Hair Flashcards
dead material when it leaves its root (we do not feel pain on hair cutting).
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average lifetime of 2-6 years and this period is responsible for the maximum hair length.
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Baby hair begins to grow around the
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After that, the number of hairs never…….. It just ……..
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Hair is composed of strong structural protein called…..
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Each hair consist of two parts:
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Each hair consists of three layers
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present in thick hairs.
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provides strength, color and texture.
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thin and colorless.
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outermost layer or the cuticle
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innermost layer or medulla
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The hair root is enclosed …
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Is the point from which the hair grows and is buried deep in the fat of the scalp
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At the base of the hair follicle is the…
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Conatin blood capillaries and receptor for androgen
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The hair follicle can be divided into two regions:
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The hair bulb:
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structure of actively growing cells, which eventually produce the long fine cylinder of the hair.
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As they grow and develop, they steadily push the previously formed cells upwards.
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When the cells reach the upper part of the bulb they begin to….., and they arrange themselves into six cylindrical layers, one inside the other.
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The inner three layers of cells become the actual hair and the outer three layers become the lining of the hair follicle.
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Special cells in the hair bulb (melanocytes) produce the ….. (melanin ) that colors the hair.
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The mid-follicle region
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In this part, the actively growing cells die and harden into what we call a hair.
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As the cells below continue to divide and push upwards, the hair grows….. out of the skin.
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It now consists of a mixture of different forms of the special hair protein….
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plays an important part in the way the hair behaves, especially when it is given cosmetic treatments.
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Some of these keratins contain a high level of ……., some much less
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The hair shaft
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This is the part of the hair that can be seen above the scalp.
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It consists mainly of dead cells that have turned into …… and binding material, together with small amounts of water.
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…… are lubricated by a natural oil (sebum) produced by the sebaceous glands of the follicles.
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How much natural oil your glands produce is mostly determined by your ………. and more oil is produced when levels of …………
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It consists of three main layers: .
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The cuticle
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The cortex
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The medulla
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Each hair can be compared to a …….
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all its moisture lies in its center, behind a tough outer layer of protective bark.
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If the ‘bark’ of the hair is well looked after,…..
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If the ‘bark’ is stripped off to expose the center……
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Is made from 6 to 11 layers of overlapping semi-transparent (contain no natural pigments) scales
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These scales are separated, flattened, horny, and can move ……, overlap over each other.
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The gaps between these scales contain ……. which impart sheen and maintain the condition and …… of the hair.
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The scales lie along the surface of the hair like …….with their free edges directed towards the tip which allow the hair to be stretched.
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Cuticle damage result to ……
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Intact cuticle cell are ……and reflect …. from their surface
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It consists of spindle shaped cells, ……….. lying along the length of the hair.
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These keratin fibers are made of ………….., and are compressed into ………
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These are held together by a mass of ………
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………..is extremely strong and resists stretching and other strains such as twisting
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The strength and elasticity of the hair is due, ………
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The cortex also contains granules of the hair pigment
……, produced when the hair was growing in its follicle.
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The granules are of two types:
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smooth, dark granules which tend to be
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lighter granules that are more irregular in shape and are
scattered randomly through the ……..
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A ….. may contain just one type of granule or a mixture.
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In some of the terminal hairs, especially gray
(unpigmented) ones, the cortex has a central hollow core, the …..
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The medulla:
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Occupy the middle of the hair fiber.
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Consists of hollow cells composed of soft protein and ……….. properties of the fiber.
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and they play a part in the regulation of body temperature.
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in the hairs of many animals
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Bonding in keratin protein
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There are many bonds that keep the……..
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The hydrogen bond
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Is responsible for the ability of the hair to be ……… (elasticity) and return back to its original shape.
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Are much weaker than the disulphide
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more easily broken whenever the hair is wetted, and form again as it dries.
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If the wet hair is coiled onto rollers,….
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if it is dried on the rollers it ….
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The change in shape is only …… and lost when the hair is dampened, because the new …….are broken again.
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The salt bond
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is an ionic bond formed by the electron transfer from the side chain of a ….. to the side chain of an ……
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is responsible for approximately 35% of the strength of the hair and 50% of the hair’s elasticity.
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The Sugar Bond
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➢is formed between the side chain of an ……. having an OH group and an ……..
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It gives the hair toughness but little strength .
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The cystine bond
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It is also known as the disulfide bond, sulfur bond, S-S bond or just S bond.
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It is formed by cross links between ………(amino acids) of the main ……. chains
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is strong and a single hair can support a load of about 100 grams without breaking.
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You could even spin rope out of hair.
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The keratin protein of the …… is responsible for this unusual strength.
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The long keratin molecules in the cortex are compressed to form a regular structure, which is not only ……
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Keratin contains high concentrations of…….
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Every cystine unit contains two ……..n different chains which are linked together by two ……, forming the forming the
strongest bonds known anywhere in nature.
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Many ……. form down the length of the keratin chains, joining them together like the rungs of a ladder.
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For a healthy individual with no hair diseases, hair fiber is very strong with tensile strength around 1.6 x10-9 N / m2 = copper wire of the same diameter.
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So how does hair break if it is so strong?
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It depends on the speed at which the pulling force is applied to the hair. slowly and steadily with gradual increasing force, the hair ……
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But sudden force and yank on the hair will break.
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So despite the apparent strength of hair, it will break if you brush or comb too vigorously because this applies a sudden force to the hair.
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Can you hang by your hair ?
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The short answer is, yes.
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The primary limiting factor is the …….l rather than the strength of hair.
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For a healthy individual with no hair diseases, hair fiber is very strong and the key weak spot……
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is the strength by which the hair fiber is anchored in the hair follicle in the skin.
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The primary limiting factor is the …….rather than the strength of hair.
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For a healthy individual with no hair diseases, hair fiber is very strong and the key
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The average ……… for normal anagen (growing) hair is 70g.
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The hair growth cycle
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Each individual hair is formed inside a hair bulb deep in a hair follicle.
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Hair follicles grow in repeated cycles from baby’s birth and for several decades with no stop.
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Anagen
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Catagen.
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Transitional phase
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Telogen
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Resting phase
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Each hair passes through the phases independent of the neighboring hairs. .
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The length of the cycle varies with the individual, and also with the part of the body on which the hair is growi
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This phase starts at the moment a new hair begins to grow.
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At that time, there is very active growth (the highest ever) in the hair bulb.
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This usually lasts for 3-7years, without interruption.
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Since human hairs grow at a rate of roughly 1 cm/month, hairs can grow to a length of a meter or more.
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Approximately 80-85% of all hairs are in the growing phase 20-15% in the other phases
at any one time.
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is made in the hair bulb throughout this phase of the hair cycle and less pigment is made in the hair of older people.
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That why white hairs start to appear, even though the hair itself may still be growing strongly.
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As people grow older the period of anagen shortens, the follicles gradually give up and the hairs become ………
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Over the years, the number of follicles capable of growing hair …… naturally.
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The decline is especially noticeable…..
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Some follicles increasingly produce only fine, short non- pigmented hairs that look more like ……
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In older women, this leads to a general
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In …… it tends to lead to common baldness.
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If you look at a bald scalp you will see these fine, poorly pigmented hairs.
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Plucking a hair from a follicle brings…….
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Nothing interrupts the activity of the hair follicle.
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Nothing that is put on the scalp or hair can interfere with the growth of the hairs.
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Only severe burns or scars can affect the hair follicle.
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Certain drugs that are given for cancer treatment can prevent hairs from growing.
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However, the interruption is only temporary and hairs begin to grow again when the medication is stopped.
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It lasts about one or two weeks
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The hair follicle ……. due to disintegration and the dermal papilla detaches and “rests”, cutting the hair strand off from its nourishing blood supply.
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Ultimately, the follicle is 1/6 its original length, causing the hair shaft to be pushed upward.
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While hair is not growing during this phase, the length of the terminal fibers increase when the follicle pushes them upward
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No pigment is made during that time.
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resting phase
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This phase lasts for 3-4 months.
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During this time, the hair…..
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At the end of this phase, the hair follicle ……
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………… join together again and a new hair begins to form.
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As it grows upwards, the old hair will be shed naturally or may be pulled out….
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These are the hairs that come out when you shampoo or brush your hair.
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The new hair emerges from the same opening at the surface of the skin as the old one, and the hair cycle begins again.
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It is easy to remember the lengths of the different phases of the growth cycle.
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The anagen phase of scalp hair follicles typically persists
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is a major determinant of the maximal hair length.
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is only 70 days,while eyelashes grow for 100–150 days.
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Telogen effluvium
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scalp disorder characterized by massive hair loss
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resulting from the early entry of hairs into the telogen phase.
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eating disorders
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fever
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chronic illness,
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major surgery,
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sever emotional stress,
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hypothyrodism
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drugs
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childbirth
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the follicles enter the catagen then to the telogen phase)
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Hair loss can happen after one pregnancy but not the next.
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Normal shampooing can continue because hairs were going to come out anyway
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No special treatment is needed
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What controls hair growth?
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No one can answer this question with certainty.
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General health and nutritional factors are …….. believed to be important for healthy hair growth.
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Many alcoholics have poor hair growth or even hair loss because their way of life tends to lead to ……..
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Some minerals may be particularly important for hair growth where some people who lack …….. in their diet produce only fine, sparse hairs and even loose their hair
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plays a part in hair growth
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It also improves the physical properties (elasticity, strength and gloss) of the hair shaft.
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Vitamin B.
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The hair cycle for each individual hair is influenced by the
levels of various ……. in the blood.
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speeds up growth in resting hair
follicles.
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slow it down while inhaled one does not
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Oral steroids
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is most sensitive to the effects of
androgens hormones
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change to terminal hairs due to rise in androgen levels
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slow down hair growth
during the growing period but also make that period longer.
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What is the maximum length that hair can grow to?
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between 0.3 to 0.35mm a day
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The scalp hair fiber growth rate is
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The active hair fiber growth phase may last from
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1000 to 2000 day.
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In normal haired individuals about 80% of hair follicles are in a ……….with the remaining 20% in ……
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Hair follicle density on the scalp is
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200-300/cm2 ,
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about 100,000 to 150,000 hairs total).
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If you put it all together in a calculation, the research would suggest that the maximum length scalp hair can grow to is between …….;
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The upper limit to scalp hair length is determined by our …..
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Does cutting hair promote new growth?
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is a common belief that cutting the hair stimulates ….. hair growth or …. and ….. hair.
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this belief is not true
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if it is cut there is no way for it to send a signal back to the hair follicles in the skin to grow more hair.
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