TBL 17 Flashcards

1
Q

What are mesentries? What is the dorsal mesentery?

A

Mesenteries are formed at the sites of continuity between the parietal and visceral peritonea.

The gut tube is suspended from the dorsal (posterior) wall by the dorsal mesentery and the mesentery extends from the abdominal portion of the esophagus to the end of the hindgut.

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2
Q

What is the septum transversum derived from? What derives from the septum transversum?

A

Visceral mesoderm that surrounds the heart tube.

The ventral mesentry is derived from the septum transversum. It connects the abdominal part of the esophagus, the stomach and proximal duodenum to the ventral (anterior) body wall.

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3
Q

What is the liver bud?

A

It is an endodermal outgrowth from the proximal duodenum, which grows into the septum transversum.

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4
Q

What forms the falciform ligament and lesser omentum?

A

The growth of the liver within the septum transversum separates the ventral mesentery into the falciform ligament and lesser omentum. The septum transversum goes on to become the central tendon of the diaphragm.

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5
Q

What suspends the fusiform stomach from the dorsal body wall?

A

Dorsal mesogastrium which is a portion of the dorsal mesentery associated with the stomach

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6
Q

Describe the rotation of the fusiform stomach.

A

The fusiform stomach rotates 90 degress clockwise around its longitudinal axis, which causes the 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 creating the greater and lesser curvatures of the stomach.

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7
Q

What does additional rotation of the stomach around the anteroposterior do?

A

It move the distal part of the stomach to the right and upward and its proximal part to the left and downward. The rotation pulls the duodenum to the right creating its C-shaped loop.

It also causes the dorsal mesogastruum to bulde downward from the greater curvature as the double layered greater omentum. The descending portion of the looping greater omentum fuses with the ascending portion to create its four-layered structure.

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8
Q

Where do the primoridia of the pancreas and spleen originally reside?

A

pancreas: dorsal mesentery
spleen: dorsal mesogastrium

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9
Q

What does stomach rotation do to the mesenteries?

A

The stomach rotations pull the mesenteries to the left where the dorsal mesentery partially fuses with the parietal peritoneum of the posterior body wall and places the pancreas in its retroperitoneal location.

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10
Q

What does the dorsal mesogastrium do?

A

It encloses the spleen as visceral peritoneum and creates the gastrosplenic ligament that connects the stomach to the spleen.

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11
Q

What does the non-fused portion of the dorsal mesentery form?

A

It forms the splenorenal ligament that connects the spleen to the body wall in the region of the retroperitoneal left kidney.

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12
Q

What does the esophageal mucosa consist of?

A

richly vascular lamina propia covered by non-keratinized stratified squamous epithelium

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13
Q

At the esophagogastric junction, what happens to the nonkeratinzed stratified squamous epithelium? What is this change’s clinical relevance?

A

The nonkeratinized squamous epithelium abruptly changes to simple columnar epithelium as the esophagogastric junction. This serrated border (called the Z line) is important because it is the most common site of esophageal carcinomas.

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14
Q

What is Barrett’s esophagus and what is the likelihood of its transformation into an adenocarcinoma?

A

It is metaplasia of the esophageal epithelium which means that the stratified squamous epithelium is replaced by the columnar epithelium. This can happen anywhere above the gastroesophageal junction. It may rarely lead to the more serious adenocarcinoma.

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15
Q

What is the most common cause of esophagitis and what conditions are typically associated with the causation?

A

Inflammation of the esophagus with damage to the epithelium is called esophagitis. Its most common cause is reflux of gastric contents into the lower esophagus, which impairs reparative capacity of esophageal mucosa.

Conditions:
Gastroesphageal reflux disease
Hiatal hernia

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16
Q

What is the muscularis mucosae?

A

It is a longitudinal layer of smooth muscle which separates the mucosa and submucosa. This muscle layer is present along the entire GI tract. Periodic contractions of the muscularis mucosae creates the folding of the mucosa to assist peristaltic propulsion.

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17
Q

What does the submucosa of the esophagus do?

A

It seperates the muscularis mucosae and muscularis externa

It also has secretory acini that secrete mucus into ducts that open into the esophageal lumen to lubricate the apical surface of the lining epithelium.

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18
Q

What is the muscularis externa of the esophagus?

A

It consists of inner circular smooth and outer longitudinal skeletal muscle layers. Skeletal muscle is present in the outer layer in the proximal 1/3 of the esophagus and smooth muscle composes both layers in the distal 2/3.

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19
Q

Where is the adventitia of the esophagus located? What is it composed of?

A

It is located external to the muscularis externa and consists of loose connective tissue without a covering mesothelium. (Only the short abdominal portion of the esophagus is intraperitoneal and enclosed by visceral peritoneum).

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20
Q

Why is esophaeal adenocarcinoma associated with rapid tumor cell metastasis outside the esophageal boundaries?

A

The lack of serosa along most of the esophageal length may account for the rapid spread of metastatic tumor cells outside esophageal boundaries.

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21
Q

What arteries supply the esophagus?

A

The left gastric artery supplies the abdominal part of the esophagus and branches of the descending aorta supply the thoracic part.

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22
Q

What is the orders of the layers of esophagus?

A

FROM OUTSIDE TO INSIDE:

Mucosa –> muscularis mucosae –> subcomusa –> muscularis externa –> adventia

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23
Q

What is rugae?

A

It is macroscopic folds of mucosa and submucosa that flatten as the stomach fills.

24
Q

In the stomach, what does the serosa do?

A

It covers the muscularis externa and represents the adventitia covered by visceral peritoneum.
(The intraperotioneal GI tract viscera have a serosa and retroperitoneal intestinal viscera have an adventitia).

25
Q

Describe the gastric glands of the stomach.

A

The simple columnar epithelium dips to join long gastric glands. These glands extend from the lamina propia to the muscularis mucosae. These glands are populated by the mucous cells, parietal cells, and chief cells.

of the fundus and body of the stomach: all three cell types
pylorus: mucous cells only!

26
Q

What do parietal cells do? Chief cells?

A

Parietal cells actively transport hydrogen ions into the glandular lumens where union with chloride ions form hydrochloric acid.

Chief cells secrete the proenzyme pepsinogen that in the acidic environment of the glandular lumens is converted to pepsin the active digestive enzyme.

27
Q

What is the function of intrinsic factor, a secretory product of the parietal cells?

A

It is a glycoprotein that facilitates vitamin B12 absorption in the proximal small intestine.

28
Q

How does pernicious anemia affect the gastric mucosa?

A

Pernicious anemia is a form of megaloblastic anemia. It is an autoimmune disease resulting in marked atrophy of gastric mucosa, destruction of parietal cells, and failure to produce intrinsic factor which leads to vitamin B12 malabsorption.

29
Q

What forms the pyloric sphincter?

A

Smooth muscle forms the muscularis externa of the stomach and thickening of the circular layer creates the pyloric sphincter.

30
Q

What forms the visceral peritoneum?

A

Mesothelium covering the thin adventitia is the visceral peritoneum

31
Q

Why is projectile vomiting a symptom of pyloric stenosis?

A

Pyloric stenosis occurs when the ciruclar and to a lesser degree the longitudinal musculature of the stomach in region of the pylorus hypertrophies. It is characterized by extreme narrowing of the pyloric lumen and the passage of food is obstructed, resulting in severe projectile vomiting.

32
Q

What are plicae circulares?

A

They are macrscopic folds of the duodenal mucosa and submucosa

33
Q

What forms the microscopic finger-like villi

A

They are formed by projections of the mucosa from the macroscopic folds.

34
Q

What forms the intestinal crypts?

A

The simple columnar epithelium dips between the villi to form intestinal crypts.

35
Q

What do the plica circulares, villi and intestinal crypts do?

A

Plica circulares, villi, and intestinal crypts continue into the jejunum and ileum to increase the surface for nutrient absorption along the small intestine.

36
Q

What is special about the mucous glands of the duodenal submucosa?

A

It is filled with distinctive mucous glands of Brunner that deliver mucous with high bicarbonate ion concentrations into the duodenal lumen to buffer the acidic discharge from the pylorus.

37
Q

What constitutes the muscularis externa of the small intestine?

A

Two layers of SMOOTH muscle (just like the stomach!)

38
Q

What treatment effectively promotes healing of peptic ulcers?

A

Antibiotic treatment often promotes healing.

39
Q

What makes up the enteric nervous system?

A

It is made of MYENTERIC PLEXUS between the two layers of the muscularis externa and a SUBMUCOSAL PLEXUS between the mucosa and muscularis externa. It extends along the whole GI tract.

40
Q

What do the ENS plexus contain? What is the embryological derivation?

A

They contain visceral (parasympathetic) motor and sensory neurons which are derived from neural crest cells.

41
Q

How are peristaltic waves created along the GI tract? (Neurally speaking)

A

Local mechanical or chemical stimuli activate sensory neurons of the ENS which synaptically activate parasympathetic neurons of the myenteric plexus to induce serial contractions of the muscularis externa creating peristaltic waves along the GI tract

42
Q

What does activation of parasympathetic neurons of the submucosal plexus cause?

A

It stimulates secretion by glandular epithelial cells (chief and mucous cells) and activates entero-endocrine cells, which are diffusely scattered in the epithelium and produce >30 hormones.

43
Q

What forms the periarterial plexuses? What does it supply?

A

Postsynaptic sympathetic fibers and branches of the vagus nerve from the periarterial plexuses.
It supplies the foregut-derived GI tract.

44
Q

How do you inhibit/ accelerate the digestive process?

A

By synapsing with neurons of the ENS, SYMPATHETIC fibers INHIBIT.

By synapsing with neurons of the ENS, PARASYMPATHETIC fibers, accelerate.

45
Q

What artery courses within the splenorenal ligament?

A

Splenic artery courses within the ligament to reach the hilium of the spleen. The ligament serves as a mesentery.

46
Q

Where do short gastric arteries branch from? What do they supply?

A

They branch from the splenic artery before it enters the splenorenal ligament. They course within the gastrosplenic ligament to supply the fundus of the intraperitoneal stomach.

47
Q

What is the splenic pulp?

A

It is a dense meshwork of reticular fibers that is encompassed by projecting trabeculae from the dense connective tissue splenic capsule

48
Q

What is white pulp?

A

Splenic pulp that contains scattered lymphoid nodules. Collectively it is called white pulp

49
Q

What is red pulp?

A

It is an intervening meshwork of reticular fibers that is mainly filled with erythrocytes.

50
Q

What discharges RBCs and other formed elements of blood directly into red pulp?

A

Open-ended capillaries

51
Q

What is the course of RBCs and other formed elements of blood?

A

splenic artery (courses with trabeculae) –> small branches (enter the red pulp) –> open-ended capillaries –> venous sinusoids –> tributaries of the splenic vein (interweave through the red pulp)

52
Q

How do extravascular formed elements of the blood re-enter the bloodstream from the red pulp?

A

Endothelial cells of the sinusoids are separated by slit-like spaces and the elements (except aged RBCs that lose pliability) squeeze through the slits and re-enter the blood stream

53
Q

What cell is a permanent resident of the red pulp? What do they do?

A

Macrophages are permanent residents of the red pulp and the aged RBCs are removed from the red pulp via phagocytosis.

54
Q

What happens to blood-borne antigens?

A

There are lymphocytes in red pulp. Blood borne antigens are either selectively bound by B cells or phagocytized by resident macrophages.

55
Q

What forms the lymphoid nodules of white pulp?

A

proliferation of antigen-bound B cells

56
Q

How do clinical consequences of splenectomy in children differ from those in adults?

A

Splenectomy in adults has no clinical consequence, but in children it leads to increased occurrence and severity of illness!