F.2 STRUCTURES AND FUNCTIONS OF THE LOWER DIGESTIVE TRACT

Acid Chyme

Partially digested food mixed with gastric juices, entering the duodenum.

Duodenum

First section of the small intestine, where acid chyme is received.

Mechanoreceptors

Nerve receptors that respond to physical pressure or distortion.

Pyloric Sphincter

Muscle that controls the passage of chyme from the stomach to the duodenum.

Secretin

A hormone released in response to acid chyme that stimulates digestive processes.

Cholecystokinin (CCK)

A hormone triggered by biomolecules that stimulates bile release from the gallbladder.

Bile

A digestive fluid produced by the liver that emulsifies fats.

Emulsification

Process of breaking down fat clusters into smaller particles for digestion.

Pancreatic Juice

Digestive fluid produced by the pancreas, containing enzymes and buffers.

Sodium Bicarbonate

A buffer in pancreatic juice that neutralizes stomach acid.

Lipase

An enzyme that hydrolyzes lipids into fatty acids and glycerol.

Nucleases

Enzymes that digest nucleic acids into nucleotides.

Pancreatic Amylase

An enzyme that continues the digestion of carbohydrates into maltose.

Protease

Enzymes that break down proteins into peptides.

Peptidases

Enzymes that further cleave peptides into individual amino acids.

Nucleotide

Basic unit of nucleic acids, formed from nucleotides.

Villi

Finger-like projections in the ileum specialized for absorption.

Microvilli

Minute extensions on epithelial cells that increase surface area for absorption.

Lacteal

Lymphatic vessel in the villi that absorbs dietary fats.

Ileocaecal Valve

Sphincter controlling the passage from the ileum to the colon.

Caecum

First segment of the colon, connected to the ileum.

E.coli

Anaerobic bacteria in the colon that aid in digesting organic material.

Feces

Undigested material and waste products excreted from the body.

Rectum

Final section of the large intestine that temporarily stores feces.

Anal Sphincter

Muscle controlling defecation through the anus.

Peristalsis

Involuntary contractions that move chyme through the digestive tract.