blood, tissue and lymph Flashcards
what is blood
the fluid used to transport materials around the body
what is hydrostatic pressure
the pressure a fluid exerts when pushing against the sides of a vessel or container
what is lymph
the fluid held in the lymphatic system which is a system of tubes that return excess tissue fluid to the blood system
what is oncotic pressure
the pressure created by the osmotic effects of the solute
what is plasma
the fluid portion of the blood
what is tissue fluid
the fluid surrounding cells and tissues
what does blood consists of
a yellow liquid (plasma) and different types of red blood cells and white blood cells and also platelets
what does plasma carry
- dissolved glucose and amino acids
- mineral ions
- hormones
- large plasma proteins such as albumin, fibrinogen, globulins
what are the functions of albumin, fibrinogen and globulin
albumin maintains osmotic potential of the blood
fibrinogen is important in blood clotting
globulins control transport and the immune system
what are platelets
fragments of large cells called megakarocytes in the bone marrow. they are involved in the clotting mechanism
how much does plasma make up (by volume)
55% and much of that is actually water
which components of the blood are involved in transport functions of the blood
red blood cells and plasma
what is the total volume of blood
5dm3
give the total blood cell numbers of ..
- rbc
- wbc
- platelets
rbc = 2.5 x 10^-15
wbc = 5 x 11^-11
platelets = 6 x 10^-12
what are megakarocytes
large bone marrow cells with a lobated nucleus that produce thromocytes which are necessary for normal clotting
how much of the blood do the cells make vs the plasma
cells = 45%
plasma = 55%
what are the different types of cells in the blood
erythrocytes (red blood cells)
leukocytes (white blood cells)
thrombocytes (platelets)
what is the function of erythrocytes
transport oxygen
4-6 million per mm2
what is the function of leukocytes
involved in immunity, 4000-11000 per mm3
what is the function of thrombocytes
involved in blood clotting
200,000-500,000 per mm2
what is plasma composed of
water - approx 92%
proteins - albumins, fibrinogen, antibodies
ions - Na+, K+, Ca2+, Cl-
nutrients - glucose, amino acids, fatty acids
waste products - urea
hormones - insulin, oestrogen
gases - oxygen and carbon dioxide
what is the term for the formation of blood clotting
coagulation
what does coagulation involve
involves a complex series of biochemical reactions involving cellular and protein components
why do blood clots form
artery walls become narrow
what drugs usually prevent blood from clotting
circulating coagulants such as heparin normally prevent blood from clotting
describe the process of coagulation
- when the wall of a blood vessel is damaged, collagen fibres become exposed to the blood
- platelets stick to the exposed collagen fibres and form a plug to stop bleeding
- platelets are activated and release thromoplastins (enzyme released from damaged cells)
- through a cascade complex, thromboplastins convert prothombin (inactive plasma protein) into thrombin (active plasma protein). this process requires calcium and vitamin K
- thrombin catalyses conversion of soluble fibrinogen into insoluble fibrin. the fibrin forms a mesh that traps red blood cells and strengthens platelet plug forming a clot
how is the blood clot eventually reabsorbed
during fibrinolysis (controlled by plasmin enzyme)
state some functions of the blood
- transport food molecules from storage compounds to cells that need them.
- transport hormones
- transport of cells and antibodies involved in the immune response
- transport platelets to damaged areas
- transported digested food from the small intestine
- transport oxygen to and carbon dioxide from cells
- transport nitrogenous waste products from the cells to the excretory organs
what else does the blood contribute to
maintenance of a steady body temperature and acts as a buffer, minimising pH changes
what is different about tissue fluid compared to plasma
tissue fluid does not contain most of the cells found in blood or plasma proteins
describe tissue fluid
formed by plasma leaking out of the capillaries. surrounds the cells in the tissue and supplies them with the oxygen and nutrients they require. as blood plasma leaks from the capillary it carries all the dissolved substances into the tissue fluid. waste products will be carried back into the capillary as some of the tissue fluid returns to the capillary
which substances dissolved in plasma can pass through the pores of the capillary walls
all dissolved substances except plasma proteins
why can’t blood plasma pass through the pores of the capillary walls
plasma proteins give blood a high solute potential compared to the surrounding fluid
how does water move into the blood in the capillaries from the surrounding fluid
by osmosis
what is the term for the tendency of water to move into the blood by osmosis
oncotic pressure (about -3.3kPa)
what happens every time the heart contracts
as blood flows through the arterioles into the capillaries it is still under pressure from the surge of blood that occurs every time the heart contracts
what is the term for the pressure inside blood vessels caused by the hearts contraction
hydrostatic pressure
what is happening at the arterial end of the capillary
the hydrostatic pressure forcing fluid out of the capillaries is relatively high (4.6kPa). this is higher than the oncotic pressure attracting water in by osmosis so tissue fluid that fills spaces between the cells is squeezed out of the capillaries
at the arterial end of the capillary…
… water moves in, fluid squeezes out
what takes place between blood and cells through tissue fluid
diffusion
what happens as blood moves through the capillaries towards the venous system
the balance of forces
what happens at the venous end of the capillary
hydrostatic pressure falls to 2.3kPa in the vessels as the fluid has moved out and the pulse is completely lost. the oncotic pressure is still -3.3kPa so is stronger than the hydrostatic pressure so water moves back into the capillaries by osmosis as it approaches the venous end of the capillaries
at the venous end of the capillary…
..tissue fluid moves back in
what happens when blood returns to the veins
90% of tissue fluid is back in the blood vessels
briefly describe how tissue is formed in terms of hydrostatic and oncotic pressure
- hydrostatic pressure of the fluid pushes fluid back into tissues
- hydrostatic pressure of the tissue fluid tends to push fluid back into capillaries
- the oncotic pressure of the blood tends to pull water back into the blood
- the oncotic pressure of the tissue fluid pulls water into the tissue fluid
what is the hydrostatic pressure at the arterial end and what does this result in
high hydrostatic pressure of 4.6kPa net flow of fluid out of the capillary to form tissue fluid
what is the hydrostatic pressure at the venous end and what does this result in
low hydrostatic pressure of 2.3kPa net flow of fluid back into the capillary
what does the fluid that leaves the blood consist of
a plasma with dissolved nutrients and oxygen.
what remains in the blood after tissue fluid is formed
rbc, most of the wbc, platelets and plasma proteins - they are too large
what is the function of tissue fluid
surrounds cells so exchange of gases and nutrients can occur across the plasma membrane. oxygen and nutrients can enter cells and carbon dioxide and waste can leave the cells
what happens to some of the tissue fluid
they dont return to the capillaries
10% of the liquid that leaves the blood vessels drains into a system of lymph capillaries where it is known as..
…lymph
describe lymph
it is a colourless, pale yellow fluid similar in composition to plasma and tissue fluid with less oxygen and fewer nutrients. contains fatty acids which have been absorbed into the lymph from the villi of the small intestine.
what do the lymph capillaries join up to form
larger vessels
how is lymph transported
through the larger vessels by the squeezing of the body muscles
what prevents the backflow of lymph
one-way valves
how does the lymph eventually return back to the blood
by flowing into the right and left subclavian veins
what are located along the lymph vessels
lymph nodes
what happens in the lymph node
lymphocytes build up when necessary and produce antibodies which are then passed into the blood. lymph nodes intercept bacteria and other debris from the lymph which are ingested by phagoctyes found in the nodes
what does the lymphatic system play a major role in
the defence mechanism of the body
describe the lymphatic system
lymphatic capillaries —> lymph vessels containing valves —> lymph nodes —> lymphatic tissue
what would happen without the lymph system
you would die within 24 hours as the rate of water loss from the body would be too large. this would lead to a buildup of tissue fluid in the tissues called oedema
the journery from blood plasma to lymph
blood plasma —> {ultrafiltration} tissue fluid —> {drainage} lymph
tissue fluid —-> {reabsorption} blood plasma
