Ingestion

Ingestion

Taking in nutrients

Digestion

Breakdown of nutrients

Types of digestion

Chemical (enzyme) digestion
Mechanical -

Absorption

Transportation of digested nutrients via blood

Elimination

Removal of undigested waste

Length of human digestive tract

6.5-9m long

Where does digestion begin?

Digestion begins in the mouth where food is chewed to form a bolus.
-Physical (mechanical) digestion

Hardest substance in the body

Enamel which covers the teeth.

Amylase

An enzyme that breaks down carbohydrates in the digestive system.

Saliva

Has 2 functions:
1. Has salivary amylase enzymes
2. Dissolves food particles.
-Lubricates foods, flavor receptors.

Swallowing Reflex

Triggered by food in pharynx
Contractions coordinated by Medulla

Medulla

Part of the brainstem that controls vital functions like breathing.

Esophagus

The tube from mouth to stomach

When a food bolus enters the esophagus:

1. Walls of the esophagus stretch
   2. Peristalsis: smooth muscle that lines the esophagus, and involuntarily contracts to help move food down.

Esophageal Sphincter

A ring-like muscular structure which controls the entry to food entering your stomach.

What is the esophagus separated by?

Gastroesophageal (cardiac) sphincter or valve.

What is the result of a faulty valve?

Heart Burn

Stomach

-J shaped organ
-Site of food storage and initial protein digestion
-Folded layers to increase surface area
-Physically digests food through the churning motion from stomach muscles.

PH of the Stomach

1.0-3.0 (acidic)

Pyloric sphincter

Controls the emptying of stomach contents into the small intestine.

Stomach Secretion

Flashcard: "Stomach Secretion"

• Process of releasing digestive fluids in the stomach

• Includes hydrochloric acid, enzymes, and mucus

• Aids in breaking down food and killing bacteria

Autocatalysis

A chemical reaction that speeds up due to the presence of its own product. It acts as a catalyst for its own formation, leading to an exponential increase in the reaction rate.

Pepsinogen (chief cells)

It is the inactive form of pepsin, an enzyme that helps break down proteins during digestion.

Chemical reaction of pepsinogen and HCL

The process where pepsinogen and HCl combine to form pepsin. Pepsinogen, an inactive enzyme, is activated by HCl in the stomach. Pepsin then breaks down proteins into smaller peptides. This chemical reaction aids in the digestion of food in the stomach.
-Stomach pH can drop to 2-3

Common stomach problems

Gastritis
Peptic ulcers

Gastritis

A stomach problem due to inflammation of the tissue, can be caused due to aspirin and alcohol.

Peptic ulcers

The mucous later in the stomach breaks down
-Stomach acid makes contact with the stomach wall causing holes, and acid burns.
Caused by bacteria, and diet and stress.

Ulcers

Most commonly caused by a Helicobacter pylori infection.
-Long period of NSAIDS for example advil.

Gastric Juices

Flashcard: Gastric Juices

• Secreted by the stomach lining

• Contains hydrochloric acid, pepsinogen, and mucus

• Helps break down food and kill bacteria

• Acidic pH aids in digestion and activates pepsinogen to pepsin

• Mucus protects stomach lining from acid damage

Chyme

Chyme: Partially digested food mixed with gastric juices in the stomach. It is a thick, soupy substance that moves from the stomach to the small intestine for further digestion and absorption of nutrients.

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