Oral Histology Flashcards
What are the 5 general layers of the GI tube?
1) Mucosa 2) Submucosa (CT) 3) Inner circular muscle 4) Outer longitudinal muscle 5) Serosa (squamous epithelium)
What are the 3 general layers of the GI mucosa?
1) Epithelium 2) Lamina propria (CT) 3) Muscularis mucosa
In what regions of the GI tract do you not have serosa?
Adventitia, this is where the GI tube is connected to the retroperitoneum.
In what region of the GI tract was the section shown below taken from?
The gastroesophageal junction. Note the stratified squamous epithelium in the esophagus sharply demarcated from the non-ciliated columnar epithelium with goblet cells.
Where in the GI tube do you find stratified squamous epithelium?
Esophagus and colon
Where in the body was this section taken from?
Small intestine. Note the tall columnar cells with goblet cells.
Why is epithelial differentiation so variable in the GI tract?
Stem cells located in the crypts of the intestine and stomach can migrate and differentiate into any type of cell (villi or secretory cells).
What cells are indicated below?
Top: mitotic cell in intestine, probably from a stem cell in an intestinal crypt. Bottom: enteroendocrine secretory cell (secretory)
What cells secrete hormones in the GI tract that initiate different responses related to digestion?
Enteroendocrine cells: change in luminal content causes secretion of different hormones (gastrin activates parietal cells, secretin acts on pancreatic duct cells)
Where are hormone granules secreted from this enteroendocrine cell?
The basal aspect. Note how the secretory granules are near the connective tissue where they can reach muscle, epithelium and blood vessels.
What cells in the GI tube are involved in host defense? Where do they secrete their content?
Paneth cells. They secrete into the GI tube lumen where pathogens exist.
Locations of GI sphincters?
Esophagus (upper and lower), pyloric, ileocecal and anal (external & internal)
How is innervation of the GI tract distributed?
The parasympathetic and sympathetic nervous systems have input into the enteric nervous system (myenteric plexus and submucosal plexus)…except for sympathetic modulation of blood vessels. The enteric nervous system modulates smooth muscle, secretory cells and endocrine cells.
Why is the enteric nervous system sometimes called “the little brain”?
Roughly 100 million neurons run through it with a very wide range of neurotransmitters.
Where are the neurons of the myenteric nervous system located?
Between the inner circular muscle layer and the outer longitudinal muscle layer.
Identify the different structures indicated below?
This is a section of a lip: 1) Keratinized stratified squamous epithelium (hair follicles & glands) 2) Vermillion border 3) Non-keratinized stratified squamous epithelium (w/ exocrine glands) 4) Striated skeletal muscle.
What are the three layers of the mucosa of the lip?
1) Non-keratinized epithelium 2) Lamina propria 3) Mucosal and salivary glands
Which cells stain darker mucosal glands or serous glands?
Serous, they secrete material that is not as glycosylated as mucosal secretions, which causes mucosal glands to stain lighter.
Identify where teeth are forming in the image below.
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Where do the cells come from that form teeth?
The epithelial layer (ameloblasts) invaginates in the oral cavity and forms enamel. Mesenchymal cells (odontoblasts) differentiate to form the inner layer of the tooth (dentin).
Why do you need to see a dentist when you get a cavity?
When the tooth erupts, you no longer have epithelial layers making enamel.
What structure is indicated below?
Gums. Note the thick invaginating epithelium designed to withstand abrasion from consuming food.
How is the tooth attached to the bone?
Periodontal ligament. Note that this ligament is flexible and is why braces work.
What are the rough projections on the tongue?
Papillae: 1) Fungiform (taste) 2) Filiform (pointy, for grabbing food) 3) Circumvallate (taste) 4) Foliate (folds on side of tongue)
Where are the taste buds located in the tongue?
Within the “moat”, note the von Ebner glands that secrete serous substance
What is the function of the cell indicated below?
It is the sensory cell of the taste bud surrounded by the elongated sustentacular cells. It sends taste sensation through connected cranial nerves.
How do we differentiate between bitter, sweet, umami, sour and salty?
Bitter, sweet, umami all have ligand-receptor signaling. Sour and salt have channel signaling.
Where is the section seen below taken from?
Note the presence of lymphoid tissue and mucous/serous glands. This is from a tonsil.
How does saliva get from the secretory cell into the larger secretory duct of the submandibular gland?
Secretory cell -> Acini -> Intercalated duct -> Striated duct (note striated mitochondrial arrangement)
What happens to Na recovery from saliva as you increase saliva secretion? What other ions are exchanged in the ductule cells of salivary glands?
It goes down. Ductule cells also recover Cl-, H+ and K+
What are the different phases of saliva release?
Cepalic (thinking about food), gastric (eating food), intestinal (digesting food) phases. The parasympathetic nervous system increases flow and the sympathetic system decreases flow.
Which picture shown below is from the parotid gland, sublingual and submandibular gland?
Top: submandibular, note the even mix of mucous and serous acini. Middle: parotid: note the predominance of serous acini and fat cells. Bottom: sublingual: note the predominance of mucous acini.
