Presentation as a overview of GIT organ Small intestine.

1. Small Intestine

2. Introduction
 The intestine, which is the longest part of the digestive tube, is
divided into small intestine and large intestine.
 Food has to be digested , metabolized and stored for expulsion
in the intestines.
 The small intestine extends from the pylorus to the ileocecal
junction.
 It is about 6 meter long.
 It is approximately 2.5–3 cm in diameter.
 The surface area of the human small intestinal mucosa averages
30 square meter

3. • Plicae
– Transverse folds of the intestinal
lining
• Villi
– Fingerlike projections of the
mucosa
• Lacteals
– Terminal lymphatic in villus
• Intestinal glands
– Lined by entero-endocrine,
goblet and stem cells
• Duodenal glands (Brunner’s
glands)
– produce mucus, buffers,
urogastrone
Histology of the small intestine

6. Duodenum
• The duodenum is a short structure (about 20–25 cm long) continuous with the
stomach and shaped like a "C".
• It lies above the level of the umbilicus, opposite 1st, 2nd and 3rd lumbar
vertebrae.
• It receives gastric chyme from the stomach, together with digestive juices
from the pancreas (digestive enzymes) and the gall bladder (bile).
• The digestive enzymes break down proteins and bile
and emulsify fats into micelles.
• The duodenum contains Brunner's glands, which produce a mucus-rich
alkaline secretion containing bicarbonate.

8. Jejunum
 The jejunum is the midsection of the small intestine, connecting
the duodenum to the ileum.
 It is about 2.5 m long, and contains the plicae circulares, and villi
that increase its surface area.
 Products of digestion (sugars, amino acids, and fatty acids) are
absorbed into the bloodstream here.
 The suspensory muscle of duodenum marks the division between
the duodenum and the jejunum.

9. Ileum
• The final section of the small intestine.
• It is about 3 m long, and contains villi
similar to the jejunum.
• It absorbs mainly vitamin B12 and
bile acids, as well as any other
remaining nutrients.
• Ileum joins to the cecum of the large
intestine at the ileocecal junction.

10. Layer Duodenum Jejunum Ileum
Serosa
1st part serosa, 2nd–4th
adventitia
Normal Normal
Muscularis externa
Longitudinal and
circular layers, with
Auerbach's (myenteric)
plexus in between
Same as duodenum Same as duodenum
Submucosa
Brunner's glands and
Meissner's
(submucosal) plexus
No BG No BG
Mucosa: muscularis
mucosae
Normal Normal Normal
Mucosa: lamina propria No PP No PP Peyer's patches
Mucosa: intestinal
epithelium
Simple columnar.
Contains goblet cells,
Paneth cells
Similar to duodenum No

12. Duodenum
Arterial supply: superior anterior and posterior
pancreaticoduodenal arteries (branches of gastroduodenal
artery), anterior and posterior inferior pancreaticoduodenal
arteries (branches of superior mesenteric artery)
Venous drainage: duodenal veins -> pancreaticoduodenal vein -
> superior mesenteric vein ->portal vein
Innervation: vagus nerve via celias and mesenteric plexi
(parasympathetic), intestinal plexi around arterial vessels
(sympathetic)
Jejunum and ileum
Arterial supply: arterial arcades of superior mesenteric artery
Venous drainage: venous arcades -> superior mesenteric vein -
> portal vein
Innervation: vagus nerve via myenteris and submucosal plexi
(parasympathetic) greater and lesser splanchnic nerves
(sympathetic)

13. Duodenum
The duodenum receives both sympathetic and parasympathetic
innervation. The vagus nerve (CN X), provides parasympathetic fibers
via the celiac and superior mesenteric plexuses, while the sympathetic
trunk also gives fibers to the intestinal plexuses that travel along the
pancreaticoduodenal arteries.
Innervation

14. Jejunum and Ileum
Like the duodenum, the lower section of the small intestine is also
innervated by both parasympathetic and sympathetic fibers. The
sympathetic nerves arrive from the fifth to the ninth thoracic spinal
cord segments, which enter the sympathetic trunk and synapse on the
postganglionic cells in the celiac and superior mesenteric ganglia
before becoming the greater and lesser splanchnic nerves.
The parasympathetic system consists of preganglionic fibers that stem
from the posterior vagal trunks and synapse on postganglionic cells in
the myenteric and submucosal plexuses of the intestinal wall.

15. •The duodenum is the mixing pot of the small intestine. It receives chyme
from the stomach, which is a mixture of food products and acid.
Pancreatic enzymes enter here as well, releasing enzymes to break down
the products from the stomach, and bicarbonate to neutralize the acid
from the stomach before reaching the jejunum. Here the liver introduces
bile which allows for the breakdown and absorption of fat from food
products.
•The jejunum primary function is absorption, where sugars, amino acids,
and fatty acids are absorbed.
•The ileum absorbs nutrients that did not get absorbed by the jejunum,
with important nutrients being vitamin B12 and bile acids for reuse.
Function

16. Small bowel
obstruction
Obstruction is a blockage
that keeps food or liquid
from passing through
your small intestine or
large intestine (colon).

17. Risk factors -
 Abdominal or pelvic surgery, which often causes adhesions — a
common intestinal obstruction
 Crohn's disease, which can cause the intestine's walls to thicken,
narrowing the passageway
 Cancer in your abdomen
Causes –
 Intestinal adhesions — bands of fibrous tissue in the abdominal
cavity that can form after abdominal or pelvic surgery
 Hernias — portions of intestine that protrude into another part of
your body
 Colon cancer

18. Function

19. Function

20. Function

21. Function

22. Function

23. Function

24. Function

25. •Stomach flu (enteritis): Inflammation of the small intestine. Infections (from
viruses, bacteria, or parasites) are the common cause.
•Small intestine cancer: Rarely, cancer may affect the small intestine. There are
multiple types of small intestine cancer, causing about 1,100 deaths each year.
•Celiac disease: An "allergy" to gluten (a protein in most breads) causes the
small intestine not to absorb nutrients properly. Abdominal pain and weight loss
are usual symptoms.
•Carcinoid tumor: A benign or malignant growth in the small intestine. Diarrhea
and skin flushing are the most common symptoms.
•Intestinal obstruction: A section of either the small or large bowel can become
blocked or twisted or just stop working. Belly distension, pain, constipation, and
vomiting are symptoms.
•Colitis: Inflammation of the colon. Inflammatory bowel disease or infections
are the most common causes.