Download MBBS (Bachelor of Medicine and Bachelor of Surgery) Latest Digestive System II Lecture PPT
DIGESTIVE SYSTEM II
GIT OR ALIMENTARY CANAL
? This is in the form of tube.
? Extend from oral cavity to
anus.
? Parts of GIT--
? Oral cavity
? Pharynx
? Oesophagus
? Stomach
? Small intestine
? Colon
? Rectum
? Anal canal
INTRODUCTION
? GENERAL HISTOLOGY OF ALIMENTARY CANAL
? It is tubular structure
? Four layers in the wall
? Layers from deep to superficial:--
I) Mucosa
- Epithelium
- Lamina propria
- Muscularis Mucosae
II) Submucosa
III) Muscle layer
IV) Serous layer / Adventitial layer
MUCOSA
? Innermost layer of alimentary canal.
? Epithelium
It is simple columnar (Absorption/secretion) all
over
except in the Oesophagus and the lower part of
Anal canal where it is stratified squamous
(Protection).
Organ
Epithelium
Mouth
Nonkeratinized Stratified Squamous
Pharynx
Nonkeratinized Stratified Squamous
Esophagus
Nonkeratinized Stratified Squamous
Stomach
Simple Columnar
Small Intestine
Simple Columnar
Large Intestine
Simple Columnar
Anus
Nonkeratinized Stratified Squamous
? Lamina propria
? Layers of loose connective tissue
? Supports the epithelium
? Contains blood and lymphatic vessels
? It also contain glands (gastric glands)
? It also contains mucosa associated lymphoid
tissue (MALT).
? Muscularis mucosae
- Thin layer of smooth
muscle that separates
lamina propria with the
submucosa.
- Inner layer: Circular
- Outer layer: Longitudinal
- It changes the shape of
mucosa, that helps in
absorption and secretion
SUBMUCOSA
? Consists of dense connective tissue rich in
collagen and elastic fibres.
? Contain numerous blood vessels, lymphatics
and nerve fibres and Meissner's plexus.
? It also contains glands (oesophagus and
duodenum)
MUSCLE LAYER
? It consists of smooth muscles all over GIT except
upper part of oesophagus which contain skeletal
muscles.
? Arranged in two layers
- Inner layer: Circular
- Outer layer: Longitudinal
Between the two layers "Auerbach's plexus
(Myenteric plexus)" is present.
This plexus controles motility of tract.
SEROSA /ADVENTITIA
? It is merely visceral peritoneum composed of
connective tissue and simple squamous
epithelium.
? The oesophagus lies outside the abdominal
cavity has a superficial layer called Adventitia
which consists of areolar connective tissue
OESOPHAGUS
? It is a straight muscular tube extending from pharynx
in neck to the stomach in abdomen.
? MUCOSA:
Epithelium: Non-Keratinised sratified squamous
epithelium
Lamina Propria: Thin layer of loose connective tissue.
Muscularis Mucosae:
- It is thicker than other parts of GIT
- It is single layer of longitudinally running smooth
muscle fibres.
? SUBMUCOSA:
? It is a wide layer of, dense connective tissue
composed of bundles of collagen and elastic
fibres.
? Due to elastic fibres, submucosa is thrown into
folds, hence lumen of oesophagus appears star
shaped
? Contains blood vessels and branched tubulo-
alveolar mucous glands
? MUSCLE LAYER
? Arranged in two layers:
- Inner layer: Circular
- Outer layer: Longitudinal
* Between the two layers ? Myenteric plexus of
nerve fibre and ganglion cells are present. It
controls peristaltic movement.
TYPES OF MUSCLES:
Upper 1/3rd ? Skeletal muscle
Middle 1/3rd ? Both skeletal and smooth muscle
Lower 1/3rd ? purely smooth muscle
? SEROSA / ADVEVTITIA
? It consists of loose areolar connective tissue,
which merges with the connective tissue of
surrounding structures.
HISTOLOGY OF STOMACH
INTRODUCTION
? On the basis of histological structure, stomach is
divided into three region:--
? i)Cardiac region
? ii)Fundic(or body) region
? iii)Pyloric region
? The stomach wall exhibits four general regions:--
? Mucosa-- a) Lining epithelium, b) Lamina propria,
c) Musularis mucosae
? Submucosa
? Muscle layer and
? Serosa .
FUNDIC OR BODY REGION
? Mucosa
? a)Lining epithelium
? Simple columnar
epithelium that
invaginates to various
extents into the lamina
propria, forming gastric
pits.
- These cells are involved in
mucus secretion. The
mucus protects the
epithelial lining from
damage due to the
presence of acid in the
stomach.
? b)Lamina propria--
? Small tubular fundic/gastric glands are present.
Types of cells:
i) Mucous neck cells ? Located just below gastric pit.
- Columnar in shape
- Contain mucinogen
- Produces soluble mucus
? Parietal or oxyntic cells:
? Large ,rounded or pyramidal in shape
? Found in upper half of gastric gland.
? Secretes HCL and intrinsic factor. Intrinsic
factor combines with vitamin B12
? Chief or zymogenic cells:
? - Located in the lower 1/3rd of gastric glands
? - Secrete pepsinogen which is converted into
pepsin in an acid environment.
? Enteroendocrine and APUD cells:
- Located in the basal portion of gastric glands
- Secretes serotonin, histamine and gastrin.
These are endocrine cells which release their
products into the blood vessels.
c)Mucularis mucosae--
It consists of two thin layer of smooth muscles.
Outer longitudinal
inner circular
SUBMUCOSA:
Consists of blood vessels, lymphatic vessels
and Meissner's plexus.
MUSCLE LAYER:
Inner: Oblique
Middle: circular
Outer: Longitudinal
SEROSA:
Outermost layers which consists of loose
connective tissue covered by mesothelium
DUODENUM
? Mucosa--villi (finger like mucosal projection)
--Intestinal gland (crypts of lieberkuhn)
? Submucosa--Duodenal gland (Brunner's gland)
present
? Secrete alkaline mucus that protect the mucosa
from acid secreted by stomach.
? Also secretes human epidermal growth factor
(which decreases HCL sec ).
JEJUNUM
? Villi are tongue
shaped and long
? Absence of
Brunner's
glands.
ILEUM
? Presence of
lymphoid
aggregations in
lamina propria
known as Peyer's
patches.
? Villi are short &
finger like
LARGE INTESTINE
? It consists of: appendix, colon, rectum and anal canal.
? Mucosa: Absence of Plicae circulares and villi
Presence of Microvilli
Presence of Crypts of Lieberkuhn
Presence of Goblet cells in large number
? Submucosa
? Muscle layer:
Inner circular layer - thin compared to small intestine.
Outer longitudinal layer- forms Taenia coli.
? Adventitia: Appendices epiploicae (peritoneum forms
pouch like processes filled with fat)
APPENDIX
? A small blind-ending diverticulum.
? Large accumulations of lymphoid tissue in
lamina propria which may extend into submucosa.
? Intestinal villi are usually absent.
? Crypts are poorly formed.
? Muscularis externa is thin.
? Absence of taenia coli.
This post was last modified on 30 November 2021