Study Notes on the Abdomen and Abdominal Viscera

Be able to describe the components of the peritoneum.
Review the overview of the abdomen and the abdominal viscera.
Describe the esophagus and recognize its anatomical features, including three main constrictions of the esophagus.
Recognize and describe the anatomy of the external and internal structures of the stomach.
Describe the anatomy of the small intestine, including naming and describing its parts.
Break down and describe the various anatomical parts of the duodenum, and identify them in images, cadavers, and wet specimens.
Understand the locations and anatomical differences between the jejunum and ileum.
Explain the pathologies associated with hiatal hernias.

Largest serous membrane of the body.
Divided into two main types:
- Parietal Peritoneum: Lines the abdominal wall.
- Visceral Peritoneum (Serosa): Covers the abdominal organs.
Retroperitoneal Organs:
- Portions of the diaphragm
- Head of the pancreas
- Kidneys
- Suprarenal glands

The abdomen contains the majority of the alimentary system, including:
- Terminal part of the esophagus
- Stomach
- Intestines
- Spleen
- Pancreas
- Liver
- Gallbladder
- Kidneys
- Suprarenal glands
Notable anatomical features:
- The liver, stomach, and spleen fill the domes of the diaphragm and bulge into the thoracic cage, providing them protection from the lower thoracic cage.
- The falciform ligament attaches continuously to the anterior abdominal wall down to the umbilicus, dividing the liver into right and left lobes.
- The greater omentum conceals almost all parts of the intestines when in its typical position.
- The gallbladder projects inferior to the border of the liver.

The esophagus follows the curve of the vertebral column and descends through the neck and mediastinum.
Composed of layers of muscle:
- Superior third: Voluntary striated muscle.
- Middle third: Both voluntary striated and smooth muscle.
- Inferior third: Smooth muscle.
Anatomical passage:
- Passes through the esophageal hiatus in the muscular right crus of the diaphragm at the level of the T10 vertebra.
- Terminates at the stomach’s cardial orifice, positioned to the left of the midline at the level of the 7th left costal cartilage and the T11 vertebra.
Esophagus characteristics:
- Muscular tube approximately 25 cm (10 inches) long with an average diameter of 2 cm.
- Responsible for conveying food from the pharynx to the stomach.
Constrictions of the Esophagus:
- Cervical Constriction:
- Location: At the pharyngo-esophageal junction, approximately 15 cm from the incisor teeth.
- Formed by the cricopharyngeal muscle.
- Thoracic (Broncho-Aortic) Constriction:
- Compound constriction at two points:
  - Crossed by the arch of the aorta at 22.5 cm from the incisor teeth.
  - Crossed by the left main bronchus at 27.5 cm from the incisor teeth.
- Diaphragmatic Constriction:
- Location: Passes through the esophageal hiatus, approximately 40 cm from the incisor teeth.

The stomach is the expanded part of the digestive tract between the esophagus and the small intestine.
Specialized for:
- Accumulation of ingested food.
- Chemical and mechanical preparation for digestion and passage into the duodenum.
- Acts as food blender and reservoir, crucial for enzymatic digestion.
- Gastric juice converts food into a semi-liquid mixture called chyme.
Capacity:
- An empty stomach has a caliber just slightly larger than that of the large intestine but can expand significantly to hold 2-3 liters of food.
Variability in size, shape, and position due to factors like body type (habitus), diaphragmatic movements, and stomach contents.

Cardia: Surrounds the cardial orifice, the superior opening (inlet) into the stomach.
Fundus: Dilated superior part, related to the left dome of the diaphragm.
- Limited inferiorly by the horizontal plane of the cardial orifice.
- Cardial notch located between the esophagus and fundus; may be dilated by gas, fluid, and food.
Body: Major part of the stomach between the fundus and pyloric antrum.
Pyloric Part: Funnel-shaped outflow region containing:
- Pyloric Antrum: Wider part leading into the pyloric canal.
- Pylorus: Sphincteric region of the pyloric part, controlling discharge through the pyloric orifice into the duodenum.
Curvatures of the Stomach:
- Lesser Curvature: Concave right border; with an angular incisure indicating junction of body and pyloric part.
- Greater Curvature: Convex left border; curves from the junction of the 5th intercostal space to reach the pyloric antrum.

Comprises the duodenum, jejunum, and ileum; primary site for nutrient absorption.
Extends from the pylorus to the ileocecal junction where it joins the cecum (the first part of the large intestine).
Duodenum Features:
- Superior Part: Short (approximately 5 cm), lies anterolateral to L1 vertebra.
- Descending Part: Long (7-10 cm), descends along right side of L1-L3 vertebrae.
- Inferior Part: 6-8 cm long, crosses L3 vertebra.
- Ascending Part: Short (5 cm), rises superiorly to the superior border of L2 vertebra.

Jejunum: Second part; begins at the duodenojejunal flexure where the gastrointestinal tract resumes an intraperitoneal course.
Ileum: Third part; ends at the ileocecal junction, where it meets the cecum.
Combined length of jejunum and ileum: 6-7m, with jejunum constituting approximately two-fifths and ileum about three-fifths of the intraperitoneal section of the small intestine.

Definition: Protrusion of part of the stomach into the mediastinum through the esophageal hiatus of the diaphragm.
Common in individuals over middle age due to muscular weakening of the diaphragm and widening of the esophageal hiatus.
Types of hiatal hernia:
- Paraesophageal Hiatal Hernia:
- Cardia remains in its normal position.
- A pouch of peritoneum extends through the esophageal hiatus anterior to the esophagus, usually with no regurgitation of gastric contents.
- Sliding Hiatal Hernia:
- Abdominal esophagus, cardia, and parts of the stomach slide superiorly through the esophageal hiatus into the thorax, particularly when lying down or bending.
- Possible regurgitation of stomach contents due to weak clamping action of the diaphragm on the lower esophageal sphincter.