Download Abdominal Wall and Cavity

Abdomen
Muscles of abdominal wall
• Rectus abdominus-vertical midline
• Three layers form tube
– External oblique
(“hands-in-pocket”)
– Internal oblique (fibers
perpendicular to
external)
– Transverse abdominus
(wraps around)
Muscles of abdominal wall--details
External Oblique
• It arises from eight fleshy digitations, each from the
external surfaces and inferior borders of the fifth to
twelfth ribs
• Those from the lowest ribs pass nearly vertically
downward, and are inserted into the anterior half of
the outer lip of the iliac crest; the middle and upper
fibers, directed downward (inferiorly) and forward
(anteriorly), become aponeurotic at approximately
themidclavicular line. This aponeurosis formed from
fibres from either side of the external oblique
decussates at the linea alba.
External oblique
• The external oblique muscle is innervated by
ventral branches of the lower 6 intercostal
(thoracoabdominal) nerves and the subcostal
nerve on each side
Ext oblique - Action
• The external oblique functions to pull the
chest downwards and compress the
abdominal cavity, which increases the intraabdominal pressure as in a valsalva maneuver.
It also has limited actions in both flexion and
rotation of the vertebral column. One side of
the obliques contracting can create lateral
flexion. It also contributes in compression of
abdomen.
Internal oblique
• The internal oblique muscle (of the abdomen)
is the intermediate muscle of the abdomen,
lying just underneath the external oblique and
just above (superficial to) the transverse
abdominal muscle.
Internal oblique
• Its fibers run perpendicular to the external
oblique muscle, beginning in the thoracolumbar
fascia of the lower back, the anterior 2/3 of the
iliac crest (upper part of hip bone) and the lateral
half of the inguinal ligament. The muscle fibers
run from these point superiomedially (up and
towards midline) to the muscle's insertions on
the inferior borders of the 10th through 12th ribs
and the linea alba (abdominal midline seam).
Internal oblique
• The internal oblique is innervated by the
lower intercostal nerves, as well as
the iliohypogastric nerve and the ilioinguinal
nerve.
• The internal oblique performs two major
functions.
 First, it acts as an antagonist (opponent) to the
diaphragm, helping to reduce the volume of the
thoracic (chest) cavity during exhalation.
 Secondly, its contraction rotates and side-bends the
trunk by pulling the rib cage and midline towards the
hip and lower back, of the same side.
Transverse abdominis
• Deep to (layered below)
the internal oblique
muscle.
Transverse abdominis
• It arises, as fleshy fibers, from the lateral third of
the inguinal ligament, from the anterior three-fourths
of the inner lip of the iliac crest, from the inner
surfaces of the cartilages of the lower six ribs,
interdigitating with the diaphragm, and from the
lumbodorsal fascia.
• The muscle ends anteriorly in a broad aponeurosis, the
lower fibers of which curve inferomedially (medially
and downward), and are inserted, together with those
of the internal oblique muscle, into the crest of
the pubis and pectineal line, forming the
inguinal aponeurotic falx, also called the conjoint
tendon.
Transverse abdominis
• The transversus abdominis is innervated by
the lower intercostal nerves
(thoracoabdominal, nerve root T7-T11), as
well as the iliohypogastric nerve and
the ilioinguinal nerve.
• The transversus abdominis (TVA) helps to
compress the ribs and viscera, providing
thoracic and pelvic stability.
Rectus abdominis
• The rectus abdominis muscle, also known as the
"6-pack," is a paired muscle running vertically on
each side of the anterior wall of the human
abdomen.
• There are two parallel muscles, separated by a
midline band of connective tissue called thelinea
alba (white line). It extends from the pubic
symphysis/pubic crest inferiorly to
the xiphisternum/xiphoid process and lower
costal cartilages (5–7) superiorly.
• It is contained in the rectus sheath.
Rectus abdominis
• The rectus is usually crossed by three fibrous
bands linked by the tendinous intersections.
While the "sixpack" is by far the most
common configuration of the muscle bellies of
the rectus, there exist rare anatomic variations
which result in the appearance of eight
("eightpack"), ten, or asymmetrically arranged
segments. All these variations are functionally
equivalent.
Rectus abdominis
• The rectus abdominis is an important postural
muscle. It is responsible for flexing the lumbar
spine, as when doing a "crunch". The rib cage is
brought up to where the pelvis is when the pelvis
is fixed, or the pelvis can be brought towards the
rib cage (posterior pelvic tilt) when the rib cage is
fixed, such as in a leg-hip raise.
• The muscles are innervated by thoracoabdominal
nerves, which pierce the anterior layer of
the rectus sheath.
Rectus sheath
• The Rectus sheath is formed by the
aponeuroses of the Obliqui and Transversus. It
contains the Rectus abdominis and
Pyramidalis muscles.
• It can be divided into anterior and posterior
laminae.
Region
Above the arcuate line
Below the arcuate line
Description
•At the lateral margin of the Rectus, the
aponeurosis of the Obliquus
internus divides into two lamellae:one
of which passes in front of the Rectus,
blending with the aponeurosis of the
Obliquus externus.
•the other, behind it, blending with the
aponeurosis of the Transversus, and
these, joining again at the medial
border of the Rectus, are inserted into
the linea alba.
Below this level, the aponeuroses of all
three muscles (including the internus)
pass in front of the Rectus.
Muscles of
Posterior
Abdominal Wall
Quadratus Lumborum
• It arises by aponeurotic fibers from
the iliolumbar ligament and the adjacent
portion of the iliac crest for about 5 cm., and
is inserted into the lower border of the
last rib for about half its length, and by four
small tendons into the apices of the transverse
processes of the upper four lumbar vertebrae.
Quadratus Lumborum
• The quadratus lumborum can perform four
actions:
1. Lateral flexion of vertebral column,
with ipsilateral contraction
2. Extension of lumbar vertebral column, with
bilateral contraction
3. Fixes the 12th rib during forced expiration
4. Levates ilium, with ipsilateral contraction
Psoas major
• The psoas major is a long fusiform muscle
located on the side of the lumbar region of
the vertebral column and brim of the lesser
pelvis. It joins the iliacus muscle to form
the iliopsoas. In less than 50 percent of
human subjects the psoas major is
accompanied by the psoas minor.
Psoas major
• The psoas major originates from the transverse
processes of lumbar vertebrae I-V, lateral surfaces
of the last thoracic vertebra, lumbar vertebrae IIV, and from neighboring invertebral discs.
• Joined by the iliacus, psoas major forms
the iliopsoas which is surrounded by the iliac
fascia. The iliopsoas runs across the iliopubic
eminence through the muscular lacuna to its
insertion on the lesser trochanter of the femur.
Psoas major
• Innervation of the psoas major is through the
anterior rami of L1 to L3
• As part of the iliopsoas, psoas major
contributes to flexion and external rotation in
the hip joint. On the lumbar spine, unilateral
contraction bends the trunk laterally, while
bilateral contraction raises the trunk from its
supine position.
Inguinal Canal
• The inguinal canal is a passage in the anterior
(toward the front of the body) abdominal wall
which in men conveys the spermatic cord and in
women the round ligament.
• The inguinal canal is situated just above the
medial half of the inguinal ligament.
• Length is approximately 3.75cm
• It is oblique directed inferiorly, anteriorly and
medially.
• Extends between superficial and deep inguinal
rings.
Inguinal Region
• Inguinal Canal:
Superficial inguinal ring:
Triangular defect in the aponeurosis of the
external oblique muscle layer.
Superficial opening of the inguinal canal.
Lies above and lateral to pubic tubercle.
Larger in males:
Transmits spermatic cord in males.
Transmits round ligament of uterus in
females.
Inguinal Region
• Inguinal Canal:
Deep inguinal ring:
Opening of the evagination of the
transversalis fascia.
Lies above inguinal ligament midway between
anterior iliac spine and pubic tubercle.
Margins of the inguinal canal
superior wall (roof):
internal oblique
transversus abdominis
anterior wall:
aponeurosis of external
oblique
aponeurosis of internal
oblique (lateral third of
(inguinal canal)
canal only)
superficial inguinal
ring (medial third of canal
only)
inferior wall (floor):
inguinal ligament
lacunar ligament (medial
third of canal only)
iliopubic tract (lateral
third of canal only)
posterior wall:
transversalis fascia
conjoint tendon (medial
third of canal only)
deep inguinal ring (lateral
third of canal only)
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