E&T: Circulatory System COPY Flashcards
What do arteries transport?
Oxygenated blood from the heart to the rest of the body.
Apart from pulmonary artery which takes deoxygenated blood to lungs.
What are 3 characteristics of arteries?
- Thick, muscuar walls
- Elastic tissue to stretch + recoil as the heart beats
- Folded endothelium = allows stretch
Why is it useful that the walls of arteries can stretch and recoil?
To help them maintain the high blood pressure.
What do arteries divide into?
Arterioles
What is the role of arterioles?
Direct blood to different areas of deman in the body by muscles inside arterioles.
What do veins transport?
Deoxygenated blood back to the heart under low pressure.
Apart from the pulmonary veins which carry oxygenated blood from the heart to the lungs.
What are 2 characteristics of veins?
- Wider lumen
- Very little elastic/muscle tissue
Blood flow through the veins is helped by what?
Contraction of surrounding body muscles.
What do arterioles branch into?
Capillaries
How are capillaries adapted for efficient diffusion?
- Found very near cells in exchange tissues = short diffusion pathway
- Only one cell thick = short diffusion pathway
- Large number = increased surface area
What is tissue fluid made from?
Small molecules that leave the blood plasma, eg. oxygen, water and nutrients.
Why doesn’t tissue fluid contain red blood cells or big proteins?
Too large to push out of capillary walls.
What do cells take from tissue fluid?
What do they release into it?
Take = oxygen + nutrients
Release = metabolic waste
How do substances move out of capillaries by pressure filtration?
- Arteriol end = hydrostatic pressure inside capillaries is greater than tissue fluid.
- Overall outward pressure forces fluid out of capillaries, forming tissue fluid.
- Fluid leaving reduces hydrostatic pressure in capillaries at venule end.
- Fluid loss + increases conc. of plasma proteins lowers water potential at venule end of capillary.
- Water re-enters from the tissue fluid at venule end by osmosis.
What happens to excess tissue fluid?
Drained into lymphatic system, which transports excess from tissues and puts back into circulatory system.
