflammation - macrophages/lymphatics
describe AV anastomosis
helps form blood clot if lose lots of blood = metarterioles lose - helps with blood pressure regulation
why do capillaries have structural variations
permits different levels of metabolic exchange
name classifications of capillaries according to permeability
permeable = fenestrated or sinusoids (large and irregular)
or
impermeable or continuous
what are capillaries composed of
endothelial cell with edges closely opposed to each other
describe post capillary venules - gaps
leave actual or potential gaps at interfaces of endothelial cells
creates passageways for migration of leukocytes
describe post capillary venules - associated with
stellate contractile cells (pericytes)
enclosed by BM
describe sinusoids and gap
large irregular lumen
potential gaps between them permit passage way of wbcs and rbcs
are endothelial cells associated with BM - for capillaries
not associated with bm but are held in place by a large network of thick reticular fibers
describe impermeable or continuous capillaries
tight junctions
clathrin coated
contains trans endothelial channels and pinocytic vesicles
no fenestrations
present in nervous tissue, skeletal, cardiac and smooth muscle, skin, lung and lymphatic organs
describe fenestrated capillaries
tight junctions
contains trans endothelial channels
pinocytic vesicles
fenestrations or pores with diaphragms
present in intestinal mucosa, pancreas, salivary glands, endocrine glands, renal glomerulus of kidney
albumin may pass through fenestrations
what diffuses freely through all capillaries
lipid soluble
what passes through trans endothelial channels - capillaries
small water soluble molecules < 10 A
ions
what passes through vesicles - capillaries
molecules up to <90 A
what passes through pores - capillaries
molecules >90A
describe pressures at arterial end and venous end of capillary
arterial end = higher bp, higher hydrostatic pressure and lower osmotic pressure = water lost
venous end = low hydrostatic pressure and high osmotic pressure = recovery of water
describe lymphatic vessels
channels in ct with lymph
very thin endothelial cells - no occluding and gap junctions
no BM associated with endothelium
endothelial cells are anchored to CT fibers = type 1 and 3 collagen, elastic fibers
what do small or large lymphatic vessels have
valves
folds of wall projecting in lumen
also seen in veins
midsize lymphatics = have valves too and lymphocytes in lumen
what do large lymphatic vessels have
like thoracic duct
smooth muscle cells in their walls
name 4 functions of endothelium
permeability - lipid diffuse
metabolic function
Production of vasoactive substances
antithrombogenic function
describe metabolic function - endothelium
conversion of angiotensin I to angiotensin II
inactivation of bradykinin (a potent stimulator of smooth muscle contraction), serotonin, prostaglandins, norepinephrine, etc
describe production of vasoactive substances - endothelium
endothelium stimulates contraction of smooth muscle cells and nitric oxide relaxes them
describe simplified mechanism of action of endothelin
phosphatidyl inositol phosphate converted to inositol triphosphate
calcium increase activates myosin light chain kinase and triggers secondary messengers
describe simplified mechanism of action of nitric oxide
NO stimulates guanylyl cyclase
cyclic GMP
smooth muscle cell relaxes
what is endothelin and nitric oxide
endothelin = vasoconstriction
nitric oxide = vasodilation
describe antithrombogenic function - endothelium
thrombi form from a cascade of events that produce fibrin from blood fibrinogen
may grown until there is complete obstruction of local flow
emboli may detach and obstruct distant blood vessels
when does blood clotting normally occur
when there is damage to a blood vessel
describe blood clotting pathway
exposure of ct –> platelets immediately adhere to cut edges of vessel –> releases chemical to attract more platelets –> forms platelet plug and external bleeding stops
what is fibrin
factor Ia
fibrous globular protein involved in clotting of blood
describe fibrin
formed by action of protease thrombin on fibrinogen which causes it to polymerize
polymerized fibrin together with platelets forms a hemostatic plug or clot over a wound site = occlusion of blood
describe muscular artery with atherosclerotic plaque
cholesterol oxidizes
macrophages migrate to intima and media of muscular artery
push endothelial cells and they can touch
subdenothelial layer contains thrombin
typically would not happen if good endothelial layer
