Anterior Abdominal wall
THE ABDOMEN
Part of the trunk between the thorax and the pelvis
Flexible & expandable container. What are the contents of the abdomen?
Boundaries of the abdominal cavity
Superiorly: diaphragm
Anteriorly: rectus muscles + their fascia
Anterolaterally: musculoaponeurotic wall
Posteriorly: lumber vertebrae + muscles
Inferiorly: No distinct boundary (continuous with pelvic cavity at the pelvic brim)
abdominopelvic cavity?
ABDOMINAL WALL
Functions
Supports & protects abdominal viscera
Helps to maintain posture
Helps to increase intra-abdominal pressure to facilitate expulsion - defaecation and micturition, parturition, vomiting
Some muscles of the wall acts as accessory muscles during forced expiration
Flex and rotate the trunk
ABDOMEN
ABDOMINAL REGIONS
Four abdominal quadrants & nine abdominal regions are clinically important for describing the position of a mass, localization of a patient’s pain or the location of abdominal viscera
The quadrants are formed by median & transumbilical planes
The 9 regions are formed by 2 midclavicular planes, subcostal plane (10th costal cartilage; at L3 vert. level) or transpyloric plane (L1) & transtubercular planes (L5 vert. level) or interspinous plane
NB: The midclavicular passes the midinguinal point
ABDOMEN
4 abdominal quadrants
right upper quadrant
left upper quadrant
right lower quadrant
left lower quadrant
ABDOMEN
ANTEROLATERAL ABDOMINAL WALL
Superior Extent
Xiphoid process & costal margin
Inferior Extent
iliac crest, pubic crest, pubic symphysis, inguinal ligament
ANTEROLATERAL ABDOMINAL WALL
Layers
Skin
Superficial fascia
Muscles + their aponeuroses
Transversalis fascia
Extraperitoneal fat/preperitoneal fat
Parietal peritoneum
Superficial fascia
-Above the umbilicus is a single layer containing variable amount of fat
-Below the umbilicus , it differentiates into Superficial fatty layer (Camper’s fascia) and deep membranous layer (scarpa’s fascia)
--Camper’s fascia
continuous with the superficial fat over the rest of the body. Over the penis, it is devoid of fat, and in the scrotum, it is replaced by dartos muscle
The deep membranous layer (Scarpa fascia)
-Continues with the superficial fascia of the perineum -Colle’s fascia
-Continues over the penis as the superficial fascia of the penis (Buck’s fascia) and over the scrotum as the dartos tunic/layer
-Fuses with deep fascia of thigh (fascia lata), a fingerbreadth below the inguinal ligament
There is no deep fascia in the anterior abdominal wall
Muscles of anterolateral anterior abdominal wall
External oblique muscle
Internal oblique muscle
Transversus abdominis muscle
Rectus abdominis muscle
Pyramidalis muscle – absent in 20% of the population
MUSCLES OF ANTEROLATERAL ABDOMINAL WALL
External oblique
Origin: 5th to 12th ribs
Insertion: linea alba, pubic tubercles, anterior ½ iliac crest
Direction of fibers - inferiomedial
Blood supply: lower posterior intercostal, subcostal, epigastric, circumflex & posterior lumbar arteries
MUSCLES OF ANTEROLATERAL ABDOMINAL WALL
Action: help maintain abdominal tone, to increase intra-abdominal pressure & flex the trunk laterally
Nerve supply: T7-T11 (intercostal n.), T12 (subcostal n.)
NB
contributes to the formation of rectus sheath, superficial inguinal ring, inguinal ligaments (of Poupart), spermatic cord and lumbar triangle
MUSCLES OF ANTEROLATERAL ABDOMINAL WALL
Internal oblique
Origin: Thoracolumbar fascia, anterior 2/3 iliac crest, lateral 2/3 inguinal ligament
Insertion: 10th-12th ribs, linea alba, pectin pubis via conjoint tendon
Direction of fibers - superiomedial
Blood supply: same as external oblique
MUSCLES OF ANTEROLATERAL ABDOMINAL WALL
Action: compress and support abdominal viscera, flex and rotate the trunk
Nerve supply: T7-T11, T12, L1 (iliohypogastric n., ilioinguinal n.)
The splitting of the internal oblique aponeurosis along the lateral border of the rectus muscle forms a relatively shallow groove, called semilunar line.
NB: contributes to the formation of rectus sheath, spermatic cord, conjoint tendon (falx inguinalis) and lumbar triangle.
MUSCLES OF ANTEROLATERAL ABDOMINAL WALL
Transverse abdominis
Origin: Thoracolumbar fascia, iliac crest, lateral 1/3 inguinal ligament, internal surface of 7th-12th costal cartilage
Insertion: linea alba, pubic crest, pectin pubis via conjoint tendon
Blood supply: same as external oblique
ANTEROLATERAL ABDOMINAL WALL
Action: the main muscle for maintaining abdominal tone & increasing intra-abdominal pressure/compressing & supporting abdominal viscera
Nerve supply: same as internal oblique
NB
contributes to the formation of rectus sheath, spermatic cord and conjoint tendon
ANTEROLATERAL ABDOMINAL WALL
Rectus abdominis
Origin: pubic symphysis & pubic crest
Insertion: xiphoid process; 5th-7th costal cartilages
UNIQUE FEATURES:
Segmented; connected by flat tendons = Tendinous intersections
Enclosed in a rectus sheath
Blood supply: mainly superior and inferior epigastric arteries
Action: flexes the trunk; compress abdominal viscera; help maintain abdominal wall tone during straining
Nerve supply: same as external oblique
Pyramidalis
- Small triangular muscle lying anterior on the lower part of rectus abdominis within rectus sheath
-Absent in 20% of people
Attachment: front of the pubis & pubic ligament; linea alba
Blood supply: mainly inferior epigastric artery
Action: Help tense the lower linea alba
Nerve supply: T12 (subcostal n.)
ABDOMINAL WALL
Rectus Sheath
Fibrous compartment for rectus abdominis, pyramidalis muscles, lower six thoracic nerves and their accompanying posterior intercostal vessels, and the superior and inferior epigastric vessels
Formed by the aponeurosis of the trilaminar anterolateral abdominal muscles
ABDOMINAL WALL
Rectus Sheath
Above the umbilicus up to the costal margin, has anterior & posterior layers
Below the umbilicus down to the arcuate line (of Douglas), also has anterior & posterior layers
From the arcuate line downward, only anterior layer is present
The arcuate line is located 1/3rd of the distance from the umbilicus to the pubic crest
ABDOMINAL WALL
Rectus Sheath
ABDOMINAL WALL
Rectus Sheath & Muscle
ABDOMINAL WALL
Transversalis fascia
covers the deep surface of the transversus abdominis muscle
with its various extensions, it forms a complete fascial envelope across the abdominal cavity
binds together the muscle and aponeurotic fascicles into a continuous layer and reinforces weak areas.
responsible for the structural integrity of the abdominal wall
a hernia results from a defect in the transversalis fascia.
lower thickened part of the transversalis fascia, between the iliac crest and pubis just above the inguinal ligament, form the iliopubic tract.
Together with the fascia iliaca, they form the femoral sheath?
Coverings of spermatic cord
1. Skin
2. Subcutaneous tissue
3. External spermatic fascia: from ext. obl. aponeurosis & its fascia
4. Cremasteric muscle & fascia: from int. obl. muscle & its fascia
5. Internal spermatic fascia: from transversalis fascia
The above layers are also present in the scrotum having dartos muscle
ANTEROLATERAL ABDOMINAL WALL
Blood Vessels
-Superior epigastric arteries (from int. thoracic a.): rect. abd. mm, sup. & deep wall of epigastric & upper umbilical regions.
Inferior epigastric arteries (from ext. Iliac a.): rect. abd mm, deep wall of pubic & inferior umbilical region
-Deep circumflex iliac arteries (from ext. iliac a.): deep wall of inguinal region
-Lower two (10th & 11th ) posterior intercostal arteries (from thoracic aorta)
-Lumbar arteries (from abdominal aorta)
-Subcostal arteries (from thoracic aorta)
Superficial circumflex iliac arteries (from femoral a. ): superficial abd. wall of inguinal region
Superficial epigastric arteries (from femoral a.): superficial abd. wall of pubic and inferior umbilical region.
Superficial external pudendal arteries (from femoral a.)
ANTEROLATERAL ABDOMINAL WALL
Superficial veins within Camper’s fascia
form a network that radiates out from the umbilicus. Above the umbilicus, drain into the axillary vein via the lateral thoracic vein.
Below the umbliicus ,drain into the femoral vein via the superficial epigastric and the great saphenous veins.
Lateral thoracic veins and superficial epigastric veins may anastmose as thoracoepigastric vein to provide collateral circulation between sup. & inf. vena caval systems
A few small veins, the paraumbilical veins, connect the network through the umbilicus and along the round ligament of the liver to the portal vein. This forms an important portal–systemic venous anastomosis.
Deep veins
The deep veins of the abdominal wall, the superior epigastric, inferior epigastric, and deep circumflex iliac veins, follow the arteries of the same name and drain into the internal thoracic and external iliac veins. The posterior intercostal veins drain into the azygos veins, and the lumbar veins drain into the inferior vena cava.
-Deep medial caval venous anastomosis may exist between inf. epigast. vein & sup. epigast. vein for collateral circulation
ANTEROLATERAL ABDOMINAL WALL
Nerves
Thoracoabdominal nerves (T7-T11)
Lateral/thoracic cutaneous nerves (T7-T9)
Subcostal nerve (T12)
Iliohypogastric nerve (L1)
Ilioinguinal nerve (L1)
T7-T9: Skin superior to umbilicus
T10: Skin around umbilicus
T11 and cutaneous branches of T12 & L1 : skin inferior to umbilicus
NB: The neurovascular plane lie between the internal oblique and the transverse abdominis muscles
ANTEROLATERAL ABDOMINAL WALL
LYMPHATIC DRIANAGE OF ANTEROLATERAL ABDOMINAL WALL
ANTEROLATERAL ABDOMINAL WALL
INTERNAL SURFACE
-Transversalis fascia
-Extraperitoneal fat
-Parietal peritoneum
5 umbilical folds occur infraumbilical region
-Median umb. fold (median umbilical ligament
-2 medial umb. fold (medial umb. lig.)
-2 lateral umb. fold (inf. epigastric vv.)
What are the embryonic origins of the median and medial umbilical ligaments?
ANTEROLATERAL ABDOMINAL WALL
INTERNAL SURFACE
The sides of the folds (fossae) are potential sites for hernia
Medial inguinal fossae: Between medial and lateral folds; site for direct inguinal hernia
Lateral inguinal fossae: Lateral to the lateral umbilical fold; site for indirect inguinal hernia
Supravesical fossae: between median & medial folds
INGUINAL REGION
Extends between anterior superior iliac spine and pubic tubercle on either side of the body
Anatomically important because its a region where structures enter & exit the abdominal cavity
Clinically important because it’s an area the pathways of entrance & exit of the anatomical structures are potential sites of herniation
INGUINAL REGION
Inguinal ligament
A dense band of fibrous tissue attached at ASIS and pubic symphysis medially
Formed by the inferiormost part of the external oblique aponeurosis
Important landmark
Lacunar ligament (of Gimbernat)
Pectineal ligament (of Cooper)
INGUINAL REGION
Inguinal Canal
An oblique passage directed inferomedially through the inferior part of the anterolateral abdominal wall
Lies parallel & superior to the inguinal ligament
Approximately 4cm long, from deep inguinal ring to superficial inguinal ring.
In newborns, the canal is directed straight forward
INGUINAL REGION
Internal entry to the canal is called deep (internal) inguinal ring
The external exit of the canal is called superficial (external) inguinal ring
INGUINAL REGION
Superficial inguinal ring
A triangular – shaped defect/Hiatus in the external oblique aponeurosis; lies immediately superior & lateral to the pubic tubercle.
Deep Inguinal Ring
An oval opening in the fascia transversalis; lies 1.25 cm above the midpoint of the inguinal ligament
Is lateral to the inferior epigastric vessels
INGUINAL REGION
Contents of Inguinal Canal
Ilioinguinal nerve (in both sexes)
Enters the canal by piercing the internal oblique muscle, lies in front of the cord and leaves via the superficial ring to supply the skin of the inguinal region, upper part of the thigh, anterior 2/3 of scrotum (labia majora) and root of penis
Spermatic cord (in males)
Round ligament of the uterus (in females)
INGUINAL REGION
Inguinal Canal
The inguinal canal is bordered:
Superiorly/roof: arching lowest fibres of internal oblique and transverses abdominis muscles.
Anteriorly: skin, fascia, external Oblique aponeurosis, reinforced lat’ly by the internal oblique muscle
Floor/inferiorly: inguinal & lacunar ligaments, iliopubic tract
Posteriorly: trans. fascia & medially by conjoint tendon
Femoral Canal
The femoral canal is bordered:
Anterosuperiorly -inguinal ligament
Posteriorly - pectineal ligament (of Cooper’s) lying anterior to the superior pubic ramus
Medially - lacunar ligament
Laterally - femoral vein
Site of femoral hernia
Abnormal obturator artery?
Hernia
Myopectineal orifice (of Fruchaud)
INGUINAL HERNIA
• An inguinal hernia is a protrusion of abdominal viscera (e.g., loops of intestine) into the inguinal canal is termed inguinal hernia.
Clinically it presents as a pear-shaped swelling above and medial to pubic tubercle, above the inguinal ligament
Consists of three parts: the sac, contents of the sac, covering of the sac. Hernial coverings are formed from the layers through which the hernial sac passes
INGUINAL HERNIA
The term complete inguinal hernia (shown in Fig. A) is used if hernia contents reach the tunica vaginalis. If the hernia contents remain confined to inguinal canal and do not pass through superficial inguinal ring it is called incomplete inguinal hernia/bubonocele (shown in Fig. B)
INDIRECT INGUINAL HERNIA
The hernia sac enters the deep inguinal ring, lateral to the inferior epigastric vessels into the inguinal canal.
Neck of the hernia sac is narrow
• It is 20 times more common in young males than females
• Is more common on the right side
May be congenital or acquired. – Congenital indirect inguinal hernia: It occurs due to patent processus vaginalis (an outpouching of the peritoneum), connecting peritoneal cavity with the tunica vaginalis. The hernia is complete and may extend through the superficial inguinal ring down into the scrotum or labium majus.
– Acquired indirect inguinal hernia: It occurs due to increased intra-abdominal pressure as during weight lifting or as a result of an injury.
Direct Inguinal hernia
It composes about 15% of all inguinal hernias
More common in elderly men with weak anterior abdominal muscle.
Very rare in women
Hernia sac bulges forward thru’ posterior wall of inguinal canal, medial to the inf epigastric vessels (Hesselbach’s triangle)
Neck of the hernia sac is wide and hence less likely to strangulated
Anomalies of Testicular Descent
FEMORAL HERNIA
Lumbar triangle site of rare lumbar hernia