Pronunciation: [nˈɒtəkˌɔːd] (IPA) 
The word "notochord" is spelled /ˈnoʊ.tə.kɔːrd/. The "o" in the first syllable is pronounced as a long "o" sound /oʊ/ and the "ch" in the second syllable is pronounced as a hard "k" sound /k/. The "or" in the final syllable is pronounced as a long "o" sound as well /ɔːr/. The notochord is a flexible rod-shaped structure found in the embryos of all chordates, providing skeletal support and playing a key role in embryonic development.
The notochord is a defining characteristic of chordates, a group of animals that includes vertebrates and some invertebrates. It is a rod-like, longitudinal structure that runs along the midline of the body, situated just below the nerve cord. This flexible, cartilaginous or fibrous structure provides structural support and defines the main axis of the embryo during early development.
In vertebrates, the notochord serves as a precursor to the spinal column, becoming the central core of the vertebral column in most species. It functions as a developmental scaffold, around which the vertebrae and other skeletal structures form. As the embryonic notochord develops, it also releases chemical signals that influence the development of nearby tissues and organs.
The notochord is composed of specialized cells that produce and secrete a unique extracellular matrix called notochordal sheath. This matrix provides mechanical support and elasticity to the notochord. In some invertebrate chordates, such as tunicates or lancelets, the notochord persists into adulthood, retaining its role as a structural element and a central axis for muscle attachment.
Overall, the notochord plays a vital role in the early development and organization of chordate animals. Its presence and function are crucial for the formation of an axial skeleton and the proper development of the nervous system, making it an important structure in understanding the evolutionary relationships within the animal kingdom.
A cartilaginous or fibrocellular rod in the young embryo, constituting the primitive spinal cord or chorda dorsalis.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.
In anat., an extremely delicate fibrous band, with successively accumulated gelatinous cells, compacted in the form of a cylindrical column, forming the primary condition of the spine in vertebrate animals.
Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874.
The word "notochord" originates from the Greek word "noton", meaning "back" or "spine", and "khordē", meaning "cord" or "string". The term was coined in the early 19th century and was used to describe the flexible rod-like structure found in the early embryonic stage of vertebrate animals. This structure later develops into the spinal column or backbone in more advanced vertebrates.
