m →References: WP:CHECKWIKI error fixes + genfixes using AWB (7408) |
m →References: Date maintenance tags and general fixes: build 572: |
||
Line 150: | Line 150: | ||
{{Development of nervous system and integument}} |
{{Development of nervous system and integument}} |
||
{{Use dmy dates|date=September 2010}} |
{{Use dmy dates|date=September 2010}} |
||
{{DEFAULTSORT:Human Hair Growth}} |
{{DEFAULTSORT:Human Hair Growth}} |
||
[[Category:Hair]] |
[[Category:Hair]] |
Revision as of 02:40, 29 November 2010
Template:Sidebar with heading backgrounds
Human hair grows everywhere on the body except for the palms of the hands, soles of the feet, the lips, and the eyelids, apart from eyelashes. Like skin, hair is an epithelium. Unlike skin, it is stratified squamous, keratinized epithelium because it is made of multi-layered, flat cells and contains the protein keratin, whose rope-like filaments provide structure and strength to the hair shaft.
Hair follows a specific growth cycle with three distinct and concurrent phases: anagen, catagen, and telogen phases. Each phase has specific characteristics that determine the length of the hair. All three phases occur simultaneously; one strand of hair may be in the anagen phase, while another is in the telogen phase.
The body has different types of hair, including vellus hair and androgenic hair, each with its own type of cellular construction. The different construction gives the hair unique characteristics, serving specific purposes, mainly warmth and protection.
Normal growth
There is no one regimen a person can follow that ensures a healthy head of hair. One's lifestyle, diet and hair type should all be considered when attempting to adopt a routine to develop and maintain healthy hair.
Diet
Promoting hair growth
- Protein: fish, eggs, cheese
- Iron: whole grain, dark leafy vegetables
- B Vitamins: eggs, meat
- Essential Fatty Acids: walnuts, soy
- Vitamin E: nuts, seeds
- Sulfur: meats, legumes, vegetables [1][medical citation needed].
Stunting hair growth
- Coffee
- Sugar
- Fat
- Carbonated Drinks [1][medical citation needed].
Exercise
Exercise stimulates the blood to flow. This nutrient-rich blood nourishes each hair follicle, promoting healthy hair growth.[2] Lack of this sufficient blood flow would yield the growth of duller, more brittle hair.[3] Apart from supplying the follicle with nutrient-rich blood, exercise also helps to alleviate stress, which is known to cause hair loss.[4]
Growth cycle
The three stages of hair growth are the anagen, catagen, and telogen phases. Each strand of hair on the human body is at its own stage of development. Once the cycle is complete, it restarts and a new strand of hair begins to form.
Anagen phase
The anagen phase is known as the growth phase.[5] It begins in the papilla and can last up to eight years.[6] The span at which the hair remains in this stage of growth is determined by genetics.[7] The longer the hair stays in the anagen phase, the faster and longer it will grow. During this phase, the cells in the papilla divide to produce new hair fibers, and the follicle buries itself into the dermal layer of the skin to nourish the strand.[6] About 85% of the hairs on one's head are in the anagen phase at a given time.[5]
Catagen phase
Signals sent out by the body determine when the anagen phase ends and the catagen phase begins. The catagen phase, also known as the transitional phase, allows the follicle to, in a sense, renew itself. During this time, which lasts about two weeks, the hair follicle shrinks due to disintegration and the papilla detaches and "rests", cutting the hair strand off from its nourishing blood supply. Ultimately, the follicle is 1/6 its original length, causing the hair shaft to be pushed upward. While hair is not growing during this phase, the length of the terminal fibers increase when the follicle pushes them upward.[6]
Telogen phase
During the telogen, or resting, phase the hair and follicle remain dormant anywhere from 1–4 months.[6] Ten to fifteen percent of the hairs on one's head are in this phase of growth in any given time.[5] The anagen phase begins again once the telogen phase is complete. The preceding hair strand is pushed up and out by the new, growing strand. This causes a normal hair loss commonly known as shedding.
Growth inhibitors and disorders
Chemotherapy
Chemotherapy involves being administered drugs to attack the fast-growing cancer cells. Hair follicle cells also grow and divide quickly; consequently, the chemotherapy drugs usually inhibit hair growth.[8] The dose and type of medicine determine how severe a person experiences hair loss, but once the chemotherapy has ended, one can begin to experience new hair growth after three to 10 months.[8]
Alopecia is a hair loss disease that can occur in anyone at any stage of life. Specifically Alopecia areata is an autoimmune disease that causes hair to spontaneously fall out. It is mainly characterized by bald patches on the scalp or other parts of the body, and can ultimately cause baldness across the entire body.[9] This disease interferes with the hair growth cycle by causing a follicle to prematurely leave the anagen, or active growth, phase and enter the resting, or telogen phase. The hair growth in the affected follicles is lessened or stopped completely.
Traction alopecia is caused by adding too much strain on the hair on one's head. Tight ponytails and other styles that require added tension to the hair are often what cause this disease. It can also occur on the face in areas where the hair is often styled.[10] Plucking or waxing one's eyebrows frequently, for example, can yield suppressed hair growth in the area.
On the scalp, the hair is usually known to be lost around the hair line, leaving the densest amount of hair at the crown. Small vellous hair will often replace the hair that is lost.[10]
Myths
There are many myths about hair growth and healthy hair that have been around for years. While some of these myths have been proven to be true, many of them, although accepted through popular belief, are false.
Cutting/trimming hair helps it to grow faster or thicker
This is false. Seeing as cutting and trimming happens at the ends of the hair, which are "dead," there is no way for the "living" portion under the scalp to sense when hair has been cut. This myth probably came about because cutting and trimming the hair gets rid of split ends which result from damage that cause breakage of the hair shaft. When the hair is trimmed regularly, the number of split ends is reduced, allowing the hair to grow to longer lengths without breaking. This gives off the effect that hair is growing faster, when in fact it is simply breaking off less often.
Hair will always remain the same texture
Hair will not always remain the same texture. A good example of this is seen in the hair texture of an adult compared to that of his or her texture as a child. In many cases, the hair of an infant will be softer compared to his or her hair at a later stage in life. Pregnancy and medications can also alter one's hair texture [11][medical citation needed].
Virgin root hair should be treated differently than the hair at the ends
Hair at the root is different compared to the hair that is farther away from the scalp, and therefore should be treated differently. The hair at the root is stronger than the hair that has grown out, especially if the hair has previously been treated with chemicals such as perms, relaxers, or hair dyes. Many treatments are specially made for natural hair or processed hair because of the differences in strength. Natural hair can take to harsher chemicals and heat better than processed hair.
Washing hair every day tends to dry it out/Hair should always be washed every day
Both of these statements are false. Because texture and type of hair varies from person to person, an individual must learn how his or her hair reacts to certain products, like shampoos and moisturizers, and how often his or her hair is to be washed. Usually, people with finer, straighter hair will wash their hair more often to avoid excessive oil build-up, while thicker, curlier heads of hair are washed less often to avoid a dry scalp. Curly hair prevents essential oils from the scalp to reach parts of the hair strand closer to the roots, resulting in overall dryness, often characterized by lack of luster, loss of original curl pattern, and breakage. Those people with thicker, curlier manes often also require store-bought moisturizers to compensate for their lack of natural moisture.
Brushing thinning hair makes it fall out
This is false. Regular daily brushing will only help to remove hair that is ready to be removed.[11][medical citation needed]. However, excessive brushing should be avoided because it can irritate the scalp and weaken the hair, yielding damage and breakage.
Citations
- ^ a b [1]
- ^ "Hair Growth Guidelines to Promote Hair Growth". Stoppinghairlossnow.com. Retrieved 21 April 2010.
- ^ "The Correlation Of Exercise & Healthy Hair - Help you body and hair become more healthy". Healthyhairplus.com. Retrieved 21 April 2010.
- ^ [2]
- ^ a b c (Hair Structure and Hair Life Cycle)
- ^ a b c d "How Does Hair Grow?" Web. 9 February 2010.
- ^ [3]
- ^ a b "Chemotherapy and hair loss: What to expect during treatment". MayoClinic.com. Retrieved 21 April 2010.
- ^ (Alopecia Areata - Alopecia Areata Overview)
- ^ a b (Traction Alopecia)
- ^ a b Karen Marie Shelton - Copyright 2002 - All Rights Reserved. "25 Hair Myths: Fact Or Fiction?". Hairboutique.com. Retrieved 21 April 2010.
{{cite web}}
: CS1 maint: numeric names: authors list (link)
References
- McElwee, Kevin. "Hair biology - hair fiber composition." Found on Hair loss and hair growth information. Kevin J. McElwee, editor. Accessed 23 January 2010.
- Kevin McElwee is a doctor who is currently studying alopecia, which is a condition associated with hair loss (blog.americanhairloss.org)
- "Your Hair." KidsHealth - the Web's most visited site about children's health. Web. 23 January 2010. <http://kidshealth.org/kid/htbw/hair.html>.
- This is a URAC (Utilization Review Accreditation Commission) accredited website. The commission deals with health care accreditation & certification.
- Conger, Cristen. "HowStuffWorks "Why do humans have body hair?"" Howstuffworks "Health" Web. 23 January 2010. <http://health.howstuffworks.com/human-body-hair.htm>.
- Cristen Conger is a journalist who studied at the University of Georgia. How Stuff Works is a site that is affiliated with Discovery Communications, founded by North Carolina University Professor Marshall Brain.
- Dr. Oz on: Healthy Hair. Perf. Mehmet Cengiz Oz. How Stuff Works. Web. 23 January 2010. <http://videos.howstuffworks.com/sharecare/31184-dr-oz-on-healthy-hair-video.htm>.
- Dr. Oz has an MD and MBA, and is the professor of cardiac surgery at Columbia University.
- Blume-Peytavi, Ulrike. Hair Growth and Disorders. Illustrated ed. Springer, 2008. Google books. Web. 23 January 2010.
- Author is a doctor with an MD and is a practicing dermatologist.
- "Epithelium -Wikipedia, the free encyclopedia." Wikipedia, the free encyclopedia. Web. 9 February 2010. <http://en.wikipedia.org/wiki/Epithelium>.
- I checked the information here against other sources to verify the information was correct.
- "Figure 1-3. Principal parts of a hair." Repair and Maintenance Manuals - Integrated Publishing. Web. 9 February 2010. <http://www.tpub.com/content/armymedical/MD0575/MD05750011.htm>.
- I checked the information here to verify that it was correct.
- "How Does Hair Grow?" Hair loss help - Hair Transplant Doctors - Hair loss product information. Web. 9 February 2010. <http://www.hairlosshelp.com/hair_loss_research/hair.cfm>.
- The website claims to review the information they post to ensure that it is reputable. I check the information against other sites to ensure it was correct.
- "Inside the Hair." Cartoon. Pantogar. Web. 9 February 2010. <http://www.pantogar.com/en/inside_the_hair.php>.
- Pantogar is a line of hair products that have gone through many clinical studies by experts.
- "What is hair?" Men's Health - Health and Fitness Information for Men. Web. 9 February 2010. <http://menshealth.about.com/cs/hairhairloss/f/baldness.htm>.
- The information on this page can be found on many other sites making it valid.
- "Hair Removal." KidsHealth - the Web's most visited site about children's health. Web. 9 February 2010. <http://kidshealth.org/teen/your_body/skin_stuff/hair_removal.html>.
- This is a URAC (Utilization Review Accreditation Commission) accredited website. The commission deals with health care accreditation & certification.
- "Fig. 19.51 Intermediate Filament Structure." Cartoon. IUPUI Department of Biology. Web. 10 February 2010. <http://bioweb.wku.edu/courses/biol22000/31IntermediaryFilaments/Fig.html>.
- This website is that of an esteemed university.
- "Hair Structure and Hair Life Cycle." Alopecia Information and Resources at Follicle.com. Web. 17 February 2010. <http://www.follicle.com/hair-structure-life-cycle.html>.
- This site has a page dedicated to links used for additional information used to supplement what is there.
- "Topic 2: The Layers of the Hair." Welcome to the Texas Collaborative website. Web. 17 February 2010. <http://www.texascollaborative.org/hildasustaita/module%20files/topic2.htm>.
- The information on this site can be verified in other sources.
- "Hair biology - hair fiber." Hair loss and hair growth information. Web. 18 February 2010. <http://www.keratin.com/aa/aa024.shtml#04>.
- The information is compatible with that of other sources.
- "Anagen Phase." Dermatology - Guide to Skin Conditions and Skin Care. Web. 22 February 2010. <http://dermatology.about.com/od/hairanatomy/l/bldefanagen.htm>.
- The information on this website is also found in other sources.
- "Hair follicle - Wikipedia, the free encyclopedia." Wikipedia, the free encyclopedia. Web. 23 February 2010. <http://en.wikipedia.org/wiki/Hair_follicle>.
- The information found here can be found in other sources.
- "Thumbprints - The Human Eyelash." Images Of Nature. Web. 3 March 2010. <http://ion.asu.edu/liv41_eyelash/liv41_thumb.htm>.
- This site is a ".edu" site, which is one of the most reputable types of sources.
- "Sound Medicine: Why Do We Have Eyebrows?" Sound Medicine. 29 March 2003. Web. 3 March 2010. <http://soundmedicine.iu.edu/segment/324/redirect?seg=324>.
- This site is a ".edu" site and the information here can be found in other sources.
- Alaiti, Samer. "Hair Growth: EMedicine Otolaryngology and Facial Plastic Surgery." EMedicine - Medical Reference. 14 July 2009. Web. 8 March 2010. <http://emedicine.medscape.com/article/837994-overview>.
- Samer Alaiti is a doctor and the Clinical Associate Professor in the Department of Dermatology at the University of Southern California.
- "Puberty." Massachusetts General Hospital Home Page. Web. 11 March 2010. <http://www.mgh.harvard.edu/children/adolescenthealth/articles/aa_puberty.aspx>.
- The article is associated with Harvard Medical School.
- Shelton, Karen M. "25 Hair Myths: Fact Or Fiction?" Hair Boutique. 4 June 2002. Web. 23 March 2010. <http://www.hairboutique.com/tips/tip1135.htm>.
- "Getting Rid Of Unwanted Hair." Women Fitness - A Complete Online Guide To Achieve Healthy Weight Loss and Optimum Fitness. Fitness Women, Women's Fitness, Women Health, Woman Health, Health, Womensfitness. Web. 8 April 2010. <http://www.womenfitness.net/beauty/hair/gettingrid_of_unwanted_hair.htm>.
- McElwee, Kevin. "Alopecia Areata - Alopecia Areata Overview." Hair Loss and Hair Growth Information. Web. 16 April 2010. <http://www.keratin.com/ad/ad010.shtml>.
- "Traction Alopecia: EMedicine Dermatology." EMedicine - Medical Reference. Web. 16 April 2010. <http://emedicine.medscape.com/article/1073559-overview>.
- "Chemotherapy and Hair Loss: What to Expect during Treatment - MayoClinic.com." Mayo Clinic Medical Information and Tools for Healthy Living - MayoClinic.com. Web. 17 April 2010. <http://www.mayoclinic.com/health/hair-loss/CA00037>.
- "Foods That Promote Hair Growth." Quick Care's Self-Care Advisory. Web. 17 April 2010. <http://www.quickcare.org/skin/foods-that-promote-hair-growth.html>.
- Smith, Karl. "Hair Growth Guidelines to Promote Hair Growth." Effective Hair Growth Program. Web. 18 April 2010. <http://www.stoppinghairlossnow.com/guidelines.html>.
- "The Correlation Of Exercise & Healthy Hair - Help You Body and Hair Become More Healthy." Health Hair Plus. Web. 18 April 2010. <http://www.healthyhairplus.com/The-Correlation-Of-Exercise-Healthy-Hair-s/3962.htm>.
- "Damaged Hair Care." TargetWoman - Women Portal. Web. 19 April 2010. <http://www.targetwoman.com/articles/damaged-hair-care.html>.
- "Conditioner Washing: The New Way to Shampoo." Long Healthy Hair Advisor, Grow and Maintain a Beautiful Mane. Web. 20 April 2010. <http://www.long-healthy-hair-advisor.com/conditioner-washing.html>.
- Bubenik, George A. "Why Do Humans Get "goosebumps" When They Are Cold, or under Other Circumstances?: Scientific American." Science News, Articles and Information | Scientific American. Web. 27 April 2010. <http://www.scientificamerican.com/article.cfm?id=why-do-humans-get-goosebu>.