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WEEK 2:
Structure and function of GI tract:
| Question | Answer |
|---|---|
| role of GIT | ingest food and break it down mechanically and enzymatically into molecules so it can be absorbed into blood to liver to synthesise proteins, carbohydrates and lipids |
| layers making up the GIT | inner lining mucosa, support submucosa, muscle (muscularis externa), outer wrapping (adventitia/ serosa), and lamina propria |
| where is the enteric nervous system found in layers of GIT | in support submucosa and muscle (muscularis externa) |
| where is lymphoid aggregation found in layers of GIT | in inner lining mucosa |
| mucosa consists of (3) | epithelium and basement membrane, lamina propria, and muscularis mucosa |
| describe the epithelium and basement membrane in mucosa | changes throughout the tube in relation to function |
| describe the lamina propria in mucosa | supports epithelium structurally and nutritionally |
| describe the muscularis mucosa in mucosa | typically an inner circular and an outer longitudinal layer of smooth muscles |
| functions of epithelium in GIT | protection and secretion |
| protective epithelium in GIT | oral cavity and pharynx, oesophgus, anal canal (stratified squamous non kertainising) |
| secretory epithelium in GIT | stomach (simple columnar cells organised to be glandular) |
| protective epithelium is made of | stratified squamous non kertainising |
| secretory epithelium is made of | simple columnar cells |
| ducts | cuboidal |
| generally secretory portion | columnar |
| types of glands (shapes) | simple tubular simple acinar, compound tubular, and compound acinar |
| absorptive epithelium in GIT in small intestine | small intestine has villi and crypts (glands) lined by columnar cells (enterocytes) specialised for absorption (microvilli) |
| absorptive/protective epithelium in GIT in large intestine | large intestine has lots of goblet cells for lubrication of faeces and has enterocytes to absorb water |
| where is lymphoid tissue located | lamina propria |
| GALT | gut associated lymphoid tissue |
| how does GALT range | from individual cells (T lymphocytes and macrophages) to large aggregates composed of T and B lymphocytes |
| Peyer's patches | feature of ileum of small intestine overlaid by antigen sampling cuboidal cells |
| submucosa consists of | connective tissue, blood vessels, lymphatics and nerves, some having glands (oesophagus and duodenum), and submucosal (Meissner's) plexus to supply glands and muscularis mucosa |
| which organs have glands in their submucosa | oesophagus and duodenum |
| what supplies the glands and muscularis mucosa | submucosal (Meissner's) plexus |
| Brunner's glands/ Duodenal glands are found where | in submucosa |
| muscularis externa/ propria consists of | smooth muscle (inner circular and outer longitudinal) |
| describe pattern of inner smooth muscle in muscularis externa/ propria | circular |
| describe the pattern of outer smooth muscle in muscularis externa/ propria | longitudinal |
| muscularis externa/ propria responsible for | movement of food along gut tube (peristalsis) |
| muscularis externa/ propria (in stomach) is modulated by | ANS via Myenteric (Auerbach's) plexus between muscle layers to modulate peristalsis |
| muscularis externa of stomach consists of smooth muscle including | inner oblique, middle oblique, and outer longitudinal |
| sphincters | thickening of smooth muscle |
| oesophagegastric sphincter function | prevents reflux of stomach contents |
| pyloric sphincter | found between stomach and duodenum and controls release of food |
| ileocaecal sphincter found | between small and large intestine |
| internal anal sphincter | upper anal canal responsible for retaining faeces |
| adventitia | outer wall of gut tube composed of thin layer of connective tissue |
| serosa | found where covered by a serous membrane |
| serous membrane is made of | squamous epithelial cells (mesothelium) secreting a small amount of fluid allowing organs to glide over each other |
| mucosa in oral cavity includes | masticatory epithelium, lining epithelium, specialised mucosa, lamina propria, and NO muscularis mucosa |
| masticatory epithelium in oral cavity | keratinised and parakeratinised stratified squamous with different masticatory surfaces (gingivae, hard palate, dorsum of tongue) which retain nuclei in upper layers to give whitish colour |
| lining epithelium in oral cavity | non keratinised stratified squamous (in lips, cheeks, floor of mouth and soft palate) |
| specialised mucosa in oral cavity | in dorsal tongue, taste buds, papillae - all composed of keratinised stratified squamous epithelium |
| what does the oral cavity lack | muscularis mucosa |
| lips is made of | fold of skeletal muscle (orbicularis oris) covered by keratinised squamous making reddish portion between most inner surface and facial skin |
| submucosa of oral cavity contains | small salivary glands (posing as origin of adenocarcinoma) |
| tongue is | bulk of interlaced bundles of skeletal muscle |
| muscles in tongue | intrinsic and extrinsic |
| intrinsic muscles of tongue responsible for | changing shape of tongue |
| example of extrinsic muscle in tongue | palatoglossus |
| mucosa in tongue | in anterior dorsal surface and has masticatory epithelium with papillae |
| taste buds in tongue | abundant in circumvallate papillae but absent in filiform papillae |
| papillae types in tongue types (4) | filiform, fungiform, circumvallate, and foliate papillae |
| how many taste receptor cells in one taste bud | 50-100 |
| taste buds consist of | long microvilli (present at apex of receptor cells) |
| taste buds only open where | taste buds only open to surface via taste pore |
| what nerve penetrates the base of taste bud | sensory nerve fibres |
| types of glands in salivary glands | major and minor |
| parotid salivary glands | secretes via parotid duct (Stensen's) with serous secretion |
| submandibular salivary glands | secretes via submandibular (Wharton's) duct with mixed muco-serous secretion (more serous) |
| sublingual salivary glands | mixed muco-serous secretion (more mucous) |
| pharynx epithelium | non keratinised stratified squamous which contains a small number of taste buds |
| regions of pharynx | naso, oro, and laryngo - pharynx |
| where are long microvilli present in taste bud tongue | apex of receptor cells |
Created by:
22tango
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