The term “pedicle” refers to a stalk-like structure that serves as a support or point of connection, acting as a base that connects one biological part to another. This general definition applies whether discussing the intricate skeletal framework of a human or the delicate structure of a flower.
The Pedicle in Human Anatomy
In the human body, pedicles are specific components of the vertebral column, which houses the spinal cord. Each vertebra, from the neck down to the lower back, has a pair of these short, thick pillars of bone. They project backward from the upper part of the vertebral body, which is the main, weight-bearing portion of the bone. These pedicles then connect to a flattened plate of bone called the lamina, and together they form a protective ring.
The primary role of the vertebral pedicles is to help form the spinal canal. The large opening enclosed by the vertebral body, pedicles, and lamina is known as the vertebral foramen. When the vertebrae are stacked, these individual foramina align to create a continuous channel, the spinal canal, which provides a secure pathway for the spinal cord.
The pedicles are robust, cylindrical structures composed of a strong outer layer of cortical bone and a more porous, cancellous bone core. Notches in the superior and inferior surfaces of each pedicle create small openings between adjacent vertebrae called the intervertebral foramina. These openings allow spinal nerves to exit the spinal canal and travel to other parts of the body.
Medical and Surgical Significance
The anatomical structure of vertebral pedicles gives them a significant role in spinal surgery. Their strength makes them an ideal anchoring point for surgical implants. In procedures like spinal fusion, which aims to stabilize the spine and alleviate pain from conditions such as fractures or scoliosis, surgeons rely on these structures.
The most common application involves the use of pedicle screws. These specialized medical screws are carefully inserted through the pedicles and into the vertebral body. Once in place, the heads of the screws are connected by rods, creating a rigid framework that immobilizes a section of the spine. This stabilization prevents motion between the affected vertebrae, facilitating the growth of new bone and fusion of the spinal segment.
The success of this technique depends on the accurate placement of the screws, as improper insertion can risk injury to the nearby spinal cord or exiting nerve roots. Surgeons use anatomical landmarks and imaging technology to guide the screws along the precise trajectory of the pedicle’s axis.
Pedicles in the Broader Biological World
Beyond human anatomy, the term “pedicle” is used in other biological fields to describe similar stalk-like structures. In botany, a pedicle is the small stalk that supports an individual flower within a larger inflorescence or cluster. It connects the base of the flower to the main stem of the inflorescence, positioning it for pollination and sunlight exposure.
In the realm of zoology, one example comes from the deer family. Male deer, elk, and moose grow antlers from bony stumps on their skulls called pedicles. These permanent, skin-covered protuberances provide the base from which the antlers, which are shed and regrown annually, develop. Another zoological use of the term is found in brachiopods, a phylum of marine invertebrates. Many brachiopods attach themselves to the seafloor using a fleshy stalk known as a pedicle.