The abdominal wall Flashcards
Where is the inguinal canal?
Between ASIS and pubic tubercle
What 2 horizontal lines form the 9 regions of the abdomen? What are the 9 regions?
Transpyloric (L1)
Transtubercular (L5)
Right hypochondriac Epigastric Left hypochondriac Right lumbar Umbilical Left lumbar Right iliac Hypogastric/pubic Left iliac
What are the five (bilaterally paired) muscles in the anterolateral abdominal wall?
Three “flat”/lateral muscles:
- Internal oblique
- External oblique
- Transversus abdominus
Two vertical muscles:
- Rectus abdominus
- Pyramidalis
What is linea alba?
Midline of abdominal muscles aponeurosis from xiphoid process to the pubic symphysis
Formed by aponeurosis of external oblique, internal oblique, transversus abdominis
What is linea semilunaris?
The curved tendinous structure that runs on the lateral edges of rectus abdominis. The tendinous intersections of rectus abdominis unite there.
External obliques
Origin: External surfaces of 5th–12th ribs
Insertion: Linea alba, pubic tubercle, and anterior half of iliac crest
Function: Rotate the trunk, flex spine
Internal obliques
Origin: Thoracolumbar fascia, anterior two-thirds of the iliac crest, and lateral half of inguinal ligament
Insertion: Inferior borders of 10th–12th ribs, linea alba, and pecten pubis via conjoint tendon
Function: Compress and support abdominal viscera, flex and rotate the trunk
Transversus abdominis
Origin: Internal surfaces of 7th–12th costal cartilages, thoracolumbar fascia, iliac crest, and lateral third of inguinal ligament
Insertion: Linea alba with aponeurosis of internal oblique, pubic crest, and pecten pubis via conjoint tendon
Function: Compresses and supports abdominal viscera
Rectus abdominus
Origin: Pubic symphysis and pubic crest
Insertion: Xiphoid process and 5th–7th costal cartilages
Function: Flexes trunk (lumbar vertebrae) and compresses abdominal viscera, stabilizes and controls tilt of pelvis (antilordosis)
Pyramidalis muscle
Connects from line alba to the anterior surface of the pubis and the anterior pubic ligament
Function: tenses linea alba
When present, surgeons use the attachment of the pyramidalis to the linea alba as a landmark for an accurate median abdominal incision
What are the anterolateral abdominal wall layers?
Skin Camper’s fascia (superficial subcutaneous fat) Scarpa’s fascia (deep membranous layer) Superficial investing fascia External oblique Intermediate investing fascia Internal oblique Deep investing fascia Transversus abdominis Endoabdominal (transversalis) fascia Extraperitoneal
What is the Rectus sheath?
Formed from the aponeurosis of the internal and external obliques and the transverses abdominus.
Contents: rectus abdominis and pyramidalis muscles, superior and inferior epigastric arteries and veins, lymphatic vessels, termination parts of lower five intercostal nerves (T7- T11), and the termination of the 12th thoracic nerve (T12)
Arcuate line (between umbilicus and pubic symphysis) = where the structure of the rectus sheath changes
What are the contents of the rectus sheath?
rectus abdominis and pyramidalis muscles, superior and inferior epigastric arteries and veins, lymphatic vessels, termination parts of lower five intercostal nerves (T7- T11), and the termination of the 12th thoracic nerve (T12)
Why is the arcuate line important?
ABOVE arcuate line, rectus sheath splits deep and superficial to the rectus abdominis has anterior and posterior wall
BELOW the arcuate line, rectus sheath goes superficial to the rectus abdominis only has anterior wall, no posterior
What is the innervation of the anterior abdominal wall?
T6-L1
Thoracoabdominal nerve - anterior cutaneous branch and lateral cutaneous branch (ventral rami T6-T12)
L1: ilioinguinal and iliohypogastric
What are umbilical folds?
folds of parietal peritoneum
We have 5:
- A single midline median umbilical fold
- Bilateral medial umbilical folds
- Bilateral lateral umbilical folds
What is the arterial supply of the anterior abdominal wall?
There is a dual blood supply to the anterior abdominal wall:
- Superior epigastric artery anastomoses with inferior epigastric artery (from external iliac artery)
- Key: superior epigastric artery is continuation of the anterior thoracic artery
The flat/lateral muscles:
- Dual supply
- Musculophrenic from anterior thoracic artery anastomoses with circumflex artery from external iliac artery
What is the venous drainage of the anterior abdominal wall?
Superficial veins:
- Thoracoepigastric vein drains into axillary vein
- Superficial inferior epigastric vein drains into femoral vein
Deep Veins:
- Superior epigastric vein drains into subclavian vein
- Inferior epigastric vein drains into femoral vein
What is Caput medusae?
Portal hypertension (following damage to the liver) can result in dilated abdominal veins surrounding the umbilicus:
- Blood backs up as it cannot pass through the liver so it tries to find an alternative route.
- The blood backs up into the external iliac vein and femoral vein and ascends up to the thoracoepigastric veins to axillary veins.
- Causes dilation of veins
What is the lymphatic drainage?
Superior to umbilicus drains: to axillary lymph nodes
Inferior to umbilicus drains: to superficial inguinal and superficial subinguinal lymph nodes
What is the inguinal canal?
The inguinal canal is an oblique opening in the anterior abdominal wall through which the spermatic cord can pass in males.
The testes like to be cool, so are kept outside the abdominal cavity
Spermatic cord: contains blood supply, nerves, muscles, and ductus deferens. Life support for the testes
Inferior epigastric artery and vein pass medial to the deep inguinal ring
Contents of the inguinal canal in females: round ligament, genital branch of the genitofemoral nerve, and the ilioinguinal nerve
What are the components of the inguinal canal?
Anterior wall – aponeurosis of the external oblique, reinforced by the internal oblique muscle laterally.
Posterior wall – transversalis fascia.
Roof – transversalis fascia, internal oblique, and transversus abdominis
Floor – inguinal ligament (a ‘rolled up’ portion of the external oblique aponeurosis), thickened medially by the lacunar ligament
What are the borders of the Hesselbach’s triangle?
Medial – lateral border of the rectus abdominis muscle.
Lateral – inferior epigastric vessels.
Inferior – inguinal ligament.
What are direct and indirect hernias?
Indirect inguinal hernia (more common in children, incomplete closure of canal):
- Through inguinal canal
- Lateral to the inferior epigastric vessels
Direct inguinal hernia:
- Through body wall
- Medial to inferior epigastric vessels
What are the Surgical Approaches to the Abdomen?
- Median/Midline incision: cuts through lines alba, easily avoids muscle, nerves, and blood vessels. Lower median incisions (below umbicus) sometimes used for reaching female pelvic viscera.
- Paramedian incisions: cuts through rectus sheath. May be favoured over median incision because the linea alba has poor blood supply and can have issues with healing
- Muscle-splitting incision: used for appendectomy, goes through external and internal obliques and transverses abdomens
- McBurney incision: at McBurney’s point- one third of the way from ASIS to umbilicus. Location of the base of the appendix, old-fashioned incision site for appendectomy
- Suprapubic (Pfannenstiel or Kerr) incision: made at pubic hairline, used for gynaecological and obstetrical procedures, such as cesarean section or removal of tubal pregnancy
- Subcostal incision: for gallbladder and biliary duct surgery
Blood supply and innervation to the abdominal wall muscles
The anterior and lateral muscles innervation:
- Thoracoabdominal nerve (T6-T12)
- Ilioinguinal and iliohypogastric
Blood supply of anterior abdominal muscles:
Superior epigastric and inferior epigastric –> anastomose
Blood supply of lateral abdominal muscles:
Musculophrenic branch of internal thoracic artery and circumflex branch of external iliac –> anastomosis
Venous drainage:
Superficial:
-Thoracoepigastric vein drains to subclavian vein
-Superficial inferior epigastric vein drains to femoral vein
Deep Veins:
- Superior epigastric vein drains into subclavian vein
- Inferior epigastric vein drains into femoral vein
