Human Gaseous Exchange System

Question 1

Nose/ Nasal Cavity

Answer 1

• large surface area with a good blood supply which warms the air to body temperature
• a hairy lining, which secretes mucus to trap dust and bacteria protecting delicate lung tissue from irritation and infection
• moist surfaces, which increase the humidity of the incoming air, reducing evaporation from the exchange surfaces

Question 2

Trachea

Answer 2

It is a wide tube supported by C shaped ring of strong, flexible cartilage which stop the trachea from collapsing. The trachea and its branches are lined with a ciliated epithelium, with goblet cells between and below the epithelial cells.

Question 3

Ciliated Cells

Answer 3

They are cells covered in tiny hair like structures which waft together. They move mucus containing trapped dust and microbes up to the throat

Question 4

Bronchus

Answer 4

In the chest cavity the trachea divides to form the left bronchus and the right bronchus. They are similar in structure to the trachea, with the same supporting rings of cartilage, but they are smaller.

Question 5

Bronchioles

Answer 5

In the lungs the bronchi divide to form many small bronchiole. Only the longest have cartilage. The walls of the bronchioles contain smooth muscle. When the smooth muscle contracts, the bronchioles constrict. When it relaxes, the bronchioles dilate. This changes the amount of air reaching the lungs. Bronchioles are lined with the thin layer of flattened epithelium, making some gaseous exchange possible.

Question 6

Alveoli

Answer 6

They are thin-walled, moist air sacs in the lungs. They consist of a layer of thin, flattened epithelial cells, along with some college and elastic fibres. These elastic tissues allow the alveoli to stretch as air is drawn in. When they return to their resting size, they help to squeeze the air out. This is known as the elastic recoil of the lungs.

Question 7

Ribs

Answer 7

Protect the lungs and have intercostal muscles between them to execute breathing/ ventilation.

Question 8

External Intercostal Muscles

Answer 8

INHALATION: contracts to raise ribs
EXHALATION: relax to lower ribs

Question 9

Internal Intercostal Muscles

Answer 9

INHALATION: ?
EXHALATION: contract further to force out more air

Question 10

Diaphragm

Answer 10

INHALATION: flattens and contracts
EXHALATION: relaxes and is pushed up

Question 11

Pulmonary vein

Answer 11

Thin walled blood vessel carrying blood at low pressure. Takes oxygenated blood from the lungs back to the heart

Question 12

Pulmonary Artery

Answer 12

Thick walled blood vessel carrying blood at high pressure. Delivers deoxygenated blood to alveoli to exchange CO2 for O2 (only artery with deoxygenated blood).

Question 13

Goblet Cells

Answer 13

Differentiated cells specialised to secrete mucus.

Question 14

Surfactant

Answer 14

Chemical mixture containing phospholipids and both hydrophilic and hydrophobic proteins, which coats the surfaces of the alveoli and prevents them from collapsing after every breath.