Conus medullaris
There are arteries near the sacrum (known as sacral arteries) that also supply blood to the conus medullaris. The sacrum (pronounced say- crum) is a large triangle shaped bone in the lower part of the spine. The middle sacral arteries are known as medial sacral arteries. The side sacral arteries are known as lateral sacral arteries. The medial and lateral sacral arteries supply blood to the conus medullaris.
The fifth lumbar artery supplies some blood to the conus medullaris. The fifth lumbar artery is an artery near the fifth lumbar vertebrae (see first paragraph). The iliolumbar artery also supplies some blood to the conus medullaris. The iliolumbar artery is an artery that originates in the internal iliac artery and supplies blood to the bones and muscles of the pelvis (hip bones). The internal iliac artery is a blood vessel that supplies blood to the pelvis, reproductive organs, and the inside of the thigh.
The conus medullaris is also known as the medullary cone. Conus medullaris comes from the Greek word "konos" meaning "cone," and the Latin word "medius" meaning "middle." Put the two words together and you have "cone middle."
The conus medullaris (shown below) is the end or bottom portion of the spinal cord. It has a bulb- shaped appearance. The spinal cord continues to taper off past the conus medullaris as dangling nerve roots known as the cauda equina. Also shown below is the filum terminale which is flexible tissue that connects the bottom of the spinal cord to the coccyx (tailbone).
In the average adult, the spinal cord ends between the 1st and 2nd lumbar vertebrae (bones that form an opening in which the spinal cord passes). The lumbar vertebrae are located in the lower (but not the lowest) part of the back. There are 5 lumbar vertebrae, which are numbered L1 through L5. L1 refers to the 1st lumbar bone, L2 to the 2nd lumbar bone, L3 to the 3rd lumbar bone, and so on.
The upper part of the conus medullaris often has a border that is not well-defined. There are three main spinal arteries that supply blood to the conus medullaris. Arteries are blood vessels that carry blood away from the heart. Some arteries also branch off from the aorta to supply a lesser amount of blood to the conus medullaris. The aorta is the largest artery of the body.
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