Digestive System Overview

Key Functions

• Regulation of satiety and hunger
• Mechanical digestion (mastication)
• Swallowing and chemical digestion of food
• Absorption of necessary nutrients
• Elimination of unnecessary matter and waste

Components

Primary Organs

• Mouth: Initiates digestion with teeth, salivary glands (enzymes for sugar and fat digestion), and tongue.
• Pharynx: Conducts food to the esophagus.
• Esophagus: Muscular tube with sphincters controlling entry and exit to stomach.
• Stomach: Secretes gastric acid for protein digestion; converts bolus to chyme.
• Small Intestines:
  • Duodenum: Mixes chyme with bile and bicarbonates to activate enzymes.
  • Jejunum: Absorbs nutrients.
  • Ileum: Absorbs vitamin B12 and bile salts.
• Large Intestine:
  • Cecum: Connects small to large intestines.
  • Colon: Absorbs water, stores feces.
• Rectum: Holds feces for elimination.
• Anal Canal: Passage for undigested food and waste.

Accessory Organs

• Salivary Glands: Secrete enzymes for digestion.
• Liver: Detoxifies, produces bile, regulates metabolism.
• Gallbladder: Stores and releases bile.
• Pancreas: Secretes insulin and digestive enzymes.

Neurovascular Supply

• Arterial Supply:
  • Celiac trunk, superior and inferior mesenteric arteries supply the digestive organs.
• Innervation:
  • Parasympathetic: Vagus nerve and pelvic splanchnic nerves.
  • Sympathetic: Thoracic and lumbar splanchnic nerves.
• Venous Drainage:
  • Portal venous system to liver, systemic venous system via hepatic veins.

Digestive Process Details

Trigger and Initiation

• Begins in the brain via hunger centers in the hypothalamus.

Mastication

• Involves teeth and muscles of mastication (masseter, pterygoids, temporalis).

Swallowing and Physical Digestion

• Reflex arc involving cranial nerves, multiple muscle actions.
• Prevents bolus entry into nasopharynx and airway.

Chemical Digestion

• Enzymes in stomach and accessory organs aid in digestion.
• Stomach as storage, mixer, conduit, and defense organ.

Anatomy of Digestive System

Organs

• Buccal Cavity: Contains teeth and tongue.
• Pharynx: Connects oral cavity to esophagus.
• Esophagus: Conducts food to stomach.
• Stomach: Divided into fundus, body, antrum, pylorus.
• Small Intestines: Duodenum, jejunum, ileum.
• Colon: Ascending, transverse, descending, sigmoid.
• Rectum: Holds stool for excretion.
• Anal Canal: Pathway for waste exit.

Accessory Digestive System

• Salivary Glands: Parotid, submandibular, sublingual.
• Liver: Produces bile, processes nutrients.
• Gallbladder: Stores bile.
• Pancreas: Produces digestive enzymes and hormones.

Examination

• Involves inspection, palpation, percussion, auscultation.
• Identifies gastrointestinal pathologies.

Additional Resources

• Anatomical terminology videos.
• Interactive quizzes and study tools.

Mnemonic

• Dow Jones Industrial Average Closing Stock Report: Duodenum, Jejunum, Ileum, Appendix, Colon, Sigmoid, Rectum.