Circulatory System Flashcards
Why do big mammals need a transport system
Low SA:V
Give 2 things blood transports
Hormones
O2/CO2
Give 3 ways arteries are adapted for their function
Thick muscular walls
Elastic tissue
Folded endothelium
How does a does thick muscular walls help the arteries
Maintain high p
How does elastic tissue help arteries
Allow to stretch and recoil at every heart beat to maintain high p
Why is a folded endothelium useful for arteries
Allows it to stretch to maintain high p
Give 3 ways veins are adapted for their function
Wide lumen
Very little elastic or muscle tissue
Valves
Explain how a wide lumen is goof for veins
Stop any résistance to blood flow
Explain why veins have little muscle or elastic tissue
Blood not under high p
Explain why veins have valves
Prevent back flow of blood
As it’s under low p
How do surrounding muscles help blood flow back to the heart
Blood in VEINS under low p
So surrounding body muscle contract to push the blood
What is the function of artérioles
Directs blood to certain areas by muscles inside arterioles. Contract = restrict flow
Give 3 ways capillaries are adapted for their function and why
Very near cells in exchange tissues = short diffusion pathway
Walls only 1 cell thick = short diffusion pathway
Large numbers = increase SA
What is a capillary bed
Networks of capillaries in tissue
What is tissue fluid
Fluid that surrounds cells
Made of small molecules that leave blood plasma eg. Water/O2
Why does tissue not contain red blood cells or big proteins
Too large to be pushed out of capillary walls
Explain pressure filtration
- At artériole end: higher hydrostatic pressure in Capillaries than tissue fluid
- Pushes fluid out of capillaries into spaces around cells
- Hydrostatic p in capillaries decreases at venule end
- Because fluid has left. The conc of plasma protein increases inside the capillary
- Lower water potential in capillary than tissue fluid
- Water moves into capillary by osmosis down water potential grad
Where does excess tissue fluid go
Drains into the lymphatic system
Why does water renter capillaries at the venule end
The water potential is lower in the capillary than In the tissue fluid. Because large plasma proteins can’t leave the capillary so their conc increases
Why does fluid move out of the capillary at the arteriole end
The capillary has a higher hydrostatic pressure than the tissue fluid forcing fluid out down the p grad
Why can high p be bad in relation to tissue fluid
High hydrostatic pressure forces out more tissue fluid. So it accumulates more
Where are the atrioventricular valves
Between atria and ventricles
Where are the semi lunar valves
Between the ventricles and the aorta/pulmonary artery
What is the function of cords in the heart
Attach atrioventricular valves to the ventricles
Stop them being forced up into the atria when the ventricles contract
When will a valve open
High pressure behind it
Why do valves only work in 1 direction
Blood can only flow in 1 direction
Give the 3 stages of the cardiac cycle
- Atria systole
- Ventricular systole
- Diastole
Explain atria systole
Atria volume decrease
Atria p increase
Pushes blood into ventricles
Slight Increase in ventricular pressure and volume as blood is received
Explain ventricular systole
Ventricle volume decrease Ventricle p increase P higher in ventricles than atria AV valves close P is higher in ventricles than aorta/pulm artery SL valve opens Blood enters aorta/pulm artery
Explain diastole
Higher p in aorta/pulm artery than ventricles
SL valves shut
Blood returns to heart
High p in vena cava/pulm vein than atria
Atria fill
Atria p higher than ventricles
AV valves open
What does passive blood flow mean
Not pushed by contraction
Eg. In atria to the ventricles during diastole
