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Abdominal wall and inguinal region
Areas of the abdomen
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Abdominal walls are dynamic, multi-layered, musculo-aponeurotic
Contract to increase intra-abdominal pressure and distend to accommodate
expansion due to ingestion, pregnancy, fat deposition, pathology etc
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Forms superior and major part of abdominopelvic cavity extending between
the thoracic and pelvic diaphragm
No floor as continuous with pelvic cavity; plane of pelvic inlet separates them
Extends superiorly into the thoracic cage (4th intercostal space); more superior
organs thus protected by the ribs (liver spleen, partial kidneys, stomach)
Greater pelvis partially protects lower abdominal viscera (part of ileum,
cecum, appendix, sigmoid colon)
Location of most digestive organs, part of urogenital system and spleen
Nine regions delineated by four planes; two sagittal and two transverse
o Sagittal – midclavicular to midinguinal on each side
o Transverse
 Subcostal (10th costal cartilage)
 Transtubercular (iliac tubercles)
Abdominal wall subdivided into anterior, right and left lateral and posterior
wall - musculoaponeurotic, except for posterior wall

Image taken from Moore et al, Clinically Oriented Anatomy, Seventh Edition
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Features of the anterolateral abdominal wall
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Extends from the thoracic cage to the pelvis
Boundaries
o Superior: cartilages of 7-10th ribs and xiphoid process
o Inferior: inguinal ligament and superior margins of pelvic girdle
Comprises skin and subcutaneous tissue, mainly fat, muscles, aponeurosis,
deep fascia, extraperitoneal fat and parietal peritoneum
Skin attached loosely to the subcutaneous tissue but firmly at the umbilicus
Most of the wall comprises three musculotendinous layers (similar to thorax);
with fibre bundles running in different directions

Image taken from Moore et al, Clinically Oriented Anatomy, Seventh Edition
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Muscle
External
oblique
Internal
oblique
Transversus
abdominus

Rectus
abdominis

Origin
External surface of 5-12
ribs
Thoracolumbar fascia,
anterior iliac crest,
connective tissue deep to
inguinal ligament
Internal surface 7-12 costal
cartilages, thoracolumbar
fascia, iliac crest,
connective tissue deep to
inguinal ligament
Pubic symphysis, pubic
crest

Insertion
Linea alba, pubic tubercle,
anterior iliac crest
Inferior border 10-12 ribs,
linea alba, pectin pubis

Innervation
T7-T11 spinal nerves,
subcostal nerve
Thoraco-abdominal
nerves (T6-12), first
lumbar nerve

Linea alba, pubic crest,
pectin pubis

Xiphoid process, 5-7th
costal cartilages

Action
Compress and support
abdominal viscera
Flex and rotate trunk

Compress and support
abdominal viscera

Thoracoabdominal
nerves (T6-12)

Flexes trunk (L vertebrae)
Compresses abdominal
viscera
Controls pelvic tilt
(antilordosis)

Features of the rectus sheath, linea alba and umbilical ring
Rectus sheath
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Strong, incomplete fibrous compartment of rectus abdominus and
pyramidalis muscles
Also contains the superior and inferior epigastric arteries and veins, lymphatics
and thracicoabdominal nerves
Formed from decussation and interweaving of aponeuroses of the flat
abdominal muscles
External oblique aponeurosis contributes to the sheath throughout its length
Superior two thirds of the internal oblique aponeurosis splits into two layers at
the lateral border of the rectus abdominus
o One layer passes anterior to the muscle and the other posterior
o Anterior layer joins the aponeurosis of the external oblique to form
anterior layer of the rectus sheath
In the lower third, the aponeuroses of the three flat muscles all pass anterior to
the rectus abdominus to form anterior layer of rectus sheath
o Thus only thin transverse fascia of the rectus abdominus covers
posteriorly
o Arcuate line demarks the transition

Linea alba
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Fibres of anterior and posterior layers interlace in the median line
Posterior layer of the rectus sheath is also deficient superior to the costal
margin as
o Transversus abdominis is continued superiorly as the transversus thoracis
(lies internal to costal cartilages)
o Internal oblique attaches to costal cartilages
Linea alba narrows inferior to the umbilicus to the width of the pubic
symphysis, and widens superiorly to the width of the xiphoid process
Transmits vessels and nerves to the skin
Contains the umbilical ring in the middle section, underlying the umbilicus

Umbilical ring
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Defect in the linea alba through which the foetal umbilical vessels pass
All layers of the anterolateral wall fuse at the umbilicus

Image taken from Moore et al, Clinically Oriented Anatomy, Seventh Edition
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Functions and actions of the anterolateral abdominal muscles
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Strong expandable support for the anterolateral abdominal wall
Support and protect the abdominal viscera
Compress abdominal contents to maintain/increase intraabdominal pressure
(opposing the diaphragm)
Move trunk and help maintain posture

Neurovasculature
Nerves of anterolateral abdominal wall
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Thoracoabdominal nerves – distal abdominal parts of the anterior rami of T7T11
Lateral thoracic cutaneous branches (T7-T10)
Subcostal nerve (T12)
Iliohypogastric and ilioinguinal (L1)

Vasculature
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Primary vessels are
o Superior epigastric vessels
o Inferior epigastric and deep circumflex iliac
o Superficial circumflex iliac
o Posterior intercostal vessels

Veins
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Intricate subcutaneous plexus drains to
o Internal thoracic vein medially
o Lateral thoracic vein laterally
o Superficial and inferior epigastric vein inferiorly
Veins anastomose with paraumbilical veins centrally
Thoraco-epigastric vein is a lateral superficial channel
Deeper veins accompany the arteries

Image taken from Moore et al, Clinically Oriented Anatomy, Seventh Edition
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Epigastric hernia (through linea alba) occurs in midline
Spigelian hernias occur in the semilunar lines – usually in people
over 40 and associated with obesity
Hernias composed of peritoneum, fatty connective tissue, skin

Surgical incisions
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Longitudinal incisions (e
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medial and paramedical) good for
exploratory operations, giving access to viscera
Oblique and transverse incisions related to muscle fibre
orientation, nearby hard tissue, or minimising nerve damage
o Gridiron (muscle splitting) incision made to access the
McBurnley point (1/3 along from spino-umbilical line) for
appendectomy
Suprapubic incisions at the pubic hairline for gynaecological
and obstetric operations
Transverse incisions can be used for appendectomy
Subcostal incisions provide access to the gallbladder and biliary
ducts on the right and spleen on the left

Internal surface of anterolateral abdominal wall
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Covered with transversalis fascia, extraperitoneal fat and peritoneum
Imfraumbilical part has five umbilical peritoneal folds passing to the umbilicus,
one in the median plane and two on each side
o Median fold from apex of urinary bladder to umbilicus, covers median
umbilical ligament
o Medial folds lateral to the above; cover medial umbilical ligaments
o Lateral umbilical folds, lateral to medial folds, cover inferior epigastric
vessels
Also peritoneal fossae, which are potential herniation sites
o Supravesical fossae between the median and medial umbilical folds
o Medial inguinal fossae between medial and lateral fold (also known as
inguinal triangles) – site for direct inguinal hernias
o Lateral inguinal fossae – lateral to lateral umbilical folds, include deep
inguinal ring, site for indirect inguinal hernias
Falciform ligament extends between the superior anterior abdominal wall
and liver; encloses round ligament (remnant of umbilical vein) and paraumbilical veins

Image taken from Moore et al, Clinically Oriented Anatomy, Seventh Edition
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I

Inguinal canal
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Formed in relation to relocation of the testes during development
Oblique passage, ~4cm long, directed inferomedially through the inferior part
of the anterolateral abdominal wall
o Parallel and superior to the medial half of the inguinal ligament
Mainly occupied by the spermatic cord (males) and round ligament
(females), plus blood vessels, lymphatics, and ilio-inguinal nerve
Deep internal inguinal ring is entrance to the canal in the transversalis fascia;
located superior to middle of the inguinal ligament and lateral to inferior
epigastric artery
Superficial external inguinal ring is the exit of the canal; spilt in the external
oblique aponeurosis superolateral to the pubic tubercle
Parts of aponeurosis lateral and medial to the superficial ring are the crura
o Lateral crus attaches to pubic tubercle
o Medial crus attaches to pubic crest
o Intercrural fibres pass from one crus to the other – structural support
Inguinal canal has two walls (anterior and posterior), a roof and a floor
o Anterior wall: external oblique aponeurosis
o Posterior wall: transversalis fascia
o Roof: transversalis fascia, internal oblique, transversus abdominus, and
external oblique aponeurosis
o Floor: ilipubic tract, inguinal ligament and lacunar ligament
Most groin hernias in males pass superior to the iliopubic tract (inguinal hernia)
while most in females pass inferior to it (femoral hernias)

Image taken from Moore et al, Clinically Oriented Anatomy, Seventh Edition
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Superficial perineal pouch
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Potential space between the perineal fascia and perineal membrane
In females, contains
o Clitoris, bulb of vestibule and greater vestibular glands
o Ischiocavernous, bulbiospongious and superficial transverse
perineal muscles
o Branches of internal pudendal vessels and nerves
In males, contains
o Root of penis and bulbous part of spongy urethra
o Ischiocavernous, bulbiospongous, and superficial transverse
perineal muscles
o Branches of internal pudendal vessels and nerves

Deep perineal pouch
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Bounded inferiorly by the perineal membrane, superior by the inferior
fascia of the pelvic diaphragm and laterally by the obturator fascia
Includes fat filled anterior recesses of the ischioanal fossae
Contains part of the following in both sexes
o Urethra
o External urethral sphincter muscle
o Ischio-anal fat pads
In males it also contains
o Intermediate urethra
o Deep transverse perineal muscles
o Bulbo-urethral glands
o Neurovasculature of the penis
In women it also contains
o Proximal urethra
o Smooth muscle associated with the perineal body
o Neurovasculature of the clitoris

Image taken from Moore et al, Clinically Oriented Anatomy, Seventh Edition
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Features of anal triangle
Ischioanal fossae
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Large, fascia lined, wedge-shaped spaces between skin of the anal
region and the pelvic diaphragm
Filled with fat and loose connective tissue
Two spaces communicate via deep postanal space over the
anococcogeal ligament (between anal canal and coccyx)
Boundaries
o Lateral: ischium, obturator internus, obturator fascia
o Medial: internal anal sphincter, levator ani, anal canal
o Posterior: sacrotuberous ligament, gluteus maximus
o Anterior: pubic bones; anterior recesses of the ischioanal fossae
Each fossa is filled with a fat body; support anal canal and readily
displaced to permit expulsion of faeces
o Traversed by tough fibrous bands and neurovasculature

Image taken from Moore et al, Clinically Oriented Anatomy, Seventh Edition
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Moore et al
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Seventh Edition

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