Sophie Bennett
Birds have evolved to have a long double-curved neck, which is made up of cervical vertebrae. This long neck helps protect the brain's delicate tissues from jarring when landing and also acts as a shock absorber. The number of cervical vertebrae in birds varies, but chickens have 13 or 14 cervical vertebrae.
| Characteristics | Values |
|---|---|
| Number of cervical vertebrae | 13 or 14 |
| Number of thoracic vertebrae | 7 |
| Number of lumbar vertebrae | 1 |
| Number of sacral vertebrae | 1 |
| Number of coccygeal vertebrae | 5 |
| Total number of vertebrae | 39 |
| Number of fused thoracic vertebrae | 3 |
| Number of fused lumbar and sacral vertebrae | 14 |
| Number of fused caudal vertebrae | 3 or 4 |
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What You'll Learn
Chickens have 13-14 cervical vertebrae
The cervical vertebrae are the bones that make up the neck. Chickens have 13–14 cervical vertebrae, which is quite surprising when you consider that humans only have seven. The long, double-curved necks of birds contain these 14 cervical vertebrae, and the ring-like atlas articulates with the skull at a single occipital condyle. The axis, or epistropheus, is short and projects from the cranial end, passing through the atlas. It has a small process, the dens, which allows the axis to articulate with the occipital condyle.
The vertebral column of a chicken is composed of 39 separate bones, divided into five sections: the cervical vertebrae, the thoracic vertebrae, the lumbar vertebrae, the sacral vertebrae, and the coccygeal vertebrae. The vertebral formula is: C13, T7, L+S14, and C5 = 39. This formula refers to the number of vertebrae in each of the major sections of the column. The atlas-axis at the base of the skull is quite different from all the other bones in the vertebral column. The atlas is small and ring-like, with a deep cavity for articulation with a single projection (the condyle) at the base of the skull.
The cervical vertebrae are just one part of the chicken's skeleton that has evolved to adapt to flight. The forelimb has changed into a wing, with the manus reduced by the disappearance of digits and the fusion of metacarpals. This has removed the need for large and strong forearm muscles. The neck is also long in most bird species, which helps to protect the delicate tissues of the brain from too much jarring when landing. This long neck also acts as a shock absorber and helps the bird reach food on the ground—a rigid body would make this much more difficult.
The bird's centre of gravity is also adjusted by the long neck when it changes from the upright position of perching to the horizontal position of flight. The hipbone is firmly fixed to the vertebral column, and the lumbar and sacral vertebrae are usually treated as one group. The last of the coccygeal vertebrae are fused to form the pygostyle, providing a strong foundation for the tail feathers. The skeletons of poultry are very different from those of farm mammals, not only because the avian skeleton is adapted for flight but also because birds and mammals are only distantly related zoologically.
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Vertebrae are fused for flight
The vertebral column, or spine, is a flexible column of bones known as vertebrae that extends from the neck to the tail in vertebrate animals. Vertebrae protect the spinal cord and provide attachment points for muscles and ligaments. In birds, the vertebral column is composed of five sections: cervical, thoracic, lumbar, sacral, and coccygeal vertebrae.
Birds are adapted for flight, and this is reflected in the structure of their skeletons and individual bones. Bird bones are relatively thin but stiff and dense, with a higher strength-to-weight ratio than mammals. One key adaptation is the fusion of vertebrae to form a rigid spinal column that provides structural support during flight. While mammals have seven cervical vertebrae, birds have between 13 and 14 cervical vertebrae, with the long, double-curved neck acting as a shock absorber during landing. The cervical vertebrae extend from the skull to the first thoracic vertebra, with the first two cervical vertebrae (the atlas and axis) articulating with the skull.
The thoracic vertebrae, of which there are seven, carry the ribs. The second to fifth thoracic vertebrae are fused, providing the rigidity and structural strength necessary for flight. The seventh thoracic vertebra is also fused with the lumbar, sacral, and first coccygeal vertebrae for additional strength. The lumbar and sacral vertebrae are typically treated as a single group due to their close fusion. The last of the coccygeal vertebrae are fused to form the pygostyle, a short section of fused bones that provides a strong foundation for the tail feathers, aiding in flight control.
In addition to the fused vertebrae, birds have other skeletal adaptations for flight. The sternum, or keel bone, provides a large surface area for the attachment of flight muscles, including the pectoralis major and supracoracoideus, which make up a significant proportion of a bird's body weight. The keeled sternum is unique to birds and is absent in flightless birds like ostriches, which have denser and heavier bones. The bones of flying birds are often hollow, reducing weight while maintaining strength, and respiratory air sacs may form air pockets within these semi-hollow bones.
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The atlas and axis are unique
Chickens have 13 or 14 cervical vertebrae, which are located in the neck. The first two cervical vertebrae, the atlas and axis, are unique compared to the other bones in the vertebral column. The atlas is the first cervical vertebra, and it is small and ring-shaped with a deep cavity. It articulates with the skull via a single occipital condyle. The axis is the second cervical vertebra, and it is short with a small process called the dens, which allows it to articulate with the occipital condyle. The atlas and axis form a specialized structure at the base of the skull that provides flexibility and shock absorption for the long, double-curved neck of the bird.
The atlas and axis have distinct roles and structures that set them apart from other cervical vertebrae. The atlas, being ring-shaped, allows for articulation or movement with the skull. This unique articulation enables the bird's head to turn and rotate with a high degree of flexibility. The axis, on the other hand, projects from the cranial end and passes through the atlas. The dens, a small projection on the axis, ensures a smooth and stable connection with the occipital condyle, optimizing the bird's neck movements.
The specialized functions of the atlas and axis are particularly important for birds. They contribute to the bird's ability to adjust its centre of gravity when transitioning between perching, walking, and flying. Additionally, the long neck acts as a shock absorber, protecting the delicate tissues of the brain during landing. This shock absorption is facilitated by the unique articulation between the atlas and the skull, allowing for a certain degree of independence in neck movements.
Furthermore, the reduced size of the bird's skull, an adaptation for flight, highlights the importance of the atlas and axis. By having a smaller skull, the bird minimizes aerodynamic hindrance during flight. However, this reduction in size also means that the neck plays a crucial role in reaching food on the ground. The flexibility provided by the atlas and axis becomes essential for the bird's survival and foraging abilities.
The atlas and axis are numbered as the first and second cervical vertebrae, respectively, indicating their proximity to the skull. This numbering system is consistent across different sources and emphasizes the unique position of these two vertebrae at the base of the skull. Their location allows them to serve as a crucial link between the skull and the rest of the vertebral column, facilitating the necessary movements for the bird's survival and adaptation to its environment.
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The vertebral column has 39 bones
The vertebral column, or spinal column, in chickens is made up of 39 separate bones. These bones are divided into five sections or groups: cervical vertebrae, thoracic vertebrae, lumbar vertebrae, sacral vertebrae, and coccygeal vertebrae.
The vertebral formula, which describes the number of vertebrae in each of these major sections, is C13, T7, L+S14, and C5. This formula adds up to 39 vertebrae, making up the vertebral column. The cervical vertebrae, or the neck vertebrae, are the most numerous, with 13 to 14 vertebrae in this section. This long, double-curved neck acts as a shock absorber and helps the bird reach food on the ground, as well as adjust its centre of gravity when changing from a perch to flight.
The thoracic vertebrae, of which there are seven, carry the ribs. The first three thoracic vertebrae are fused, and all but the last have large ventral processes for muscle attachment. The lumbar and sacral vertebrae are usually treated as one group due to their extensive fusion. They form a long synsacrum that includes several fused caudal vertebrae. The last few caudal vertebrae are fused into a single, flattened bone called the pygostyle, providing a strong foundation for the tail feathers.
The vertebral column is critical for flight, and the fusion of some vertebral sections provides the rigidity and strength required for this function. The avian bone is generally denser than mammalian bone, indicating a higher strength-to-weight ratio in birds. The hipbone is also firmly fixed to the vertebral column, contributing to the overall stability of the skeleton.
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The neck is long to protect the brain
The chicken's skeleton is adapted for flight. The vertebral column is made up of 39 separate bones, divided into five sections: cervical vertebrae, thoracic vertebrae, lumbar vertebrae, sacral vertebrae, and coccygeal vertebrae. The neck, which contains the cervical vertebrae, is quite long in most bird species. This long neck serves to protect the delicate tissues of the brain from excessive jarring upon landing. The neck's flexibility acts as a shock absorber, protecting the brain from injury.
The cervical vertebrae extend from the skull to the first thoracic vertebral body. The atlas-axis, located at the base of the skull, is notably different from the other bones in the vertebral column. The atlas is a small, ring-shaped bone with a deep cavity that articulates with a single projection, or condyle, at the base of the skull. The axis, or epistropheus, is short and protrudes from the cranial end, passing through the atlas. It has a small process called the dens, which allows it to articulate with the occipital condyle.
The number of cervical vertebrae in a chicken's neck varies slightly depending on the source, with most stating there are 13 or 14. These vertebrae provide protection and passage for the spinal cord and nerve roots. The long neck also enables the chicken to reach food on the ground, as a rigid body would make this task more challenging. Additionally, the neck helps the chicken adjust its centre of gravity when transitioning from an upright position to a horizontal flying position.
The chicken's skeleton exhibits extensive vertebral fusion, particularly in the thoracic, lumbar, sacral, and coccygeal regions, to provide the rigidity required for flight. The sternum, a large surface area for the attachment of flight muscles, further contributes to the structural strength necessary for flight. Compared to other animals, the chicken's head is significantly smaller, reducing weight during flight. The bones of the pelvis and vertebral column are also fused, providing additional strength.
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Frequently asked questions
Chickens have 13 or 14 cervical vertebrae.
Cervical vertebrae are bones in the vertebral column that extend from the skull to the first thoracic vertebral body.
The chicken's cervical vertebrae are pneumatic, meaning they are hollow and infiltrated by air sacs.
Yes, many birds have pneumatic bones, including songbirds, penguins, ostriches, turkeys, pheasants, and partridges.
The cervical vertebrae provide passage and protection for the spinal cord and nerve roots.
