Histology Flashcards
What lines the oral cavity, oropharynx and laryngopharynx?
Squamous epithelium
Generally non-keratinised
What lines the nasal cavity and nasopharynx?
Respiratory epithelium
What is the histology of the anterior 2/3 of the tongue?
Stratified squamous epithelium
Thin on ventral surface
Thick and with papillae on the dorsal surface
What is the histology of the posterior 1/3 of the tongue?
Smooth stratified squamous epithelium
Lacks papillae (except for circumvallate)
Substantial lymphoid aggregates in the submucosa
What are the four types of papillae which line the tongue?
Fungiform
Circumvallate
Foliate
Filiform (no tastebuds)
What are the four major layers of the digestive tract (lumen outwards)?
Mucosa (Epithelium, Lamina propria, muscularis mucosae)
Submucosa
Muscularis externa (inner circular, outer longitudinal)
Serosa or Adventitia
What occurs at the gastro-oesophageal junction?
Abrupt transition from stratified squamous epithelium of oesophagus to columnar epithelium of stomach
What is the surface view of the stomach?
Relatively flat with holes (gastric pits)
Gastric glands at the bottom of the pits
What lines the gastric pits of the stomach?
Surface mucous cells
How are the cells in the gastric gland distributed?
Isthmus = Mostly parietal cells Neck = Mostly neck mucous cells and stem cells Base = Mostly chief cells, with a few parietal cells and neuroendocrine cells
What is the role of the chief cells of the gastric glands?
Digestive enzyme secretion
What is the role of the parietal cells of the gastric glands?
Hydrochloric acid production
What is the mucosa of the cardia of the stomach like?
Deep gastric pits that branch into loosely packed, tortuous glands
What is the mucosa of the body of the stomach like?
Shallow gastric pits with long straight gastric glands
What is the mucosa of the pylorus of the stomach like?
Deep gastric pits with branched, coiled gastric glands at a higher density than in the cardia
What is unusual about the muscular external of the stomach?
It contains an additional layer oblique to the circular and longitudinal muscle layers
Located internal to the circular layer
Aids the churning action of the stomach
What occurs at the gastro-duodenal junction?
Abrupt transition from stomach mucosa to duodenal mucosa
Inner circular layer of smooth muscle thickens to form the pyloric sphincter
What is the surface view of the small intestine?
Villi, with pits in between (Crypts of Lieberkhun)
What is the histology of the duodenum?
Contains Brunner’s glands in the submucosa
These produce alkaline mucous to neutralise chyme from the stomach
What is the histology of the jejunum?
Tallest villi, locate don circular folds of mucosa and submucosa (plicae circularis)
What is the histology of the ileum?
Aggregations of lymphoid follicles called Peyer’s patches found in submucosa, often extending into the lamina propria
What are the cells of the small intestine epithelium?
Enterocytes Goblet cells Paneth cells Neuroendocrine cells Stem cells
What are enterocytes?
Most numerous cells in SI epithelium
Tall columnar cells with brush border
Principle absorptive cells
What are goblet cells?
Produce mucin to protect epithelium and lubricate passage of material
What are Paneth cells?
Found at the base of the Crypts of Lieberkuhn
Defensive function
Regulate bacterial flora by secreting lysozyme and definsins
What are neuroendocrine cells?
Produce hormones that contribute to control of secretion and motility (e.g. gastrin, CCK, VIP)
What are stem cells?
Found at the base of the Crypts of Lieberkuhn
Divide to replenish epithelium
What are the two principal cells of the large intestinal epithelium, and what are their functions?
Absorptive cells = Removal of salts and thereby water Goblet cells = Secretion of mucus to lubricate the colon
How are the cells of the large intestinal epithelium arranged?
Straight, tubular glands (crypts) which extend down into the muscular mucosae
What is distinctive about the longitudinal muscle layer in the large intestine?
Not continous
Made of 3 muscular strips (teniae coli)
What the histology of the appendix?
Similar to the colon
Less abundant crypts
Circular arrangement of lymphoid tissue in the submucosa and lamina propria
Lymphiod tissue declines with age
What occurs at the recto-anal junction?
Change from rectal mucosa to stratified squamous epithelium of the anal canal
Where ar most of the neurones of the myenteric plexus found?
Between the two muscle layers of the muscularis externa
What is the submucosal plexus?
Controls muscle of the muscularis mucosae ad helps regulate secretion in the epithelium
Where is the sub mucous plexus found?
Submucosa
What is the myenteric plexus?
Interconnected network of fibres that control gut motility
