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Digestive System Anatomy & Physiology (Chapter 23 Part 1)

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  • Alimentary canal

    Continuous tube through which food passes; includes oral cavity, pharynx, esophagus, stomach, small intestine, and large intestine.

  • Accessory organs of digestion

    Organs that assist digestion but are not part of the alimentary canal; include teeth, tongue, salivary glands, liver, gallbladder, and pancreas.

  • Six major processes of digestion

    Ingestion, propulsion, mechanical breakdown, digestion, absorption, and defecation.

  • Peritoneum

    Largest serous membrane in the body with two layers: parietal peritoneum lining the body wall and visceral peritoneum covering digestive organs.

  • Mesenteries

    Folds of visceral peritoneum that hold digestive organs in place, house blood vessels, nerves, lymphatics, and store fat.

  • Four layers of the GI tract

    Mucosa, submucosa, muscularis externa, and serosa (or adventitia).

  • Mucosa functions

    Secretion, absorption, and protection; lined by stratified squamous epithelium in mouth/esophagus/anus and simple columnar epithelium elsewhere.

  • Submucosa composition

    Areolar connective tissue with blood and lymphatic vessels, submucosal glands, and the submucosal plexus of the enteric nervous system.

  • Muscularis externa structure and function

    Two layers of smooth muscle (inner circular, outer longitudinal) responsible for segmentation and peristalsis; stomach has three layers.

  • Serosa vs Adventitia

    Serosa covers intraperitoneal organs (areolar CT), adventitia covers organs outside abdominal cavity (dense CT).

  • Splanchnic circulation

    Blood supply and drainage of abdominal digestive organs via branches of abdominal aorta and veins draining into hepatic portal vein.

  • Hepatic portal system

    Veins drain digestive organs and deliver blood to liver for processing before returning to inferior vena cava.

  • Enteric nervous system (ENS)

    Intrinsic nervous system of GI tract with over 100 million neurons; includes submucosal and myenteric plexuses controlling motility and secretions.

  • Sympathetic vs Parasympathetic effects on digestion

    Sympathetic inhibits digestive processes; parasympathetic stimulates digestion.

  • Oral cavity functions in digestion

    Site of ingestion, secretion, mechanical breakdown, and propulsion; contains teeth, tongue, and salivary glands.

  • Palate structure

    Hard palate (anterior 2/3) made of stratified squamous epithelium and connective tissue; soft palate (posterior 1/3) made of skeletal muscle with uvula.

  • Tongue muscles

    Extrinsic muscles control position; intrinsic muscles control shape and size; both assist in chewing and bolus formation.

  • Three major salivary glands

    Parotid (serous cells near ear), submandibular (mostly serous, medial mandible), and sublingual (mostly mucous, under tongue).

  • Saliva composition

    97–99.5% water, electrolytes (including bicarbonate), salivary amylase, lysozyme, and secretory IgA.

  • Control of salivation

    Primarily parasympathetic via salivatory nucleus and ACh; sympathetic increases mainly mucous secretions.

  • Teeth function and location

    Located in alveoli of mandible and maxilla, held by periodontal ligament; function in mechanical digestion (mastication) to increase surface area.