Histology of GIT I

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HISTOLOGY OF GIT I
PROF. DR. FAUZIAH OTHMAN
DEPT OF HUMAN ANATOMY
FPSK
CONTENT
Histology of the:
- oral cavity
- pharynx
- peritoneum
- oesophagus
- stomach
- small intestine
- large intestine
Digestive System
Digestive System
Structures involved in digestive system

The digestive system of mammals consists
of the following:
-(mouth, oral cavity, pharynx, esophagus,
stomach, small intestine, large intestine,
rectum, anus)
-also includes other associated
structures/organs/glands (salivary
glands, gall bladder, liver, pancreas).
Function of Digestive System
 Digestion
is the process of breaking
down food into molecules small enough for
the body to absorb.
Oral Cavity Diagram
uvula
Oral Cavity
Salivary glands produce
large amounts of saliva

Saliva contains:
 water for moistening food
 Mucus for lubricating food and binding it into a bolus
(ball of mush)
 salivary amylase to start the breakdown of starch

taste buds
ORAL CAVITY

Oral or buccal cavity:


Is bounded by lips, cheeks, palate, and tongue
To withstand abrasions:
The mouth is lined with stratified squamous
epithelium
 The gums, hard palate, and dorsum of the tongue are
slightly keratinized

How is food swallowed?
Food moves to the pharynx, (throat) which in
humans, leads to both the trachea and the
esophagus.
 While food is being swallowed, the epiglottis blocks
the trachea and the uvula blocks off the nose.
 Then food reaches the esophagus,(tube that
connects the pharynx to the stomach)

(throat)
uvula
Oral Cavity of Pig
PHARYNX
 Lined
with stratified squamous
epithelium and mucus glands
 Has


two skeletal muscle layers
Inner longitudinal
Outer pharyngeal constrictors
PERITONEUM

Peritoneum – serous membrane of the abdominal
cavity
Visceral – covers external surface of most digestive
organs
 Parietal – lines the body wall


Simple squamous epithelium
OESOPHAGUS
Esophageal mucosa – nonkeratinized stratified
squamous epithelium
 The empty esophagus is folded longitudinally and
flattens when food is present
 Glands secrete mucus as a bolus moves through
the esophagus
 Muscularis changes from skeletal (superiorly) to
smooth muscle (inferiorly)

GENERAL HISTOLOGY OF GIT
Consist of 4 layer arrangement of tissue.
1.
Mucosa
2.
Submucosa
3.
Muscularis
4.
Serosa

Mucosa
Submucosa
Muscularis
Serosa
Composed
1. Layer of
epithelium
2. Areolar
connective
tissue
3. Muscularis
mucosae
Consists areolar
connective tissue
that bind the
mucosa to
muscularis
Highly vascular &
contain
submucosal
plexus.
Skeletal musclemouth, pharyx,
superior and
midddle of
esophagus
Serous membrane
that composed
aerolar connective
tissue & simple
squamous
epithelium
Smooth muscle- 2
sheet;
inner(circular fiber
Outer( longitudinal)
Stomach
The stomach has several muscle layers
surround the stomach, serving to churn food.
 The stomach can expand to hold about 2 L of food
(= 1/2 gal). It contains acid to digest food (ph = 2)
and enzymes to breakdown protein.

Stomach diagram
Sphincters

The cardiac sphincter closes off the top end of
the stomach and the pyloric sphincter closes
off the bottom
Lower digestive tract of the pig
Lower digestive tract of pig
STOMACH
The stomach has three layers of muscle:
•
an outer longitudinal layer,
•
a middle circular layer,
•
an inner oblique layer.
The inner lining consists of four layers:
•
the serosa,
•
the muscularis,
•
the submucosa, and
•
the mucosa.

The mucosa is densely packed with gastric
glands, which contain cells that produce digestive
enzymes, hydrochloric acid, and mucus.
Small Intestine and accessory organs



Small intestine A lot of digestion happens here. S. int. secretes
enzymes and pancreas/gall bladder dump enzymes into duodenum to
continue digestion.
Liver- The largest internal organ of the body. Makes bile, which
aids in the digestion of fat. Detoxifies poisons like alcohol. Stores
extra glucose in the form of glycogen.
Gall Bladder- Sack on the bottom of one of the liver lobes. Stores
bile until it is ready to move into the duodenum.
Pancreas- Makes digestive enzymes that are dumped into
duodenum of the small intestine. Makes the hormone, insulin, which
regulates the amount of sugar in the blood.
Small Intestine




SECTIONS OF THE SMALL INSTESTINE
Duodenum- The first part of the small intestine which has ducts
(tubes) leading into it from the liver/gall bladder and pancreas.
Bile and pancreatic enzymes are mixed with food here.
Jejuno-ileum- All the small intestine except for the duodenum.
Digestion of food is completed here and nutrients are absorbed
through its walls into the blood stream.
Caecum-a pouch off the digestive tract between the small intestine
and the colon. Produces enzymes that digest cellulose. (is the
appendix in humans)
SMALL INTESTINE

Small intestine, which has three parts:
Duodenum
 Jejunum
 Ileum

 The
epithelial
component of the
small intestine is
composed of villi
(finger like
projections) and
crypts (crypts of
Liberkuhn).
Layer
Duodenum
Jejunum
Ileum
serosa
normal
normal
normal
muscularis externa
longitudinal and
circular layers, with
Auerbach's
same as duodenum
(myenteric) plexus in
between
same as duodenum
submucosa
Brunner's glands and
Meissner's
no BG
(submucosal) plexus
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. Similar to duodenum.
Villi very long.
Villi very short.
LARGE INTESTINE

Large intestine, which has three
parts:
Cecum (the vermiform appendix is attached
to the cecum).
 Colon (ascending colon, transverse colon,
descending colon and sigmoid flexure)
 Rectum

Plicae circularis (valves of Kerckring) –
transverse semilunar folds that contain a core of
submucosa
Large Intestine
The large intestine or colon functions to re-absorb
water.
 Bacteria live here like Escherichia coli (E. coli) which
produce gases as they ferment their food.
 Occasionally, some of this gas is released. As these
bacteria digest/ferment left-over food, they secrete
beneficial chemicals such as vitamin K, Vitamin B,
and some amino acids, and are our main source of
some of these nutrients.

Sections of Large Intestine


Spiral colon-spiraled part of the large intestine.
Absorbs water, vitamins, and minerals from the food
and moves them into the bloodstream.
Descending colon- The part of the large intestine
leading from the spiral colon down to the rectum.
Same function as the spiral colon.
STRUCTURE OF LI;
simple columnar epith
 Crypts of Leiberkuhn
 lymph tissue (GALT)
 goblet cells

NO kerckring folds or villi or paneth cells
 Layers: Mucosa, Submucosa, Musc. Ext, and
either serosa & adventia

Large Intestine Diagram
Rectum of digestive tract of the pig
Rectum


The rectum is the end of the large intestine and functions for
storage of the feces, the wastes of the digestive tract, until these
are eliminated.
The external opening at the end of the rectum is called the anus.
The anus has two sphincters, one voluntary and one involuntary.
The pressure of the feces on the involuntary sphincter causes the
urge to defecate and the voluntary sphincter controls whether a
person defecates or not.
COLON
The colon is characterized by mucosal folds that are no longer called
villi. These are lined by many GOBLET CELLS and fewer ABSORPTIVE
CELLS. The glands are shorter in the colon than in the small
intestine. There are no Paneth cells.
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