Lumbar Spine Anatomy

the human spine is made up of 24 spinal

bones called vertebra the vertebra

stacked on top of one another to create

the spinal column the spinal column

gives the body its main upright support

from the side the spine forms three

curves the neck called the cervical

spine curves slightly inward the

mid-back or thoracic spine curves

outward the outward curve of the

thoracic spine is called kyphosis the

low back also called the lumbar spine

curves slightly inward an inward curve

of the spine is called lordosis the

lumbar spine is made up of the lower

five vertebra doctors often refer to

these vertebra as l1 to l5 the lowest

vertebra of the lumbar spine

l5 connects to the top of the sacrum the

triangular bone at the base of the spine

that fits between the two pelvic bones

there is a joint on each side of the

sacrum that connects the sacrum to the


this joint is called the sacroiliac or

SI joint each vertebra is formed by

round block of bone called a vertebral

body the lumbar vertebral bodies are

taller and bulkier compared to the rest

of the spine this is partly because the

lumbar spine has to withstand pressure

from the body weight and from daily

actions like lifting carrying and

twisting a bony ring attaches to the

back of each vertebral body when the

vertebra are stacked on top of one

another these rings form a hollow tube

called the spinal canal this bony tube

surrounds the spinal cord as it passes

through the spine just as the skull

protects the brain the bones of the

spinal column protect the spinal cord

the spinal cord extends from the brain

to the l2 vertebra below this level the

spinal cord splits into a bundle of

nerves that goes to the lower limbs and

pelvic organs the latin term for this

bundle of nerves is cauda equina meaning

horse's tail as the spinal cord travels

from the brain down through the spine it

sends out nerves on the side of each

vertebra called nerve

it's these nerve roots joined together

to form the nerves that travel

throughout the body and form the body's

electrical system the nerve roots that

come out of the lumbar spine form the

nerves that go to the lower limbs and

pelvis the thoracic spine nerves go to

the abdomen and chest the nerves coming

out of the cervical spine go to the neck

shoulders arms and hands it is sometimes

easier to understand what happens in the

spine by looking at a single spinal

segment the spinal segment includes two

vertebra the intervertebral discs

between the two nerve roots that leave

the spinal cord at that level and the

small facet joints that link each level

of the spinal column an intervertebral

disc is made up of two parts the center

called a nucleus pulposus is spongy and

acts like a shock absorber to cushion

the force between each vertebra the

nucleus is surrounded by a series of

strong ligaments rings called the

annulus fibrosus ligaments are made of

strong connective tissue and connect one

bone to another the annulus fibrosus is

actually a special ligament that

connects two vertebra together between

the vertebra of each spinal segment are

two facet joints the facet joints are

located on the back of the spinal column

there are two facet joints between each

pair of vertebra one on each side of the

spine a facet joint is a small bony knob

that sticks out from the vertebral body

at the back of the lumbar spine where

these knobs meet they form a synovial

joint that connects the two vertebra the

facet joints of the lumbar spine moved

together in a sliding motion as you bend

forward and backward the surfaces of the

facet joints are covered by articular

cartilage articular cartilage is a

smooth rubbery material that covers the

ends of most joints it allows the bone

ends to move against each other smoothly

without friction to spinal nerve roots

exit the sides of each spinal segment

one on the left and one on the right as

the nerves leave the spinal cord they

pass through a small bony tunnel on each

side of the vertebra called a neural

for Raymond the lumbar spine is

supported by a complex set of ligaments

and muscles ligaments are arranged in

layers and run in multiple directions

where they connect the bones of the

lumbar spine to the sacrum and pelvis

the muscles of the low back are also

arranged in layers those closest to the

surface are covered by a thick tissue

called fascia the middle layer runs up

and down over the lower ribs chest and

low back they blend in the lumbar spine

to form a thick tendon that binds the

bones of the low back pelvis and sacrum

the deepest layer of muscles runs along

the back surface of the spine

these muscles connect the lumbar

vertebra pelvis and sacrum and

coordinate movement with the muscles of

the abdomen to help hold the spine

steady during activity we hope watching

this video will help you better

understand your orthopedic care you can

find more information about this and

other orthopedic conditions or

procedures at the orthopod comm