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Small and Large Intestines

Delve into the intricate details of the small and large intestines, exploring their parts, functions, movement patterns, absorption processes, and common diseases/disorders. Gain insights into the complexities of nutrient absorption, movement of chyme, and mechanisms regulating defecation. Discover key components like the duodenum, jejunum, ileum, and colon, and learn about conditions such as diverticulitis and Crohn's disease that affect the gastrointestinal system.

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Small and Large Intestines

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  1. Small and Large Intestines

  2. Parts of the Small Intestines

  3. 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

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

  5. 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

  6. 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

  7. Movement Patterns • Segmentation: circular muscle contraction • Peristalsis: movements by circular and longitudinal muscles

  8. Large Intestines • Colon • 6 cm wide and 1.5 meets long (6 feet)

  9. 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

  10. Major segments of Lg intestines • Transverse • Ascending • Sites of water and Na absorption and mucus secretions • Descending • Sigmoid • Storage of fecal matter

  11. Process that allows for water absorption • Osmosis • …following the Na/K pump which is what type of cellular transport??

  12. Important to replenish electrolyte balance • Homeostasis • K is secreted into large intestines

  13. Stool massWhat’s in your Poo? • Dietary fiber (pectin and cellulose) • Fruits and vegetables • Indigestible substances

  14. 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

  15. 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

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

  17. Crohn’s 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

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