12.6 Histology: Gastrointestinal histology Flashcards
What are the layers of the GIT? (4)
Mucosa
Submucosa
Muscularis externa
Serosa
What is the mucosa supported by? What forms the boundary of mucosa?
Lamina propria (connective tissue layer containing nerves and blood vessels)
Muscularis mucosae forms the boundary
What type of tissue is the submucosa? What does it do?
Dense, irregular connective tissue
Provides strength and elasticity
What are the two layers of the muscularis externa?
Smooth muscle:
Inner: circumferential
Outer: longitudinal
What is the epithelium of the serosa? Why?
Simple squamous to provide a non-stick surface
What is the enteric nervous system responsible for? (3)
Mixing, peristalsis and secretion
Where do the enteric nerve plexuses lie? (2)
Myenteric: between longitudinal and circular
Submucous: lies in the submucosa
What type of epithelium exists in the esophagus?
Are there glands?
Stratified squamous epithelium
Submucosal glands (lubrication)
What are the only parts of the GIT that have smooth muscle in them?
Muscular externa (esophagus)
Anal sphincter
What type of muscle are the three layers of the esophagus comprised of?
Top third: skeletal
Middle: mixed
Bottom third: smooth
What controls release of material into intestine?
Pyloric sphincter
What is the function of the stomach (2)?
What does it do minimally?
Initiate digestion (PRO) Chyme: production/regulation
(minimal absorption)
What is the epithelium of the stomach?
Simple columnar secretory epithelium
What is the inner surface of the stomach like?
Low folds, rugae: contains gastric pits–>glands
What kind of glands are gastric glands?
What gives rise to these?
Simple tubular glands (into LP)
Gastric pit gives rise to 3-5 GGs
What are some cells in the gastric gland? (4)
What do they produce?
Regenerative cells:neck
Mucous neck cell (mucus)
Parietal cell (HCl)
Chief cell (pepsinogen): base
What is the role of pepsin?
Protein breakdown–>peptides and amino acid
How is pepsinogen activated?
Acid environment cleaves pepsinogen to pepsin
What type of epithelium exists on the small intestine?
Simple columnar epithelium
Where are villi present? What does the base give rise to?
Villi: on transverse folds (plica circulares)
Base of villi: tubular glands (Crypts of Leiberkuhn)
Which cells in the small intestine have microvilli?
All columnar epithelium except goblet cells)
How is surface area increased in the small intestine?
Plica circulares: 2-3x
Villi: 10x
Microvilli: 20x
What are the Crypts of Leiberkuhn? What do they do?
Penetrate into LP (small intestine)
Secrete mucus (Goblet cells on villi) and fluid
Contain stem cells
What does the lamina propria in the small intestine contain? Where does it run?
MM, BV, lymph, immune cells
Extends into core of each villus
