features of human gas exchange system

structure and functions of nasal cavity

• large surface area and good blood supply which warms the air as it passes

• hair lining- produces mucus to trap dust and bacteria and prevent them from reaching the lungs, could cause infection

• moist surface-increases humidity of incoming air, reduces the evaporation of water in the lungs

structure and function of trachea

• c-shaped rings of cartilage keeps airways open and air resistance low

• prevents collapsing and bursting

• rings are incomplete to allow it to bend when food is swallowed down oesophagus (behind trachea)

trachea lining

• contains ciliated epithelial cell and goblet cells

• CEC: waft mucus out of airways

• GC: produces mucus

epithelial tissues

• airways lined by CEC and GC which secrete mucus

• these cells are positioned on a basement membrane consisting of a network of protein fibres

ciliated epithelium

• usually columnar in shape

• numerous cilia on free surfaces

epithelial tissue- gc

• mucus secreted by goblet cells contains long glycoprotein molecules, making the mucus thick and sticky to coat the epithelium and to trap dust

• cilia then move the mucus up the trachea so that it can be removed form the gas exchange system

bronchus

• irregular blocks of cartilage, not rings

• fewer goblet cells than trachea

• epithelial cells shorter

• elastic fibres beneath epithelium

bronchioles

• no cartilage

• held open by smooth muscle

• can relax or contract to alter diameter of airways

• lined with a thin layer of epithelial tissues making some gas exchange possible

alveoli

• made up of thin layer of flattened epithelial cells, as well as some collagen and elastic fibres

• elastic fibres causes recoil which helps move air out of the alveoli

• surrounded by blood vessels for gas exchange

surfactant

• lung surfactant is phospholipid that coats the surface of the alveoli

• w/o the watery lining of alveoli would create surface tension, which would cause them to collapse

macrophages

• constantly patrol the alveolar surfaces, ready to engulf pathogens or dust particles

• a type of phagocyte

gas exchange in alveoli

1. blood low in oxygen, high in co2

2. co2 diffuses out of blood to exhale

3. gasses dissolve in moist lining

4. oxygen is transported by rbc

5. oxygen diffuses into blood

6. blood low in co2, high in o2

7. air moves in and out of alveolus