Histology Flashcards
What are the three layers of the generalized gut mucosa?
1) Epithelium
2) Lamina Propria
3) Muscularis Mucosae
What types of epithelium exist in the generalized gut?
Either stratified squamous or simple columnar
Where is there no muscularis mucosa?
In the oral cavity, anal canal, or gall bladder
What is found in the submucosa of the generalized gut?
Dense irregular connective tissue and Meissner’s plexus of sympathetic and post-ganglionic parasympathetic fibers that innervate the muscularis mucosa
What are the two main layers of the Muscularis externa?
An inner circular layer (usually smooth, but skeletal in the mouth and esophagus)
Outer longitudinal layer (also smooth usually, but skeletal in mouth, esophagus and external anal sphincter)
What nerves supply the muscularis externa?
Auerbach’s plexus
What is the difference between a serosa and an adventitia?
If the organ has a mesothelium and is peritoneal, it has a serosa; if the organ is not peritoneal, the outer layer is an adventitia
What are the three types of oral mucosa, what features do they have, and where are they found?
1) Masticatory–has keratin, on gingiva and hard palate
2) Specialized–has keratin and papillae, on dorsal tongue
3) Lining–no keratin, robust and flexible; elsewhere in mouth
What are the four types of papillae found on the tongue? Which have taste buds and keratin?
1) Filiform–no taste buds, very keratinous
2) Fungiform–less numerous, has taste buds and some keratin
3) Circumvellate–papillae near terminal sulcus, has taste buds
4) Foliate–has taste buds, but poorly developed in humans
What structure cleanses taste buds?
The serous glands of von Ebner
What type of epithelium is found in the esophagus?
non-keratinized stratified squamous
What feature exists in the submucosa of the esophagus?
Esophageal glands that secrete mucus to lubricate esophagus
How does the muscularis externa appear histologically in the esophagus?
The proximal 1/3 is all skeletal muscle
The middle 1/3 is a transitional mix between skeletal and smooth muscle
The distal 1/3 is all smooth muscle
What are the four regions of the stomach?
The cardia, pylorus, fundus, and body
What type of epithelium exists in the stomach and what histological structure generates its acids and enzymes?
Simple columnar; gastric pits and glands
What is the purpose of rugae and where are they found histologically?
They are infoldings that allow the stomach to distend; found in the submucosa
What is unique about the stomach’s muscularis externa?
There is an additional layer of inner oblique muscles that promote additional churning
Which layer of the stomach’s muscularis externa forms the pyloric sphincter?
The middle circular
What types of cells are found in the pit region of the gastric pit? What do they make?
Surface mucus cells; secrete mucus
What types of cells are found in the neck region of the gastric gland? What do they make?
Mucus cells—mucus
Parietal cells–HCl and intrinsic factor (very eosinophilic)
What types of cells are found in the base region of the gastric gland? What do they make?
Predominantly chief cells–zymogens (very basophilic)
What are the main zymogens of the stomach and what are their roles?
Pepsinogen–protein digestion
Rennin/chymosin–curdle milk to slow digestion in infants
Where are G-cells found and what do they secrete?
In the body and pylorus of the stomach; gastrin
What are roles of gastrin?
Promotes parietal cell activity
Promotes chief cell activity
Promotes increased muscular contractions in the stomach
Where are D-cells found and what do they secrete? What prompts their secretions?
In the pylorus; somatostatin
Acids
What is the main role of somatostatin?
Inhibition of G-cells and decrease of biliary and pancreatic secretions
Where are ghrelin cells found and what is their role?
In the body; release ghrelin with low glucose to promote appetite
How do gastric glands appear in the cardiac region of the stomach?
- the pits are short
- glands are long and coiled
- secrete high levels of mucus
How do gastric glands appear in the principal region of the stomach?
- the pits are short
- the glands are long and branched
- have mucus, chief, and parietal cells
How do gastric glands appear in the pyloric region of the stomach?
- the pits are long
- the glands are short and coiled
- secrete high levels of mucus
How does the small intestine increase its surface area?
1) pliae circulares–permanent folds of mucosa and submucosa (x3)
2) villi–finger projections of epithelium and lamina propria (x10)
3) microvilli–apical cellular projections (x20)
What are the types of cells found in the crypts of Lieburkuhn?
Enterocytes (absorption) Goblet cells (mucus) Stem cells Paneth cells (anti-bacterial--small intestine only) Enteroendocrine cells
Where are goblet cells densest in the intestines?
Duodenum
Where are S-cells found, what do they secrete, and what is that secretion’s function?
Duodenum; secretin; decrease acid in the stomach and promote bicarbonate secretions by the acinar pancreas
Where are I-cells found, what do they secrete, and what is that secretion’s function?
Duodenum and jejunum; CCK; promote relaxation of the gallbladder to increase bile, increase trypsinogen release, decrease hunger
What do E cells secrete and what is that secretion’s function?
Serotonin; promoted peristalsis
How can the three segments of the small intestine be identified histologically?
The duodenum has Brunner’s glands—tubular mucus glands that secrete alkaline substances into the duodenum
Jejunum–lacks unique features
Ileum–has Peyer’s patches
How can the appendix be identified histologically?
Looks much like the large intestines but lacks teniae coli and has many lymphoid nodules (NOT Peyer’s patches because they encircle entire organ)
What are modifications of the large intestine’s epithelium compared to the small intestine?
deeper crypts of Lieberkuhn
higher mucus secretion
no villi nor microvilli
What is the teniae coli?
Modulations of the outer longitudinal layer of the muscularis externa into three bands that permits independent contraction and compacts feces
How much saliva do the main salivary glands produce daily?
Submandibular–600 mL
Parotid—300 mL
Sublingual 50 mL
Minro–50 mL
What is the role of the stroma in the salivary gland?
Connective tissues that divide the gland into lobes and lobules
What types of cells exist in the parenchyma of salivary glands and what are their roles?
1) Serous cells—pyramidal shaped, round nucleus, in acini, secrete enzymes
2) Mucus cells–columnar/pyramidal, flat nucleus, secrete mucin
3) Myoepithelial cells–contractile cells that surround secretory units
What are the four stages of duct that saliva travels through?
1) Intercalcated ducts
2) Non-striated intralobar ducts OR striated intralobar ducts
3) Interlobular ducts
4) Main excretory duct
What is the role of the intercalated duct? How does it appear histologically?
Made of simple cuboidal epithelium
Makes antibacterial lysozymes and lactoferrin
What is the role of the non-striated interlobar duct? How does it appear histologically?
Made of simple columnar epithelium
Involved in mucus secreting glands
What is the role of the striated interlobar duct? How does it appear histologically?
Made of simple columnar epithelium
Has a striated basal membrane with many mitochondria that change the tonicity of saliva by secreting K and HCO3
Where are interlobular ducts found and how do they appear histologically?
They are in the septa; made of pseudostratified epithelia
What is the predominant gland type found in the parotid gland? What is the excretory duct called? What does it make?
- -serous acinar cells (have striated interlobar ducts)
- -Stensen’s duct
- -alpha-amylase and antimicrobial proteins
What is the predominant gland type found in the submandibular gland? What is the excretory duct called? What does it make?
- -tubuloacinar glands with serous demilunes
- -mostly serous in nature, has striated interlobar ducts
- -Wharton’s duct
- -alpha-amylase, proline-rich proteins, lysozyme, mucus
What is the predominant gland type found in the sublingual gland? What is the excretory duct called? What does it make?
- -tubuloacinar gland; mostly mucosal
- -non-striated interlobar ducts
- -Bartholin’s duct
- -mostly mucus production
What are the two types of exocrine cells found in the pancreas and what do they produce?
Serous acini and ducts–most enzymes
Centro-acinar–HCO3-
What are the components of the porta hepatis?
Hepatic portal vein
Hepatic artery
Lymphatic supply
Biliary duct (common hepatic)
What is the name of the hepatic stroma and what type of connective tissue is present?
Glisson’s capsule
Type III collagen (reticular)
What are distinguishing histological characteristics of hepatocytes?
–presence of glycogen granules and high levels of rough endoplasmic reticulum
What are structural features of the sinusoids?
- highly fenestrated cellularly and have fenestrated basement membrane
- ferries both portal venous blood and arterial blood to central vein
What do Kupffer cells do?
They are hepatic macrophages
What is the space of Disse?
It is an actual space between sinusoids and hepatocytes where hepatic microvilli extend and extract nutrients and oxygen
What are bile canaliculi?
small spaces surrounded by plasma membrane that receive bile from hepatocytes and ferries them to bile ducts
How does the gallbladder appear histologically?
Simple columnar epithelium with microvilli; folded lamina propria, NO muscularis mucosa; very thick muscularis externa
