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os pubis
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Right hip bone External surface
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The is the
Ventral and
Anterior of the three principal
Bones composing either half of the
Pelvis .
It is covered by a layer of
Fat , which is covered by the
Mons Pubis .
In the female, the pubic bone is anterior to the
Urethral Sponge .
It is divisible into a body, a superior and an inferior ramus.
The Body (corpus oss. pubis).—The body forms one-fifth of the acetabulum, contributing by its external surface both to the lunate surface and the acetabular fossa.
Its internal surface enters into the formation of the wall of the lesser pelvis and gives origin to a portion of the
Obturator Internus .
The Superior Ramus (ramus superior oss. pubis; ascending ramus).—The superior ramus extends from the body to the median plane where it articulates with its fellow of the opposite side. It is conveniently described in two portions, viz., a medial flattened part and a narrow lateral prismoid portion.
The Medial Portion of the superior ramus, formerly described as the body of the pubis, is somewhat quadrilateral in shape, and presents for examination two surfaces and three borders.
The anterior surface is rough, directed downward and outward, and serves for the origin of various muscles.
The
Adductor Longus arises from the upper and medial angle, immediately below the crest; lower down, the
Obturator Externus , the
Adductor Brevis , and the upper part of the
Gracilis take origin.
The posterior surface, convex from above downward, concave from side to side, is smooth, and forms part of the anterior wall of the pelvis. It gives origin to the
Levator Ani and
Obturator Internus , and attachment to the puboprostatic ligaments and to a few muscular fibers prolonged from the bladder.
The upper border presents a prominent tubercle, the pubic tubercle (pubic spine), which projects forward; the inferior crus of the subcutaneous inguinal ring (external abdominal ring), and the
Inguinal Ligament (Poupart’s ligament) are attached to it.
Passing upward and lateralward from the pubic tubercle is a well-defined ridge, forming a part of the pectineal line which marks the brim of the lesser pelvis: to it are attached a portion of the
Inguinal Falx (conjoined tendon of Obliquus internus and Transversus), the
Lacunar Ligament (Gimbernat’s ligament), and the reflected inguinal ligament (triangular fascia).
Medial to the pubic tubercle is the crest, which extends from this process to the medial end of the bone. It affords attachment to the inguinal falx, and to the
Rectus Abdominis and
Pyramidalis .
The point of junction of the crest with the medial border of the bone is called the angle; to it, as well as to the
Symphysis , the superior crus of the subcutaneous inguinal ring is attached.
The medial border is articular; it is oval, and is marked by eight or nine transverse ridges, or a series of nipple-like processes arranged in rows, separated by grooves; they serve for the attachment of a thin layer of cartilage, which intervenes between it and the interpubic fibrocartilaginous lamina.
The lateral border presents a sharp margin, the obturator crest, which forms part of the circumference of the obturator foramen and affords attachment to the obturator membrane.
The Lateral Portion of the ascending ramus has three surfaces: superior, inferior, andposterior. The superior surface presents a continuation of the pectineal line, already mentioned as commencing at the pubic tubercle.
In front of this line, the surface of bone is triangular in form, wider laterally than medially, and is covered by the Pectineus.
The surface is bounded, laterally, by a rough eminence, the iliopectineal eminence, which serves to indicate the point of junction of the ilium and pubis, and below by a prominent ridge which extends from the acetabular notch to the pubic tubercle.
The inferior surface forms the upper boundary of the obturator foramen, and presents, laterally, a broad and deep, oblique groove, for the passage of the obturator vessels and nerve; and medially, a sharp margin, the obturator crest, forming part of the circumference of the obturator foramen, and giving attachment to the obturator membrane.
The posterior surface constitutes part of the anterior boundary of the lesser pelvis.
It is smooth, convex from above downward, and affords origin to some fibers of the
Obturator Internus .
The Inferior Ramus (ramus inferior oss. pubis; descending ramus).—The inferior ramus is thin and flattened.
It passes lateralward and downward from the medial end of the superior ramus; it becomes narrower as it descends and joins with the inferior ramus of the ischium below the obturator foramen.
Its anterior surface is rough, for the origin of muscles—the Gracilis along its medial border, a portion of the Obturator externus where it enters into the formation of the obturator foramen, and between these two, the Adductores brevis and magnus, the former being the more medial.
The posterior surface is smooth, and gives origin to the Obturator internus, and, close to the medial margin, to the
Constrictor Urethræ .
The medial border is thick, rough, and everted, especially in females. It presents two ridges, separated by an intervening space.
The ridges extend downward, and are continuous with similar ridges on the inferior ramus of the ischium; to the external is attached the
Fascia Of Colles , and to the internal the inferior fascia of the urogenital diaphragm.
The lateral border is thin and sharp, forms part of the circumference of the
Obturator Foramen , and gives attachment to the obturator membrane.
