In the hair grafting sector we know the term "graft", "hair follicle", or follicular unit as a group of follicles (hairs). The hairs are grouped in the form of follicular units.
We have approximately 90,000-150,000 hairs on the scalp. This number varies from person to person according to density.
Humans have approximately 120 to 260 hairs per cm2 (60-120 follicles cm2) with a total of 90,000-150,000 in the whole head.
No. As each follicular unit can have 3 or 4 hairs, therefore the number of follicular units is not equal to the number of hairs.
For us, 2400 follicular units would correspond to approximately 4800 to 6000 hairs, depending above all on the number of 3 and 4 hair follicular units in the patient's donor area.
In this case of 4800 hairs, the patient would have a low follicular density, but in the case of 6000 hairs, the patient would have a good follicular density.
A patient with 60 follicles/cm2 corresponds to approximately = 120-140 hairs/cm2.
Another patient with 90 follicles/cm2 corresponds to approximately = 180-200 hairs/cm2.
Therefore, when we walk down the street we see people with a lot of hair (greater hair density) and others with less volume (less hair density).
Composition of a follicular unit.
Hair does not grow indefinitely, but has a cyclic growth, which is called the hair follicle cycle.
Every follicle has its own cycle, independent of those around.
|Growth depending on type of hair||Duration of the Anagen phase|
|Hair||3-5 years (1095-1825 days)|
|Beard||1 year (365 days)|
|Body hair||13-15 weeks (91-105 days)|
|Eyebrows||1 month (30 days)|
|Moustache||4-14 weeks (28-98 days)|
Every 2 days and 9½ hours, any hair grows at least one millimetre more.
In men, growth is approximately 1 cm per month.
In women, growth is approximately 1 to 1.5 cm per month.