GIT 1 By: Dr Hossam El-deen Salem

The subdivisions of the tongue are based on embryologic origins: Anterior two-thirds (body) posterior one-third (root) They are separated by the sulcus terminalis.

The tongue is considered as a "bag" of mucous membrane packed with striated muscle fibers running in all directions

Structure of tongue Mucosa  stratified squamous epithelium on both surfaces.  The dorsal surface forms papillae Submucosa  Has minor salivary glands that secrete both mucous and serous secretions. Muscles  Core of striated muscles running in all directions Minor salivary glands  In submucosa of cheek : called buccal glands  In submucosa of lips: called labial glands  In submucosa of tongue: called lingual glands

Structure Each consists of a connective tissue core covered by stratified squamous epithelium. Lingual Papillae

Filiform papillae (Cone-shaped)  Most numerous; all over the tongue.  No taste Buds Fungiform papillae (Mushroom shaped)  Less numerous; present on tip and sides of the tongue  Has taste buds

Fungiform papillae on tip and sides of tongue

Circumvallate papillae (surrounded by a wall, vall=wall)  papillae located (on a v-shaped line) just anterior to the sulcus terminalis.  Large circular papillae, each is surrounded by a deep groove  Has taste buds.  Serous acini (called Von Ebner’s glands) open into the groove to dissolve food particles, so help tasting

Circumvallate papilla. B= taste Buds

Section in the tongue : Notice striated muscles in all directions, filiform and circumvallate papillae are shown (rectangle)

Circumvallate papillae (short arrow) and Fungiform papillae (long arrow)

Foliate papillae Rare in humans

Notes on Lingual papillae filiform = thread-like fungiform = mushroom-like cirumvallate = surrounded by a wall foliate = paper-like The most numerous type (filiform) has NO taste buds and can not receive taste senstaions All other types have taste buds, So we can receive taste from areas with these papillae (tip, sides, and back) Tip: sweet, salty Sides: sour Back: bitter (circumvallate)

onion-shaped structures in the epithelium of lingual papillae e.g.fungiform and circumvallate papillae. Function  Taste buds contain taste cells that communicate with the surface of the papilla through a taste pore.  stimulation of the taste cells leads to the stimulation of gustatory nerve fibers and receiving sweet, salty, bitter, and sour sensations Taste buds

Cells in taste buds  Taste cells: pale cells, with pale nuclei. On apex, microvilli directed towards taste pore, On base surrounded by sensory nerve fibers of taste sensation  Supporting cells: dark cells with dark nuclei, theses cells are present in the periphery of taste buds  Basal cells: They are undifferentiated stem cells that may be differentiated to other types of cells Taste buds General rules, before proceeding Whenever you find dark-staining cells together with pale-staining cells, usually the pale staining are the active ones, and the dark staining are supportive Whenever you find short cells together with tall cells, usually short (basal) cells are stem cells for the others

General structure of GIT wall

I. Mucosa (= mucous membrane) Epithelium Lamina propria: Connective tissue Muscularis mucose (= the muscle of mucosa).It causes folding of mucosa NOT peristalsis General Structure of GIT II. Submucosa Connective tissue May contain glands (eg in esophagus, duodenum), or lymphoid nodules (eg in ileum). Contains Meissner's plexus (Autonomic controlling secretion of glands) III. adventitia or Serosa Connective tissue If covered by a peritoneal layer, it is called serosa III. Musculosa Usually inner circular, and outer longitudinal layers of smooth muscle Responsible for peristalsis of intestine Contains Auerbach's myenteric plexus between inner and outer layer (Autonomic controlling peristalsis)

structure of the esophagus

I. Mucosa (= mucous membrane) Epithelium : stratified squamous epithelium non-keratinized. Lamina propria: Connective tissue Muscularis mucose (= the muscle of mucosa). Usually inner circular, and outer longitudinal layers Structure of esophagus II. Submucosa Connective tissue Oesophageal glands in submucosa secrete mucous secretion III. Adventitia Connective tissue thin adventitia of connective tissue that binds it to adjacent structures. III. Musculosa Inner circular, and outer longitudinal layers of muscles The muscle fibers o f the top 1/3 of the esophagus is striated and that of the bottom 1/3 is smooth. In the middle 1/3 both kinds are found.