SMALL INTESTINE AND LARGE INTESTINE

DR NILESH KATE
MBBS,MD
ASSOCIATE PROF
DEPT. OF PHYSIOLOGY
SMALL
INTETSINE AND
LARGE
INTESTINE

OBJECTIVES.
 FUNCTIONAL ANATOMY
 INTESTINAL SECRETIONS
 FUNCTIONS OF INTESTINE
 APPLIED ASPECTS.
Thursday, September 27, 2018

FUNCTIONAL ANATOMY
SMALL INTESTINE
 Gross Anatomy.
 Extend – from Pylorus
to the Ileocaecal Valve
 Length – 6-7m.
 Divided into 3 parts
 Duodenum
 Jejunum
 Ileum.

FUNCTIONAL ANATOMY
 Duodenum –
 First, shortest & most
fixed.
 C shaped
 4 parts –
 Superior (Duodenal Cap)
most common site for
Peptic Ulcer.
 Descending – Ampulla of
Water opens
 Horizontal &
 Ascending.

FUNCTIONAL ANATOMY
 Jejunum
 Proximal 2/5th
 Ileum –
 Distal 3/5th

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

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.

STRUCTURAL CHARACTERISTICS
SMALL INTESTINE
 Histological – 4 layers
 Mucosa
 Sub mucosa
 Muscle coat
 Serosa.

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)

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.

VILLI
 Finger like projections
of mucous membrane
 Total number – 4-5
millions
 20-40 villi/mm2
 Length – 0.5-1mm

VILLI
 Structure –
 Each villus covered – single layer
of columnar epithelia cells-
enterocytes.
 Core contains – artery venule &
Lymphatic vessel & nerve network
 Activity – during Digestion &
absorption –villi contracts &
relax slowly & pump Lymph
from core to submucosal lacteal.

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.

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.

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.

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 over
posterior aspect.
 Small peritonial bags of fat
“Appendices epiploicae”

SMALL INTESTINE AND LARGE INTESTINE

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