Histology of GIT I
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Transcript of 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.