Histology of GIT I

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

Composed1.Layer of epithelium2.Areolar connective tissue3.Muscularis mucosae

Consists areolar connective tissue that bind the mucosa to muscularisHighly vascular & contain submucosal plexus.

Skeletal muscle- mouth, pharyx, superior and midddle of esophagus

Smooth muscle- 2 sheet; inner(circular fiberOuter( longitudinal)

Serous membrane that composed aerolar connective tissue & simple squamous epithelium

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 (myenteric) plexus in between

same as duodenum same as duodenum

submucosaBrunner'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. Villi very long.

Similar to duodenum. 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.