Biology Of The Hair
Understanding how to keep your hair healthy requires a bit of understanding of hair biology.
Hair consists basically of two parts, the outer portion which is the shaft; and the inner part which is the root, also known as the follicle. The hair we see on top of the scalp comes in many different colors and degrees of curliness. On the molecular level, the more disulfide bonds you have in your hair shafts, the curlier your hair is. On the microscopic level, when a hair is cut cross-sectional, a straight hair will have a round shape. The less round the cross section is, or if the cross section is flat or elliptical, the more curl is in the hair.
All Hair Follicles Are Present Before Birth
During gestation, by the end of the sixth month, the fetus has all the hair follicles it is ever going to have. At a total of about five million hair follicles, there will never be another time when the body has as many follicles. The older the body grows the faster loss of follicles increases.
The External Hair
The shaft of the hair is a structure of three layers of keratin. Keratin is hardened, lifeless protein. The shaft of keratin has layers that, from the outside inward are called the cuticle, the cortex and the medulla. This entire structure is surrounded by the internal and external root sheaths which continue all the way around the follicle. The external root sheath is in continuation from the dermis while the internal root sheath will appear at about the area where the sebaceous gland duct connects with the hair follicle. The cortex is the structure that holds the melanocytes that gives your hair its color.
Oil Glides Better On Straight Hair
Sebaceous glands produce the oil that gives hair its softness. It also permits the hair being twisted and bent into different hairstyles without breakage. It is easier for sebum to glide along the shafts of straight hair than the tortuous course of curly hair. This is the primary reason why straight hair is often oilier than curly hair.
Goosebumps And Your Hair
A little deeper to the area where the sebaceous gland attaches to the hair shaft is the attachment of the tiny arrector pili muscles. These are the little muscles that make your hair stand up when you are cold or when you have a sudden flash of fear. The contraction of the muscles produces the puckering of “gooseflesh.”
Follicles Are In The Dermis
The follicle is the deepest part of the hair. It forms the root from which the hair grows. It is covered by the outer root sheath. The follicle and the outer root sheath are covered by a connective tissue sheath. The bottom of the follicle divides into two claw-like projections. Through the opening between these projections forms a papilla which is used to surround tiny blood vessels that enter to bring nourishment to the hair shaft. One of the blood vessels is an arteriole that brings freshly oxygenated blood to the hair shaft. The arterioles connect with the venules which carry away deoxygenated blood and other debris in the blood stream.
Hair And Chemo
Hair follicle cells divide very quickly. This is part of the reason why hair falls out when patients have to undergo chemo therapy.
How to keep hair healthy
There are three primary objectives and tactics for getting and improving the health of your hair.
- First, is to maintain sufficient blood flow to the scalp. This ensures a balance of nutrients are delivered to the developing follicle and, more basically, the lifeline of follicle development is maintained. This can be accomplished through a balanced diet rich in leafy vegetables or through use of hair growth stimulants (follicle stimulators).
- Second, after adequate blood flow is stabilized, making sure proper and balanced nutrients, vitamins, and minerals are allowed to be absorbed into the papilla and scalp tissue. For healthy hair, certain hair products can be beneficial. Such as vitamins and supplements that enhance, Biotin, Niacin and the B-complex family. All of these nutrients, plus amino acids, help healthy growth in all stages of the hair's growth and often produce thicker, faster growing follicles with a healthy shine.
- Third, avoid damage. While this may sound simple, damage can come from a lot of different sources. Heat from flat irons, curling irons, and dryers can dehydrate and steal moisture leading to frizz, excess static cling, hair breakage, and pre-mature snapping and tearing. Similarly, chemical treatments to add color, bleaching and even lowlights and highlights can strip oils (sebum), nutrients and moisture. Generally, the more treatments you have done, the less healthy hair will become.
When considering proper hair care, it is helpful to understand hair types and fundamental functions of the hair as it progresses through its growth cycle as well as the role of hair products. To respond to hair loss or thinning hair, a hair loss analysis may be necessary to identify causes of hair problems. Understanding the hair’s cycle and biology helps in developing solutions for healthy growing hair.
Human hair falls into three basic groupings: lanugo, vellus, and terminal hairs. The first hairs to appear in the follicle are lanugo which are fine and without the medulla (comprised of loosely, hardened cells at the center of the hair – not uncommon for the center to not be present, especially in finer hairs). They have little or no melanin (color) and are generally colorless. Lanugo hairs vary in length, but are short and rarely exceed several centimeters. They are formed before birth.
Vellus hairs resemble lanugo hairs, rarely exceeding several centimeters and can best be characterized as the smallest, light facial hairs.
The largest of the hairs are terminal hairs and are the most common and noticeable of hair types. Terminal hairs often lack a medulla, and terminal hairs on the scalp have been known to exceed 39 inches in length. Terminal body hairs rarely exceed 1 inch.
Patterns of hair on the body are directly related to the three types of hairs. Lanugo hairs are replaced by vellus hairs as we mature and grow except for hairs on the brows, scalp and face where they are replaced by terminal hairs which are coarse and grow longer. Loss of terminal hairs can begin at age 40. Hair patterns are dynamic and are constantly changing.
Follicles are distributed over the entire surface of the skin except for palms and soles. Hairs develop out of the follicle at an angle to the skin’s surface, and regardless of the hair’s size or length, all hairs are “born” in the hair bulb, a mass of cells at the base of the follicle.
Hair progresses through a growth cycle made up of three stages: The Anagen is the growth stage and generally lasts up to about four years. This stage is followed by the Catagen phase, is transitional and can last up to three months. The final, or resting stage, is the Telogen stage during which a new hair bulb is developed. At any point, hairs – in particular those of the scalp - can be moving through any of these three cycles.hair biology and growth cycle
Regarding hair loss, thinning or slow growing hair, it is necessary to identify stages of the growth cycle along with understanding which environmental or physiological factors may be influencing hair growth
Hair is susceptible to hormonal changes, excessive sebum (oil) production, stress, nutrition, medication, pregnancy or childbirth, and to environmental factors such as product build-up, chemical treatments, sun and photo-damage, and styling.
Much hair loss is temporary and can be addressed by hair products formulated to increase blood circulation, block DHT enzymes, or to deep clean the scalp. Life-style changes – reduced stress, improved nutrition, and adequate exercise and water consumption – can have a significant effect on hair loss and thinning.
Many of these slow growing issues can be addressed with a hair growth shampoo with Trichogen. Additionally, natural products have been shown to work as effectively as synthetics for maintaining and encouraging normalized biology of the cuticle, root and shaft. An herb shampoo that either helps growth, body or that acts to deep clean and clarify can help avoid stripping natural nutrients and oils necessary for follicle pore and scalp health.