Chapter 8: Transport in animals

Question 1

Why do multicellular animals need transport systems ?

Answer 1

multicellular organisms have high metabolic demands (need loads of 02 and food in cells deep in the body) —> cannot be supplied by diffusion

multicellular organisms have a small SA:V ratio + are larger in size (and so large diffusion distance)

waste products need to be removed (from metabolic reactions)

Question 2

what is a circulatory system

Answer 2

a mass transport system responsible for carrying gases (o2 and co2) nutrients, waste products and hormones around the body to where they are needed.

Question 3

what are the different types of circulatory system

Answer 3

single circulatory system
open circulatory system
double circulatory system
closed circulatory system

Question 4

what features do all circulatory systems have in common

Answer 4

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

Question 5

what does an open circulatory system look like (in an insect)

Answer 5

very few vessels to contain transport medium, pumped straight from heart into the body cavity of animal

open body cavity = haemocoel —> blood here comes into direct contact with tissues and cells

exchange takes place between transport medium and cells under low pressure

Question 6

why doesn’t gaseous exchange take place via the open circulatory system in insects?

Answer 6

in insects gaseous exchange takes place in the tracheal system

also insect blood (haemolymph) does not carry co2 or o2

Question 7

what does a closed circulatory system look like

Answer 7

blood flows in enclosed vessels + the heart pumps the blood under pressure

substances leave and enter the blood by diffusion through the walls of the blood vessels

amount of blood flowing to a particular tissue can be adjusted through the widening and narrowing of these blood vessels

blood carries respiratory gases

Question 8

what does a single closed circulatory system look like (in fish)

Answer 8

blood travels through the heart once for each complete circulation

the blood passes through two sets of capillaries (in the gills and in the body)

in the gills it exchanges oxygen and co2, but in the body other substances are exchanged

blood flows back to the heart under low pressure ( limited efficiency of exchange due to circulatory system)

Question 9

what does a double closed circulatory system look like ?

Answer 9

most efficient system for transporting substances

blood travels through the heart twice in enclosed blood vessels

to the lungs (pulmonary circuit) and to the body (systemic circuit)- for gaseous exchange

travels to and away from the heart under high pressures

Question 10

Describe the structure and function of an artery

Answer 10

must carry blood away from the heart under high pressure

contains high proportions of elastic fibres and collagen ( and very low proportions of smooth muscle)

elastic fibres allow the the vessel walls to stetch and recoil - enabling it to with stand the force of blood pumped out of the heart and stetch

the collagen- provides a structural support to maintain the shape of the vessel

Question 11

What is the endothelium, where is it present and what function does it carry out

Answer 11

The endothelium is a thin layer of cells present in all of the blood vessels and enables blood to flow easily

Question 12

Describe the structure and function of an arteriole

Answer 12

higher proportion of smooth muscle, less elastin and little collagen

smooth muscle enables arteriole to constrict and dilate controlling the flow of blood to different capillary beds - vasoconstriction/dilation

elastin- allows it to stretch/ provides flexibility

collagen- provides support

Question 13

describe the structure and function of a capillary

Answer 13

are microscopic blood vessels linking arterioles and venules

consist of a thin layer of endothelial cell wall only- has large gaps where substances can pass out of the capillary for exchange (into the surrounding fluid)

thin layer for diffusion is provided

lumen of capillary is thin so the RBCs can travel in single file (for exchange)

Question 14

How are capillaries especially adapted to their role

Answer 14

provide a large surface area for diffusion into and out of the blood

rate of blood flow falls = more time for the exchange of materials by diffusion (because of larger total cross sectional area of the capillaries)

Question 15

Describe the structure and function of veins

Answer 15

transports blood back to the heart under low pressure (typically carries deoxygenated blood)

have high proportions of collagen and some smooth muscle, very low proportion of elastin

muscle and elastic layers are thin because constriction not needed to control flow of blood

contains a wide lumen- maximising volume of blood being carried to the heart, because pressure is low

weak pulse indicating little elastic tissue and smooth muscle

has valves to prevent backflow of blood

Question 16

Describe the structure and function of venules

Answer 16

link the capillaries to the veins

Venules have a high proportion of smooth muscle + very thin walls

this allows the constriction and dilatation

Question 17

What is hydrostatic pressure and what is oncotic pressure (Include their values)

Answer 17

oncotic pressure is the tendency for water to move out of the blood by osmosis and is always at -3.3 kPa

hydrostatic pressure is the pressure from the heart beating created when there is a surge of blood and it is always at + 4.6 kPa

Question 18

Describe the process of forming tissue fluid from blood plasma

Answer 18

blood flows in through the arterial end (of the capillary)-

hydrostatic pressure is higher than oncotic pressure here so there is an overall net movement of fluid out of the blood and out the capillary

this results in the formation of tissue fluid

Question 19

Describe the composition of the blood

Answer 19

blood consists of a yellow liquid called plasma (Mostly made up of water)

plasma contains a variety of components dissolved in it (glucose, amino acids, mineral ions, hormones + plasma proteins)

plasma also carries red blood cells, platelets + white blood cells

Question 20

Describe the composition of tissue fluid

Answer 20

same composition as plasma but without red blood cells and plasma proteins

Question 21

describe the composition of the lymph

Answer 21

lymph contains less oxygen + nutrients than tissue fluid + contains more fatty acids

Question 22

how is oxygen transported via the haemoglobin

Answer 22

oxygen binds reversibly (and loosely) to the haem groups in each of the 4 subunits (contain iron Fe 2+ ions)

this means that each haemoglobin molecule carries 4 o2 molecules

Question 23

how does oxygen show positive cooperativity in the haemoglobin

Answer 23

the arrangement of the haemoglobin molecule means that as soon as one oxygen molecule binds to the haem group the molecule changes shape.

this makes it easier for the next oxygen molecule to bind to the haem group.

Question 24

How does the oxygen dissociation curve work