Week 7: Digestive Histology

What are the 4 layers of the gut tube from deep to superficial?

Mucosa, submucosa, muscularis externa, serosa or adventitia

What are the 3 layers of the mucosa?

Epithelium, lamina propria, muscularis mucosae

What type of tissue is the mucosal epithelium?

Stratified squamous or simple columnar

What type of tissue is the lamina propria?

Loose connective

What is the function of the muscularis mucosae?

Permit local mucosal movements

What type of tissue is the submucosa?

Dense connective

What does the submucosa contain?

Blood/lymph vessels, Meissner’s (submucosal) plexus, glands, significant lymphoid tissue

What significant structure of the duodenum is found in the submucosa?

Brunner’s glands

What significant structure of the ileum is found in the submucosa?

Peyer’s patches

What type of muscle is the muscularis externa, and what is the exception?

Smooth, part of esophagus

For the exception of the stomach, how many layers does the muscularis externa contain? What are they called?

2, inner circular and outer longitudinal

What connects the layers of the muscularis externa, and what does this area contain?

Sparse connective tissue, blood/lymph vessels and Auerbach’s (myenteric) plexus

What is the name of the combination of Meissner’s plexus and Auerbach’s plexus?

Enteric nervous system

Where is serosa found instead of adventitia?

Intraperitoneal organs suspended in the abdomen

What type of tissue is serosa/adventitia?

Simple squamous mesothelium

What is serosa continuous with?

Visceral peritoneum

What types of organs have adventitia rather than serosa?

Retroperitoneal or subperitoneal

What structures are found within the lamina propria of the esophagus?

Mucus-producing esophageal cardiac glands

What structures are found within the submucosa of the esophagus?

Proper esophageal glands

What portion of the esophagus contains serosa?

Distal 1-2 cm

Describe the tissue transition at the esophagogastric junction

Stratified squamous to simple columnar

What is the name for the abrupt tissue transition at the esophagogastric junction?

Z-line

What type of tissue is the mucosa of the esophagus?

Simple squamous

What type of tissue is the mucosa of the stomach?

Simple columnar

What enzymes does the stomach produce?

Pepsinogen, gastric lipase, rennin

What hormones does the stomach produce?

Gastrin, histamine, somatostatin, intrinsic factor

What structures sit within the gastric pits of rugae?

Gastric glands

What are the 4 important cell types within gastric glands?

Parietal, DNES, G cells, chief cells

What do parietal cells produce?

HCl, intrinsic factor

What do G cells produce?

Gastrin

What do DNES cells produce?

Somatostatin, secretin, CCK

Where are chief cells found (what do they produce)

Fundus (pepsin, rennin, lipase precursors)

How many layers is the muscularis externa in the stomach, and what are they called?

3, outer longitudinal, middle circular, inner oblique

Which layer of the muscularis externa within the stomach thickens to form the pyloric sphincter?

Middle circular

What are the circular folds within the small intestine called, and what layer are they formed from?

Plica circularis, submucosa

What tissue type is the mucosal epithelium of the small intestine?

Simple columnar

What are the exocrine cells of the pancreas, and what do they produce?

Acinar cells, pancreatic juice

What are the endocrine cells of the pancreas, and what do they produce?

Islets of Langerhans, containing alpha cells (glucagon) and beta cells (insulin)

Which proenzymes do acinar cells produce?

Trypsin, chymotrypsinogen

What do the cells of intercalated ducts produce in the pancreas?

Alkaline fluid

What do pancreatic delta cells produce?

Somatostatin

What do pancreatic epsilon cells produce?

Ghrelin

What is the name of the dense, collagenous capsule that surrounds the liver?

Glisson’s capsule

What is the largest gland of the body?

Liver

What shape are the fenestrae of hepatic sinusoids?

Slit

What space prevents hepatocytes from coming into direct contact with the bloodstream?

Space of Disse

What is the name given to hepatic macrophages?

Kupffer cells

What is the name given to hepatic NK cells?

Pit cells

Which cells accumulate and store vitamin A?

Perisinusoidal stellate cells

What is another name for perisinusoidal stellate cells?

Ito cells

What is another major function of Ito cells?

Collagen manufacturing

What is the main exocrine function of the liver?

Production of bile

What are the endocrine functions of the liver?

Produces plasma proteins, stores iron, lipids, glucose, and vitamin A, synthesize lipoproteins, transport IgA, detoxification

What stimulates the gallbladder to release bile?

CCK and ACh

Does the gallbladder have a submucosal layer?

No

What tissue type is the epithelium of the cystic mucosa?

Simple columnar

Does the gallbladder have a muscularis mucosae?

No

Describe the cystic muscularis externa

Tunica muscularis, contains lots of collagen

Where does the gallbladder contain adventitia rather than serosa?

Where gallbladder lies up against liver

Does the large intestine have villi?

No

Does the colon have any major folds?

No

Does the rectum have any major folds?

Yes

What is the main function of the large intestine?

Absorption of water and electrolytes

What does the colic lamina propria contain?

Crypts of Lieberkuhn

What is the outer longitudinal layer of colic muscularis externa?

Teniae coli

What tissue type is colic mucosal epithelium?

Simple columnar

What does the inner circular layer form in the sigmoid colon?

Internal anal sphincter

Where in the large intestine is there adventitia rather than serosa?

Lower part of rectum

Does the rectum have haustra?

No

Describe the tissue transition at the rectoanal junction

Simple columnar to simple cuboidal to stratified squamous

What type of cells proliferate around the rectum?

Goblet cells

What layers form the anal columns?

Mucosa and submucosa

What tissue type is the anal mucosa?

Stratified squamous

What structures are formed by the lamina propria of the anus?

Longitudinal anal columns

What venous structures are contained within the anal submucosa?

Sinuses that connect the superior rectal veins with middle and inferior