Anatomy - Umbilical hernia, direct suture

1. Anterior Abdominal Muscles

M. rectus abdominis: straight abdominal muscle within the rectus sheath with 3-4 tendinous intersections (Intersectiones tendineae), which are fused with the anterior layer of the rectus sheath.
M. pyramidalis: originates at the superior pubic ramus and radiates into the linea alba, located ventrally to the M. rectus abdominis in its own sheath in the anterior layer of the rectus sheath.

2. Layer Structure of the Anterior Abdominal Wall

Rectus sheath: envelops the M. rectus abdominis; above the midpoint between the navel and symphysis, a distinction is made between an anterior and a posterior layer; the posterior layer ends here in the form of the linea arcuata; above this linea, the M. obliquus externus abdominis radiates into the anterior layer of the rectus sheath, the M. obliquus internus abdominis into both the anterior and posterior layers, and the M. transversus abdominis into the posterior layer.
Linea semilunaris: transition zone between the aponeuroses of the lateral abdominal muscles and the lateral edge of the rectus sheath.
Linea alba: approximately 1 cm wide firm connective tissue strip between the right and left rectus sheath, extending from the sternum to the symphysis.
Fascia transversalis: above the linea arcuata, it covers the posterior layer of the rectus sheath internally, below the linea it lies directly on the M. rectus abdominis.

3. Internal Relief of the Abdominal Wall

Plica umbilicalis mediana: median peritoneal fold running from the navel to the bladder, within the fold is the Lig. umbilicale medianum (connective tissue strand = urachus remnant).
Plica umbilicalis medialis: paired peritoneal fold, contains on both sides the Lig. umbilicale mediale = obliterated remnant of the bilateral umbilical artery, A. umbilicalis.
Plica umbilicalis lateralis: paired peritoneal fold, beneath it lies on both sides the A. epigastrica inferior with two accompanying veins each.

4. Conduits

a) Arteries

A. epigastrica superior: continuation of the A. thoracica interna, anastomoses at the level of the navel with the A. epigastrica inferior.
A. epigastrica inferior: arises from the A. iliaca externa and runs like the aforementioned artery on the dorsal surface of the M. rectus abdominis in the rectus sheath.
A. epigastrica superficialis: originates from the A. femoralis and distributes in the subcutaneous tissue of the anterior abdominal wall after crossing the inguinal ligament.
Aa. intercostales posteriores VI – XI and A. subcostalis: originate from the thoracic aorta; their terminal branches run obliquely downward between the M. obliquus internus abdominis and M. transversus abdominis and extend from laterally to the rectus sheath, where they anastomose with A. epigastrica superior et inferior.

b) Veins

Vv. epigastricae superiores: accompany the artery of the same name; anastomose with branches of the V. epigastrica inferior and drain into the Vv. thoracicae internae.
V. epigastrica inferior: branches into accompanying veins of the A. epigastrica inferior and drains into the V. iliaca externa.
V. epigastrica superficialis: runs parallel to the artery of the same name (see above).

c) Lymphatic Vessels

Superficial lymphatic vessels: above the navel, they run to the axillary lymph nodes (Nodi lymphatici axillaris), below to the inguinal lymph nodes, Nodi lymphatici inguinales.
Deep lymphatic vessels: usually run parallel with the blood vessels; reach the Nodi lymphatici parasternales, lumbales, and iliaci externi.

d) Nerves

Nn. intercostales VI – XII: as Rr. ventrales of the Nn. thoracici VI – XII; they enter the abdominal wall behind the costal cartilages between the M. obliquus internus abdominis and M. transversus abdominis; motor branches supply the anterior and lateral abdominal muscles, the sensory branches the abdominal skin.
N. iliohypogastricus, N. ilioinguinalis, and N. genitofemoralis: participate in the motor and sensory innervation of the lower abdominal region and genitalia.

Regio umbilicalis: (1) Umbilical ring, (2) Collagen fiber layer, (3) Ligamentum teres hepatis, (4) Umbilical scar, (5) Linea alba, (6) Tendinous intersection of the rectus abdominis muscle, (7) Rectus abdominis muscle (translucent), (8) Anterior cutaneous branches.

The navel or umbilicus refers to the remnant of the umbilical cord attachment, which remains as a scar at the level of the body's midpoint after birth.

Three layers are distinguished at the navel:

• superficial layer consisting of skin and subcutis
• middle, aponeurotic layer
• deep layer of preperitoneal connective tissue and peritoneum

1. Superficial Layer

The relatively delicate navel skin in adults is only movable cranially against the umbilical ring; otherwise, it is firmly anchored everywhere with a tight connective tissue plate located underneath. Within the umbilical ring, the subcutis is very delicately formed and is traversed only by sparse vessels and nerves.

2. Middle Layer

The middle, aponeurotic layer consists of a tight meshwork of connective tissue, traversed by the obliterated embryonic vascular remnants and the remnant strand of the urachus, closing the umbilical opening. At the edges of the umbilical opening, the connective tissue plate is fused with the umbilical ring, into which tendinous cords from the rectus sheath radiate. The closure of the umbilical opening by the tough connective tissue plate is completed by the end of the second year of life.

3. Deep Layer

In the deep layer of the umbilical plate, there is usually a localized fat pad up to the size of a palm, traversed by radial connective tissue strands and divided by a total of five peritoneal folds, the so-called umbilical folds, which extend from lateral caudal to cranial towards the navel:

• one median umbilical fold, contains the obliterated urachus
• two medial umbilical folds, contain the obliterated umbilical arteries
• two lateral umbilical folds, house the inferior epigastric vessels

Against the abdominal cavity, the umbilical region is covered by the transversalis fascia and the peritoneum fused with it. The peritoneum is reinforced in the umbilical region by the umbilical fascia, which is built from tight connective tissue. The fascia extends dorsally from the umbilical vein, is anchored laterally in the posterior layer of the rectus sheath, and ends caudally at the level of the middle of the umbilical ring. Cranially, it extends about 5 cm beyond the navel, with its fibers drawing towards the linea alba and attaching to it.

Between the transversalis fascia and the linea alba is a canal filled only with loose connective tissue (umbilical canal), which can form the path for umbilical hernias.