Abdominal Muscles PDF

Anterior & Posterior abdominal wall Dr/ Hind Hamdy Anatomy department Benha faculty of medicine  Abdomen It is bounded above by the xiphoid process of the sternum and costal margin, and below by the upper parts of the pelvic bones and the upper margins of the...

Anterior & Posterior abdominal wall Dr/ Hind Hamdy Anatomy department Benha faculty of medicine  Abdomen It is bounded above by the xiphoid process of the sternum and costal margin, and below by the upper parts of the pelvic bones and the upper margins of the lower limbs. Anterior abdominal wall Layers: - 1-skin 2-superficial fatty layer 3-deep membranous layer 4-external oblique muscle 5-internal oblique muscle 6-transversus abdominis 7-fascia transversalis 8-extraperitoneal fat 9-parietal peritoneum 1- External oblique muscle Origin: Eight fleshy muscular digitations from the lower eight ribs close to their costal cartilage. Direction of fibers: Downwards, forwards & medially. Insertion: Aponeurosis inserted into the xiphoid process, linea alba, pubic crest and tubercle, and ASIS fleshy part descend to inserted into ant. ½ of the outer line of iliac crest. Particular features: Free borders of ext. abdominal oblique muscle: Upper horizontal border Posterior vertical border Lower free border The inguinal ligament: The free lower border of the aponeurosis of E.O.M. between the anterior superior iliac spine laterally and the pubic tubercle medially folding backward upon itself. It gives partial origin to the internal abdominal oblique & transversus abdominus muscles. Superficial inguinal ring: It is a perforation In the lower medial part of the aponeurosis of the external oblique that allows transmission of the spermatic cord or the round ligament of the uterus through it. 2- Internal oblique muscle Origin: the lateral 2/3 of the upper inner surface of the inguinal ligament. anterior 2/3 of the intermediate line of the iliac crest lumbar fascia. Direction of fibers: Upwards, forwards & medially Insertion: Aponeurosis the lower six costal cartilages, xiphoid process, linea alba, pubic crest, and pectineal line. 3- Transversus abdominus muscle Origin: the lateral one-third of the upper concave surface of the inguinal ligament. Anterior two-thirds of the inner lip of the iliac crest. Lumbar fascia The inner surfaces of the lower six costal cartilages Direction of fibers: Transversely forwards. Insertion: Aponeurosis into the xiphoid process, linea alba, pubic crest, and pectineal line. Conjoint tendon Formed by the lower muscle fibers of internal oblique and transverses abdominus passing medially and forming an arch from their origin to their insertion, crossing over the spermatic cord to gain insertion into the public crest and pectineal line where 2 appenurosis fuse as conjoint tendon. 4- Rectus abdominus muscle Origin: By two narrow tendinous heads; one large head arising from the pubic crest and tubercle and the other smaller head from the symphysis pubis. Insertion: By fleshy slips into the fifth, sixth and seventh costal cartilages. The most medial slip gains insertion into the xiphoid process. The muscle is intersected along its course by three or four transverse fibrous bands; Tendinous intersections: 1-3 or 4 2-levels of each one : -One at the level of the xiphoid process. -One at the level of the umbilicus. -One midway between the xiphoid process and the umbilicus. -The 4th one may be present in some people below the level of umbilicus. 3- seen on the anterior surface. 4-Absent on the posterior surface. Rectus sheath: It has an anterior wall and a posterior wall which meet at the lateral margin of the rectus muscle, while medially, they fuse into the Linea alba. The anterior wall covers the whole anterior surface of the muscle while the posterior wall of the sheath covers only the upper three-quarters of the posterior surface of the muscle, leaving the lower quarter of the muscle in direct contact with a fascia, the transversalis fascia.  Thus, the posterior wall of the rectus sheath ends in a curved lower margin; termed the arcuate line. Contents: 1-Two muscles (rectus abdominus and the pyramidalis when present). 2-Epigastric arteries and veins, 3-The terminal parts of the lower five intercostal and subcostal nerves. 5- Pyramidalis muscle Origin: From the pubic crest. Insertion: : Into the lower part of the linea alba. Nerve supply of muscles of the anterior abdominal wall: External Oblique muscle by ventral rami of 7- 12ththoracic nerve Internal Oblique muscle, transverse abdominus :- lower 6 thoracic nerves and 1st lumbar (iliohypogastric and ilioinguinal nerves) Rectus abdominis :-lower 6 thoracic nerves Pyramidalis :-subcostal nerve (T12)  Actions of muscles of anterior abdominal wall Movements of the trunk Respiratory actions Expulsive actions Supportive actions Protective actions  The actions of the muscles of the anterolateral abdominal wall Compression of the abdominal contents and keeping them in position the tone of muscles have a protective and supportive action The muscles assist in the process of expiration during breathing. In forced expiration during coughing pull on ribs downwards in expulsive action during urination defecation and labour, contraction of abd. Muscles and diaphragm the compression of the abdominal contents causes an increased intra- abdominal pressure that assists the act to be done. Both oblique muscles help in laterally flex and rotate the trunk , rectus abdominus muscle flex the trunk forwards 1- Quadratus Lumborum muscle Origin: Posterior 1\3 of the iliac crest. Insertion: Medial half of lower border of 12th rib and tips of transverse processes of upper 4 lumbar vertebrae. Nerve supply: Subcostal nerve (T12) and upper 4 lumbar nerves. Action: Lateral flexion of the vertebral column. Extends lumbar vertebrae Thank you