BMS Anatomy Lecture 5: Anterior and Posterior Abdominal Wall Muscles, Inguinal Canal PDF

BMS Anatomy Lecture 5 Anterior and Posterior Abdominal Wall Muscles, Inguinal Canal Presented By: Dr. K. Lumsden; [email protected] (Toronto Campus) Dr. M. Doroudi; [email protected] Boucher Campus) Moore's Clinically Oriented Anatomy, by Arthur F. Dalley II PhD FAAA (Author), Anne M. R. Agur BSc...

BMS Anatomy Lecture 5 Anterior and Posterior Abdominal Wall Muscles, Inguinal Canal Presented By: Dr. K. Lumsden; [email protected] (Toronto Campus) Dr. M. Doroudi; [email protected] Boucher Campus) Moore's Clinically Oriented Anatomy, by Arthur F. Dalley II PhD FAAA (Author), Anne M. R. Agur BSc (OT) MSc PhD FAAA (Author), 9th ed. Abdomen Chapter Pages 415 – 421, 431 – 433, 544 – 545 Anterior and posterior Abdominal Wall Muscles Anterior Abdominal Wall Muscles Ant. & Lat. Abdominal Wall Muscles • Obliquus externus abdominis (External abdominal oblique muscle) situated on the lateral and anterior parts of the abdomen, is the largest and the most superficial of the three flat muscles in this region. • Ori: External surfaces of lower 8 ribs • Ins: Linea alba (midline of rectus sheath) Pubic tubercle Anterior half of iliac crest Fun: movement of the ribcage contralateral rotation bilateral: flexion of the trunk compress the abdominal contents - isometric - they contract every time you have a bowel movement What is the inguinal ligament? - serves as an attachment point for our oblique muscles • Nerve: Intercostal nerves (T7 to T12) Obliquus internus abdominis (Internal abdominal oblique muscle) thinner and smaller than the Obliquus externus, beneath which it lies, is of an irregularly quadrilateral form, and situated at the lateral and anterior parts of the abdomen. • Ori: - lateral 1/3 of Inguinal ligament - Anterior 2/3 of iliac crest, - Thoracolumbar fascia (shares an attachment with spinal muscles) • Ins: ▪ Linea alba ▪ Lower 3 ribs • Fun: Helps form the rectus sheath Unilateral: ipsilateral rotation Bilateral: flexion of trunk compression of the abdominal wall - Nerve: Intercostal nerves (T6 to T12) & L1 • Transversus abdominis muscle is the most internal of the flat muscles of the abdomen, being placed immediately beneath the internal abdominal oblique muscle. • Ori: • Inguinal ligament • Iliac crest • Thoracolumbar fascia • Cartilages of the lower 6 ribs - Ins: - Linea alba (also helps form the rectus sheath) • Fun: compresses the abdomen - Nerve: Intercostal nerves (T6 to T12) & L1 •Rectus abdominis is a long flat muscle, which extends along the whole length of the front of the abdomen, and is separated from its fellow of the opposite side by the linea alba. Ori: pubic crest, and symphysis pubis. Ins: o Xiphoid process o Cartilages of ribs 5,6,7 Note: The Rectus is crossed by fibrous bands, three in number, which are named the tendinous intersections. •Fun: - flexion of the trunk @ the spinal joints - can initiate posterior pelvic tilt - compresses the abdominal abdomen • Nerve: Intercostal nerves (T6 – T12) Layers of the Abdominal wall Camper's Fascia = fatty layer • A thick superficial layer of adipose and areolar connective tissue • Sits just deep to the skin of the abdomen • More prominent in lower aspect of abdomen (inferior to umbilicus) Scarpa’s Fascia = Deep membranous layer • Sits between Camper’s fascia and rectus sheath • Anchored laterally to the aponeurosis of the external oblique and medially to the linea alba of the rectus sheath Rectus Sheath = protective covering over rectus abdominis • Composed of the aponeurosis of the three flat muscles as they converge in the midline to form the median linea alba • External oblique • Internal oblique • Transversus Abdominis • *Composition to sheath changes inferior to the umbilicus 9 Layers of the Abdominal wall ANTERIOR Rectus Sheath: • A durable, resilient, fibrous compartment that contains and protects the rectus abdominis • The composition and arrangement of muscle layers differs depending on location with respect to an area known as the Arcuate line • Arcuate line – Located ½ of the distance between umbilicus and pubic symphysis • Inferior to this point the aponeuroses of all 3 lateral abdominal muscles pass anterior to the rectus abdominis muscle • At this level, the internal aspect of rectus abdominis muscle is in direct contact with the transversalis fascia • A thin layer of CT located between the posterior surface of the TA muscle a the extraperitoneal fat of the parietal peritoneum • directly by the abdominal cavity 10 Layers of the Abdominal wall 1. 2. 3. 4. Skin Camper’s Fascia Scarpa’s Fascia Rectus Sheath: SUPERIOR to arcuate line ANTERIOR • Anterior lamina (sheet) – full aponeurosis of external oblique and ANTERIOR 1/2 of the aponeurosis of the internal oblique • Posterior lamina (sheet) – POSTERIOR 1/2 of the aponeuroses of the internal oblique and full aponeurosis of transversus abdominis 5. 6. 7. Transversalis fascia Extraperitoneal fat (does not get removed - this is protective) Parietal Peritoneum (first layer of abdominal cavity) POSTERIOR 11 Layers of the Abdominal wall 1. 2. 3. 4. Skin Camper’s Fascia Scarpa’s Fascia Rectus Sheath: INFERIOR to arcuate line ANTERIOR • Anterior lamina (sheet) – aponeuroses of all 3 abdominal muscles • Posterior lamina (sheet) – no layer! • Transversalis fascia now directly meets the posterior aspect of rectus abdominis mm. 5. 6. 7. Transversalis fascia Extraperitoneal fat Parietal Peritoneum POSTERIOR 12 Layers of Anterolateral Abdominal Wall SUPERFICIAL DEEP 1. 2. 3. 4. 5. 6. 7. 8. 9. Skin/Superficial fascia Camper’s fascia – fatty layer Scarpa’s fascia – membranous layer External oblique m. Internal oblique m. Transversus abdominis m. Transversalis fascia Extraperitoneal fat Parietal layer of peritoneum X 13 MUSCLES OF THE POSTERIOR ABDOMINAL WALL • Quadratus lumborum – Ori: - Iliac crest - Iliolumbar ligament – Ins: - Rib 12 - TVPs of L1 – L4 – Fun: - extender of the trunk of lumbar spine - lateral flexion of lumbar spine - fixes rib 12 – Nerve: Ventral rami of spinal nerves T12, L1, 2, 3, 4 • Psoas Major – Ori: - Bodies and TVPs of L1 – L5 – Ins: - Lesser trochanter of femur Fun: - flexes the hip - lateral rotation of the thigh - lateral flexion of the trunk Bilateral: trunk flexion (lumbar spine) Nerve: Lumbar plexus (L1, L2, L3) Iliacus – Ori: - Iliac fossa - Sacral ala – Ins: - Lesser trochanter of femur – - Fun: flexion of the thigh lateral rotation of the thigh – Nerve: Femoral N. ❒ The psoas major and the iliacus muscles are sometimes considered to be the iliopsoas M. because of their common distal attachment onto the lesser trochanter of femur. The Inguinal Canal: It is an oblique canal about 4 cm. long, directing downward and medial ward, and placed parallel with and a little above the medial half of the inguinal ligament. It extends from the deep inguinal ring to the superficial inguinal ring. It contains the spermatic cord (containing ductus (vas) deferens, testicular vessels, autonomic nerves and lymphatic) and the ilioinguinal nerve in males, and the round ligament of the uterus and the ilioinguinal nerve in females. Superficial inguinal ring: A triangular gap in the external oblique aponeurosis. Deep inguinal ring: an oval shape opening in the fascia transversalis; situated half an inch above the mid inguinal point (and immediately lateral to the stem of the inferior epigastric vessels). Conjoint tendon: is formed by the fusion of the lowest aponeurotic fibers of the internal oblique and of the transversus abdominis muscles. It lies behind the superficial inguinal ring and strengthens the abdominal wall at this point. 17 18 Note: In this session, we ONLY need to learn the number and name of the cranial nerves. The rest of this table will be taught later.