Digestive

• Digestive System Functions

  • Food intake
  • Digest food into molecules
  • Absorb nutrients
  • Compacts and excretes waste
• (1) Gastrointestinal Tract

  • Mouth
  • Pharynx
  • Esophagus
  • Stomach
  • Small Intestine
  • Large Intestine
  • Anus
• (2) Accessory Organs

  • Teeth
  • Tongue
  • Salivary Glands
  • Liver
  • Gallbladder
  • Pancreas
• Walls of the Digestive Tract

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

  • Epithelium
  • Stratified squamous: Mouth and Esophagus
  • Columnar: Remainder of tract
• Submucosa

  • Connective tissue
  • Blood vessels, nerves
• Muscularis

  • Two layers of smooth muscle
  • Movement and mixing
• Peristalsis

  • Waves of muscle contraction that propel bolus through digestive tract
• Segmentation

  • Cycles of contraction that fragment bolus
  • occurs in many areas of small intestine and some areas of large intestine
• Serosa

  • Serous membrane that covers the outside of abdominal organs
  • AKA “Visceral Peritoneum”
• Peritoneum

  • serous membrane
  • lining abdominal cavity
  • covering abdominal organs
• Structures of the Peritoneum

  1. Parietal layer
  2. Visceral layer
  3. Perioneal space
• Mesentery: a fold of the peritoneum which attaches the stomach, small intestine, pancreas, spleen, and other organs to the posterior wall of the abdomen.
• Greater Omentum

  • Peritoneum extension
  • "abdominal apron"
  • protects surfaces of abdomen
  • insulation
  • lipid reserves
• Buccal Cavity

  • Mouth
• Mouth Functions

  • Mechanical digestion
  • Enzymatic digestion
• Teeth

  • Mechanical digestion - chewing
  • Deciduous - 20, 6 months
  • Permanent - 32, 6 years
• Salivary Glands

  • Parotid
  • Submandibular
  • Sublingual
  • Enzyme: Amylase
• Tongue

  • Move food for chewing
  • Shape food into rounded bolus
  • Initiate swallowing
• Swallowing

  • Deglutition
  • 3 Stages: Voluntary, Pharyngeal, Esophageal
• Esophagus

  • Food from pharynx to stomach
  • Peristalsis ensures stomach destination
  • Two sphincters: UES, LES
• Stomach Regions

  1. Cardia
  2. Fundus
  3. Body
  4. Pylorus
• (3) Stomach muscles macerate food and mix it with gastric juice, forming chyme.
• Stomach Structures

  1. Rugae
  2. Pyloric sphincter
  3. Gastric glands
• Gastric Glands

  • Parietal cells secrete HcL, Intrinsic factor
  • Chief cells secrete pepsinogen
  • Mucous cells secrete mucous
• Small Intestine

  • Digestion completes
  • End products are absorbed
  • Duodenum, jejunum, ileum
• Small Intestine - Structures

  • Intestinal Glands
  • Plicae circulares
  • Villi
  • Microvilli
• Intestinal Gland Secretions

  • Maltase - breakdown sugar
  • Sucrose - inverts into fructose, glucose
  • Lactase - digest lactose (weaning)
  • Peptidase - deactivates peptides
• Duodenum

  • Receives secretions from Liver, Gall Bladder, Pancreas
• Liver

  • Bile for emulsification of fats
• Gall Bladder

  • Stores, concentrates bile
  • Cholecystokinin (secretion of bile)
• Pancreas

  • Alkaline substance
  • Lipase
  • Amylase
  • Trypsin
• Large Intestine

  • Reabsorption of water, vitamins
  • Compaction of feces
  • Storage of feces
• Large Intestine - Structures

  • Cecum
  • Ascending colon
  • Transverse colon
  • Descending colon
  • Sigmoid
  • Rectum
  • Anus
• Ileocecal Valve

  • prevents the backflow of fecal material from cecum to ileum
• Rectum

  • Expandable feces storage
  • Fecal matter triggers defecation urge
  • Mass peristalsis
• Anal Canal

  • Internal anal sphincter
  • External anal sphincter
  • Anus
• End products of digestion

  • Carbs - Monosaccharides
  • Fats - Fatty Acids, Glycerol
  • Proteins - Amino Acids
• Emulsification

  • Physical digestion of fats
  • Bile
• Hydrolysis

  • Chemical digestion of fats
  • Pancreatic lipase