Human Respiratory System and Gas Exchange Mechanisms

Large surface area

To maximize O2 exchange.

Moist surface area

For diffusion.

Ventilation Mechanism

Force O2 across respiratory surface.

Breathing

An important process that forces O2 across the gas exchange surface.

Air movement

Air moves from a region of high pressure to a region of low pressure until equilibrium is reached.

Nose hair

Filters dust from air.

Capillaries close to surface

Warm the air.

Mucus

Moistens the air.

Pharynx

Opening to the digestive system and the gas exchange system (trachea).

Epiglottis

Closes over trachea when swallowing to prevent choking.

Larynx

Voice box.

Mucus/Cilia

Move dust and foreign particles out of lungs.

Cartilage Rings

Maintain an open airway.

Bronchi

Two branches of the trachea that further branch into bronchioles.

Alveoli

Actual site of gas exchange; grape-like cluster of tiny sacs at the end of each bronchiole.

Alveoli wall

One cell thick to facilitate gas diffusion.

Inhaled Air composition

~20.94% O2 and ~0.04% CO2.

Exhaled Air composition

~16.49% O2 and ~4.49% CO2.

Pleural membrane

Surrounds lungs with two layers and lubricating fluid between them.

Right lung

Contains 3 lobes.

Left lung

Contains 2 lobes.

Medulla Oblongata

Regulates breathing based on CO2 concentrations in the brain and arterial blood.

Bronchioles

Muscles sensitive to CO2 levels that dilate to increase air reaching alveoli.

Oxygen Receptors

Located in the aorta and carotid arteries, stimulate the medulla oblongata when O2 levels are low.

Carbon Monoxide (CO)

Invisible, odourless, tasteless gas that binds tightly to hemoglobin on RBCs, preventing O2 transport.

Symptoms of CO poisoning

Short-term: Headaches, weakness, dizziness; Long-term: damage to organs, coma, death.