The bony pelvis is a complicated basin-shaped structure that constitutes the pelvic region’s skeletal framework and contains the pelvic organs.
It is mainly divided into two anatomic regions: the pelvic spine and the pelvic girdle. The sacrum and coccyx constitute the pelvic spine, the back of the pelvis located below the lumbar spine. Ilium, ischium, and pubic bone are the three fused bones that comprise the pelvic girdle, usually referred to as the hip bone.
The pubic symphysis connects the two pelvic bones anteriorly, and the sacroiliac joints are formed by their posterior articulation with the pelvic spine.
Table of Contents
- Types of Pelvic Bone
- Pelvic Hip Bones
- Male and Female Pelvic Bone
- Pubic Bone and Its Parts
- Frequently Asked Questions (FAQs)
Types of Pelvic Bone
Both genetic and environmental factors determine the general shape of the pelvis. Researchers in the 1930s identified four different types of pelvic bones.
These pelvis types were mainly developed based on the pelvic inlet shapes, the upper portion of the pelvic cavity. The birth canal begins at the pelvic inlet.
The four types of pelvic bones are as follows:
- Gynecoid: This is the most prominent female pelvis, commonly recognised as the female pelvic bone. It has a basic open, shallow, and rounded shape.
- Android: This type of pelvic bone resembles the male pelvis better. It has a shape similar to a heart or a wedge and is smaller than the gynecoid pelvis.
- Anthropoid: The anthropoid pelvic bone is deep and narrow. It is an upright egg or oval-shaped.
- Platypelloid: The flat pelvis is another name for the platypelloid pelvis. It’s shallow but wide and looks like an oval, or an egg turned sideways. This is the rarest type of pelvic bone.
Greater and Lesser Pelvis
The pelvic inlet is situated in the lesser (true) pelvis, which is smaller and inferior to the greater (false) pelvis.
The ilium forms a border on either side of the greater (false) pelvis. It is incomplete in the front, showing a large gap between the ilia’s anterior borders; in the back, there is a significant gap between the sacrum’s base and ilium on either side.
The superior rami of the pubis and the pubic symphysis form the front and bottom borders of the lesser (or true) pelvis. The coccyx and sacrum are located behind and above.
Pelvic Hip Bones
The hip bone, also termed the innominate bone, pelvic bone, or coxal bone, is a bilateral, irregularly shaped bone of the skeletal pelvis.
It is a composite structure composed of the ilium, ischium, and pubis, three smaller bones. The ischium is situated posteroinferiorly, the pubis or pubic bone constitutes the anterior half of the hip bone, and the ilium is the most superior and the largest element of the bone.
The three parts of the hip bone grow independently and are only joined in children by cartilage. During puberty, they fuse entirely to form intricate and compressed hip bones. The acetabulum, which articulates with the femoral head at the hip joint, is the centre of this union. It is a cup-shaped, deep socket on the lateral surface of the bone.
The hip bones attach anteriorly to the pubis or pubic region and medially to the acetabulum.
Male and Female Pelvic Bone
The pelvis is one of the most significant skeletal features for distinguishing between males and females.
Female hip bones of the pelvis are wider and larger than male pelves and have a rounder pelvic opening. Male false pelves appear taller and narrower than female false pelves because male iliac crests are higher.
The male sacrum differs from the female sacrum in that it is longer, thinner, straighter, and has a more noticeable sacral promontory. Females have an obtuse (90-100 degrees) angle between the inferior pubic rami, whereas males have an acute (70 degrees) angle. As a result, the angle is known as the pubic arch in women and the subpubic angle in men.
The female pelvis has evolved to its greatest capacity for birthing. In contrast, males humans are more suited for bipedal walking because they are not required to give birth.
Pubic Bone and Its Parts
The pubis, or pubic bone, is one of the three major bones that comprise the pelvis. It is also known as the pelvic girdle.
The pelvic bone that faces forward the most is the pubis. The pelvic girdle is a deep, cup-shaped structure composed of the ilium, ischium, and pubis.
The primary objective of the pubis is protecting the internal sex organs and the urinary organs. People born female have a distinct pubis shape and function than people born as males.
The pubis is situated in the front, beneath the abdomen. It is divided into two halves. There are three parts to each half:
Pubic body: It is the largest part of the pubis. This body produces the flat, central, strong, and wide portion of the pubic bone.
Superior pubic ramus: It is one of the two bone segments that branch from the pubic body. The upper segment of the pubic ramus connects to the ilium (wing-shaped) and the upper part of the ischium (L-shaped).
Inferior pubic ramus: The lower portion of the pubic bone that arises from the pubic body. The lower part of the ischium is connected to this inferior pubic ramus.
The cartilage, known as the pubic symphysis, connects the left and right halves of the pubis. The pubic symphysis can migrate by about 2 millimetres in most individuals due to its relative flexibility.
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