The abdomen

Anterior Abdominal Wall Superior Border Infrasternal notch Costal Margins and Arch

Anterior Abdominal Wall Inferior Borders

Inguinal Ligament What is it? Where does it attach? What does it separate? Inguinal fold

Surface Anatomy Umbilicus Level Variety

Anterior Median line Linea alba

Levels of Markers and Planes Subcostal plane Transtubercular plane Midclavicular plane

Zones of the Abdomen Hypochondriac, Epigastric Lumbar (Lateral), Umbilical Iliac (Inguinal), Hypogastric

Fascia of the abdominal wall Two layers

Superficial Fascia Over most of body In lower abdominal region

Deep Fascia

Nerves and blood vessels

Organization of the nervous system Dorsal roots Dorsal root ganglia Ventral roots Meninges Dura mater Arachnoid membrane Pia mater

Filum terminale – extension of pia mater Coccygeal ligament – filum terminale fuses with dura mater and attaches to coccyx

Organization of Nerves As they exit the vertebral column, the dorsal and ventral roots join to form the spinal nerve (a mixed nerve) The spinal nerve then divides into a posterior (dorsal) primary ramus and an anterior (ventral) primary ramus

Dorsal and Ventral Rami The dorsal primary ramus innervates the skin and muscles around the spine The ventral primary ramus innervates the skin and muscles for the rest of the body Lateral and anterior trunk Upper and lower extremities

Anterior Rami Nerve plexuses Cervical: C1-C4 Brachial: C5-T1 Lumbar: branch from T12, and L1-L4 Sacral: L4-S3 Pudendal: Parts of S2 and S3, and all of S4 – important for control of bowel, bladder and sexual function

Anterior Rami in the Thoracic Region Do NOT form a nerve plexus T1-T11: Intercostal nerves Travel between ribs T12: Subcostal nerve Travels below 12th rib L1: Follow similar direction as intercostal and subcostal nerves Iliohypogastric nerve: lowest cut. nerve in abdomen Ilioinguinal nerve

Branches of T1-L1 Motor branches to intercostal and abdominal muscles Lateral cutaneous branch – sensory to skin Anterior and posterior branches Anterior cutaneous branch – sensory to skin

Walls of Inguinal Canal Anterior wall Part of aponeurosis of external oblique Reinforced laterally by fibers of int. oblique and sometimes the transversus abdominis Posterior wall Fascia transversalis Medially by fibers of conjoint tendon, the common tendon of int. oblique and transversus abdominis muscles

Superior wall (roof) Inferior wall (floor) Arching fibers of IO and TA Superior surface of inguinal ligament Lacunar ligament Medial part of inguinal ligament that is reflected back and attaches to pectineal line

Superficial Inguinal Ring Medial crus – pubic bone and pubic crest medial to pubic tubercle Lateral crus – pubic tubercle Center point of ring superior to pubic tubercle Intercrural fibers

Deep inguinal ring Slit-like opening in fascia transversalis Immediately superior to midpoint of inguinal ligament

Inguinal Canal Male: spermatic cord Female: Round ligament of uterus

Hernias More common in men Indirect: hernia follows path from deep ring to canal to superficial ring More common Direct: hernia directly through weakness in abdominal wall

Linea alba and rectus sheath See handout