The Circulatory System Flashcards
What is the function of the circulatory system?
This is a specialised transport system to carry raw materials from specialised exchange organs to their body cells- this is the circulatory system.
Whether or not there is a transport medium is determined by what two features?
- The activity level of the organisms.
- The surface area to volume ratio.
Pulmonary artery
Carries blood from… heart
Carries blood to… lungs
Pulmonary vein
Carries blood from… lungs
Carries blood to… heart
Aorta
Carries blood from… heart
Carries blood to… body
Vena Cava
Carries blood from… body
Carries blood to… heart
Hepatic artery
Carries blood from… body
Carries blood to… liver
Hepatic vein
Carries blood from… liver
Carries blood to… vena cava
Hepatic portal vein
Carries blood from… gut
Carries blood to… liver
Renal artery
Carries blood from… body
Carries blood to… kidneys
Renal vein
Carries blood from… kidneys
Carries blood to… vena cava
What are the characteristics of arteries?
Carry blood from heart to rest of the body.
Thick, muscular walls have elastic tissue- cope with the higher pressure from heartbeat.
Endothelium is folded to stretch and cope with high pressure.
All arteries carry oxygenated blood except for the pulmonary arteries, which take deoxygenated blood to the lungs.
What are the characteristics of arterioles?
Arteries divide into smaller vessels called arterioles.
These form a network throughout the body.
Blood is directed to different areas of demand in the body by muscles inside the arterioles, which contract to restrict the blood flow or relax to allow full body flow.
What are the characteristics of veins?
Take blood back to the heart under low pressure.
Wider lumen than arteries, with very little elastic or muscle tissue.
Veins contain valves to stop the blood flowing backwards.
Blood flow through the veins is helped by the contraction of the body muscles surrounding them.
All veins carry deoxygenated blood (used by body cells), except for the pulmonary veins, which carry oxygenated blood to the heart from the lungs.
What are capillaries?
Arterioles branch into capillaries which are the smallest of the blood vessels.
Substances like glucose and oxygen are exchanged between cells and capillaries, so they’re adapted for efficient diffusion.
Capillaries are always found very near cells in exchange tissues, so there’s a short diffusion pathway.
There are a large number to increase surface area for exchange.
What are networks of capillaries in tissue called?
Capillary beds.
What is tissue fluid?
The fluid that surrounds cells in tissues.
It’s made from substances that leave the blood, e.g oxygen, water and nutrients (e.g glucose and amino acids).
Cells taken in oxygen and nutrients from the tissue fluid, and release metabolic waste into it.
How does pressure filtration work in tissue fluid?
At the start of the capillary bed, nearest the arterioles, the hydrostatic pressure inside the capillaries is greater than the hydrostatic pressure in the tissue fluid.
This difference in hydrostatic pressure forces fluid out of the capillaries and into spaces around the cells, forming tissue fluid.
As fluid leaves, the hydrostatic pressure reduces in the capillaries- lower at the end of capillary bed nearest to veins.
Due to fluid loss, water potential at the end of the capillaries is lower than in the tissue fluid- some water re-enters the capillaries from the tissue fluid at the vein end by osmosis.
Where is any excess tissue fluid drained?
Into the lymphatic system, which transports the excess fluid from the tissues and dumps it back into the circulatory system.
Why do mammals need a mass transport system?
Mammals have a low surface area: volume ratio so they can’t rely on diffusion to exchange substances with their environment- the distance is too large.
Name two blood vessels that carry blood into the heart.
Pulmonary vein, vena cava
Which blood vessel carries deoxygenated blood to the lungs?
Pulmonary artery
What is the function of the hepatic portal vein?
To carry blood from the gut to the liver
Which blood vessel carries blood to the kidneys?
Renal artery
Which vessels supply the heart tissue with blood.
The (left and right) coronary arteries.
Name the blood vessels which have valves in them.
Veins
Give ways in which capillaries are adapted for efficient diffusion.
The walls are only one cell thick.
They’re always near the cells in exchange tissues.
There’s a large number of them in exchange tissues.
What is the basic layered structure in arteries, arterioles and veins?
Tough outer layer- that resists pressure changes from both within and outside.
Muscle layer- that can contract and so control flow of blood.
Elastic layer- that helps maintain blood pressure by stretching and springing back.
Thin inner lining (endothelium)- that is smooth to prevent friction and thin to allow diffusion.
Lumen- central cavity blood flows through.
Artery structure related to function.
Muscle layer thick compared to veins- smaller arteries can be constricted and dilated in order to control volume of blood.
Elastic layer is relatively thick compared to veins- important blood pressure is kept high if blood is to reach extremities of body.
Thickness of wall is large- resists vessel bursting under pressure.
There are no valves- because blood is under constant high pressure and therefore does not tend to flow backwards.
Arteriole structure related to function?
The muscle layer is relatively thicker than in arteries- contraction of this muscle allows constriction of lumen and control movement of blood into capillaries.
Elastic layer is relatively thinner than in arteries because blood pressure is lower.
Vein structure related to function?
Muscle layer is relatively thin compared to arteries because veins carry blood away from tissues and therefore their constriction and dilation cannot control the flow of blood to the tissues.
Elastic layer and overall thickness of wall is relatively thin because low pressure of blood within veins will not cause burst.
Valves are throughout to prevent blood flow.
What is more domineering hydrostatic pressure or osmosis?
Hydrostatic pressure
How does blood plasma differ from tissue fluid?
Tissue fluid does not contain proteins because the molecules are too large to pass through the capillary wall.
Tissue fluid is going to contain less glucose because it is being diffused into the surrounding cells for respiration.
What is hydrostatic pressure?
Pressure that results from the force of a liquid on a surface.
