Circulatory System UNIT 2 Flashcards
The circulatory system is made up of what
The heart and blood vessels
The circulatory system is a what type of system
A mass transport system
Name of blood vessels entering and leaving the liver
The hepatic artery and vein
Name of blood vessels entering and leaving the kidneys
The renal artery and vein
What are arteries
They carry blood from the heart to the rest of the body. Their walls are thick and muscular and have elastic tissue to cope with the high pressure produced by the heartbeat. The inner lining (endothelium) is folded, allowing the artery to stretch, also helps it to cope with high pressure. Is also smooth to reduce friction. All arteries carry oxygenated blood except the pulmonary artery which takes deoxygenated blood to the lungs
What are arterioles
These form a network throughout the body. Blood is directed to different areas of demand in the body by muscles inside the arterioles, which contract to restrict blood flow (constrict, reduce the size of the lumen) or relax to allow full blood flow (dilate, increase size of lumen)
What are veins
Take blood back to the heart under low pressure. Have a wider lumen compared to arteries, with very little elastic or muscle tissue. Veins contain valves to stop blood flowing backwards. Blood flow through the veins is helped by contraction of the body muscles surrounding them. All veins carry deoxygenated blood, except for the pulmonary vein which carries oxygenated blood to the heart from the lungs
How are capillaries adapted for efficient diffusion
Found very close to cells in exchange tissues (eg alveoli in lungs), so short diffusion pathway
Walls are one cell thick
Large network of capillaries to increase surface area for exchange.
What are networks of capillaries in tissue called
Capillary beds
What is tissue fluid
The fluid that surrounds the cells in tissues. It’s made from substances that leave the blood, eg oxygen water and nutrients. Cells take in oxygen and nutrients from the tissue fluid and release metabolic waste onto it. Substances move out of the blood capillaries into the tissue fluid by pressure filtration
What does tissue fluid not contain
Red blood cells or big proteins as they’re too big to be pushed through the capillary walls. Any excess tissue fluid is drained into the lymphatic system which transports this excess fluid from the tissues and takes it back to the circulatory system
What is the lymphatic system
A network of tubes that acts as a drain
How does pressure filtration work
At the start of the capillary bed, nearest the arteries, the pressure inside the capillaries is greater than the pressure in the tissue fluid. This difference in hydrostatic pressure forces fluid out of the capillaries and into the spaces around the cells, forming tissue fluid. Proteins and red blood cells remain in blood. As fluid leaves, the pressure reduces in the capillaries, so the pressure is much lower at the end of the capillary bed that’s nearest to the veins. Due to fluid loss, the water potential is higher than the hydrostatic pressure. The water potential at the end of the capillaries nearest the veins is lower than the water potential in the tissue fluid, so some water re enters the capillaries from the tissue fluid at the vein end by osmosis .
The elastin fibres in the wall of the artery help to smooth out the flow of blood. What happens to these fibres as the pressure of the blood in the artery changes?
They stretch as the pressure increases and recoil as the pressure drops
In children, some diets may result in a low concentration of protein in blood plasma. This can cause an accumulation of tissue fluid. Why?
Water potential gradient is reduced
More tissue fluid formed
Less water absorbed into capillary by osmosis
