Small intestine, pancreas, gallbladder Histology - Shaw

Question 1

What is the Plicae circulares?

Answer 1

• Prominent circular folds in duodenum and upper jejunum
• Disappear in ileum
• May increase surface area by a factor of 3

Question 2

What is the distinct histologic feature of the small intestine Mucosa layer?

Answer 2

Villi

Question 3

What are the three histologic features of the small intestine Mucosa?

Answer 3

• Villi
• Distinct muscularis mucosae
• Plicae circulares: mucosal folds with a submucosal core

Question 4

What are the three histologic features of the Submucosa of the small intestine?

Answer 4

• Forms core of plicae circulares
• Larger blood vessels and lymph vessels
• Submucosa nerve plexi with post-ganglionic cell bodies

Question 5

What are the two layers of muscle in the Muscularis Externa?

Answer 5

• Inner circular layer
• Outer longitudinal layer

Question 6

What is the difference between the Villus epithelium and Crypt epithelium in the Mucosa of the small intestine?

Answer 6

• Villus epithelium: simple columnar
  
  • Absorptive columnar cells (aka enterocyte)
  • Goblet cells
  • Enteroendocrine cells
• Crypt epithelium: simple columnar
  
  • Absorptive columnar cells
  • Goblet cells
  • Enteroendocrine cells
  • Paneth cells (bacterocidal/bacterolytic)
  • Undifferentiated cells (stem cells, mitotic)

Question 7

What compents are in the lamina propria of villi in the Small Intestine?

Answer 7

• Connective tissue core of each villus
• Contains a central lymphatic vessel (lacteal)
• Capillaries and venules present
• Very cellular connective tissue: Lymphocytes, eosinophils, plasma cells, macrophages, fibroblasts, mast cells, smooth muscle cells, etc.

Question 8

Does the muscularis mucosae extend into the villus?

Answer 8

NO

Question 9

Where do the intestinal glands open up in the small intestine?

Answer 9

• Crypts of Lieberkuhn (intestinal glands)
• ***Open at base of villi
• Extend to muscularis mucosae

Question 10

What are the five types of cells located in the small intestine?

Answer 10

• 1. Absorptive columnar cells
• 2. Goblet cells
• 3. Enteroendocrine cells
• 4. Paneth cells
• 5. Undifferentiated (stem) cells

Question 11

What is a unique property of Paneth Cells?

Answer 11

Bacteriocidal properties

Question 12

What are the distinct features of the Duodenum?

Answer 12

• ***Brunner’s glands***
  
  • Secrete an alkaline mucus (pH 8.1-9.3) into lumen of duodenum; neutralizes acid chyme arriving from stomach
  • Glands are located in submucosa and lamina propria
• Many plicae circulares
• Adventitia present

Question 13

What are the unique histologic features of the Ileum?

Answer 13

• Peyer’s patches
  
  • Aggregates of lymphatic nodules
  • M-cells: in epithelium above patches
    
    • Endocytose antigen and transport it to underlying lymphatic tissue
  • Provide precursors of intestinal plasma cells that produce IgA
• Plicae very sparse or absent
• Goblet cells are increasing in numbers

Question 14

What is the Pancreas?

Answer 14

• Exocrine and endocrine gland
  
  • very eosinophilic histologically
• Looks similar to parotid gland in some respects
• Produces ~1200 ml of digestive juice daily

Question 15

What four ducts make up the Pancreatic Duct System?

Answer 15

• Excretory duct
• Intralobular duct
• Intercalated duct
• Acinus

Question 16

What kind of duct forms the majority of the ducts in the Pancreas?

Answer 16

Excretory ducts

Question 17

What are Acinar ducts?

Answer 17

• Secretory Alveoli
  
  • Entirely serous
    
    • Cytological features of serous secretory cells
    • Zymogen granules
    • Basis for eosinophilic staining of apical cytoplasm
    • Contain enzyme precursors (proenzymes)
      
      • Trypsinogen; chymotrypsinogen; proelastases; procarboxypeptidases; lipolytic enzymes (lipases); alpha-amylases; nucleases

Question 18

What is different histologically between the Parotid gland and the Pancreas?

Answer 18

• Capsule - seen best in parotid gland
  
  • can see lobules in parotid
• Connective tissue amount
• Fat cells (more in parotid)
• Striated ducts (distinct in parotid)
• Centro-acinar cells (present in pancreas only)
• Islets of Langerhans (present in pancreas only)

Question 19

What are the 3 histological layers in the gallbladder?

Answer 19

1. Mucosa
   
   • Simple columnar epithelium (TALL) with microvilli
   • Lamina propria
     
     • Loose c.t.
     • Rokitansky-Aschoff sinuses
2. Muscularis externa
3. Adventitia (near liver) or serosa