C6 - Transport Systems in Mammals

Question 1

Why do you larger organisms have transport systems?

Answer 1

Diffusion would take too long as they have a small surface area to volume ratio reducing the rate of diffusion.

Question 2

What are the components of a specialised circulatory system?

Answer 2

The heart

The fluid in which substances are transported

Vessels through which the fluid flows

Question 3

What occurs in an open circulatory system?

Answer 3

The system consisting of the hearts that pumps the fluid ‘haemolymph’ through the short vessels went into a large cavity called the haemocoel.

In the haemocoel, the haemolymph directly bathes organs and tissues enabling the diffusion of substances.

When the heart relaxes, the haemolymph blood is sucked back via pores called ostia.

Question 4

What is an open circulatory system?

Answer 4

When blood flows freely through the body cavity, carrying nutrients to their cells.

Question 5

What is the closed circulatory system?

Answer 5

One where blood is fully enclosed within blood vessels at all times.

Blood is pumped through vessels and substances enter and exit via diffusion.

This is beneficial as in a closed system pressure can be created.

Question 6

Why is a closed circulatory system beneficial?

Answer 6

Pressure can be created and blood pressure can be maintained throughout the body

Pressures can differ in the pulmonary and systemic systems

Blood supply to different organs varies depending on the function and need for example the gut needs more blood during digestion

Lower volumes of transport fluid, the blood, are needed to keep the system moving than in an open system

Question 7

What’s a double circulation system?

Answer 7

When there are two circuits - one is the circuit between the lungs and the heart (the pulmonary circuit) and the other is between the body and the heart (the systemic circuit)

Question 8

What are the advantages of a double system?

Answer 8

Blood pressure can be maintained around the body rather than falling due to resistance to flow as it moves through the lungs and other tissues.

Oxygenated blood doesn’t mix with deoxygenated blood making oxygen uptake from exchange more efficient

There is a greater efficiency of the delivery of nutrients and oxygen

Blood pressure and the systemic and pulmonary circulation is can be maintained at different pressures

Question 9

What are the different blood vessels?

Answer 9

Arteries
Veins
Capillaries
Arteriolar
Venules

Question 10

What is the structure of arteries?

Answer 10

They have a thick wall with large amounts of smooth muscle and elastic fibres

The inner endothelia lining is smooth to reduce friction

There are no valves

They have a small lumen

Question 11

What is the function of arteries?

Answer 11

They keep the pressure high as the blood is distributed throughout the circuit.

The artery wall stretches during ventricular systole and recoils during ventricular diastole.

Question 12

What is the bloodflow of arteries?

Answer 12

They take blood away from the heart under high-pressure

High-pressure pulses as the pressure fluctuates

Question 13

What is the structure of veins?

Answer 13

They have a wide lumen and a thin walls with a small amount of muscle and elastic tissue.

Semilunar valves are found all along the length

Question 14

What is the function of veins?

Answer 14

Blood is carried on the low-pressure and the thin wall makes it easier to compress the vessel when the skeletal muscles contract around them.

This aids blood flow through the veins

Question 15

What is the blood flow within veins?

Answer 15

They return blood to the heart

Flow is slow because the pressure is low

There is no pulse

The valves prevent back flow and keep the flow moving in one direction which is necessary with the low-pressure

Question 16

What is the structure of capillaries?

Answer 16

The wall is a single layer of squamous epithelial cells with no elastic on muscle tissue

Question 17

What is the function of capillaries?

Answer 17

They connect arterioles and venules forming a vast network within the tissues.

The size of the network provides a large overall cross-sectional area for exchange of materials between the blood and surrounding tissues

Question 18

What is the blood flow within capillaries?

Answer 18

See allows the flow between the arterioles and venules.

Rate of flow is slow as the pressure is low.

Question 19

What is the structure, function and blood flow within arterioles?

Answer 19

They have a thin wall mainly of muscle and some elastic fibre

They carry blood between arteries and capillaries. They regulate the flow and distribution.

Smooth-muscle contracts to constrict the lumen or relax and dilate the lumen to allow blood pressure and distribution to be regulated.

Question 20

What is the structure, function and blood flow within venules?

Answer 20

They have very thin walls of muscle and elastic fibres.

They carry blood from capillaries back to the veins.

The wall has only a thin layer of muscle which does not provide any assistance in blood flow.
Valves along the length of the venue prevent back flow.

Question 21

What moves blood forwards within arteries?

Answer 21

Elastic fibres contribute to blood pressure is elastic fibres and arteries stretch during systole and recoil in diastole, propelling the blood forwards.

Question 22

How is blood pressure calculated?

Answer 22

Systolic pressure divided by diastolic pressure measured in millimetres of mercury.

Question 23

What is systolic pressure?

Answer 23

Pressure created by the contraction of the left ventricle / the force generated by the left ventricle contracting

Question 24

What is diastolic pressure?

Answer 24

Pressure reflecting the elasticities of artery walls

Question 25

How does blood flow in veins?

Answer 25

There is no pulse so skeletal muscles around the veins contract and relax. Surrounding muscle contraction increases blood pressure.

As they relax blood pressure falls so more blood from the capillaries can flow in.

Valves prevent back flow

Question 26

What is hypertension?

Answer 26

A permanently raised high blood pressure

Question 27

What is hypotension?

Answer 27

Are permanently lowered blood pressure

Question 28

What can hypertension cause?

Answer 28

Damage to the lining of artery walls causing an aneurysm. This could lead to a heart attack or stroke.

Damage to heart valves

Kidney disease as the capillaries within the kidney are damaged by constant high-pressure

Question 29

What can hypotension cause?

Answer 29

Weakness and tiredness

Dizziness and fainting

Coma and possible death

Question 30

What risk factors can contribute to hypertension?

Answer 30

Smoking
Being obese or overweight
A diet high in salt
Excess alcohol consumption
High levels of stress
Age - the older you are the greater the risk
Gender – males have increased risk
Low levels of exercise

Question 31

What is the name of the vein and artery that travels to and from the head and neck?

Answer 31

Carotid artery (to the head)

Jugular vein (away from head)

Question 32

What is the name of the vein and artery that travels to and from the upper limbs?

Answer 32

The subclavian artery (to the fore limbs)

The subclavian vein (away from upper body)

Question 33

What is the name of the vein and artery that travels to and from the lungs?

Answer 33

Pulmonary artery (to the lungs)

Pulmonary vein (to the left atrium)

Question 34

What is the name of the vein and artery that travels to and from the liver?

Answer 34

Hepatic artery (from the heart)

Hepatic portal vein (from the stomach and intestines to the liver)

Hepatic vein (to the heat)

Question 35

What is the name of the vein and artery that travels to and from the kidney?

Answer 35

Renal artery

Renal vein

Question 36

What is the name of the vein and artery that travels to and from the gonads (reproductive glands)?

Answer 36

Genital artery

Genital vein

Question 37

What is the name of the vein and artery that travels to and from the lower body / hind limbs?

Answer 37

Iliac artery

Iliac vein

Question 38

What is tissue fluid?

Answer 38

The fluid that surrounds body cells.

It has a similar composition to blood plasma except it contains no large proteins and no cells.

Excess tissue fluid that’s not reabsorbed is known as lymph.

Question 39

What is the function of tissue fluid?

Answer 39

To supply cells with nutrients and remove waste products.

Question 40

What is hydrostatic pressure?

Answer 40

Pressure created by a fluid pushing against the sides of a vessel.

Question 41

What is oncotic pressure?

Answer 41

Also known as colloid osmotic pressure, it is the force due to the tendency of plasma proteins and other substances to lower the water potential.

It tends to pull fluids into the circulatory system.

Question 42

What is another name for colloid osmotic pressure?

Answer 42

Oncotic pressure.

Also known as colloid osmotic pressure, it is the force due to the tendency of plasma proteins and other substances to lower the water potential.

It tends to pull fluids into the circulatory system.

Question 43

How is tissue fluid formed?

Answer 43

(Arteriole end)
Slow blood flow through many capillaries and high hydrostatic pressure results in small molecules and water leaving the capillaries.

Larger protein molecules remain in the capillaries/blood plasma and create an oncotic force. This is negative and pulls the water back in. Hydrostatic pressure is greater than oncotic so there’s a net outward force.

(Venule end)
Hydrostatic pressure has now fallen due to loss of fluid so oncotic pressure is higher than hydrostatic, drawing fluid back into the capillary.

Some tissue fluid doesn’t return and drains into the lymphatic system which carries excess tissue fluid back to veins in the neck.

Question 44

What creates the oncotic pressure in the formation of tissue fluid?

Answer 44

The large protein molecules which remain in the capillary blood plasma.

Question 45

Why does the exchange of fluid occur in capillaries?

Answer 45

They’re made of very thin, flat, squamous epithelial cells with many fenestrations (gaps) which make the walls permeable to small molecules.

They’re ‘leaky’ so materials can be exchanged.