What is the Posterior Scalp?
The posterior scalp refers to the back of the scalp. It is the area that is below the crown of the scalp, extending to the nape of the neck. The opposite of the scalp’s posterior is the anterior scalp, which includes the frontal hairline, temporal regions, and the area immediately after the hairline, but stopping right at the mid-scalp.
Is the Crown Part of the Posterior Scalp?
No, but the crown is often mistakenly referred to as the posterior scalp since it is towards the back. The crown is actually considered its own region, starting behind the midscalp, and ending where the scalp dips down to form the occipital region. The whorl, a tight spiral pattern of hair growth that determines the scalp’s overall hair geometry, is located in the crown region.
What is the Occipital Scalp?
The occipital scalp is a part of the posterior area that begins below the crown region, roughly at the horizontal mid-line. Keep in mind that the occipital scalp covers a large portion of the back of the head. In hair transplants, however, a very specific portion of the occipital scalp is considered an optimal area for extracting follicular hair units. In general this is referred to as the "donor zone". The donor zone in the occipital scalp varies from patient to patient and can be larger or smaller depending on the type of procedure being performed, FUE or FUSS.
The External Occipital Protuberance
Though follicular units may be harvested from many areas throughout the body, one area in particular is most commonly utilized. The external occipital protuberance is a bump on the back of the head where the most preferable type of hair grows. Donor hairs can be taken from any part of the occipital scalp, though follicular units from this area tends to work best.
Why is the Occipital Scalp Preferable for Hair Transplants?
Occipital scalp hairs – particularly those growing along the external occipital protuberance – are some of the sturdiest hairs to be found anywhere on the scalp. Hairs in this area have a tendency to remain on the scalp the longest, even during most stages of advanced hair loss. Occipital scalp hairs are the last to go because they are normally highly resistant to dihydrotestosterone (DHT). DHT is a male sex hormone that can bond to the cells of hair follicles that have a DHT receptor. When DHT attaches to hair follicles in sufficient quantities the hair follicles begin to shrink, and eventually stop growing altogether. This process is called miniaturization, and it is the primarily cause for male pattern hair loss (MPH). Occipital hairs often resist miniaturization well into the very late stages of life. Sometimes, they can even resist miniaturization for a lifetime. It is important to note that not everyone is susceptible to the effects of DHT; it is a genetic vulnerability that some people do not have. Those who are not vulnerable to the harmful effects of DHT will not have their hair follicles miniaturized at all.