Blood Vessels

1. Arteries
Carry blood away from heart

2. Blood Capillaries
Exchange materials with tissues

3. Veins
Carry blood back INTO the heart

Blood Flow
Blood always flow out & back into the heart in the following order.

Arteries

Blood leaves the heart at high pressure & a pulse can be felt.

Structural adaptations

1. thicker wall

2. thicker muscle layer

3. narrower central channel

4. no valves

Veins

Blood returns to the heart at low pressure & no pulse is felt.

Structural adaptations

1. thinner wall

2. thinner muscle layer

3. wider central channel

4. valves to prevent backflow of blood.

Structural adaptations

1. thinnest wall

2. large surface area

3. highly branched forming networks

Form networks at issues to exchange materials as in close contact with tissues.

Gas Exchange at tissues

O2 + nutrients moves from blood capillary cells/tissues for aerobic respiration.

CO2 moves from the cells/ tissue blood capillary to be removed from body.