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Digestive System Anatomy. Digestive tract Alimentary tract or canal GI tract Accessory organs Primarily glands Regions Mouth or oral cavity Pharynx Esophagus Stomach Small intestine Large intestine Anus. Digestive Tract Histology. Nervous regulation Involves enteric nervous system

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digestive system anatomy
Digestive System Anatomy
  • Digestive tract
    • Alimentary tract or canal
    • GI tract
  • Accessory organs
    • Primarily glands
  • Regions
    • Mouth or oral cavity
    • Pharynx
    • Esophagus
    • Stomach
    • Small intestine
    • Large intestine
    • Anus
digestive system regulation
Nervous regulation

Involves enteric nervous system

Types of neurons: sensory, motor, interneurons

Coordinates peristalsis and regulates local reflexes

Chemical regulation

Production of hormones

Gastrin, secretin

Production of paracrine chemicals

Histamine

Help local reflexes in ENS control digestive environments as pH levels

Digestive System Regulation
peritoneum and mesenteries
Peritoneum and Mesenteries
  • Peritoneum
    • Visceral: Covers organs
    • Parietal: Covers interior surface of body wall
    • Retroperitoneal: Behind peritoneum as kidneys, pancreas, duodenum
  • Mesenteries
    • Routes which vessels and nerves pass from body wall to organs
    • Greater omentum
    • Lesser omentum
oral cavity
Oral Cavity
  • Mouth or oral cavity
    • Vestibule: Space between lips or cheeks and alveolar processes
    • Oral cavity proper
  • Lips (labia) and cheeks
  • Palate: Oral cavity roof
    • Hard and soft
  • Palatine tonsils
  • Tongue: Involved in speech, taste, mastication, swallowing
teeth
Teeth
  • Two sets
    • Primary, deciduous, milk: Childhood
    • Permanent or secondary: Adult (32)
  • Types
    • Incisors, canine, premolar and molars
salivary glands
Salivary Glands
  • Produce saliva
    • Prevents bacterial infection
    • Lubrication
    • Contains salivary amylase
      • Breaks down starch
  • Three pairs
    • Parotid: Largest
    • Submandibular
    • Sublingual: Smallest
pharynx and esophagus
Pharynx

Nasopharynx

Oropharynx: Transmits food normally

Laryngopharynx: Transmits food normally

Esophagus

Transports food from pharynx to stomach

Passes through esophageal hiatus (opening) of diaphragm and ends at stomach

Hiatal hernia

Sphincters

Upper

Lower

Pharynx and Esophagus
deglutition swallowing
Deglutition (Swallowing)
  • Three phases
    • Voluntary
      • Bolus of food moved by tongue from oral cavity to pharynx
    • Pharyngeal

Reflex: Upper esophageal sphincter relaxes, elevated pharynx opens the esophagus, food pushed into esophagus

    • Esophageal
      • Reflex: Epiglottis is tipped posteriorly, larynx elevated to prevent food from passing into larynx
functions
Functions
  • Ingestion: Introduction of food into stomach
  • Mastication: Chewing
  • Propulsion
    • Deglutition: Swallowing
    • Peristalsis: Moves material through digestive tract
stomach anatomy
Stomach Anatomy:
  • Openings
    • Gastroesophageal: To esophagus
    • Pyloric: To duodenum
  • Regions
    • Cardiac
    • Fundus
    • Body
    • Pyloric
stomach histology
Stomach Histology:
  • Layers
    • Serosa or visceral peritoneum: Outermost
    • Muscularis: Three layers
      • Outer longitudinal
      • Middle circular
      • Inner oblique
    • Submucosa
    • Mucosa
stomach histology1
Stomach Histology
  • Rugae: Folds in stomach when empty
  • Gastric pits: Openings for gastric glands
    • Contain cells
      • Surface mucous: Mucus
      • Mucous neck: Mucus
      • Parietal: Hydrochloric acid and intrinsic factor
      • Chief: Pepsinogen
      • Endocrine: Regulatory hormones
small intestine
Small Intestine
  • Site of greatest amount of digestion and absorption
  • Divisions
    • Duodenum
    • Jejunum
    • Ileum: Peyer’s patches or lymph nodules
  • Modifications
    • Circular folds or plicae circulares, villi, lacteal, microvilli
  • Cells of mucosa
    • Absorptive, goblet, granular, endocrine
small intestine secretions
Small Intestine Secretions
  • Mucus
    • Protects against digestive enzymes and stomach acids
  • Digestive enzymes
    • Disaccharidases: Break down disaccharides to monosaccharides
    • Peptidases: Hydrolyze peptide bonds
    • Nucleases: Break down nucleic acids
  • Duodenal glands
    • Stimulated by vagus nerve, secretin, chemical or tactile irritation of duodenal mucosa
liver
Liver
  • Lobes
    • Major: Left and right
    • Minor: Caudate and quadrate
  • Ducts
    • Common hepatic
    • Cystic
      • From gallbladder
    • Common bile
      • Joins pancreatic duct at hepatopancreatic ampulla
functions of the liver
Functions of the Liver
  • Bile production
    • Salts emulsify fats, contain pigments as bilirubin
  • Storage
    • Glycogen, fat, vitamins, copper and iron
  • Nutrient interconversion
  • Detoxification
    • Hepatocytes remove ammonia and convert to urea
  • Phagocytosis
    • Kupffer cells phagocytize worn-out and dying red and white blood cells, some bacteria
  • Synthesis
    • Albumins, fibrinogen, globulins, heparin, clotting factors
gallbladder
Gallbladder
  • Bile is stored and concentrated
  • Stimulated by cholecystokinin and vegal stimulation
  • Dumps into small intestine
  • Production of gallstones possible
    • Drastic dieting with rapid weight loss
pancreas
Anatomy

Endocrine

Pancreatic islets produce insulin and glucagon

Exocrine

Acini produce digestive enzymes

Regions: Head, body, tail

Secretions

Pancreatic juice (exocrine)

Trypsin

Chymotrypsin

Carboxypeptidase

Pancreatic amylase

Pancreatic lipases

Enzymes that reduce DNA and ribonucleic acid

Pancreas
movement in small intestine
Movement in small intestine:
  • Mixing: Segmental contraction that occurs in small intestine
  • Secretion: Lubricate, liquefy, digest
  • Digestion: Mechanical and chemical
  • Absorption: Movement from tract into circulation or lymph
  • Elimination: Waste products removed from body
large intestine
Large Intestine:
  • Extends from ileocecal junction to anus
  • Consists of cecum, colon, rectum, anal canal
  • Movements sluggish (18-24 hours)
large intestine1
Large Intestine
  • Cecum
    • Blind sac, vermiform appendix attached
  • Colon
    • Ascending, transverse, descending, sigmoid
  • Rectum
    • Straight muscular tube
  • Anal canal
    • Internal anal sphincter (smooth muscle)
    • External anal sphincter (skeletal muscle)
    • Hemorrhoids: Vein enlargement or inflammation
secretions of large intestine
Secretions of Large Intestine
  • Mucus provides protection
    • Parasympathetic stimulation increases rate of goblet cell secretion
  • Pumps
    • Exchange of bicarbonate ions for chloride ions
    • Exchange of sodium ions for hydrogen ions
  • Bacterial actions produce gases called flatus
movement in large intestine
Movement in Large Intestine
  • Mass movements
    • Common after meals
  • Local reflexes in enteric plexus
    • Gastrocolic: Initiated by stomach
    • Duodenocolic: Initiated by duodenum
  • Defecation reflex
    • Distension of the rectal wall by feces
  • Defecation
    • Usually accompanied by voluntary movements to expel feces through abdominal cavity pressure caused by inspiration
digestion absorption transport
Digestion, Absorption, Transport
  • Digestion
    • Breakdown of food molecules for absorption into circulation
      • Mechanical: Breaks large food particles to small
      • Chemical: Breaking of covalent bonds by digestive enzymes
  • Absorption and transport
    • Molecules are moved out of digestive tract and into circulation for distribution throughout body
liver histology
Liver Histology

portal

triad

Figure 24.20a, b

3 architecture of the hepatic parenchyma
3. Architecture of the Hepatic Parenchyma

The hepatic lobuleis the structural unit of the liver.

Portal vein

Bile duct

Sinusoids

Central vein

Liver cells (Hepatocytes)

Portal area

Hepatic artery

slide58
Bile

…each day around 600 ml of bile is produced…

  • Bile acid
  • Phospholipids
  • Cholesterol
  • Bilirubin
  • Waste products
  • Electrolytes
  • Mucin
functions of the liver1
Functions of the Liver
  • Bile production
    • Salts emulsify fats, contain pigments as bilirubin
  • Storage
    • Glycogen, fat, vitamins, copper and iron
  • Nutrient interconversion
  • Detoxification
    • Hepatocytes remove ammonia and convert to urea
  • Phagocytosis
    • Kupffer cells phagocytize worn-out and dying red and white blood cells, some bacteria
  • Synthesis
    • Albumins, fibrinogen, globulins, heparin, clotting factors
exocrine pancreas enzymes
Exocrine Pancreas – Enzymes
  • Trypsinogen
  • Chymotrysinogen
  • Carboxypeptidases
  • Pro-elastase
  • Phospholipase
  • pancreatic lipase
  • Pancreatic amylase
lipoproteins
Lipoproteins
  • Types
    • Chylomicrons
      • Enter lymph
    • VLDL
    • LDL
      • Transports cholesterol to cells
    • HDL
      • Transports cholesterol from cells to liver
water and ions
Water and Ions:
  • Water
    • Can move in either direction across wall of small intestine depending on osmotic gradients
  • Ions
    • Sodium, potassium, calcium, magnesium, phosphate are actively transported
effects of aging
Effects of Aging
  • Decrease in mucus layer, connective tissue, muscles and secretions
  • Increased susceptibility to infections and toxic agents
    • Ulcerations and cancers