Histology of GI Tract Flashcards
What structures are shown by the stars in the image?
What are the different types of liver lobules?
What does each type emphasize based on its structure?
Label image.
Where in GI tract is it from?
Label image. Where in small intestine is section from?
Label image. Where in small intestine is section from?
Where is the GALT found?
Ileum + colon
Which salivary gland is this section from?
True or false: # goblet cells decreases from duodenum of ileum.
False –> increases
Which salivary gland is this section from?
Where can you find stem cells in the small intestine?
Crypts
Why aren’t microvilli present in the entire GI tract?
They are only present in the parts of the GI tract that do not come in contact with solid materials, i.e. only when the contents of the tract have become liquified
Label image.
Where is this image from in the body?
What type of salivary duct is this?
What is this ducts function?
What type of salivary duct is this?
What is this ducts function?
Label image.
Where is this image from in the body?
Enterocytes that line the villi of small intestine are […]
Enterocytes that line the crypts of small intestine are […]
Absorptive
Secretory
Label image
Where is section from?
Liver
Label image.
Where is image from in body?
What is an ito cell?
How are salivary glands classified?
Based on the amount of mucus vs. serous glands they contain.
What is this image showing?
Kupfer cells = resident macrophages in liver
Which salivary gland is this section from?
What kind of epithelium lines the esophagus?
Non-keratinized epithelium
What surrounds salivary acini?
Myoepithelial cells –> prevent the acini from expanding during secretion thus forcing fluid out ducts
Label image.
Where in GI tract is section from?
How can the muscularis externa layer of the esophagus tell you where you are in the esopagus?
From internal to external, what is the order of structures in a salivary duct?
Acinus –> intercalated duct –> striated duct –> excretory duct
In a liver acinus lobule, what is the significance of zones 1 and 3 (shown below)?
Zone 1 sees blood first –> most susceptible to damage from toxins
Zone 3 sees blood last –> most susceptible to hypoxic damage
Label this image. Also, for each bold arrow, describe the type of secreting glands that are found in these locations.
What type of salivary duct is this?
What is this ducts function?
The submucosa is composed of […] tissue
Dense, irregular CT
What is the general purpose of the intercalated and striated ducts?
Initial saliva is similar in composition to ECF. These ducts modify the composition by transporting ions in/out of saliva to change final salivary composition.
Label image.
Where in GI tract is section from?
- Label image. Where in small intestine is section from?
- What is an M-cell?
- From Jejunum and ileum
- Image is showing a peyer’s patch, which is part of the GALT.
- See image for M cell
Label image.
Also:
- How does type of mucus change based on where mucus cell is in this section?
- What are the eosinophillic cells?
- What are the basophillic cells?
- Mucus near lumen = thick, protect lining from acid; mucus inside lining = thin/watery
- Eosinophillic = parietal cells
- Basophillic = chief cells
Label image. Where in large intestine is section from?
Where are the nervous plexi located in the GI tract?
They both span the entire length of the GI tract
Submucosal plexus is at border of submucosa and muscularis layer.
Myenteric plexus is in between inner circular layer of smooth muscle and outer longitudinal layer of smooth muscle.
Label this image.
What do lacteals in microvilli do?
Absorb fat/lipids and remove lymph
The epithelium of the gut sits on top of […]
Loose connective tissue
*In this case, called the lamina propria
ALL EPITHELIUM SIT ATOP LOOSE CONNECTIVE TISSUE
Label image. Where in GI tract is image from?
Esophagus
What is unique about the histology of the gallbladder compared to rest of GI tract?
No submucosa
Label image.
Label image.
Where in GI tract is section from?
How do you distinguish between parotid, submandibular and sublingual salivary glands?
What is the difference between the adventitia and serosa in this image?
Serosa - if the section of gut is free and not connected to any other structure (see image)
Adventitia - if the section of gut is connected to other tissue (see image, side of gut tube that is connected to mysentery is adventitia)
Label this image. Where in small intestines is section from?
C - sublingual gland
D – myoepithelial cell – prevents expansion of acinar cells during excretion, forcing fluid out the ducts
A – 2 (striated duct)
B – 3 (excretory duct)
C – 1 (intercalated duct)
The ductal system is responsible for modifying the composition of saliva, which is initially similar in composition to extracellular fluid.
Identify the 4 layers of the esophageal wall
Mucosa: yellow
- Epithelium
- Lamina propria
- Muscularis mucosa
Submucosa: blue
Muscularis external red
- Outer longitudinal
- Inner circular
Adventia/serosa: green
A – this is the middle third of the esophagus.
- Esophagus
- Mucus
- Lubrication of the epithelial lining to allow for passage through the lumen
A – this is the lower third of the esophagus.
Note the two layers of smooth muscle, arranged as a longitudinal and circular layer
The gastroesophageal junction, or squamocolumnar junction
Identify the following cells: surface mucous cell, parietal cell, mucous neck cell, chief cell
surface mucous cell: yellow
parietal cell: green
mucous neck cell: blue
chief cell: red
A.Mucous neck cell – secrete a thin, watery mucus that is low in bicarbonate in response to vagal nerve stimulation
- Helps suspend pepsin + mix with chyme
B.Surface mucous cell – constitutively secrete a thick, bicarb-rich mucus
- Protective function
B – these are pepsinogen-secreting chief cells. Discuss the conversion of pepsinogen to pepsin by the acidic environment of the stomach.
HCl helps denature proteins directly, also activates pepsinogen to pepsin, which is a protease that digests proteins. Intrinsic factor serves as a critical molecule for absorption of vitamin B12 in the ileum
B – enteroendocrine cells of the stomach do not secrete leptin.
Functions:
- Ghrelin stimulates GH secretion appetite. Inhibits lipid metabolism.
- Leptin functions as a satiety signal
- Somatostatin inhibits gastrin release and HCl secretion, as well as most other GI hormones
- Gastrin stimulates HCl secretion.
- Histamine stimulates HCl secretion
C – these are central lacteals found in the villi of the small intestine. Recall that fats are absorbed and enter the bloodstream via the lymphatic system
Identify this gland, and discuss the role of these glands
Brunner’s glands, secrete HCO3-, neutralize the stomach acid and protect the mucosa of the small intestine.
E – Meissner’s plexus (Submucosal) responsible for enterocyte function
B – Auerbach’s plexus (Myenteric) responsible for GI motility
Identify this structure and discuss its function.
Lymphatic nodules. Epithelial cells covering are microfold cells, or M cells. These are Ag-sampling cells that transport antigens from the lumen of the intestine to immune cells, thereby playing a role in initiating an immune response.
B. Paneth cells secrete alpha defensin and lysozyme. These antibacterial compounds help maintain the gut flora.
C. Muscularis externa – the outer longitudinal layer of the ME is thin, with thickened bands running the length of the colon. These thickened bands make up the TC.
