The Vertebral Column:
The adult vertebral (spinal) column consists of 26 bones that are grouped as follows:
7 cervical vertebrae in the neck
12 thoracic vertebrae that articulate with the 12 pairs of ribs
5 lumbar vertebrae of the lower back
1 sacrum which is actually a fusion of 5 sacral vertebrae (fusion occurs from late teens to early 20's)
1 coccyx or "tailbone" which is a fusion of 4 coccygeal vertebrae
Intervertebral discs are located between adjacent vertebrae. These fibrocartilage discs form strong joints and absorb spinal compression shock.
Various spinal disorders include:
Herniated (slipped) disc - protrusion or rupture of an intervertebral disc
Scoliosis - exaggerated lateral bending of spinal column
Kyphosis - "hunchback" exaggerated thoracic curvature
Lordosis - "swayback" exaggerated lumbar curvature
Spina bifida - congenital defect with incomplete closure of the vertebral column
Epidural anesthesia, often used in obstetrics, is injected into the sacrum at the sacral hiatus.
In a lumbar puncture ("spinal tap), spinal fluid is removed using a long needle inserted between L3-L4 or L4-L5.