Gastroduodenal Diseases

10 Gastroduodenal Diseases



Anatomy of the Stomach and Duodenum



image

Stomach in Situ



Parts of the Stomach



• Cardia(c) portion joins the abdominal esophagus.

• Fundus: uppermost curvature to the left of the cardia

• Greater curvature, lesser curvature, inferior and superior borders (respectively) of the voluminous body of the stomach

• Pyloric region
image Angular incisure (notch): distal end of the lesser curvature and start of the antrum

image Antrum: entryway to the pyloric canal, very muscular and peristaltic

image Pylorus: thickened circular muscle layer

• Rugae: folds in the mucosal surface of the relaxed stomach


Functional Anatomy and Motility



• Receptive relaxation and accommodation occur in the proximal 1/3 of the stomach, with swallowing and entry of food.

• True peristalsis occurs in the distal 2/3, with waves of contraction driving the contents back and forth between the body and antrum (trituration).

• Small amounts of triturated stomach contents pass through the pylorus with successive peristaltic waves.

• Myoelectric pacemaker for peristalsis is located high on greater curvature.


Gastric Microscopic Anatomy



Mucosa



• Epithelium
image Mucus-secreting cardia glands

image Oxyntic glands in the fundus and body
image Chief cells secrete pepsinogen.

image Parietal cells secrete H+ and intrinsic factor.

image Antrum and pylorus glands
image Both secrete HCO3 and mucus.

image G cells release gastrin.

image D cells secrete somatostatin, inhibiting release of gastrin and H+.

• Lamina propria: supportive, loose connective tissue deep to epithelium

• Muscularis mucosae: layer of smooth muscle at the boundary between mucosa and submucosa


Submucosa



• Strongest layer

• Connective tissue

• Meissner’s plexus (neuronal network)


Muscularis (Smooth Muscle)



• Auerbach’s plexus: myenteric neurons

• Inner circular muscle

• Outer longitudinal layer


Serosa



• Peritoneum

image

Duodenum in Situ



Anatomy of the Duodenum



• Most fixed portion of small bowel, surrounds head of the pancreas

• Superior (first) part
image Length ~5 cm, lies anterolateral to L1 body

image Overlain by liver and gallbladder

image Ampulla (cap)—first 2 cm—bears a mesentery, the hepatoduodenal ligament, part of the lesser omentum.

image Distal 3 cm retroperitoneal

• Descending (second) part
image Length 7-10 cm, lies along right sides of L1-L3 bodies

image Receives the outflow from bile and pancreatic ducts via the hepatopancreatic ampulla (Vater) through the greater duodenal papilla (Vater)

image Receives outflow from the accessory pancreatic duct through the lesser duodenal papilla

• Horizontal (third) part
image Length 6-8 cm, crosses the L3 body

image Lies posterior to the main trunk of the superior mesenteric artery

• Ascending (fourth) part
image Length ~5 cm, left of L3 to the upper border of L2

• Ligament of Treitz (suspensory ligament of the duodenum): marks duodenal-jejunal junction

• Plicae circulares: internal circular folds of the wall due to circular muscle, increase surface area per length


Duodenal Microscopic Anatomy



Mucosa



• Epithelium: enterocytes (absorptive), goblet cells, Paneth cells, enterochromaffin cells,

• Lamina propria: contains Peyer’s patches (lymphoid aggregations with B cells in germinal centers and T cell in interfollicular zones)

• Muscularis mucosa

• Water and nutrients absorbed across the mucosa


Submucosa



• Strongest layer

• Connective tissue

• Meissner’s plexus (parasympathetic ganglion cells and neuronal network)


Muscularis



• Inner circular muscle

• Outer longitudinal layer

• Auerbach’s plexus: myenteric neurons and parasympathetic ganglion cells


Serosa



• Peritoneum


Inner Surface



• Mucosal surface area specializations: microvilli, villi, plica circulares (valvulae conniventes)

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Aug 12, 2016 | Posted by in ANATOMY | Comments Off on Gastroduodenal Diseases

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