Final answer:
Not all hair types have a medulla, which is the innermost zone of the hair shaft. Hair texture and structure are determined by the presence or absence of a medulla, along with the cortex. Straight hair typically lacks a medulla, while curly hair may have one.
Step-by-step explanation:
Not all hair types have a medulla. The medulla is the innermost zone of the hair shaft and is surrounded by the cortex and cuticle. The presence or absence of a medulla, along with the shape and structure of the cortex, determines the texture of the hair. For example, straight hair typically has no medulla, while curly hair may have a medulla.
Learn more about hair without medulla