While a lot of you may know that human hair varies from animal hair, do you know WHY it varies, other than its texture and feel?
This question is important, especially during a forensic investigation when they find evidence. How can they tell that the piece of hair that they found on the carpet is from the suspect or the suspect’s cat?
This can be answered when looking under a comparison microscope. There are many aspects that a scientist has to look at in order to differentiate the hairs; the cuticle, the cortex and the medulla.
The cuticle is the outermost layer and is made of dead cells that form scales. They come in 3 patterns: coronal (crown like), spinous (petal like), an imbricate (flattened). Humans usually have imbricate patterns while animals have spinous or coronal.
The cortex helps determine the colour of the hair. This is done by seeing the amount and type of melanin pigment. High concentrations of melanin will be brown/black and low concentrations will be blonde/red. In humans, the density and distribution of these pigments is consistent throughout the hair but in animals, it is usually denser near the medulla or produce sudden changes (banding).
The medulla is the core of the hair strand and it also has 3 patterns: fragmented, intermittent (similar sized fragments) or continuous. In humans, the medulla is less than 1/3 of the overall diameter and the animals, it is greater than 1/3. There are also different structures: uniserial, multiserial, vacuolated, lattice and amorphous.
This is usually looked at if there is no follicular tag, which is a clear piece of tissue surrounding the hair shaft that is rich in DNA. This is more likely found when hair is forcibly removed and if the hair is in its early growth phase.