3.1.2 - Transport In Animals (set A - Circulatory Systems And Blood Vessels)

Question 1

Outline the need for specialised transport systems - give 4 reasons?

Answer 1

• metabolic demands are high - require lots of substances and produce lots of waste products
• SA:V ratio gets smaller - diffusion distances get bigger and the surface area for substances to exchange across decreases
• transport of hormones or enzymes to other sites
• waste products need to be removed from cells and transported to excretory organs

Question 2

Explain the main features of most circulatory systems?

Answer 2

• have a liquid transport medium that circulates around the system
• have vessels that carry the transport medium
• have a pumping mechanism to move fluid around the system

Question 3

Definite what a mass transport system is?

Answer 3

When substances are transported in a mass of fluid with a mechanism for moving the fluid around the body

• multicellular animials have either an open or closed system

Question 4

Outline main features of an open circulatory system?

Answer 4

• very few vessels to contain transport medium
• pumped straight from heart into body cavity (haemocoel)
• transport medium in haemocoel is under low pressure - comes into direct contact with tissue and cells
• transport medium returns to heart through open-ended vessel

Question 5

Briefly describe an open circulatory system?

Answer 5

Transport medium pumped straight from heart into haemocoel where its under low pressure and exchanges gases directly with the tissues and cells

Question 6

Explain what the haemocoel is?

Answer 6

The open body cavity of the animal which the transport medium is directly pumped into

• transport medium under low pressure

Question 7

Outline the type of circulatory system preset in most insects - explain the features?

Answer 7

• open circulatory system
• blood called haemolymph (doesn’t carry oxygen or carbon dioxide - transports food and nitrogenous waste products)
• haemocoel split by membrane - heart extends along length of thorax and abdomen

Question 8

Explain the function of haemolymph?

Answer 8

Transport medium of most insects - doesn’t carry oxygen or carbon dioxide - transports food and nitrogenous waste products

• also contains cells involved in fighting diseases

Question 9

Explain a problem with open circulatory systems?

Answer 9

• Haemolymph circulates however steep concentration gradient cannot be maintained - prevents efficient diffusion
• amount of haemolymph flowing to particular tissues can not be varied to meet changing demands

Question 10

Outline the main features of a closed circulatory system?

Answer 10

• blood enclosed in vessels - doesn’t directly come into contact with cells
• heart pumps blood under pressure around body
• substances diffuses in and out of the vessel walls
• blood flow to particular tissues can be adjusted

Question 11

Briefly explain a closed circulatory system?

Answer 11

Blood is enclosed within vessels and is pumped around the body under pressure - substances diffuse in and out of the blood through the vessel walls

• blood pigment carries respiratory gases

Question 12

Outline an important advantage of closed circulatory systems?

Answer 12

Blood flow to particular tissues can be adjusted by widening or narrowing blood vessels

Question 13

Briefly outline what single circulatory systems are?

Answer 13

Blood flows through heart and is pumped around body before returning to the heart (travels once through heart for each complete circulation of the body)

Question 14

Outline the features of a single circulatory system?

Answer 14

• blood passes through 2 sets of capillaries before retuning to heart
• first capillary it exchanges O2 and CO2 - second set of capillaries, substances are exchanged between blood an the cells
• blood returns to heart slowly due to very narrow vessels

Question 15

Explain why single circulatory systems are often found in low activity animals?

Answer 15

Blood pressure in the system drops considerably due to blood passing through two sets of very narrow vessels - blood returns to heart quite slowly

• limits efficiency of exchange processes

Question 16

Explain why some active animals like fish are able to have a single circulatory system?

Answer 16

Have very efficient system - due to countercurrent gas exchange in the gills, allowing the removal of lots of O2 from water

• body weight is supported by the water and they do not have to maintain body temperature (reduces metabolic demands)

Question 17

Outline what a double circulatory system is?

Answer 17

Most efficient system for transporting substances around the body - blood travels twice through the heart for each circuit of the body

• each circuit - to the lungs and to the body only pass through one capillary network

Question 18

Explain how high pressure is maintained in a double circulatory system?

Answer 18

Each circuit - to the lungs and to the body - only passes through one capillary network, which allows a relatively high pressure and fast flow of blood to be maintained

Question 19

Explain the main features of a double circulatory system?

Answer 19

• blood is pumped from heart to lungs to pick up O2 and unload CO2, then returns to heart
• blood flows through the heart and is pumped out to travel around the body before returning to the heart again

Question 20

Explain the role of elastic fibres in vessels, give brief structure?

Answer 20

Composed of elastin - can stretch and recoil providing vessel walls with flexibility

Question 21

Explain the role of smooth muscle in vessels?

Answer 21

Contracts or relaxes which changes the size of the lumen - controls blood flow

Question 22

Explain the role of collagen in vessels?

Answer 22

Provides structural support to maintain the shape and volume of the vessel

Question 23

Outline the main features of arteries?

Answer 23

• contain elastic fibres, smooth muscle and collagen
• elastic fibres help even out surges of blood
• blood transported under high pressure
• endothelium lining is smooth for easy blood flow
• Carry oxygenated blood

Question 24

Outline the importance of elastic fibres in arteries?

Answer 24

• enables vessel to stretch to withstand force of blood as its pumped from the heart, and increase blood volume - collagen prevents overstretching
• recoil and return to original length between contractions of the heart - evening out surges of blood, gives a continuous flow

Question 25

Outline and explain 3 adaptions arteries have?

Answer 25

• smooth endothelium - allows for easy blood flow
• elastic fibres which allowing vessel to stretch to increase blood flow and maintain pressure + evens out surges allowing for continuous flow
• collagen prevents elastic fibres from overstretching

Question 26

Outline what arterioles are - give brief structure?

Answer 26

Vessels which link arteries and capillaries

• smooth muscle and less elastin (little pulse surge) in walls
• smooth muscles allows constriction and dilation to control blood flow to individual organs

Question 27

Explain why arterioles have less elastic fibres but more smooth muscle than arteries?

Answer 27

• Have little pulse surge, so do not need much elastic fibre to recoil and relax to even out surges
• have more smooth muscle to control blood flow - contracts to constrict vessel (vasoconstriction) and relax to dilate vessel (vasodilation)

Question 28

Outline what capillaries are - give brief structure?

Answer 28

Extremely small blood vessels that link arterioles with the venules by forming an extensive network through tissues

• lumen is narrow enough that RBCs move in single file
• large gaps between endothelial cells in the walls

Question 29

Explain the significance of gaps within capillary walls?

Answer 29

Large gaps between endothelial cells that make up capillary walls allow movement of substances into surrounding cells

Question 30

Outline an explain 3 ways capillary’s are adapted for their role?

Answer 30

• provide a very large SA for diffusion of substances in and out
• total cross-sectional area of capillaries is greater than arteriole supplying them - rate of blood flow falls, increasing time for diffusion
• walls are single endothelial cell thick - short diffusion path

Question 31

Why is the cross-sectional area of capillaries being larger than supplying arteriole important?

Answer 31

Results in the rate of blood flow falling - slower movement of blood through capillaries allows for more time for the exchange of substance by diffusion between blood and the cells

Question 32

Outline what veins are - give brief structure?

Answer 32

Carry deoxygenated blood at low pressure from cells towards heart - join to form 2 main vessels (inferior vena cava and superior vena cava)

• walls contain lots of collagen, relatively little elastic fibre
• wide lumen and smooth, thin endothelium

Question 33

Outline what venules are and the role they play - give brief structure?

Answer 33

Link capillaries with the veins - several join together to form vein

• have very thin walls and little smooth muscle

Question 34

Explain why veins do not have a pulse?

Answer 34

Surfers from the heart pumping are lost - due to blood passing through narrow capillaries

• do however hold larger reservoir of blood - 60%

Question 35

Give the features of veins?

Answer 35

• blood pressure is low compared to arteries
• valves to prevent back flow of blood
• walls contain lots of collagen, relatively little elastic fibres
• wide lumen - higher blood volume
• smooth endothelium - easy blood flow

Question 36

Explain 3 ways veins are adapted to return blood whilst under low pressure?

Answer 36

• contain one-way valves which open so blood can pass through and close if blood starts flowing backwards
• bigger veins run between big, active muscles which force blood towards the heart
• breathing movements of the chest act as a pump

Question 37

Outline how breathing movements of the chest helps veins transport deoxygenated blood to the heart?

Answer 37

Acts as a pump - the pressure changes and squeezing action moves blood in the veins of the chest and abdomen towards the heart

Question 38

Outline how veins running between major muscles helps them return deoxygenated blood to the heart?

Answer 38

Veins run between big, active muscles - when they contract they squeeze the veins, which forces the blood towards the heart

• valves then prevent back flow when the muscles relax

Question 39

Which type of veins contain valves?

Answer 39

Medium-sized veins (majority of the venous system)- have valves

Question 40

Explain the two exceptions of type of blood carried by arteries?

Answer 40

Carry oxygenated blood from the heart to tissues of body - except the pulmonary artery which carries deoxygenated blood from the heart to the lungs

• umbilical artery during pregnancy carries deoxygenated blood from fetus

Question 41

Explain the two exceptions of type of blood carried by veins?

Answer 41

Carry deoxygenated blood from the tissues to the heart - except the pulmonary vein which caries oxygenated blood from the lungs to the heart

• umbilical vein - carries deoxygenated blood from the placenta

Question 42

How are arteries adapted for withstanding high pressure?

Answer 42

Thick muscular walls - contain lots of collagen and elastic fibres

Question 43

Explain why veins have thin walls?

Answer 43

Transport blood at lower pressure - have less muscular and elastic tissue