The document provides an overview of the small and large intestines, including their structure, function, and relevant pathologies. It details the small intestine's length, parts, and adaptations for digestion and absorption, including circular folds, villi, and microvilli. Additionally, it discusses the blood supply, lymphatic structures, and nerve supply associated with these organs.

1. SMALL AND LARGE
INTESTINE

2. INTRODUCTION
 Longest part of digestive
system
1. Long & less distensible –
Small intestine
2. Shorter & more
distensible- Large intestine
 Function- digestion,
metabolism & stored for
expulsion.
 Suffers –bacterial infection
like typhoid, tuberculosis.
 parasitic infection like
round worm, tape worm
etc,
 Diarrhea & Dysentery.

3. SMALL INTESTINE
 EXTEND; Pylorus to ileoceacal
junction
 Measurement: 6 meters long,
greater in male than in female &
greater in cadavers
 Divided into:
1. Upper- fixed part-
DUODENUM- 25cm long.
2. Lower – mobile part – long
convoluted tube
 Upper 2/5th
of mobile
intestine are known as
JEJUNUM & lower 3/5th
known as ILEUM.
 Structures adapted for
digestion & absorption.

4. RELEVANT FEATURES
1. Large surface area: for absorption of digested
food very large surface area is required.This is
achieved by:
 Greater length of intestine
 Presence of
1. Circular folds of mucous membrane,
2.Villi &
3. Microvilli.

5. 1.Circular folds of mucous membrane/plicae
circulares /valve of kerking
 Forms complete or
incomplete circles.
 Permanent & not obliterated
by distention
 Begins in the 2nd
part of
duodenum & become large &
closely set below level of the
major duodenal papilla.
 They continue to be closely
set in the proximal half of the
jejunum but diminish
progressively in size &
number in distal half of
jejunum & in the proximal half
of ileum.

6.  Almost absent in the distal half of the
ileum.
 Apart from increasing the surface area for
absorption , the circular folds facilitate
absorption by slowing down the passage
of intestinal contents.

7. II. Intestinal villi
 Finger like projection of
mucous membrane,
visible to naked eye.
 Valvety appearnce
 Large & numerous in the
duodenum & jejunum but
smaller & fewer in the
ileum.
 Vary in density from 10-
40 per square millimeter
& about 1-2 mm long.
 Increases the surface area
about 8 times

8. Microvilli
 Villus is covered
by a layer of
absorptive
columnar cells,
surface of these
cells has a
striated border
seen under the
electron
microscope

9. Intestinal Glands or Crypts of
Lieberkuhn
 Simple tubular glands
distributed over the
entire mucous
membrane of jejunum &
ileum.
 Open by small circular
apertures on the
surface of mucous
membrane b/w villi
 Secretes digestive
enzymes

10.  Epithelial cells of glands
show high level of
mitotic activity,
proliferated cell
gradually move
towards the surface to
be shed from tips of
villi .
 Complete epithelial
lining of the intestine is
replaced every 2-4days.

11. Lymphatic follicles
 Two types
1. Solitary lymphatic follicle- 1
to 2 mm & are distributed
throughout the small & large
intestine.
2. Aggregated lymphatic
follicles/ Peyer’s patches -
circular or oval patches,
varying in length 2-10cm &
containing 10-200 follicles.
 Ileum- largest & most
numerous
 Distal jejunum- small circular
& fewer
 Placed- antimesentric border
 Ulcerated in typhoid fever

12.  Both most numerous
at puberty , diminish
in size & number
thereafter.
 Each villus has a
central lymp vessel
called a lacteal –
plexes in the wall of
gut- regional lymph
nodes

13. Arterial supply
 Jejunum & ileum –
jejunal & ileal
branches of superior
mesenteric artery
 Vasa recta distributed
alternatively to
opposite surface of
gut – run b/w serous
& muscular coat
reaches villi.

14. Lymphatics
 Mesentric lymph nodes

15. Nerve supply
 Symphathetic – T9-T11
 Parasymphathetic- vagus
 Enteric nervous system