Your lower back contains 5 bones.
Your lower back contains 5 vertebral bones stacked above each other with intervertebral discs in between.
These bones are connected at the back with specialized joints.
The lumbar spine connects to the thoracic spine above and the hips below.
Individual anatomical structures include2:
Vertebrae.
Your lumbar vertebrae are labeled L1 to L5, which progressively increase in size, allowing them to bear the body’s weight more effectively.
Your vertebrae protect important nervous tissues, such as your spinal cord and the cauda equina.
Discs.
A total of 5 intervertebral discs are situated between your vertebral bodies. The discs typically provide cushioning and shock-absorbing functions to protect your vertebrae during spinal movements.
Facet joints. Your vertebrae are connected in the back of the spine with paired facet joints.
These joints provide stability and allow your spine to move in different directions.
The joint surfaces are lined by cartilage for smooth movements.
The facets of the upper lumbar vertebrae are similar to the thoracic facet joints and allow more back and forth spinal movements.
The facets of the lower lumbar spine are more flexible and facilitate side-to-side movements.
The muscles in the small of your back are called the spinalis muscles which are closest to your spine.
They're the smallest of the paraspinal muscles, and they help you bend backward and side to side.
They also allow you to rotate at the waist.
Other muscles in your back include.
Latissimus dorsi (lats), which helps you extend and rotate your shoulder and arm.
Levator scapulae, which raises your scapula (shoulder blade).
Rhomboids, two muscles (the rhomboid major and minor) that work together to pull the scapula inward toward the spine.
The small of the back is called the small of the back because it's smaller and narrower than the rest of it.
The small of the back is the lower part of the back that is smaller and narrower than the rest.
The small of the back is also the lumbar region of the back.
The human back, also called the dorsum, is the large posterior area of the human body, rising from the top of the buttocks to the back of the neck.
It is the surface of the body opposite from the chest and the abdomen.
The vertebral column runs the length of the back and creates a central area of recession.
The breadth of the back is created by the shoulders at the top and the pelvis at the bottom.
The central feature of the human back is the vertebral column, specifically the length from the top of the thoracic vertebrae to the bottom of the lumbar vertebrae, which houses the spinal cord in its spinal canal, and which generally has some curvature that gives shape to the back.
The ribcage extends from the spine at the top of the back (with the top of the ribcage corresponding to the T1 vertebra), more than halfway down the length of the back, leaving an area with less protection between the bottom of the ribcage and the hips.
The width of the back at the top is defined by the scapula, the broad, flat bones of the shoulders.
The fifth lumbar spine vertebrae (L5) is part of the greater lumbar region.
To the human eye, this is the curve just above the buttocks, which is also commonly referred to as the small of the back.