Circulatory System

Question 1

Function

Answer 1

-carry raw materials from specialised exchange organs to their body cells

Question 2

Structure

Answer 2

• blood transports respiratory gases products of digestion metabolic wastes and hormones around body in 2 circuits
• 1 circuit takes blood from heart to lungs then back to heart
• other circuit takes blood round rest of body so blood has to go through heart twice to complete one full circuit of the body
• heart own blood supply with left and right coronary arteries

Question 3

Arteries

Answer 3

• from heart to rest of body
• walls thick and muscular and have elastic tissue to stretch and recoil as the heart beats which helps maintain the high pressure
• inner lining called endothelium is folded allowing artery to stretch so helps maintain high pressure
• all carry oxygenated blood except pulmonary vein which take deoxygenated blood to lungs

Question 4

Arterioles

Answer 4

• arteries divide into smaller vessels
• form network throughout the body
• blood directed to dif areas of demand in body by muscles inside arterioles which contract to restrict blood flow or relax to allow blood flow

Question 5

veins

Answer 5

• take blood back to heart under low pressure
• larger lumen than equivalent arteries so very little elastic or muscle tissue
• contain valves to stop blood flowing backwards
• blood flow through veins helped by contraction of body muscles surrounding
• all carry deoxygenated blood except pulmonary veins carry oxygenated blood to heart from lungs

Question 6

Capillaries

Answer 6

• arterioles branch into capillaries
• smallest of blood vessels
• substances exchanged between cells and capillaries
• adapted for efficient diffusion
• found very near cells in exchange tissue which makes it have a short diffusion pathway
• large number increases SA for exchange
• network of capillaries = capillary beds

Question 7

Tissue Fluid

Answer 7

• fluid that surrounds cells in tissue made from small molecules that leave the blood plasma like oxygen water and nutrients
• cells take in oxygen and nutrients from tissue fluid and release metabolic waste into it
• substances move out of the capillaries into the tissue fluid by pressure filtration

Question 8

Tissue Fluid Process

Answer 8

• at start of capillary bed nearest the arteries the hydrostatic pressure inside the capillaries is greater than in tissue fluid
• difference in hydrostatic pressure means overall outward pressure forces fluid out of the capillaries and into the space around the cells forming tissue fluid
• as fluid leaves hydrostatic pressure reduces in capillaries so this means hp much lower at venule
• due to fluid loss and increasing concentration of plasma proteins WP at venule end of capillary bed is lower than wp in tissue fluid
• water re-enters capillaries from tissue fluid at the venule end by osmosis
• excess tissue fluid drained into lymphatic system

Question 9

venule

Answer 9

• end of capillary bed

- end nearest to veins

Question 10

Lymphatic system

Answer 10

-network of tubes that act like a drain that transports excess fluid from tissues and passes it back into circulatory system