GI-Histology - Intestines

Question 1

What are permanent folds of the mucosa and submucosa; most prominent in the proximal jejunum?

What are permanent folds of the mucosa?

Answer 1

Plicae circularis

Villi

Question 2

Describe:

Answer 2

Left: Plicae Circularis

Right: Villi on the plicae circularis

Question 3

In the small intestines, glands and crypts don’t expand deeper than muscularis mucosae except in the ?

Answer 3

duodenum

Question 4

What 4 major items extend into each villi on the plicae circularis?

Answer 4

arteries, veins, lacteals, muscularis mucosae (for tone)

Question 5

What are the 2 most common cells on the villi and along crypts in the small intestines?

Answer 5

1. Enterocytes — absorptive, columnar cells with microvilli (most common)
2. Goblet cells — mucous cells

Question 6

What cell secrets lysozyme and defensins; contribute to the innate immune system and are found in the fundus of crypts in the small intestines?

Answer 6

Paneth cells

Question 7

Where are the enteroendocrine cells located in the small intestine and what do they do?

Answer 7

Villi and crypts

paracrine/endocrine functions

Question 8

What cell type allows for transcellular passage of particles, microorganisms, to facilitate the exposure of antigens to the underlying lymphoid tissues and where would these cells be located?

Answer 8

M (microfold) cells

GALT, Peyer’s patches, lymphoid nodules

Question 9

Where are stem cells mostly located in the small intestine?

Answer 9

in the crypts

Question 10

What is pictured here?

Answer 10

Villi in small intestine (mostly lined by enterocytes and goblet cells)

Question 11

Describe the photos?

Answer 11

Enterocytes and Goblet cells along villi

enterocytes at the bottom

brush border

Question 12

Enterocytes and Lipid Processing

1. Lipids metabolized in the and diffuse across of the microvilli
2. Products move into smooth ER and resynthesized into
3. Triglycerides processed by Golgi and rough ER into
4. Chylomicrons released pass through the basement membrane and enter lacteal ducts

Answer 12

lumen, plasmalemma

triglycerides

chylomicrons

laterally

Question 13

What cell is located in the fundus of this crypt in this gland?

Answer 13

Question 14

Which enteroendocrine cell relies on outside info from other cells or blood and which can “taste” or sample lumen contents and respond accordingly?

Answer 14

Closed enteroendocrine cell

open enteroendocrine cell

Question 15

What type of malignancy would from from enteroendocrine cells?

Answer 15

carcinoid tumors

Question 16

Review diagram:

Answer 16

Question 17

Why do the M (Microfold) cells have small openings?

Answer 17

To bring in Antigens for the cell mediated immune system

Question 18

Take note of the primary and secondary lymphoid nodules in the Peyer’s patches. Which lymphoid nodule demonstrates an active immune response?

Answer 18

Question 19

What cell is being described?

Answer 19

Question 20

What cell is being described?

mucous cell

Answer 20

Question 21

What cell type is being described?

secrets isozymes and defensins; part of innate immune system

Answer 21

Question 22

What 3 cells are being described and what are their functions:

Answer 22

Question 23

What submucosal glands occur only in the proximal portion of the duodenum with secretory cells that are lightly-staining?

From these characteristic, what can you infer about its secretory product and function?

Answer 23

The secretory cells secrete an alkaline mucous that function to neutralize the acidic chyme passing into the duodenum from the pylorus (of the stomach)

Question 24

Which layer of intestine is pictured here?

Answer 24

Muscularis externa

Question 25

Which of these is the duodenum, jejunum, and lleum and what distinguishes them as such?

Answer 25

from L to R Duodenum: Brunner Glands in the submucosa Jejunum: Largest and most plicae circularis ileum: smaller and fewer plicae circularis and Peyer;s patches

Question 26

A 35-year-old woman reported to her primary care physician that she has been experiencing intermittent abdominal discomfort and soft stool and diarrhea for the past year. The frequency and severity of these episodes has gotten worse over the past few months. A biopsy of the small intestines is ordered and the pathology report reveals the presence of chronic inflammatory damage in all layers of the intestinal walls. Based on these initial findings, which of disease would this patient most likely have? Explain: Celiac or Chrohns

Answer 26

Crohn's dz Although chronic inflammation and the resulting damage is shared by both diseases, the inflammation related to Crohn disease, which is caused by multiple factors that are not fully understood, can occur in any or all layers of the intestinal wall. Inflammation from celiac disease (a.k.a. celiac sprue), which is caused by an immune response to gluten and other wheat protein, is typically limited only to the mucosal layer, especially the absorptive enterocytes

Question 27

Review this diagram of the large intestine: What are the 3 main functions?

Answer 27

storing compacting absorbing water

Question 28

What are the 4 main cell types and their functions in the large intestine?

Answer 28

1. Colonocytes — fluid-absorptive, columnar cells with microvilli 2. Goblet cells — mucous cells 3. Enteroendocrine cells 4. Stem cells — pluripotent cells (no large villi or plicae circularis)\ (lumen with intestinal glands)

Question 29

Small intestine or large intestine?

Answer 29

large intestine

Question 30

Review the slides of the large intestine (What is pictured on the top right)?

Answer 30

Lumen ducts (tops slice off)

Question 31

How does the muscularis externa of the large intestine differ from the small intestine?

Answer 31

The longitudinal external layer is concentrated in 3 spots longitudinally on the side called the tenia coli They sometimes penetrate the circular inner layer to form pouches of haustra

Question 32

During a colonoscopy of a 63-year-old male, numerous pouches (out-pocketing) are observed in the colon wall (see images on next slide). What is the name for these physical findings?

Answer 32

Diverticula

Question 33

Are these pouches (diverticula) symptomatic, in and of themselves? Explain

Answer 33

In and of themselves, diverticula do not necessarily cause any problems and can be asymptomatic. However, if fecal matter get impacted, or immobilized, within the diverticula, it can **irritate the mucosa and lead to localized inflammation, infections, or hemorrhaging/ischemia** (if the diverticula impacts blood flow).

Question 34

What is the difference between a true diverticulum and a pseudodiverticulum?

Answer 34

True diverticulum involves all layers of the intestine (which includes the muscularis externa) Pseudodiverticulum does not involve the muscularis externa

Question 35

Which part of the large intestine is loaded with lymphoid nodules and possibly housed the healthy microbiome?

Answer 35

the appendix

Question 36

Sensory endings in the anal canal can distinguish between solids, liquids, and ? And where are these sensory endings mostly located?

Answer 36

gas near the pectinate line

Question 37

What are the differences of the internal and external anal sphincters? Muscle type nerves

Answer 37

the internal anal sphincter is a continuation of the **smooth muscle** of the inner circular muscle layer of the muscularis external and is innervated by the **pelvic splanchnic nerves** the external anal sphincter is **somatic skeletal muscle** and is innervated by the **pudendal nerve**

Question 38

What is the rectoanal junction (anal transition zone)?

Answer 38

The transition from columnar epithelia above the pectinate line to keratinized squamous epithelia below the pectinate line

Question 39

How do external vs. internal hemorrhoids differ in their source, sensory innervation, and presentation in a patient?

Answer 39

**External hemorrhoids** arise from the **external rectal plexus** (inferior to the pectinate line) and are innervated by somatic afferent neurons (pudendal nerve). They are typical visible at the periphery of the anus and painful. **Internal hemorrhoids** arise from the i**nternal rectal plexus** (superior to the pectinate line) and are innervated by visceral afferent neurons (pelvic splanchnic nn). When they are small, they are not visible and do not cause any pain.