Vessels-Sum 6 Flashcards
blood vascular system
components
- arterial vessels AWAY
aorta > arteries > aterioles - microcirulation (2 way fluid exchange w/ tissues and capillaries)
metarterioles > capillaries > tissue > postcapillary venules - venous vessels TOWARDS
venules > veins > SVC/IVC
common structure
3 layers/tunics:
1. tunica intima
2. tunica media
3. tunica externa
tunica intima
inner layer closest to lumen
sublayers:
endothelium- lines vessels, direct contact w/ bloodstream
subendotherlial CT- anchors endothelium to rest of vessel
tunica media
middle muscular layer
smooth muscle and elastic CT for vessel to change lumen diameter for restriction or accomodate volume
tunica externa/adventitia
more detailed
CT layer of most coll I + some coll III + elastic fibers + fibroblasts + white fat cells
has blood vessels and nerves that supply the major vessel
-vasa vasorum for vessels
-nervi vasorum for nerves, mostly sympathetic
merges with loose CT
tunica externa/adventitia
general
outer layer
connects/anchors vessels to surrounding tissues
protective pathway for smaller vessels and nerves that supply vessel wall
tunica media
more detailed
smooth muscles in concentric layers
-lumen diameter changes when contract or relax
vary elastic lamellae and elastic fibers
has external elastic lamina (EEL)
external elastic lamina
laminating outside of tunica media
thicker sheet of elastin w/ holes for nervi and vasa vasorum to contact media
tunica intima
more detailed
sublayers:
endothelium (simple squamous + BM)
subendothelium (mostly loose CT + fibroblasts + smooth muscle cells) rarely thick
internal elastic lamina (laminated outside of intima w/ thicker sheet of elastin w/ holes to aid diffusion)
endothelium organization
almond shaped instead of egg simple squamous aka endothellium lines lumen in all blood vessels
parallel w/ direction of blood flow to reduce shear stress as blood flows over
endothelium functions
maintain structural integrity w
-junctional complexes
-hemidesmosomes
-focal adhesions
coordinate cell activity
-gap junctions
regulate inflammation
-CAMs bind WBC (WBC can unlock junctions)
WBC access
- macrophage release cytokines in response to injury
- endothelial cells extend CAMs
- circulating neutrophils bind CAMs
- neutrophil express integrins
- integrins bind receptors and unlock junctions
- neutrophils enter underlying CT b/t endothelial cells
other endothelium functions
- reg vessel formation via angiogenesis
- modulate smooth muscle activity for vessel diameter and resistance
-myoendothelial junction
-chemicals for vasoconstriction (endothelins)
-chemicals for vasodilation (NO, prostacyclin)
myoendothelial junctions
physical connections b/t endothelial cells (intima) and smooth muscle cells (media) of lots of gap junctions
goal: reduce shear stress via dilation
hyperpolarize and transfer polarization to smooth muscle in media = dec vascular tone
thrombus formation
thrombus: clot that forms in vessel and stays there
removed by:
anticoagulants (prevent fibrinogen convert)
antithrombogenic substances (platelet aggregation)
thrombolytic substances (break down clots)
enhanced by:
prothombogenic substances (von willebrand factor) if injury/tear
weibel-palade bodies
store von willebrand factor for promoting platelet adhesions
low VWF = bleeding problems bc clots take longer to form or are incorrect
most common hereditary blood clotting disorder
elastic arteries
largest arteries aka aorta and main branches
transport large vol of blood away from heart and stretch to accomodate vol change
sublayers: subendothelium, tunica media, tunica externa
media is dominated by elastic lamellae
elastic lamellae aging
number of lamellae in media inc from birth to adult (in aorta)
thickening of intima by coll I = moderate intimal fibrosis
minor fragmentation of media as elastin protein breaks down
muscular arteries
control distribution of blood to major body regions
sublayers:
subendothelium w/ prominent IEL
media w/ prominent EEL and smooth muscle
externa: thick vs. elastic arteries
small arteries
smaller distribution to smaller body regions
resemble muscular arteries structurally
sublayers:
subendothelium w/ IEL but no other CT
media w/ no elastic lamellae, 3-10 layers smooth muscle
externa w/ no vasa or nervi vasorum so thin
arterioles
main resistance vessels in circulation
very vasoactive so constantly dilating/constricting
greatly influence vol of flow to local area
little IEL in subendo
1-2 complete layers of smooth muscle, no EEL or elastic lamellae in media
externa functionally absent, no vasorum
donut shaped
vasoconstriction
via sympathetic fibers that discharge norepinephrine
dilation w/ parasympathetics that release NO
endothelium function as barrier
maintain selective permeability barrier w/
-junctional complexes
exchange gas/nutrients across endothelium via transcellular pathway
-pinocytotic vesicles, receptor mediated endocytosis, active transport, diffusin
surface receptors for histamine, LDL, insulin
endothellium inflammatory function
regulate inflammatory and immune cell traffic
via CAMs that bind WBC
microvasculature
capillaries + vessels that directly interact
metarterioles
regulate blood flow into capillaries
serve as bypass route when they shut off blood to a cap bed
postcapillary venules
receive blood from capillary beds
primary site of WBC migration into tissues
metarterioles characteristics
highly vasoactive like arterioles
tunica media is discontinuous of SM
use precapillary sphincters to constrict entrance (coordination of sphincters forms bypass to postcap venules)
capillary characteristics
passive diffusion and active transport across endothelium
lumen only accommodates 1 RBC
no media or externa, only intima (endothelium)
pericytes
starfish shaped from mesenchymal cells
low level stem cells (>fibroblast, smooth muscle, endothelial)
surround capillaries and help modulate flow thru
cytoplasmic processes wrap around caps
-form gap junctions w/ endothelial cells
types of blood capillaries
continuous
fenestrated
sinusoidal
continuous
@CNS, llungs, skeletal muscle, CT
prevent leaks bc no fenestrations and strong junctional complexes
necessary for BBB and blood-gas barrier
most common
continuous
appearance
marginal folds along edges for WBC’s
numerous pinocytotic vesicles for transport across endothelium
visible pericytes
fenestrated capillaries
@intestines, endocrine glands, kidney (except glomeruli)
permanent windows thru cytoplasm for fluid transfer w/o endocytosis aka faster
have molecular diaphragms to temporarily seal off fenestrations w/ neg ionic charge
not as many pinocytotic vesicles than continuous
sinusoidal
@red marrow, spleen, liver, lymph nodes, suprarenal gland cortex aka places of rapid fluid exchange
largest type of capillary
large fenestrations and large gaps b/t adj cells so RBC and WBC exit
postcapillary venules
aka pericytic venule bc have pericytes
receive blood from cap beds w/ some exchange of metabolites w/ tissue
primary site of WBC migration into tissues w/ marginal folds
venules
blood from caps and postcaps
drain into small veins
paired w/ arterioles
media has 1-2 layers isolated SM cells
externa= thin CT layer around entire circumference
muscular venules
small veins
blood from venules
drain to medium veins
accompany small arteries
valves to prevent backflow
media= 1 SM cell layer discont or continuous
externa = thing layer of CT w/ more elastic
varicose veins
weakened or incompetent valves allow backflow
valves stays partially open so blood settles in leaflets, pools, bulges
medium veins
blood from small > large veins
accompany medium muscular arteries
large lumen, thin walls, valves
media = 2-3 continous layers, visible EEL
externa= thickest layer, elastic and collagen, vasa/nervi vasorum
jugular
large veins
blood from medium > larger veins or R atrium of heart
accompany elastic arteries
large lumen, thin walls, no valves
intima= thick
media= 3+ layers, will transition from smooth>cardiac
externa= thickest layer, SM in longitudinal bundles, vasa/nervi
IVC, portal veins, common iliac
atypical vessels
coronary arteries
great saphenous vein
coronary arteries
structure
first 2 branches off aorta so higher pressure and volume
intima: thick, inc w/ age
media: many more layers smooth
externa: looser coll. I and elastic than muscular
should be muscular
great saphenous vein
drainage for lower limb
media: perpendicular smooth layers + inner layer of longitudinal so some peristalsis ability
used as coronary bypass graft bc thick walls and similar size
lymph system characteristics
no central pump
1 way interaction so collects fluid but not return
driven by skeletal muscle contraction
pathway of lymph
tissue > lymphatic capillary > lymphatic vessels > thoracic duct or R lymphatic duct > venous vessels
filtered in nodes to remove particulates, bacteria, foreign materials
returned to venous blood via internal jugular, subclavian, brachiocephalic veins
no lymph vessels
orbit, inner ear, epidermis, cartilage, bone, CNS
ways to move out of capillaries
- pinocytosis (large moles)
- junctions, fenestrations (by BP)
- diffusion - from concentration gradients
- diffusion across cells - lipid sol only
BP and concentration gradient main driving forces
opposing forces
- hydrostatic pressure (blood vs inside cap walls)
- oncotic pressure- form of osmosis (from higher protein con in plasma vs interstitial)
- interstitial fluid pressure (interstitial fluid vs outside lymph cap walls)
lymphatic capillaries
blind ended so fluid only flow one direction
remove protein rich interstitial fluid > larger lymphatic vessels
no true tunics so only thin endothelium
-no smooth muscle cells, pericytes, valves
have endothelial folds/flaps to prevent backflow
anchoring fibrillin filaments tether to elastic fibers in ECM
lymphatic vessels
conduits that carry lymph from caps to nodes/thoracic ducts
tight junctions, continuous BM so no leaks, elastic fibers surround endothelium
some smooth muscle cells > collagen and elastic around entire vessel
not true tunics
lymphatic ducts
do have tunics and valves
intima: fibroelastic CT, band of elastic fibers where IEL is
media: longitudinal and circumferential layer of SM
externa: longitudinal SM but not consistent layer, vasa vasorum, collagen
smooth muscle
vasculogenesis
de novo formation
mainly in embryos, sometimes in adults after injury
embryonic stem cells (angioblasts or hemangioblasts) > endothelial capillary tubes> primitive vascular network
angiogenesis
new blood vessels branch off and extend from pre-existing
thru development
differentiated endothelial cell migrate from existing > where new vessels needed
vascular remodeling
reshaping vessel walls in response to environmental
angiogenesis process
1.destabilization from parent induced by angiopoieten
2.parent vasodilates and more permeable
3.existing endothelial cells detach from adj cells and BM by disrupting cell junctions and degrade underlying BM
4.migration to angiogenic stimulus
5.tube of endothelium forms
6.tube stabilized by syn of BM and recruit cells for tunica media and externa (pericytes and SM cells)
angiogenesis w/o migration
endothelial progenitor cells recruited from red marrow
EPC are adult stem cells-mobilize in response to dramatic tissue alterations aka complete loss of endothelial cells, vascular implants, ischemic organs/wounds/tumors
EPC similar to embryonic hemangioblasts
capillaries
in a capillary bed
gatekeepers to tissues
2 way fluid exchange b/t blood and tissues
lymph vascular system
collects xs interstitial fluid and returns it to blood
extracellular fluid @tissues = interstitial fluid >enters lymph system = lymph
normal pressures/opposing forces
hydrostatic and oncotic = balanced so little net movement out of blood vessels
lymphatic vessels remove most of remaining fluid
vol of tissue fluid inc = interstitial fluid P drives fluid into lymph capillaries
edema
when capacity for lymphatic drainage exceeded
hydrostatic = too high
oncotic = too low
lymph capillaries = damaged or blocked
BP and vascular remodeling
inc BP or rate of flow = inc vascular wall stress V/V
@arterial vessels
change amount of SM in media
large artery > outward hypertrophy
small artery > inward hypertrophy
arterioles > rarefaction (death) OR inward hypertrophy OR inward remodeling (whole thing smaller)
inc BP = hypertension
rate of flow and remodeling
wall thickness stays the same when flow inc bc not adding pressure
rate inc > inc lumen diameter (larger surface area so less irritation)
rate dec> dec lumen diameter
