mammilian gas exchange and ventilation

What do the ribs do

Protect the lungs and heart

What are the parts of the gas exchange system

Nasal cavity, trachea, intercostal muscles, diaphragm, plural membrane, larynx, bronchus, bronchioles, alveoli

What is the structure of the nasal cavity

Large SA, good blood supply, hairy and moist surface

What is the function of the nasal cavity

Warms air as it enters body, trap dust or pathogens in mucus to prevent reaching lungs, increase humidity of air to reduce evaporation of moisture in lungs

What is the structure of the trachea/bronchi

Supported by incomplete rings of cartilage, lined in ciliated epithelial cells and goblet cells

What is mucus made of

Mucin

What is the function of the trachea/bronchi

Hold the trachea open to prevent it from collapsing, prevent dust and pathogens enter ring lungs

Why are the cartilage rings around the trachea and bronchi incomplete

Allow flexibility when swallowing food down oesophagus

What us the structure of the bronchioles

1mm diameter, held by smooth muscle instead of cartilage, lined in ciliated epithelial cells to allow gas exchange

What is the function of the bronchioles

Smooth muscle contracts to constrict bronchioles and relaxes to allow dilation

What is the structure of the alveoli

200-500 micro meter diameter, thin layer of epithelial tissue with some collagen and elastic tissue

What is the function of alveoli

Most gas exchange here, elastic fibres allow stretching when drawing air in and recoil to push air out

What is inspiration

Breathing in, active process

What happens in inspiration

Diaphragm contracts, external intercostal muscles contract to move ribs up and out, internal intercostal muscles relaxes, thoracic volume increases, thoracic pressure decreases, airflow into lungs to equalise pressure difference

What us expiration

Breathing out, passive process

What happens in expiration

Diaphragm relaxes and moves up, external intercostal muscles relax to move ribs down and in, thoracic volume decreases, thoracic pressure increases, airflow out of lungs

When are the internal intercostals used in expiration

In forced expiration

How does the alveoli support itself

Lung surfactant is a phospholipid that coats the lung surface, without it the waterery lining of alveoli would create surface tension and result in collapsing