Week1: esophagus, stomach, exocrine pancreas MA

Question 1

4 layers of esophagus

Answer 1

inside to out

1. Mucosa: stratified sq. epithelium, loose CT (lamina propria), and muscularis mucosae (SM)
2. Submucosa: dense CT
3. Muscularis externa
   - 2 layers, inner is circular, outer is longitudinal
   - upper is skeletal, lower is smooth
4. Adventitia

Question 2

Interior surface of stomach

Answer 2

• rugae: folds of mucosa and submucosa that allows stomach to expand
• gastric pits: invaginations that lead to gastric glands
• on the surface are simple columnar cells (mucous cap cells) that provides protection and lubrication of stomach

Question 3

Gastric gland microanatomy

Answer 3

1. mucous neck: underneath mucous cap. more acidic mucous
2. Chief cells: secrete proenzymes
3. parietal cells: secrete HCl and intrinsic factor (absorbs B12). Large cells.
4. Enteroendocrine cells (EEC): secrete variety of hormones

Question 4

Parietal cell- microanatomy

Answer 4

• have indentations called secretory canaliculi which is where HCl is released into
• the cytoplasm of parietal cells are pH 7.0-7.2
• secretory canaliculi pH<1.0
• sER tubulovesicles contain stored microvilli and appear in canaliculi in the activated parietal cell. Tubulovesicles are incorporated into the surface in active state.
• tubulovesicles store intrinsic factor, which is released in the activated parietal cell
• surface ATPases for H and Cl pumps
• while HCl can be continually released, IF can only be released for 30 mins before needing to be replenished

Question 5

Enteroendocrine system-microanatomy

Answer 5

-at least 20 cell types, secretory granules accumulate and released basally
-also paracrine regulation: affect neighboring cells
Two types of EEC
1. Cell is open to lumen
2. closed to lumen

Question 6

Gastric mucosa restitution

Answer 6

-gastric epithelium has ability to repair itself quickly
-depends on damage to basal lamina
normal replacement for mucous cap cells is 3-5 days

Question 7

Exocrine pancreas: cell types and function

Answer 7

1. Acinar cells
   - release 15+ proenzymes into duodenum
   - trypsinogen released, activated in duodenum to trypsin, which activates other proenzymes
   - also releases trypsin inhibitor to prevent premature activation (autosuggestion of pancreas)
   - tight jxns between cells
2. Centroacinar cells and intercalated duct cells
   - release trypsin inhibitor and bicarbonate
   - -These cells regulated by hormones and neural input
   - cholecystokinin: from EEC, stimulates pancreatic enzymes and gallbladder contraction
   - secretin: from EEC in small intestines, stimulates centroacinar cells to release alkaline fluid