Presentation on theme: "Lecture 10. Definition of the hair General facts about hair The structure of the hair Hair growth cycle Hair loss."— Presentation transcript:
Definition of the hair General facts about hair The structure of the hair Hair growth cycle Hair loss
Definition of hair A hair is a specialized outgrowth of part of the skin called the epidermis.
General facts about hair A human scalp normally has about 100,000 hairs. People with red hair have 25% fewer scalp hairs than those with brown hair; whilst those with blond hair have 25% more scalp hairs than those with brown hair. (This fact may account for the belief that men with red hair are more likely to go bald than anyone else). Hair grows almost throughout the entire body (exceptions include the palms of hands and soles of the feet). The face, for example, is covered in tiny, near-invisible "vellus" hairs.
General facts about hair Hair growth is fastest from the age of sixteen to the late twenties. New hairs grow faster and the growth rate slows down with the increasing length. Attached to the hair follicles are tiny muscles called the erect pili muscles that cause the hairs to become erect. Under the influence of nervous excitation, these muscles contract and cause the hairs to which they are linked to become rigid.
General facts about hair Hair is dead material when it leaves it's root Hair consists mainly of keratin Keratin is an anionic structure pH of hair is between 4.5 and 5.5 A single hair has a thickness of mm, so that hair fibers next to each other make one millimeter. Hair is strong as a wire of iron
Structure of Hair The hair on our scalp can be divided into two parts—the root and the shaft. The root of the hair is inside the skin of the scalp. Each hair root is surrounded by a pouch-like structure called follicle. The base of the hair root is in the shape of a bulb. This bulb is indented by capillaries and nerve fibres. Cell division takes place in the centre of the bulb and the newly divided hair cells push the previous cells up. The cells which move upwards die slowly forming the hard hair shaft.
Hair follicle Hair follicle is a small, curved pit buried deep in the fat of the scalp and is the point from which the hair grows. The hair follicle is well supplied with tiny blood vessels and the blood passing through them nourishes the growing region. Every follicle follows a life cycle of its own
Hair follicle has three vertical segments: Upper portion (Infundibulum) Middle portion (Isthmus) Lower potion (Inferior )
1 – Upper portion – Infundibulum: The part between the exit of hair fiber to the part that sebaceous gland is attached to the hair follicle. The sebaceous gland produces sebum (oil), which lubricates the hair and allows it smooth passage as it grows along the follicle.
2 – Middle portion – Isthmus: The portion between the attachment point of the sebaceous gland and the Arrector pili muscle. The point, which the Arrector pili muscle is attached to the hair follicle, is called “bulge region”.
3 – Lower portion – Inferior: The region spanning the Arrector pili attachment and the basal part of the hair follicle. The basal tip of the hair in the scalp is known as papilla, it is shaped like a doorknob and lying at the tip of the follicle. The papilla contains the blood vessels to supply nourishment to the hair. During the active period the new cell growth pushes the older part of the hair away from the papilla until the hair falls out.
A hair shaft The shaft is the visible portion of the hair It is composed of three concentric layers namely, the cuticle, the cortex and the medulla.
The cuticle Cuticle is the outer layer of hair shaft It is made up of overlapping transparent keratin cells (6-11 layers). Someone with thick, course hair will have more overlapping layers of cuticles than someone with fine hair. The cuticle works like protective scales for the other two inner layers. The cuticle is resistant to chemicals and protects cortex from chemical influences. A healthy cuticle gives a shiny appearance to the hair whereas an unhealthy cuticle lends it a lifeless look.
Cuticle, the outer layer of the hair shaft, defines smoothness and shininess. Hair (cuticle) may get damaged by chemical processes, overexposure to sunlight (UV), too much heat from a dryer, abusive brushing and combing, over-chlorinated swimming pool water, etc.
Cortex The cortex is the second layer of the hair shaft It is the thickest portion of the shaft Cortex determines the bulk, elastisity and strength of the hair Cortex is where moisture and natural pigment "melanin" are held. (No other part of the hair shaft has pigments) Melanin contained in cortex determines the natural color of the hair. The cortex can be modified a bit through dyeing, bleaching and straightening
Natural hair pigmentation It is the cortex which gives the hair its colour. There are two forms of melanin: - Eumelanin: It has a colour varying between brown red and black - Phaeomelanin: its colour varies from yellow to red.
Medulla Medulla is the core (innermost layer) of hair shaft. Sometimes the medulla is absent from hair and hair that lacks medulla is no worse than hair that has medulla. the medulla does not get affected by hair care products or processes.
Hair growth cycle Hair has a dynamic growth structure that includes continuous elongation, thinning and fall out phases. Each hair fiber is independent from each other and might be found in a particular phase of its life cycle. The growth cycle originates from papillae cells at the base of follicles within the skin. The rate of hair growth is 3mm per week
Hair growth cycle The human hair growth cycle involves three stages anagen catagen telogen
Anagen - the period of hair growth. The hair follicles in Anagen phase are thick, healthy and in continuous elongation. Anagen lasts about 3-5 years (which means that, if left uncut, it will grow between approximately cm long). If you're in general good health, up to 90% of your scalp hair will be in anagen at any one time.
Catagen Phase- the transition phase Programmed cell death is initiated within this phase. The dermal papillae shrinks and the hair follicle is elevated within the skin. The hair begins to lose its pigment and gets thinner (club hair). The hair stops growing and detaches from the papillae cells This phase lasts 2-3 weeks. Roughly 2% of our hair is found in catagen phase.
Telogen Phase- the period of rest In telogen phase, thin and depigmented club hair falls out and a new hair follicle is produced by the hair stem cells. Telogen phase lasts an average of 3 months. Approximately 10 % of our scalp hair is in telogen phase. 10 % of the hair follicles of an individual, who has a total of 100,000 hair follicles, are theoretically found in telogen phase. Given this, the loss of an average of 100 hair fibers per day should be considered as normal. When telogen ends, anagen restarts
Note The period of growth (anagen) and rest (telogen) varies from person to person and is affected by diet, health and age. Normally, the dead hair decays at the rate of 100 strands per day. A rate of fall or decay greater than this is considered alarming and such a situation may be termed as hair loss.
Hair loss Hair loss overview Causes of hair loss Types of hair loss Hair loss treatment
Hair Loss Overview About 30% of people have hair loss by 30 years of age, and about 50% have hair loss by 50 years of age. Hair loss is so common that it is usually considered a normal variation and not a disease.
Causes of hair loss Hormonal problems Inadequate nutrition Stress Long-standing diseases Some medicines Tying hair tightly Heredity Dandruff or fungal infection of scalp Accumulation of dirt on scalp
1. Hormonal problems Hormonal problems may cause hair loss. If your thyroid gland is overactive or underactive, your hair may fall out. This hair loss usually can be helped by treatment thyroid disease. Hair loss may occur if male or female hormones, known as androgens and estrogens, are out of balance. Correcting the hormone imbalance may stop your hair loss. In women, hormonal imbalances both during pregnancy and after delivery cause hair fall.
2. Inadequate nutrition or unhealthy diet Inadequate nutrition (e.g. iron deficiency, zinc deficiency and vitamin D deficiency) or unhealthy diet causes hair fall
3. Stress Stress, worry, lack of sleep, and anxiety cause hair fall. Stress Induced hair loss: Telogen effluvium With this less severe type of hair loss, the hair stops growing and lies dormant, only to fall out 2 or 3 months later. Then it grows back within 6 to 9 months. Alopecia areata This type involves a white blood cell attack on the hair follicles. The hair falls out within weeks (usually in patches), but can involve the entire scalp and even body hair. Hair may grow back on its own, but treatment may also be required.
4. Long-standing diseases Long-standing diseases like typhoid, viral infections, anaemia, etc. cause general debility which leads to hair fall. 5. Medicines Some medicines like birth-control pills, anticoagulants, anti-depressants, those used for gout, those used during chemotherapy against cancer cause hair loss. This type of hair loss improves when you stop taking the medicine
6. Diseases Diseases such as lupus or diabetes may cause hair fall. 7. Tying hair tightly Tying hair tightly pulls the hair from the follicles and cause traction alopecia.
8. Heredity Heredity is also responsible for hair fall. “pattern” baldness, is much more common in men than in women. 9. Dandruff or fungal infection of scalp Fungal infections of the scalp can cause hair loss in children. The infection is easily treated with antifungal medicines.
10. Accumulation of dirt on scalp Accumulation of dirt on scalp causes blocking of pores and weakens hair roots. This leads to hair fall.
Types of Hair Loss One useful way to classify hair loss is by whether the loss is localized and patchy or whether it affects large areas or the whole scalp.
Alopecia Areata Alopecia areata usually starts as a single quarter-sized circle of perfectly smooth baldness. Alopecia patches often regrow in three to six months without treatment. Sometimes, hair regrows in white coloration. In another variant, alopecia areata can produce two or three bald patches. When these grow back, they may be replaced by others. The most extensive form of hair loss is called alopecia totalis, in which the hair is lost from the entire scalp and alopecia universale in which the hair is lost from the whole body.
Alopecia Areata (Continue) Alopecia areata is considered an autoimmune condition in which the immune system attacks the hair follicles. Alopecia is also often blamed on "stress“ Treatments for alopecia areata include injecting steroids into affected patches to stimulate hair
Tight braids and ponytails can pull hard enough on hairs to make them fall out. If this happens, it's best to choose hairstyles that put less pressure on hair roots. The sooner this is done the better in order to avoid permanent damage. Traction Alopecia
Tinea capitis is also known as ringworm of the scalp. This fungal infection generally affects school-age children and may spread in schools. It appears as scalp scaling associated with bald spots usually showing broken-off hairs. Oral antibiotics are needed to penetrate the hair roots and cure the infection after which hair grows back. Tinea Capitis (Fungal Infection)
Telogen Effluvium There are several circumstances that alters the hair growth rhythm. As a result, as much as 30%-40% of the hairs can cycle into telogen. Three months later, hairs come out in a massive shedding (effluvium), especially near the front of the scalp.
Androgenetic Alopecia ("Male-Pattern Baldness," "Female-Pattern Baldness") Everyone loses hair, but men do it better -- faster, earlier, and more extensively. Doctors refer to common baldness as "androgenetic alopecia," which implies that a combination of hormones and heredity (genetics) is needed to develop the condition. (The male hormones involved are present in both men and women.)
Male-Pattern Baldness Unlike those with reversible telogen shedding, those with common male-pattern hair loss don't notice much hair coming out; they just see that it's not there anymore.
Female-Pattern Baldness Women lose hair on an inherited (genetic) basis, too, but the female pattern is more diffuse. Although some women may notice hair thinning as early as their 20s, the pace of hair loss tends to be gradual, often taking years to become obvious to others.
Hair Loss Treatment If hair loss is caused by another illness, treatment of the illness is the best treatment for hair loss. If hair loss is the only problem, then there are many ways to treat it depending on how severe the loss is. Treatment options include medications, surgery and wigs, and hairpieces
Medications for Hair Loss Many conditioners, shampoos, vitamins, and other products claim to help hair grow in some unspecified way. These are harmless but useless for hair regrowth. To slow down hair loss, there are two basic options: - Minoxidil (Rogaine) - Finasteride (Propecia)
Minoxidil (Rogaine) This topical application is available over the counter, no prescription is required. It is available as 2% and 5% solutions Rogaine may grow a little hair, but it's better at holding onto what's still there. There are few side effects with Rogaine. One concern with this treatment is the need to keep applying it twice a day (once therapy has started, it must continue indefinitely) and most men get tired of it after a while. In addition, minoxidil is not so effective on the front of the head, which is where baldness bothers most men.
Indications Male pattern baldness (MPB) Female pattern baldness (FPB) (5% concentration is used for men only) Contraindications Patients allergic to minoxidil Patients under 18 years of age (safety is not yet established) Pregnancy
Finasteride (Propecia) This is a lower-dose version (1mg) of a drug that shrinks prostates in middle-aged men (it is originally used for Benign Prostate Hyperplasia, as 5mg tablet) Propecia is available by prescription and is taken once a day. Propecia does grow and thicken hair to some extent, but its main use is to keep hair that's still there. It's therefore best for men who still have enough hair to retain.
One side effect is impotence, but it is reversible when the drug is stopped. It is contraindicated in case of pregnancy as it causes birth defect Taking Propecia once a day is easier than applying Rogaine, but the prospect of taking a pill daily for years doesn't sit well with some men.
Surgery for Hair Loss Surgical approaches include various versions of hair transplantation (taking hair from the back and putting it near the front) or scalp reduction (cutting away bald areas and stitching the rest together). Many transplant patients now take Propecia to keep what they've transplanted.
Wigs and Hairpieces Wigs and hairpieces can provide good results if you are willing to try them.