Abdomen 1

Abdominal Wall Functions

• Provides strong, yet flexible support to the abdominal contents
• Contains and protects the viscera from injury
• Opposes or assists the diaphragm in maintaining or increasing intra-abdominal pressure
• Helps to eliminate gas, liquid, and solid waste products
• Moves the trunk and helps maintain posture

Innervation of the Abdominal Wall

• Dermatomes:
  • C4: Clavicle
  • C7:
  • T4: Nipple
  • T10: Umbilicus
  • L1: Groin
  • L5: Top of feet
• Innervation:
  • T7-T12/L1 supply the muscles and skin of the abdominal wall
  • Thoracoabdominal (T7-T11): muscles of anterolateral abdominal wall and overlying skin
  • Subcostal nerves (T12): muscles of anterolateral abdominal wall and overlying skin superior to iliac crest and inferior to umbilicus
  • Iliohypogastric (L1): skin overlying iliac crest, upper inguinal, and hypogastric regions; internal oblique and transversus abdominis

Vascularity of the Abdominal Wall

• Arteries:
  • Musculophrenic: internal thoracic artery; supplies abdominal wall of hypochondriac region, anterolateral wall, and diaphragm
  • Superior Epigastric: terminal branch of the internal thoracic artery; supplies the rectus abdominis and upper central part of the anterior abdominal wall
  • Inferior Epigastric: branch of the external iliac artery just above the inguinal ligament; supplies the lower central part of the anterior abdominal wall
  • Superficial Epigastric: branches off femoral artery; supplies subcutaneous tissue and skin over pubic and inferior umbilical region
  • Superficial Circumflex Iliac: branches off femoral artery; supplies superficial abdominal wall of inguinal region and adjacent anterior thigh
  • Deep Circumflex Iliac: branch of the external iliac artery; supplies lower lateral part of the abdominal wall
  • Posterior Intercostal Arteries (10th/11th)/Subcostal: branches of the descending thoracic aorta; supply the lateral part of the abdominal wall

Anatomy of the Groin

• Inguinal Ligament:
  • Formed by the external abdominal oblique aponeurosis and is continuous with the fascia lata of the thigh
  • Runs from the ASIS curving downward to the pubic tubercle of the pubic bone
• Symphysis Pubis:
  • Cartilaginous joint that lies in the midline between the bodies of the pubic bones
  • Felt as a solid structure beneath the skin in the midline of the anterior abdominal wall
• Pubic Crest:
  • Ridge of the superior surface of the pubic bones medial to the pubic tubercle
• Inguinal Canal:
  • Tubular structure that runs inferomedially and contains the spermatic cord in males and the round ligament in females
  • Formed during development as the gonads relocate
  • Superficial (External) Inguinal Ring:
    • Triangular aperture in the aponeurosis of the external oblique muscle situated above and medial to the pubic tubercle
  • Deep (Internal) Inguinal Ring:
    • Internal opening of the inguinal canal 1 cm above the midpoint of the inguinal ligament

Hernias

• Direct Inguinal Hernias:
  • Usually occur in men over 40
  • Rare in women
  • Above the inguinal ligament
  • Directly behind and through the external inguinal ring
  • Rarely enters the scrotum
  • Hernia pushes the side of the examiner's finger in the inguinal canal
• Indirect Inguinal Hernias:
  • Most common type
  • All ages
  • 30% bilateral
  • Swelling above the inguinal ligament
  • Abdominal contents through the internal inguinal ring often into the scrotum
  • Hernia comes down the inguinal canal and touches the examiner's fingertip
• Femoral Hernias:
  • Least common of all the groin hernias
  • More common in women
  • Passes below the inguinal ligament
  • Never enters the scrotum
  • Inguinal canal is empty
• Spigelian Hernias:
  • A hernia through the Spigelian fascia, which is the aponeurotic layer between the rectus abdominis muscle medially, and the semilunar line laterally

Surgical Incisions

• Median/Midline
• Paramedian
• Gridiron
• Pfannenstiel
• Transverse
• Subcostal

Peritoneum

• The abdominal cavity is lined with a protective membrane termed the peritoneum
• The abdominal wall is covered by the parietal peritoneum
• The viscera are covered by the visceral peritoneum
• The kidneys are located in the abdominal cavity behind the peritoneum, in the retroperitoneum
• Two continuous layers of serous membrane:
  • Parietal – lines the surface of the abdominopelvic wall
  • Visceral – invests organs
• Intraperitoneal organs are almost completely covered with visceral peritoneum
• Every organ must have an area that is not covered with visceral peritoneum to allow entrance/exit of neurovascular structures
• Bare area
• Extraperitoneal, retroperitoneal, and subperitoneal organs are only partially covered

Subdivisions of the Peritoneal Cavity

• The peritoneal cavity is divided into a greater sac and an omental bursa:
  • Greater Sac:
    • Main/larger part of the peritoneal cavity
  • Omental Bursa (Lesser Sac):
    • Smaller part of the peritoneal cavity
    • Posterior to the stomach
    • Permits free movement of the stomach on adjacent structures
  • 2 Recesses:
    • Superior
    • Inferior
  • Greater and Lesser Sac communicate through the Omental Foramen (Epiploic Foramen/Foramen of Winslow)

Posterior Abdominal Wall

• From deep to superficial:
  • 5 Lumbar vertebrae
  • Posterior abdominal wall muscles
  • Psoas, quadratus lumborum, iliacus, transversus abdominis, obliques
  • Lumbar plexus
  • Fascias
  • Diaphragm
  • Fat, nerves, vessels, and lymph nodes

Retroperitoneum

• The retroperitoneal space (retroperitoneum) is the anatomical space behind the peritoneum
• Has no delineating anatomic structures
• Organs are retroperitoneal if they have peritoneum on their anterior side only
• Structures that are not suspended by mesentery in the abdominal cavity and that lie between the parietal peritoneum and abdominal wall are classified as retroperitoneal### Abdominal Wall
• Xiphoid process: a thin, cartilaginous extension of the sternum, easily palpated in the depression where the costal margins meet in the upper part of the anterior abdominal wall
• Epigastric fossa: a small depression located in the upper-most midline abdomen in the infraxiphoid area
• Costal margin: the curved lower margin of the thoracic wall formed by the cartilage of the 7th, 8th, 9th, and 10th ribs anteriorly and the cartilage of the 11th and 12th ribs posteriorly

Linea Alba and Umbilicus

• Linea alba: a fibrous band extending from the symphysis pubis (inferiorly) to the xiphoid process (superiorly) and lies in the midline
• Fusion of the aponeuroses of the muscles of the anterior abdominal wall, represented on the surface by a slight median groove – “rhaphe” or suture/seam
• Umbilicus: lies in the linea alba and is inconstant in position, puckered scar at the site of attachment of the umbilical cord in the fetus, located at L4, where the aorta bifurcates at vertebral level L4

Diaphragm

• Dome-shaped, musculotendinous partition separating the thoracic and abdominal cavities
• Made up of central tendon with muscular attachments to the xiphoid process, inferior thoracic cage, and superior lumbar vertebrae
• Right dome is typically higher than the left
• Apertures:
  • Caval opening: for IVC
  • Esophageal hiatus: oval aperture for esophagus
  • Aortic hiatus: posterior to the diaphragm, not piercing it

Anterolateral Abdominal Wall

• Composed of:
  • Skin (epidermis and dermis)
  • Subcutaneous tissue
  • Fascias (Camper's, Scarpa's, and Colles')
  • Muscles (3 flat and 2 vertical)
  • Endoabdominal fascia (transversalis fascia lines organs)

Muscles of the Abdominal Wall

• 3 flat muscles:
  • External oblique: most superficial, largest, runs inferomedially
  • Internal oblique: intermediate, runs superomedially
  • Transversus abdominis: deepest, runs horizontally and inward
• 2 vertical muscles:
  • Rectus abdominis: long, broad, strap-like, mostly enclosed in the rectus sheath
  • Pyramidalis: small, triangular, lies in the rectus sheath anterior to the inferior rectus abdominis, ends in linea alba, and tenses it (present in 80% of population)

Rectus Sheath

• Formed by the interweaving aponeuroses of the flat muscles
• Contains: rectus abdominis, pyramidalis, superior and inferior epigastric arteries, lymphatic vessels, and portions of spinal nerves (T7-T12)

Functions of the Abdominal Wall

• Provides strong, yet flexible support
• Contains viscera and protects from injury
• Opposes or assists diaphragm in maintaining or increasing intra-abdominal pressure
• Helps to eliminate gas, liquid, and solid waste

Innervation of the Abdominal Wall

• Dermatomes:
  • C4 = Clavicle
  • C7 = &%#.
  • T4 = Nipple
  • T10 = Umbilicus
  • L1 = Groin
  • L5 = Top of feet
• Thoracoabdominal (T7-T11) and subcostal nerves (T12) supply the muscles and skin of the abdominal wall
• Iliohypogastric (L1) supplies skin overlying iliac crest, upper inguinal and hypogastric regions; internal oblique and transversus abdominis

Vascular Supply of the Abdominal Wall

• Arteries:
  • Musculophrenic
  • Superior epigastric
  • Inferior epigastric
  • Superficial epigastric
  • Superficial circumflex iliac
  • Deep circumflex iliac
  • Posterior intercostal arteries (10th/11th) and subcostal
• Veins:
  • Musculophrenic
  • Superior epigastric
  • Inferior epigastric
  • Superficial epigastric
  • Superficial circumflex iliac
  • Deep circumflex iliac

Anastomosis of Epigastric Arteries

• Crucial for blood supply to the abdominal wall
• Superior epigastric arteries anastomose with inferior epigastric arteries, forming a continuous channel### Peritoneal Ligaments

• Double layer of peritoneum that connects an organ with another organ or to the abdominal wall • Examples: Falciform ligament (connects liver to anterior abdominal wall), Broad ligament of the uterus (connects uterus, fallopian tubes, and ovaries to the pelvis)

Omentum

• A large apron-like fold of visceral peritoneum that hangs down from the greater curvature of the stomach • Passes in front of the small intestines and reflects on itself to ascend to the transverse colon • Functions: Fat deposition, immune contribution, macrophage collections, infection and wound isolation ("policeman of the abdomen")

Greater Omentum

• A broad, double-layered sheet of peritoneum passing from the stomach to another abdominal organ • Connects greater curvature of stomach to another viscus • Composed of 3 parts: Gastrocolic ligament, Gastrosplenic ligament, and Gastrophrenic ligament

Lesser Omentum

• Located behind the stomach • Connects lesser curvature of stomach to another viscus • Composed of 2 parts: Hepatogastric ligament and Hepatoduodenal ligament

Subdivisions of the Peritoneal Cavity

• The peritoneal cavity is divided into a greater sac and an omental bursa • Greater sac: Main/larger part of the peritoneal cavity • Omental bursa: Smaller part of peritoneal cavity, also known as the "lesser sac" • Communicates with the greater sac through the omental foramen (also known as the epiploic foramen/foramen of Winslow)

Posterior Abdominal Wall

• Composed of: 5 lumbar vertebrae, posterior abdominal wall muscles, lumbar plexus, fascias, diaphragm, fat, nerves, vessels, and lymph nodes • Retroperitoneum: The retroperitoneal space is the anatomical space behind the peritoneum • Retroperitoneal structures: A BAD PUCKER: Aorta, Bladder, Adrenal glands, Duodenum, Pancreas, Ureters, Uterus, Esophagus, Rectum, and Kidneys

Surface Anatomy of the Abdomen

• Xiphoid process: Thin cartilaginous extension of the sternum • Linea alba: Fibrous band that extends from the symphysis pubis to the xiphoid process • Umbilicus: Lies in the linea alba, and is inconstant in position • Linea semilunaris: Lateral edge of the rectus abdominis muscles • Iliac crest: May be felt along its entire length and ends anteriorly at the Anterior Superior Iliac Spine (ASIS)

Subdivisions of the Abdomen

• The abdomen can be divided into 4 quadrants or 9 regions • 4 Quadrants: RUQ, LUQ, RLQ, LLQ • 9 Regions: Right and left hypochondriac, right and left lumbar, right and left inguinal, epigastric, umbilical, and pubic/hypogastric regions