3.1: Exchange surfaces and breathing

Question 1

Why do single celled organisms not need specialised exchange surfaces?

Answer 1

Substances can easily enter the cell because the distance that needs to be travelled is short

Question 2

Why do multicellular organisms need specialised exchange surfaces?

Answer 2

This is because they have a lower surface area to volume ratio whihc means there is a larger distance that substances need to cross over

Question 3

What are features of specialised exchange surfaces?

Answer 3

• Larger surface area (root hair cells/folded membranes)
• Thin - means short diffusion distance
• Good blood supply - maintains steep gradient

Question 4

How does air enter the lungs?

Answer 4

Air enters through the nose, along the trachea, bronchi and bronchioles
Takes place in the alveoli

Question 5

What is the alveoli?

Answer 5

They are air sacs filled with air

• Smallest clusters of bronchiole have alveoli
• 1 cell thick

Question 6

What are the airways held open with?

Answer 6

They are held open with rings of cartilage
However, in the trachea it is incomplete as it allows food to pass through

Question 7

What are similarities and differences of the trachea and bronchi?

Answer 7

Differences:

• Bronchi is narrower

Similarities:

• Composed of several layers, make of thick wall of cartilage (incomplete c rings)
• Inside surface of cartilage is a layer of glandular and connective tissue, elastic fibre, smooth muscle and blood vessles (reffered to as loose tissue)
• Inner lining is an epithelial layer composed of ciliated epithelium and goblet cells

Question 8

What are the structures or functions of cartilage?

Answer 8

Involved in supporting the trachea and bronchi
Plays an important role in preventing the lungs from collapsing in the event of pressure drop during exhalation

Question 9

What are the structures and functions of the ciliated epithelium?

Answer 9

• Present in bronchi, bronchioles and trachea
• Involved in moving mucus along to prevent lung inflaion by moving it towards the throat

Question 10

What are the structures and functions of goblet cells?

Answer 10

• Cells present in the trachea, bronchi and bronchioles
• Involves in mucus secretion to trap bacteria and dust to reduce the risk of infection with the help of lysozome which digests bacteria

Question 11

What are the structures and functions of smooth muscle?

Answer 11

Their ability to contract enables them to play a role in constricting the airway thus controllong its diameter as a result and thus controlling the flow of air to and from the alveoli

Question 12

What are structures and functions of elastic fibres?

Answer 12

Strecth when we inhale and recoil when we exhale thus controlling the flow of air

Question 13

What is ventalation?

stages and muscles

Answer 13

The flow of air to and from the alveoli
Stages: Inspiration and exhalation
Muscles: Intercostal and diaphragm

Question 14

What happens in inspiration?

Answer 14

1. External intercostal muscles contract whereas the internal ones relax and ribs raise upwards
2. Diaphragm contracts ad flattens
3. Volume of chest cavity increases which lowers the pressure
4. Difference between pressure inside the lungs and atmospheric oressure creates a gradient and air enter the lungs

Question 15

What happens in expiration?

Answer 15

1. Internal intercostal muscles contact whereas external ones relax and this lowers the ribcage
2. Diaphragm relaxes and rises upwards
3. These actions decrease the volume of the chest cavity and the pressure increases
4. This forces air out of the lungs

Question 16

What is a spirometer and what happens?

Answer 16

A device that is used to measure lung volume

Person breathes in and out of airtight chamber and it moves up and down
It leaves a trace of the graph that can be interpreted

Question 17

What is vital capacity?

Answer 17

Maximum volume of air that can be inhaled and exhaled in a single breath. Varies by age, gender and size

Question 18

What is tidal volume?

Answer 18

The volume of air we breathe in and out at each breath at rest (it can be exceeded)

Question 19

What is breathing rate

Answer 19

The number of breaths per min calculated by number of peaks in 60 seconds

Question 20

What is residual volume?

Answer 20

Volume of air always present in lungs

Question 21

What is expiratory reserve volume?

Answer 21

Additional volume of air that can be exhaled on top of the tidal volume

Question 22

How are substances transported in insects?

Answer 22

Insects do not posess a transport system so oxygen needs to be transported directly to tissues undergoing respiration
This is achieved by spiracles

Question 23

What are spiracles?

Answer 23

Small openings of tubes, either bigger trachea or smaller tracheals. They run into the body and supply it with required gases
They are opened or closed to avoud excessive water loss

Question 24

What is tracheal fluid?

Answer 24

At the end of a tracheole and allows gases to dissolve and then diffuse into the cells

Question 25

How are insects ventilated?

Answer 25

Sections of the tracheal system are expanded and have flexible walls

• They act as air sacs and are squeezed by the action of the flight muscles
• Repetitive expansion and contraction of these sacs ventilate tracheal system

Question 26

How do movements of the wings alter the volume of the thorax?

Answer 26

1. Thorax volume decreases, air in the tracheal system put under pressure and pushed out of the trachela system
2. Thorax volume increases, pressure inside drops and air is pushed into the tracheal system from the outside

Question 27

How do locusts and other insects ventilate?

Answer 27

They alter the volume of abdomen by specialised breathing movements
1. Abdomen expands, spiracles at front end of body open and air enters the tracheal system
2. Abdomen reduces in volume, spiracles rear end of the body open and air can leave the tracheal system

Question 28

What are the features of bony fish?

Answer 28

• Small surface area to volume ratio for gas exchange
• Impermeable membrane so gases cannot diffuse through their skin

Question 29

What is the features of gills?

Answer 29

• Each gill is supported by a gill arch
• Along each arch are gill filaments (projections)
  They have lamellae - participate in gas exchange
• Blood and water flows across lamellae in counter current direction

Question 30

Why can fish not survive long out of water?

Answer 30

Projections held apart by water flow
Absence of water they stick together

Question 31

How does ventilation occur in bony fish?

Answer 31

1. Fish opens mouth followed by lowering the floor of buccal cavity (enables water to flow into it)
2. Fish closes mouth - buccal cavity floor raises which increases pressure
3. Water is forced over the gill filaments by difference in pressure between mouth cavity and opercular cavity
4. Operculum acts as a valve and pump, lets water out and pumps it in

Question 32

What are precautions when using a spirometer?

Answer 32

• Subject should be healthy - free of asthma
• Soda lime fresh and functioning
• Mouthpiece should be sterilised
• Water chamber must not be overfilled