7.2 Mammalian Gaseous Exchange System

Question 1

Why do mammals need effective gas exchange systems?

Answer 1

Small SA:V ratio, large volume of cells

Higher metabolic rate because:

• Active
• Maintain body temperature

Question 2

What’s the consequence of mammals having a small SA:V ratio and high metabolism?

Answer 2

They need lots of oxygen for cellular respiration and they produce CO2 (which needs to be removed.

This exchange of gases occurs in the lungs.

Question 3

What are the 3 features of the nasal cavity?

Answer 3

1. Large SA w/ GBS
2. Hairy lining
3. Moist surfaces

Question 4

What is the function of a large SA w/ GBS in the nasal cavity?

Answer 4

Warms inhaled air to body temperature

Question 5

What is the function of a hairy lining in the nasal cavity?

Answer 5

Secretes mucus.
Mucus traps dust and bacteria.
This protects lung tissue from irritation or infection.

Question 6

What is the function of moist surfaces in the nasal cavity?

Answer 6

Humidity of incoming air is increased, reducing evaporation from exchange surfaces.

Question 7

What is the state of the air entering the lungs as a result of the nasal cavity adaptations?

Answer 7

The air entering the lungs is a similar temperature + humidity to air already there.

Question 8

What is the trachea and what does it do?

Answer 8

Main airway carrying clean + warm + moist air from the nose to the chest

Question 9

Describe the structure of the trachea

Answer 9

Wide tube supported by incomplete rings made up of strong, flexible cartilage - stops trachea collapsing

Question 10

Why are the rings supporting the trachea incomplete?

Answer 10

So food can move down the oesophagus behind the trachea

Question 11

What is the trachea and its branches lined with?

Answer 11

A ciliated epithelium w/ goblet cells between and below the epithelial cells

Question 12

What is the function of goblet cells?

Answer 12

To secrete mucus onto the lining of the trachea.

Question 13

What is the function of mucus released from goblet cells?

Answer 13

To trap dust and microorganisms that escaped the nose lining

Question 14

What do cilia do?

Answer 14

Beat and move mucus along w/ any trapped dirt and microorganisms away from the lungs - most goes into throat = swallowed + digested

Question 15

What is one effect of smoking?

Answer 15

Cigarette smoke stop cilia beating

Question 16

What is the bronchus?

Answer 16

Where the trachea divides to form the left bronchus leading to left lung, and right bronchus leading to right lung.

Question 17

What is the structure of the bronchi?

Answer 17

Similar to trachea, w/ supporting rings of cartilage, but smaller

Question 18

What does 1 bronchi divide into?

Answer 18

Many small bronchioles

Question 19

What is the structure of the bronchioles?

Answer 19

No cartilage rings ( Diameter 1mm< )

Walls contain smooth muscle

Lined with thin layer of flattened epithelium, making some gas exch. possible

Question 20

What is the function of the smooth muscle in the walls of bronchioles?

Answer 20

Muscle contracts = bronchioles constrict (close)

Muscle relaxes = bronchioles relax (open
Changes how much air reaches lungs)

Question 21

What are alveoli?

Answer 21

Tiny air sacs which are the main gas exchange surfaces of the body

Question 22

Describe the structure of alveoli and the function of its structure

Answer 22

• Consist of thin, flattened epithelial cells + collagen + elastic fibres (composed of elastin)

These elastic tissue enable alveoli to stretch as air comes in. When they return to normal size, air is pushed out. This is known as elastic recoil of the lungs.

Question 23

What are the 4 adaptations of the alveoli?

Answer 23

1. Large SA
2. Thin layers
3. GBS
4. Good ventilation

Question 24

Explain how thin layers are an adaptation in alveoli

Answer 24

Alveoli are one cell thick - short diffusion distance

Question 25

Explain how a good blood supply is an adaptation in alveoli

Answer 25

Constant blood flow maintains a steep concentration gradient

Question 26

Explain how good ventilation is an adaptation in alveoli

Answer 26

Breathing moves air in + out of alveoli, maintaining steep diffusion gradients for O2 + CO2 between blood + air in lungs

Question 27

What is the inner surface of the alveoli covered in?

Answer 27

Thin layer of water, salts and lung surfactant

Question 28

Where are lung surfactants? What is their function?

Answer 28

1. Inner surface of alveoli | 2. Enables alveoli to remain inflated

Question 29

What happens to oxygen as a result of the solution of water on the inner surface of the alveoli?

Answer 29

Oxygen dissolves into the water before diffusing into the blood, but water can also evaporate into the air in the alveoli

Question 30

What is ventilation?

Answer 30

Movement of air in + out of lungs as a result of pressure changes in the thorax (chest cavity) as a result of breathing movements.

Question 31

What does the shape of the ribcage provide?

Answer 31

A semi-rigid case, in which pressure can be lowered in comparison to the air outside of it

Question 32

What is the diaphragm?

Answer 32

Broad, domed sheet of muscle which forms the floor of the thorax

Question 33

What types of muscle can be found between the ribs?

Answer 33

External intercostal muscles | Internal inercostal muscles

Question 34

What is the thorax lines lined by?

Answer 34

Pleural membranes which surround the lungs

Question 35

What do you call the space between the pleural membranes which line the thorax and what is their function?

Answer 35

Pleural cavity - Filled w/ thin layer of lubricating fluid so membranes easily slide over each other as you breathe

Question 36

What is inspiration?

Answer 36

Taking in air (inhalation) | Energy-using process

Question 37

What happens during inspiration?

Answer 37

- Diaphragm contracts + lowers - External intercostal muscles contract, moving ribs upwards + outwards - Vol. of thorax increases so pressure in thorax decreases - now lower than pressure of air so air is drawn through airway - this equalises pressure inside + outside chest

Question 38

What is expiration?

Answer 38

Exhalation (breathing air out) | Passive process

Question 39

What happens during expiration?

Answer 39

- Diaphragm relaxes; moves up into its resting domed shape - External intercostal muscles relax = ribs move downwards + inwards due to gravity - Elastic fibres in alveoli return to normal length The effect of this is that the vol. of thorax decreases - Pressure in thorax is now greater than normal air pressure, so air moves out of lungs until pressure inside and outside of lungs is equal

Question 40

What happens when you exhale forcibly?

Answer 40

- Internal intercostal muscles contract, pulling ribs down hard + fast - Abs contract, forcing diaphragm up to rapidly increase pressure in lungs