Anatomy and Physiology of the Abdominal Wall 0011 CHAPTER Internal Oblique Some Inferior ﬁ Bers Form the Cremaster Muscle at the Level of the Inguinal Canal

Handbook of Complex Abdominal Wall Anatomy and physiology of the abdominal wall 0011 CHAPTER Álvaro Robín Valle de Lersundi, MD, PhD Arturo Cruz Cidoncha, MD, PhD 11.1..1. Anatomy of the abdominal wall 1.1.1. Introduction The abdominal wall is delimited by muscle structures than can be classifi ed in 5 anatomical areas: lateral, anterior, posterior, diaphragmatic and perineal (Table 1.1). We will describe the fi rst four due to their relevance in surgical repair of complex abdominal wall. These groups of muscles are enclosed by several bone structures: last ribs, chondrocostal joints, xyphoid, pelvis and costal apophysis of lumbar vertebrae. Layers of the anterior and lateral abdominal wall include skin, subcutaneous tissue, superfi cial fascia, deep fascia, muscles, extraperitoneal fascia and peritoneum. Table 1.1. Muscular limits of the abdominal wall ∙ Quadratus lumborum POSTERIOR ∙ Psoas ∙ Iliac muscle ∙ External oblique LATERAL ∙ Internal oblique ∙ Transversus abdominis ∙ Rectus abdominis ANTERIOR ∙ Piramidalis CONTENTS SUPERIOR ∙ Diaphragm 1.1. Anatomy of the abdominal INFERIOR ∙ Perineal muscles wall 1.1.2. Muscles of the abdominal wall 1.2. Physiologyygy Muscles of the anterolateral wall Rectus abdominis The rectus abdominis (m. rectus abdominis) is a long and thick muscle that is extended from the anterolateral thorax to the pubis close to the midline (Figure 1.1). 1 Figure External oblique 1.1. Rectus abdominis The external oblique muscle (m. obliquus externus abdominis) is the most superfi cial and thickest of the three lateral abdominal wall muscles (Figure 1.2). Figure 1.2. External oblique muscle Handbook of Complex Abdominal Wall Handbook of Complex Cranially, the rectus abdominis muscles originates from 3 dig- itations that insert on the 5th-7th costal cartilages, the xyphoid process and costoxyphoid ligament. Caudally, it inserts on the anterior surface of the superior border of the pubis, symphysis and pubic crest. The muscle is packed between the anterior and posterior rectus sheaths, except on the lower third of the abdomen where it is only covered by the anterior sheath. Laterally, the rectus sheath merg- Its muscle fi bers originate from the anterior surface of the lower es within the aponeurosis of the external oblique muscles to form eight ribs that intertwine with insertions of the serratus anterior the linea semilunaris. and latissimus dorsi. Three to four horizontal tendinous structures, that closely adhered It runs vertically and medially and the muscular tendinous bound- to the anterior rectus sheath, interrupt the rectus abdominis along ary descends in such a way that, approaching the midline and its length. These intersections make diffi cult the dissection between also below the anterosuperior iliac spine, the muscle becomes the anterior rectus sheath and the muscle and explain why hemato- completely aponeurosis. Inferiorly the aponeurosis bends in itself mas and abscesses mainly extend over the posterior rectus sheath. to form the inguinal ligament, which extends between the anterior superior iliac spine and pubic tubercle. Table Anteriorly the aponeurosis joins the aponeurosis of internal oblique 1.2. Relevant characteristics of the rectus abdominis and contributes to form the anterior rectus sheath and linea alba, crossing the midline with fi bers of the other side. Characteristics ∙ Originates on the anterior surface of 5, 6, 7 costal cartilages and xyphoid Insertion on the pubis is made through the pillars of the su- ∙ Insertion on the anterior surface of pubis and symphysis of pubis perfi cial inguinal ring, the inguinal ligament and Gimbernat´s ∙ Packed in their sheaths except in the lower third where the posterior sheath is missing ligament. ∙ Diffi culty of dissection between the anterior rectus sheath and the muscle ∙ The most important muscle for fl exion of the trunk ∙ Used for pedicled muscle fl aps Table 1.3. Relevant characteristics of external oblique Pyramidalis Characteristics The pyramidalis (m. pyramidalis) is a small muscle that can be ∙ Originates from the anterior surface of the last 8 ribs found inferiorly overlaying the rectus (Figure 1.1). It is a rudimen- ∙ The thickest muscle of the lateral abdominal wall tary muscle that can be missing in 20% of subjects. ∙ Inferior and medial direction of fi bers of muscle and aponeurosis ∙ The aponeurosis contributes to form anterior rectus sheath ∙ Boundary between muscle and aponeurosis It originates from the pubis and inserts into the lateral borders of ∙ It bends in itself to form the inguinal ligament linea alba, inferior to the umbilicus. 2 Anatomy and physiology of the abdominal wall 0011 CHAPTER Internal oblique Some inferior fi bers form the cremaster muscle at the level of the inguinal canal. The internal oblique muscle (m. obliquus internus abdominis) lies between the external oblique muscle and transversus abdominis There is an avascular layer of loose connective tissue between (Figure 1.3). Posteriorly, it is covered by the latissimus dorsi. external oblique and internal oblique muscles that allows easy dissection between these muscle layers. Figure Transversus abdominis 1.3. Internal oblique muscle The transversus abdominis muscle (m. transversus abdominis) is the deepest of the three lateral abdominal wall muscles and runs in a horizontal direction (Figure 1.4). Fleshy in the middle and tendinous at the extremities, it covers the entire lateral half of the abdominal wall, from the spine to the linea alba. Figure 1.4. Transversus abdominis It originates from the thoracolumbar fascia (fascia toracolum- baris), anterior two thirds of the iliac crest, and lateral half of the inguinal ligament. The internal oblique muscle runs in a superomedial direction, perpendicular to the external oblique muscle. At the level of linea semilunaris, it becomes a wide aponeurosis. In the superior two-thirds the aponeurosis splits medially to form the anterior and the posterior rectus sheaths. In the inferior third, It originates from the thoraco-lumbar fascia, the iliac crest, the in- the aponeurosis does not split, joins the anterior aponeurosis of guinal ligament and from the inner surface of the lower six costal external oblique muscle and only comprises the anterior rectus cartilages, interdigitating with the insertions of fi bers of the dia- sheath. The inferior border of the posterior rectus sheath is the phragm (Figure 1.5). Posteriorly, the transversus abdominis also arcuate line. starts from a wide aponeurosis of insertion in the thoraco-lumbar fascia, over the cuadratus lumborum, which has been termed The internal oblique inserts on the inferior border of the 10th to 12th posterior aponeurosis of the transversus abdominis. In posterior ribs superiorly. Inferiorly, the internal oblique inserts with aponeu- component separation technique, the mesh can be laid on this rotic fi bers from the transversus abdominis, forming the conjoined posterior aponeurosis (Figure 1.6). tendon, which inserts on the pubic crest. The muscle runs horizontally and ends medially in a broad fl at aponeurosis in the linea semilunaris, with a shape of a curve line Table with medial concavity. Above the arcuate line, the aponeurosis 1.4. Relevant characteristics of internal oblique joins the internal oblique aponeurosis and the linea alba. Characteristics In the superior third of the abdomen the fi bers of the muscle ex- ∙ Originates from thoracolumbar fascia, iliac crest and inguinal ligament. tend behind the rectus abdominis muscle approaching the mid- ∙ Fibers run perpendicular to the external oblique muscle line. ∙ Easy dissection between the muscle layers of external oblique and internal oblique ∙ The aponeurosis does not form the posterior rectus sheath below the Below the arcuate line, the aponeurosis of the muscle contributes arcuate line to form the conjoined tendon with the internal oblique. At this level, ∙ It has insertions on the inferior border of 10th-12th ribs the differentiation between the fi bers of internal oblique and trans- ∙ Involved in the composition of the conjoined tendon versus is quite diffi cult. 3 Figure It is not an easy task to separate the layer of the transversus ab- 1.5. Anatomical relationships between transversus dominis from the internal oblique because the neurovascular bun- abdominis and diaphragm dles are intercalated in this space. Muscles of the posterior wall Quadratus lumborum The quadratus lumborum (m. Quadratus lumborum) is a fl at and quadrangular muscle situated between the last rib and the iliac crest (Figure 1.7). It originates in the iliac crest and iliolumbar ligament and its fi bers ascend to insert on the 12th rib and transverse apophysis of the fi rst lumbar vertebrae. The lateral fi bers are more vertical than the medial ones that are oblique. Handbook of Complex Abdominal Wall Handbook of Complex It is covered by the posterior aponeurosis of transversus abdominis muscle. Figure 1.6. Extension of the mesh following the plane behind Figure the transversus abdominis and laying on the posterior aponeurosis 1.7. Quadratus lumborum and psoas iliacus of transversus abdominis and quadratus lumborum. 1: transversus abdominis; 2: mesh; 3: thoracolumbar fascia; 4: posterior fascia of transversus abdominis; 5: quadratus lumborum; 6: psoas Iliopsoas Table 1.5. Relevant characteristics of transversus abdominis The iliopsoas muscle (m. iliopsoas) is made of 2 muscles: psoas major and iliacus. Characteristics ∙ Originates from thoracolumbar fascia, iliac crest, inguinal ligament and The iliacus muscle (m. iliacus) originates

Load more