histology Flashcards
what kind of epithelium covers the; oral cavity, oropharynx and laryngopharynx?
stratified squamous epithelium which is not generally keratinised
what covers the nasal and nasopharynx ?
covered by the respiratory epithelium
tongue - what covers the anterior 2/3
statified squamous epithelium, thin on ventral surface, thick with papillae on the dorsal surface
tongue - what covers the posterior 1/3
smooth stratified squamous epithelium which for the most part lacks papillae but does have substantial lymphoid aggregates in the submucosa
tongue - papillae (the different types)
fungiform
foliate
circumvallate
filiform (this one doesn’t have tastebuds)
**need to know what they look like
what does the pharynx consist of
a ring of lymphoid tissue composed of the palatine tonsils, lingual tonsils, tubal tonsils and pharyngeal tonsils (adenoids)
**what does it look like though?
what are the 4 major layers the digestive track is made out of?
- mucosa
- submucosa
- muscularis externa
- serosa or adventitia
**what do they look like in comparison to each other?
mucosa
-is made up of 3 parts
>epithelium which sits on a basal lamina
>lamina propia which is loose connective tissue
>muscularis mucosae which is a thin layer of smooth muscle
submucosa
dense irregular connective tissue
muscularis externa
thin layer of smooth muscle
serosa/adventitia
outer layer of connective tissue that either suspends the digestive tract or attaches it to other organs
variations in the GI tract mucosa
bar = mucosal layer
what is the gastro-oesophageal junction
abrupt transition from stratified squamous epithelium of oesophagus to the simple columnar epithelium of the cardia of the stomach
what are gastric pits
holes in the stomach epithelium and gastric glands reside at the bottom of them
>they are lined by surface mucous cells
cells of the stomach epithelium
the cells of the gastric gland are not evenly distributed
>the isthmus has mostly parietal cells and stem cells
>the fundus is mostly chief cells with a few parietal cells and enteroendocrine cells (neuroendocrine cells)
chief cell
a digestive enzyme secreting cell
cells of the stomach epithelium
the cells of the gastric gland are not evenly distributed
>the isthmus has mostly parietal cells and stem cells
>the neck is mostly parietal cells and mucous cells
>the fundus is mostly chief cells with a few parietal cells and enteroendocrine cells (neuroendocrine cells)
the stomach regions
cardia
body
pylorus
cardia (mucosa)
deep gastric pits that branch into loosely packed, tortuous glands
body/fundus (mucosa)
shallow gastric pits with long straight gastric glands
pylorus (mucosa)
deep gastric pits with branched, coiled gastric glands at a higher density than in the cardia
muscularis externa of the stomach
is unusual in that in areas it contains an additional layer
>this layer is oblique to the usual circulation and longitudinal muscle layers and is located internal to the circular layer
>this aids churning
gastroduodenal junction
an abrupt transitions from stomach mucosa to duodenal mucosa
>the inner circular layer of smooth muscle is markedly thickened to from the pyloric sphincter PS
what are the finger like projections and what resides at the bottom of them
> villi
>crypts of Lieberkuhn
small intestine segments
duodenum
jejunum
ileum
duodenum
contains Brunner’s glands in the submucosa
jejunum
tallest villi, located on permanent circular folds of the mucosa and submucosa, the place circulars. Lymphoid follicles infrequent
ileum
characterised by shorted villi and aggregations of lymphoid follicle called Peyer’s patches found in the submucosa and often extending into the lamina propria
the cells of the small intestine epithelium
enterocytes goblet cells paneth cells enteroendocrine cells stem cells
enterocytes
the most numerous cells, they are tall columnar cells with a brush border and are the principle absorptive cell
goblet cells
produce mucin to protect epithelium and lubricate passage of material
paneth cells
found at the base of the crypts of Lieberkuhn
they have a defensive function and have a role in regulating bacterial flora - they secrete lysozyme and definsins
enteroendocrine cells
produce hormones that contribute to the control of secretion and motility ie gastrin, cholecystokinin CCK, and vasoactive intestinal peptide VIP
stem cells
found at the base of the crypts of Lieberkuhn
they divide to replenish epithelium
duodenum
receives the acidic, partly digested semifluid material called chyme form the stomach
>it has glands located in the submucosa - Brunner’s glands and when stimulated by the presence of chyme they produce a thin, alkaline mucous to neutralise the chyme
Brunner’s gland
what does it look like ?
Jejunum cross section
- the plicae are not just folds of the mucosa but also they contain submucosa
Ileum
there is a substantial amount of lymphoid tissue associated with the gut
>much of this consists of scattered lymphocytes but areas of excessively large aggregations of lymphoid tissue exist, particularly in the ileum
Peyer’s patches
Peyer’s patches
lymphoid tissue aggregations in the ileum
what is the general structure of the large intestine
look it up !
cells of the large intestinal epithelium
absorptive cells
goblets cells
**these are arranged in straight, tubular glands, referred to as crypto’s that extend down to the muscularis mucosae
absorptive cells
for removal of salts and thereby water
goblet cells
for the secretion of mucous to lubricate the colon
the large intestine
**the outer, longitudinal smooth muscle is distinct
>is not continuous but found in three muscular strips called the teniae coli
what is the appendix
> blind-ending hollow extension of the cecum
the structure is similar to the rest of the colon but the crypts are far less abundant and there is typically a circular arrangement of lymphoid tissue in the submucosa and often in the lamina propria
the lymphoid tissue tends to decline with age
rectoanal junction
> there is a distinction junction between the mucosa of the rectum and the non-keratinised stratified squamous epithelium of the anal canal
the long anal canal is continuous with the keratinised stratified squamous epithelium of the surrounding skin
ENS
> receives input from the autonomic nervous system but is capable of coordinating gut motility locally
the interconnected network of fibres has two plexuses one in the submucosa and one between the muscle layers of the muscularis externa (myenteric)
ENS
> receives input from the autonomic nervous system but is capable of coordinating gut motility locally
the interconnected network of fibres has two plexuses one in the submucosa and one between the muscle layers of the muscularis externa (myenteric)
**has the same number of neurons as the spinal cord
myenteric plexus
an interconnected network that controls gut motility
ganglion
a group of neurones living outside of the brain and spinal cord
submucosal plexus
the second network of neurons found in the submucosa that controls the muscle of the muscularis mucosae and also helps regulate secretion in the epithelium
different types of mucosa in the digestive tract
protective
secretory
absorptive
protective
protective mucosa
non-keratinised stratified squamous epithelium ie oral cavity, pharynx, oesophagus and anal canal
secretory
simple columnar epithelium with extensive tubular glands ie stomach
absorptive
simple columnar epithelium with villi and tubular glands ie small intestine
protective and absorptive
simple columnar epithelium with tubular glands ie large intestine
