Exchange Surfaces And Breathing- 3.1

Question 1

What affects the need for specialised exchange surfaces ?

Answer 1

-whether the organism is single-celled or multicellular - in single-celled organism the cytoplasm is very close to the environment in which they live. So diffusion will be able to supply enough oxygen and nutrients. In multicellular organisms there is a much longer diffusion pathway as the organism may have several layers of cells, so diffusion will be too slow.

-surface area to volume ratio-small organisms will have a large surface area to volume ratio meaning there surface area is large enough to supply all their cells with sufficient oxygen. Large organisms have a small surface area to volume ratio

-metabolic activity- the need for energy is higher in some organisms than in others

Question 2

What is the equation for surface area to volume ratio?

Answer 2

Ratio= surface area / volume

Question 3

What is the equation for surface area?

Answer 3

SA= (length x height ) number of sides

Question 4

What is the equation for volume?

Answer 4

Volume= length x height x depth

Question 5

What are the features of an efficient gas exchange system?

Answer 5

-a large surface area - to provide more space for molecules to pass through. For example by folding the walls and membranes involved e.g. in root hair cells
-a thin barrier- to reduce diffusion distance and that is permeable to the substances being exchanged. E.g. in the alveoli
-a good blood supply and ventilation -in order to maintain concentration gradient. E.g. in gills or in the alveolus

Question 6

What are the mechanics behind inspiration (inhaling)?

Answer 6

1-the diaphragm contracts to move down and become flatter, this displaces the digestive organs downwards
2-the external intercostal muscles contract to raise the ribs
3-the volume of the chest cavity is increased
4-the pressure in the chest cavity drops below atmospheric pressure
5-air is moved into the lungs

Question 7

What are the mechanics behind expiration (exhaling)?

Answer 7

1- the diaphragm relaxes and is pushed up by the displaced organs underneath
2-the external intercostal muscles relax and the ribs fall (the internal intercostal muscles can contract to help push air out more forcefully e.g. during exercise, coughing and sneezing)
3-the volume of chest cavity is decreased
4-pressure in the lungs increases and rises above the pressure in the surrounding atmosphere
5-air is moved out of lungs

Question 8

What is the bucal cavity in a fish?

Answer 8

The mouth

Question 9

What is a countercurrent flow?

Answer 9

When 2 fluids flow in opposite directions

Question 10

What are gill filaments in a fish?

Answer 10

—often called primary lamellae
-slender branches of tissue that make up the gill
-each gill consists of 2 rows of gill filaments attached to the bony arch
-filaments are very thin and their surface is folded into many secondary lamellae

Question 11

What are (secondary) lamellae?

Answer 11

-also called gill plates
-folds of the filament to increase surface area

Question 12

What is the operculum in a fish?

Answer 12

A bony flap that covers and protects the gills

Question 13

Describe countercurrent flow?

Answer 13

-blood flows along the gill arch and out along the filaments to the secondary lamellae
-the blood then flows through capillaries in the oposite direction to the flow of the water over the lamellae
-this creates a countercurrent flow that absorbs the maximum amount of oxygen from the water

Question 14

Describe how changes in the volume of the buccal cavity can help ventilation?

Answer 14

-the buccal cavity can change volume
-the floor of the mouth moves downwards ,drawing water into the buccal cavity
-the mouth closes and the floor is raised again pushing water through the gills
-movements of the operculum are coordinated with the movements of the buccal cavity- as water is pushed from the buccal cavity ,the operculum moves outwards
-this movement reduces pressure in the opercular cavity (the space under the operculum) this helps water to flow through the gills

Question 15

How is the circulatory system in an insect?

Answer 15

-they do not transport oxygen in blood
-they have an open circulatory system in which the body fluid acts as both blood and tissue fluid
-circulation is slow and can be affected by body movement

Question 16

What is a spiracle in an insect?

Answer 16

-an external opening or pore that allows air in or out of the trachea

Question 17

What is tracheal fluid in an insect?

Answer 17

The fluid found at the ends of the tracheoles in the tracheal system

Question 18

What is the tracheal system in an insect?

Answer 18

A system of air-filled tubes in insects

Question 19

Where does gas exchange occur in an insect?

Answer 19

-between the air in the tracheole and the tracheal fluid

-some exchange can also occur across the thin walls of the tracheoles

Question 20

Describe how air moves through an insect

Answer 20

-air enters the system via a spiracle
-the air is transported into the body through a series of tubes called tracheae (singular trachea)
-these divide into smaller tubes, called tracheoles -the ends of tracheoles are open and filled with tracheal fluid
-gas exchange occurs between the air in the tracheole and the tracheal fluid

Question 21

How does an insect increase oxygen absorption when active?

Answer 21

-when tissues are very active the tracheal fluid can be withdrawn into the body fluid in order to increase the surface area of the tracheal exposed to air
-this means that more oxygen can be absorbed when the insect is active

Question 22

How can air sacs in an insect help with ventilation?

Answer 22

-in many insects sections of the tracheal system are expanded and have flexible walls
-these act as air sacs which can be squeezed by the action of the flight muscles
-repetitive expansion and contraction of these sacs ventilate the tracheal system

Question 23

How can movement of an insects wing help with ventilation?

Answer 23

-in some insects movement of the wings alter the volume of the thorax
-as the thorax volume decreases, air in the tracheal system is put under pressure and is pushed out of the tracheal system
-when the thorax increases in volume , the pressure inside drops and air is pushed into the tracheal system from outside.

Question 24

How do some insects use abdominal movements to change body volume?

Answer 24

-locusts can alter the volume of their abdomen by specialised breathing movements
-these are coordinated with opening and closing valves in the spiracles
-as the abdomen expands spiracles at the front end of the body open and air enters the tracheal system
-as the abdomen reduces in volume, the spiracles at the rear end of the body open and air can leave the tracheal system

Question 25

What is the function of cartilage in the mammalian gaseous exchange system?

Answer 25

Rings of cartilage line the trachea. Cartilage is a strong but flexible tissue and is essential for keeping the trachea open. Because of its flexibility, the cartilage is able to move and flex as we breathe.
Larger bronchioles also have cartilage and so do the bronchi

Question 26

What is the function of ciliated epithelial cells in the mammalian gaseous exchange system?

Answer 26

-line the trachea to the bronchi
-each cell has tiny projections called cilia
-cilia sweeps mucus , dust bacteria and other microorganisms up and away from the lungs to the mouth where they are swallowed and destroyed by stomach acid

Question 27

What is the function of goblet cells in the mammalian gas exchange system?

Answer 27

-they are found in the ciliated epithelium cells
-they release mucus which traps pathogens
-the cilia then move the mucus to the top of the airway where it is swallowed

Question 28

What is the function of smooth muscle in the mammalian gas exchange system?

Answer 28

-smooth muscle is not under conscious control
-it is found in the walls of the bronchi and bronchioles
-it helps regulate the flow of air into and out of the lungs by dilating and widening when more air is needed
-it can control the flow of air to the alveoli which may be important if there are harmful substances in the air

Question 29

What is the function of the elastic fibres in the mammalian gaseous exchange system?

Answer 29

-found in trachea,bronchi bronchioles and alveoli
-they allow the alveoli to stretch as they fill with air and recoil to help them force air out-this helps increase the alveoli’s surface area

Question 30

What are some adaptions of the alveoli?

Answer 30

An extensive capillary network surrounds them
Lined by a thin layer of moisture to facilitate the diffusion of gases.
Thin walls. Large surface area to volume ratio

Question 31

What are alveoli?

Answer 31

The main site of gas exchange in the lungs. They contain a single layer of epithelium and have elastic fibres