Small and Large Intestines Parts of the Small

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Small and Large Intestines

Small and Large Intestines

Parts of the Small Intestines

Parts of the Small Intestines

How do the parts of Small intestines Vary? • Duodenum: secretes mucous enzymes and

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; p. H 7 -8; absorbs B 12 and bile salts

Intestinal Wall • Mucosa contain: absorptive cells aka: enterocytes • 2 layers of smooth

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

Function of villi and microvilli • Specialized absorptive units – Microscopic units with layers

Function of villi and microvilli • Specialized absorptive units – Microscopic units with layers of epithelial cells • 200 m 2 for nutrient absorption • desmosomes and tight junctions prevent microbes b/t cells

Regulator of absorptive units • Absorption occurs by active transport, facilitated diffusion, Na/K pump

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

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

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

Large Intestines • Colon • 6 cm wide and 1. 5 meets long (6

Large Intestines • Colon • 6 cm wide and 1. 5 meets long (6 feet)

Movement of chyme • Chyme enters the colon thru ileocecal valve • Located b/t

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

Major segments of Lg intestines • Transverse • Ascending – Sites of water and

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

Process that allows for water absorption • Osmosis • …following the Na/K pump which

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

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

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

Stool mass What’s in your Poo? • Dietary fiber (pectin and cellulose) • Fruits

Stool mass What’s in your Poo? • Dietary fiber (pectin and cellulose) • Fruits and vegetables • Indigestible substances

Movements of colon • Segmentation: circular muscle contraction • Peristalsis: movements by circular and

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

Mass movements • Defecation • Rectal distention triggers defecation reflex, which then forces feces

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

Diseases/Disorders • Diverticulitis – Fever, pain in abdomin, diareherra • Possibly caused from increase

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

Crohn’s Disease • autoimmune disease: caused by the immune system attacking the gastrointestinal tract

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 CARD 15 gene