Gastroduodenal Diseases

Published on 16/04/2015 by admin

Filed under Surgery

Last modified 16/04/2015

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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

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