GI - Histology - Upper & Lower Tracts Flashcards by Jason Worley

What type(s) of epithelia is(are) found in the oral cavity?

(1) Non-keratinized stratified squamous (lining mucosa)
(2) Keratinized or para-keratinized stratified squamous (lining gingiva and hard palate)
(3) Specialized papillae and taste buds (dorsal tongue)

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What are the three histological sections of the oral lip?

Describe each.

(1) Cutaneous, (2) vermillion/red, (3) oral mucosa

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What muscle group is found in the lips?

Orbicularis oris

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Name the histological lip region described: thin skin with tall dermal papillae (keratinized stratified squamous epithelium with hair follicles and sebaceous and sweat glands).

Cutaneous region

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Name the histological lip region described: a stratified squamous epithelium supported by connective tissue containing blood vessels responsible for the red color of this region; no salivary glands

Vermillion/red region

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Name the histological lip region described: stratified squamous epithelium, supported by a dense lamina propria and a submucosa, closely bound by connective tissue fibers to the underlying skeletal muscles.

Oral mucosa region

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Name and describe the papillae of the tongue.

Filiform (most numerous) - covered by keratinized stratified squamous epithelium

Fungiform - same covering as filiform, mushroom-shaped, taste buds

Circumvallate - ducts of glands of von Ebner, side taste buds

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Where are taste buds found in relation to the papillae of the tongue?

Within the circular cleft

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Gustatory cells contact masticated food through:

Taste pores

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What are the three types of cell in the tongue related to taste?

Gustatory

Supportive

Stem (basal)

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What three precusor cells give rise to the teeth?

Ameloblast (enamel)

Odontoblast (dentin)

Cementoblast (cementum)

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Name the respective product of each of the following cells:

Cementoblast

Ameloblast

Odontoblast

Cementum

Enamel

Dentin

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What is the hard, outer layer of the tooth?

What lies just deep to this layer?

Enamel;

dentin

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The _________ ligament secures the tooth to alveolar bone via the ligament’s interface with the tooth through ___________.

Periodontal;

cementum

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Name the layers of the esophagus from the inner mucosa to the outermost layer (assume above the diaphragm).

Mucosa

- Epithelium*
- Lamina propria*
- Muscularis mucosa*

Submucosa

- Glands, blood vessels*
- Meissner’s plexus*

Muscularis externa

- Inner circular layer*
- Auerbach’s plexus*
- Outer longitudinal layer*

Adventitia

Serosa (below diaphragm)

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What esophageal covering is only present below the diaphragm?

Serosa

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True/False.

Contraction of the muscularis mucosae produces ___________ folds in the esophagus.

Longitudinal

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What type of epithelium lines the esophageal lumen in a healthy esophagus?

Non-keratinized stratified squamous epithelium

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The muscularis of the upper 1/3 of the esophagus is made of _________ muscle.

The muscularis of the upper 2/3 of the esophagus is made of _________ muscle.

The muscularis of the upper 3/3 of the esophagus is made of _________ muscle.

Striated;

striated + smooth;

smooth

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Describe the glands of the esophagus.

Tubuloacinar glands arranged in small lobules that drain into a single duct

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What type of gland is found in the esophageal mucosa?

What type of gland is found in the esophageal submucosa?

Cardiac mucus glands (lamina propria);

esophageal glands

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From proximal to distal, what are the four general regions of the stomach?

Cardia,

fundus,

body,

pyloric antrum

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The stomach lumen is lined by longitudinal folds called:

Rugae

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Describe the three regions of the general anatomy of a gastric gland.

The pit (surface mucous cells),

the neck (pinch point),

the body (parietal, chief, neuroendocrine, and stem cells)

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Describe the histology of a gastric gland.

Describe the histology and function of a gastric parietal cell.

Histology: microvillous, numerous cannaliculi and mitochondria Function: secrete **HCl and intrinsic factor**

Describe the histology and function of a gastric chief cell.

Histology: apical zymogen granules, basal RER, supranuclear Gogli Function: secrete **pepsinogen**

What are the four general layers found throughout the GI tract?

Mucosa, submucosa, muscularis externa, serosa

From anatomically largest to smallest, name four mechanisms by which the small intestine increases its surface area.

Plicae circularis Villi Crypts of Lieberkuhn Microvilli

Define: crypts of Lieberkuhn.

Invaginations of intestinal mucosa extending deep between villi ## Footnote *(at times, all the way down to the muscularis mucosae)*

Describe the gastric epithelium.

Simple columnar

What is the difference between gastric mucous cells found on the luminal epithelium and those found in the neck of gastric glands?

Surface - insoluble mucus production Glandular neck - soluble mucus production

What are some of the products secreted by enteroendocrine cells found in the body of gastric glands?

Cholecsytokinin, secretin, gastrin

**True/False**. Both the gastric epithelium and the small intestinal epithelium are simple columnar.

True.

What are the five main cells of the small intestine?

Enterocytes Goblet cells Enteroendocrine cells Paneth cells Stem cells

What main function(s) do Paneth cells of the small intestine serve?

Release lysozymes, defensins, phospholipase A2; regulate gut flora

What structure innervates/causes villous movement in the small intestine? Central lacteals are located in what tissue layer?

The submucosal (Meissner's) plexus; the lamina propria

**True/False**. Most small intestine lymphatics are in the lamina propria, and the central lacteals are located in the submucosa.

**False**. Most small intestine lymphatics are in the _submucosa_, and the central lacteals are located in the _lamina propria_.

What function(s) is(are) regulated by the submucosal (Meissner's) nerve plexus?

Mucosal / submucosal glands; the muscularis mucosa

What function(s) is(are) regulated by the myenteric (Auerbach's) nerve plexus?

Peristalsis

Describe the differences in villi shapes between the duodenum, jejunum, and ileum.

**D**: Leaf-like at apex **J**: finger-like **I**: shortest

Describe the differences in distinctive structures between the supportive networks of the duodenum, jejunum, and ileum.

**D**: Brunner's glands (submucosa) **J**: none **I**: Peyer's patches (lamina propria and submocusa)

What type of gland is found only in the duodenum?

Brunner's glands

What type structure is found only in the ileum?

Peyer's patches | (also, M cells)

What are M cells of the small intestine?

APCs of the ileal epithelium

Describe the relationship between M cells and Peyer's patches.

What type of epithelium is found in the large intestine?

Simple columnar

What are the four cell types of the large intestine?

Enterocytes Goblet cells Enteroendocrine cells Stem cells

What visible external structures are formed on the large intestine by the longitudinal layer of the muscularis externa?

The teniae coli

Identify which of the following are present in the large intestine: Plicae circularis Villi Microvilli Crypts of Lieberkuhn Goblet cells

Plicae circularis Villi **Crypts of Lieberkuhn** **Microvilli** **Goblet cells (in large number)**

Besides the colon (ascending, transverse, descending, and sigmoid), what are the other portions of the large intestine?

The appendix, the rectum, the anal canal

At the base of what distal structure of the large intestine do the teniae coli converge and end?

The appendix (note: they end at the base and do not extend onto the appendix)

Describe the lymphoid portion of the appendix.

Large aggregations in the lamina propria and submucosa

Describe the epithelium of the anal canal.

A transition from simple columnar to stratified squamous (with hair follicles and sebaceous glands)

Describe the general histological changes from the esophagus to the colon.

What form of vitamin D comes from the skin upon sun exposure?

D₃

How does parathyroid hormone have an effect on vitamin D protein production?

Upregulation of 1-α-hydroxylase in the PCT

After calcium absorption is increased by vitamin D, what protein modulates calcium channels and pumps to prevent cytosolic buildup of calcium within the enterocytes?

Calbindin

What are our main sources of 25-hydroxy vitamin D?

Sun exposure; diet

Vitamin D acts on what organ systems?

Bones; the gut

What protein is secreted in the oral cavity and is necessary for vitamin B12 absorption?

Transcobalamin-1 (haptocorrin) (R-factor)

What two substances must bind B12 in order for it to be properly carried to the absorption site? What substance is necessary to cleave one of these substances and allow the B12 complex to be absorbed?

Transcobalamin-1 (oral cavity), intrinsic factor (gastric body); pancreatic lipases (cleave TC-1)

Vitamin B12 absorption occurs at:

Peyer's patches (the terminal ileum)

**True/False**. B12 deficiencies virtually only occur when there is either an insufficient diet or gastric damage.

**False**. There are several other causes (see image).

What four layers are found throughout the digestive tract?

Mucosa Submucosa Muscularis externa Adventitia/Serosa

What are the three portions of the gut mucosa?

Epithelium, lamina propria, muscularis mucosa

**True/False**. Many small salivary glands and APCs can be found in the soft mucosa of the cheeks.

**False**. Many small salivary glands and APCs can be found in the soft _sub__mucosa_ of the cheeks.

In what directions do the intrinsic muscle fibers of the tongue project? Where do they attach?

In various crisscrossing directions; a central septum

Which type(s) of lingual papillae lack(s) taste buds?

Filiform

What type of lingual papilla is not abundant in adult humans?

Foliate

**True/False**. The lingual circumvallate papillae contain mucinous secretions.

**False**. The lingual circumvallate papillae contain _serous_ secretions.

What are the three largest salivary glands?

Parotid, sublingual, and submandibular

What are the four smaller salivary glands?

Lingual, labial, buccal, palatine

The ___________ gland has many bilateral ducts beneath the tongue. The ___________ gland has 1-2 ducts beneath the tongue.

Sublingual; submandibular

**True/False**. Salivary glands are often bunches of glands leading into a single duct.

True. (Similar to a bunch of grapes on a stalk)

Cells secreting serous fluids are \_\_\_\_\_\_\_ly colored. Cells secreting mucinous fluids are \_\_\_\_\_\_\_ly colored.

Dark; light

The parotid gland is a completely _________ (serous/mucinous) gland.

Serous

The submandibular gland is a predominantly _________ (serous/mucinous) gland.

Serous

The sublingual gland is a predominantly _________ (serous/mucinous) gland.

Mucinous

What term describes diminished salivary secretion?

Xerostomia

Describe the chemical/substrate makeup of saliva.

Water, calcium, phosphate, amylase (and other proteins), IgA, electrolytes

Mumps

The gastric cardia contains ________ glands. The gastric fundus contains ________ glands. The pyloric region contains ________ glands.

Cardiac; gastric; pyloric

What enzyme allows h. pylori to resist the acidic gastric pH?

Urease

What effect does acetylcholine (parasympathetic stimulation) have on gastric glands?

Increased parietal cell secretion (**HCl and intrinsic factor**); increased enteroendocrine secretion (**histamine and gastrin**)

Describe the differences in histological appearance between neck mucus cells, parietal cells, and chief cells.

Neck mucus cells - flat, pale, near gland neck; parietal cells - eosinophilic, round, cannalicular; chief cells - basophilic, round, towards deepest portion of gland

**True/False**. Enteroendocrine cells of the stomach can secrete a variety of hormones, including the following: *gastrin, histamine, glucagon, serotonin, somatostatin*

True.

What is the difference between a 'closed' and an 'open' enteroendocrine cell of the stomach?

Closed do not reach the gastric lumen (contacting the blood vessels only); open reach the lumen

What substance plays a major role in alkalizing gastric mucus?

Bicarbonate

Besides pepsinogen, what do gastric chief cells also produce?

Gastric lipase

How often do surface mucus cells of the stomach regenerate from stem cells?

Every 3 - 5 days

What segments of the GI tract contain paneth cells?

Mainly the jejunum

Describe the appearance of Paneth cells (found in the jejunum).

What type of cell is found only in the jejunum and helps regulate gut flora?

Paneth cells

**True/False**. If you see a section of small intestine with abundant lymphocytes, that must be the ileum.

False. Abundant GALT with germinal centers is more indicative of Peyer's patches.

Which section of the small intestine contains abundant submucosal glands? Which section of the small intestine contains abundant, very prominent GALT in the lamina propria? Which section of the small intestine has no submucosal glands or very prominent GALT?

Duodenum (Brunner's glands); ileum (Peyer's patches); jejunum

What types of cell are found in the colon?

Abundant goblet cells; colonocytes; some enteroendocrine; stem cells

What two locations in the gut have large, circular aggregations of GALT, often with germinal centers?

The ileum (Peyer's patches); the appendix

What type of epithelium covers the anal canal?

Keratinized stratified squamous epithelia

What section of the GI tract is this?

Jejunum

D. | (appendix)

While looking at a slide showing a section of the GI tract, you notice an abundance of lymphocytes. What section of the tract is this?

Inconclusive information given (80% of body lymphocytes are found in the GALT. More information needed.)

Which of the following does the large intestine not have: Villi Microvilli Crypts

Villi