14 POSTERIOR ABDOMINAL REGION

Page 1: Introduction

Instructor Information

  • Dr. Gholamreza HassanzadehProfessor of AnatomyTehran University of Medical Sciences

Page 2: Lumbar Vertebrae

Characteristics

  • Vertebral Bodies: Massive and progressively increase in size from L1 to L5.

  • Pedicles: Short.

  • Transverse Processes: Long and slender.

  • Spinous Processes: Large and quadrangular.

  • Articular Processes: Large and oriented medially and laterally.

    • Function: Promotes flexion and extension of the vertebral column.

Page 3: Sacrum

Structure

  • Formed by the fusion of five sacral vertebrae into a wedge-shaped bone.

  • Shape: Broad superiorly and narrows inferiorly.

  • Surface Types:

    • Concave anterior surface.

    • Convex posterior surface.

  • Sacral Foramena: Contains anterior and posterior foramina for rami of spinal nerves.

Page 4: Pelvic Bones

Composition

  • Ilium: Each pelvic bone; connects to the sacrum at the sacro-iliac joints.

  • Iliac Fossa: The upper part expands outward into a wing-like area.

  • Function: Medial side contributes to the posterior abdominal wall alongside related muscles.

Page 5: Ribs

Posterior Abdominal Wall

  • Ribs XI and XII: Complete the bony framework.

    • Unique characteristics: Do not articulate with the sternum or other ribs, single articular facet, lack necks or tubercles.

  • Locations:

    • Rib XI is posterior to the superior part of the left kidney.

    • Rib XII is posterior to both kidneys and serves as an attachment point for muscles and ligaments.

Page 6: Muscles of Posterior Abdominal Wall

Overview

  • Muscles forming boundaries fill the bony framework:

    • Medial: Psoas major and minor.

    • Lateral: Quadratus lumborum.

    • Inferior: Iliacus.

    • Superior: Diaphragm.

Page 7: Psoas Major and Minor

Psoas Major Muscle

  • Covers anterolateral surface of lumbar vertebrae.

  • Origin: Bodies of T12 and all lumbar vertebrae, intervertebral discs, transverse processes.

  • Pathway: Passes inferiorly to the anterior thigh to attach at the lesser trochanter of the femur.

Page 8: Function and Innervation

Psoas Major Function

  • Flexes the thigh at the hip when trunk is stabilized.

  • Flexes the trunk against gravity when supine.

Innervation

  • Innervated by anterior rami of nerves L1 to L3.

Page 9: Psoas Minor Muscle

Overview

  • Often absent; lies on psoas major.

  • Origin: Vertebrae T12 and L1.

  • Insertion: Pectineal line of pelvic brim and iliopubic eminence.

Innervation

  • Innervated by the anterior ramus of nerve L1.

Page 10: Quadratus Lumborum

Characteristics

  • Fills space between rib XII and iliac crest; overlaps psoas major.

  • Origin: Transverse process of L5, iliolumbar ligament, iliac crest.

  • Attachment: Transverse processes of first four lumbar vertebrae, inferior border of rib XII.

Page 11: Function and Innervation of Quadratus Lumborum

Functions

  • Depresses and stabilizes rib XII.

  • Contributes to lateral trunk bending.

  • May extend the lumbar vertebral column.

Innervation

  • Innervated by anterior rami of T12 and L1 to L4 spinal nerves.

Page 12: Iliacus Muscle

Overview

  • Fills iliac fossa; joins with psoas major to form iliopsoas.

Function

  • Flexes thigh at hip joint when trunk is stabilized.

  • Flexes trunk against gravity when supine.

Innervation

  • Innervated by branches of the femoral nerve.

Page 13: Diaphragm as Boundary

Structural Overview

  • Forms the boundary of the posterior abdominal region.

  • Separates thoracic from abdominal cavities.

  • Consists of a central tendon with muscle fibers.

Page 14: Diaphragm Attachments

Crura of Diaphragm

  • Anchored to lumbar vertebrae by musculotendinous crura.

    • Right Crus: Attached to L1-L3 and intervertebral discs.

    • Left Crus: Attached to L1 and L2.

Page 15: Diaphragm Ligaments

Tendinous Arches

  • Median arcuate ligament connects crura across midline anterior to the aorta.

  • Medial Arcuate Ligament: Above psoas major, attached to L1 and L2 vertebrae.

Page 16: Lateral Arcuate Ligament

Description

  • Formed by fascia over quadratus lumborum.

  • Attached medially to transverse process of L1 and laterally to rib XII.

Page 17: Structures Passing through Diaphragm

Openings at Specific Levels

  • T12: Aorta, thoracic duct, sometimes azygos vein.

  • T10: Esophagus, anterior & posterior vagal trunks.

  • T8: Inferior vena cava, right phrenic nerve.

Page 18: Additional Structures around Diaphragm

  • Splanchnic Nerves: Greater, lesser, and least nerves through the crura.

  • Hemi-Azygos Vein: Passes through the left crus.

  • Sympathetic Trunks: Posterior to medial arcuate ligament.

  • Vessels & Nerves: Musculophrenic vessels and intercostal nerves through diaphragm.

Page 19: Blood Supply of Diaphragm

Arterial Supply

  • Superior: Musculophrenic and pericardiacophrenic arteries (branches of internal thoracic artery), superior phrenic artery (a branch of the thoracic aorta).

  • Inferior: Inferior phrenic arteries (branches of abdominal aorta).

Page 20: Innervation of Diaphragm

Neural Supply

  • Primarily by Phrenic Nerves: Originating from C3 to C5 spinal levels.

  • Provides all motor innervation and sensory fibers to the central part.

  • Additional Sensory Fibers: Supplied by intercostal nerves.