Digestive System Lecture Notes

Flashcards covering the components, structure, and functions of the human digestive system, including the alimentary canal, accessory organs, and biochemical processes.

Oral Cavity

Site of mechanical processing, moistening, and mixing with salivary secretions.

Salivary Glands

Exocrine organs that secrete lubricating fluid containing enzymes to break down carbohydrates.

Pharynx

Muscular region that propels materials into the esophagus; divided into nasopharynx, oropharynx, and laryngopharynx.

Esophagus

A food passageway posterior to the trachea that transports materials to the stomach.

Liver

Organ responsible for the secretion of bile, storage of nutrients, and detoxification.

Gallbladder

An organ that stores and concentrates bile until it is regulated for release by cholecystokinin.

Stomach

Organ where chemical breakdown occurs via acid and enzymes, and mechanical processing via muscular contractions.

Pancreas

Organ with exocrine cells that secrete buffers and digestive enzymes, and endocrine cells that secrete hormones.

Large Intestine

The site of dehydration and compaction of indigestible materials in preparation for elimination.

Small Intestine

The primary site for enzymatic digestion and absorption of water, organic substrates, vitamins, and ions.

Mucosa

The inner lining of the alimentary canal consisting of mucosal epithelium, lamina propria, and muscularis mucosae.

Submucosa

A layer of dense irregular connective tissue in the alimentary canal wall.

Muscularis Externa

The layer of the digestive tract wall dominated by smooth muscle cells.

Serosa

A serous membrane that covers the muscularis externa; also known as visceral peritoneum.

Peritoneum

A broad serous membrane with two regions: the parietal peritoneum lining the abdominal wall and the visceral peritoneum enveloping abdominal organs.

Lingual Lipase

An enzyme secreted by lingual glands that breaks down triglycerides into fatty acids and diglycerides after activation in the stomach.

Intrinsic Factor

A substance secreted by parietal cells in the stomach required for the absorption of vitamin $B_{12}$ in the small intestine.

Ingestion

The process of taking food into the body by the mouth.

Mastication

The mechanical process of chewing food.

Digestion

The chemical breakdown of food into smaller components.

Absorption

The movement of nutrients from the digestive tract into the blood or lymph vessels.

Peristalsis

The coordinated contraction of circular and longitudinal muscles that propels materials along the digestive tract.

Bolus

A small, rounded mass of food prepared for swallowing.

Chyme

A mixture of food and gastric juices formed in the stomach.

Parotid Gland

A salivary gland located inferior to the zygomatic arch that secretes salivary amylase.

Sublingual Gland

A salivary gland located on the floor of the mouth that secretes mostly mucus.

Submandibular Gland

A salivary gland located on the inner surface of the mandible that secretes mucins and some amylase.

Deciduous Teeth

The first set of teeth, also known as primary teeth, typically erupting between $6$ and $24$ months.

Enamel

The hard, protective outer covering of the crown of a tooth.

Deglutition

The physiological act of swallowing, consisting of buccal, pharyngeal, and esophageal phases.

Rugae

Folds in the mucosa of the stomach that allow for expansion.

Chief Cells

Stomach cells that secrete pepsinogen, which is converted to the enzyme pepsin.

Parietal Cells

Stomach cells that secrete $HCl$ and intrinsic factor.

G-cells

Endocrine cells in the stomach that secrete the hormone gastrin.

Ghrelin

A hormone produced by the stomach mucosa (mainly fundus) that regulates food intake by stimulating hunger.

Duodenum

The shortest region of the small intestine ($1\,foot$) that begins at the pyloric sphincter.

Jejunum

The middle segment of the small intestine, extending from the duodenum to the ileum, measuring about $8\,feet$.

Ileum

The final and longest segment of the small intestine ($12\,feet$) that connects to the cecum via the ileocecal valve.

Lacteal

A lymphatic capillary found within each intestinal villus for the absorption of lipids.

Microvilli

Cylindrical cell surface structures that form the brush border, with about $200\,million$ per square mm.

Cecum

The first portion of the large intestine where the appendix is attached.

Hepatocytes

The primary functional cells of the liver.

Kupffer Cells

Phagocytic cells located in the liver sinusoids.

Bilirubin

A green breakdown product of red blood cells excreted in bile.

Pancreatic Juice

A mixture of water, salts, sodium bicarbonate, and enzymes such as amylase, lipase, and nuclease.