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Digestive System and Metabolism - Anatomy & Physiology

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  • What are the four main functions of the digestive system?

    Ingestion - taking in food
    Digestion - breaking food into nutrient molecules
    Absorption - movement of nutrients into the bloodstream
    Defecation - excretion of indigestible waste

  • What are the two main groups of organs in the digestive system?

    Alimentary canal - continuous, coiled, hollow tube for ingestion, digestion, absorption, defecation
    Accessory digestive organs - teeth, tongue, and large digestive organs that assist digestion

  • List the organs of the alimentary canal in order.

    Mouth, Pharynx, Esophagus, Stomach, Small intestine, Large intestine, Anus

  • What are the main anatomical features of the mouth?

    Mouth lined by mucous membrane, lips (labia), cheeks, hard palate (anterior roof), soft palate (posterior roof), and uvula (projection of soft palate)

  • What are the two parts of the mouth cavity?

    Vestibule - space between lips and teeth/gums
    Oral cavity proper - area contained by the teeth

  • What are the two types of tonsils in the mouth?

    Palatine tonsils - pair at posterior oral cavity
    Lingual tonsil - single tonsil at base of tongue

  • What are the functions of the mouth in digestion?

    Mastication (chewing), mixing food with saliva, initiating swallowing, and taste via taste buds on the tongue

  • What is the role of the pharynx in digestion?

    Passageway for food, fluids, and air; food passes through oropharynx and laryngopharynx to esophagus; propels food by peristalsis using two skeletal muscle layers

  • Describe the esophagus and its function.

    About 10 inches long, runs from pharynx to stomach through diaphragm; conducts food by peristalsis; passageway for food only

  • Name the four layers of tissue in the alimentary canal from innermost to outermost.

    1. Mucosa
    2. Submucosa
    3. Muscularis externa
    4. Serosa

  • What is the mucosa composed of in the alimentary canal?

    Innermost moist membrane with surface epithelium (mostly simple columnar except esophagus), lamina propria connective tissue, and scant smooth muscle; lines the lumen

  • What does the submucosa contain?

    Soft connective tissue with blood vessels, nerve endings, mucosa-associated lymphoid tissue (MALT), and lymphatic vessels

  • Describe the muscularis externa layer.

    Smooth muscle with inner circular and outer longitudinal layers

  • What is the serosa and its components?

    Outermost layer containing fluid-producing cells; visceral peritoneum (innermost) and parietal peritoneum (outermost lining abdominopelvic cavity)

  • What are the two intrinsic nerve plexuses in the alimentary canal wall?

    Submucosal nerve plexus and myenteric nerve plexus; regulate mobility and secretory activity of GI tract organs

  • What are the main regions of the stomach?

    Cardia (near heart), Fundus (expanded lateral portion), Body (midportion), Pylorus (funnel-shaped terminal end)

  • What is the function of the rugae in the stomach?

    Internal folds of mucosa that allow the stomach to stretch and hold up to 4 liters of food when full

  • What cells are found in the stomach mucosa and their functions?

    Chief cells - produce pepsinogen (protein-digesting enzyme)
    Parietal cells - produce hydrochloric acid
    Mucous neck cells - produce thin acidic mucus
    Enteroendocrine cells - produce hormones like gastrin

  • What are the three subdivisions of the small intestine?

    Duodenum, Jejunum, Ileum (ends at ileocecal valve)

  • What structural modifications increase the surface area of the small intestine?

    Villi (fingerlike projections), microvilli (brush border), and circular folds (plicae circulares)

  • What are the main functions of the large intestine?

    Absorbs water, vitamins, ions; eliminates feces; houses bacteria that produce vitamin K and some B vitamins

  • What are the major accessory digestive organs?

    Teeth, Salivary glands, Pancreas, Liver, Gallbladder

  • What are the two sets of human teeth and their characteristics?

    Deciduous (baby) teeth - 20 teeth by age 2
    Permanent teeth - 32 teeth replacing deciduous between ages 6-12

  • Classify teeth by shape and function.

    Incisors - cutting
    Canines - tearing/piercing
    Premolars (bicuspids) - crushing/grinding
    Molars - crushing/grinding

  • What are the main components of a tooth?

    Crown (exposed part covered by enamel), Root (covered by cement and anchored by periodontal membrane), Dentin, Pulp cavity (connective tissue, blood vessels, nerves)

  • What enzymes and substances are found in saliva?

    Salivary amylase (begins starch digestion), mucus (moistens and binds food), lysozymes and antibodies (inhibit bacteria)

  • What are the digestive and hormonal functions of the pancreas?

    Produces digestive enzymes for all food categories; secretes alkaline fluid to neutralize chyme; produces insulin and glucagon hormones

  • What is the role of the liver in digestion?

    Produces bile which emulsifies fats; detoxifies drugs and alcohol; produces cholesterol and blood proteins; plays central role in metabolism

  • What is bile composed of and its function?

    Yellow-green watery solution with bile salts, bile pigments (bilirubin), cholesterol, phospholipids, electrolytes; emulsifies fats for digestion

  • What is the function of the gallbladder?

    Stores and concentrates bile; releases bile into duodenum when fatty food enters

  • What are the six essential processes of the gastrointestinal tract?

    1. Ingestion
    2. Propulsion (peristalsis)
    3. Mechanical breakdown
    4. Chemical digestion
    5. Absorption
    6. Defecation

  • What are the two phases of swallowing?

    Buccal phase - voluntary, food formed into bolus and pushed to pharynx
    Pharyngeal-esophageal phase - involuntary, peristalsis moves bolus to stomach

  • What regulates gastric juice secretion in the stomach?

    Neural and hormonal factors; hormone gastrin released by rising pH or food presence stimulates secretion of enzymes, mucus, and hydrochloric acid

  • What are the main enzymes involved in protein digestion in the stomach?

    Pepsin (active enzyme from pepsinogen) and rennin (digests milk protein in infants)

  • What enzymes digest carbohydrates, proteins, fats, and nucleic acids in the small intestine?

    Pancreatic amylase (starch), trypsin/chymotrypsin/carboxypeptidase (proteins), lipases (fats), nucleases (nucleic acids)

  • What hormones regulate pancreatic juice and bile secretion?

    Secretin and cholecystokinin (CCK) stimulate pancreas, liver, and gallbladder

  • How are nutrients absorbed in the small intestine?

    Most by active transport through mucosal cells into blood or lymph; lipids absorbed by diffusion

  • What are the main functions of the large intestine in digestion?

    No digestive enzymes produced; bacteria digest remaining nutrients and produce vitamins; absorbs water, vitamins, ions; eliminates feces

  • What is metabolism and its two main types?

    All chemical reactions to maintain life; catabolism breaks down substances releasing energy; anabolism builds larger molecules from smaller ones

  • What are the three main metabolic pathways of cellular respiration?

    Glycolysis (cytosol), Citric acid cycle (mitochondria), Electron transport chain (mitochondria)

  • What is the role of the liver in glucose homeostasis?

    Glycogenesis (stores glucose as glycogen), Glycogenolysis (releases glucose), Gluconeogenesis (makes glucose from fats and proteins)

  • What are LDLs and HDLs in cholesterol transport?

    LDLs (low-density lipoproteins) transport cholesterol to body cells (bad lipoproteins)
    HDLs (high-density lipoproteins) transport cholesterol from cells to liver for breakdown (good lipoproteins)

  • What factors influence basal metabolic rate (BMR)?

    Surface area, gender, age, thyroxine production, emotions, infections

  • How does the hypothalamus regulate body temperature?

    Initiates heat loss (radiation, sweating) or heat-promoting (vasoconstriction, shivering) mechanisms to maintain homeostasis