GIT Flashcards
The GI Tract consists of
Mouth (oral cavity) Oesophagus Stomach Small intestine (duodenim, jejunum, ileum) Large intestine (colon, caecum) Rectum Anus
Lip Skin
: keratinized stratified squamous epithelium. Contains hair follicles, sebaceous glands, sweat glands.
Lip Vermilion Border
Very thin keratinized epithelium. Contains dilated venules and veins, but lacks salivary glands.
Lip Oral Mucosa
Most-surface, covered by nonkeratinized stratified squamous epithelium. Labial salivary glands in submucosa.
Oral Mucosa
thick stratified squamous epithelium, supported by a lamina propria
In mobile areas, such as the soft palate, underside of the tongue, floor of the mouth, and mucosal surfaces of the cheeks and lips, the epithelium is not keratinised, although in some places it may be parakeratinized.
• In other areas, such as the gums (gingivae), hard palate, and most of the upper surface of the tongue, the epithelium is keratinised and, in some areas, parakeratinized.
• Underneath the oral mucosa, there is a tough collagenous submucosal layer, with accessory salivary glands, except where the oral mucosa lies over bone, where the submucosa is thin.
Tongue Dorsal Surface
Lingual Muscles: Striated • Extrinsic
• Intrinsic
Sulcus Terminalis
• V-shaped depression which divides tongue into anterior 2/3 and posterior 1/3. Foramen caecum at its apex.
Lingual papillae on the anterior 2/3 • Filiform
• Fungiform
• Circumvallate
• Foliate
Taste buds associated with select papillae
Lingual Papillae Filliform
Small and Conical • Lined by keratinized stratified squamous epithelium • No taste buds • Mechanical function
Lingual Papillae Fungiform
Fungiform
• Mushroom shaped
• Prominent on tip of tongue
• Lined by stratified squamous epithelium
• Taste buds in the epithelium on dorsal surface
Lingual Papillae Foliate
- Found on the lateral edges of tongue • Parallel rows separated by deep clefts • Taste buds
- Rudimentary in human
Lingual Papillae Circumvallate
8 to 12 large and dome shaped found anterior to sulcus terminalis
• Surrounded by a moat-like invagination which receives ducts of serous Von Ebner’s glands
• Taste buds in epithelium of lateral surface
Taste Buds
Composition: • Taste pore • Three types of cells: • Sensory neuroepithelial cells • Synapse with afferent neurons: CN VII, IX, X • Microvilli on apical surface • Express 1 class of receptor protein • Turnover ~ 10 days • Supporting cells • Microvilli on apical surface • Turnover ~ 10 days • Basal cells • Stem cells
Teeth Odontoblasts
Tall columnar secretory cells near pulp cavity.
Produce dentine, which is laid down and then calcified. Dentine - 90% type I collagen, 70% wet weight hydroxyapatite.
Teeth Ameloblasts
Tall columnar secretory cells from ectodermal origin near surface tooth
Produce enamel.
Enamel - 96% mineralised, hydroxyapatite the primary mineral, does not contain collagen.
Ameloblasts die when the tooth erupts
Parotid Glands Acini
Pure serous gland
• Only serous cells (protein-secreting) in acini.
• Serous cells produce e.g. Amylase (carbohydrates)
• Amylase stored apical in acidophilic secretory granules
• Granules also contain peroxidase, lysozyme, cystatins
Parotid Glands Ducts
Secretory acini – Intercalated ducts – Intralobular or Striated ducts – Interlobular ducts – Major ducts
• The parotid gland has the longest intercalated ducts
• Myoepithelial cells around acini
Submandibular Glands Acini
Mixed gland
• Mostly pure serous acini, but also groups of mixed acini
among the pure serous acini.
• Serous cells (protein-secreting) are filled with prominent, purplish-staining zymogen granules.
• Mucous cells (mucin-secreting) are pale-staining with abundant clear cytoplasm. Arranged in duct-like structures, capped by so-called serous demilumes.
Submandibular glands Ducts
Intercalated ducts are short, but present; striated ducts are long and clearly evident.
Sublingual glands Acini
Mixed gland
ID
• Gland consist mostly of mucous acini capped with serous demilumes. The mucin-secreting cells predominate, with far less protein-secreting cells
Sublingual glands ducts
Short intercalated and striated ducts, but are few in number.
• Long excretory ducts. Multiple sublingual ducts empty directly into the floor of the oral cavity, near to or with the submandibular ducts.
M S
Oesophagus
- ~25cm long muscular tube
- Connects pharynx to stomach
- Function as a conduit for the bolus of food from the mouth
- Lumen normally collapsed with longitudinal folds
Oesophagus Mucosa
Epithelium • Stratified squamous non keratinized epithelium • Protects from mechanical and chemical injury • Lamina Propria • Connective tissue containing diffuse lymphatic tissue and lymphatic nodules • Eosophageal Cardiac Glands (NOT shown) • Present mainly in terminal part of esophagus • Produces neutral mucus which protects from regurgitated gastric contents • Muscularis Mucosae • Single layer of longitudinal muscle
Oesophagus Submucosa
Dense irregular connective tissue
• Large blood and lymphatic vessels
• Submucosal Plexus (Meissner’s plexus)
• Eosophageal Glands Proper:
• Scattered throughout the length • Produces slightly acidic mucous • Lubricates the lumen
• Excretory duct: (green arrow) lined by stratified squamous epithelium
Oesophagus Muscularis external
Typical two layers: inner circular and outer longitudinal • Upper third: striated • Middle third: striated and smooth • Lower third: smooth • Myenteric plexus (Auerbach’s plexus)
Serosa and Adventitia
- Above the diaphragm
- Fixed to adjacent structure by adventitia
- Below the diaphragm
- Serosa continuous with that of the stomach
