Anterior Abdominal Wall PDF

ANTERIOR ABDOMINAL WALL Dr Ramya Rathan Asst Prof- Anatomy OBJECTIVES ▪ Explain the subdivisions of the abdomen. ▪ Describe the fascia of the anterior abdominal wall ▪ Describe the attachments of muscles of anterior abdominal wall SUBDIVISIONS ▪ Four quadrants (divided by the horizontal transumbilic...

ANTERIOR ABDOMINAL WALL Dr Ramya Rathan Asst Prof- Anatomy OBJECTIVES ▪ Explain the subdivisions of the abdomen. ▪ Describe the fascia of the anterior abdominal wall ▪ Describe the attachments of muscles of anterior abdominal wall SUBDIVISIONS ▪ Four quadrants (divided by the horizontal transumbilical and vertical median planes) SUBDIVISIONS ▪ Nine abdominopelvic regions, ▪ Superior subcostal plane - passes right under the costal margins of the 10th ribs, ▪ Inferior intertubercular plane- connects the tubercules of the iliac crest. ▪ Midclavicular planes- passes through the midpoint of each clavicle and halfway between the pubic symphysis and the anterior superior iliac spine. FASCIA Skin - Superficial layer. ▪ In pregnant women, obese people and those with abdominal distention, it can contain elongated lines called stretch marks or striae distensae. The superficial fascia ▪ located just below the skin and consists of connective tissue. ▪ Superior to the umbilicus, it is similar and continuous to the superficial fascia of the body and is made up mostly of one layer. ▪ Inferior to the umbilicus, it is divided into two layers: Superficial Camper’s fascia, which is a thicker fatty layer that can have a variable degree of thickness. Deep Scarpa's fascia, which is a thinner and denser membranous layer overlying the muscle layer of the abdominal wall. ▪ Scarpa's fascia - firmly attached to the Linea alba and pubic symphysis and fuses with the fascia lata (deep fascia of the thigh) right below the inguinal ligament. ▪ In men, the Camper’s fascia continues over the penis and blends with the Scarpa’s fascia to form the superficial fascia of the penis. The latter extends further on into the scrotum, where it contains smooth muscle fibers and becomes the dartos fascia. ▪ Scarpa’s fascia continues into the perineum to form the superficial fascia of the perineum, called Colles’ fascia. In women it continues into the labia majora and anterior perineum. MUSCLES ▪ Lateral flat muscle group situated on either side of the abdomen, which includes three muscles: external oblique, internal oblique and transversus abdominis. ▪ Anterior vertical muscles situated bilaterally to the median fibrous structure called Linea alba. They are called rectus abdominis and pyramidalis muscles. EXTERNAL ABDOMINAL OBLIQUE MUSCLE ▪ Most superficial - attaches to the outer surfaces of the lower ribs and iliac crest. ▪ Continues anteriorly as the external oblique aponeurosis, which courses anteriorly to the rectus abdominis muscle and inserts into the linea alba. ▪ The inferior border of the external oblique aponeurosis, between the anterior superior iliac spine and the pubic tubercle, is called the inguinal ligament. EXTERNAL ABDOMINAL OBLIQUE MUSCLE ▪ Origin: External surface of ribs 5-12 ▪ Insertion: Linea alba, pubic tubercle, anterior half of iliac crest ▪ Innervation: Lower intercostal nerves (T7-T11), subcostal nerve (T12), Iliohypogastric nerve (L1) ▪ Function: ▪ Bilateral contraction - Trunk flexion, Compresses abdominal viscera, Expiration ▪ Unilateral contraction - Trunk lateral flexion (ipsilateral), Trunk rotation (contralateral) INTERNAL ABDOMINAL OBLIQUE MUSCLE ▪ Origin: Thoracolumbar fascia, anterior iliac crest, iliopectineal arch ▪ Insertion: Continues anteriorly as the internal oblique aponeurosis, which splits around the rectus abdominis muscle to insert into the linea alba ▪ Innervation: Lower intercostal nerves (T7-T11), subcostal nerve (T12), Iliohypogastric nerve (L1), ilioinguinal nerve (L1) ▪ Function: (flexion only – omit the rest) ▪ Bilateral contraction - Trunk flexion, Compresses abdominal viscera, Expiration ▪ Unilateral contraction - Trunk lateral flexion (ipsilateral), Trunk rotation (ipsilateral) TRANSVERSUS ABDOMINIS MUSCLE ▪ Origin: Costal cartilages of ribs 7-12, thoracolumbar fascia, anterior iliac crest, iliopectineal arch ▪ Insertion: continues anteriorly as the transverse abdominis aponeurosis and inserts into the Pubic crest, Pectineal line of pubis ▪ Innervation: Lower intercostal nerves (T7-T11), subcostal nerve (T12), Iliohypogastric nerve (L1), ilioinguinal nerve (L1) ▪ Function: respiration ▪ Bilateral contraction - Compresses abdominal viscera, Expiration ▪ Unilateral contraction - Trunk rotation (ipsilateral) ANTERIOR ABDOMINAL WALL MUSCLES ▪ Rectus abdominis muscle: Origin: Pubic symphysis, Pubic crest 5-7 Insertion: Xiphoid process, Costal cartilages of ribs Innervation: Intercostal nerves (T7-T11), Subcostal nerve (T12) Function: Trunk flexion, Compresses abdominal viscera, Expiration ▪ Pyramidalis muscle Origin: Pubic symphysis, Pubic crest Insertion: Linea alba Innervation: Subcostal nerve (T12) Function: Tenses linea alba DEEP FASCIAL LAYERS ▪ Transversalis fascia. A thin, aponeurotic membrane, deep to the transverse abdominis muscle. ▪ Extraperitoneal fat. A thin layer of connective tissue and fat lining the abdominal wall between the transversalis fascia and the parietal peritoneum. The extraperitoneal fat is more abundant in the posterior abdominal wall, especially around the kidneys and in the pelvic floor. ▪ Parietal peritoneum. Parietal peritoneum is a serous membrane lining the internal surface of the abdominal wall. The parietal peritoneum forms the mesentery that suspends the abdominal viscera and is continuous with the visceral peritoneum. APPLIED ANATOMY ▪ A Caesarean section (“C-section”) is a surgical procedure for which incisions are made through a pregnant woman's abdomen to access the uterus for delivery of the infant. ▪ The most common incision location for a C-section is the lower uterine section where a transverse cut is made superior to the pubis and bladder, through all layers of the anterior abdominal wall. ▪ From superficial to deep, the layers cut through during a C-section are the skin, Camper's fascia, Scarpa's fascia, rectus sheath, pyramidalis muscle, rectus abdominis muscle, transversalis fascia, extraperitoneal fascia, and, finally, the parietal peritoneum.