which is the remnant of the intra-abdominal part of the allantois. (The allantois forms the urachus which in the fetus, extends from the apex of the bladder to the umbilicus.) The lateral umbilical ligaments are the remnants of the oblit-erated umbilical arteries, which in the fetus, carry blood to the placenta. These ligaments raise the medial umbilical folds of the peritoneum.
The lateral umbilical folds are formed by the inferior epigastric vessels. (Note that there are five folds, but only three ligaments, as the two lateral folds are raised by arteries.)
Arrangement of structures in the groin
The anterior and posterior abdominal walls meet each other at the groin, and their fascial linings—
the transversalis fascia and iliac fascia—become continuous [Fig. 8.11]. The muscles of the anterior abdominal wall end at the inguinal ligament.
The transversalis and iliac fasciae fuse with each other at the lateral part of the inguinal ligament.
Structures of the posterior abdominal wall enter the thigh deep to this line of fusion [Figs. 8.7, 8.11,
Transversalis fascia (cut edge)
Inferior epigastric vessels Extraperitoneal fascia
Parietal peritoneum
Median umbilical ligament (urachus)
Medial umbilical ligament (obliterated part of umbilical artery)
Urinary bladder Pectineal ligament Lacunar ligament
Inguinal ligament
Fig. 8.10 The parietal peritoneum deep to the anterior abdominal wall, with the umbilical folds and ligaments.
This figure was published in Atlas of Human Anatomy 6th Edition, Frank H Netter. Copyright © 2014, Elsevier Inc. All rights reserved. www.netterimages.com.
Aorta Psoas major
Femoral N.
Lumbosacral trunk
Obturator N.
Sciatic N. Lacunar ligament Femoral canal
Cut edge of external oblique aponeurosis Inguinal ligament Femoral N.
Femoral sheath lliacus
lliacus fascia
Common iliac A
Fig. 8.11 A diagram to show the structures in the inguinal region and the nerves of the lower limb related to the pelvis.
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The anterior abdominal wall
all of the sheath is filled by the femoral vessels. Its medial part is a loose connective tissue space—the femoral canal. The femoral canal is filled with fat, some lymph vessels, and an occasional lymph node.
The femoral canal allows for distension of the femo-ral vein. The sharp latefemo-ral edge of the lacunar liga-ment lies medial to the femoral canal.
Inguinal canal
The inguinal canal is an intermuscular passage parallel to, and immediately superior to, the me-dial half of the inguinal ligament [Figs. 8.14, 8.15].
It is the space through which the testis descends from within the abdominal cavity to the scrotum during intrauterine life. The canal therefore con-tains the duct of the testis (the vas deferens), blood and lymph vessels, and nerves of the testis. Togeth-er these structures constitute the spTogeth-ermatic cord.
The inguinal canal has an anterior wall, a floor, a posterior wall, and a roof. The canal also has two openings through which the contents pass—the deep and superficial inguinal rings.
The floor of the inguinal canal is formed by the inguinal and lacunar ligaments [Fig. 8.7]. The anterior wall is formed by the aponeurosis of the external oblique and the internal oblique, deep to the external oblique in the lateral 1 cm. The roof is formed by the lower fibres of the transversus abdominis and the internal oblique arching over the spermatic cord [Fig. 8.6]. The posterior wall is 8.12, 8.13]. These structures include the iliacus
and psoas muscles, the femoral nerve, and the lateral cutaneous nerve of the thigh. They lie behind the iliac fascia and descend into the thigh, posterior to the lateral half of the ligament.
Behind the medial part of the inguinal ligament, the external iliac vessels of the abdomen are contin-uous with the femoral vessels of the thigh. The trans-versalis and iliac fasciae pass down anterior and pos-terior to the femoral vessels, forming a sheath around them—the femoral sheath [Figs. 8.11, 8.12]. Not
Internal oblique Rectus abdominis Inferior epigastric A.
Transversus abdominis
Transversalis fascia Deep inguinal ring Deep circumflex iliac A.
Femoral N.
External iliac vessels Fat in femoral canal Psoas major
Pectineal ligament
Spermatic cord Aponeurosis of external oblique Inguinal ligament Conjoint tendon Pubic branch of inferior epigastric A.
Lacunar ligament Pubic branch of obturator A.
Fig. 8.12 Posterior surface of the anterior abdominal wall in the inguinal region. Note the pubic branches of the obturator and inferior epigastric arteries.
Transversalis fascia Transversus abdominis Internal oblique External oblique Membranous layer of superficial fascia Superficial epigastric V.
Fatty layer of superficial fascia Skin
Spermatic cord Inguinal ligament
Fascia iliaca
Psoas major Femoral V.
External iliac V.
Femoral sheath
Deep fascia of thigh
Fig. 8.13 Sagittal section along the external iliac and femoral veins to show the fasciae and muscles of the inguinal region.
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Inguinal canal
matic fascia, and that from the internal oblique is the cremaster muscle and cremasteric fascia.
The superficial inguinal ring is a defect in the exter-nal oblique aponeurosis (anterior wall of the caexter-nal), through which the testis descends into the scrotum.
It lies immediately superolateral to the pubic tuber-cle [Fig. 8.3]. The external spermatic fascia cov-ering the testis and spermatic cord arises from the margins of the superficial inguinal ring. The sper-matic cord comes to lie anterior to the pubis, deep to the membranous layer of the superficial fascia, as it descends into the scrotum.
In the female, the ovary remains intra-abdom-inal and the inguintra-abdom-inal canal is small, containing only the round ligament of the uterus, the homo-logue of the gubernaculum testis in the male. As such, inguinal hernias are much more common in the male than in the female (see also Clinical Application 8.1).
When the muscles of the anterior abdominal wall contract, the aponeurosis of the external oblique is pulled firmly against the taut conjoint tendon. The contraction of the fibres of the internal oblique and transversus which form the conjoint tendon pulls the arched roof of the canal downwards and narrows the deep ring and the canal. Thus the tendency of a hernia to occur through the canal is reduced as the intra-abdominal pressure rises.
(A hernia is an abnormal protrusion of abdominal contents through the abdominal wall.)
formed by the transversalis fascia laterally and the conjoint tendon medially.
The deep inguinal ring is an opening or a defect in the transversalis fascia (posterior wall), through which the testis enters the inguinal region in the fetus [Figs. 8.10, 8.12]. It lies immediately superior to the inguinal ligament, at the mid-inguinal point, lateral to the inferior epigastric artery [Figs. 8.10, 8.12]. At this point, the descending testis carries part of the transversalis fascia and the most me-dial fibres of the internal oblique muscle before it [Fig. 8.8]. These extensions form the coverings for the testis and spermatic cord. The covering derived from the transversalis fascia is the internal
sper-External oblique aponeurosis
Conjoint tendon
Internal oblique Cremaster M.
Inguinal ligament Superficial inguinal
ring and reflected ligament Spermatic cord
Fig. 8.14 A diagram of the inguinal canal to show the conjoint tendon and the internal oblique muscle. Note that the internal oblique muscle arches over the spermatic cord and sends fibres (the cremaster muscle) on to it.
External oblique
Internal oblique
Anterior superior iliac spine
Transversus abdominis
Aponeurosis of external oblique (reflected) Internal spermatic fascia on spermatic cord
Transversalis fascia Aponeurosis
of external oblique (reflected)
Internal oblique
Inferior epigastric A.
Conjoint tendon
Fig. 8.15 Deep dissection of the inguinal region. Parts of the internal and external oblique muscles have been reflected. The spermatic cord and internal spermatic fascia are cut across.
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The anterior abdominal wall
Branches of the internal thoracic artery
(1) The superior epigastric artery enters the rec-tus sheath, deep to the seventh costal cartilage.
It lies deep to the rectus abdominis, supplies that muscle, and sends branches through it to the over-lying skin. It anastomoses with the inferior epigas-tric artery.
(2) The musculophrenic artery runs along the up-per surface of the costal origin of the diaphragm to the eighth intercostal space. It gives branches to the diaphragm and anterior abdominal wall.