Chapter 22- Blood vessels and Circulation Flashcards
blood vessels
- closed circuit of tubes
- arteries carry blood away from the heart
- capillaries are exchange vessels
- veins return blood to heart
- oxygen does not distinguish arteries from veins
summary of circulation
heart-arteries-arterioles-capillaries-venules-veins-heart
blood vessel tissues
endothelium -smooth surface for blood flow -simple squamous epithelium CT -provides elasticity to withstand BP changes smooth muscle -vasoconstriction -vasodilation
blood vessel histology: layers
tunica intima
- innermost
- endothelium on top of CT membrane
- internal elastic membrane
- functions:
- -separates blood flow from vessel wall
- -prevents blood clotting
- -helps regulate BP
layers
tunica media
- middle
- bulk of wall
- smooth muscle and elastic CT
layers
Adventitia (tunica externa)
- arteries: thin
- veins: not so thin
- outer
- made of CT, elastic and collagenous fibers
- attaches artery to surrounding tissues
- contains vasa vasorum
- -BV of BV because they are so thick
arteries: characteristics
strong and elastic
-subdivided into arterioles
differences in arteries and veins
-artery wall thicker
-artery lumen appears smaller
endothelium of artery can not contract
types of arteries
elastic
- large diameter
- in areas of high pressure
- media:
- -high % elastic tissue,
- -less smooth muscle
- examples:
- -pulmonary trunk, aorta, carotid, subclavian, common iliacs
types of arteries
muscular
- large to small diameter
- carry blood to skeletal muscles and organs
- media:
- -much smoother muscle
- -less elastic tissue
- examples
- -femoral, carotids, brachials, mesenteric
arterioles
microscopic continuations of arteries-cant see them
- small diameter
- adventitia is thin
- no external elastic membrane
- no vasa vasorum
capillaries
consist of -only intima: --basement membrane --simple squamous epithelium -very thin -variable permeability materials exchanged: -nutrients -dissolved gases -wastes
capillary permeability
maximized by:
-thin wall
-low BP
-slow blood flow
mechanism of permeability:
-diffusion across endothelial cells: lipids, gases
-diffusion through gaps between endothelium: water, small solutes
-diffusion through pores: water, larger solutes
-vesicular transport with pinocytes (ATP involved): large, bound solutes
continuous capillaries
many: -tight junctions -desmosomes -pinocytes allow movement by: -passive diffusion -active transport locations: -CNS -skeletal muscle -lungs
fenestrated capillaries
- swiss cheese appearance
- -pores
- allow movement of:
- -peptides
- -small proteins
- -molecules that cant make it through likes wastes, plasma components that arent cells
- locations
- -kidneys
- -intestines
- -intestines
- -endocrine glands
- -choroid plexus
sinusoid capillaries
specialized for max exchange by
- large intercellular gaps
- pores
- discontinuous basement membrane
- -allows CELLS to enter/exit
- location
- -spleen and bone marrow
- -liver and adrenal glands
capillary beds
network of interconnected capillaries
- connection for veins and arteries
- depreived from arterioles
- precapillary sphincters
- -manages blood flow to bed
- metarterioles
- -a direct connection through the bed
- -leads to a throughfare channel
anastomses
messing with blood flow in capillaries
- collateral arteries
- -two arteries fuse
- -twice as much blood supplies the arteries
- -found in areas with high O2 demand
- -allow for variable degree of blood flow to capillary beds. can contract one tube or open both
- arteriovenous anastomosis
- -direct connectoin between arteriole and venule
- -where blood flow may be hindered by posture
- -allows to reroute blood flow if hindered in capillary bed
venules
smallest veins that collect blood from capillaries
- can lack a media
- scatter, minimal amount of smooth muscles occasionally
medium sized veins
2-9mm in diameter
- thin media
- few smooth muscle fibers
- thick adventitia
- low bp
- valves
- shape does not need to change, not enough pressure for lots of things that arteries do
large sized veins
- great veins: superior/inferior vena cava, and tributaries
- thin media
- thcik adventitia
- low BP
- valves
venous valves
flap like structures projecting inward -folds of media -found in extremities veins have low BP -valves prevent back flow of blood movement of blood through veins -movement of limbs and contraction of muscles --skeletal muscle pump --positive pressure to push blood up -expansion of the thoracic cavity --involves negative pressure, creating empty space to be filled, sucks blood up --thoracoabdominal pump
blood distribution
- unveven
- -oxygenated blood in the heart, arteries, and capillaries-1/3 of blood
- -deoxygenated, venous blood-2/3 of blood
- known as the blood reservoir
- -allows ability to lose fair amount of blood but still be able to survive and escape, essentially extra blood
- veins contract during blood loss
circuits: pulmonary
pulmonary circuit
- deoxygenated blood goes to lungs from right ventricle
- oxygenated in alveolar capillaries of lungs
- brought to left atrium, then left ventricle
- veins=oxygenated
- arteries=deoxygenated
circuits: systemic
- oxygenated blood goes from left ventricle to body
- deoxygenation occurs in systemic capillaries
- brought to right atrium, then to right ventricle
- veins= deoxygenated
- arteries= oxygenated
