Digestion and absorption

1. The Intestines
Mr. Jayant A Gideon
Nursing TUTOR
HCN, SRHU.

2. Learning Objectives
By the end of the class the student will be able to
• Explain the anatomy small intestine
• Explain the anatomy of large intestine
• Differentiate between small and large intestine.
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3. FUNCTIONAL ANATOMY - SMALL INTESTINE
• Gross anatomy
• Extend – from Pylorus to the Ileocaecal Valve
• Length – 6-7m.
• Divided into 3 parts
• Duodenum
• Jejunum
• Ileum.
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4. FUNCTIONAL ANATOMY
• Duodenum –
• First, shortest & most fixed.
• C shaped
• 4 parts –
• Superior (Duodenal Cap) most common
site for Peptic Ulcer.
• Descending – Ampulla of Vater opens
• Horizontal &
• Ascending.
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5. FUNCTIONAL ANATOMY
• Jejunum
• Proximal 2/5th
• Ileum –
• Distal 3/5th
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6. FUNCTIONAL ANATOMY – LARGE INTESTINE
• Gross Anatomy
• Extend – from the Ileocaecal Valve to Rectum.
• Length – 100 cm.
• Divided into 3 parts
• Caecum
• Appendix
• Ascending Colon
• Transverse Colon
• Descending Colon
• Sigmoid colon & rectum and Anal Canal
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7. ILEOCAECAL VALVE
• Structure – valve is due to Invagination of ileum into Caecum.
• Function – to prevent backflow of faecal matter from Caecum into
ileum.
• Role of Ileocaecal sphincter –sphincter is thickened band of
circular muscle coat of terminal ileum.
• Control – Gastrin – relaxes.
• Secretin – Contracts.
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8. STRUCTURAL CHARACTERISTICS
SMALL INTESTINE
• Histological – 4 layers
• Mucosa
• Sub mucosa
• Muscle coat
• Serosa.
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9. MUCOUS MEMBRANE
• Length of small intestine – 6 meter.
• Absorptive area – 250m2 due to
• Plicae Circularis – Numerous folds of intestinal
mucosa
• Villi
• Microvilli along with crypts of Liberkuhn
(Depressions)
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11. PLICAE CIRCULARIS
• Numerous folds
• Absent in Duodenum
• Contains all layers of mucosa
• Lining epithelium, lamina Propria, Muscularis
Mucosa.
• Submucosa
• Functions – Increase surface area & Decreases
passage & fascilitate absorption.
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12. VILLI
• Finger like projections of mucous membrane
• Total number – 4-5 millions
• 20-40 villi/mm2
• Length – 0.5-1mm
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13. VILLI
• Structure –
• Each villus covered – single layer of columnar epithelia
cellsenterocytes.
• Core contains – artery venule & Lymphatic vessel & nerve network
• Activity – during Digestion & absorption – villi contracts & relax
slowly & pump Lymph from core to submucosal lacteal.
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14. THE CRYPTS OF LIBERKHUN.
• These are Tubular intestinal glands
which invaginate deep into lamina
propria between villi throughout small
intestine.
• Epithelial cells of mucous membrane of
small intestine & intestinal glands.
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15. THE CRYPTS OF LIBERKHUN
• Absorptive columnar cells
• Undifferentiated columnar cells
• Goblet cells
• Argentaffin or Enterochromaffin cells
• Zymogen cells or Paneth cells
• Duodenal glands of Brunner
• Peyer Patches.
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16. STRUCTURAL CHARACTERISTICS
OF LARGE INTESTINE
• Histologically similar to small intestine
except –
• Absence of plicae circulares & Villi
• Large number of Crypts of Liberkhun
with goblet cells – secrete Mucus.
• Epithelium Overlying lymphatic follicles
contains M cells.
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17. LONGITUDINAL LAYER OF
MUSCLE COAT
• Unusual
• Forms 3 thick Bands – “Taenia Coli”
• Shorter in Length, than other layers of colon forms
• Sacculations called “Haustrations”
• Serous layer – missing overposterior aspect.
• Small peritonial bags of fat “Appendices epiploicae”
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18. THANK YOU ! 18