Mass Transport in Animals - A5

Question 1

Why have a circulatory system?

Answer 1

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.

Question 2

Where does the systematic circuit of the heart take the blood?

Answer 2

Takes blood from the heart to the body and back to the heart.

Question 3

Where does the pulmonary circuit of the heart take the blood?

Answer 3

Takes blood from the heart to the lungs and back to the heart.

Question 4

What is the blood supply for the heart muscle?

Answer 4

Coronary artery

Question 5

What is the structure of the circulatory system?

Answer 5

-made up of heart and blood vessels

Question 6

Where does the pulmonary artery carry blood from/to?

Answer 6

from: heart
to: lungs

Question 7

Where does the pulmonary vein carry blood from/to?

Answer 7

from: lungs
to: heart

Question 8

Where does the aorta carry blood from/to?

Answer 8

from: heart
to: body

Question 9

Which blood vessel has the highest pressure?

Answer 9

Aorta (because it’s next to the left ventricle)

Question 10

Where does the vena cava carry blood from/to?

Answer 10

from: body
to: heart (right atrium)

Question 11

Which blood vessel has the lowest pressure?

Answer 11

Vena cava (furthest from left ventricle)

Question 12

Where does the renal artery carry blood from/to?

Answer 12

from: body
to: kidneys

Question 13

Where does the renal vein carry blood from/to?

Answer 13

from: kidneys
to: vena cava

Question 14

How have the arteries been adapted?

Answer 14

-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

Question 15

What are the smaller vessels which arteries divide into called?

Answer 15

Arterioles.

Question 16

What do the muscles inside the arterioles do?

Answer 16

Direct blood to different areas of demand in the body

Question 17

What causes vasoconstriction and vasodilation in the arterioles?

Answer 17

Contraction and relaxation of the smooth muscle

Question 18

What happens to reduce blood flow?

Answer 18

Vasoconstriction:
-smooth muscle contracts
-reduced diameter of the lumen

Question 19

What happens to increase blood flow?

Answer 19

Vasodilation:
-smooth muscles relax
-increases diameter of lumen

Question 20

True or false: the endothelium is smooth.

Answer 20

True

Question 21

What is the movement of muscles?

Answer 21

Contract and relax

Question 22

What is the movement of elastic tissue?

Answer 22

Stretch and recoil

Question 23

Where do veins take blood in relation to the heart?

Answer 23

Take blood back INto the heart under low pressure

Question 24

What are the adaptations of the veins?

Answer 24

-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

Question 25

What do the arterioles branch into?

Answer 25

Arterioles branch into capillaries with the smallest lumen, slowing rate of flow so there is more time for diffusion

Question 26

How are the capillaries adapted?

Answer 26

-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.

Question 27

What is the function of the capillaries?

Answer 27

Exchange of substances

Question 28

What is tissue fluid?

Answer 28

-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

Question 29

How is tissue fluid formed?

Answer 29

-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)

Question 30

What is reabsorption of tissue fluid?

Answer 30

-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

Question 31

What is pressure filtration?

Answer 31

-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

Question 32

What is the lymphatic system?

Answer 32

-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

Question 33

What is the lymph network made of?

Answer 33

The lymph network consists of lymph vessels flowing alongside veins. Lymph drains into veins near the vena cava

Question 34

What are the 3 functions of the lymphatic system?

Answer 34

-drains excess tissue fluid
-absorbs fats from the small intestine
-part of the immune system - lymph nodes are where WBC mature