Anatomy of Hair Transplantation: Skin Grafts & Follicular Units
Anatomical basis of follicular units and ethnic variations in hair characteristics.
Clinical classification: FUE is a micro-skin graft procedure involving punch extractions of less than 1% body surface area.
Grafts vs. Hairs
14 grafts containing 39 hairs
The Follicular Unit (FU)
- 1–4 Hair Follicles
- Sebaceous (Oil) Glands
- Arrector Pili Muscle
- Neurovascular Plexus
- Connective Tissue Sheath
Graft vs. Hair Distinction
Graft: One transplanted Follicular Unit (contains 1-4 hairs).
Hair: The individual shafts within that graft.
Example: 2,000 grafts typically yields 3,500–4,500 hairs.
Ethnic Variations in Hair Anatomy
Comparative Hair Characteristics by Ethnicity
| Characteristic | Caucasian | African | Asian |
|---|---|---|---|
| Hair Density (hairs/cm²) | ~200 | ~160 | ~170 |
| FU Density (units/cm²) | ~100 | ~60 | ~90 |
| Hair-Graft Ratio | 2.3 | 2.3 | 1.8 |
| Shaft Diameter | 0.07 mm | 0.06 mm | 0.08 mm |
| Hair Shape | Curly/Wavy | Curly/Coiled | Straight |
| Follicle Length | ~4.5 mm | Variable | ~5.5 mm |
Follicular Unit Distribution in Chinese Scalps
Regional Density (FU/cm²)
| Group | Back |
|---|---|
| Men (Normal) | 80 |
| Men (Bald) | 68 |
| Women (Normal) | 72 |
| Women (Bald) | 69 |
FU Composition (%)
| Group | 1-Hair | 2-Hair | 3-Hair | Ratio |
|---|---|---|---|---|
| Men | 29% | 52% | 17% | 1.92 |
| Women | 33% | 49% | 16% | 1.87 |
Biological Timeline of a Transplanted Graft
Day 0: Implantation — graft relies on plasma diffusion.
Days 1–7: Inflammatory phase — edema and white blood cell influx.
Weeks 1–3: Revascularization — new blood vessels form.
Weeks 2–8: Anchoring and shedding — hair shaft sheds (normal). Follicle remains.
Months 3–12: Regrowth phase — new hair grows and thickens over time.
Clinical Relevance
Natural Appearance
Transplanting intact FUs supports natural hairline design.
Treatment Planning
Donor density measurement allows coverage calculation.
Donor Management
Efficient harvesting helps preserve donor supply.
Growth Timeline
Understanding the shedding phase supports patient expectations.