Describe briefly the layers of anterior abdominal wall. [TU 2070]
Layers of anterior abdominal wall?
Nine layers : skin, subcutaneous tissue, superficial fascia, external oblique muscle, internal oblique muscle, transversus abdominis muscle, transversalis fascia, preperitoneal adipose and areolar tissue, and peritoneum
Anatomy of external oblique muscle?
- Lower seven ribs and course in a superolateral to inferomedial direction. The most posterior of the fibers run vertically downward.
- - anterior half of the iliac crest
- - At the midclavicular line, the muscle fibers give rise to a flat, strong aponeurosis that passes anteriorly to the rectus sheath to insert medially into the linea alba
- - The lower portion of the external oblique aponeurosis is rolled posteriorly and superiorly on itself to form a groove on which the spermatic cord lies. This portion of the external oblique aponeurosis extends from the anterior superior iliac spine to the pubic tubercle and is termed the inguinal or Poupart ligament.
Anatomy of internal oblique muscle?
- from the iliopsoas fascia beneath the lateral half of the inguinal ligament, from the anterior two thirds of the iliac crest and lumbodorsal fascia.
- fibers course in a direction opposite to those of the external oblique, that is, inferolateral to superomedial.
- - The uppermost fibers insert into the lower five ribs and their cartilages.
- - The central fibers form an aponeurosis at the semilunar line, which, above the semicircular line (of Douglas), is divided into anterior and posterior lamellae that envelop the rectus abdominis muscle. Below the semicircular line, the aponeurosis of the internal oblique muscle courses anteriorly to the rectus abdominis muscle as part of the anterior rectus sheath.
- - The lowermost fibers of the internal oblique muscle pursue an inferomedial course, paralleling that of the spermatic cord, to insert between the symphysis pubis and pubic tubercle. Some of the lower muscle fascicles accompany the spermatic cord into the scrotum as the cremasteric muscle.
Anatomy of transversus abdominis?
- The transversus abdominis muscle is the smallest of the muscles of the anterolateral abdominal wall.
- Origin - from the lower six costal cartilages, spines of the lumbar vertebrae, iliac crest, and iliopsoas fascia beneath the lateral third of the inguinal ligament.
- Course - The fibers course transversely to give rise to a flat aponeurotic sheet that passes posterior to the rectus abdominis muscle above the semicircular line and anterior to the muscle below it
- The inferior most fibers of the transversus abdominis originating from the iliopsoas fascia pass inferomedially along with the lower fibers of the internal oblique muscle
Rectus muscle anatomy?
- Origin - anterior surfaces of the fifth, sixth, and seventh costal cartilages and the xiphoid process
- Insertion - pubic crest and pubic symphysis
Contents of preperitoneal space?
- • Inferior epigastric artery and vein - branches of external iliac vessels
- • Medial umbilical ligaments, which are the vestiges of the fetal umbilical arteries
- • Median umbilical ligament, which is a midline fibrous remnant of the fetal allantoic stalk or urachus
- • Falciform ligament of the liver, extending from the umbilicus to the liver
Arterial supply of anterior abdominal wall?
- Last six intercostals and four lumbar arteries
- Superior and inferior epigastric arteries
- Deep circumflex iliac arteries
Nerve innervation of anterior abdominal wall?
- Thoracic nerves 7 to 12 - enter a plane between the internal oblique muscle and the transversus abdominis.
- 10th thoracic nerve reaches the skin at the level of the umbilicus
- 12th thoracic nerve innervates the skin of the hypogastrium
Important nerves in inguinal region?
The ilioinguinal and iliohypogastric nerves often arise in common from the anterior rami of the 12th thoracic and first lumbar nerve. The iliohypogastric and ilioinguinal nerves lie beneath the internal oblique muscle to a point just medial and superior to the anterior superior iliac spine, where they penetrate the internal oblique muscle and course beneath the external oblique aponeurosis
Iliohypogastric - The main trunk of the iliohypogastric nerve runs on the anterior surface of the internal oblique muscle and aponeurosis medial and superior to the internal ring. It provides sensory innervation to the anterior abdominal wall in the hypogastrium.
Ilioinguinal nerve courses parallel to the iliohypogastric nerve but closer to the inguinal ligament than the iliohypogastric nerve. Unlike the iliohypogastric nerve, the ilioinguinal nerve courses with the spermatic cord to emerge from the external inguinal ring, with its terminal branches providing sensory innervation to the skin of the inguinal region and scrotum or labium.
Genital branch of the genitofemoral nerve The genitofemoral nerve usually arises from the L2 or L1-L2 nerve roots. It divides into genital and femoral branches on the anterior surface of the psoas muscle. The genital branch enters the inguinal canal through the deep ring, whereas the femoral branch enters the femoral sheath lateral to the artery. Genital branch of the genitofemoral nerve nerve lies on the iliopubic tract and accompanies the cremaster vessels to form a neurovascular bundle.
Classification of umbilical hernia?
- Omphalocele and gastroschisis
- Infantile umbilical hernia, and
- Acquired umbilical hernia
What is omphalocele?
- Also called as exomphalos.
- An omphalocele is a funnel-shaped defect in the central abdomen through which the viscera protrude into the base of the umbilical cord.
- It is caused by failure of the abdominal wall musculature to unite in the midline during fetal development.
- There is no skin covering these defects, only peritoneum and, more superficially, amnion.
- 1. Exomphalos minor where the opening is less than 4cm and only contains the intestine,
- 2. Exomphalos major where the opening is greater than 4cm and/or with the liver inside the cord.
- - These small defect may be closed spontaneously soon after birth.
- - Various surgical techniques for surgical closure include - primary closure, skin flap closure or staged repair.
What is Gastroschisis?
- Gastroschisis is congenital defect of the abdominal wall in which the umbilical membrane has ruptured in utero, allowing the intestine to herniate outside the abdominal cavity.
- The defect is almost always to the right of the umbilical cord.
- The intestine is not covered with skin or amnion.
What is infantile umbilical hernia?
- The infantile umbilical hernia appears within a few days or weeks after the stump of the umbilical cord has sloughed.
- It is caused by a weakness in the adhesion between the scarred remnants of the umbilical cord and umbilical ring.
- In contrast to omphalocele, the infantile umbilical hernia is covered by skin.
- They are easily reducible and become prominent when the infant cries.
- Most of these hernias resolve within the first 24 months of life, and complications such as strangulation are rare
- Operative repair is indicated for those children in whom the hernia persists beyond the age of 3 or 4 years
Acquired umbilical hernia?
- In this condition, an umbilical hernia develops at a time remote from closure of the umbilical ring.
- This hernia occurs most commonly at the upper margin of the umbilicus and results from weakening of the cicatricial tissue that normally closes the umbilical ring.
- This weakening can be caused by excessive stretching of the abdominal wall, which may occur with pregnancy, vigorous labor, or ascites.
- In contrast to infantile umbilical hernias, acquired umbilical hernias do not spontaneously resolv but gradually increase in size. The dense fibrous ring at the neck of this hernia makes strangulation of herniated intestine or omentum an important complication
Management of acquired umbilical hernia?
- Transverse incision is made over the swelling.
- Small defects - closed primarily (anatomical repair)
- Defects > 3 cm - closed using prosthetic mesh
Zones of retroperitoneal hematoma?
- Zone 1 (central) - esophageal hiatus to the sacral promontory.
- Zone 2 (lateral) - lateral diaphragm to the iliac crest.
- Zone 3 (pelvic) - confined to the retroperitoneal space of the pelvis
The judgment of whether and when to explore the retroperitoneal hematoma is guided by the mechanism of injury (blunt or penetrating) and the location of the RPH.
- RPH localized to the upper central area (Zone 1) after penetrating trauma implies injury to the great vessels and always requires urgent surgical exploration.
- RPH in other zones should be evaluated by CT and/or angiography; ongoing hemorrhage may respond to therapeutic embolization.