Anterior Abdominal Wall

 Introduction  :-

                 The abdominal wall refers to the layer of anterolateral  (front and side)  structures including skin,muscles,nerves,vessels and connective tissues between the thorax and pelvis.

                 The abdominal wall has a number of important functions both protecting and containing the abdominal viscera.

                 The muscles of the anterior abdominal wall are able to contact,increasing intra abdominal pressure aiding expiration cutting and vomiting.

Surface of anatomy :-

                    The anterior abdominal wall may be divided into nine regions.

                    The nine regions of the abdomen are created by four imaginary in interesting lines:

• Two mid-clavicular lines : Vertical lines that pass down from the mid-point of the clavicle to the mid-inguinal point.
• The subcostal plane : A transverse line that passes across the abdomen at the level of the inferior aspect of the 10th costal cartilage. This lines bisect the 3rd lumbar vertebrae.
• The trans-tubercular plane : A transverse line that passes across the iliac tubercles. These are located approximately 5 cm posterior to the anterior  superior iliac spine. The line bisets the 5th lumbar vertebrale.

Another commonly discussed plane is the "Transpyloric plane of Addison" or more simply the transpyloric plane. It is located halfway between the supercostal super notch and the top of the pubic symphysis approximately a hands breath below the xiphoid process.

   A number of key structure lie on the transpyloric plane :

• L1 vertebrare 
• Pancreatic neck
• Pylorus of the stomach 
• First part of the duodenum
• Duodenojejunal flexure 
• Fundus of the gallbladder 
• Renal hila.

Muscle :-

         The anterolateral abdominal wall is made up of five muscles:

•   Rectus abdominal
•   External oblique
•   Internal oblique
•   Transversus abdominal
•   Pyramidalis.

           The muscles of abdominal wall have multiple functions. They act to protect and contain the abdominal viscera. They are able to contract increasing intra-abdominal vomiting. Together they help with truncal movements, particularly against resistance.

External oblique :-

                   The external oblique is the largest and outermost muscles of the anterolateral abdominal wall.

       Origin :  external surface of the 5th to 12th ribs.

       Insertion : Linea Alba, pubic tubercle and anterior half of           iliac crest.

       Action : lateral flexon, increasing intra-abdominal pressure,         maintain abdominal tone.

       Vascular supply : intercostal, subcostal and deep circumflex         iliac arteries.

       Innervation : thoracoabdominal and intercostal nerves.

       The inferior margin of the aponeurosis of the external oblique. Muscles is thickend between the axis of the iliac crest and the pubic tubercle. This thickened structure is known as a inguinal ligaments or "poupart's ligament.

Rectus abdominis :-

                  The rectus abdominis is a paired, vertical structure running each side of the linea alba and contained within the rectus sheath.

        Origin : pubic symphysis and pubic crest.

        Insertion : xiphoid process of 5th to 7th costal cartilage.

        Action : flexion of the trunk, maintain abdominal tone.

        Vascular supply : superior and inferior happy gastric artery

        Innervation : T6 - T11 intercostals,subcostal and                    iloinguinal  nerves.

                   The rectus sheath is formed by the aponeurotic layers of the anterolateral abdominal wall muscles. For more on the rectus sheath.

Internal oblique :-

                   The internal oblique is a relatively thin sheath of  muscle that forms the intermediate layer of the anterolateral abdominal wall.

         Origin : Thoracolumbar fascia, iliac crest, iliopectinal             arch.

         Insertion : 9th - 12th ribs (aponeurosis) as high 7th                 costal cartilage) linea Alba, pubic crest.

         Action : lateral flexion, increasing intra-adominal                   pressure, maintain abdominal tone

         Vascular supply : Intercostal,subcostal ,inferior                     epigastric and deep circumflex,iliac artery.

         Innervation  : T8 -T11 intercostals,subcostal,                       iliohypogastric nerves. 

         The fibre of the internal oblique run superomedially. As it approaches the midline the muscles forms aponeurosis ( a broad,flat,tendon ) inserting at the linea alba.

Transversus abdominis :-

                       The two transversus abdominal muscles from the innermost layer of muscles of the anterolateral abdominal wall.

         Origin : 7th to 12th ribs, thoraciclumbar fascia, iliac               crest, inguinal ligament.

         Insertion : Linea alba, pubic crest, pectineal line.

         Action : increasing intra-abdominal pressure maintain                 abdominal tone.

         Vascular supply : intercostal, subcostal, superiorl /                 inferior epigastric, superficial/deep circumflex iliac and           posterior lumbar arteries.

         Innervation : T7 - T11 intercostals, subcostal,ilioinguinal           and iliohypogastric nerves. 

          The fibres of the transversus abdominis run transversely. As it approaches the midline the muscle forms and aponeurosis (a broad,flat and tendon )an inserting at linea alba.

Pyramidalis :-

            The pyramidalis is small triangular muscle that is located anterior to the inferior part of the rectus abdominis.

            Origin: Pubic symphysis and pubic crest. 

            Insertion : Linea alba.

            Action : Atension the linea alba.

            Vascular supply :Inferior epigastric artery.

            The pyramidalis sites in the rectus sheath  anterior to the lower rectus muscles . It is through to have little clinical significance and is absent in 20% of people.