blood circulation Flashcards by Amber Taylor

blood direction of arteries

carry blood away from heart to the cells of the body
-all carry oxygenated blood

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pulmonary artery

carries deox blood from heart to lung

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umbilical artery

during pregnancy, carries deox blood from fetus to placenta

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features of the lumen

-central space inside the blood vessel
-gets smaller further away it is from heart

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arterioles

smallest branches of arterial system
-furthest from heart

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structure of arteries

-external layer of tough tissue
-middle layer containing elastic fibres and smooth muscle
-smooth lining allows easiest flow of blood
-lumen small when unstretched of blood

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middle layer of arteries features

-contains elastic fibres and smooth muscle
-arteries nearest heart have more elastic fibres
-those further from heart have greater proportion of muscle tissue

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adaptations of arteries near heart

a lot of elastic fibres so they can stretch to accommodate greater volume of blood without being damaged
-between surges elastic fibres return to original length squeezing blood and moving it in regular flow

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peripheral arteries

-arteries further away from heart
-blood pressure drops

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functionality of peripheral arteries

-muscle fibres in vessel walls contract or relax to change size of lumen
-controlling blood flow

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what do capillaries link

arterioles and venules

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features of capillaries

branch between cells
-substances diffuse between cells and blood quickly
-small diameter- blood travels slow- gives more time for diffusion to occur

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adaptations of capillaries

-thin walls
-no elastic fibres, collagen, smooth muscle
-helps them fit between cells and quick diffusion

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veins carrying blood

-carries blood back towards heart
-carries deox blood

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pulmonary vein

carries oxygen rich blood from lungs back to heart for circulation around body

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umbilical vein

during pregnancy
-carries ox blood from placenta to fetus

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structure of veins

outer tough layer of collagen fibres
-thin layer of smooth muscle- few elastic fibres
-smooth inner surface
-large lumen

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2 veins carry returning blood to heart

inferior vena cava- lower parts of body
-superior vena cava- upper parts of body

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veins as blood reservoirs

-veins hold large amounts of blood
-blood pressure low- eliminated as blood passes through capillary beds

first way blood at low pressure returned to heart for oxygen

semilunar one way valves throughout venous system
-formed from infoldings of inner wall of veins
-valves prevent backflow of blood

second way blood to heart for oxygen

-larger veins between large muscle blocks of body
-when muscle contract during physical activity they squeeze veins
-with valves keeping blood in one direction, this helps squeezing to return blood to heart

how is tissue fluid formed

from the blood

role of tissue fluid

moves substances in and out of cells directly

what are capillary walls not permeable to

everything but large plasma proteins and erythrocytes

what do substances do in tissue fluid to be transported

substances diffuse into cells along concentration gradients and waste products diffuse out into the tissue fluid

factors that effect most of tissue fluid returning to blood vessels after blood leaves capillary beds

water potential -hydrostatic pressure

what exerts osmotic effects in blood

-plasma proteins albumin

how does water potential effect tissue fluid moving back into the blood capillaries

-plasma proteins give blood low water potential of about -3.3 but tissue fluid surrounding capillaries has water potential of -1.3. water moves from area of high to low so water has tendency to move back into blood by osmosis

whats oncotic pressure

tendency for water to move into or out of the capillary by osmosis

how does hydrostatic pressure effect tissue fluid moving back into blood capillaries

residual pressure of heartbeat that stays as blood enters through arterial end of capillary end forcing tissue fluid out through leaky capillary beds

what determines whether tissue fluid moves in or out of capillaries

the balance between oncotic and hydrostatic pressure

hydrostatic pressure as blood flows from arterioles into capillary beds

high tending to force the fluid out of the capillary at around 3.3 kpa

oncotic pressure of plasma in capillaries

constant at around -2.0 kpa

how does tissue fluid fill around cells for substances to diffuse

-hydrostatic pressure forcing fluid out of capillaries higher than oncotic moving water in -fluid squeezed out of capillaries and fills space around cells -where diffusion between blood and cells takes place

what happens at the venous end of the capillaries

-the blood moves steadily and the hydrostatic pressure falls to around 1.0 kpa

why does the hydrostatic pressure fall in the venous end of the capillaries

the pressure from the pulse is completely lost -fluid moves out of capillaries to form tissue fluid so volume of blood in capillaries is lowered

why does the oncotic pressure remain constant in the venous end of the capillaries

due to constant presence of large plasma proteins

how does tissue fluid return to blood vessels

-pressure exerted by water moving into capillaries by osmosis is greater than hydrostatic pressure forcing fluid out so water returns to capillaries -by the time blood enters venules most of tissue fluid is lost

what happens to the 10% of tissue fluid that is not returned to capillaries

drains into blind ended tubes called lymph capillaries and become lymph -lymph capillaries join to become larger vessels

features of lymph vessels

one way valves to prevent lymph flowing backwards -lymph moved through vessels because of muscle contraction as we move

where is the lymph returned to

-neck area where is joins the left and right subclavian veins found under the collar bone

how is lymph different to tissue fluid

-has fewer nutrients and less oxygen as taken up by cells from tissue fluid -high level of fatty acids that are absorbed directly into the lymph system in the villi of the small intestine

where are lymph glands found

at intervals along the lymph vessels

role of lymph glands

where lymphocytes accumulate and produce antibodies -remove bacteria and other pathogens

where are the antibodies emptied from lymph glands

into the blood with the lymph at the subclavian veins