The Mamallian Gaseous Exchange System Flashcards
What features does the nasal cavity have?
• Large SA with 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
• Moist surfaces, increasing the humidity, reducing evaporation from exchange surfaces
Describe the structure of the trachea.
• The main airway of the body supported by incomplete (c-shaped) cartilage rings
• Lined with ciliated epithelium and goblet cells
What is the function of goblet cells in the trachea?
They secrete mucus onto the lining of the trachea to trap dust and microorganisms.
What is the function of cilia in the trachea?
The cilia beat rhythmically (synchronous beating) to move the mucus away from the lungs (most of it goes to the throat and is swallowed and digested).
Describe the structure of the bronchi.
They have a similar structure to the trachea, as they both have the same supportive (incomplete) rings of cartilage.
Describe the structure of the bronchioles.
They, unlike the bronchi and trachea, do not have supportive cartilage rings. The walls of the bronchioles contain smooth muscle. They are lined with a layer of flattened epithelium, making some gaseous exchange possible.
What is the function of the smooth muscle in the bronchioles?
When the smooth muscle contracts, the bronchioles constrict, and when the smooth muscle relaxes, the bronchioles dilate. This changes the volume of air in the lungs.
Describe the structure of the alveoli.
They are tiny air sacs unique to mammalian lungs. Small diameter (around 200-300 micrometers). Consists of a layer of thin, flattened epithelial cells along with some collagen and elastic fibres (made of elastin).
What is the function of the elastic fibres?
These allow the alveoli to stretch as air is drawn in. When they return to resting size, they help squeeze the air out. This is known as elastic recoil of the lungs.
