Posterior Abdominal Wall and Kidneys

Posterior abdominal wall and kidneys Key Information The posterior abdominal wall is formed by the lumbar vertebrae, the pelvic girdle, the posterior abdominal muscles and their associated fascia. Find the following features of the posterior abdominal wall in your sections • Bones - Lumbar vertebrae - Sacrum - Ilia - Ribs XI and XII ✓ Attachment points for muscles Muscles Muscle Psoas Major Origin Vertebral bodies of T12-L4, Intervertebral discs between T12-L4, Transverse processes of L1-L5 vertebrae Insertion Lesser trochanter of femur Innervation Action Anterior rami of spinal nerves L1-L3 Hip joint: Thigh/trunk flexion, Thigh: external rotation, Trunk: lateral flexion Psoas Minor Vertebral bodies of T12 & L1 vertebrae Iliopubic eminence, Pectineal line of pubis Anterior rami of spinal nerves L1-L3 Iliacus Iliac fossa Lesser trochanter of femur Femoral nerve (L2L4) Quadratus lumborum Iliac crest, Iliolumbar ligament Inferior border of rib 12, Transverse processes of vertebrae L1-L4 Subcostal nerve (T12), Anterior rami of spinal nerves L1L4 Function: Diaphragm Sternal part: Posterior aspect of xiphoid process Costal part: Internal surfaces of lower costal cartilages and ribs 712 Lumbar part: Medial and lateral arcuate ligaments (lumbocostal arches), bodies of vertebrae L1-L3 (+intervertebral discs), anterior longitudinal ligament Central tendon of diaphragm Phrenic nerves (C3C5) (sensory innervation of peripheries via 6th11th intercostal nerves) Hip joint: Thigh/trunk flexion, Thigh: external rotation, Trunk: lateral flexion Hip joint: Thigh/trunk flexion, Thigh: external rotation, Trunk: lateral flexion Bilateral contraction - Fixes Ribs 12 during inspiration, Trunk extension Unilateral contraction - Lateral flexion of trunk (ipsilateral) Depresses costal cartilages, primary muscle of breathing (inspiration) Fascia Blood supply Nerves • • Subcostal nerves Lumbar plexus - Formed by the anterior rami of L1-4, some contribution from subcostal) - 7 branches: Iliohypogastic (L1) - Ilioinguinal (L1) Genitofemoral (L1, 2) - Lateral cutaneous nerve of the thigh (L2, 3) - Obturator (L2-4) o Femoral (L2-4) Lumbosacral trunk (L4, 5) Kidneys and suprarenal glands • The kidneys are retroperitoneal in the abdomen, one on each side of the vertebral column. They are approximately 10-12cm in length, 6 cm in width and 3 cm thick. • • The kidneys extend from the T12 to L4 vertebrae, with the right kidney slightly lower than the left (right L1-L4, left T12-L3). They are embedded in fat (perirenal fat) and surrounded by a fascia (renal fascia). • The anterior relations of the kidney are different on each side • The kidneys are anterior to the 12th rib on the right side and 11th and 12th rib on the left side. Posterior relations of the kidneys include psoas major, quadratus lumborum and transverse abdominis muscles, subcostal vessels, and nerves (T12) and the iliohypogastric and ilioinguinal nerves (branches of L1 spinal nerve). • • • The renal hilum is located at the concave medial margin of the kidney and contains the renal artery, renal vein (left vein longer than right vein and arise from the aorta at level L1-L2) and the upper end of the ureter. Normally the renal vein is anterior, the ureter posterior and the renal artery in between (secondary branches of the vessels are not unusual). Suprarenal glands • • • The suprarenal glands are found on the posterior poles of the kidneys and are surrounded by adipose tissue. The suprarenal glands can be divided into two functionally and histologically distinct parts, the suprarenal cortex, and the suprarenal medulla. The suprarenal cortex secretes corticosteroid class of hormones regulated by the pituitary hormone ACTH, and the suprarenal medulla secretes epinephrine and norepinephrine under the control of the sympathetic nervous system