INTRODUCTION TO ANATOMY AND PHYSIOLOGY

Hair Types

THERE ARE 3 MAIN TYPES OF HUMAN HAIR LANUGOVELLUS AND TERMINAL

Lanugo Hair: This is the soft, thin, and generally unpigmented hair found on the foetus (before birth) or new-born (usually disappears after a few weeks).   It is present from 16 – 20 gestation (at its most prolific).  This type of hair is replaced by Vellus hair (see next paragraph) and covers the same area as the lanugo Hair but is barely visible as it is very fine.

 

Vellus Hairs: These are short light or translucent fine and short hairs that do not have any pigmentation – they cover most areas of the body from childhood. These hairs are not affected by hormones (unlike Terminal Hair). They often referred too as “peach fuzz”.  They are common in young boys before the onset of puberty on the upper lip.  There is no connection to the follicles and the sebaceous glands and are approximately 2mm in length. The bulb of the follicle is located in the upper dermal layer.

There is some evidence indicating a connection between the activity of sebaceous glands and the growth of vellus hairs. Since vellus hairs have no underlying sebaceous glands, pre-pubertal children do not develop acne and other skin conditions which are associated with these glands. Vellus hairs can be more prominent on females and children because they do not have as many terminal hairs as adult males, which tend to obscure vellus hairs.

 

Terminal hairs – are thick, long, and dark, as compared with vellus hair.  During puberty, the increase in androgenic hormone levels causes vellus hair to be replaced with terminal hair in certain parts of the human body. These parts will have different levels of sensitivity to androgens, primarily of the testosterone family (male hormones).

The pubic area is particularly sensitive to such hormones, as are the armpits which will develop axillary hair. Pubic and axillary hair will develop on both men and women, although males will develop terminal hair in more areas. This includes facial hair, chest hair, abdominal hair, leg and arm hair and foot hair. Human females on the other hand can be expected to retain more of the vellus hair.

 

DIFFERENCES BETWEEN VELLUS AND TERMINAL HAIR

Vellus Hair is short, thin hair that has little colour, and is barely noticeable. You’ll see it most in childhood (not the same as lanugo hair on foetuses). Terminal hair is mature hair. Thick, strong, and pigmented (or grey). This is hair on the head, pubic, under arms, face of men. The growth of terminal hair is influenced by hormones.

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