8.3 Blood, tissue fluid and lymph Flashcards
what percentage of blood volume is plasma
plasma makes up 55% of blood volume - much of that volume is water
what is plasma
Plasma is a yellow liquid that carries a wide variety of components including dissolved glucose, amino acids, mineral ions, hormones, and the large plasma proteins (including albumin, fibrinogen, globulins). Plasma also transports erythrocytes, white blood cells and platelets.
what is
albumin
fibrinogen
globulins
Albumin – important for maintaining the osmotic potential of the blood
Fibrinogen – important in blood clotting
Globulins – involved in transport and the immune system
what is
erythrocytes
platelets
white blood cells
Erythrocytes – carry oxygen to the cells
Platelets – involved in the clotting mechanism of blood. Platelets are fragments of large cells called megakaryocytes found in the red bone marrow
White blood cells – involved in the immune response of the body (leucocytes)
functions of the blood
The blood transports:
- Oxygen to and carbon dioxide from the respiring cells
- Digested food from small intestine
- Nitrogenous waste products from cells to excretory organs
- Chemical messages (hormones)
- Platelets to damaged areas
- Cells and antibodies involved in the immune response
Blood also contributes to a maintenance of a steady body temperature and acts as a buffer to minimise pH changes.
what is tissue fluid
Capillaries have small gaps in their walls so that liquid and small molecules can be forced out – this forms tissue fluid.
hydrostatic pressure
the pressure exerted by liquid
oncotic pressure
is the tendency of water to move into the blood via osmosis
interaction between hydrostatic and oncotic pressure
The interaction of hydrostatic and oncotic pressure is responsible for the formation and reabsorption of tissue fluid
tissue fluid formation
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Blood enters the capillaries from the arterioles and the small diameter causes high hydrostatic pressure
Pressure forces water, glucose, amino acid, fatty acid, ions and oxygen out of the capillaries at the arterial
Solution is called tissue fluid as it bathes the cells with substances they need
Hydrostatic pressure is greater than oncotic pressure at arterial end of capillary so net movement of liquid is out of the capillaries
Tissue fluid is same composition to plasma except has no erythrocytes and plasma proteins
Diffusion takes place between blood and cells through tissue fluid
tissue fluid reabsorption
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Large molecules (plasma proteins) remain in blood and lower the water potential of the blood remaining in capillaries
Lowered water potential results in high oncotic pressure
At venule end hydrostatic pressure is low due to loss of liquid, water potential is also very low
Net movement of water will be back into capillaries by osmosis.
Once equilibrium of water potential of blood is reached, no more water from the tissue fluid can be reabsorbed back into the blood in the capillaries
Remaining liquid is absorbed into lymphatic system and eventually drains back into bloodstream near the heart
Liquid in lymphatic system is called lymph
Composition of lymph is similar to plasma except no large plasma proteins and less oxygen and nutrients as these would’ve been absorbed.
filtration pressure
Filtration pressure = hydrostatic pressure – oncotic pressure
+ fluid moving out of capillary
- fluid moving into capillary
what happens at the arterial and venous end (tissue fluid)
Arterial end – hydrostatic pressure is greater than oncotic pressure, so fluid is forced out of capillaries
Venous end – hydrostatic pressure is lower than oncotic pressure, so fluid can move back into capillaries by osmosis
lymph
Some of the tissue fluid doesn’t 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. Lymph is similar in composition to plasma and tissue fluid but has less oxygen and fewer nutrients.
It also contains fatty acids, which have been absorbed into the lymph from the villi of the small intestine.
The lymph capillaries join up to form larger vessels.
The fluid is transported through them by the squeezing of the body muscles.
One-way valves prevent the backflow of lymph.
Eventually the lymph returns to the blood.
Along the lymph vessels are the lymph nodes.
Lymphocytes build up in the lymph nodes 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 phagocytes found in the nodes.
The lymphatic system plays a major role in the defence mechanisms of the body.
Enlarged lymph nodes are a sign the body is fighting off an invading pathogen.
tissue fluid formation anogram
billy - blood
probably - pressure
shouldnt - solution
hide - hydrostatic
toms - tissue fluid
duck - diffusion
