Inferior Lateral or Ilio-inguinal Region.
Passing from without inward we find: The skin; the subcutaneous layer; the prolongation of the cellular layer which covers the fibres of the external oblique; the tendinous in sertion of the external oblique; the femoral arch; fibres forming the fibrous, or 'true fascia transversalis; often, but not always, a cellular layer which forms the fascia transversalis; the peritoneum; the epigastric, the circumflex, the iliac and the abdominal cutaneous arteries. The nerves are of little importance; the lymphatics proceed to the ganglia lying above the femoral arch, and to the iliac ganglia. (Richet.) Just below and to the inside of the pubic spine, and between this spine and the symphysis, the aponeurosis of the external oblique divides into two diverging bands, which enclose an oval opening; this is the in guinal ring, the external orifice of the inguinal canal. This canal is deep within the musculo-aponeurotic sheath of the abdomen, just above the femoral arch, which forms its inferior wall. It is traversed by a round ligament, which, in the foetus, is accompanied by the peritoneum, thus forming a cul-de-sac called Nuck's canal. (Tarnier.) The Muscles of the Internal Su? face of the Pelvis.
The internal surface of the pelvis is covered with very important mus cles which modify its character and form. They are: The Psoas and lliacus Muscles.—A pair of muscles, which fill the grooves on each side of the promontory, and the internal iliac fosse. Composed of two bundles, the psoas and iliacus, which form a single muscle, arises, on each side, by its psoas fascia from the lateral and superior parts of the body of the lumbar vertebrae and the last dorsal; by its iliac portion from the whole of the internal surface of the internal iliac fossa; then the fascia as a whole passes over the ilio-pectinal eminence, and a part of the horizontal ramus of the pubes, below the femoral arch, and in serts into the trochanter of the femur. Sometimes a small part of the fascia separates from the superior end of the psoas, and is attached at the ilio-pectinal eminence: this is the psoas parvus.
An aponeurosis, called the fascia iliaca, covers the psoas-iliac muscles. It is placed above and outside the ilio-lumbar ligament, below the femoral arch, and the aponeurosis of the fascia lata of the thigh.
It divides into two layers: a deep and a superficial, which form a sheath for the iliac vessels and lymphatic glands.
Along the internal edge of the muscle the external iliac artery and vein are found.
Between the promontory and the sacro-iliac synchondrosis the common iliac artery and vein pass, also the upper part of the internal iliac artery and vein.
The left lateral part of the iliac muscle is covered by the colon, the right lateral part by the crecuin; the rectum begins above and to the left. Finally, in front, is the bladder, and laterally the peritoneum.
To this region belong the femoral and genito-crural nerves, which arise from the lumbar plexus.
The crural nerve springs from the second, third and fourth lumbar nerves, which make a sharp angle to form it. It crosses the psoas along its external edge, being placed between the iliac muscle and the fascia iliaca; it then passes under the femoral arch, separated above from the iliac vessels by the entire thickness of the psoas; it approaches it below, and is separated from it by only a fibrous partition, a portion of the fascia iliaca.
Tho genito-crural nerve is the lowest of the branches of the lumbar plexus; it crosses the psoas on the level of the vertebral insertions, do. scending the length of the common and external iliac arteries, and divides, either on the level of the ligament of Fallope, or below it, into an external or femoral branch, or into an internal or genital branch.
In the cavity, the sub-pubic or obturator fosse, are filled by the obtura tor muscles, which are attached partly to the rim of the obturator fossa, then leave the pelvis by the sciatic foramen, and pass to the digital fossa on the greater trochanter.