6. GI Histology Flashcards
- Correctly identify and describe components of GI tract on histology (objective)
Answer later
- Describe the physiological roles of different parts of the GI tract (objective)
Answer later
GI tract common structural features in all regions
- Mucosa
- Epithelial lining
- Lamina propria (loose connective tissue)
- Muscularis mucosa - Submucosa (dense connective tissue)
- Muscularis Propria
- Serosa (loose connective tissue)
GI Tract Organ List
Esophagus, Stomach, Small Intestine, Large Intestine, Anal Canal
Esophagus (Mucosa)
Nonkeratinized stratified squamous epithelium; cardiac glands at lower end
Esophagus (Submucosa)
Small esophageal glands (mainly mucous)
Esophagus (Muscularis)
Both layers striated muscle in upper region; both layers smooth muscle in lower region; smooth and striated muscle fascicles in middle region
Esophagus (Adventitia/Serosa)
Adventitia, except lower end with serosa
Stomach (Mucosa)
Surface mucous cells and gastric pits leading to gastric glands with parietal and chief cells (in fundus and body), or to mucous cardiac glands and pyloric glands.
Stomach (Submucosa)
No distinguishing features
Stomach (Muscularis)
Three indistinct layers of smooth muscle
Stomach (Adventitia/Serosa)
Serosa
Small Intestine (Mucosa)
Plicae circulares; villi, with enterocytes and goblet cells, and crypts/glands with Paneth cells and stem cells; Peyer patches in ileum
Small Intestine (Submucosa)
Duodenal (Brunner) glands (entirely mucous); possible extensions of Peyer patches in ileum
Small Intestine (Muscularis)
No distinguishing features
Small Intestine (Adventitia/Serosa)
Mainly serosa
Large Intestine (Mucosa)
Intestinal glands with goblet cells and absorptive cells
Large Intestine (Submucosa)
No distinguishing features
Large Intestine (Muscularis)
Outer longitudinal layer separated into three bands, the teniae coli
Large Intestine (Adventitia/Serosa)
Mainly serosa, with adventitia at rectum
Anal Canal (Mucosa)
Stratified squamous epithelium; longitudinal anal columns
Anal Canal (Submucosa)
Venous sinuses
Anal Canal (Muscularis)
Inner circular layer thickened as internal sphincter
Anal Canal (Adventitia/Serosa)
Adventitia
Pancreas
Mixed exocrine and endocrine gland
Produces digestive enzymes and hormones
-Exocrine function: 1.5L of alkaline pancreatic juice per day into the duodenum; proteases, amylase, lipases
-Endocrine function: insulin, glucagon and somatostatin
Liver
Main digestive function is bile production
Hepatocytes:Key cells
Functionally diverse: synthesis of plasma proteins, conversion of aa into glucose, produce urea, storage of glucose/vitamin A/iron
GI Tract 1/6
Interfaces with outside world to absorb things
- Function: acquire nutrient molecules from food and eliminate indigestible remnants
- Secondary function: maintain barrier between contents of lumen (toxins,bacteria) and rest of body
- Functional tissue is epithelium (varies by location in tract)
GI Tract 2/6
Oral cavity, pharynx, esophagus, anal canal: protective mucosa, characterized by abrasion-resistant stratified squamous epithelium
GI Tract 3/6
Stomach: secretory mucosa, epithelial glands specialized to secrete acid and digestive enzymes, as well as mucous to protect itself from acid and enzymes
GI Tract 4/6
Small intestine: absorptive columnar mucosa interspersed with goblet cells; responsible primarily for absorbing digested nutrients
-Epithelial specializations include folding (plicae and villi) and apical projections (microvilli) to increase surface area for absorption
GI Tract 5/6
Large intestine: absorptive/protective mucosa, specializes in water absorption (columnar cells) and mucous secretion (goblet cells)
Especially in large intestine, tight junctions are actually selectively permeable to allow for movement of water and ions
GI Tract 6/6
Underlying epithelium: stroma of GI tract includes loose connective tissue (lamina propria), smooth muscle (muscularis mucosa), dense fibroelastic connective tissue (submucosa), more smooth muscle (muscularis externa), and more loose connective tissue (serosa or adventitia)
-Lamina propria+muscularis mucosa: serve as closely related support/localized movement for epithelium and together make up mucosa
