Digestive system
. The muscle fibers cross one another in three planes; they are grouped in bundles, usually separated by connective tissue. Because the connective tissue of the lamina propria penetrates the spaces between the muscular bundles, the mucous membrane is strongly adherent to the muscleFILIFORM PAPILLAE
The upper surface of anterior two third shows small projections called papillae which are four types: Filiform papillae. Fungiform papillae. Circumvallate papillae. Foliate papillae.FUNGIFORM PAPILLAE:
CIRCUMVALLATE (VALLATE) PAPILLAETaste bud
Three types of cells in the taste bud:- Taste cells (sensory cells). Supporting- sustentacular cells Basal cells( primitive stem cells) can replace the two cells, lie at the base of the bud, rounded in shapeOESOPHAGUS:
In humans the esophagus is covered by nonkeratinized stratified squamous epithelium .In general, it has the same layers as the rest of the digestive tract.
Gastro esophageal junction
Parietal cell(pc) and chief cell( cc)Fundus and Body: Surface epithelium is thrown into short gastric pits; the lamina propria is filled with long straight tubular gastric glands some of them open at the bottom of the gastric pits.
Cardia: . Its mucosa contains simple or branched tubular cardiac glands... the surface epithelium composed of mucous-secreting cells with few parietal cells.
Gastric esophageal junction
Fundus and BodyPylorus This region shows deep gastric pits into which open tubular mucous glands extending down to the muscularis mucosa similar to the cardiac glands.These glands are lined by mucous cells and scattered parietal cells particularly close to the pyloric sphincter, the glands secrete mucin and enzyme lysozyme.
Small intestine
Mucosa:- the small intestine shows structural modification to increase it’s surface area for absorption, so the lining mucosa and submucosa are thrown into numbers of folds or plicae which are most prominent in the jejunum .the surface of plicae arranged into intestinal villi which are long outgrowths of the mucosa consists of epithelium and lamina propriaLymphatic lacteal
The epithelium of the villi is continuous with that of intestinal glands and consists of 5 types of cells:-
Enterocytes ( absorptive cells) :-Tall columnar cells with rounded nuclei, the apex of the cells shows brush border consists of about 3000 microvilli, the cytoplasm contains mitochondria, Golgi apparatus, Lysosomes and ribosoms. Goblet cells:-Lie between the absorptive cells and increase in number in the jejunum and ileum and most numerous in the terminal ileum. The cytoplasm is fully expanded with mucin
Paneth cells :-have basal nuclei and prominent large eosinophilic granules in their apical cytoplasm, these granules secrete lysozyme which protects against infection.
Jejenum: is the main absorptive site, finger like villi, plicae (most prominent).
Duodenum: entirely retroperitoneal, leaf shaped villi, Brunner’s gland in the submucosa,.Duodenum Brunner's gland
Ileum: aggregation of lymphoid tissue to form large nodules called (Peyer’s patches)Large intestine Mucosa:The epithelium of large intestine: contains no folds and no villi but there is a mixture of absorptive cells and mucous cells (goblet cells) arranged as simple, straight, non branching tubular glands (intestinal glands).
goblet cells are filled with large mucin granules
The absorptive cells are columnar and have short irregular microvilli, they are less numerous because they are compressed between the large mucous (goblet cellsThe appendix is a blind- ending tubular diverticulum arising from the cecum, it has a narrow lumen caused by the presence of lymphoid follicles in its wall
Anal canal lined by columnar epithelium at it’s upper end and this changes to a non keratinizing stratified squamous epithelium at the level of pectinate or dentate line in this line , the mucous membrane forms a series of longitudinal folds, the rectal columns of Morgagni. Small branched tubular (anal glands) open into the anal canal just above the pectinate line
Anal canal
salivary glandSerous cells are usually pyramidal in shape, with a broad base resting on the basal lamina and a narrow apical surface with short, irregular microvilli facing the lumen. Adjacent secretory cells are joined together by junctional complexes and usually form a spherical mass of cells called acinus, with a small lumen in the center Mucous cells are usually cuboidal to columnar in shape; their nuclei are oval and pressed toward the bases of the cells. In the human submandibular and sublingual glands, serous and mucous cells are arranged in a characteristic pattern,The mucous cells form tubules, but their ends are capped by serous cells, which constitute the serous demilunes cells