What is the Difference Between Notochord and Vertebral Column

The main difference between notochord and vertebral column is that notochord is one of the distinguishing features of chordates whereas vertebral column occurs in higher chordates. Furthermore, the notochord is a flexible rod-like structure that lies between the dorsal nerve cord and the gut while the vertebral column is the bony structure containing vertebrae, which protects the spinal cord.

Moreover, both are two supportive structures of chordates. However, in higher vertebrates, notochord only occurs during embryonic development.  It is later replaced by the vertebral column.

Key Areas Covered

1. What is Notochord
     – Definition, Structure, Function
2. What is Vertebral Column
     – Definition, Structure, Function
3. What are the Similarities Between Notochord and Vertebral Column
     – Outline of Common Features
4. What is the Difference Between Notochord and Vertebral Column
     – Comparison of Key Differences

Key Terms

Intervertebral Discs, Notochord, Vertebrae, Vertebral Column, Vertebrates

What is Notochord

Notochord or the primitive spine is a flexible, rod-like structure made up of cartilages. Most importantly, the presence of it is one of the four main distinguishing features of a chordate along with the presence of a post-anal tail, dorsal hollow nerve cord, and pharyngeal slits. Moreover, it is the principal longitudinal anatomical structure of the body of chordates during embryonic development. It persists throughout the lifetime of lower chordates. However, it develops into the vertebral column in higher vertebrates.

Figure 1: Notochord in the Embryo

Furthermore, the notochord forms via infolding blastula by the migration of cells in the midline between the hypoblast and epiblast. These migrating cells are united with the developing central nervous system beneath the notochord. In higher vertebrates, the notochord is incorporated into the vertebral column as the centers of the intervertebral discs, called the nuclei pulposi, which cushion the vertebrae.

What is the Vertebral Column

The vertebral column, spinal column, spine or backbone is the flexible column, extending from the neck to tail, made of a series of bones known as vertebrae. It is made up of bones and serves as a part of the axial skeleton, housing the spinal cord. Apart from its protective function to the spinal cord, vertebral column provide structural support to the body. Additionally, it provides sites for the attachment of muscles including pectoral and pelvic girdles.

Figure 2: Vertebral Column

Moreover, the human vertebral column contains 33 vertebrae. The upper 24 vertebrae are separated by intervertebral disks while the lower 9 vertebrae are fused with each other in adults, forming the sacrum and coccyx. The first seven articulating vertebrae are cervical vertebrae while the next 12 vertebrae are thoracic vertebrae. Moreover, we call the final 5 articulating vertebrae lumbar vertebrae. In humans, the vertebral column is responsible for transmitting body weight while walking and standing.

Similarities Between Notochord and Vertebral Column

• Both are two supportive structures of chordates.
• Both have a mesodermal origin.
• Also, both occur in the head to tail axis, closer to the dorsal part of the body.
• Furthermore, both are skeletal structures.
• And, both are rigid but flexible.
• Moreover, they provide sites for the attachment of muscles.

Difference Between Notochord and Vertebral Column

Definition

Notochord refers to a cartilaginous, skeletal rod, supporting the body in all embryonic and some adult chordate animals while vertebral column refers to the flexible column, extending from the neck to tail, made of a series of bones. Thus, this is the main difference between notochord and vertebral column.

Occurrence

Furthermore, notochord occurs in all chordates during the embryonic stage and in adult lower chordates while vertebral column only occurs in the adult higher chordates. Hence, this is an important difference between notochord and vertebral column.

Made up of

Also, another difference between notochord and vertebral column is that the notochord is made up of cartilages while the vertebral column is made up of bones.

Location

Moreover, notochord occurs between the dorsal nerve cord and the gut while vertebral column occurs surrounding the nerve cord.

Conclusion

The notochord is a rod-like supportive structure present in the dorsal part of the body. In fact, it is one of the main distinguishing features of chordates. However, lower chordates have it throughout their lifetime while it develops into the vertebral column in higher chordates known as vertebrates after the embryonic stage. Therefore, the vertebral column is the supportive structure in the body and it protects the spinal cord. Moreover, the notochord is made up of cartilages while the vertebral column is made up of bones. Therefore, the main difference between notochord and vertebral column is their structure and occurrence.

Reference:

1. “Notochord.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 15 Nov. 2018, Available Here.
2. “Vertebral Column.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 13 Jan. 2014, Available Here.

Image Courtesy:

1. “Gray19 with color” By Derivative of Image:Gray19.png by (presumably) User: The cat – Image:Gray19.png (Public Domain) via Commons Wikimedia   
2. “Illu vertebral column” (Public Domain) via Commons Wikimedia   

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