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Gastrointestinal tract + diseases, Watch lecture, Watch lecture for…
Gastrointestinal tract + diseases
Consisting
Mouth (oral cavity)
Oesophagus
Stomach
Small intestine (duodenum, jejunum, ileum)
Large intestine (colon, caecum)
Rectum
Anus
Lip
Skin
Keratinised stratified squamous epithelium
Hair follicles
Sweat glands
Sebaceous glands
Lubricates hair
Vermilion border
Very thin keratinised epithelium
Contains dilated venules + veins
Lacks salivary glands
Oral mucosa
Most-surface
Covered by thick non-keratinised stratified squamous epithelium
Labial salivary glands in submucosa
Supported by lamina propria
Not keratinised in mobile areas
Some areas are parakeratinised
In gum (gingivae), hard palate + upper surface of tongue it may be parakeratinised or keratinised
Under oral mucosa
Tough, collagenous submucosal layer with accessory salivary glands
No salivary glands where oral mucosa lies over bone
Submucosa is thin here
Tongue
Dorsal surface
Lingual muscles (striated)
Extrinsic
Intrinsic
Sulcus Terminalis
V-shaped depression divides tongue into anterior 2/3 and posterior 1/3
Foramen caecum at apex
Lingual papillae on anterior
Filiform
Small + conical
Lined by keratinised stratified squamous epithelium
No taste buds
Mechanical function
Fungiform
Mushroom shape
Prominent on tip of tongue
Lined by stratified squamous epithelium
Taste buds in epithelium on dorsal surface
Circumvallate
8-12 large + dome shaped
Anterior to sulcus terminalis
Surrounded by moat-like invagination
Receives ducts of serous Von Ebner's glands
Taste buds in epithelium of lateral surface
Foliate
On lateral edges of tongue
Parallel rows separated by deep clefts
Taste buds
Rudimentary (basic) in human
Taste buds associated with select papillae
Taste buds
Extend through entire thickness of epithelium
Detect taste simulating particles from food
Composition
Taste pore
3 cell types
Sensory neuroepithelial cells
Synapse with afferent neurons
CN
VII
IX
X
Microvilli on apical surface
Express 1 class of receptor protein
~10 day turnover
Supporting cells
Microvilli on apical surface
~10 day turnover
Basal cells
Stem cells
Teeth
Odontoblasts
Tall columnar secretory cells
Near pulp cavity
Produce dentine
Laid down then calcified
90% type 1 collagen
70% wet weight hydroxyapatite
Ameloblasts
Produce enamel
Hydroxyapatite primary mineral
No collagen
96% mineralised
Tall columnar secretory cells
Ectodermal origin near surface of tooth
Die when tooth erupts
Salivary glands
3 major pairs of salivary glands
Parotid
Inside of cheeks
Acini
Pure serous gland
Only serous cells (protein secreting)
Produce amylase
Stored apical in acidophilic secretory granules (amylase)
Granules also contain
Peroxidase
Lysozyme
Cystatins
Ducts
Secretory acini
Intercalated ducts
Intralobular/striated ducts
Major ducts
Parotid gland has longest intercalated ducts
Myoepithelial cells around acini
Submandibular
Floor of mouth
Acini
Mixed gland
Mostly pure serous acini
Serous cells filled with prominent, purplish-staining zymogen granules
Mucous cells (mucin-secreting)
Pale staining with abundant clear cytoplasm
Arranged in duct-like structures, capped by serous demilumes
Ducts
Intercalated ducts are short
Striated ducts are long and clearly evident
Sublingual
Under tongue
Acini
Mixed gland
Consists mostly of mucous acini capped with serous demilumes
Far less protein-secreting cells
Ducts
Short intercalated + striated ducts short in number
Long excretory ducts
multiple secretory ducts empty directly into floor of oral cavity near to submandibular ducts
Many minor glands
Oesophagus
Structure
~25cm long muscular tube
Connects pharynx to stomach
Lumen normally collapsed with longitudinal folds
Function
Conduit (channel) for bolus of food from mouth
Mucosa
Epithelium
Stratified squamous non keratinised
Protects from injury
Mechanical
Chemical
Lamino propria
Connective tissue containing diffuse lymphatic tissue + lymphatic nodules
Oesophageal cardiac glands
Present mainly in terminal part of oesophagus
Produces neutral mucus which protects from regurgitated gastric contents
Muscularis mucosae
Single layer of longitudinal muscle
Submucosa
Dense irregular connective tissue
Large blood + lymphatic vessels
Submucosal plexus (Meissner's plexus)
Network of intersecting nerves
Stomach
Fundic region
Chief cells
Stain purple
Lots of RER to produce pepsinogen
Basophilic due to RER
Parietal (oxyntic) cells
Stain pink (H&E)
Eosinophilic due to lots of mitochondria
Lots of mitochondria for production of HCl
Enteroendocrine cells
Unstained in H&E
Stained best by silver staining due to natural aldehydes
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