29/30: GI Tract I & II - Canby Flashcards
four main layers of GI tract from internal to external
mucosa
submucosa
muscularis externa
serosa
most of the GI tract epithelium is…
simple columnar
the proximal and distal segments are stratified squamous
layers of mucosa
epithelium resting on basal lamina
lamina propria
muscularis mucosae
2 segments of GI that contain glands
esophagus
duodenum
submucosal vs. myenteric plexuses
,Submucosal (Meissner’s) plexus – parasympathetic postganglionic neurons and their processes and sympathetic postganglionic fibers; regulates the activity of the muscularis mucosae and the secretory activity of glands (contractile activity, blood flow, secretions)
Myenteric (Auerbach’s) plexus – parasympathetic postganglionic neurons and sympathetic postganglionic fibers; regulates the activity of the muscularis externa (between the different layers of muscle) (peristalsis)
epithelium of mucosa of esophagus
stratified squamous non keratinized - protects against coarse-textured foods
esophageal cardiac glands are found in the lamina propria
muscularis externa of espophagus
proximal v. middle. distal
skeletal m.
mixture
smooth muscle
describe esophageal varices
hepatic portal hypertension due to cirrhosis
desribe barrett’s esophagus
change from stratified squamous epithelium to simple columnar with mucus producing cells/goblet cells
metaplasia due to acid reflux
can progress into adenocarcinoma of esophagus
lymph flow in the _____ is usually upward, whereas lymph flow in lower 2/3 is _______.
of the esophagus
upward
downward
- Incidence of lymphatic metastasis is low if the carcinoma is limited to the mucosa. If the carcinoma spreads into the submucosa, the incidence of metastasis increases to 60%.
- Cancer in the superior 2/3 may spread to the internal jugular, paratracheal nodes, subcarina, and paraesophageal nodes.
- Cancer in the inferior 1/3 tends to spread to the celiac and cardiac nodes
Gastric pits are formed by
the invagination of the surface epithelium into the lamina propria
muscularis externa layers of stomach
i. Inner oblique layer of smooth muscle (this is the added layer – most only have other two)
ii. Middle circular layer of smooth muscle - thickened at the pylorus
iii. Outer longitudinal layer of smooth muscle
describe the cardia of stomach
Short gastric pits Long glands in the lamina propria Simple or branched tubular glands Surface lining, mucous, regenerative, and DNES cells Few parietal cells
describe the fundus and body of stomach
Gastric pits become slightly longer
Gastric glands are still long
Branched tubular glands fill the lamina propria
isthmus vs.
neck vs.
base region of glands
Isthmus region of gland (stem cell niche of stomach)
- Surface lining cells - secrete mucus
- Parietal (oxyntic) cells - secrete HCl and intrinsic factor
- Regenerative cells - replace other cell types as they die off
Neck region of the gland
- Mucous neck cells
- Parietal cells (secrete HCl and intrinsic factor)
Base region of the gland
- Contains many chief (zymogenic) cells - pepsinogen
- Enteroendocrine (DNES) cells - hormone secreting cells
- Some mucous cells
- Few parietal cells
describe the pylorus
Deep gastric pits
Short glands
Branched tubular glands
Surface lining, mucous, regenerative cells; a few parietal cells
Enteroendocrine cells (hormone secreting cells) (G cells – gastrin)
structures that increase SA for absorption in small intestine
plicae circulares – (valves of Kerckring) - Circular folds of submucosa and mucosa (increase 3 fold, increase chyme reabsorption)
intestinal villi – Highly vascular processes of mucosa (increase 10 fold) simple columnar cells
microvilli – increase surface 20-fold (on apical domain of columnar cells)
goblet cells in the duodenum ____ in number as ileum is approached
Increase in number as the ileum is approached
paneth cells
baceteriostatic cells found in intestinal glands (crypts of lieberkuhn)
Peyer’s patches (aggregates of lymphoid nodules extending into lamina propia) indicate what part of intestine?
ileum
4 signature histological features of celiac sprue
4 signature histologic features (enterocytes disarrayed, villus atrophy, crypt hyperplasia, inflammation of lamina propria)
LARGE vs. small intestine
Mucosa
- No folds (plicae circulares) except for the rectum and anal canal)
- Absence of villi
- Intestinal glands are more numerous and longer, more goblet cells, more mucus
- Intestinal glands contain fewer Paneth cells
- Columnar cells have short, irregular microvilli: this presents an ill-defined striated (brush) border
- Goblet cells are more numerous
Muscularis externa
- Outer longitudinal layer of smooth muscle does not completely surround the large intestine
- Instead, three longitudinal bands of smooth muscle are found: these are the teniae coli
describe the folds found in rectum
Longitudinal folds (temporary) - folds of submucosa and mucosa)
Plicae transversales recti (transverse rectal folds; aka folds or valves of Houston) - folds of circular muscle of muscularis externa (some folds also have longitudinal muscle), submucosa, and mucosa
describe the anal columns
Anal columns (columns of Morgagni) - longitudinal folds of submucosa and mucosa. Most distended areas are anal cushions – where internal hemmorhoids form)
before and after the white line of hilton
Pectinate/Dentate line to white line of Hilton
Stratified squamous, nonkeratinized epithelium
Stratified squamous, keratinized epithelium inferior to white line of Hilton - sebaceous glands are present
internal vs. external anal sphincter
Internal anal sphincter
Formed by the inner circular smooth muscle layer of the muscularis externa
Does become thickened
External anal sphincter (skeletal muscle)
what are diverticula?
Outpocketings of the colonic wall are diverticula. A true diverticulum involves all wall layers; whereas, a pseudo-diverticulum only involves the mucosa and submucosa. If it doesn’t have all the layers it is false (acquired) true are more genetic
corners of hepatic lobules =
central of hepatic lobule =
portal triads (portal v. hepatic a bile duct) central v.
Subendothelial space between the endothelial cells of the sinusoids and the hepatocytes
Space of Disse/perisinusoidal space
Microvilli of hepatocytes extend into this space c. Reticular fibers d. Perisinusoidal cells (Ito cells) 1. Accumulate vitamin A Contain lipid droplets 2. Synthesize and secrete growth factors
Hepatic Acinus Zones: 1, 2, and 3 central vein in the middle, forms a diamond shape
Blood to zone 1 closest to blood source
1. Increased oxygen 2. Decreased carbon dioxide 3. Decreased metabolic waste products 4. Increased nutrients
Blood to zone 3 closest to central vein
1. Decreased oxygen 2. Increased carbon dioxide 3. Increased metabolic waste products 4. Decreased nutrients 5. Main site of drug and alcohol detoxification *damage too 6. More susceptible to damage a) Decreased nutrients, particularly during states of malnutrition b) Hypoxic damage
functions of hepatocyte
a. Detoxification via enzymes on SER
b. Glycogen metabolism
c. Blood protein synthesis and secretion (e.g., fibrinogen, factor III, prothrombin, complement, albumin, α-globulin, β-globulin, and lipoproteins)
d. Bile synthesis and secretion – sends to bile duct
bilirubin secretion (broken down blood)
clinical relevance of no submucosa in gall bladder
Absence of submucosa and serosa on the hepatic surface of the GB facilitates the spread of GB cancer to the liver.
Presence of serosa on peritoneal surface of GB limits the spread of cancer to some extent.
