HOME
Front page
Credits
Links
MyBodyIndex:
Human Body Guide
Nutrient Guide
Disorder Guide
Remedies & Therapies
The Human Body:
|
Respiratory Passage
diagram 7.1 respiratory system
The respiratory system consists of the nostrils, nasal passage, windpipe, bronchi, bronchiole, alveoli, lungs. As one breathes in through the nose, the air becomes moist and warm. This aids the lungs to absorb the oxygen. There is a mucous lining which is sticky to trap dust particles. The air is then further cleaned as it passes through the small hairs(cilia) in the nasal cavities and passage in which the dirt is carried to the throat to be swallowed/coughed/spat out, the clean air is then passed down the pharynx at the back of the throat(voice production area). A small flap named the epiglottis opens to allow the air to pass through. It closes when eating to prevent food from entering the windpipe which will cause choking. The windpipe(trachea) is protected by C-shaped bands of gristle called cartilage. The air soon passes into 2 bronchi which leads to the lungs. The tubes then divide into smaller passages called bronchioles. They will then end in little bunches of hollow sacs named alveoli which fills with air as one breathes in. They are only 2 cell thick so that oxygen and carbon dioxide exchange can be done so easily and rapidly.
Within the alveolus, oxygen in the inhaled air dissolves in the moisture of the alveolar epithelium. It diffuses across the alveolar membrane that has a 1cell layer of the alveolar epithelium and the other layer 1 cell layer of the capillary endothelium. It then passes into the blood plasma. It combines with haemoglobin in the erythrocyte to form oxyhaemoglobin and transported to tissues to maintain the oxygen diffusion gradient. Carbon dioxide diffuses in the reverse direction.
The essential diffusion gradient is maintained by lung ventilation, blood flow, haemoglobin combining rapidly with oxygen and the release of carbon dioxide from the blood plasma. The gaseous exchange is facilated by the greater exposure of the erythrocyte surface as the cell squeezes through the capillaries and the slow progress of the erythrocytes through the capillarieds.
|