Circulatory System of a Mammal (Exchange and Transport) (UNIT2)

Question 1

Why do large organisms need a transport system?

Answer 1

With increasing size, the surface area to volume ratio decreases to a point where the needs of the organism cannot be met by the body surface alone. Specialised exchange surface needed.

Question 2

What is the job of a transport system?

Answer 2

To absorb nutrients and respiratory gases and to remove excretory products. Take materials from cells to exchange surfaces and vice versa. MAterials have to be transported between exchange surfaces and environment. Also between different parts of organism.

Question 3

What two factors does the presence of a specialised transport system depend on?

Answer 3

• SA:vol ratio
• How active organism is.

Lower SA:vol ratio and more active, more need for exchange system.

Question 4

What are the 6 features of a transport system?

Answer 4

• Suitable medium to carry materials (blood) normally a liquid based on water- water readily dissolves substances.
• Form of mass transport in which transport medium is moved around in bulk over large distances.
• Closed system of tubular vessels containing transport medium and forms branching network.
• A mechanism for moving transport medium within vessels.

REQUIRES PRESSURE DIFFERENCE BETWEEN ONE PART OF SYSTEM AND ANOTHER.

2 ways:

+Muscular contraction either of body muscles or specialised organ.

+Plants use passive natural physical processes such as evaporation.

• Mechanism to maintain mass flow movement in ONE DIRECTION (valves)
• Means of controlling flow to suit changing needs of organism.

Question 5

Outline the transport system in mammals.

Answer 5

Closed blood system, confined to vessels.

Heart (muscular pump) circulates blood.

DOUBLE CIRCULATORY SYSTEM.

Blood passes twice through heart for each complete circuit of body.

Question 6

Why do mammals have a double circulatory system?

Answer 6

When blood passes through lungs, pressure is reduced. If was to pass straight to rest of body its low pressure would make circulation slow. Returned to heart to boost pressure. Substances delivered to rest of body quicker.

Question 7

Why do mammals need substances delivered quickly?

Answer 7

High temperature so high rate of metabolism.

Question 8

What are the three types of vessels in mammals circulatory system>

Answer 8

Arteries, veins capillaries.

Question 9

What s the final journey of substances into the body and why is it rapid?

Answer 9

Into cells by diffusion. Large SA, short distance and steep diffusion gradient so rapid.

Question 10

Leaving the aorta, what journey does blood take back?

Answer 10

OXYGENATED:

UP TO: head and neck

Upper limbs

DOWN TO: Hepatic arteries->LIVER

Stomach and intestines->hepatic portal vein->liver Renal artery->Kidneys

Lower limbs

DEOXYGENATED

DOWN TO:

Head and neck and upper limbs-> vena cava

UP TO:

Liver-> Hepatic vein->vena cava

Kidneys->renal vein->vena cava

Lower limbs->vena cava

VENA CAVA-> Right atrium->Right ventricle->Pulmonary artery->LUNGS->Pulmonary vein-> Left atrium->Left ventricle->AORTA

Question 11

Arteries

Answer 11

carry blood away from heart and into arterioles.

Question 12

Arterioles

Answer 12

Smaller arteries that control blood flow from arteries to capillaries.

Question 13

Capillaries

Answer 13

Tiny vessels that link arterioles to veins

Question 14

Veins

Answer 14

Carry blood from capillaries back to heart

Question 15

Layers of arteries, arterioles and veins. (5)

Answer 15

• Tough outer layer- resists pressure changes from both within and outside
• Muscle layer- can contract and so control the flow of blood
• Elastic layer- helps to maintain blood pressure by stretching and springing back
• Thin inner lining (ENDOTHELIUM)- smooth to prevent friction and thin to allow diffusion.
• Lumen- not actually a layer but the central cavity of the blood vessel through which blood flows.

Question 16

ARTERY SPECIFIC STRUCTURE

Answer 16

Narrow lumen

ENDOTHELIUM THICK

ELASTIC LAYER THICK

MUSCLE LAYER THICK

TOUGH OUTER LAYER

Question 17

VEIN SPECIFIC STRUCTURE

Answer 17

WIDE LUMEN

ENDOTHELIUM THIN

ELASTIC LAYER MEDIUM

MUSCLE LAYER

TOUGH OUTER LAYER

Question 18

CAPILLARY SPECIFIC STRUCTURE

Answer 18

Narrow lumen

ONLY ENDOTHELIUM

Question 19

Structure of artery related to function (4)

Answer 19

-Muscle layer thick compared to veins:

constricted and dilated in order to control the volume of blood passing through them.

-Elastic layer is relatively thick compared to veins- important that blood pressure in arteries is kept high for blood to reach extremities of body.

Stretched (systole.

Springs back (diastole).- helps maintain high pressure and smooth pressure surges created by beating of heart.

• Overall thickness of wall is large- resists vessel bursting under pressure.
• No valves (except leaving heart)- constant high pressure and therefore does not tend to flow backwards.

Question 20

Function of artery

Answer 20

Transport blood rapidly under high pressure from the heart to tissues.

Question 21

Function of arteriole.

Answer 21

carry blood, under lower pressure than arteries, from arteries to capillaries. Also control blood flow between two .

Question 22

Structure of arteriole related to function. (2)

Answer 22

• The muscle layer is relatively thicker than in arteries- contraction allows constriction of lumen of the arteriole.

Restricts flow of blood and so controls its movement into the capillaries that supply the tissues with blood.

-Elastic layer is relatively thinner than in arteries- blood pressure lower.

Question 23

Function of vein

Answer 23

Transport blood slowly, under low pressure, from tissues to the heart.

Question 24

Structure of vein related to function. (4)

Answer 24

• Muscle layer relatively thin compared to arteries- veins carry blood away from tissues so constriction and dilation cannot control the flow of blood to the tissues.
• Elastic layer relatively thin compared to arteries- low pressure so won’t burst, and too low for recoil action
• Overall thickness of wall small- no need for thick wall as no risk of bursting. Allows them to be flattened easily, aiding flow of blood between them.
• valves throughout- Ensure blood does not flow backwards. One way.

Question 25

Function of capillary

Answer 25

Exchange metabolic material such as oxygen, carbon dioxide and glucose between blood and cells. Slow flow to allow time for exchange of materials.

Question 26

Structure of capillaries related to function. (5)

Answer 26

Walls consist only of lining layer- extremely thin, short diffusion pathway, rapid diffusion between blood and cells.

• Numerous and highly branched
• large SA
• Narrow diameter- permeate tissues, no cell far from a capillary
• Narrow lumen- red blood cells squeezed flat against side of capillary. Brings them even closer to the cells to which they supply O2. Reduces diffusion distance.
• There are spaces between lining (endothelial) cells that allow white blood cells to escape in order to deal with infections within tissues.

Question 27

What is the final journey of metabolic materials?

Answer 27

Tissue fluid.

Question 28

What is tissue fluid?

Answer 28

Watery liquid that contains glucose, amino acids, fatty acids, salts and oxygen. Tissue fluid supplies all of these substances to the tissues. In return, it receives CO2 and other waste materials from the tissues. Bathes all cells in body.

Question 29

What is tissue fluid formed from?

Answer 29

From blood plasma, and composition of blood plasma is controlled by various homeostatic systems.

Question 30

What is the path taken by blood from the heart? Vessels (simple)

Answer 30

Arteries- narrrower arterioles- even narrower capillaries

Question 31

Hydrostatic pressure. Where is it created?

Answer 31

Pressure created by the blood on its path from the heart to capillaries. At arterial end of capillaries

Question 32

What is the outwards pressure in vessels that forces tissue fluid out of blood plasma opposed by? (2)

Answer 32

-hydrostatic pressure of the tissue fluid outsidethe capillaries, which prevents outwards movement of liquid -the lower water potential of the blood, due to plasma proteins, that pulls water back into the blood within capillaries

Question 33

Ultrafiltration

Answer 33

Filtration under pressure- Outwards pressure only enough to force small molecules out of capillaries, leaving all cells and protein in the blood.

Question 34

How does tissue fluid return to blood plasma?

Answer 34

• Loss of tissue fluid from the capillaries reduces the hydrostatic pressure inside them.
• As a result, by the time blood has reached the venous end of the capillary network its hydrostatic pressure is less that that of the tissue fluid outside it.
• Tissue fluid forced back into capillaries by the higher hydrostatic pressure outside them
• In addition, the osmotic forces resulting from the proteins the blood plasma pull water back into capillaries. `

Question 35

How is the remainder of tissue fluid be carried back?

Answer 35

Via lymphatic system

Question 36

Lymphatic system

Answer 36

System of vessels that begin in the tissues. Initially they resemble capillaries, but they gradually merge into larger vessels that form network throughout body. Larger vessels drain their contents back into the bloodstream via two ducts that join veins close to the heart.

Question 37

How are the contents of the lymphatic system moved?

Answer 37

Hydrostatic Pressure of tissue fluid that has left capillaries. Contraction of body muscles that squeeze lymph vessels- valves ensure move in correct direction.