Histology Flashcards
Which parts of the oral cavity are covered by keratinised
stratified squamous epithilium?
Hard palate
Gingiva
The rest is non keratinised squamous epithilium
What type of epithilium covers the nasal cavity and nasopharynx?
Respiratory epithilium
What type of epithilium cover the anterior 2/3rds of the tongue (horizontal part)
Stratified squamous epithilium which is thin on the ventral surface but thick with papillae of the dorsal surface
What type of epithilium covers the posterior 1/3rd of the tongue (descending part)?
Smooth stratified squamous epithilium which except for the circumvallate papillae, lacks papillae but does hace substantial lymphoid aggregates in the submucosa
What are circumvallate papillae?
Papillae found just posterior to the sulcus terminalis and contain tastebuds which detect bitter tasting foods
What are the 4 types of papillae and which do not have tastebuds?
Fungiform
Foliate
Filiform (no tastebuds)
Circumvallate
Where are foliate papillae found?
Lateral aspects of the dorsal surface of the tongue
Where are fungiform papillae found?
Middle of the tongue
Where are filiform papillae found?
Across the whole dorsal surface of the tongue
Does the descending tongue have crypts?
Yes- often surrounded by lymphoid tissue with some lymphiod follicles
What are the 4 layers of the digestive tract form the oesophagus to the anal canal?
1) Mucosa
2) Submucosa- lose connective tissue
3) Muscularis externa
4) Serosa or Adventicia
What is within the mucosa?
1) Epithilium which sits on a basal lamina
2) Lamina propria which is loose connective tissue
3) Muscularis mucosae which is a thin layer of smooth muscle
What is within the submucosa?
Loose connective tissue
What is within the muscularis externa?
Two thick layers of smooth muscle, an inner circular layer and an outer longitudinal layer
What is within the adventicia?
Outer layer of connective tissue which either suspends the digestive tract or attaches to other organs
Where are submucosal glands found?
Within the oesophagus
What is the function of oesophageal submucosal glands?
To secrete mucin which protects the oesophageal wall from damage especially from acid
What type of epithilium lines the oesophagus?
Stratified squamous epithilium
What type of epithilium line the cardia of the stomch?
Columnar epithilium
What is the name of the point where the epithilium changes from stratified squamous in the oesophagus to columnar in the stomch?
Gastro-oesophageal junction
There are holes found in the stomach wall within the mucosa. What are the holes called and what is found within them?
Gastric pits and at the bottom ar between 1 and 7 gastric glands
Gastric pits are lined with epithilial cells. True or flase?
True
What are the 3 parts of the gastric gland?
Isthmus, neck and base
The cells of the gastric glands are not evenly distributed. Which cells are found where (parietal, mucus, stem, chief and neuroendocrine cells)?
Isthmus = parietal cells (Release HCl, intrinsic factor and gastroferrin) Neck = mostly mucus and stem cells Base = Chief cells (pepsinogen) and neuroendocrine cells
What do chief cells produce and what characterises them?
Pepsinogen. Have Zymogen granules which cantain the enzyme.Appear darker. Lots of RER ad ACh receptors
What do parietal cells secrete and what are tehre characteristics?
Hydrochloric acid.
ACh, Histamine and Gastrin receptor on the basal surface and secretort canaliculus
What are the 4 regions of the stomch and how is the mucosa different in each part?
Cardia: Deep gastric pits that branch into loosely packed tortuous glands
Fundus:
Body: Shallow gastric pits with long straight gastric glands
Pylorus: deep gastric pits with branched, coilded gastric glands at a higher density than the cardia
What is unique about the muscularis externa of the stomach?
It contains an additional oblique layer of muscle which is located internal to the circular layer. It aids the churning action of the stomch
What happens at the gastroduodenal junction?
Mucosa changes
The inner circular layer f smooth muscle is markedly thickened to form the pyloric sphincter
What characteries the mucosa of the small intestine?
Villi and crypts of Lieberkuhn
What is a unique histological feature of the duodenum?
Contains Brunners glands in the submucosa which are stimulated by the presence of chyme
What is the function of Brunners glands?
empty into the intestinal glands, secrete an alkaline fluid composed of mucin, which exerts a physiologic anti-acid function by coating the duodenal epithelium, therefore protecting it from the acid chyme of the stomach.
What is the unique histological feature of the jejunum?
Tallest Villi, located on permanent circular folds of the mucosa and submucosa, the plicae circularis
What is the unique histological feature of the ileum?
Aggregations of lymphiod follicles- Peyers patches found in the submucosa and extending into the lamina propria
What are the features of enterocytes?
Most numerous cell of the small intestine. Columnar cells with a brush boarder and are the principle absorptive cell
What are the features of goblet cells?
Produce mucin to protect the epithilium and lubricate the passage of material
What are the features of Paneth cells found in the small intestine?
Found at the base of crypts of Lieberkuhn, they have a defensive function and a role in regulating bacterial flora (secrete lysosomes and defensins)
What are the features of neuroendocrine cells in the small intestine?
Produce hormones that contribute to the control of secretion and motility eg gastrin CCK, vasoactive intestinal peptide VIP
What is the function of stem cells found in the small intestine?
Found at the base of crypts of Lieberkuhn and divide to replenish epithilium
Plicae circularis contain mucosa and submucosa. T or F?
True and are found in the jejunum
What does GALT stand for?
Gut associaed lymphoid tissue
What are the 2 main types of cells in the large intestine?
Absorptive cells for removal of salt and water
Goblet cells or the secretion of mucus to lubricate the colon
Does the large intestine contain crypts?
Yes but no villi
What are crypts?
Straight tubular glands which extend down to the muscularis mucosae
How is the longitudinal muscle arranged in large intestine?
Not continuous but is found in 3 muscular strips called teniae coli
What is the appendix?
Blind ending hollow extension of the cecum
How is the structure of the appendix different to the structure of the colon?
Far fewer crypts and there is typically a circular arragement of lymphoid tissue in the submucosa and the lamina propria.
Lymphoid tissue declines with age
What happens at the rectoanal junction?
Rectal mucosa is columnar and the epithelium of the anal canal is stratified squamous epithelium which continues with the stratified squamous epithelium of the surrounding skin
How long is the anal canal?
2-3cm
Where are the ganglia of the ENS found?
Between the two muscle layers that make up the muscularis externa
The ENS controls gut motility. What is the plexus called that does this?
Myenteric plexus- found in the muscularis extena
There is another network of neurons found in the submucosa. WHat is this called and what does it do?
Submucosal plexus
Controls the muscles of the muscularis mucosae and regulates secretion into the epithilium
