Lumbar Spine (Lower Back) Anatomy and Function

The spinal column is made up of 26 bones: 24 unique vertebrae plus the sacrum and coccyx (tail bone) at the end of the backbone. The Vertebrae seem to be chained together). The vertebrae include:
• 7 cervical vertebrae which make up the neck
• 12 thoracic vertebrae of the chest
• 5 lumbar vertebra or the “lower back”—L1, L2, L3, L4 and L5.

Here is more information about your nerves, spine and back:

The Spinal Column

Bones and disks of lumbar spine

Bones, disks and facet joints of lumbar spine

The back can move in many different directions, it can stiffen as well as be supple. When looked at from the back, the spine appears to be straight, but looked at from the side you can see 2 curves which cause the back to have an “S” shape—it curves forward at the neck (cervical spine) and lower back (lumbar spine) and slightly backwards at the thoracic spine and sacral region. These curves help support the head and provides strength, flexibility and provides super shock absorbing abilities. Many problems with the back are associated with the normal curvature of the back.

Between each vertebra is a cushion called an intervertebral disk. On the anterior side of each vertebra is an oval shaped disk called the vertebral body. On the posterior side of each vertebra is the vertebral foramen, which is an opening through which the spinal cord passes. A crucial job of the back is to protect and support the vital spinal cord and spinal nerves.

A Spinal Segment

Spinal Segment

Segment is made of two vertebrae, the intervertebral disk, and two spinal nerves

A spinal segment forms a functional unit and is made up of two adjacent vertebrae, the intervertebral disk between them, the two spinal nerves that exit from each side of the spinal cord, ligaments and muscles.

The Sacrum

Side view of the sacrum and tailbone

Side view of the sacrum and tailbone, the body of the sacrum forms a joint with the 5th lumbar vertebra.

The sacrum is the last segment of the spine. At birth, it is made of several vertebrae. By the time you’re an adult these vertebrae have fused together to form the sacrum. The Sacrum is a large, triangular bone, in the lower part of the vertebral column and at the upper and back part of the pelvic cavity, where it is inserted like a wedge between the two hip bones; its upper part or base joins with the 5th lumbar vertebra by intervertebral fibrocartilage and at the bottom it joins with the coccyx or tailbone.

The Lumbar Spine

The Lumbar spine consists of the vertebral body, posterior elements, intervertebral disks, and ligaments. The lumbar spine is made up of the five lumbar vertebrae located between the thoracic spine and the sacrum. This area is commonly called the “lower back”. The lumbar vertebrae are the largest of the vertebrae because of their weight-bearing function supporting the torso and head.

L-5, the 5th lumbar vertebra.

L-5, the 5th lumbar vertebra.

Labeled lumbar vertebra

Labeled lumbar vertebra

The function of the structures of the lumbar spine are to protect and support the spinal cord and spinal nerves. The spinal nerves pass through a large hole (foramen) in the center of each vertebrae, which when lined up is called the spinal canal. The lumbar spinal nerves branch off the spinal cord at each level between the vertebrae. The joints—a joint is where two or more bones meet—between the vertebrae contain a disk (intervertebral disk) that acts as a shock absorber.

The vertebrae of the back are “linked” together by pedicles (lamina, transverse process, and spinous process) to form facet joints.

Ligaments of the Back

The function of ligaments is to attach bones to bones and give strength and stability to the back. Ligaments are strong, tough bands that are not very flexible. The vertebral bodies of the back are connected to each other by multiple ligaments which include:
• posterior longitudinal ligaments
• anterior longitudinal ligaments
• intertransverse ligaments
• interspinous ligaments
• supraspinous ligaments

Tendons of the Back

Tendons are elastic tissues that connect muscles to bones.

Muscles of the Back

Muscles support and move the spine.

Nerves of the Back

Lumbar segment, spine, nerves

Lumbar segment, spine, nerves

Vascular structures of the Back

Arteries supply the vertebrae, ligaments, and muscles with nourishment.

Problems, Treatments and Surgery for the Lumbar Spine

• Osteoporosis
• Osteomalacia
• Arthritis
• Ankylosing Spondylitis
• Sacroiliitis
• Lumbosacral sprain and strain
• Acute Cauda Equina Syndrome
• Intervertebral Disk Disease
• Scoliosis
• Spinal Instability
Herniated Disk
Spinal Stenosis

More About the Back

Back Injury
Lumbar Spinal Fusion Surgery


  1. Mohd ekhlaque says

    I am looking degenerative changes in lumbar spine. Reduced L5-S1 intervertebral disc space. Remaining intervertebral disc spaces appear unremarkable. Plz suggest me. What can


    What happens if L1 L2 and L3 are broken or damage is lower part of body work or not

  3. Md.Shakawt hossain says

    I have got osteiphyte lumber L-4,L-5 vertebra. How can I get good treatment and recover from this.

  4. Faiz Alam says

    I am getting leg pain due to L3 and L4 nurves has pressd also loses of fiber protection of nerves pls advise.

  5. What are the reason L1_S1 vertebra disconnected

  6. sheri Clayborne says

    I had an exray and it showed mainley arthritis and mild scholis. The pain starts at the lower spine and lower back. Could a orthopedic help me?

  7. Hennie van Eden says

    If you want problems with your back go to a Doctor. Chiropractors, Physiotherapists and the more of a specialist the Doctor is are all part of a racket. I speak of 40 years of back problems from time to time. Basically every person I met who had an operation done to their back had to stop working or ended up with permanent pain. All my back problems came from wrong postures, lifting heavy items and pushing a lawnmower with my back bend in case of with a straight back and using the legs to do the pushing. After going through all the motions i.e Voltaren which is the biggest racket of all, x-rays, Chiropractors, Physiotherapists and specialists I was being lined up for back surgery. From what I was told by all these experts is that the cause of the pain was the disc pushing against the nerves due to the narrowing of the gap between the two vertebrae over a period of time, in my case as a result of the wrong position when sitting (poor ergonomic work conditions), taking an incorrect position lifting heavy equipment and most probably the main contributor pushing a heavy lawnmower incorrectly, Being of an Engineering background I came to the conclusion to fix it up should be simple, all you have to do is to stretch the gap open again so that the disc can move back in position away from the nerves. I got hold of a tennis ball and started lying on it with my back starting from as low as possible and slowly working my way up. In this specific case the pain was down my left leg and I could hardly walk. This is apparently caused by the 3rd vertebrae from the bottom, The guilty vertebrae becomes sore after a day or so and once this happens the pain start to go away in the leg. I ly on the tennis ball for about 15 minutes a day for 3 days and within a week all pain is gone. Apparently the pain is reflected in the leg and there is no pain at the vertebrae and the pain must come back to the vertebrae. I had the same experience with extensive pain in the left arm, neck etc. After going through all the motions and just short of being cut up, I thought if it works at the bottom it should also work at the top. A week later all the pain was gone. I have given this advice to a number op people and all that could handle the pain of lying on the tennis ball ended up without pain.

  8. I would like to apologise for all the typos but I suffer fron muscular atrophy,radiculopathy and severe pain and shaking. It often makes typing on a small touch screen near impossible and extremely time consuming so I use word prediction to help speed,avoid mistrikes but instead a often get mis spelling due to my improper use of word prediction or rather in actuality I move way to fast mentally and did not notice the improper prediction. Sorry,I’ll try to slow down. Try to cope? I have too?

  9. Tim Marks says

    “Speak your mind?” I have multiple sever spine injuries almost exclusively from blunt force traumas from accidents through my entire life from age 5 – through the current age of 53. These injuries involve and include broken vertebrae, sacrum,13 herniated discs in all,7 severe and some even grossly and unbelievably so. Broken and distroyed IS and facet joints of the spine, all combined injuries uniformly span the entire length of the spine and all its segments or say sections,cervical through the sacrum ! So yes,I’ll gladly speak my mind for you an if I have your attention I hope to keep it and that you give me and what i say ear? The first thing i will mention to you is ive never seen a pain killer yet in my life other than over the counter meds and home remedies and “self conducted physical therapy!” Do i have your attention? I hope? These injuries were no secret to me,believe me! And it took up to 35 years to get some of them finally imaged and genuinely diagnosed! And no,they have never truely been treated by the medical profession. Why? Many reasons! I want to warn you that if you genuinely have prominent spin injuries that you might as well settle in and make yourself at home! Its a long and very rough road to hoe and often gets worse no matter what and can even become a never ending down hill battle! And despite all the nonsense out there from everyone especially medical arenas and all the expenses, it often does regardless. So first come to grips with that your life is changing and you will one way or another to some extent change with it! We have no choice,”not a game!” Though apparently many think so in all walks of life. This is really all up to you,always has been,always will be. I had not money enough,nor were any willing because of that. So each time when I healed and used exercise to get back to able to work while I lived on and exhausted savings,credit cards ect. I went to the medical profession with pains,symptoms etc that did not go away. When asked what did I do,what happened,how was I injured. Well I explained in great detail and as you see I’m a fair hand at the English language. When I explained that my back bad been broken and how grossly it was done the year before I was laughed at and told,”nonsense,you wouldn’t be walking!” MRI by requisition only from my doctors were refused by my doctors to prescribe! As they told impossible,I think I know everything and tried to blame symptoms of everything but which almost led to my death in 1996. And irreversible kidney damage and a heart attack at 31 yrs old in perfect athletic,muscular shape! Did you know spine injuries can cause multiple kidney stones no matter what your diet is? I know and did but know one would listen,said my diet of fresh raw and cooked vegetables,meat,bread,juice wasn’t perfect and that’s why I had 47 stone come out in a day ,that plagued me for 11 years on and off under their care, when I could afford it. Said it must have been the ketchup? Thats is baby,no more ketchup for me! Uh huh! When the lawers and disability came down on them we finally got answers in 2009! But the drink driver hit me when i was 7? Do some math people!! My first advice to you is check into good lawyers and disability attorney and don’t be afraid to put any medical personnel or institutions butt on the spot or even the 6 o’clock news! I don’t care if the government is paying for it and helping you, that’s all of our money and our system gives blank checks in advance with no avenue of recourse should they play with it or be ignorant. Other than that do your best to survive,”did ya here that families of the injured?” Help them survive and file grievances if necessary! Anyone can,even friends. By gosh and golly absolutely get an MRI if at all posible,and the right kind with dye or what ever is needed! “If you possibly can?” Do I lot of research on the spine and injuries on the internet especially things related to your problems. Get your own copies of xrays and MRI cds that you have in your possession to take for other opinions. You can,it’s the law,they are your records!
    All my vegetables came from the farm where I grew the beef,pork,chicken,turkey ect. Funny thing is when those animals were hurt or sick the spoke no human tongue of any kind? But I still had to treat and help them? And did,often by symptoms and reading sign cause they can not speak with words! Here I was speaking perfect English and “nope,we can’t have any of that around here!” I wouldn’t let one of those nuts trim my nails let alone cut my spine. Come on it took 1/3 century to get a diagnosis and I spoke English. You can do what you want but I will do what I will. But we all need a proper diagnosis so any one can begin to do anything. So I’m cool with getting that if possible,but really that’s about all for me. Had to have been the ketchup,they said that 1400 lb herferd that smashed me through the barn wall had no real effect? I wish you the best of luck. I have and am doing as good or better and much more peaceful than any I’ve encountered that have had any spine surgeries and I know of hundreds having worked construction ect. My secret is sit ups or anything I can pull of that resembles one,it duplicates the fetal position and let’s my spine realign naturally with as little pain as possible. Yes I’m in great pain and have been for years and years but I still some how smile when I think of how close to dead I was. Every moment is a blessing. No I don’t stand or walk far or long and it is pain intense and not pretty,but everyone else is the same or worse with my type injuries and usually far worse and had surgery at least once,some 3 & 4 Times. Sure I’m still disabled but so are they,and I haven’t cost my country 3 million in surgeries ,treatment and therapy . So go figure? Bless ya!

  10. Luana Guzman says

    I was told I have l3/4 disk compressing my nerve roots “mildly” but my feet are burning really bad and numb from arch to toes on bottom. But I had a cervical fusion posterior, as soon I I woke up from surgery my feet was on fire. I’m confused it the burning and numbness come from my cervical or lumbar?

  11. I find going to the doc for a back problem is similar to taking my car to the garage, it’s trial and error. You get the doctor they choose for you and you will probably get the assistant that is not a real doctor but could luck up and make the correct diagnosis. When you get older, expect problems. I have had spinal surgery for scoliosis with rods and fusion. No problems until I had an accident. Take care of your back and don’t do stupid stuff, like lifting heavy objects. Know your limits and don’t let anyone talk you into doing anything you know is going to be a risk. You will suffer for it.

  12. There is a back pain along with a line like pain along the left leg that gets increase on walking. This is becoming difficult for me even to sleep. How could i overcome this problem by doing what kind of excersices. Please suggest me.

  13. We are asking questions, but we are really supposed to make comments.
    Hamisi Nuhu, you need to have an X-ray or scan of some sort. You need a diagnosis. No good doctor should give you medication and send you on your way without trying to discover what your problem is.

  14. what causes the spinous process to move over to the left or right?

  15. June Tomlinson says

    What part(S) of of the body is served from the nerves coming out of L3,4 & 5. Thank you

  16. Laurie spicer says

    Hi there, could you please tell me which nerves coming our at L1 serve which parts of the body?
    Many thanks
    Kindest regards

    Laurie spicer

  17. Patricia a Lynch says

    I would like to know if you can get drop foot from the spinal surgery in the LS 5 area.

  18. Cindy Schmidler says

    I am so sorry for your pain. Please, immediately see your doctor and get a second opinion or recommendation for a specialist. There are many other things this could be and finding out quickly from a qualified back specialist or neurologist is important.

  19. GIllian Snyders says

    I would like to know my husband was at the doctor they said it is Arthrirtis in the spine he has severe lower back pain and even now at the moment pins and needles in his leg and the leg is lame from the hip and cannot feel anything in that area if you pinch it. what can it be. he do not sleep his whole body shakes because of the pain, Help what do we do. tabletts prescribed do not help. what next.

  20. i have a lower back for about two months,i have been given medication but there is NO remarkable change,please help.

  21. Media Partners says

    Joann, There are many fibrous tissues around muscles, and nerves. It could just be a “sleeve” around the muscle, etc. It’s hard to say exactly which fibrous tissue was involved.

  22. I had a desectomy at L5, S1. After the surgery the doctor talked to my husband (very quickly and breifly) and said the piece of bone causing the pain had origined higher up the spine, dropped down perforated a “fibrous tissue” surroundding the neve and was pressing hard directly onto the nerve. He also said this tissue was very inflated but went down once the bone was removed. What is the firbous tissue called?

  23. Media Partners says

    I think you are describing a herniated disk that is causing pressure on the nerve and pain down the leg. We do not offer medical advice. We just try to help you learn about health problems so you can better talk with your doctor or health care team about your own problem.

  24. i think the doctor told,my father problem is loss of the fiber protection of the ligament,the liquid is out and pressure to the nerve. what type surgery is better to this time. father occuring leg pain and very difficult to move

  25. thomas mullen says

    im looking for a picture from the back view showing the lower lumbar region of the back can you help ?

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