Histology Lab. looking at microscopic pictures of tissues, for more information use Junqueira book and you can use BlueHistolgy website

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1 Done By: Aseel Twaijer & Laith Sorour Histology Lab *These notes help in differentiating tissues and you must read them while looking at microscopic pictures of tissues, for more information use Junqueira book and you can use BlueHistolgy website oral cavity * in the 4th week stomodeum which is covered by two layers: endoderm and ectoderm ruptured and made an opening for the oral cavity (the mouth was closed by a membrane then it was ruptured) *part of the ectoderm(ectoderm on the outside while endoderm on the inside) made a small invasion inside the mouth that's why some parts of the oral cavity has stratified squamous mucosa. * same thing in proctodeum(7th week) when the membrane ruptured the cells from the ectoderm went inside this why the lining of the oral cavity and the anus is keratinized S.S.E. *All the oral cavity is non-keratinized S.S.E except the dorsum of the tongue, hard palate, attached gingiva of the teeth (the first line of the gum just beneath the tooth ) Esophagus the lining of the GI from the internal to external : 1- mucosa

2 tunica mucosa tunica propria(loose areolar connective.t) muscularis mucosa( very thin single layer of circular smooth muscle in some areas they're 2) Submucosa (mucous secreting glands) 3) muscular layer inner circular outer lingitudinal 4) serosa (advintitia ) serous secreting membrane mesothelial cells secrete the lubricating fluid and a thin layer of connective tissue. *those four layers started from the abdominal part of the esophagus (this part of the esophagus has serosa the rest doesn t have. the esophagus is non-keratinized stratified epithelium lamina propria containing few amounts of mucous secreting glands(cardiac esophageal glands). serosa only found in the part of the esophagus under the diaphragm 2 *cm(abdominal esophagous) *muscularis: upper half has skeletal muscle and no serosa middle : mixed skeletal with smooth muscle lower half: the part of it above the diaphragm purely smooth muscle no serosa lower to the diaphragm we have serosa coming from the peritoneum stomach mucosa lining simple coloumner lamina propria : lots of glands here unlike the esophagus **for comparison : esophagus has prominent glands in submucosa and few in L.propria while in stomach lots of gland in L.propria and few in submucosa Submucosa: C.T few glands not prominent in number muscularis: circular/longitudinal/oblique

3 serosa **in stomach the lining has gastric pits(invagination) near the submucosa while in S.intestine it's evaginations (villi:extention to the outside) isthmus :the beginning of the isthmus is mucous secreting glands thickness nearly 1 cm to protect the stomach from auto-digest The part in the middle is called the neck: stem cells so close to the surface that's one of the mechanisms why stomach doesn t digest itself (turnover) *the first line of defense in stomach is the turnover of the cells not mucosa the base of the gastric pits we find glands : parietal(eosinophilic),chief(violet nucleus ) *any nucleus secretes protein we find prominent nucleus intense basophilia the nucleus itself is pale but the Nucleolus is dark * a lot of endocrine secreting cells Small intestine: it is divided into 3 parts(divisions :duodenum\jejunum\ileum) with same lining

4 and some similarities similarities: **Mucosa: Lining: simple columnar Lamina propria containing a lot of glands *Villi *pilca circularis= mucosa + submucosa folded in inner semi-circular line (found in all small intestine so doesn t help us to differentiate between its divisions) *inner and outer muscles *serosa (it s a connective tissue with mesothelium(very flattened squamous cells), it doesn t help us in differentiation,found in abdomen under the diaphragm until Anus(no serosa in anus)). Duodenum: *Contains Brunner glands in sub-mucosa (tubular branching mucus secreting gland) *Villi is leaf-like unlike in jejunum & ilium which is finger-like(this helps in theory but not under microscope) Jejunum: If we don t find Brunner glands(we see it in duodenum) and peyer patches (we see it in ilium ) then its Jejunum. Ilium: -finger-like villi under it submucosa with no glands but with Peyer patches

5 (lymphocyte follicles with germinal centers) Large intestine : -villi is not prominent as in small intestine containing goblet cells lined with mucus secreting glands -sometimes lymphoid follicles specially in appendix Accessory glands of the digestive system: Liver, pancreas and gallbladder Gallbladder : continuation with digestive system lined with simple columnar,have extensive muscular layer (CCK works on it and makes it contract physiology) Liver: *Second largest Organ after the skin *Largest Gland in the body have connective tissue capsule, and any capsule makes septa into the organ separating it by lobes and lobules. -Hepatocytes which origin is simple cuboidal epithelium arranged into Hexagonal plates radiated around Central vein and at each corner have portal triad (Portal vein\bile duct\hepatic artery)

6 Liver Pancreas : **almost identical to parotid gland those notes are for theory : *pancreas doesn t have striated ducts *in parotid gland the intercalated ducts came out from secretory portion unlike in pancreas it inserted the secretory portion making centroacinar portion *there is islets of langerhamn in pancreas but not in parotid gland