Anatomy and Physiology - The Lungs

The Lungs

The Larynx:

• Part of the vocal cords and is located between the pharynx and the trachea.
• It is made up of cartilage.

The Lungs:

• There are two and they are surrounded by the plural membrane.
• The lungs are divided up into lobes; two on the left and three on the right.

The Trachea:

• Connects the larynx with the bronchus and progressively into the smaller dimensions called the bronchiole.
• It is a flexible fibro elastic and muscular structure which allows the neck to move.
• Allows the transport of oxygen from the atmosphere to the lungs and carbon dioxide from the lungs into the atmosphere.
• It is strengthened by rings of cartilage to prevent it come collapsing.
• Contains cilia and mucus, which are hair like structures which traps dust and bacteria which is within the air, as it passes down the trachea.

Ciliated Lining:

• A collection of fine hairs that cover the inside of the trachea.
• They help to trap small particle and foreign bodies. 
• Move in waves in one direction back up towards the head.
• Goblet cells / mucus moving, wafting.

The Bronchus:

• It splits into two tubes and so enables air to pass into both lungs.
• Cells in the bronchi contain cilia to trap pathogens and prevent disease.
• It splits into smaller divisions called the bronchioles.

The Bronchioles:

• They are tiny tubes within the lungs.
• They are connections of the bronchus.
• The bronchioles are attached to tiny air sacs called the alveoli, where gas exchange takes place by the use of diffusion into the pulmonary capillaries. 

The Alveoli:

• They are very thin – only one cell thick (epithelium).
• They have a large surface area to volume ratio.
• They are moist to assist with the diffusion of gases.
• Their function is gas exchange.
• Small air sacs that allow the diffusion of oxygen across their membrane into red blood cells in the surrounding capillaries.
• They also allow the diffusion of carbon dioxide from the blood plasma to diffuse back into the alveoli.
• Elasticised tissue to allow expansion.

Pleural Membranes:

• They are lubricated and surround the whole lungs to keep them moist.
• Without the pleural membranes, the lungs would face resistance and friction from the chest wall while they are expanding and contracting, which may cause shortness of breath ect.

The Diaphragm:

• It is a sheet of internal muscle.
• It is dome shaped when relaxed.
• Extends across the bottom of the rib cage.
• Divides the lungs and hearth from the stomach, kidney, liver etc.
• Helps with the mechanism of breathing.
• The intercostal muscles help bring enlargement of the thorax.
• A large dome shaped muscle that contracts and relaxes causing the chest cavity to increase and decrease in volume allowing the lungs to expand and contract (breathing).
• Changes pressure / maintains pressure within the lungs. 

Mechanisms of Breathing

This is done by two processes:

• Inspiration - breathing in.
• Expiration - breathing out.

These processes rely on pressure changes within the lungs, these are controlled by two sets of muscles:

• The diaphragm:
• A…