7.2 Mammilian Gaseous Exchange System Flashcards Preview

Biology Module 3 > 7.2 Mammilian Gaseous Exchange System > Flashcards

Flashcards in 7.2 Mammilian Gaseous Exchange System Deck (13):

What are the key features of the nasal cavity?

Large surface area with good blood supply, which warns the air to body temperature

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


Describe, in detail, the structure of the trachea

Main airway

Wide tube supported by incomplete rings of strong, flexible cartilage

Trachea and its branches are lined with a ciliated epithelium, with goblet cells between and below the goblet cells


Explain the purpose of the cartilage in the trachea

Stops the trachea from collapsing

Rings are incomplete so food can move easily down the oesophagus behind the trachea


Describe the roles of the goblet cells and epithelial cells in the trachea and branches

Goblet cells = secrete mucus to trap dust and micro organisms

Cilia = beat and move the mucus along with any trapped dirt and microorganism away from the lungs

Then it is either swallowed or coughed up


Describe the positioning and structure of the bronchus

In the chest cavity the trachea divides to form the left bronchus leading to the left lung and the right bronchus leading to the right lung.

Similar in structure to trachea with same supporting rings of cartilage, but smaller.


Describe the positioning and structure of the bronchioles

The bronchi divide to from many bronchioles.

These have no cartilage.

Diameter = 1 mm or less

Walls contain smooth muscle.

Bronchioles are lined with a thin layer of flattened epithelium, making some gaseous exchange possible.


How do bronchioles control how much air reaches the lungs

When the smooth muscle contracts, the bronchioles constrict.

When it relaxes, the bronchioles dilate.

This changes the amount of air reaching the lungs.


Describe the structure of alveoli

Tiny air sacs = main gas exchange surfaces of the body

Diameter = 200-300 um

Layer of thin, flattened epithelial cells

Has collagen and elastic fibres composed of elastin


Why is elastin important in alveoli?

They allow the alveoli to stretch as air is drawn in.

When the return to their resting size, they help to squeeze air out.

This is known as the elastic recoil of the lungs.


List and explain the main adaptations of the alveoli for effective gaseous exchange.

Large surface area - 300-500 million alveoli per adult lung. SA = 50-75m2

Thin layers - alveoli and capillaries that surround them have walls that are only a single epithelial cell thick = short diffusion distance

Good blood supply - network of 280 million capillaries. Constant flow brings CO2 and carries of O2 = steep concentration gradient

Good ventilation - moves air in and out of alveoli = steep diffusion gradient


What is lung surfactant ?

Makes it possible for the alveoli to remain inflated


What happens when you breathe out ( expire )?

Passive process

Diaphragm relaxes
External intercostal muscles relax
Ribs move down and onwards
Elastic fibres in the alveoli return to normal length

This decreases volume of thorax
Pressure inside is greater than pressure of atmosphere

Air moves out of the lungs until pressure inside and out is equal again


What happens when you breathe in ( inspire )?

Energy using process

Diaphragm contracts , flattening and lowering

External intercostal muscles contract, moving the ribs upwards and outwards

Volume of thorax increase so pressure decreases

Pressure is lower than pressure of atmosphere, so air enters until the pressure equalises