circulatory system Flashcards
why do multicellular organisms need a specialised transport system and what is it called
they have a low surface area to volume ratio, so they need a specialised transport system to carry raw materials from specialised exchange organs to their body cells
called the circulatory system
what is the circulatory system made up of
the heart and blood vessels
what happens in the circulatory system
the heart pumps blood through blood vessels to reach different parts of the body
there are two circuits:
one circuit takes blood from the heart to the lungs, then back to the heart
the other loop takes blood around the rest of the body
the heart has its own blood supply - the left and right coronary arteries
what does blood transport
blood transports respiratory gases, products of digestion, metabolic wastes and hormones
name all types of blood vessels
arteries
arterioles
veins
capillaries
what takes blood into the kidneys
renal artery
what takes blood out of the kidneys
renal vein
what takes blood out of the gut, into the liver
hepatic portal vein
what takes blood directly into the liver
hepatic artery
what takes blood away from the liver
hepatic vein
what takes blood into the lungs
pulmonary artery
what takes blood away from the lungs
pulmonary artery
taking oxygenated blood to body
aorta
taking deoxygenated blood to the heart
vena cava
how are arteries adapted
they carry blood from the heart to the rest of the body
walls are tick and muscular and have elastic tissue to stretch and recoil as the heart beats - maintains high pressure
inner lining (endothelium) is folded, allowing the artery to stretch - maintains high pressure
all arteries carry oxygenated blood except for the pulmonary arteries, which take deoxygenated blood to the lungs
what are arterioles
arteries divide into smaller vessels called 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 the blood flow or relax to allow full blood flow
how are veins adapted
veins take blood back to the heart under low pressure
have wider lumen with very little elastic or muscle tissue
contains valves to stop the blood flowing backwards
blood flow through the veins is helped by contraction of body muscles surrounding them
all veins carry deoxygenated blood, except for the pulmonary veins which carry oxygenated blood to the heart from the lungs
how are capillaries adapted
always found very near cells in exchange tissues (eg alveoli) so there’s a short diffusion pathway
their walls are only one cell thick, which also shortens the diffusion pathway
there are a large number of capillaries, to increase surface area for exchange - networks of capillaries in tissue are called capillary beds
tissue fluid - first stage
at the start of the capillary bed, nearest the arteries, the hydrostatic pressure inside the capillaries is greater than the hydrostatic pressure in the tissue fluid
tissue fluid - second step
the difference in the hydrostatic pressure means an overall outward pressure forces fluid out of the capillaries and into the spaces around the cells, forming tissue fluid
tissue fluid - third step
as fluid leaves, the hydrostatic pressure reduces in the capillaries - so the hydrostatic pressure is much lower at the venule end of the capillary bed
tissue fluid - fourth step
due to the fluid loss, and an increasing concentration of plasma proteins, the water potential at the venule end of the capillary bed is lower than the water potential in the tissue fluid
tissue fluid - fifth stage
this means that some water re-enters the capillaries from the tissue fluid at the venule end by osmosis
