Unit D1-Biochemistry and Digestion: Topic 2

Digestion

Ingestion

Taking nutrients into the body

Digestion

The breakdown of the food molecules into smaller molecules

Absorbtion

The transport of digested nutrients to the tissues of the body

Egestion

The removal from the body of portions of the ingested material that cannot be absorbed

Digestive Tract/Alimentary Canal

Places where the food actually runs through the body

Accessory Organs

Those which aid in digestion by secreting but do not actually handle food.

Ex: Salivary Glands, liver, gallbladder, pancreas

Peristalsis

the involuntary, wave-like contraction and relaxation of muscles in the digestive tract that propels food, liquids, and waste forward

Saliva

Dissolves food particles in the mouth which allows for taste and it also lubricates the food for easier swallowing

Amylase

An enzyme that breaks down large carbohydrates into smaller ones (Polysaccarides into disaccharide, ETC)

Bolus

Ball of food that is result of oral digestion (physical & chemical)

Mucous (goblet) Cells

Secrete a mucous lining that protects the stomach wall from enzymes and acids

Parietal Cells

Secrete hydrochloric acid (HCl) which chemically digests matter and activates enzymes (occurs in gut lumen)

Peptic (Chief) Cells

Secrete pepsinogen which is then converted in the stomach to pepsin by hydrochloric acid (HCl). This enzyme begins protein digestion.

What else do Peptic Cells do?

They also secrete rennin which slows down the movement of milk so it can be digested and absorbed, but this isn’t very prevalent in adults

Gastrin

A hormone that causes the stomach to produce more juices.

When are gastric juices produced?

After eating

Gastric Juices include:

Hydrochloric acid (HCl), pepsinogens, mucous, & more

Chyme

a mixture of food, saliva, and gastric juices

Why aren’t most substances from the chyme absorbed in the stomach?

Most of the substances present in the chyme aren’t fully broken down yet

Hiatal Hernia

-Caused by the stomach protruding through the diaphragm

-Identified by a discomfort after eating

-Can be solved surgically

Ulcers

-Caused by low mucous production in the stomach, usually because of the presence of a bacteria called H. Pylori.

• This allows for the stomach wall to come into contact with stomach acid which burns the wall.

- Treatment includes antibiotics, rest, change in diet

Where does most absorbtion occur?

The small