Chapter 6.1 Transport systems in mammals

Question 1

Explain why mammals needs a circulatory system

Answer 1

• SA:vol too small to meet demands by diffusion alone
• Also have higher metabolic rate -> greater demand
• Also very active hence they have a greater number of cells respiring very quickly so need a greater and faster supply of O2 and greater and faster removal of waste products (CO2, lactic acid, heat)

Hence need specialist exchange surface and mass transport system = circulatory system in mammals

Question 2

State the benefits of a closed circulatory system

Answer 2

blood always moves within a vessel

blood pressure can be maintained

supply to organs can differ depending on function and need

lower volumes of blood volumes

Question 3

State the benefit of a double circulatory system

Answer 3

pulmonary + systemic circuits are separated

pressure can be maintained separately

blood does not mix ∴ oxygen/nutrient uptake at exchange site is more efficient

Question 4

List the layers of an artery’s wall (start from the lumen and work outwards)

Answer 4

lumen

tunica intima

endothelium

internal elastic lastima

tunica media

external elastic lastima

tunica externa

vasa vasorum

Question 5

State the function of elastic fibres in arteries

Answer 5

allow arteries to expand and recoil during ventricular systole

this enables BP changes to be regulated

Remember: do not say contract and relax as elastic fibres can only stretch and recoil

Question 6

State the function of smooth muscle in the artery walls

Answer 6

contract –> forces blood through at high pressure

can change the size of the lumen

this reduces resistance to blood flow

Question 7

List the layers of a vein’s walls(start form the lumen and work outwards)

Answer 7

lumen

tunica intima

endothelium

tunica media

tunica externa

vasa vasorum

Question 8

Describe how blood is moved in veins

Answer 8

Contraction of skeletal muscles
 compresses veins
 increases BP within veins
 helps ensure blood returned to heart
 without this the BP would be too low to overcome force of gravity
 this would lead to blood pooling
 leading to an increase in the risk of clots forming
 increasing risk of DVT  increased risk of stroke or heart attack

When skeletal muscles relax
 decompresses veins
 BP falls in veins
 more blood flows from capillary beds through valves into veins

Question 9

Describe the structure of the capillary walls

Answer 9

Made of squamous endothelium
Smooth surface (reduces resistance to blood flow)
Walls are one cell thick

Question 10

Define systolic pressure

Answer 10

the pressure in the arteries as blood is forced out of the left ventricle during systole

Question 11

Define diastolic pressure

Answer 11

the pressure during diastole

Question 12

State how BP can be measured

Answer 12

sphygmomanometer

 Measures BP in kPa
 Previous units = mmHg (typical BP = 120/80mmHg)
 Can be electronic or manual sphygmomanometers (which are used in conjunction with a stethoscope)
 Consists of composed of an inflatable cuff to collapse and then release the artery under the cuff in a controlled manner and a mercury or mechanical manometer to measure the pressure

Question 13

Describe how is blood pressure measured

Answer 13

• Ensure person is sat down for 5-10 minutes in calm area
• Person must sit still with arm supported on table and not talk
• Person is advised not to look at the monitor (if electronic) or mercury column (if manual)
• BP is usually taken using the left arm (closest to heart)
• Cuff is attached to upper arm (above elbow) securely
• Cuff is inflated (manually or by electronic pump)
• Builds up pressure on brachial artery and eventually stops blood flow in this artery
• With the aid of a stethoscope placed under the cuff the medical practitioner listens for sounds of blood flow returning as the cuff is slowly and gradually deflated
• First sounds heard = Krokoff sounds (occur as soon as BP in brachial artery = systolic pressure)
• When Krokoff sounds disappear the BP in brachial artery = diastolic pressure

Question 14

Define hypertension

Answer 14

Persistently high blood pressure

 At a clinic BP of 140/90 mmHg
 At home BP of 135/85mm Hg

Question 15

State 4 risk factors that contribute to hypertension

Answer 15

 smoking
 obesity
 high salt intake
 excessive alcohol consumption
 high stress levels
 increasing age
 post-menopausal drop in oestrogen
 biological sex: males are higher risk (do not say gender here)
 sedentary lifestyle

Question 16

Describe the health risks associated with hypertension

Answer 16

damage to artery walls –> aneurysm/blood clot

damage to heart valves

kidney disease

Question 17

State the health risks associated with hypotension

Answer 17

 weakness & tiredness
 dizziness & fainting
 coma

potentially fatal :(

Question 18

Describe the tissue fluid

Answer 18

fluid that surrounds the cells of the body

Question 19

State the function of tissue fluid

Answer 19

to supply cells with nutrients and to remove waste products

exchange of materials at capillaries

Question 20

Describe how tissue fluid is formed

Answer 20

high hydrostatic pressure at arteriole end of capillaries

water and other soluble materials forced out of the blood plasma

plasma proteins too large to diffuse into tissue fluid ∴ they exert negative oncotic pressure on capillary walls which draws water in by osmosis

Question 21

Describe lymph

Answer 21

similar to tissue fluid but more leucocytes

Question 22

Describe the function of lymph?

Answer 22

important in immune response - nodes are site for filtration of pathogens/foreign bodies

Question 23

Define a closed circulatory system

Answer 23

Blood always moves within blood vessels  allows pressure to be maintained

Question 24

Describe a double circulatory system

Answer 24

Nlood passes through the heart twice per complete circuit round the body
two circulatory systems exist:
a) Pulmonary circuit (PC) – blood travels from RV to lungs to LA
b) Systemic circuit (SC) – blood travels from LV to rest of the body to RA

Question 25

State the advantages of a DCS

Answer 25

BP can be maintained (BP will naturally fall as distance from heart increases due to surface of blood vessels generating resistance to blood flow)
Oxygenated blood is not mixed with deoxygenated blood  increases efficiency of O2 uptake at alveoli
Increased efficiency in delivering O2 and glc etc to tissues
BP in systemic and pulmonary circuits can be maintained at different levels (if there was only a single circuit then a high BP would cause alveoli walls to rupture whereas a low BP would not be high enough to enable O2 etc to be delivered at a rate that would meet demand)

Question 26

State the advantages of a closed circulatory system

Answer 26

BP can be maintained all through body
BP in PC and SC can be different
Blood supply can be varied between organs to match their specific metabolic demands e.g. increase delivery to skeletal muscles during exercise, increase delivery to small intestine during digestion
Lower volumes of blood required (compared to if blood was allowed to bathe all cells i.e. fill the spaces occupied by TF)

Question 27

Complete the table

Answer 27

Question 28

State the tissues found in the walls of arteries.
Explain their role.

Answer 28

• Smooth muscle: maintains blood flow and enables distribution of blood via vasoconstriction and vasodilation
• Endothelium/tunica intima: smooth flattened cells that reduce friction and resistance so blood flows smoothly
• Collagen: avoids arteries from bursting under high pressure
• Elastic fibres to allow surges in blood flow: recoil enables blood pressure to be maintained and also to help force blood forwards

Question 29

Describe and explain the features of capillary walls

Answer 29

 Single layer of squamous endothelial cells (thin & flat)
 Have pores between cells called fenestrations -> enables formation of TF and for WBC to squeeze through to form macrophages
 Walls are ‘leaky’ to allow constant exchange of materials

Question 30

Name the 3 layers of artery walls and state their composition

Answer 30

o Tunica externa: collagen fibres & elastic fibres
o Tunica media: smooth muscle & elastic fibres
o Tunica intima: single layer of endothelial cells

Question 31

Explain why artery walls have a high quantity of smooth muscle tissue

Answer 31

Maintains blood flows & redistributes blood via vasoconstriction and vasodilation

Question 32

Explain why artery walls have a high quantity of elastic tissue

Answer 32

Enables the BV to stretch during ventricle systole & recoil during ventricle diastole

Question 33

Explain why the lumen of an artery is made from endothelial cells

Answer 33

Cells are flat
This produces a smooth inner lining which
Reduces friction
Reduces resistance
Enables smooth blood flow

Question 34

Describe the role of capillaries

Answer 34

Site of exchange between plasma and cells i.e. glc & O2 delivered to cells

Remember: they enable 2 way exchange i.e. delivery of nutrients but also removal of waster products (such as CO2) from cells

Question 35

Make sure you can interpret this diagram

Answer 35

Question 36

Explain possible causes of hypertension

Answer 36

 damage to endothelium of artery walls leads to an aneurysm (rupture of artery wall) or blood clot  heart attack or stroke
 damage heart valves (both semilunar and atrioventricular)
 kidney disease as capillaries in glomerulus are damaged by persistent high BP

Question 37

Define hypotension

Answer 37

Persistently low blood pressure

Question 38

State the advantages of using an electronic device to measure BP

Answer 38

• Data can be collected over a long period of time
• Continual readings can be recorded by the device
• Person does not have to make repeated visits to clinic i.e. maintain lifestyle (job)
• Data collected remotely