Mass Transport in Animals - A5 Flashcards
Why have a circulatory system?
Multicellular organisms have a low SA:Vol so they need a specialised mass transport system to carry raw materials from exchange organs to body cells.
Where does the systematic circuit of the heart take the blood?
Takes blood from the heart to the body and back to the heart.
Where does the pulmonary circuit of the heart take the blood?
Takes blood from the heart to the lungs and back to the heart.
What is the blood supply for the heart muscle?
Coronary artery
What is the structure of the circulatory system?
-made up of heart and blood vessels
Where does the pulmonary artery carry blood from/to?
from: heart
to: lungs
Where does the pulmonary vein carry blood from/to?
from: lungs
to: heart
Where does the aorta carry blood from/to?
from: heart
to: body
Which blood vessel has the highest pressure?
Aorta (because it’s next to the left ventricle)
Where does the vena cava carry blood from/to?
from: body
to: heart (right atrium)
Which blood vessel has the lowest pressure?
Vena cava (furthest from left ventricle)
Where does the renal artery carry blood from/to?
from: body
to: kidneys
Where does the renal vein carry blood from/to?
from: kidneys
to: vena cava
How have the arteries been adapted?
-Thicker muscle (walls) - withstand high pressure - prevents bursting
-elastic tissue to stretch under high pressure an recoil under low pressure as the heart beats - maintains high pressure and smooths blood flow
-endothelium is smooth(in all blood vessels) - reduces friction to blood flow
-aorta specifically also has a semilunar valve to prevent backflow
What are the smaller vessels which arteries divide into called?
Arterioles.
What do the muscles inside the arterioles do?
Direct blood to different areas of demand in the body
What causes vasoconstriction and vasodilation in the arterioles?
Contraction and relaxation of the smooth muscle
What happens to reduce blood flow?
Vasoconstriction:
-smooth muscle contracts
-reduced diameter of the lumen
What happens to increase blood flow?
Vasodilation:
-smooth muscles relax
-increases diameter of lumen
True or false: the endothelium is smooth.
True
What is the movement of muscles?
Contract and relax
What is the movement of elastic tissue?
Stretch and recoil
Where do veins take blood in relation to the heart?
Take blood back INto the heart under low pressure
What are the adaptations of the veins?
-wider lumen
-very little elastic or muscular tissue -because the blood is under lower pressure,so doesn’t need them to withstand it
-contains valves to stop back-flow of blood
-blood flow is helped by muscles surrounding the veins
-walls are thin so they can easily be compressed by the muscles
What do the arterioles branch into?
Arterioles branch into capillaries with the smallest lumen, slowing rate of flow so there is more time for diffusion
How are the capillaries adapted?
-they’re adapted for diffusion by having a short diffusion pathway(endothelium is 1 cell thick) and by being very near cells
-there is a large no. of them, increasing overall SA
-small gaps/pores between cells-> increase rate if diffusion, so more fluid movement out of vessel
-red blood cells in contact with endothelium and are flexible as they have to bend to fit. This gives short diffusion pathways. Increased rate of diffusion of oxygen.
What is the function of the capillaries?
Exchange of substances
What is tissue fluid?
-fluid that surrounds cells and tissues
-made from small molecules that leave blood plasma
-doesnt contain RBC or large proteins(too large to fit through capillaries)
-substances move out of the blood by pressure filtration
How is tissue fluid formed?
-contraction of the left ventricle causes there to be a high hydrostatic pressure at the arteriole end of the capillary
-This causes water(containing useful substances such as oxygen and glucose) to be forced out of the blood into the tissue fluid
-large proteins remain in the blood(as they are too large to pass out)
What is reabsorption of tissue fluid?
-the loss of water and remaining large proteins and RBCs cause the blood to have a lower water potential then the tissue fluid
-water returns to blood via osmosis
-some water drains into the lymphatic system
What is pressure filtration?
-at the start of capillary bed, the hydrostatic pressure is higher inside the capillaries compared to the tissue fluid-due to contraction of the heart
-the difference in hydrostatic pressure forces fluid out of the capillary into the tissue fluid
-this reduces the hydrostatic pressure in the capillary at the venule end
What is the lymphatic system?
-due to fluid loss, and the retention of RBCs and other large proteins, the water potential at the venule end is lower then the water potential in the tissue fluid
-this causes some water to re-enter the capillaries by osmosis
-any excess fluid is drained into the lymphatic system which transports excess fluid from tissue fluid back into the circulatory system
What is the lymph network made of?
The lymph network consists of lymph vessels flowing alongside veins. Lymph drains into veins near the vena cava
What are the 3 functions of the lymphatic system?
-drains excess tissue fluid
-absorbs fats from the small intestine
-part of the immune system - lymph nodes are where WBC mature
