Overview:The Spinal Column
From Head-neck-joints instability conditions
Table of contents Available documents from the overview:
- Anatomy of the vertebral column
- Anatomy of the cervical spine
- Symptoms linked to head-neck-joint instability
Contents |
The Spinal Column
The Spinal Column (Columna vertebralis) forms the longitudinal axis of the skeleton. The Spinal Column of an adult human consists of 24 vertebrae aligned straight one below the other from the skull-base to the coccyx. Between the vertebrae lie the intervertebral discs which give the spinal column its strength and flexibility. Furthermore, the vertebrae form different attachment points for short or long muscles.
The spinal column is divided in:
- 7 cervical vertebrae. These form the Cervical spine. The single vertebrae are consecutively numbered C1- C7 (The C is derived from Cervical spine).
- 12 thoracic vertebrae. These form the Thoracic spine. The vertebrae of the thoracic spine are again named Th1 to Th12 (Th = Thoracic vertebra). The thoracic spine is very flexible and has a concave curvature to the ventral side.
- 5 lumbar vertebrae. These form the Lumbar spine. These vertebrae are identified as L1 to L5 (L = Lumbar vertebra). The lumbar vertebrae are the largest segments of the movable part of the spinal column.
- With an adult the 5 vertebrae of the sacrum and the 4 coccygeal vertebrae are united and form the sacral bone and the coccyx.
The Spinal Cord
In its vertebral canal (Canalis vertebralis), the spinal column contains the spinal cord (Medulla spinalis). It forms a kind of “highway” between the brain and the nerves of the spinal cord, the so-called spinal nerves. It is called a “highway” because nervous signals are partly conducted with a very high velocity from the brain to the periphery and vice versa. This is done by large ascending and descending lines of transmission, the so-called white substance of the spinal cord. But the spinal cord can e.g. also trigger necessary motor reactions especially fast. The spinal cord of an adult human has a length of about 45 cm and emerges level with the foramen occipitale magnum from the afterbrain (Medulla oblongata). This cord is several centimetres thick and reaches to the second lumbar vertebra in the vertebral canal. Throughout the entire length, 31 pairs of nerve roots originate on both sides and unite to the respective spinal nerves. With these exits of nerve roots the spinal cord is divided in 31 spinal cord segments which contain their own centres of reflexes and linkage.
The following segments are to be distinguished :
- 8 cervical segments supplying especially the muscles of respiration and the upper extremities.
- 12 thoracic segments whose nerve roots supply the largest part of the torso with impulse cords.
- 5 lumbar segments
- 5 segments of the sacral bone supplying the lower extremities, the exterior genital and the anus together with the lumbar segments.
- one to three coccygeal segments supplying the dermal area above the coccyx.
The segments are situated inside the vertebrae respectively and have different areas of supply of function. For example, the segment of the spinal cord level to the first thoracic vertebra (Th1) executes the impulse transmission to the forearms, the wrists, the hands, the fingers, the oesophagus and the trachea. A dislocation of this thoracic vertebra can lead to limitations in the areas of supply mentioned above. Since the respective segments lie inside the vertebrae, they are named after the corresponding vertebral body in literature.
There is an entire list about the areas of function and supply of the spinal cord segments which I display below for the sake of completeness.
This list does not derive from me but was compiled by chiropractors. It can be found in appropriate literature, but also in the book “Atlas des ganzheitlichen Heilens” by E.A. Röcker:
Spinal column segment:
Cervical Spine
C1 (=name of vertebral body) Functionality: Blood supply for head, pituitary gland, scalp and facial bones. Inner and middle ear. Sypmathetic nerve system.
C2 Eyes, visual nerves, acoustic nerve, ethmoidal sinus, mastoid bone, tongue, forehead.
C3 Cheeks, auricles, facial bones, teeth, facialis nerve
C4 Nose, lips, mouth, eustachian tube
C5 Vocal cords, neck glands, throat
C6 Neck muscles, shoulders, tonsils
C7 Thyroid gland, bursa of the shoulder, elbow
Thoracic spine
Th1 Forearms, wrists, hands, fingers, oesophagus, trachea
Th2 Heart with its valves, endocard and pericard, coronary vessel
Th3 Lungs, bronchia, pleura, thorax, breasts
Th4 Gall bladder and gall canals
Th5 Liver, solar plexus, blood
Th6 Stomach
Th7 Pancreas, duodenum
Th8 Spleen
Th9 Adrenal glands
Th10 Kidneys
Th11 Kidneys, ureter
Th12 Interstinum, lymphatic system
Lumbar spine
L1 Colon, groin gate
L2 Appendix, abdomen, femoral
L3 Genitals, uterus, bladder, knee
L4 Prostata, muscles of the lower back section, sciatica
L5 Lower leg, ankle, feet
As can be seen in the above image, the spinal cord is relatively well cushioned, embedded between vertebral body and vertebral arch. The layer of fat tissue of the epidural space and in particular the subarachnoidal space filled with cerebro-spinal fluid form, so to speak, the deformable zone of the spinal cord.
The spinal nerves already mentioned are part of the peripheral nerve system and leave the vertebral canal of the spinal column through the intervertebral holes, i.e. through the port between two neighbouring vertebrae.
The intervertebral discs
Between neighbouring vertebrae from the second cervical vertebra to the sacral bone rather strong discs of filament cartilage with a thickness of approx. five millimetres are situated, the so-called intervertebral discs. They operate as solid links and elastic buffer of the spinal column. They consist of an exterior filament ring aligned in concentric layers, the Anulus fibrosus, and a central, elastic, jellyfish core, the Nucleus pulposus. The filaments of the Anulus fibrosus cross each other in consecutive layers in order to increase resistance against torsion. The intervertebral discs make up about 25% of the total length of the spinal column. Vertically seen they have the form of a wedge, causing the convex curvature of the lumbar spine (Lordosis). Intervertebral discs are only sparsely supplied with vessels and nerves.
They form elastic links of the vertebral bodies and increase the motility of the spinal column by deforming correspondingly. Thereby the Nucleus pulposus relocates rather minimally within die intervertebral disc according to the flexion of the spinal column. For this reason the spinal column operates like an anti-shock pad and absorbs compressions.
The intervertebral discs change with growing age:
- The humidity ratio of the Nucleus pulposus decreases and the jellyish basic substance is gradually replaced by filament cartilage, making it resemble the Anulus fibrosus more and more. That way the thickness of the intervertebral disc declines maginally. The length of the spinal column can reduce by 2-3 centimeters. Because of that humans become “smaller” when getting older
- The Anulus fibrosus becomes rifty, allowing parts of the Nucleus pulposus to emerge through it and to vault against the vertebral canal
With injuries or sicknesses the filaments of the Anulus fibrosus soften. Therewith the Nucleus pulposus set on swelling pressure and surrounded by them can perforate the rear ligament and compress nerves and vessels. This is called herniated vertebral disc.