Histology Flashcards
What type of epithelium is the oral cavity, oropharynx and laryngopharynx covered by
Generally non-keratinised (Except hard palate and gingiva) stratified squamous epithelium
What type of epithelium is the nasal cavity and nasopharynx covered by?
Respiratory epithelium
What type of epithelium covers the anterior 2/3rds of the tongue
How does this vary between the ventral and dorsal surface
Stratified squamous epithelium
Thin on ventral surface
Thick with papillae on the dorsal surface
Epithelium on the posterior 1/3rd of the tongue
Smooth stratified squamous epithelium which lacks papillae, except the circumvallate papillae, but does have some lymphoid follicles in the submucosa
What are the 4 types of taste buds present on the tongue?
Fungiform
Cicumvallate
Foliate
Filiform (no tastebuds - occupy much of the dorsal surface of the tongue)
What are the 4 major layers of the digestive tract (from the oesophagus to the anal canal)
Mucosa (epithelium, lamina propria, muscularis mucosae)
Submucosa
Muscularis externa
Serosa or adventitia
What are the 3 layers of the mucosa?
Epithelium (sits on a basal lamina) Lamina propria (loose connective tissue) Muscularis mucosae (thin layer of smooth muscle)
What is the submucosa
Loose connective tissue
What is the muscularis externa
2 thick layers of smooth muscle, an inner circular layer and an outer longitudinal layer)
What is the serosa or adventitia
An outer layer of connective tissue that ether suspends the digestive tract or attaches it to other organs
What happens in terms of the epithelium at the cardia of the stomach
There is an abrupt transition from stratified squamous epithelium of the oesophagus t to simple columnar epithelium of the stomach
What are the holes in the surface of the stomach and what is at the bottom of these
Holes = gastric pits
There are 1-7 gastric glands at the bottom of these
What are gastric pits lined by
Surface mucous cells
In terms of the cells gastric gland, what does the pit contain mostly?
Isthmus?
Neck?
Base?
Pit = surface mucous cells Isthmus = parietal cells neck = neck mucous cells and stem cells Base = chief cells (few parietal cells and neuroendocrine cells)
What are chief cells of gastric glands?
digestive enzyme secreting cells
What are parietal cells of gastric glands
HCl acid producing cells
How does the mucosa of the stomach differ across the cardia, body and pylorus?
The cardia contains deep gastric pits that branch into loosely packed, tortuous glands
The body contains shallow gastric pits with long straight gastric glands
The pylorus contains deep gastric pits with branched, coiled gastric glands at a higher density than in the cardia
What is unusual about the muscularis externa of the stomach?
It contains an additional oblique layer which located internal to the circular layer and aids in the churning action of the stomach
What creates the pyloric sphincter?
The inner circular layer of smooth muscle is markedly thickened
Epithelium of the small intestine
Simple columnar epithelium with villi and tubular glands
Epithelium of the large intestine
Simple columnar epithelium with tubular glands
What are the crypts called between the bases of adjacent villi in the small intestine?
Crypts of Lieberkuhn
What makes the duodenum different from any other region of the GI tract
It contains glands within the submucosa called Brunner’s glands which when stimulated by the presence of chyme, produce a thin, alkaline mucous to neutralise the chyme
What part of the small intestine has the tallest villi
The jejunum (located on the plicae circulars)
What are the permanent circular folds on the mucosa and submucosa of the small intestine (except the first part of the duodenum) called?
Plicae Circularis (these are not just folds of the mucosa, but also contain submucosa)
What are the cells of the small intestinal epithelium
Enterocytes Goblet cells Paneth cells Neuroendocrine cells Stem cells
What are enterocytes
Most numerous cell in small intestinal epithelium
Tall columnar cells with a brush border
Principle absorptive cell
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 and have a defensive function and role in regulating bacterial flora (secrete lysozyme and definsins)
What do neuroendocrine cells produce?
Hormones that contribute to the control of secretion and motility e.g. CCK, gastrin, VIP
Purpose of stem cells in small intestinal epithelium
Found at the base of the crypts of Lieberkuhn
Divide to replenish the epithelium
What does GALT stand for?
Gut associated lymphoid tissue - the gut has a substantial amount of lymphoid tissue associated with it
What are Peyer’s patches
Areas of relatively large aggregations of lymphoid tissue, particularly in the ileum
What are the 2 principal cell types present in the epithelium of the large intestine
Absorptive cells - for removal of salts and thereby water
Goblet cells - for the secretion of mucus to lubricate the colon (these are arranged in straight tubular glands referred to as crypts that extend down to the muscularis mucosae
What is different about the outer, longitudinal smooth muscle in the large intestine
Is not continuous but instead found in 3 muscular strips called teniae coli
What is different about the structure of the appendix compared to the rest of the colon
The crypts are far less abundant
There is typically a circular arrangement of lymphoid tissue in the submucosa and often the lamina propria (the lymphoid tissue tends to decline with age)
What type of epithelium does the anal canal have
Stratified squamous epithelium
Where do most of the neurones of the enteric nervous system live?
What is this interconnected of fibres called?
What does it control?
In groups called ganglia between the 2 muscle layers that make the muscularis externa
Myenteric plexus
Gut motility
Apart from the myenteric plexus, what other network of enteric neurones exist?
Where is this found?
What does it control?
Submucosal plexus
Submucosa
Controls the muscle of the muscularis mucosae and also helps regulate secretion in the epithelium
