blood vessels + tissue fluid

Question 1

What are arterioles? (2)

Answer 1

Arterioles branch from arteries and transport blood into capillaries

They have thinner walls, less elastic tissue, and smooth muscle to control blood flow to tissues

Question 2

What are capillaries and what is their role? (2)

Answer 2

Capillaries are the smallest blood vessels, with permeable walls that are one cell thick

They are the site of metabolic exchange between blood and cells

Question 3

What are venules? (2)

Answer 3

Blood vessels that connect capillaries to veins

They have thin walls containing muscle cells

Question 4

What are veins? (4)

Answer 4

Carry blood back to the heart under low pressure

Most carry deoxygenated blood (except pulmonary veins)

They have a wide lumen, thin walls, and valves to prevent backflow

Blood flow is aided by surrounding muscle contraction

Question 5

What is tissue fluid? (2)

Answer 5

Surrounds cells and allows the exchange of oxygen, nutrients, and waste

It does not contain red blood cells or large proteins

Question 6

How is tissue fluid formed and partially reabsorbed? (6)

Answer 6

1. Hydrostatic pressure forces fluid out of capillaries
2. The fluid forms tissue fluid around the cells
3. Hydrostatic pressure decreases as fluid leaves
4. Oncotic pressure, due to plasma proteins, lowers water potential in the capillaries
5. Water re-enters capillaries via osmosis at the venule end
6. Excess tissue fluid returns to the blood via the lymphatic system

Question 7

How does the lymphatic system return excess tissue fluid to the blood? (2)

Answer 7

1. Excess tissue fluid enters lymph capillaries, where it becomes lymph
2. Lymph moves through lymph vessels, aided by valves, and is eventually returned to the blood through vessels in the thorax

Question 8

Draw a table that shows the differences in the composition of blood, tissue fluid and lymph (6)

Answer 8

blood: red blood cells

tissue fluid + lymph have no red blood cells as they are too big to get through capillary walls

blood: white blood cells
tissue fluid: limited WBC
lymph: white blood cells

most WBC are in lymph and only enter tissue fluid when theres an infection

blood: platelets

tissue fluid + lymph have no platelets, will only be present in tissue fluid when capillaries are damaged

blood: proteins
tissue fluid: very few
lymph: antibodies only

most plasma proteins cannot fit through capillary walls

blood, tissue fluid and lymph all have water and dissolved solutes