Chapter 7 - The Lungs & Alimentary Canal

It helps to maintain a difference in concentrations of oxygen and carbon dioxide in the blood and in the air in the lungs.

So that large amounts of gases can be exchanged in a relatively short time.

So that gas molecules do not have far to travel to move into or out of the blood.

To prevent excessive evaporation of the fluid that covers the respiratory surfaces.

It helps to ensure that there is always a difference in the concentrations of oxygen and carbon dioxide in the air and in the blood.

The process by which air is moved into and out of the lungs.

For air to flow into the lungs, the pressure of air in the lungs must be less than the atmospheric pressure outside the body. This is achieved by increasing the volume of the lungs.

The diaphragm and external intercostal muscles contract, it thus become flatter and the rib cage moves upwards and outwards, increasing the volume of the chest cavity.

Membrane around the lungs.

The diaphragm and external intercostal muscle relax so that the diaphragm bulges more into the chest cavity and the rib cage moves downwards. This reduces the volume which increases the air pressure in the lungs.

Low concentration of Oxygen than the air in the alveolus.

It has a higher concentration than the air in the alveolus

• The constant blood flow through the capillaries. As the blood flowing through the capillaries around each alveolus picks up oxygen and loses carbon dioxide it is replaced by more blood pumped into the capillaries. This ‘new’ blood is low in O2 and high in CO2 so that the concentration gradient is maintained.

It is the continuos tube that runs from the mouth to the anus.

• Ingestion of food and water • Mechanical digestion of food • Chemical digestion of food • Movement of food along the alimentary canal • Absorption of digested food and water into the blood and lymph • Elimination of material that is not absorbed.

Transverse, Ascending and Descending colons. They are the longest part of large intestine. Absorbs water, minerals, vitamins.

• Breaks food into smaller particles by chewing. * Saliva, which contains salivary amylase, begins starch digestion.

It carries food from the mouth to the stomach.

• Waves of contraction churn food. * Gastric juice, which contains pepsin, breaks down proteins to polypeptides.

• Muscular contractions churn food; bile salts emulsify lipids. • Pancreatic juice- contains: pancreatic amylase, which breaks starch into disaccharides; pancreatic protease, which breaks proteins and polypeptides into peptides; pancreatic lipases, which break down lipids into fatty acids and glycerol; and nucleases, which digest DNA and RNA. • Intestinal juice - contains amylase a to break down disaccharides to simple sugars; peptidases to break down peptides to amino acids; and lipases to break down lipids to fatty acids and glycerol.

These are chisel-shaped teeth used for biting or cutting, such as when on takes a bite out of an apple.

Located one on each side of the incisors, these are conical teeth used for tearing. Human canines are the same length as the other teeth.

There are two on each side of the jaw.

Three on each side of the naw, the premolars and molars have broad crowns with rounded cusps. The cusps of the teeth of one jaw fit into depressions on the surface of teeth on the other jaw, making the premolars and molars ideal for crushing and grinding,