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Gastrointestinal System Anatomy

• The gastrointestinal (GI) system is a long, continuous tube beginning at the mouth and ending at the anus.
• The GI system is responsible for the digestion, absorption and elimination of food.
• The study covers the anatomy of the GI tract's major organs.

Learning Outcomes

• Students will be able to identify abdominal quadrants and regions.
• Students will be able to describe different abdominal incisions.
• Students will be able to name and locate abdominal organs.
• Students will be able to define the peritoneum and its functions.

Abdominal Quadrants and Regions

• Nine-region organizational pattern is used for description. Subcostal and midclavicular planes are used.
• Four quadrants (RUQ, LUQ, RLQ, LLQ) are also used
• Organs are located in specific regions of the abdomen. For example: liver and gallbladder in the right upper quadrant, stomach and spleen in the left upper quadrant, cecum and appendix in the right lower quadrant, and the descending and sigmoid colon in the left lower quadrant.

Abdominal Incisions

• Median or Midline Incisions: extend along linea alba from xiphoid process to pubic symphysis.
• Paramedian Incisions: located laterally to the median plane, extend from the costal margin to pubic hairline. After incision through rectus sheath, muscle freed to prevent vessel/nerve damage
• Different types of incisions are described, each with specific advantages and disadvantages in surgery.

Abdominal Organs

• Specific organ locations are identified within the quadrants/regions. Examples include:
  • Liver, in the right upper quadrant, primarily.
  • Stomach, within the epigastric, left hypochondriac and into the umbilical region of the abdomen.
  • Spleen, in the left upper, near the diaphragm's area.
  • Cecum and appendix in the right lower.
  • Descending and sigmoid colon in the left lower.

Peritoneum and its Functions

• The peritoneum is a large serous membrane lining the abdominal cavity.
  • Externally lined by fibrous tissue providing strength.
  • Internally mesothelial cells line it.
  • It is in the form of a closed sac, invaginated by viscera.
• Divided into outer (parietal) and inner (visceral) layers.
• Folds of peritoneum suspend the viscera, and also form passageways for nerves, vessels, and lymphatics.
• Structures are identified, such as the lesser omentum, the greater omentum, and mesentery.

Abdominal Esophagus

• Emerges through the diaphragm's right crus, typically at the level of vertebra T10.
• Passes through esophageal hiatus.
• Ends at the cardiac end of the stomach, approximately 2.5cm to the left of the median plane, at the level of T11.

Stomach

• The stomach is the most dilated part of the gastrointestinal tract.
• It's located in the epigastric, left hypochondriac and umbilical regions, with moderate gastric content.
• It has two orifices, cardiac and pyloric.
• Two curvatures—lesser and greater.
• Three subdivisions—fundus, body, and pylorus.

Small Intestine

• The small intestine is the longest part of the GI tract.
• It extends from the pyloric orifice of the stomach to the ileocecal junction.
• It comprises three parts: duodenum (proximal, fixed), jejunum, and ileum (distal, mobile). Total length approximately 6.5 meters.

Duodenum

• Shaped like a “C”, positioned adjacent to the head of the pancreas.
• Located above the umbilicus.

Jejunum

• The proximal two-fifths of the small intestine.
• Primarily located in the left upper quadrant.

Ileum

• The distal three-fifths of the small intestine.
• Primarily located in the right lower quadrant.

Large Intestine

• It originates from the ileum, extending to the anus.
• It stretches about 1.5 m in length.
• Contains components such as the cecum, appendix, colon, rectum, and anal canal.

Liver

• The largest visceral organ within the body.
• Predominantly situated in the right hypochondrium and epigastric region; extends into the left hypochondrium.

Pancreas

• Mostly posterior to the stomach.
• Extends across the posterior wall of the abdomen from the duodenum (on the right) to the spleen (on the left).
• Consists of head, uncinate process, neck, body, and tail.

Spleen

• Near the diaphragm in the area of ribs IX and X on the left side (left hypochondrium)

Peritoneal Folds and Ligaments

• Various peritoneal folds and ligaments within the peritoneal cavity.
  • Examples include mesentery, mesocolon, omenta (greater and lesser), and other folds involved in suspending and connecting the organs.
• Peritoneal folds allow some organs to move and others to be directly anchored to the abdominal wall.
• Ligaments connect some organs to other structures or hold them in place.

Greater Omentum

• A large peritoneal fold that hangs from the greater curvature of the stomach.
• Composed of four fused layers forming a thin membrane containing fat, small arteries, and veins.
• Also called "policeman of the abdomen" due to its role in limiting infection spread.

Lesser Omentum

• A fold connecting the lesser curvature of the stomach and the proximal part of the duodenum to the liver.
• Contains the hepato-duodenal ligament.
• Contains a free margin behind which lies the epiploic foramen, connecting the greater and lesser sacs.

Functions of Greater Omentum

• Fat storage
• Protects the peritoneal cavity.
• Limits infection spread through the movement of macrophages.

Test your knowledge on the anatomy of the abdominal cavity, including questions on the stomach, small intestine, and related structures. Explore the functions and features of key anatomical components such as the greater omentum and its role in infection. This quiz is perfect for students studying human anatomy.