blood, tissue fluid & lymph Flashcards
what is carried in the plasma?
- dissolved glucose, amino acids, mineral ions, hormones and plasma proteins
- red and white blood cells
- platelets
state 3 examples of plasma proteins
- albumin: maintains osmotic potential of blood
- fibrinogen: role in blood clotting
- globulins: role in transport and immunity
describe platelets
fragments of megakaryocytes found in red bone marrow
what process are platelets involved in?
clotting mechanism of blood
what % of blood volume is made up of plasma
55%
what are fenestrations
small openings / pores in capillary wall that allow substances to pass through
what effect do plasma proteins have?
osmotic effect - gives blood in capillaries a high solute potential (low water potential) compared to surrounding fluid
what is tissue fluid
fluid that fills gaps between cells after being squeezed out of the capillaries
describe the composition of tissue fluid
- water
- dissolved glucose, amino acids, mineral ions, hormones
- red and white blood cells
- platelets
what is oncotic pressure?
the tendency of water to move into the blood by osmosis
what is the oncotic pressure in capillaries
-3.3kPa
what is hydrostatic pressure?
the pressure exerted by the blood of walls of blood vessels (due to heart contractions)
what is the hydrostatic pressure at the arterial end of the capillary?
4.6kPa
what happens to water at the arterial end of the capillary?
hydrostatic pressure is higher than oncotic pressure, water moves in by osmosis so fluid is squeezed out of the capillaries
what happens as blood moves through the capillaries?
balance changes - hydrostatic pressure falls to 2.3 kPa as fluid has moved out, oncotic pressure is still -3.3 kPa so is stronger than hydrostatic
what happens to water in the venous end of the capillary?
water moves back into the capillary by osmosis
what % of tissue fluid is in the blood vessels once blood has returned to the veins
90%
what % of tissue fluid does not return to the capillaries - where does it go?
10% - drains into lymph capillaries
what is the composition of lymph
similar to plasma + tissue fluid with less oxygen and fewer nutrients - contains fatty acids absorbed from villi of small intestine
how is lymph transported?
through lymph capillaries that get squeezed by body muscles - contain one way valves
how does lymph rejoin the blood
flows into subclavian veins (under clavicle/collar bone)
what are lymphocytes
type of WBC that is part of the immune system
what is a lymph node
small, bean-shaped structure part of immune system
what do lymph nodes do?
filter substances that travel through the lymphatic fluid (eg. bacteria and other debris) from lymph to be ingested by phagocytes
