The spinal cord is a long, delicate structure of a tube that starts at the end of the stem of the brain and goes down almost to the bottom of the spine. Nerves that carry incoming and outgoing signals between the brain and the rest of the body consist of the spinal cord. For reflexes, such as the knee jerk reflex, it is also the centre. Three layers of tissue protect the spinal cord, like the brain (meninges). In the spinal canal, which runs along the middle of the spine, the spinal cord and meninges are located. The spine is composed of 33 individual backbones in most adults (vertebrae). Much like the skull covers the brain, the spinal cord is covered by vertebrae.Disks made of cartilage, which serve as cushions, separate the vertebrae, minimizing the forces produced by movements such as walking and jumping. The cartilage vertebrae and discs stretch the length of the spine and form the vertebral column together, often referred to as the spinal column.The spinal cord, like the brain, consists of gray and white matter. The cord's butterfly-shaped core is made of gray matter. There are motor nerve cells (neurons) in the front wings (also called horns) that relay information from the brain or spinal cord to muscles, stimulating movement. Sensory nerve cells include the back horns, which relay sensory information to the brain from other parts of the body via the spinal cord. The surrounding white matter comprises columns of nerve fibres from the rest of the body (ascending tracts) that carry sensory input to the brain and columns that carry motor impulses from the brain to the muscles (descending tracts).
Organization of the Spine
The spine is made up of a column of bones called vertebrae (spinal column). The spinal cord, a long, fragile structure contained in the spinal canal which runs through the centre of the spine, is protected by the vertebrae. Disks made up of cartilage are between the vertebrae, which help cushion the spine and give it some flexibility.Three layers of tissue protect the spinal cord, like the brain (meninges).
1. Spinal Nerves:
There are 31 spinal nerve pairs arising from the spinal cord between the vertebrae. Two short branches (roots) emerge from each nerve: One at the front of the spinal cord (motor or anterior root) The one at the back of the spinal cord (sensory or posterior root)The motor roots carry commands, particularly skeletal muscles, from the brain and spinal cord to other parts of the body. The sensorial roots bring information from other parts of the body to the brain.
2. Cauda Equina:
About three-fourths of the way down the spine, the spinal cord stops, but a bundle of nerves stretches beyond the cord. This bundle, since it resembles the tail of a horse, is called the cauda equina. Nerve impulses are carried by the cauda equina to and from the legs.
3. Spinal Cord Tracts
The white matter in the spinal cord consists of ascending and descending tracts.
The ascending tracts are responsible for transmitting the sensory information from the sensory receptors to the Central Nervous System. It emerges from the dorsal ganglion. The dorsal and the ventral spinocerebellar tracts are responsible for carrying the unconscious proprioception information from joints and muscles to the lower part of the cerebellum. There are four essential parts in the ventral column, which are as follows –
The paleospinothalamic tract: This is the anterior spinothalamic tract that carries the touch, pain, temperature, and information to the brain stem nuclei and to the diencephalon
The spine olivary tract: This is responsible for carrying the information from the Golgi tendon organs to the cerebellum.
The spinoreticular tract and the spinotectal part are both responsible for carrying pain information to the brainstem and diencephalon. They are present in the grey matter and are intersegmental nerve fibres.
The Descending tracts originate from brain stem nuclei and several cortical areas. They are responsible to carry several motor activities information such as posture, tone of the muscle, balance of the body, visceral and somatic activities. The corticospinal tract and the Rubrospinal tract that are present in the lateral column are responsible for carrying information related to voluntary movements.
The reticulospinal tract acts as a motor neuron that has a primary function of lowering down the activity in the spinal cord and without this pathway, it is observed to have increased extensor tone.
The vestibulospinal tract originates from the medulla and receives very limited inputs from the cortical areas. It plays a role in the control of balance and posture.
The rubrospinal tract originates from the red nucleus in the brain. It works towards the common structure and distal motor control.
Lissauer's tract is responsible for regulating pain sensation at the spinal level.
4. Dorsal Root:
The information by the joints, skin, and skeletal muscles are transmitted to the spinal cord by the sensory cells present in the dorsal root ganglia. The medial division of the dorsal root consists of myelinated axons that are responsible for conducting sensory fibres from the skin and the later division consists of the unmyelinated axons carrying pain and temperature.
5. Spinal Arteries:
The arteries that run vertically down the spinal cord and rise from the vertebral artery are known as the spinal arteries. There are several branches of other arteries along with several numbers of anastomoses of the spinal arteries that make up a vasocorona around the spinal cord. The dorsal column sensory is maintained even when the anterior spinal artery results in loss of power and spinothalamic sensory deficit.
6. Autonomic Pathways
They consist of the autonomic nerves that are carried by the spinal cord. Sympathetic nerves have an exit outlet through the thoracolumbar spinal cord whereas the parasympathetic nerves exit the vertebral canal through the sacral spinal control. However, some of these nerve fibres are carried within cranial nerves and remain unaffected even through a spinal cord injury.
Backbone is another name that the vertebral column is used to identify. A flexible column that runs from the neck to the tail of the vertebrate body is the vertebral column. The primary characteristic used to distinguish vertebrates from other chordates is usually the presence of a vertebral column.A notochord is usually formed by chordates; this notochord can be identified only during embryonic development in vertebrates. Later, it grows into the vertebral column. In addition, the vertebral column consists of a series of vertebrae grouped as cervical, thoracic, lumbar, sacral, and coccygeal vertebrae and is a bony structure. Humans have a backbone of 33 vertebrae. In addition, housing the spinal canal is the main feature of the vertebral column or backbone; the spinal cord extends from head to tail within this canal. It also provides the spinal cord with protection and provides sites for the nerves to emerge from the spinal cord. The spinal cord is basically one of the two components of the central nervous system, while the brain is the second component. Here, the backbone provides muscles such as pectoral and pelvic girdles and many muscles for attachment sites. In addition, when standing and walking, the backbone transmits body weight into the pelvis.
What is the Difference Between Spinal Cord and Backbone?
The key distinction between the backbone and the spine is that the more informal term for the vertebral column is the backbone, whereas the more formal term is the spine.
Functions of Backbone
The following are the functions of the backbone –
The backbone acts as a protection of the spinal cord and its nerve roots against any damage.
It is responsible for the attachment of various muscles, tendons, and ligaments in the back of the body.
It helps in flexible movements of the body, such as bending forward, left, and right.
The vertebrae are essential for storing nutrients and lipids as it also produces white and red blood cells.
Kinds and Numbers of Vertebrae in the Body
The different kinds of vertebrae in the vertebral column and are as follows –
Atlas is the first cervical vertebrae and there are seven cervical vertebrae in the neck region.
Next comes the thoracic vertebrae that are twelve in number connecting to the upper back and ribs on either of the sides.
The vertebrae on the lower back are known as the lumbar vertebrae and they are five in number. They are responsible for maintaining the body’s weight and they are the largest and cause common back problems.
The vertebrae are present in the small back and make of the sacrum. They form a triangle after the age of 26.
The lowermost region of the vertebral column that merges with the hip bones. It consists of 3-5 vertebrates, also known as the tailbone.
The more casual word to define the vertebral column, which is the vertebrate body's most distinctive characteristic, is the backbone. It consists of a series of vertebrae which are divided by intervertebral discs. The spine is the more formal term used to define the vertebral column, on the other hand. The only difference between the backbone and the spine is, therefore, the use of the term.