The pelvic girdle is a part of the appendicular skeleton, which connects the lower limbs to the axial skeleton. The upper limb is connected by the pectoral girdle to the axial skeleton.
The appendicular skeleton is made up of 126 bones and includes the pectoral girdle and limbs apart from the pelvic girdle.
The pelvic girdle forms the bony framework of the pelvis together with the sacrum of the vertebral column and coccyx. It provides support and stability to the body and transfers the weight of the upper body from the axial skeleton to the hips and lower limbs. It also protects the abdominal and pelvic visceral organs.
Pelvic Girdle Bones
Pelvic girdle is made up of a pair of single bones called coxal bone (hip bone), which are strongly joined to the sacrum of the vertebral column. Unlike the pectoral girdle, which provides more range of movement, hip bones allow relatively limited movement and form the strong foundation for the upper body and support the body weight.
Coxal bones together with the coccyx and the sacrum constitute the pelvis.
Coxal Bone (Hip bone)
Each half of the pelvic girdle is composed of a single bone known as the coxal bone or hip bone.
- Coxal bone is made up of a fusion of three bones, namely ilium, ischium and pubis.
- Ilium- Ilium is the largest part of the coxal bone. It is the upper part and has a fan-like structure. It is attached to the sacrum of the vertebral column strongly by the sacroiliac joint.
- Ischium- It makes the posterior part of the pelvic girdle below the ilium. It provides support while sitting.
- Pubis- It makes the lower anterior part of the pelvic girdle.
- Pubic symphysis- It is a joint between the pubis part of the two hip bones in the middle portion. It contains fibrous cartilage.
- Acetabulum- It is a cavity formed by the fusion of ilium, ischium and pubis. The femur or thigh bone articulates with the acetabulum.
- The coccyx is attached to the lower part of the sacrum by sacrococcygeal symphysis.
- Obturator foramen- It is the large opening between the ischium and the pubis bone. It is round or oval in shape. It is filled with the lining of connective tissue and is the attachment site for muscles.
The pelvic girdle divides the pelvic region into two portions, the upper is known as the false pelvis or greater pelvis and the lower part is known as the lesser pelvis or true pelvis.
- Greater pelvis- It is also known as the false pelvis. It is the upper part and encloses the small and large intestine.
- Lesser pelvis- It is the lower part of the pelvis. It contains pelvic organs such as the urinary bladder, internal sex organs, etc. and known as the true pelvis.
- The Pelvic inlet separates the two regions, the outer surface of the pelvic inlet is known as the pelvic brim.
- The lower limit of the lesser pelvis is marked by the pelvic outlet. In females, it is wider.
The female pelvis differs from the male and is adapted for the foetal development and childbirth. The female pelvis is wider and broader than the male pelvis. The bones are lighter compared to males. The pubic arch is greater than 90°, whereas in males it is narrower and less than 90°.
Also see: Locomotion and Movement
To sum up, the pelvic girdle is made up of a pair of hip bones, which are joined to the axial skeleton through the sacrum. It connects the lower limbs to the trunk. The pelvic girdle, sacrum and the coccyx constitute the pelvis. The pelvis of male and female differs.
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