2.5 The structure and function of veins, capillaries and arteries Flashcards
Identify the three different types of blood vessels that make up the circulatory system.
The circulatory system is made up of three types of blood vessels; arteries, capillaries and veins and the movement of blood through these vessels is powered by a pump called the heart.
Where does the pulmonary vein take blood.
(Circuit of the circulatory system) 1
Blood is oxygenated as it travels through the lungs. When oxygenated blood leaves the lungs, it travels in the pulmonary vein and is carried into the left atrium of the heart.
How is the oxygenated blood supplied to the body tissues
(Circuit of the circulatory system) 2
Blood then flows from the left atrium into the left ventricle and is pumped out of the left ventricle into the aorta which supplies the oxygenated blood to the body tissues.
Where does the vena cava deliver blood
(Circuit of the circulatory system) 3
The body tissues carry out respiration, using up the oxygen and producing carbon dioxide. The blood is now deoxygenated, and it is returned from the body tissues to the heart in the vena cava. The vena cava delivers blood into the right atrium.
Where does the pulmonary artery carry blood
(Circuit of the circulatory system) 4
Blood then flows from the right atrium into the right ventricle before being pumped out of the heart into the pulmonary artery. The pulmonary artery carries the deoxygenated blood up to the lungs where the blood will become oxygenated again.
where does blood circulate
Blood circulates from the heart through the arteries into the capillaries and then through the veins and back to the heart
State the function of arteries and describe the changes in pressure that occur as blood travels around the circulation system.
Arteries carry blood away from the heart under high pressure. Arteries divide into smaller and smaller blood vessels called arterioles and then capillaries.
State the function of capillaries and describe the changes in pressure that occur as blood travels around the circulation system.
The capillaries form a network that allows exchange of materials with body cells. Blood enters the capillary network under high pressure but then loses pressure so that by the time that the blood exits the capillary bed it is under low pressure.
State the function of capillaries and describe the changes in pressure that occur as blood travels around the circulation system.
Blood leaves the capillary network in small veins called venules and these join up to form bigger veins. Veins carry blood back to the heart under low press
Explain why a pulse can be felt in an artery
The elastic walls of the arteries stretch and recoil to accommodate the surge of blood that passes through the artery after each contraction of the heart. This stretch and recoil of the elastic fibres within the thick muscular walls of the artery is what is felt as a pulse.
What is the central lumen
All blood vessels have a central lumen – the area where the blood flows
The central lumen is lined by a layer of cells called the endothelium.
What is the endothelium surrounded by
In arteries and veins the endothelium is then surrounded by further layers of tissue. The outermost layer is composed of connective tissue containing elastic fibres. The middle layer contains smooth muscle with more elastic fibres.
Arteries walls are….
When compared, the arteries have much thicker muscular walls and a smaller central lumen than veins. The other major structural difference between arteries and veins is that only veins contain valves.
Capillarie structure
Capillaries allow exchange of substances with tissues.
Capillary walls are only one endothelial cell thick.
What are clefts?
Clefts / slits between the endothelial cells allow materials to pass in and out of the capillary.
Only one red blood cell at a time can fit through the central lumen of a capillary.
What is exchanged between the lumen of the capillary
Materials are exchanged between the lumen of the capillary and the tissue fluid surrounding the body cells.
Where are the valves located
Valves are found between the atria and ventricles, between the ventricles and the arteries leaving the heart and within veins
What are the function of valves
The function of valves is to prevent the backflow of blood between heartbeats.
How do valves operate
The valves are forced open when the heart beats to let the blood move forward. The valves then close when the heart relaxes to prevent the blood flowing back down the vein / into the previous chamber under the force of gravity.
How is blood flow regulates
Blood flow can be regulated using the nervous system to send nerve impulses to the smooth muscle tissue of the arteries
What is it called when the smooth muscles contact
The signals can cause the smooth muscle to contract, this is called vasocontraction and will decrease the blood flow through the artery by reducing the diameter of the lumen
What happens when the smooth muscles relax
Alternatively, the signals can cause the smooth muscle to relax, this is called vasodilation and will increase the blood flow through the artery by increasing the diameter of the lumen
What are vasoconstriction and vasodilation used for
Vasoconstriction and vasodilation are mechanisms used to redistribute blood flow to body organs during different activities and they are also used during thermoregulation.
Describe the exchange of materials between blood vessels and body cells.
Materials are exchanged between the blood capillaries and tissue fluid surrounding the body cells.
What direction does the exchange between blood vessels and body cells happen
This happens in both directions. The initial exchange of materials from the capillaries happens due to pressure filtration of the blood plasma through the capillary walls into the tissue fluid
What does the tissue fluid supply the body with?
The tissue fluid then supplies body cells with glucose, oxygen and other substances needed for cell metabolism. Carbon dioxide and other metabolic wastes diffuse out of the body cells and into the tissue fluid.
What is glucose, oxygen and other substances exchanged back into
These materials are then exchanged back into the blood plasma when tissue fluid is reabsorbed back into the blood capillaries.
State the role of lymph vessels in the circulation system
Lymphatic vessels absorb excess tissue fluid that is not reabsorbed into the capillary network. They transport their lymph fluid for eventual return to the circulatory system.
Compare the composition of blood plasma and tissue fluid.
Blood plasma and tissue fluid both carry almost the same materials e.g. glucose, O2, CO2 and amino acids. However, the main difference is that tissue fluid does not contain the plasma proteins that would be found in blood plasma. Plasma proteins are too large to move through the blood capillary walls during pressure filtration.
