F.1 STRUCTURE AND FUNCTIONS OF THE UPPER DIGESTIVE TRACT

Alimentary Canal

Also known as the gastrointestinal tract; the entire pathway food travels through during digestion.

Physical Digestion

The process of breaking down food into smaller pieces without chemical change, such as chewing.

Exocrine Glands

Glands that release their secretions through ducts to the outside of the body or into a cavity.

Salivary Amylase

An enzyme in saliva that begins the chemical digestion of starches into sugars.

Bolus

A mass of chewed food that is formed by the tongue and ready to be swallowed.

Muscularis

The layer of smooth muscle that lines the digestive tract and helps move food through it.

Peristalsis

The wave-like muscle contractions that move food through the esophagus and digestive tract.

Epiglottis

A flap of tissue that covers the opening of the trachea during swallowing to prevent food from entering the airway.

Cardiac Sphincter

A muscular constriction at the base of the esophagus that controls the entry of food into the stomach.

Gastric Processes

The processes that occur in the stomach for digestion, including churning and mixing food with gastric juices.

Rugae

Folds in the stomach's inner layers that allow it to expand when filled with food.

Mechanoreceptors

Nerve endings in the stomach that sense the presence of food and trigger digestive responses.

Gastrin

A hormone released by G-cells that stimulates the secretion of gastric juices in the stomach.

Endocrine Cells

Cells that release hormones directly into the bloodstream without the use of ducts.

Gastric Juice

A mixture of water, HCl, and pepsinogen produced by the stomach for digestion.

Pepsinogen

The inactive precursor of the digestive enzyme pepsin, which is activated by acidic conditions.

Acid Chyme

The semi-fluid mass of partly digested food that moves from the stomach to the small intestine.

Mucous-secreting Cells

Cells in the mucosal layer that produce mucus to protect the stomach lining.

Pyloric Sphincter

A muscular valve at the end of the stomach that regulates the flow of acid chyme into the duodenum.

Duodenum

The first part of the small intestine, where acid chyme is further digested.

Protease

An enzyme that breaks down proteins into smaller peptides and amino acids.

Mucosa

The innermost layer of the digestive tract that directly interacts with food materials.

Submucosa

A layer of connective tissue surrounding the mucosa in the digestive tract, containing blood vessels and nerves.

Serosa

The tough outer layer of epithelial cells that cover the muscles of the digestive tract.

Longitudinal Muscles

The outer layer of muscles in the muscularis that run lengthwise and help shorten and extend the digestive tract.

Circular Muscles

The inner layer of muscles in the muscularis that encircle and constrict the digestive tube.

Churning

The mixing action in the stomach that combines food with gastric juices to aid in digestion.