Anatomy of the Digestive System - HUAP220

Overview of the Digestive System

• Comprises the gastrointestinal tract (GI tract) and accessory organs.
• GI tract is a continuous tube extending from the mouth to the anus, measuring roughly 5-7 meters in a living person.

Functions of the Digestive System

• Ingestion: Intake of food.
• Propulsion: Movement of food through swallowing and peristalsis.
• Mechanical Breakdown: Chewing and mixing food with saliva to increase surface area.
• Digestion: Enzymatic breakdown of food into molecules.
• Absorption: Transfer of nutrients from the GI lumen to the blood or lymph.
• Defecation: Excretion of indigestible substances as feces.

Components of the Digestive System

• Gastrointestinal Tract: Mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, anal canal.
• Accessory Organs: Teeth, tongue, salivary glands, liver, gallbladder, pancreas.

Layers of the GI Tract

• Mucosa: Innermost layer with epithelium, lamina propria, and muscularis mucosa.
• Submucosa: Contains areolar tissue, blood vessels, lymphatics, and Meissner’s plexus.
• Muscularis Externa: Comprises inner circular and outer longitudinal smooth muscle layers.
• Serosa: The outer visceral peritoneal layer; non-peritoneum-covered organs have adventitia.

Oral Cavity

• Divided into vestibule and oral cavity, lined with stratified squamous epithelium.
• Functions: Chewing, mixing food with saliva, swallowing initiation, and taste sensation via tongue papillae.

Pharynx

• A fibromuscular tube facilitating the passage of air and food.
• Comprised of three sections: nasopharynx, oropharynx, laryngopharynx.

Esophagus

• Muscular tube conducting food from the pharynx to the stomach via peristalsis.
• Contains two sphincters: Upper esophageal and lower esophageal (cardiac) sphincters.

Stomach

• A C-shaped muscular sac with four regions: cardiac, fundus, body, pyloric region.
• Contains three layers of smooth muscle and gastric glands that secrete gastric juice.

Small Intestine

• Major site for nutrient absorption, extending from pyloric sphincter to ileocecal valve.
• Divided into three segments: duodenum, jejunum, ileum, with distinct lengths and locations.

Mucosa of the Small Intestine

• Features circular folds, villi for surface area enhancement, and microvilli.
• Contains Peyer’s patches for immune function.

Large Intestine

• Larger in diameter but shorter than the small intestine; extends from ileocecal valve to anus.
• Regions include cecum (with appendix), colon (ascending, transverse, descending, sigmoid), rectum, anal canal.
• Lacks villi and features mucus-producing goblet cells; has teniae coli and haustra.

Salivary Glands

• Parotid Gland: Largest, secretes saliva into the vestibule.
• Submandibular Gland: Located on the floor of the mouth, secretes saliva via submandibular duct.
• Sublingual Gland: Under the tongue, secretes saliva through small ducts.

Teeth

• Involved in mastication: Incisors and canines for cutting, premolars and molars for grinding.

Tongue

• Composed of skeletal muscle, aiding in mastication, swallowing, and speech.
• Papillae on the tongue contain taste buds for taste sensation.

Pancreas

• Divided into head, neck, body, and tail, with the head located in the duodenal cavity.
• Exocrine function produces pancreatic juice containing digestive enzymes, neutralizing acidic chyme in the duodenum.

This quiz covers the anatomy and function of the digestive system as part of Human Anatomy and Physiology II. You will explore the gastrointestinal tract's components, structures, and accessory glands, as well as the microscopic anatomy involved in digestion. Get ready to test your knowledge on this vital subject!