Exchange and Transport: Exchange Surfaces

Question 1

What are the three main features of an efficient exchange surface and where they are found?

Answer 1

Large surface area - root hair cells
Thin layer e.g. short diffusion distance - alveoli
Good blood supply to maintain steep concentration gradient - gills, alveolus

Question 2

Where and what is the function of cartilage?

Answer 2

• Cartilage is found in the trachea of the mammalian gaseous exchange system
• Cartilage helps keep the trachea open and prevents collapsing during expiration and inspiration

Question 3

Where and what is the function of the ciliated epithelium?

Answer 3

• Ciliated epithelium lines the trachea, bronchi, nasal cavities
• Ciliated epithelial cells are important in propelling mucus up the airway, thereby removing particulate material.

Question 4

Where and what is the function of goblet cells?

Answer 4

• They are inside the trachea, bronchi and larger bronchioles
• They secrete mucus

Question 5

Where and what is the function of smooth muscle?

Answer 5

• Smooth muscle is found in the walls of airways from the trachea to alveolar ducts
• Controlling airway diameter

Question 6

Where and what is the function of elastic fibres?

Answer 6

• In the walls of the trachea
• They help with the process of breathing out, they stretch in order to breathe out

Question 7

Describe the mechanism of inspiration:

Answer 7

• Diaphragm contracts (flattens and lowers)
• The external intercostal muscles contract causing the ribs to move upwards and outwards
• This increases the volume of the thorax
• This reduces the pressure meaning the air inside in lower than atmospheric pressure around
• So air is drawn through the nasal passages, trachea, bronchi and bronchioles and into the lungs

Question 8

Describe the mechanism of expiration:

Answer 8

• Muscles of the diaphragm relax, moving it up into its resting shape
• External intercostal muscles relax so the ribs move down and inwards under gravity
• Elastic fibres in the alveoli return to normal size
• Causing the thorax to decrease in volume
• Pressure inside the lungs is greater than the pressure of the atmosphere
• Air moves out of the lungs until the pressure inside is equal to the outside

Question 9

Describe the mechanism of expiration by using energy:

Answer 9

• Intercostal muscles contract
• This pulls the ribs down hard and fast
• The abdominal muscles contract
• Which forces the diaphragm up to increase pressure in lungs rapidly

Question 10

Define Vital Capacity (VC):

Answer 10

The maximum amount of air a person can exhale after taking the deepest possible breath. Represents the maximum volume of air that can be moved in and out of the lungs. VC = Inspiratory reserve volume + Tidal Volume + Expiratory Reserve volume

Question 11

Define Tidal Volume:

Answer 11

The volume of air inhaled or exhaled in a single breath under normal, resting conditions. It is usually around 500ml in adults at rest.

Question 12

Define breathing rate:

Answer 12

The number of breaths taken per minute.

Question 13

Define oxygen uptake:

Answer 13

The amount of oxygen the body uses per minute. It’s related to the metabolic demand for oxygen and is influenced by factors such as physical activity level, fitness and overall health

Question 14

Describe the mechanism of inspiration in fish

Answer 14

• The operculum is shut and the operculum cavity expands. The mouth opens and floor of the buccal cavity is lowered.
• The volume of the buccal cavity increases
• This decreases the pressure inside lower than surrounding water pressure, causing water to rush in.

Question 15

Describe the mechanism of expiration in fish

Answer 15

• The floor of the buccal cavity moves up and the mouth closes. The buccal cavity and the operculum cavity constrict. Opening the operculum.
• The volume of the buccal cavity decreases
• Increasing the pressure inside higher than the surrounding water pressure, causing water rush out

Question 16

Function of the operculum

Answer 16

Is a bony flap that protects the gills from harm. It opens and closes to allow water to pass over the gills.

Question 17

Function of gill filaments

Answer 17

They provide oxygen to the blood by taking oxygen from the water. Each filament contains thousands of lamellae that are exposed to the water. Oxygen is absorbed and re-emitted into the fish’s blood.

Question 18

Function of gill lamellae

Answer 18

They are used to increase the surface area in contact with the environment to maximise gas exchange (to attain oxygen and to expel carbon dioxide) between the water and the blood.

Question 19

Description and function of countercurrent flow in gills

Answer 19

Water that flows over the gills flows in the opposite direction to the blood. Meaning the exchange of oxygen and carbon dioxide is more efficient than if the water and blood were both flowing in the same direction .

Question 20

Describe the gas exchange system in insects

Answer 20

• Insects have spiracles which open and close by sphincters to allow gas in and out. The pores on the abdomen are necessary because insects have tough exoskeletons so gas exchange cannot occur through skin
• Gas travels through the tracheae which leads away from the spiracles into the body cavity. The tracheae are chitinous forming a rigid structure.
• They lead to the tracheoles which have many branches meanings there’s a large SA. This is where gas exchange into the body occurs. They are highly permeable.
• Tracheal fluid limits penetration of oxygen down tracheoles, reducing area available for diffusion, but during periods of high activity the build up of lactic acid causes tracheal fluid to move out and expose more area for gas exchange.

Question 21

Some insects with higher energy demands have additional methods of increasing gas exchange, what are they?

Answer 21

• Mechanical ventilation - muscular movements of the thorax actively pump air into the respiratory system.
• Air sacs - they act as reservoirs during times of high activity, but can be deflated.