Chapter 6.1 Transport systems in mammals Flashcards
Explain why mammals needs a circulatory system
- 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
State the benefits of a closed circulatory system
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
State the benefit of a double circulatory system
pulmonary + systemic circuits are separated
pressure can be maintained separately
blood does not mix ∴ oxygen/nutrient uptake at exchange site is more efficient
List the layers of an artery’s wall (start from the lumen and work outwards)
lumen
tunica intima
endothelium
internal elastic lastima
tunica media
external elastic lastima
tunica externa
vasa vasorum
State the function of elastic fibres in arteries
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
State the function of smooth muscle in the artery walls
contract –> forces blood through at high pressure
can change the size of the lumen
this reduces resistance to blood flow
List the layers of a vein’s walls(start form the lumen and work outwards)
lumen
tunica intima
endothelium
tunica media
tunica externa
vasa vasorum
Describe how blood is moved in veins
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
Describe the structure of the capillary walls
Made of squamous endothelium
Smooth surface (reduces resistance to blood flow)
Walls are one cell thick
Define systolic pressure
the pressure in the arteries as blood is forced out of the left ventricle during systole
Define diastolic pressure
the pressure during diastole
State how BP can be measured
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
Describe how is blood pressure measured
- 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
Define hypertension
Persistently high blood pressure
At a clinic BP of 140/90 mmHg
At home BP of 135/85mm Hg
State 4 risk factors that contribute to hypertension
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
Describe the health risks associated with hypertension
damage to artery walls –> aneurysm/blood clot
damage to heart valves
kidney disease
State the health risks associated with hypotension
weakness & tiredness
dizziness & fainting
coma
potentially fatal :(
Describe the tissue fluid
fluid that surrounds the cells of the body
State the function of tissue fluid
to supply cells with nutrients and to remove waste products
exchange of materials at capillaries
Describe how tissue fluid is formed
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
Describe lymph
similar to tissue fluid but more leucocytes
Describe the function of lymph?
important in immune response - nodes are site for filtration of pathogens/foreign bodies
Define a closed circulatory system
Blood always moves within blood vessels allows pressure to be maintained
Describe a double circulatory system
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
State the advantages of a DCS
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)
State the advantages of a closed circulatory system
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)
Complete the table
State the tissues found in the walls of arteries.
Explain their role.
- 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
Describe and explain the features of capillary walls
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
Name the 3 layers of artery walls and state their composition
o Tunica externa: collagen fibres & elastic fibres
o Tunica media: smooth muscle & elastic fibres
o Tunica intima: single layer of endothelial cells
Explain why artery walls have a high quantity of smooth muscle tissue
Maintains blood flows & redistributes blood via vasoconstriction and vasodilation
Explain why artery walls have a high quantity of elastic tissue
Enables the BV to stretch during ventricle systole & recoil during ventricle diastole
Explain why the lumen of an artery is made from endothelial cells
Cells are flat
This produces a smooth inner lining which
Reduces friction
Reduces resistance
Enables smooth blood flow
Describe the role of capillaries
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
Make sure you can interpret this diagram
Explain possible causes of hypertension
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
Define hypotension
Persistently low blood pressure
State the advantages of using an electronic device to measure BP
- 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
