This section is from the book "Anatomy Of The Arteries Of The Human Body", by John Hatch Power. Also available from Amazon: Anatomy of the Arteries of the Human Body, with the Descriptive Anatomy of the Heart.
The Sciatic Or Ischiatic Artery, smaller than the glutaeal, descends on the front of the sacral plexus of nerves and pyriformis muscle: in this course it passes between the rectum and outer wall of the true pelvis, and is accompanied by the pudic artery, which is at first somewhat external to it, and then crosses in front of it and to its inside, opposite the spine of the ischium. In company with the pudic artery, and with the greater and lesser sciatic nerves, it escapes from ternus. 51, The Patella. 52, The Ligamentum Patellae. 53, External Lateral Ligament of Knee joint. 54, The Plantaris. 55, 55, 55, The Gastrocnemius. 56. 56, The Soleus. 57, The Peroneus Longus. 58, Extensor Digitorum Longus. 59, The Glutaeal Artery. 60. 61, 61, Branches of the Glutaeal Artery. 62, The Sciatic Artery. 63, Coccygeal Branch of the Sciatic Artery. 64, 64, Comes Nervi Ischiatici: there are two in this dissection. 65. Muscular Twig for Quadratus Femoris and Gemelli. 66. Descending Branch of the Hamstring Muscles. 67, Branch for the Adductors. 68, 69, 70, 70, External or Inferior Haemorrhoidal Artery and Anastomoses. 71, First Perforating Artery. 72, 73, Anastomosis between the External Circumflex and first Perforating Artery. 74, Small Branch from the first Perforating Artery, for the Sciatic Nerve. 75, 75, 75. Muscular Twigs from first and second Perforating Arteries. 76. Third Perforating Artery. 77, Popliteal Artery. 78. Superior External Articular Artery of Knee. 79, 79, 79, Sural Arteries, and Branch for Posterior Saphena Vein. 80, Inferior External Articular Artery of Knee. 81, Branch from the Anterior Tibial Recurrent Artery the pelvis through the inferior part of the great sacro-sciatic notch, passing between the lower edge of the pyriformis muscle and the lesser sacro-sciatic ligament. After its exit from the pelvis it is covered by the glutaeus maximus muscle, and is situated posterior and then internal to the great sciatic nerve: it lies behind the spinous process of the ischium near its root, and passes also behind the gemelli, obturator internus, and quadratus femoris muscles. While within the pelvis it gives small branches to the bladder, rectum, uterus, and levator ani muscle: after it leaves the pelvis, it terminates by giving off the following branches:
* Dublin Journal, vol. iv. p. 231.
Muscular. Comes Nervi Ischiatici.
The Muscular Branches are distributed to the glutaeus maximus, quadratus femoris, and hamstring muscles.
The Coccygeal Branch passes inwards, and in so doing runs across the posterior surface of the pudic artery, and then passes between the origins of the greater and lesser sacro-sciatic ligaments: it supplies the glutaeus maximus, levator ani, and coccygeus muscles, and periosteum of the coccyx, and anastomoses with the anterior spinal and with the middle and lateral sacral arteries.
The Comes Nervi Ischiatici at first descends along the internal margin of the great sciatic nerve, and then penetrates its substance. Boyer found this branch as large as the radial at the wrist, in a subject that Dessault had operated on eight months before for popliteal aneurism. I have found it in a young child fully as large; and when it had reached the popliteal space it took the place of the popliteal artery: in this case the femoral artery was so very small as to be nearly rudimentary.