See vertebral column. Any of various pointed projections, processes, or appendages of animals. A sharp-pointed projection on a plant, especially a hard, narrow modified leaf, as on a cactus, that is adapted to reduce water loss.

Compare thorn. See more at leaf. The number of vertebrae in the spines of reptiles is highly variable, and may be several hundred in some species of snake.

In birds, there is a variable number of cervical vertebrae, which often form the only truly flexible part of the spine.

The thoracic vertebrae are partially fused, providing a solid brace for the wings during flight. The sacral vertebrae are fused with the lumbar vertebrae, and some thoracic and caudal vertebrae, to form a single structure, the synsacrum , which is thus of greater relative length than the sacrum of mammals.

In living birds, the remaining caudal vertebrae are fused into a further bone, the pygostyle , for attachment of the tail feathers. Aside from the tail, the number of vertebrae in mammals is generally fairly constant.

There are almost always seven cervical vertebrae sloths and manatees are among the few exceptions , followed by around twenty or so further vertebrae, divided between the thoracic and lumbar forms, depending on the number of ribs.

There are generally three to five vertebrae with the sacrum, and anything up to fifty caudal vertebrae.

The vertebral column in dinosaurs consists of the cervical neck , dorsal back , sacral hips , and caudal tail vertebrae.

Saurischian dinosaur vertebrae sometimes possess features known as pleurocoels , which are hollow depressions on the lateral portions of the vertebrae, perforated to create an entrance into the air chambers within the vertebrae, which served to decrease the weight of these bones without sacrificing strength.

These pleurocoels were filled with air sacs, which would have further decreased weight. In sauropod dinosaurs, the largest known land vertebrates, pleurocoels and air sacs may have reduced the animal's weight by over a ton in some instances, a handy evolutionary adaption in animals that grew to over 30 metres in length.

In many hadrosaur and theropod dinosaurs, the caudal vertebrae were reinforced by ossified tendons. The presence of three or more sacral vertebrae, in association with the hip bones, is one of the defining characteristics of dinosaurs.

The occipital condyle is a structure on the posterior part of a dinosaur's skull that articulates with the first cervical vertebra.

From Wikipedia, the free encyclopedia. For other uses, see Spine. Bony structure found in vertebrates. This article's lead section does not adequately summarize key points of its contents.

Please consider expanding the lead to provide an accessible overview of all important aspects of the article.

September Main article: Vertebra. Main article: Spinal cord. Anatomy portal. This article uses anatomical terminology.

Functional anatomy of the vertebrates: an evolutionary perspective. Harcourt College Publishers. Biology: A Guide to the Natural World.

Benjamin-Cummings Publishing Company. Gray's anatomy for students. Gray's Anatomy. New York: Crown Publishers, Inc. Anatomy Atlase. Retrieved June 11, Churchill Livingstone ed.

Anatomy and Human Movement: Structure and Function. Retrieved 29 January Gray's anatomy for students Pbk.

Enumeration and interrelationships in staged human embryos, and implications for neural tube defects".

Cells Tissues Organs. Dorland's Illustrated Medical Dictionary 32nd ed. Elsevier Saunders. Current Reviews in Musculoskeletal Medicine.

May 6th Science Daily. Retrieved 25 July Developmental constraints, Hox genes, and cancer" PDF. The Journal of Experimental Zoology. There was an error submitting your subscription.

Please try again. Email Address. Keep scrolling for more. Synonyms for spine Synonyms backbone , chine , spinal column , vertebral column Visit the Thesaurus for More.

Examples of spine in a Sentence This X-ray shows her spine. Recent Examples on the Web What was important to me with The Nutcracker was to create something that had a real spine to it, that had my take on it.

First Known Use of spine 15th century, in the meaning defined at sense 1a. History and Etymology for spine Middle English, thorn, spinal column, from Latin spina ; perhaps akin to Latin spica ear of grain.

Learn More about spine. Time Traveler for spine The first known use of spine was in the 15th century See more words from the same century.

From the Editors at Merriam-Webster. Most users access Spine through clinical systems or through the Spine portal.

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