7.2 The Mammalian Gaseous Exchange System

Question 1

Mammals require a specialised exchange surface due to their…

Answer 1

low SA:V

high metabolic rate

Question 2

How do mammals change the COMPOSITION of air during gas exchange?

Answer 2

inhale oxygen rich air

exhale carbon dioxide rich air

Question 3

Structures in the Human Gaseous Exchange System:

Answer 3

nasal cavity,
trachea,
bronchi/bronchioles,
alveoli

Question 4

Air first enters into the nasal cavity before the trachea. What is its function & its features related to each function?

Answer 4

WARMS air (good blood supply),
TRAPS dust & bacteria (hair + mucus),
increases HUMIDITY of air (moist),

Question 5

What are the advantages linked to each function of the nasal cavity?

1. warms air
2. traps dust & bacteria
3. humidifies air

Answer 5

good blood supply brings heat into large surface area,
lined with mucus & hair,
moist

Question 6

Why does air need to be HEATED to body temperature in the nasal cavity before entering the lungs?

Answer 6

prevents damage to delicate lung tissues (squamous epithelium, ciliated epithelium)

Question 7

What helps trap dust & bacteria in the nasal cavity?

Answer 7

mucus & hair

Question 8

Why does air need to be HUMIDIFIED in the nasal cavity before entering the lungs?

Answer 8

prevent evaporation of LUNG SURFACTANT

Question 9

What prevents the trachea from collapse due to air pressure changes?

Answer 9

rings of cartilage

Question 10

Why are rings of cartilage incomplete?

Answer 10

to allow peristalsis of oesophagus behind it

Question 11

Why are rings of cartilage required around the trachea?

Answer 11

prevent collapse from changes in air pressure

Question 12

What tissue is the trachea lined with?

Answer 12

ciliated epithelial tissue

goblet cells&raquo_space; mucus, ciliated epithelial cells&raquo_space; cilia

Question 13

air outside –> _____ –> _____ –> _____ –> _____ –> _____

Answer 13

nasal cavity, trachea, bronchi, bronchioles, alveoli

Question 14

Ciliated epithelial cells waft the dust/bacteria trapped in mucus towards the…

Answer 14

oesophagus so that it can be digested

Question 15

Rings of cartilage are found in…

Answer 15

trachea & bronchi

Question 16

Bronchi divide into…

Answer 16

bronchioles

Question 17

How do bronchioles direct air flow?

Answer 17

contain SMOOTH MUSCLE which contracts/relaxes to constrict/dilate airway

Question 18

What are alveoli?

Answer 18

AIR SACS with elastic fibres + collagen

which increase surface area for diffusion

Question 19

What are the features of alveoli and their related functions?

Answer 19

High SA&raquo_space; fast rate of diffusion
1 cell thick squamous epithelium&raquo_space; short diffusion distance
Good blood supply&raquo_space; steep concentration gradient
Good ventilation&raquo_space; steep concentration gradient

Question 20

What are alveoli coated in and what is its function?

Answer 20

lung surfactant

prevents alveolar collapse

Question 21

What is lung surfactant made from?

Answer 21

solution of water + phospholipids,

phospholipids reduce cohesion

Question 22

What is found between the lungs & thorax & what does it do?

Answer 22

pleural fluid,

lubricates & creates vacuum preventing air escape

Question 23

How does ventilation occur in the lungs?

Answer 23

DIAPHRAGM & EXTERNAL INTERCOSTAL muscles contract & relax
changes VOLUME & therefore PRESSURE of thorax
causes air to move in/out

Question 24

EXHALATION:

Answer 24

Diaphragm muscle + external intercostal muscle relaxes,
Diaphragm moves up + ribs fall,
volume of thorax ￬, so pressure ￪,
pressure outside < pressure inside so air moves out

Question 25

INHALATION:

Answer 25

Diaphragm muscle + external intercostal muscle contract,
Diaphragm moves down + ribs rise,
volume of thorax ￪, so pressure ￬,
pressure outside > pressure inside so air moves in

Question 26

Internal intercostal muscles are found on the interior, and only contract during…

Answer 26

forced exhalation

Question 27

What happens during an asthma attack?

Answer 27

cells lining bronchioles release HISTAMINES,
stimulate GOBLET CELLS to produce more mucus & SMOOTH MUSCLE to contract,
swelling + inflammation&raquo_space; less air flow to alveoli