Download Histology Ass. Lec. Dentistry College Lec-7

Histology
Lec-7-
Ass. Lec.
Wafaa H. M. Alhashimy
Dentistry College
Second Stage
Digestive system : oral cavity , salivary glands ,esophagus and stomach
The digestive system is long , hollow tube or tract that starts at the oral cavity and
terminates at the anus . the system consists of the oral cavity , esophagus , stomach ,
small intestine , large intestine , rectum and anal canal . associated with the
digestive tract are the accessory digestive organs : the salivary glands , liver and
pancreas .
The oral cavity
In the oral cavity , food is ingested , masticated (chewed ) and lubricated by saliva
for swallowing . because food is physically broken down in the oral cavity , this region
is lined by a protective , non keratinized stratified sequamous epithelium .
The lip
The lip lined by stratified sequamous epithelium, sub-epithelium is connective tissue
,in deeper connective tissue contains blood vessel are very closed to the surface giving
the lip a red color, under lying is adipose tissue. The core of the lip is skeletal muscle
called orbicularis oris.
The part of the lip:
-The outer region is thin skin a stratified sequamous keratinized epithelium. C.T.
contains hair follicles , sebaceous glands and sweat glands.
-The intermediate region (free margin) of the lip coverd the a stratified sequamous
non keratinized.
- Inside region a stratified sequamous non keratinized oral epithelium , in deeper C.T.
of the lip are found labial glands, tubuloacinar mucus - secreting forbmoisten the oral
mucosa. The epithelium of inner surface thicker than the outer surface.
The tongue
The tongue is muscular organ located in oral cavity. The core of the tongue consists
of connective tissue and interlacing bundles of skeletal muscle fibers are random
distribution of individual skeletal muscle fibers in the tongue for increased movement
during chewing , swallowing and speaking .
Outer layer is the mucosa composed of epithelium and lamina properia (loose C.T.)
The epithelium on the ventral surface of the tongue is smooth , the epithelium on the
dorsal surface of the tongue is irregular or rough because contain numerous papillae
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The posterior one third of the dorsal surface of the tongue is separated from the
anterior two thirds by the V-shaped sulcus terminalis.
Type of papillae Tongue
All papillae on the tongue are coverd by stratified seaquamous epithelium that
shows partial or incomplete keratinization .these intended by lamina properia. there
are four types of papillae are found on the tongue :
filiform : most numerous , smallest , elongated conical shape, found in rows parallel
to the median sulcus but do not contain taste buds.
fungiform : fewer in number than filiform , larger , mushroom shaped and contain a
few taste buds on their , most numerous near the tip of the tongue.
circumvallate : largest papillae , surrounded by a deep, circular furrow, located along
the sulcus terminalis and number from 7-12. Contain Taste buds are located in its
lateral surface. Numerous ducts of Serous Ebner's glands drain a watery fluid
containing lipases .
foliate : poorly developed in humans .
Taste buds
are pale, barrel-shaped intraepithelial bodies that extend from the basal lamina to the
surface that opening by the taste pore. In taste bud containing a neuroepithelial cell
(taste cell) have in apices numerous microvilli that protrude through the taste pore,
support cells and basal cells (stem cell).
The major salivary glands
salivary glands are located outside of the oral cavity and convey their secretions into
the mouth via large excretory ducts. There are three major salivary glands :
- Paired of parotid gland: are the largest of salivary glands, located anterior and
inferior to the external ear. Secreted purely serous gland
- Paired of submandibular gland (submaxillary): are smaller, located inferior to the
mandible in the floor of the mouth. Secreted mixed gland serous & mucous.
Aggregation of sublingual gland: are the largest of salivary glands, located inferior to
the tongue. Secreted mixed gland serous & mucous.
salivary glands are composed of cellular secretary units called acini and numerous
excretory ducts (intercalated Ducts , striated Ducts , Excretory intralobular Ducts ,
interlobular and interlobar Ducts).
There are two type of the cells of a cini:
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Serous cells: are pyramidal shape, rounded nucleus in the base, secreting granules in
apices' cytoplasm.
Mucous cells: are similar in shape serous cell, except their cytoplasm filled with light
stain mucus.
Where mucus cells predominate , serous cells form a moon-shaped cap over the
mucous cells called serous demilune.
Myoepithelial cells are flattened cells with branched and contractile surround both
serous and mucous acini.
Tonsil (palatine, pharyngeal, and lingual).
Esophagus
The layers of the oesophagus are as follows:




mucosa
o nonkeratinized stratified squamous epithelium: is rapidly turned over, and
serves a protective effect
o lamina propria:loose C.T.
o muscularis mucosae: smooth muscle .
submucosa: Denes irregular C.T., Contains the mucous secreting glands
(esophageal glands).
muscularis externa (or "muscularis propria"): composition varies in different
parts of the esophagus, to correspond with the conscious control over
swallowing in the upper portions and the autonomic control in the lower
portions:
o upper third, or superior part: striated muscle
o middle third, smooth muscle and striated muscle
o inferior third: predominantly smooth muscles
adventitia
Gastroesophageal junction
The junction between the esophagus and the stomach (the gastroesophageal junction
or GE junction) is not actually considered a valve, although it is sometimes called the
cardia or cardias.
Stomach
The three histologic regions of the stomach are the cardia , the fundus and body and
the pylorus. the stomach wall are:
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mucosa
The first main layer. This consists of the epithelium and the lamina
propria (loose connective tissue), with a thin layer of smooth
muscle called the muscularis mucosae separating it from the
submucosa .
submucosa
consists of fibrous connective tissue, The Meissner's plexus is in
this layer .
the muscularis externa has three layers of smooth muscle instead
of two.

muscularis
externa


serosa
inner oblique layer: This layer is responsible physically
breaks down the food .
middle circular layer: the pylorus is surrounded by a thick
circular muscular wall ,which controls the movement of
chyme into the duodenum. Auerbach's plexus (myenteric
plexus) is found between the outer and middle layer.
outer longitudinal layer
consisting of layers of connective tissue continuous with the
peritoneum.
Gastric glands
Different types of cells are found at gastric glands:
Layers of
Name
gland
parietal cells
Isthmus
Secretion
gastric acid and intrinsic factor, Acidophilic
Mucous neck
mucus gel layer
cells
fundus
chief cells
pepsinogen, Basophilic
enteroendocrine Defferent hormones to regulate digestive
fundus
cells
system as gastrin, histamine, and somatostatin
Rugae is temporary folded of the submucosa of stomach when the stomach is empity
formed when contraction of smooth muscle layer .
neck
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Not:serosa covers lower esophagus , stomach ……to colon while adventitia upper part
of esophagus and posterior wall of colon.
stomach
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