Digestive System

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Digestive System
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Digestive SystemObjectives

• 1 Describe the primary and accessory organs of
  the GI system and how each plays a role in
  digestion
• 2. Identify and describe the structures
  associated with the oral cavity including the
  tongue, teeth, gums and salivary glands

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Digestive SystemObjectives

• 3. Describe and diagram the structure of the
  tooth as well as deciduous and permanent dental
  formulae
• 4. Identify the source and function of the
  digestive secretions provided in Table 7.1

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Digestive SystemObjectives

• 5. Explain the origin and structure of GI support
  structures including the mesentery, mesocolon,
  peritoneal extensions and structures of the liver
• 6. Describe and diagram the anatomical
  relationship between the liver, gall, bladder,
  pancreas and small intestine

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Digestive SystemObjectives

• 7. Explain the microscopic anatomy of the liver
  and how this structure relates to the overall
  functions of the liver
• 8. Describe the anatomy, histology and functions
  of the tubular digestive organs

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Digestive SystemObjectives

• 9. Discuss the etiology, symptoms and treatment
  of diabetes mellitus, hypoglycemia, dental
  caries, periodontal disease, peritonitis, ulcers,
  indigestion, constipation, diarrhea,
  appendicitis, cirrhosis, hepatitis, gall stones
  and eating disorders
• 10. Use the correct terminology associated with
  the digestive system

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Digestive SystemObjectives

• 11. Discuss the effects of aging on the digestive
  system

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Digestive System
9
Digestive Process

• Ingestion
• Movement of food along tract
• Swallowing
• Peristalsis
• Pendular movements

10
Digestive Process

• Mechanical and chemical digestion
• Chewing /mastication
• Enzymatic activity on food
• Absorption
• Defecation

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Tubular Digestive Organs

• Large Intestine
• Cecum
• Colon
• Ascending
• Transverse
• Descending
• Sigmoid
• Rectum
• Anus

• Mouth
• Pharynx
• Esophagus
• Stomach
• Small Intestine
• Duodenum
• Jejunum
• Ileum

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Mouth

• Subdivisions
• Vestibule
• between teeth and cheeks
• Oral/buccal cavity
• from teeth to fauces

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Mouth
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Accessory Organs

• Teeth
• Tongue
• Salivary glands

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Accessory Organs -Teeth

• Kinds of teeth
• Incisors
• canine/cuspid
• premolars/bicuspid (absent in deciduous)
• molars/tricuspids

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Dental Formulae

• Deciduous
• Three tooth types
• Incisor, canine, molar
• 212212/212212 Total 20
• Permanent
• Four tooth types
• Incisor, canine, premolar, molar
• 32122123/32122123 Total 32

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Adult Dentition
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Accessory Organs -Teeth

• Deciduous and permanent structurally similar
• Crown (above the gum line)
• Neck at junction of gum line)
• Root (below the gum line)

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Tooth Structure
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Tooth Structure

• Hard portion
• Enamel
• Dentin

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Tooth Structure

• Soft portion
• Pulp
• blood and nerve supply
• Anchoring structure to underlying bone
• Cementum
• periodontal ligament

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Tongue

• Extrinsic and intrinsic skeletal muscle covered
  with mucous membrane

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Tongue

• Anchored to floor of mouth via lingual frenulum

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Tongue

• Intrinsic muscle
• Transverse
• Longitudinal
• Vertical

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Tongue

• Extrinsic (to bones of skull)
• Genioglossus
• Hyoglossus
• Styloglossus
• Palatoglossus

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Tongue Papillae3 Types

• Filiform
• distal 2/3 of tongue
• conical shape
• increase surface area, assist in chewing
  swallowing
• Fungiform
• scattered among filiform
• mushroom shaped
• taste buds at base

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Tongue Papillae

• Circumvallate/vallate
• Large
• root of tongue - gustatory region
• recessed circles w/ taste buds
• Lateral surface has rudimentary folds foliae

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Salivary Glands

• Two types
• Mucosal single goblet cell on mucosal membrane of
  mouth, tongue, moisten food, mouth
• Large, paired compound exocrine glands, secrete
  into mouth upon stimulus

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Large Salivary Glands

• Parotid
• anterior to ear
• drains via Stensons duct near maxillary molar
• Submandibular
• floor of the mouth along mandible
• drains via Whartons duct into floor of mouth

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Large Salivary Glands

• Sublingual
• superior to submandibular glands
• drain via multiple (Rivinius) duct openings
  below tongue

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Salivary Glands
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Saliva

• Water
• Enzymes
• salivary amylase/ptyalin
• lingual lipase
• lysozyme (bactericide)
• Other
• salts, desquamated cells, mucous

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Pharynx

• Muscular tube adapted for swallowing/deglutition
  bolus of chewed food
• Extends posteriorly from internal nares to
  esophagus

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Pharynx
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Generic Gut Layers

• Tunica Mucosa
• Submucosa
• Tunica Muscularis
• Tunica Serosa

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Tunica Mucosa

• Epithelium.
• stratified squamous near opening.
• simple columnar elsewhere.
• Lamina propria.
• CT.
• supports blood vessels etc.
• contains lymphatic tissue.
• Muscularis mucosae.
• smooth muscle.

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Submucosa

• Submucosa
• Vascularized areolar CT
• Nerve supply

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Tunica Muscularis

• Superior portions skeletal muscle, from lower
  esophagus on, smooth muscle
• Two layers
• longitudinal (incomplete in colon)
• Circular
• Responsible for gut motility

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Tunica Serosa (Peritoneum)

• Continuous with mesentery
• Largest serous membrane
• Visceral and parietal divisions
• Retroperitoneal organs
• Folds - provide mechanical support, blood
  vessels, nerves, lymphatics

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Esophagus

• Function
• Moisten food
• Transport food to stomach
• Length 25cm

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Esophagus Layers

• T. Mucosa (stratified squamous epithelium)
• mucous glands near stomach
• Submucosa
• mucous glands
• T. Muscularis
• Upper 1/3 skeletal muscle
• Lower 1/3 smooth muscle
• T. Adventitia
• Areolar CT, no epithelium, not true serosa

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Tunica Serosa (Peritoneum)

• Mesentery
• mesocolon
• greater omentum
• lesser omentum
• falciform ligament

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Tunica Serosa (Peritoneum)

• Occurs only below diaphragm
• CT w/ simple squamous epithelium

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Stomach

• J shaped
• Greater curvature
• Lesser curvature
• Four regions of stomach
• Cardia
• Fundus
• Body
• Pylorus
• Lined with mucosal folds rugae

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Stomach
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Stomach Glands

• Mucosal glands/gastric glands in gastric pits
• Mixed food with gastric juice chyme
• Minimal absorption (alcohol, weak acids, H20,
  electrolytes)
• Four kinds of secretory cells

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Stomach Histology
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Gastric Gland Cells

• mucous neck
• mucus
• chief/zymogenic
• pepsinogen (inactive pepsin)
• Lipase
• Rennin

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Gastric Gland Cells

• parietal / oxyntic
• HCl (activates pepsinogen, destroys
  microorganisms)
• intrinsic factor (Vit B12 absorption - pernicious
  anemia)

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Gastric Gland Cells

• enteroendocrine cells
• hormone gastrin stimulating stomach secretions
• concentrated in pyloric region

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Small Intestine

• 7 m, three divisions
• Duodenum
• Jejunum
• Ileum

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Duodenum

• - 25 cm
• Adapted to receive gastric juice, pancreatic and
  liver secretions
• Submucosal Brunners glands secrete mucus
• Motility
• Peristalsis
• Segmentation
• Retroperitoneal
• Little absorption
• Secretes hormones

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Jejunum

• 2.5 m
• Modified mucosa to increase surface area for
  absorption
• Microvilli
• Villi
• plicae circularis

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Jejunum

• Produce enzymes for digestion
• Carbohydrases
• Peptidases
• Nucleases

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Ileum

• 3.5m
• Lots of lymphatic nodules and Peyers patches

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Small Intestine

• 7 m, three divisions
• Duodenum
• Jejunum
• Ileum

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Large Intestine

• 1.5 m
• ileocecal sphincter regulates passage

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Large Intestine Regions

• Cecum
• Colon
• Rectum
• Anus

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Large Intestine Regions

• Cecum
• blind pouch
• vermiform appendix

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Large Intestine Regions

• Colon subdivisions (4)
• Ascending
• Transverse
• Descending
• Sigmoid

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Large Intestine
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Large Intestine Regions

• Major curvatures of colon
• Hepatic
• Splenic

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Large Intestine
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Large Intestine Structures

• Incomplete longitudinal muscle taenia coli
• creates haustra
• Serosal fat filled appendages epiploic
  appendages

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Large Intestine Functions

• Absorption (H20)
• Vitamin synthesis
• Feces production

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Large Intestine Physiology

• rate of passage of feces determines consistency
  of feces
• constipation----gtdiarrhea

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Feces Composition

• Undigested food materials
• Bacteria (20)
• continue breakdown
• produce vitamin K, B
• produce gas
• H20

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Feces Composition

• Salts
• Epithelial cells
• shed from gut lining
• Mucus

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Feces

• Color
• food breakdown products
• bile pigments
• Consistency
• H2O
• Gas
• byproduct of bacterial activity, especially on
  amino acids
• skatole, indole, H2S, methane

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Rectum

• Distal 15 cm
• Empty most of the time
• Has complete longitudinal muscle
• Blood supply via inferior hemorrhoidal veins

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Anus

• internal sphincter smooth muscle
• external sphincter skeletal muscle

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Accessory Organs

• Liver
• Gall Bladder
• Pancreas

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Liver Functions

• Manufacture bile
• Synthesize cholesterol
• Store amino acids, vitamins, minerals, glycogen
• Detoxify nitrogenous waste
• Recycle blood pigments
• Synthesize plasma protein
• Phagocytosis

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Liver Structure

• Largest internal organ
• Superior surfaces conforms to diaphragm
• Inferior surface with colic and renal impressions

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Liver Structure

• Gall bladder attaches on inferior surface
• Posterior surrounds vena cava

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Liver Structure

• Four lobes
• Right (largest)
• Left
• Caudate
• Quadrate

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Liver Support Structures

• Falciform ligament - extension of parietal
  peritoneum between R and L lobes
• Ligamentum teres/round ligament - vestigial
  umbilical vein, attaches to umbilicus

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Liver Support Structures
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Liver Support Structures

• Coronary ligament - attaches superiorly to
  diaphragm
• Triangular ligament - joins with coronary,
  superior to diaphragm, together leave a portion
  of liver without a fibrous capsule
• Ligamentum venosum - vestigial ductus venosus on
  posterior aspect

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Liver Structure
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Liver Blood Supply

• Oxygenated via hepatic artery
• Deoxygenated, nutrient rich from gut via portal
  vein
• Join microscopically, dump into liver sinusoids

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Liver Blood Supply
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Liver Blood Supply
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Microscopic Liver Blood Supply

• Central vein
• Hepatic vein
• Inferior vena cava

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Triad
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Liver Lobule

• Liver lobule cylindrical/hexagonal functional
  units of liver
• Triads along margin
• hepatic artery (oxygenated blood)
• portal vein (nutrient rich blood)
• bile duct (bile from bile canaliculi)

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Liver Lobule
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Liver Lobule

• Sinusoids carry blood toward central vein
• Kupffer cells - phagocytes in sinusoids
• sinusoids allow passage of nutrients, waste into
  and out of hepatocytes

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Liver Lobule

• Bile canaliculi carry bile secreted by
  hepatocytes to bile ducts and out via
  
  R L hepatic ducts ---gtcom. hepatic
  duct---gtcystic duct---gtGB---gtcom. bile duct

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Lobule
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Hepatocyte
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Liver Pathologies Jaundice

• Yellowing of skin, eyes due to accumulation of
  bile pigments in blood crossing into interstitial
  fluid
• Multiple causes
• Hemolytic
• Hepatocellular
• Obstructive

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Jaundice

• Excessive bile pigment (bilirubin)
• Obstruction of bile ducts
• Diseases of hepatocytes causing them to be less
  able to metabolize bilirubin

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Liver Pathologies Hepatitis

• Viral inflammation
• hep A (RNA) - contaminated food, drink
• hepB(DNA) blood
• non-A, non-B blood

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Liver Pathologies Cirrhosis

• Progressive inflammation of liver.
• Scar tissue replacement of hepatocytes.
• Impaired circulation, portal hypertension.
• Jaundice.
• May be caused by alcohol, toxic chemical
  exposure, viral infection, etc.

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Cirrhosis
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Gall Bladder

• Function - store and concentrate bile
• 3 layers
• T. Mucosa with rugae
• T. Muscularis - smooth muscle
• T. Serosa - CT peritoneum

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Pathology Gallstones
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Pancreas

• 15cm x 3cm
• Head, body tail
• Retroperitoneal
• Exocrine and Endocrine

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Exocrine Pancreas

• 99 Exocrine pancreas
• Loosely aggregated pancreatic acini
• Produce pancreatic juice

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Exocrine Pancreas

• Enzymes
• Lipase
• Amylase
• Nuclease
• protease peptidase
• Trypsin
• Chymotrypsin
• Carboxypeptidase
• NaHC03 neutralizes gastric acid

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Exocrine Pancreas

• Dumped into pancreatic duct/Duct of Wirsung and
  accessory duct of Santorini then into duodenum

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Pancreas Drainage
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Endocrine Pancreas

• 1 Endocrine - Islets of Langerhans

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Endocrine Pancreas

• alpha cells
• 20 of Islet cells
• produce glucagon
• stimulates glycogenolysis gluconeogenesis
• raises blood glucose

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Endocrine Pancreas

• beta cells
• 75 of Islet cells
• produce insulin
• stimulates glucose uptake by cells glycogenesis
• reduces blood glucose

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Endocrine Pancreas

• delta cells
• produce somatostatin (insulin and glucagon
  inibiter)
• reduces glucagon and insulin production
• reduces food absorption

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Endocrine Pancreas

• F cells
• produce pancreatic polypeptide hormone
• influences pancreatic digestive enzyme production

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Diabetes Mellitus Symptoms

• Hyperglycemia
• Glycosuria
• Polyuria
• Thirst
• Weight loss
• Fatigue

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Diabetes Mellitus Types

• juvenile onset/type I (10)
• insulin dependent
• onset lt 40 yrs
• adult onset/type II (90)
• normal insulin levels, slow cellular response
• obesity, age gt40 yrs
• may be controlled with diet, exercise, oral
  antidiabetogenic drugs

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Diabetes Mellitus Complications

• Acute
• diabetic coma
• insulin shock

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Diabetic complications

• Chronic
• Retinopathy
• Nephropathy

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Diabetic complications

• Neuropathy
• increase in heart attack
• peripheral circulation impairment

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Hypoglycemia

• Excessive insulin