TBL 17: Mesenteries, Esophagus, Stomach Flashcards
What is the primitive stomach attached to? how?
the body wall by the dorsal mesogastrium and ventral mesogastrium
Describe the oritentation of the stomach
What creates the greater and lesser curvatures of the stomach?s
the stomach rotates 90⁰ clockwise around its longitudinal axis causing its left side to face anteriorly and its right side to face posteriorly.
During the rotation, the original posterior wall grows faster than the original anterior wall thus creating the greater and lesser curvatures of the stomach.
What forms the omental bursa?
What forms the lesser omentum and falciform ligament?
the 90⁰ clockwise rotation pulls the dorsal meso-gastrium to the left creating the omental bursa (aka lesser sac) posterior to the stomach
the rotation also pulls the ventral mesogastrium to the right where it forms the lesser omentum and falciform ligament.
What does additional rotation of the stomach around its antero-posterior axis do?
What does this rotation do to the duodenum?
additional rotation of the stomach around its antero-posterior axis moves its distal part to the right and upward and its proximal part to the left and downward.
envision this rotation pulls the duodenum to the right creating its characteristic C-shaped loop.
the rotation also causes the dorsal mesogastrium to bulge downward and its continuous growth forms the double-layered greater omentum
What does the ascending portion of the looping greater omentum fuse with?
the ascending portion of the looping greater omentum fuses with the descending portion and together they join the transverse mesocolon.
What surrounds the esophageal mucosa?
What do these layers form?
internal circular and external longitudinal muscle layers surround the esophageal mucosa.
the layers form the muscularis externa that continues along the entire gastrointestinal (GI) tract.
What does the myenteric plexus between the two muscle layers contain?
What induces serial contractions of the muscularis externa? What does this create?
the myenteric plexus between the two muscle layers contains parasympathetic neurons of the enteric nervous system (ENS).
activation of the neurons by local hormones or metabolites induces serial contractions of the muscularis externa creating peristaltic waves along the GI tract.
What forms periarterial plexuses and what do they supply?
What do the presynaptic vagal fibers synapse with? What does this do?
branches of the vagus nerve and postsynaptic sympathetic fibers form periarterial plexuses that supply the foregut (and midgut and hindgut) derivatives.
the presynaptic vagal fibers synapse with ENS neurons to accelerate the rates of peristaltic wave formation and glandular secretion.
Where do the postsynaptic sympathetic fibers directly enter? What do they do?
the postsynaptic sympathetic fibers directly enter the muscularis externa and submucosa to diminish the rates of muscular contraction and glandular secretion caused by the submucosal and myenteric plexuses.
What is between the mucosa and muscularis externa of the esophagus?
What is the adventitia external to the muscularis externa made of?
the collagen and elastic fiber-rich submucosa is between the mucosa and muscularis externa.
the adventitia external to the muscularis externa is a loose connective tissue layer without a covering mesothelium i.e., only its short abdominal part is intraperitoneal and enclosed by visceral peritoneum.
What forms the esophageal mucosa?
What forms the muscularis mucosae? What is the function of this?
nonkeratinized stratified squamous epithelium and a richly vascular lamina propria form the esophageal mucosa.
a longitudinal layer of smooth muscle forms the muscularis mucosae that continues along the entire GI tract to create mucosal folding that assists peristaltic propulsion of digested substances along the tract.
What does the muscularis externa consist of?
Where are skeletal muscle bundles predominant? Where are smooth muscle bundles?
the muscularis externa consists of skeletal muscle fibers and smooth muscle fibers organized into distinct bundles.
skeletal muscle bundles are predominant in the proximal esophagus and smooth muscle bundles characterize the distal esophagus. (makes sense so you can control swallowing!)
What do submucosal secretory acini secrete? What is the purpose?
submucosal secretory acini secrete mucus into ducts that open into the esophageal lumen thus lubricating the epithelial apical surface.
What happens to the nonkeratinized stratified squamos epithelium at the esophagogastric junction?
the nonkeratinized stratified squamous epithelium abruptly changes to simple columnar epithelium at the esophagogastric junction
What is the clinical relevance of the esophagogastric junction?
the Z line is the most common site of esophageal carcinoma.
Why is projectile vomiting a symptom of pyloric stenosis?
Projective vomiting occurs because passage of food is obstructed
What is Barrett’s esophagus and what is the likelihood of its transformation into an adenocarcinoma?
BARRETT’S ESOPHAGUS – metaplasia (reversible replacement of one differentiated cell type with another mature differentiated cell type) of the esophageal epithelium
• Columnar epithelium (like that of stomach) replaces the normal stratified squamous epithelium in the esophagus
• Patients with persistent GERD are predisposed to barrett’s esophagus
o Acid reflux disrupts esophageal mucosal barrier
• It may rarely lead to a more serious adenocarcinoma
Why is esophageal adenocarcinoma associated with rapid tumor cell metastasis outside the esophageal boundaries?
Lack of serosa along most of esophageal length (except the segment below the diaphragm) –> rapid tumor metastasis outside of the esophageal boundaries
What is the most common cause of esophagitis and what conditions are typically associated with the causation?
ESOPHAGITIS – inflammation of esophagus w/ damage to the epithelium
• Most common cause – reflux of gastric contents (GERD) into the lower esophagus
o Impairs reparative capacity of esophageal mucosa
• Typically associated with:
o Hiatal hernia
o Incompetent lower esophageal sphincter
What cells populate the gastric glands?
What cells do glands in the fundus and body of stomach contain? What cells do glands in the pylorus contain?
mucous cells, parietal cells, and chief cells populate the gastric glands.
glands in the fundus and body of the stomach contain all three cell types
glands in the pylorus contain only mucous cells
What are plicae circulares in the duodenum?
What are finger-like villi created by?
plicae circulares **are macroscopic folds of mucosa and submucosa
- Unlike the folds in the stomach, they are permanent, and are not obliterated when the intestine is distended.**
- In the horizontal and ascending portions of the duodenum and upper half of the jejunum they are large and numerous, but from this point, down to the middle of the ileum, they diminish considerably in size.
- In the lower part of the ileum they almost entirely disappear; hence the comparative thinness of this portion of the intestine, as compared with the duodenum and jejunum.
finger-like villi are created by mucosal projections from the folds.
What is the duodenal submucosa filled with?
What do the glandular ducts produce? Why?
the duodenal submucosa is filled with distinctive mucous glands (of Brunner).
the glandular ducts deliver mucous with high bicarbonate ion concentrations into the duodenal lumen thus buffering the acidic discharge from the pylorus.
What treatment effectively promotes healing of peptic ulcers?
Antibiotics effectively promote their healing
Recall spatial relations of the spleen with the liver, stomach, pancreas, and left kidney in the left upper quadrant of the abdominal cavity
What constitutes the splenic pulp?
the spleen is intraperitoneal
its connective tissue capsule and inward projecting trabeculae encompass a dense meshwork of reticular fibers designated the splenic pulp
What does the splenic white pulp and red pulp contain?
the pulp contains scattered lymphoid nodules collectively designated white pulp.
the vast intervening pulp is filled mainly with erythrocytes; thus it is called red pulp.
What permeates throughout the red pulp?
What are endothelial cells of the sinusoids separated by? What is their function?
venous sinusoids permeate throughout the red pulp.
endothelial cells of the sinusoids are separated by slit-like spaces, which blood cells can easily squeeze through, except aged RBCs that lose their pliability and are phagocytized by macrophages in the red pulp.
Where do branches of the splenic artery pass from?
Where do most of the smaller branches open directly into?
Where does blood enter after filtration?
branches of the splenic artery pass from the capsule –> contiguous trabeculae where smaller branches arise and enter the splenic pulp.
most of the smaller branches open directly into the red pulp between the venous sinusoids; thus aged RBCs and antigens are readily filtered from the blood.
after the filtration, blood enters the porous sinusoids that drain into tributaries of the splenic vein.
How do clinical consequences of splenectomy in children differ from those in adults?
SPLENCTOMY
• In adults – no clinical consequence (asymptomatic)
• In children – INC occurrence + severity of infx (immune system not fully developed)
