Pelvis
The lower part of the trunk between lower abdomen and thighs is generally termed as Pelvic region or Pelvis. It is a basin shaped, bony, massive, ring structure that encloses the terminal part of digestive tract and Reproductive organs. It is basically a skeletal structure formed by the union of various bones including two hip bones, terminal vertebral column (Sacrum and Coccyx). Pelvis contains a cavity known as Pelvic cavity below which there is the Pelvic floor. Beneath the Pelvic floor lies the Perineum, which contains genitalia.
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STRUCTURE
Pelvis is basically a region located lower to the trunk and consists of two parts:
- Pelvic Girdle : It is the bony skeleton, which comprises of two opposite hip bones located side by side. These hip bones articulate posteriorly to the Sacrum and Coccyx which are terminal parts of vertebral column. Anteriorly, two hip bones join to form the Pubic Symphysis. Each hip bone further consists of three bones: Ilium, Ischium and Pubis. During childhood these three bones are separate bones that become fused to form a single bone in adulthood. There is a socket formed by the union of the three bones that articulates with femur (the thigh bone) to form the hip joint.
- Pelvic Cavity : The space enclosed by the Pelvic Girdle is termed as Pelvic Cavity. This space is further divided into two regions by an imaginary line called Pelvic Brim. The area above the Pelvic brim is known as Greater or False Pelvis while the area below the Pelvic brim is known as Lesser or True Pelvis. The false Pelvis is the space enclosed between the two Ilia on either side presented with an interval in front. The Greater Pelvis contains intestines and provides them support and to the abdominal wall. The True or Lesser Pelvis is surrounded by the Pubic bones in front and with the Sacrum behind and two Ischia laterally. It is more complete than Greater Pelvis and contains Terminal Colon, Rectum, Bladder and some Reproductive organs. Below it lies the Pelvic Floor.
- Pelvic Floor : It is also termed as Pelvic Diaphragm. It comprises of several muscles and its function is to provide support to the Pelvic Cavity above and to protect the Perineum lying below.
- Perineum : It is the most delicate part of the Pelvic region, which is susceptible to damage during trauma. It encloses the Genitalia and Reproductive organs of male and females.
BLOOD SUPPLY
Internal Iliac Artery supplies to the most of the Pelvis. It arises from common Iliac artery. This bifurcation lies in front of the Sacro-Iliac joint. It is then divided into two branches anterior and posterior branches. These further divide into Visceral branches supplying the organs residing in the Pelvis, and the Parietal branches supplying the bony Pelvis.
NERVE SUPPLY
The bony Pelvis receives innervation from the spinal nerves supplying the Sacrum and Coccyx. The Pelvic part of Autonomic Nervous System supplies the rest of the Pelvis.
LYMPHATIC DRAINAGE
The majority of the lymphatics drain into the group of lymph nodes residing along Iliac arteries and their branches. External Iliac lymph nodes receive the lymph from inguinal region and external genitalia. The lymph of the viscera of Pelvis drains into Internal Iliac lymph nodes. Both external and internal Iliac lymph nodes are drained into Common Iliac lymph nodes which ultimately are drained by Aortic lymph nodes lying along the Abdominal Aorta.
FUNCTION
The Pelvis is a strong and a rigid structure tht performs various functions. It is highly developed in human beings and enables them to stand on two legs and lets them walk, run and bend.
- It provides attachment of the vertebral column to both of legs forming the hip joint.
- It is a weight bearing structure of the body and transmits the weight while standing and walking from the upper part of body to the legs.
- It provides attachment to the muscles required to maintain the posture and used for locomotion.
- It provides protection to the viscera of the Pelvis.
- It provides support to the abdominal wall and muscles and viscera of the abdomen.
- It provides attachment to the External Reproductive organs and to the membranes and muscles associated to them.
- It is an important part of the skeleton during pregnancy and delivery. Its cartilaginous Pubic Symphysis expands during delivery, thus it helps the new born baby to come out of the Pelvis.
CLINICAL SIGNIFICANCE
- There is a great difference between the female and male Pelvis, which allows the female Pelvis to bear the growing baby in the uterus and to expand at the pubic symphysis at the time of the delivery.
- Any abnormality in the formation of the Pelvis leads to the inability of a person to stand and walk.
- During road traffic accidents and fall from a height, hip joint can be fractured badly and the fragments of bone can damage the terminal Digestive Tract and Reproductive organs of the Pelvis.
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