Posterior Abdominal Wall & Diaphragm Flashcards
What are the bones of the posterior abdomen?
LV1-LV5 + their intervertebral discs, ribs 11-12, the sacrum, and the ala (wing) of the sacrum
What are the lumbar vertebrae like?
Large vertebral bodies, with short, stocky pedicles, long transverse processes, and large spinous processes. Their articular facets interlock.
How does the ilium articulate with the sacrum?
At the sacro-iliac joint. The upper part of each ilium articulates with the ala - the wing-like transverse process of the sacral vertebrae.
What is the anterior edge of S1 called?
It projects forward and is called the promontory
Where are the floating ribs located in relation to the kidneys?
Rib 11 is posterior to the superior part of the left kidney
Rib 12 is posterior to the superior part of the right and left kidney
What are the muscles of the posterior abdominal wall?
3 (sometimes 4) paired Iliacus Quadratus lumborum Psoas major Sometimes: psoas minor (50%, sometimes only 1 side too)
1 unpaired
Diaphragm
What are the origin, insertion, action, and innervation of psoas major?
Origin: Bodies, discs, and transverse processes of T12 and L1-L5
Insertion: Lesser trochanter of femur
Innervation: Lumbar plexus (L1-L3)
Action:
With iliacus on one side: flexes the thigh.
Acting alone: Flexes trunk laterally
Acting with opposite psoas + iliacus: Flexes trunk
What is the course of the psoas major muscle?
T12-L5 vertebral column, goes inferolaterally and its tendon runs posterior to the inguinal ligament and anterior to the hip joint to reach femur
What are the origin, insertion, action, and innervation of psoas minor?
Short belly and long tendon like palmaris longus. Lies anterior to psoas major
Origin: T12-L1 vertebrae
Insertion: Iliopubic eminence on pelvic rim
Innervation: L1
Action: Helps psoas major flex the pelvis and lumbar region of vertebral column
What are the origin, insertion, action, and innervation of iliacus muscle?
Lateral and inferior to p. major. Fibers cross sacroiliac joint
Origin: Superior 2/3 of iliac fossa
Insertion: Lesser trochanter of femur, fibers join tendon of psoas major muscle
Innervation: Femoral nerve L2-L4
Action: Flexes thigh, stabilizes hip joint with p. major
What is the iliopsoas muscle?
The name for the psoas major and iliacus muscles together. They are referred to together because they share a common tendon and are the chief flexors of the thigh, helping to maintain erect posture at the sacroiliac joint.
They have extensive relations to the kidneys, ureters, cecum, appendix, sigmoid colon, pancreas, lymph nodes, lumbar plexus, etc
What is a psoas abscess?
An abscess resulting from tuberculosis in the lumbar region which could spread through the fascia enclosing the p. major muscle and pass inferiorly over the pelvic brim into the femoral triangle.
What are the origin, insertion, action, and innervation of quadratus lumborum?
Square muscle which forms a sheet in abdominal wall.
Origin: Transverse processes of L1-L5, medial half of inferior border of 12th rib
Insertion: Iliolumbar ligament and internal lip of iliac crest
Innervation: T12, L1-L4
Action: Extends and laterally flexes the vertebral column, fixes 12th rib during inspiration
What is the iliolumbar ligament?
Strong triangular ligament that connects the tips of LV5 to the iliac crest
What parts of the diaphragm move during inspiration?
Only its dome because the peripheral parts are attached to the inferior margin of the osteocartilagenous thoracic cage and superior lumbar vertebrae.
It moves down during inspiration -> contraction. Forms the floor of the thoracic cavity and roof of abdominal cavity
What are the three parts of the muscular part of the diaphragm? Where do they collectively attach?
- Sternal
- Costal
- Lumbar
They all attach to the central tendon
What is the sternal part of the diaphragm and what hypothetical space is found here?
Two muscular slips attaching to posterior aspect of xiphoid process. They converge on the central tendon, and lateral to each slip is a gap known as the sternocostal hiatus - contains superior epigastric artery
What is the costal part of the diaphgram and what is the vertebrocostal triangle?
Fibers making a dome which originate from the inferior six ribs and their costal cartilages on each side. Ribs 11/12 is separated from lumbar part by the vertebrocostal triangle, which is normally filled by loose connective tissue
What forms the lumbar part of the diaphragm and what vertebral levels are the major landmarks?
Two musculotendinous crura (legs) which form aortic hiatus
Disc between TV12 and LV1 = median arcuate ligament, from which originate the left and right crura
Right crus - extends down to LV3
Left crus - extends down to LV2
What is median vs medial vs lateral arcuate ligaments?
Median - origin of left and right crus, around aortic hiatus
Medial - Thickening of psoas fascia over the superior part of p. major. The muscle fibers radiate towards central tendon
Lateral - thickening of thoracolumbar fascia over superior quadratus lumborum, extending towards central tendon
What is the central tendon of the diaphragm fused with, and what does it resemble?
Central tendon is fused with inferior surface of fibrous pericardium. It resembles a clover leaf from the three areas of thickened fascia
Where is the diaphragm prone to herniation, and what is the most common spot? When does this happen?
Prone to herniation wherever muscles fuse, since it is formed by the fusion of various muscles. This happens when there is increased thoracic or abdominal pressure often during car accident.
Common spot: Vertebrocostal triangle, since it is where muscle fibers of costal and lumbar diaphragm fuse.
Where do congenital hernias most often happen and what structures can enter into the thorax?
Esophageal opening or stenocostal hiatus
-stomach, intestines, and spleen can herniate through
What are the three diaphragmatic aperatures through which things pass, and what vertebral levels are they at?
- Vena caval foramen - TV8
- Esophageal hiatus - TV10
- Aortic hiatus - TV12
What is the vena caval foramen and how is it affected during inspiration?
It is at TV8 where the IVC descends into the abdomen. Since the IVCC is adherent to the margin of the caval opening, inspiration widens the foramen, dilating the IVC
What structure forms the esophageal hiatus and why is this relevant to function?
The right crus does, at the TV10 level. It also forms the esophageal sphincter, which constricts the distal end of the esophagus during inspiration so gastric contents do not reflux into the esophagus
What structures pass through the esophageal hiatus?
Esophagus, anterior and posterior vagal trunks