Small and Large Intestines

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Small and Large Intestines
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Parts of the Small Intestines
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How do the parts of Small intestines Vary?

• Duodenum secretes mucous enzymes and hormones
  and is a site of entry for bile and pancreatic
  juices
• Jejunum nutrient absorption
• ileum central portion of the abdominal cavity
  pH 7-8 absorbs B12 and bile salts

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Intestinal Wall

• Mucosa contain absorptive cells aka enterocytes
• 2 layers of smooth muscle
• Circular and longitudinal aid in intestinal
  mobility
• Serosa supportive CT

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Function of villi and microvilli

• Specialized absorptive units
• Microscopic units with layers of epithelial cells
• 200m2 for nutrient absorption
• desmosomes and tight junctions prevent microbes
  b/t cells

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Regulator of absorptive units

• Absorption occurs by active transport,
  facilitated diffusion, Na/K pump
• Actin (protein)
• Filaments regulated by autonomic nerve fibers
• Fats and water soluble nutrients take different
  paths

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Movement Patterns

• Segmentation circular muscle contraction
• Peristalsis movements by circular and
  longitudinal muscles

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Large Intestines

• Colon
• 6 cm wide and 1.5 meets long (6 feet)

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Movement of chyme

• Chyme enters the colon thru ileocecal valve
• Located b/t ileum and colon
• Gastroileal reflex regulates ileocecal valve by
  the peristaltic waves

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Major segments of Lg intestines

• Transverse
• Ascending
• Sites of water and Na absorption and mucus
  secretions
• Descending
• Sigmoid
• Storage of fecal matter

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Process that allows for water absorption

• Osmosis
• following the Na/K pump which is what type of
  cellular transport??

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Important to replenish electrolyte balance

• Homeostasis
• K is secreted into large intestines

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Stool massWhats in your Poo?

• Dietary fiber (pectin and cellulose)
• Fruits and vegetables
• Indigestible substances

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Movements of colon

• Segmentation circular muscle contraction
• Peristalsis movements by circular and
  longitudinal muscles
• Mass movement force of feces along the colon
  through the anal canal

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Mass movements

• Defecation
• Rectal distention triggers defecation reflex,
  which then forces feces out of anal canal
• Control? Other mechanisms
• Internal and external valves (sphincters)
• Pressure from abdominal cavity

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Diseases/Disorders

• Diverticulitis
• Fever, pain in abdomin, diareherra
• Possibly caused from increase in intraluminal
  pressure.
• Indiv. With low dietary fiber intake at high risk

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Crohns Disease

• autoimmune disease caused by the immune system
  attacking the gastrointestinal tract and
  producing inflammation in the gastrointestinal
  tract
• may affect any part of the gastrointestinal tract
  from mouth to anus,
• Symptoms abdominal pain, diarrhea (which may be
  bloody), vomiting, or weight loss
• Type of inflammatory bowel disease (IBD)
• appears to be a genetic link
• Mutations in the CARD15 gene