Download 29-Posterior Abdomin..

Psoas Major
It arises from the roots of the transverse processes; the sides of the vertebral bodies and
the intervertebral discs from the 12th thoracic to the 5th lumbar vertebrae.
Its fibers run downward and laterally and leave the abdomen to enter the thigh by passing
behind the inguinal ligament.
It is inserted into the lesser trochanter of the femur.
It is enclosed in a fibrous sheath that derived from the lumbar fascia. This sheath is
thickened above to form the medial arcuate ligament.
Nerve Supply: femoral nerve and the ventral rami of L 1, 2, 3 ( lumbar plexus ).
Action : it flexes the thigh at the hip joint on the trunk. If the thigh is fixed, it flexes the trunk
on the thigh, as in sitting up from a lying position.
Quadratus Lumborum
It is a flat, guadrilateral- shaped muscle that
lies alongside the vertebral column.
It arises below from tips of the transverse
processes of the lower lumbar vertebrae; the
iliolumbar ligament and the adjoining part of
the iliac crest.
It is fibers run upward and medially.
is inserted into the transverse processes of
the upper lumbar vertebrae and the lower
border of the 12th rib.
It
Its anterior surface is covered by lumbar
fascia which is thickened above to form the
lateral urcuate ligament and below to form the
iliolumbar ligament.
Nerve Supply:
Lumbar plexus only the ventral rami of L2; 3
and 4
Action: it fixes or depresses the 12th rib during
respiration and laterally flexes the vertebral
column to the same side.
Iliacus
It is a fan shaped and arises from the upper part of the iliac fossa.
Its fibers join the lateral side of the psoas tendon to be inserted into the lesser trochanter of
the femur. The combined muscles are often referred to as the iliopsoas.
Nerve Supply: Femoral nerve ( L2; 3; 4 ) which is a branch from the lumbar plexus.
Action: It flexes the thigh on the trunk at the hip joint. If the thigh is fixed, it flexes the trunk
on the thigh.
Transversus muscle
It is a thin sheet of muscle that lies deep to the internal oblique . Its fibers run
horizontal forward.
It arises from the deep surface of the lower 6 costal cartilages ( interdigitating with
the diaphragm ); the thoracolumbar fascia ; anterior two thirds of the iliac crest
and the lateral third of the inguinal ligament.
It is inserted into the xiphoid process ; linea alba and the symphysis pubis.
Nerve Supply:
Lower 6 thoracic nerves; ilioinguinal and iliohypogastric nerves.
Fascial Lining of the Abdominal Walls
The abdominal walls are lined by one continuous
layer of connective tissue that lies between the
parietal peritoneum and the muscles. It is
continuous below with a similar fascial layer
lining the pelvic wall.
Superiorly: Diaphragmatic fascia which covers
the undersurface of the diaphragm.
The transversalis fascia which lines the
transversus abdominis muscle.
The ilio- psoas fascia which covers the iliacus
and psoas major muscles.
The quadratus lumborum fascia which covers the
the quadratus lumborum muscle. It is the anterior
layer of thoraco- lumbar fascia.
The abdominal blood & lymph vessels lie within
this fascial lining, whereas the principal nerves
lie outside this fascia.
The femoral sheath is a downward prolongation
of this fascia around the femoral vessels and
lymphatic for about 1.5 inch ( 4cm) into the thigh
behind the inguinal ligament. The femoral nerve
lies outside this fascial envelope.
Thoraco-Lumbar Fascia
It forms a strong aponeurosis and
laterally gives origin to the middle
fibers of the transversus abdominis
and the upper fibers of the internal
oblique muscles of the abdominal
wall. It is divided into 3 layers.
1- The posterior layer extends from the
sacrum upward to reach the lower
part of the neck. It covers the back of
the erector spinae muscle. It is
attached to the lumbar spines.
2- The middle layer passes medially to
be attached to the tips of the
transverse processes of the lumbar
vertebrae. It lies in front of the deep
muscles of the back and behind the
quadratus lumborum muscle.
3- The anterior layer passes medially
and is attached to the anterior
surface of the transverse processes
of the lumbar vetebrae. It lies in front
Psoas fascia and Tuberculosis
Tuberculous disease of the
thoracolumbar region of the
vertebral column results in the
destruction of the vertebral bodies.
Pus may spread laterally under the
psoas fascia.
From there, the pus tracks
downward, following the course of
the psoas muscle and appears as a
swelling in the upper part of the
thigh below the inguinal ligament.
This abscess may be mistaken for
femoral hernia.
Diaphragm
It closes the opening between the thorax and the abdomen
which is bounded by xiphisternal joint; the costal margin and
the body of the 12th thoracic vertebra.
It is a muscular and tendinous septum. It is the primary
muscle of respiration.
Diaphragm
It is dome shaped and consists of a peripheral muscular part which arise from 3 parts
A sternal part, consisting of small right and left slips arising from the posterior surface of
the xiphoid process.
A costal part, consisting of 6 slips that arise from the deep surfaces of the lower 6 ribs and
their costal cartilages.
A vertebral part, arising by means of vertical columns or crura and from the arcuate
ligaments.
The right crus arises from the sides of the bodies of the first 3 lumbar vertebrae
and the intervertebral discs.
The left crus arises from the sides of the bodies of the first 2 lumbar vertebrae and
the intervertebral disc.
Lateral to the crura the diaphragm arises from the medial and lateral arcuate
ligaments.
The fibrous medial borders of the 2 crura are connected by a median arcuate
ligament which crosses over the anterior surface of the aorta.
The medial arcuate ligament extends from the side of the body of the 2nd
lumbar vertebra to the tip of the transverse process of the 1st lumbar
vertebra.
The lateral arcuate ligament extends from the tip of the transverse
process of the 1st lumbar vertebra to the lower border of the 12th rib.
The diaphragm is inserted into a central tendon which is shaped like 3
leaves.
The superior surface of the tendon is partially fused with the inferior
surface of the fibrous pericardium.
Some of the muscle fibers of the right crus pass up to the left and surround the
esophageal orifice in a sling like loop.
These fibers appear to act as a sphincter and possibly assist in the prevention of
regurgitation of the stomach content into the thoracic part of the esophagus.
When seen from side, the diaphragm has the appearance of an inverted J.
The long limb extending up from vertebral column and the short limb
extending forward to the xiphoid process.
As seen from in front, the diaphragm curves up into right and left domes or cupolae.
The right dome reaches as high as the upper border of the 5th rib and the left dome reach the
lower border of the 5th rib.
The right dome lies at a higher level, because the large size of the right lobe of the liver.
The central tendon lies at the level of the xiphisternal joint.
The domes support the right and left lungs whereas the central tendon supports the heart.
The levels of the diaphragm vary with the phase of respiration, the posture and the degree
of distension of the abdominal viscera.
The diaphragm is lower when a person is sitting or standing. It is higher in the supine
position and after a large meal.
Opening in the diaphragm
The aortic opening:
It lies anterior to the body of the 12th thoracic vertebra between the crura. It
transmits the aorta; thoracic duct and azygos vein.
Esophageal opening:
It lies at the level of the 10th thoracic vertebra in a sling of muscle fibers derived
from the right crus. It transmits the esophagus; the right and left vagus nerves;
the esophgeal branches of the left gastric vessels and the lymphatics from the
lower third of the esophagus.
Caval opening:
It lies at the level of the 8th thoracic vertebra in the central tendon. It transmits the
inferior vena cava and terminal branches of the right phrenic nerve.
Other Openings:
1- Greater; lesser and lowest splanchnic nerves pierce the crura.
2- Sympathetic trunks pass posterior to the medial arcuate ligament on each side.
3- Superior epigastric vessels pass between the sternal and costal origins of the
diaphragm on each side.
4- Left phrenic nerve pierces the left dome to supply the peritoneum on its
undersurface.
5- Neurovascular bundles of the 7th to 11th intercostal spaces pass into the anterior
abdominal wall between the muscular slips of the costal origin of the diaphragm.
Nerve Supply:
The motor nerve supply on each is from the phrenic nerve ( C3;4 and 5 ) only.
The sensory nerve supply to parietal pleura and peritoneum covering the central surfaces of
the diaphragm is from the phrenic nerve. So, pain is referred to the shoulder & lower part of
the neck ( C 3;4 and 5 nerves ).
The sensory supply to the periphery of the diaphragm is from the lower 6 intercostal nerves.
So, pain is referred to the thoracic & anterior abdominal walls ( lower 6 thoracic nerves ).
Arterial supply:
Phrenic arteries from the aorta & Branches from the intercostal aretries & musculophrenic
and pericardiacophrenic arteries.
Action:
On contraction, the diaphragm pulls down its central tendon and increases the vertical
diameter of the thorax.
Functions of the diaphragm
1- It is the most important muscle used in inspiration.
2- Muscle of abdominal straining:
Its contraction help in raising the intra-abdominal pressure to evacuate the
pelvic contents.
3- Weight – lifting muscle:
By rising intra-abdominal pressure, it will help support the vertebral column
and prevent flexion. It assists the postvertebral muscles in the lifting of heavy
weight. It is important to have adequate sphincteric control of the bladder and
anal canal under these action.
4- Thoracoabdominal pump:
The descent of the diaphragm decreases the intra-thoracic pressure and at the
same time increases the intra- abdominal pressure. This pressure change
compresses the blood in the inferior vena cava and forces it upward into the
right atrium of the heart.
Lymph within the abdominal lymph vessels also is compressed and passed
upward within the thoracic duct. The presence of valves within the thoracic
duct prevents backflow.