Pelvic Girdle Bones – Class 11 | Chapter – 20 | Biology Short Notes Series PDF

Pelvic Girdle Bones: Pelvis is the lower section of the trunk. The region between the thighs and abdomen is called the pelvic region. It is also called pelvic girdle or bony pelvis. This basin-shaped structure of bones associates the legs and the trunk. 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.

GENIUS 2023

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.

The anatomy of the Pelvic girdle shows the bony pelvis. It contains the skeletal framework of the pelvic region enclosing the pelvic structures. Generally, it is classified into two different regions – the pelvic spine and the pelvic girdle. The pelvic spine is the posterior section of the pelvis after the lumbar spine. It comprises the coccyx and the sacrum. The hip bone or the pelvic girdle comprise three bones – ilium, ischium and the pubic bone.

Parts of Pelvic Girdle Bones

Pelvic Girdle Bones

The pelvis is made up of a number of smaller bones. They are: 

Tail bone: This is also known as the coccyx. The tail bone is the small three-sided shape which typically resembles a tail. The coccyx is the last fragment of the vertebral segment and it additionally provides support for weight and helps in the movement.

Sacrum: This is a shield-shaped bone situated at the base of the vertebrae. The sacrum is also known as sacral vertebra. It imparts stability as well as strength to the pelvis and also forms the posterior wall.

Hip bones: The hip bones are composed of three parts such as pubis, ilium, and ischium. All of these bones are separated by a triradiate cartilage before puberty arrives. They start fusing with each other at the age of 15-16. 

Pubis: In the human body, the pubis is located at the front (ventral and anterior). The left and right pubic bones consolidate together, shaping the pubic symphysis. Usually, the pubic bone comprises three parts – inferior ramus of the pubis, the body of the pubis, and superior ramus of the pubis.

Ilium: The ilium is the biggest part of the hip bones. This is likewise the uppermost part of the hip bone. It is fairly easy to recognize, with its distinctively broad and flaring bones.

Ischium: The Ischium, similar to the pubis, is formed of 3 parts: the body, inferior ramus of the Ischium and superior ramus of the ischium.

Types of Pelvic Girdle Bones

The shape of the pelvis mainly varies in the female body. It decides whether a person can give birth vaginally or not. Below are given the four general types of pelvis:

Android: The android pelvis has a heart-shaped brim with a narrow shape in the front. This type of pelvic bones are mainly found in tall women with narrow hips and also in African women. 

Anthropoid: This is an oval-shaped anthropoid pelvis brim with a slightly narrow pelvic cavity. In this pelvis, the outlet is large but most of the diameters are reduced.

Gynecoid: This is one of the most common pelvis shapes found in the female body and it favours vaginal birth. Different shapes like android and platypelloid face more trouble in vaginal birth. Gynecoid is also known as the genuine female pelvis.

Platypelloid: It has a kidney-shaped brim and it very well might be tightened in diameter across from front to back. In this, there’s just an issue for the baby while entering the pelvis.

Hip Bone Anatomy and Functions

The hip bone (coxal bone) is an irregularly shaped part of the bony pelvis. Each half of the pelvic girdle is composed of a single hip bone or coxal 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.

Functions of the Hip joint

The hip is the largest weight-bearing joint in the body; it is a ball-and-socket joint. The joint connects the lower extremities with that of the axial skeleton. The main function of the hip joint is to support the weight of the body dynamically as it promotes load and force transmission to the lower parts from the axial skeleton. Thus it allows mobility. Hip joint enables movement in three main axes; these are all perpendicular to each other.

Further, the hip joint brings about weight-bearing. As a result of the depth of the acetabulum and its shape, the complete head of the femur can be confined by it.

True Pelvis and False Pelvis

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°.

The true pelvis has rectum, some bowel, the reproductive structures and the urinary bladder. The false pelvis is superiorly and anteriorly in association with the abdominal cavity. It has sections of colon, most parts of small bowel and the iliac vessels.

Female Pelvis

Pelvis is the lower section of the torso found between the legs and the abdomen. The region supports the intestines and comprises the bladder and the reproductive structures. The female pelvis, in addition, comprises the cervix, vagina, uterus, ovaries and fallopian tubes. It must accommodate and provide enough space for the development of the foetus and provide a passageway during parturition. Thus, the female pelvis is typically wider and broader compared to the male pelvis.

 


JOIN OUR TELEGRAM CHANNELS
Biology Quiz & Notes Physics Quiz & Notes Chemistry Quiz & Notes

Follow on Facebook

By Team Learning Mantras