Blood Vessels And Their Functions

Question 1

what are the different types of blood vessels?

Answer 1

• arteries
• arterioles
• capillaries
• veins

Question 2

what are the arteries?

Answer 2

-they carry blood away from the heart and into arterioles

Question 3

what are the arterioles?

Answer 3

-they are smaller arteries that control blood flow from arteries to capillaries

Question 4

what are the capillaries?

Answer 4

-tiny vessels that link arterioles to veins

Question 5

what are the veins?

Answer 5

-they carry blood from capillaries back to the heart

Question 6

what are the layers of the arteries, arterioles and veins?

Answer 6

• tough fibrous outer layer that resists pressure changes from both within and outside
• muscle layer that can contract and so control the flow of blood
• elastic layer helps to maintain blood pressure by stretching and springing back
• thin inner layer that is smooth to reduce friction and thin to allow diffusion
• the lumen is not actually a layer but the central cavity of the blood vessel through which the blood flows

Question 7

what is the difference between each type of blood vessel?

Answer 7

• the relative proportions of each layer
• arterioles are not included because they are similar to arteries
• they differ from arteries in being smaller in diameter and having a relatively larger muscle layer and lumen
• the differences in structure are related to differences in the function that each type of vessel performs

Question 8

what is the structure of the artery?

Answer 8

• lumen lining
• elastic layer
• muscle layer
• tough outer layer

Question 9

what is the structure of a vein?

Answer 9

• lumen lining layer
• elastic layer
• muscle layer
• tough outer layer

Question 10

what is the structure of a capillary?

Answer 10

• lumen

- lining layer

Question 11

what is the function of the artery?

Answer 11

-the function of arteries is to transported blood rapidly under high pressure from the heart to the tissues

Question 12

how is the structure of the artery related to its function?

Answer 12

• the muscle layer is thick compared to the veins so smaller arteries can be constricted and dilated in order to control the volume of blood passing though them
• the elastic layer is relatively thick compared to veins since it is important that blood pressure in arteries is kept high if blood is to reach the extremities of the body so the elastic wall is stretched at the beat of the heart and springs back when the heart relaxed which helps to maintain high pressure and smooth pressure surges created by the beating of the heart
• the overall thickness of the wall is great which resists the vessel bursting under pressure
• there are no valves since the blood is under constant high pressure due to the heart pumping blood into the arteries so it tends not to flow backwards

Question 13

how is the structure of the arteriole related to its function?

Answer 13

• the muscle layer is relatively thicker than in arteries because the contraction of this muscle layer allows constriction of the lumen of the arteriole which restricts the flow of blood and so controls its movement into the capillaries that supply the tissues with blood
• there are no valves because blood pressure is lower

Question 14

how is the structure of a vein related to its function?

Answer 14

• the muscle layer is relatively thin compared to arteries because veins carry blood away from the tissues and therefore their constriction and dilation cannot control the flow of blood to the tissues
• the elastic layer is relatively thin compared to the arteries because the low pressure of blood within the veins will not cause them to burst and pressure is too low to create a recoil action
• the overall thickness of the wall is small because there is no need for a thick wall as the pressure within the veins is too low to create and risk of bursting to allow them to be flattened easily which aids the flow within them
• there are valves at intervals throughout to ensure that blood does not flow backwards which it may do if there is a low pressure this means that the valves only direct pressure towards the heart when the body muscles contract and the veins are compressed

Question 15

What is the function of tissue fluid?

Answer 15

-the capillaries are small but can’t serve any single cell directly so the final journey of metabolic materials is made in a liquid solution that bathes tissues

Question 16

How is the structure of capillaries related to its function?

Answer 16

• their walls consist mostly of the lining later to make them extremely thin so the distance over which diffusion she’s place is short to allow for the rapid im diffusion of materials between blood and the cells
• they are numerous and highly branched to provide a large surface area for exchange
• they have a narrow diameter so permeate tissues meaning there is a short diffusion pathway
• their lumen is narrow so red blood cells are squeezed against the side of the capillary to create a shorter diffusion pathway
• there are spaces between the lining cells that allow white blood cells to escape so they can deal with tissue infections

Question 17

What is the formation of tissue fluid?

Answer 17

• it’s a watery liquid that contains glucose, amino acids fatty acids and ions in solution and oxygen
• tissue fluid supplies all of these substances to the tissues
• tissue fluid is therefore the means by which materials are exchanged between blood and cells so it bathes all the cells of the body
• it’s the immediate environment of the cells
• tissue fluid is formed from blood plasma and the composition of blood plasma is controlled by various homeostatic systems so tissue fluid provides a mostly constant environment for the cells it surrounds

Question 18

What is hydrostatic pressure?

Answer 18

• blood pumped by the heart passes along arteries then the narrower arteriolar and the even narrower capillaries
• pumping by the heart creates a pressure called hydrostatic pressure at the arterial end of the capillaries
• hydrostatic pressure causes tissue fluid to move out of the blood plasma

Question 19

Which factors oppose hydrostatic pressure?

Answer 19

• the hydrostatic pressure of the tissue fluid outside the capillaries which resists outward movement of liquid
• the lower water potential of the blood due to the plasma proteins that causes water to move back into the blood within the capillaries

Question 20

What is ultrafiltration?

Answer 20

• a pressure is created by water potential and hydrostatic pressure which pushes tissue fluid out of the capillaries at the arterial end
• this pressure is only enough to force small molecules out of the capillaries leaving all cells and proteins in the blood because these are too large to cross the membranes

Question 21

What is the process of tissue fluid to the circulatory system?

Answer 21

• the loss of the tissue fluid from the capillaries reduces the hydrostatic pressure inside them
• this means that by the time the blood has reached the venous end of the capillary network its hydrostatic pressure is usually lower than that of the fluid outside it
• tissue fluid is forced back into the capillaries by the higher hydrostatic pressure outside them this means the plasma has lost water and still contains proteins so has a lower water potential than the tissue fluid which mess a that water leaves the tissue by osmosis down a water potential gradient m

Question 22

What happens to the tissue fluid that can’t return to the capillaries?

Answer 22

• the remainder is carried back via the lymphatic system which is a system of vessels that begin in the tissues
• initially the resemble capillaries but they gradually merge into larger vessels that form a network throughout the body
• these larger vessels drain their contents back into the bloodstream via two ducts that join veins close to the heart

Question 23

How are the contents of the lymphatic system moved?

Answer 23

• the hydrostatic pressure of the tissue fluid that has left the capillaries
• the contraction of body muscles that squeeze the lymph vessels valves in the lymph vessels ensure that the fluid inside them moves away from the tissues in the direction of the heart