Hair and Fibres

Question 1

What substance is hair made of?

Answer 1

keratin

Question 2

Why are hairs considered “good” evidence?

Answer 2

they are persistent, transferable and readily available

Question 3

Approximately how many hairs are lost off the human scalp every day?

Answer 3

100

Question 4

Name the 3 stages of hair growth

Answer 4

anagen, catagen and telogen

Question 5

Describe the anagen stage of hair growth

Answer 5

rapid cell division in the dermal papilla pushes the keratin up and out of the skin for 2-6 years, root is tear-drop shaped

Question 6

Describe the catagen stage of hair growth

Answer 6

cell division rate decreased causing the root to regress and elongate for 1-2 weeks

Question 7

Describe the telogen phase of hair growth

Answer 7

the dermal papilla detaches and secondary germ cells push the club-shaped root up and out of the skin for 5-6 weeks until it is shed and the root matrix can reform

Question 8

What must be present to determine if hair has been forcibly removed?

Answer 8

the hair must be stretched and the follicle must still be attached to the root as it is during growth stages where it would not fall out naturally

Question 9

Name the 3 regions of hair

Answer 9

root, shaft and distal end/tip

Question 10

Name the 3 internal areas of the hair shaft

Answer 10

cuticle, medulla and cortex

Question 11

How can the cuticle of a hair be classified?

Answer 11

coronal, spinious and imbricate

Question 12

Describe the coronal cuticle

Answer 12

looks like a stack of cups, found in small rodents and bats

Question 13

Describe the spinious cuticle

Answer 13

petal shaped, appears to protrude in triangular forms, found in mink, seals, cats and dogs

Question 14

Describe the imbricate cuticle

Answer 14

flattened and irregular, cuticle overlaps with narrow margins, found in humans and other animals

Question 15

Describe the medulla

Answer 15

innermost region of the shaft, cells arranged in a cylinder, can be fragmented, discontinuous or absent, typically absent/highly fragmented

Question 16

How can medullary index be used to identify hairs?

Answer 16

humans tend to have a medullary index of <0.3, and other species over that, calculated medulla diameter / hair diameter

Question 17

Describe the cortex

Answer 17

comprised of spindle cells arranged in parallel (fusiform), contains melanocytes that provide colour and may contain large ovoid bodies, typically in human and cattle hair