Tissues in the Gaseous Exchange System

Question 1

Tissues in the Gaseous Exchange System

Answer 1

Alveoli:
Airways (trachea, bronchi, bronchioles):
Smooth muscle and elastic tissue:

Question 2

Alveoli:

Answer 2

Alveoli are composed of squamous epithelium and are surrounded by blood capillaries, so gas diffusion distance is short. Alveolus walls contain elastic fibres that stretch (deform) during inspiration and recoil (to original size) in expiration.
(Note: alveolar epithelium is so thin, they may not be able to be distinguished under light microscopes).

Question 3

Airways (trachea, bronchi, bronchioles):

Answer 3

Walls composed of smooth muscle & elastic fibres, cartilage, Ciliated epithelium (cilia & goblet cells).
•Must be large enough to allow sufficient air flow without obstruction.
•Must be supported to prevent collapse when air pressure inside is low during inspiration.
•Must be flexible to allow movement.

The airways are lined with ciliated epithelium (a layer of cells that have many cilia), which help keep airways clean. Goblet cells in the epithelium secrete mucus. which traps pathogens and other irritants le.g. dust_. the cilia then waft mucus up to the top of the trachea, where it is swallowed to prevent infections.
• Trachea and bronchi: These airways are supported by rings of cartilage, which prevent collapse during inspiration.
C-shaped rather than rings to allow flexibility and space for food to pass down the oesophagus.
•Bronchioles: Larger bronchioles may have cartilage. Very smallest may not have smooth muscle.

Question 4

Smooth muscle and elastic tissue:

Answer 4

•Smooth muscle contracting restricts the airway, making the lumen narrower, and restricting flow of air to/from the alveoli. This is important if there are harmful substances in the air.
•The contraction of smooth muscle is involuntary and be a result of an allergic reaction.
•Once the smooth muscle has contracted it cannot reverse the effect on its own. It is elongated by the elastic fibres, when the muscle contracts, it deforms the elastic fibres.
•As the smooth muscles relax, the elastic fires recoil to their original size & shape, dilating the airway.
•Elastic fibres are stretching during inspiration and recoil to help push air out in expiration.
•During exercise the smooth muscle relaxes making the airways wider (controlling diameter), so there’s less resistance to airflow.

Question 5

Do the tabel

Answer 5

Tabel draw.

Question 6

Practical: Drawing slide of lung tissue to show tissue histology:

Answer 6

Eve protection when using microscopes. Initially view at low power (×40) to select best part of slide and draw tissue plan (contains no individual cells). Then move to high power (x400) and draw a few cells showing as much detail of contents and shape as possible.