By week 22, a developing fetus has all of its hair follicles formed. At this stage of life there are about 5 million hair follicles on the body. There are a total of one million on the head, with one hundred thousand of those follicles residing on the scalp. This is the largest number of hair follicles a human will ever have, since we do not generate new hair follicles anytime during the course of our lives.
Most people will notice that the density of scalp hair is reduced as they grow from childhood to adulthood. The reason: Our scalps expand as we grow.
Hair Structure and Hair Life Cycle
Hair is composed of strong structural protein called keratin. This is the same kind of protein that makes up the nails and the outer layer of skin.
Each strand of hair consists of three layers: (hair follicles)
• An innermost layer or medulla which is only present in large thick hairs.
• The middle layer known as the cortex. The cortex provides strength and both the color and the texture of hair.
• The outermost layer is known as the cuticle. The cuticle is thin and colorless and serves as a protector of the cortex.
The innermost region, the medulla, is not always present and is an open, unstructured region. The highly structural and organized cortex, or middle layer of the hair, is the primary source of mechanical strength and water uptake.
The cortex contains melanin, which colors the fiber based on the number, distribution and types of melanin granules. The shape of the follicle determines the shape of the cortex, and the shape of the fiber is related to how straight or curly the hair is. People with straight hair have round hair fibers. Oval and other shaped fibers are generally more wavy or curly.
The cuticle is the outer covering. Its complex structure slides as the hair swells and is covered with a single molecular layer of lipid that makes the hair repel water.
Structure of the hair root
Below the surface of the skin is the hair root, which is enclosed within a hair follicle. At the base of the hair follicle is the dermal papilla. The dermal papilla is feed by the bloodstream which carries nourishment to produce new hair. The dermal papilla is a structure very important to hairgrowth because it contains receptors for hormones regulate hairgrowth.
Hair growth begins inside the hair follicle. The only “living” portion of the hair is found in the follicle. The hair that is visible is the hair shaft, which exhibits no biochemical activity and is considered “dead”. The base of a hair’s root (the “bulb”) contains the cells that produce the hair shaft. Other structures of the hair follicle include the oil producing sebaceous gland which lubricates the hair and the arrector pili muscles, which are responsible for causing hairs to stand up. In humans with little body hair, the effect results in goose bumps.
All natural hair colors are the result of two types of hair pigments. Both of these pigments are melanin types, produced inside the hair follicle and packed into granules found in the fibers. Eumelanin is the dominant pigment in brown hair, and black hair, while pheomelanin is dominant in red hair. Blond hair is the result of having little pigmentation in the hair strand. Gray hair occurs when melanin production decreases or stops.
The Hair Growth Cycle
It’s very important to understand the hair growth cycle in order to recognize and understand many of the problems you can encounter with your hair.
The hair growth cycle consists of three distinct stages:
Your hair grows around half an inch a month, and faster in the summer than in winter. The growth phase, or anagen phase, lasts an average of 3-5 years, so a full-length hair averages 18 to 30 inches. The anagen phase is generally longer in Asians, and can last as much as 7 years with hair being able to grow to 1 metre.
At the end of the anagen phase, your hair enters the catagen phase. A short transitional phase that lasts approximately 10 days.
Lastly, your hair enters the telogen phase, a resting phase when your hair is released and falls out. The follicle then remains inactive for 3 months and the whole process is repeated. Each hair follicle is independent and goes through the growth cycle at different times, otherwise all your hair would fall out at once. Instead, you only shed a certain number of hairs a day – up to 80 hairs on a healthy head of hair.
Hair loss, hair thinning and problems with hair growth occur when your growth cycle is disrupted. This can be triggered by conditions such as metabolic imbalances, illness or improper nutrition.
See also: “Healthy“
Texture And Type
The texture of your hair is determined by the size and shape of the hair follicle, which is a genetic trait controlled by hormones and related to age and racial characteristics.
Whether hair is curly, wavy or straight depends on two things: its shape as it grows out of the follicle, and the distribution of keratin-producing cells at the roots.
When viewed in cross-section, straight hair tends to be round, wavy hair tends to be oval, and curly hair kidney shaped.
Straight hair is formed by roots that produce the same number of keratin cells all around the follicle.
In wavy and curly hair, the production of keratin cells is uneven, so that at any given time there are more cells on one side of the oval equally shaped follicle than on the other. Furthermore, the production of excess cells alternates between the sides. This causes the developing hair to grow first in one direction and then in the other. The result is wavy or curly hair.
The natural color of the hair also affects the texture. Natural blondes have finer hair than brunettes, while redheads have the thickest hair.
Consistency of the hair
The consistency of hair can almost always be grouped into three categories: fine, medium, and coarse.
This trait is determined by the hair follicle volume and the condition of the strand.
Fine hair has a small circumference in relation to medium and coarse strands; coarse hair having the largest circumference. Coarse hair has a more open cuticle than thin or medium hair causing it to be the most porous.
Fine hair can be strong or weak; however, because of its texture, all fine hair has the same characteristic • it lacks volume.
About 15% of all women have fine hair. Fine hair has a diameter of 50 microns. Fine hair reflects light the best. When it is healthy, fine hair will often have a natural shine. Blondes have fine hair most often, since blonde hair is the thinnest.
Fine hair is: soft, shine, limp, flyaway, lifeless and flat.
Fine hair is much easier to damage than medium or coarse hair. The biggest problem with fine hair is to gain volume and get hair to hold a style.
To gain volume, color and heat style your hair and it will hold a style easier. Use volumizing products and styling gels and mousses. Use a gentle shampoo.
It is also important to use a lightweight conditioner! Put conditioners onto the lengths and ends of your hair rather than the roots.
A short blunt cut will create the illusion of more hair. Avoid layers and long hair.
The general rule for fine hair is that the shorter it is, the lighter it is and therefore the less limp and flat it is. Streaks are a good idea for fine hair, because they add volume to the hair.
As the name suggests, medium hair is neither too thick nor too thin, and is strong and elastic.
Most people have medium hair. Medium hair is not too thick, not too thin, and has a diameter between 60-90 microns.
Medium hair has lots of body and usually holds either a blow-dry shape or any type of hairstyle very well. It has the most styling flexibility of the three hair types.
Medium hair is:
• Softer than coarse hair.
• More voluminous than fine hair.
• More manageable than fine hair.
• Medium hair is regularly considered as normal hair.
Thick and coarse hair is abundant and heavy, with a tendency to grow outwards from the scalp as well as downwards. It often lacks elasticity and is frizzy.
Coarse hair has a diameter of 100 microns and above.
Coarse hair is:
Coarse hair is often dry. It is hard to process, and can be very resistant to hair coloring, perming, and straightening. It needs conditioning to keep it under control.
Wear it long so the weight of the hair drags it down. Get a layered cut. Stay away from a blunt cut.
There are various systems that people use to classify their curl patterns. Being knowledgeable of an individual’s hair type is a good start to knowing how to take care of one’s hair.
There are multiple hair typing systems:
• The Andre Walker Hair Typing System
• LOIS System
• FIA’s Hair Typing System.
The system created by Andre Walker is substantially more popular well-known and communicated than the other hair typing systems.
Andre Walker system
Type 1 Straight Hair:
Generally speaking Type 1 hair is straight; however Andre categorizes this hair type into three very specific segments: Type 1A, Type 1B, and Type 1C.
• 1- Type 1A hair is described as fine, very thin and soft with a noticeable shine.
• 2- Type 1B hair is medium-textured and has more body than Type 1A hair.
• 3- Type 1C hair is the most resistant to curly styling and relatively coarse compared to other Type 1 hair types.
Type 2 Wavy Hair:
A Type 2 is wavy hair that usually isn’t overly oily or very dry. The thought is that Type 2 hair falls right in the middle of Type 1 and Type 3.
• 1- Type 2A hair is fine and thin. It is relatively easy to handle from a styling perspective because it can easily be straightened or curled.
• 2- Type 2B hair characteristically has waves that tend to adhere to the shape of your head.
• 3- Type 2C hair will frizz easily and it is fairly coarse.
Type 3 Curly Hair:
Curly hair textures have a definite “S” shaped curl pattern. Since the cuticle doesn’t lay flat, you will noticed that curly hair isn’t nearly as shiny as Type 1 (straight hair) or Type 2 (wavy hair) hair types.
• 1- Type 3A hair is very shinny and loose.
• 2- Type 3B hair has a medium amount curls, ranging from bouncy ringlets (spiral like curls of hair) to tight corkscrews (spiral-shaped corkscrew curls).
Type 4 Kinky Hair:
A Type 4 is “kinky” or more appropriately full of tight coils (tightly curled hair). Typically, Type 4 hair is also extremely wiry and fragile. Often times, it appears to be coarse, however it is really very fine, with several thin hair strands densely packed together. Note that type 4 hair is one the most common hair types found in black hair (african american hair).
• Type 4A hair is full of tight coils. It has a “S” pattern when stretched, much like Type 3 curly hair.
• Type 4B hair has a less defined pattern of curls and looks more like a “Z” as the hair bends with very sharp angles.
• Type 4C as 4a and 4b but with almost no defined curl pattern.
Hair type: Normal, Dry or Oily
Hair type is determined by the hair’s natural condition, that is the amount of sebum the body produces. Treatments such as perming, coloring and hair styling will also have an effect on hair type. Natural hair types and those produced by applying treatments are described here.
• 1- It can look dull, feels dry and tangles easily.
• 2- It is difficult to brush, particularly when it is wet.
• 3- It is often quite thick at the roots but thinner, and sometimes split, at the ends.
• Excessive shampooing
• over-use of heat-styling equipment
• misuse of color or perms
• damage from the sun, or harsh weather conditions.
Each of these factors depletes the moisture content of hair, so that it loses its elasticity, bounce and suppleness.
Dryness can also be the result of a sebum deficiency on the hair’s surface, caused by a decrease in or absence of sebaceous gland secretions.
Solutions: Use a nourishing shampoo and an intensive conditioner. Dry hair naturally.
It is neither oily nor dry, has not been permed or colored, hold its style and looks good most of the time.
Normal hair is suited to the daily use of two-in-one conditioning shampoos. These are formulated to provide a two-stage process in one application. When the product is lathered into wet hair the shampoo removes dirt, grease and styling products. At this stage the conditioner remains in the lather. As the hair is rinsed with more water, the grease and dirt are washed away, and the micro-fine conditioning droplets are released onto the hair, leaving it shiny and easy to comb.
It looks lank and greasy and needs frequent washing to look good.
Overproduction of sebum as a result of hormone disturbances, stress, hot and humid atmosphere, excessive brushing, or constantly running hands through the hair, perspiration, or a diet rich in saturated fat.
The hair becomes oily, sticky and unmanageable in just a few days, or sometimes within hours.
Use a gentle, non-aggressive shampoo that also gives the hair volume.
A light perm will lift the hair at the roots and limit the dispersal of sebum.
Rethink your diet; cut out as many dairy fats and greasy foods as you can.
Try to eat plenty of fresh food, and drink six to eight glasses of water everyday.
It is oily at the roots but dry and sometimes split at the ends.
Chemical treatments, using detergent based shampoos too frequently, overexposure to sunlight, and over-use of heat-styling equipment. Such repeated abuse often provokes a reaction in sebum secretion at the roots and a partial alteration in the scales, which can no longer fulfil their protective role. The hair ends therefore become dry.
Use products that have only a gentle action on the hair. Excessive use of formulations for oily hair and those for dry hair may contribute to the problem. Ideally, use a product specilly designed for combination hair. If this is not possible try using a shampoo for oily hair and finish by applying a conditioner from the middle lengths to the ends of the hair only.