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Hair Structure Cuticle Structure of Hair Hair Structure Hair is composed of three principal parts: Cuticle – outer coating composed of overlapping scales Cortex – protein-rich structure around Medulla – central core the medulla that contains pigment (may be absent) The structure of hair has been compared to that of a pencil with the medulla being the lead, the cortex being the wood and the cuticle being the paint on the outside. http://library.thinkquest.org/04oct/00206/lesson.htm#t_hair Structure of Hair Hair under the microscope • Basic components: keratin (a protein), melanin (a pigment), and trace quantities of metallic elements (Cu, Fe, Mn,etc). • Elements are deposited in hair during growth and absorbed by the hair from external environment. Hair Structure Cuticle The cuticle varies in: • Its scales, How many there are per centimeter, How much they overlap, Their overall shape, and How much they protrude from the surface • Its thickness, and • Whether or not it contains pigment. Characteristics of the cuticle may be important in distinguishing between hairs of different species but are often not useful in distinguishing between different people. Info: http://library.thinkquest.org/04oct/00206/lesson.htm#t_hair Image: http://www.hairdressersus.com/micro/Image5b.jpg HAIR SHAFT Cuticle – First Layer • The cuticle is a translucent outer layer of the hair shaft consisting of scales that cover the shaft. • The cuticle scales always point AWAY from the root end - toward the tip of the hair. • The cuticle is a GOOD WAY to tell species apart The Cuticle of Human Hair is rough --- which is why we use Conditioner Cuticle under the microscope Cuticle Scales: Coronal • Scales show crown- shaped pattern • Found in small rodents and bats • Coronal pattern is NEVER seen in human hair FREE-TAILED BAT HAIR CUTICLE SCALES: SPINOUS • Spinous - petal-like scales are triangular in shape and protrude from the hair shaft. • Spinous are found close to the body on mink, and on seals, sea lions, fox and cats • Never found in humans. CUTICLE SCALES: IMBRICATE • The imbricate (brick- like) or flattened scales. Consists of tightly overlapping scales with narrow margins between the scales. • Usually only found in human hair (and some animal species). Hair Structure Cortex CORTEX • The area between the cuticle and the core of the hair. • Contains all the pigment granules, ovoid bodies and any moisture PIGMENT GRANULES • Pigment granules are small, dark, and solid structures that look like grains of sand • They contain melanin • In humans, pigment granules are found in the cortex closest to the cuticle • Animal hairs have pigment granules only in the medulla. Human Rat Hair Structure Medulla The medulla may vary in: • Thickness • Continuity - one continuous structure or broken into pieces • Opacity - how much light is able to pass through it • It may also be absent in some species. Like the cuticle, the medulla can be important for distinguishing between hairs of different species, but often does not lend much important information to the differentiation between hairs from different people. http://library.thinkquest.org/04oct/00206/lesson.htm#t_hair http://www.bfro.net/images/whatis/figures/Fig.%203%20with%20caption.jpg Medulla – in the middle of the hair • The medulla is a central core of cells that may be present in the hair. • Human hair - the medulla unorganized, random pattern • Animal hair - structure is well defined • Some medullary patterns: CONTINUOUS INTERRUPTED FRAGMENTED ABSENT Medulla Patterns . Broken . Intermittent . Continuous The Medulla of Human Hair is very thin or is not present Continuous Medulla • Medulla has solid continuous medulla through the entire hair shaft. • No breaks or gaps Upper - human hair Lower - lattice pattern of a deer Medulla - Interrupted • Pattern is repeated over and over in the hair shaft at regular intervals. • Common in rodent hair (rats, mice, guinea pigs, ferrets, bats) Guinea Pig Multiserial ladder (rabbit) Mouse FE Ferret FRAGMENTED • Bubbly or cellular medullary area • Center of hair shaft appears hollow with bubble or cell-like pattern but can have a few parts visible • Most common in human hair but can be found in animals Human Cow Absent Medulla • No discernable medulla visible • Can be found in Human human hair and animal hair Human Silver fox Summary The structure of hair has been compared to that of a pencil with the medulla being the lead, the cortex being the wood and the cuticle being the paint on the outside. • The cuticle is a transparent outer layer of the hair shaft. It is made of scales that overlap one another and protect the inner layers of the hair • the cortex is the largest part of the hair shaft and contains most of the pigment granules (melanin) that give the hair its color. • The center of the hair is called the medulla. It can be a hollow tube, or filled with cells First page Make a foldable Second Page End Result Outer Contains Center scaly pigments of Hair layer Very Spongy thick in Used layer animals to Can deter contain mine Determines pattern specie shape of ed cells s hair or be hollow transparent Imbri- - cate in human s Cortex Cuticle Medula.
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