1.6.
3.6.
3.7.
3.8.
4.4.
4.5.
4.6.
5.3.
5.5.
5.5.1.
5.5.2.
5.5.3.
5.6.
6.1.
6.2.
6.3.
6.7.
6.9.
7.4.
6.9.1.
6.9.2.
6.9.3.
8.1.
7.4.2.
1.6. TYPES OF HAIR AND THEIR PROPERTIES
1.6.1. Classification according to hair type
Hair classified according to hair type is divided into:
y hair follicle – occurring on a large surface of the body;
y bristly hair – located in the external auditory canal, in the nasal vestibule, as well as eyebrows and eyelashes;
y long hair – occurring on the scalp, beard and armpits.
1.6.2. Classification according to hair type
Hair is also classified by type:
y terminal hair – also known as definitive hair. Found on the scalp, as facial hair, or in the armpits, also called long hair, with the strongest pigmentation, located of the scalp;
y transitional hair – located on the forearms and lower limbs; the growth cycle is estimated to be approximately 12 months;
y vellus hair – located on the face, trunk and arms; the hair follicle growth cycle is estimated at 6 months.
1.6.3. Andre Walker’s classification
Hair type can also be determined based on the type of curl and thickness, using Andre Walker’s classification:
1. Straight hair:
1A. Straight and thin hair – low porosity hair, does not tend to frizz, thin and delicate hair easily becomes electrified, hair ends may split.
1B. Straight and medium thickness hair – low porosity hair, characterized by medium thickness, not susceptible to styling.
1C. Straight and thick hair – low porosity hair, with a tendency to become oily at the roots, is characterized by much greater volume than hair types 1A and 1B.
2. Wavy hair:
2A. Delicate, loose waves – low/medium porosity hair, adherent to the scalp, sensitive to inappropriate styling/care.
Anatomy and physiology of skin and hair
Figure 1.7.
Andre Walker’s classification of hair types (straight, slightly wavy, curly, and tightly curly) with subgroups marked with letters a to c (explanations in text)
Source: Aleksandra Nekrasova/Dreamstime
2B. Defined waves – medium/high porosity hair, reflected from the roots, characterized by a defined, emphasized curl with a thicker hair diameter than type 2A.
2C. Wide waves – medium/high porosity hair, characterized by large volume, has a much more durable curl than type 2B, tends to lose moisture quickly.
3. Curly hair:
3A. Loose curls – high porosity hair, separated from the roots, susceptible to styling.
3B. Defined curls – high porosity hair, with a lot of volume, reflected from the roots, very difficult to style.
4. Knot hair:
4A. Tight curl – high porosity hair, matte, dense, with a lot of volume, difficult to style, with a spiral form of curl.
4B. Zigzag form – high porosity hair, with a very tight curl in the form of zigzags, raised from the roots, dense, much thicker than type 4A, matte.
1.6. Types of hair and their properties
1.6.4. Classification according to the structure of the hair
Hair classification by structure:
1. Normal hair – healthy hair, with appropriate elasticity, proper level of moisture and shine.
2. Oily hair at the roots (oily scalp) – excessive activity of the sebaceous glands of the scalp, disturbed hydrolipid balance of the scalp, excess sebum transferred to the hair shaft.
3. Dry hair – hair without a fatty coating, the reason may be improper hair care/ styling, poor diet and supplementation, hormonal disorders.
4. Damaged hair – characterized by excessive roughness and brittleness, damage may be caused by external as well as genetic factors, such as disorders of the corneal protective barrier.
1.6.5. Classification by ethnicity
Hair classification by ethnicity:
1. Slavic hair – hair with a strong structure, durable, in natural shades (from light blonde to medium brown).
2. Caucasian hair – durable hair with various structures (straight, wavy, curly).
3. Asian hair – thick hair, with a straight structure, usually in a dark shade.
4. Indian hair – dense, thick hair, but with a delicate structure, susceptible to styling, with a tendency to dry out.
5. African-American hair – durable hair, usually with a tight curl, not easy to style.
1.7. HAIR SHAFT – DEFECTS OF HAIR SHAFT
The hair shaft is composed of an outer layer – the protective sheath and the inner cortex. The normal structure of the hair shaft may be disturbed by external or genetic factors, which may lead to changes in the physical properties of the hair. The main structural components of the hair shaft are keratinocytes associated with the intercellular matrix protein. As a result of damage, in certain anomalies, the hair cortex may become exposed, which makes it much more susceptible to external damage and possible breakage. Clinical symptoms also include changes in the external texture of the hair and brittleness of the hair shaft.
Anatomy and physiology of skin and hair
ENTRY
Trikhos in Greek means hair, from which comes the name trichology, i.e. the study of hair. Trichology is a field of medicine that covers the diagnosis of scalp and hair diseases, as well as the treatment and care process.
In order to properly diagnose, interpret, and analyze scalp disease, it is essential to understand the biology of the skin and its appendages. The structure of the hair shaft may initially seem quite simple, but in fact it is a complex part of the anatomy. Proper histopathological evaluation of scalp dermatoses should be based on an understanding of the structure of the basic unit, hair follicles and all associated structures. The book covers the full spectrum of trichopathology, essential for proper understanding trichoscopic image of the patient, from the anatomy and physiology of the scalp and hair, to the classification of scalp diseases, facilitating the proper interpretation of the patient’s clinical data.
The following chapters include clinical features, pathogenesis, as well as medical treatment in relation to individual dermatoses, laboratory diagnostics, and also histological features with clinical description, trichoscopic features, and classification of hair types and types of hair damage. They allow proper understanding of the pathophysiology and clinical presentations, as well as the therapeutic and surgical therapies used. However, it is necessary to emphasize the importance of proper care of the scalp and hair in the field of cosmetological trichology, which is necessary to achieve results acceptable to patients.
The aim of the publication was also to describe comprehensively diseases of the scalp, in medical, cosmetological and surgical terms. Without following previous models, the treatment text as well as the characterization of individual scalp disorders specifically addresses their molecular basis in a complex manner.
Subsequently, such important issues as the basics of endocrinology, dietetics and the organization of work in a trichology office were discussed. The book covers the full range of knowledge necessary to work with a trichological patient.
The range of recipients of the publication is very wide. Both students and practicing trichologists, dermatologists and cosmetologists involved in the treatment of patients with excessive hair loss will probably find the presented content helpful and practical.
PhD Claudia Musiał
y “Woolly” hair – it is a congenital, rare anomaly of hair structure. It is characterized by severe curling, which may occur on the entire scalp or locally. There is also a shortened anagen phase. Changes can be observed during trichoscopic examination. Axial rotation is also noted in the anomaly. The first changes appear shortly after birth or until the first 18 months of life. An anomaly maybe be associated with other genetic syndromes such as keratosis pilaris (atrophicans faciei), cardio-facio-cutaneous syndrome, palmoplantar keratosis, Carvajal syndrome and Noonan syndrome.
y Uncombable hair syndrome (pili trianguli et canaliculi) – triangular and tubular hair.
2. Damage to the hair shaft with increased hair brittleness – congenital defects:
y Nodal hair cleft (trichorrhexis nodosa) – a congenital or genetic anomaly, but it may also be an acquired defect. It is characterized by light nodes, frayed hair cortex and excessive brittleness of the hair shaft. Importantly, the cortical fiber breaks. The anomaly occurs in diseases such as chronic lichen simplex, atopic dermatitis, contact dermatitis, numb skin dermatitis, Menkes syndrome, argininosuccinic acidosis and citrulinemia.
y Curly hair (pili torti) – an anomaly characterized by a significantly increased curl of the hair at an angle of 180° caused by irregularities in the inner sheath of the hair root. The hair shaft is brittle, weak or excessively brittle. In addition, the hair growth cycle is significantly shortened. Pili torti may also appear in the eyelashes and eyebrows. Research results indicate that the damage may be closely related to the presence of reactive oxygen species and mitochondrial dysfunction. The anomaly often occurs with others congenital defects. One of them is a recessive autosomal disease – Björnstad syndrome – caused by the BCS1L mutation on chromosome 2q34–36.
y Beady hair (monilethrix) – a genetically determined anomaly. Mutations in the KRT81, KRT83 and KRT86 genes, related to the coding of type II keratin Hb1, Hb3 and Hb6, are responsible for the damage. It is characterized by excessive brittleness, dryness and brittleness of the hair shaft, often leading to complete baldness. Streptococcal lesions may cover the entire body area – the scalp, pubic hair, eyebrows and eyelashes. At the same time, patients are often diagnosed with keratosis pilaris. Attempts are being made to treat the anomalies with N-acetylcysteine.
y Bamboo hair (trichorrhexis invaginata) – an anomaly characterized by unevenly distributed “bumps” along the length of the hair shaft, visible in the trichoscopic image. Bamboo hairs often coexist with other entities such as ichthyosis linearis circumflexa. The anomaly may occur in the crown area of the scalp, eyebrows and eyelashes. Typically, the anomaly is a feature of a hereditary disease – Netherton syndrome, which manifests itself as scaly, red lesions all over the body.
Anatomy and physiology of skin and hair
y Trichothiodystrophy – is an autosomal recessive disease (mutation in the GTF2H5 gene known as TTDA, ERCC3 – XPB or ERCC2 – XPD). The hair is characterized by sulfur deprivation and excessive brittleness. Simultaneously changes in alopecia areata have also been reported. Deviations in biochemical tests indicate a reduced concentration of sulfur amino acids. In polarized light, the anomaly manifests itself in the form of dark and light bands.
3. Damage to the hair shaft with increased hair brittleness – acquired defects:
y Bubble hair – as the name suggests, this type of acquired damage is manifested by characteristic “bubble-like” damage to the stem, i.e. air-filled spaces. An anomaly occurs usually due to hot air styling using hair dryers, straighteners or curlers. Microscopy diagnostic shows air-filled spaces within the stem. As a preventive measure, it is recommended to cut the hair or gently care for it, and to avoid styling the hair with heat, especially in the case of damp hair.
y Nodal hair cleft (trichorrhexis nodosa) – nodal damage or breakage may be preceded by a complete breakage. It may be caused not only by genetic factors, but also by chemical or mechanical trauma (excessive hair styling, permanent wave, frequent hair straightening). Extensive damage may also occur in response to isotretinoin treatment.
y Distal hair splitting (trichoptilosis) – hair splitting, mechanical/chemical/ thermal damage caused by improper care (coloring, permanent wave), excessive styling using high temperature (curling irons, straighteners, hair dryers) or improper combing of the hair. The anomaly may also be a symptom of Menkes syndrome or occipital horn syndrome (which is a mild form of Menkes syndrome).
y Pseudonits (peripillous) – an anomaly characterized by white-yellow, tubular growths that move along the shaft and surround the hair shaft. Pseudonites are composed of keratinized cells of the sheath of the epithelium of the hair bulb, both external and internal. The changes should be differentiated from dandruff, knotty hair, mycosis and beady hair.
1.8. CHANGES IN THE CHARACTER OF THE HAIR –CHEMICAL, MECHANICAL AND THERMAL DAMAGE
1.8.1. Chemical damage
Chemical damage to the hair shaft is usually caused by chemicals typically used to change the color or texture of the hair. The oxidant applied to the hair shaft causes the breaking of disulfide bonds, which – in turn – causes an increase in the hygroscopicity of the hair, as well as reducing their resistance to external factors.
1.8. Changes in the character of the hair – chemical, mechanical and thermal damage
There are three types of bonds: disulfide bonds, salt bonds and hydrogen bonds. Disulfide bonds are also known as sulfide bonds or cystine bonds. The concentration of disulfide in the hair fibers has a significant influence on the natural appearance of the hair – the higher their concentration, the curlier the hair. These bonds can be damaged by the action of chemicals such as relaxing agents, coloring paints or oxidants. During the oxidation process, high temperature breaks the keratin chains, which consequently leads to hair breakage. In the case of chemical hair straightening, disulfide bridges are broken and the B-form keratin is changed into the A-form. In turn, hydrogen bonds are easily broken temporarily in contact with water. However, salt bonds are present throughout the hair cortex, and changes have a significant impact on their pH condition, both alkaline and acidic. Deformation of ionic bonds, i.e. so-called salt bridges, occurs when the substance is used with a pH of 5.5 or higher. It is worth emphasizing that the permanent wave treatment using thioglycolic acid esters is performed in an acidic environment (pH range 5–6).
The process of chemical hair lightening carried out in an alkaline environment involves the oxidation of melanins, i.e. pigmentation components of the hair. Natural hair pigments shrink as a result of increased keratin hydration. Chemicals brightening include peroxydisulfuric acid salts, ammoniacal hydrogen peroxide solution, or hydrogen peroxide adduct. In turn, solutions of reducing agents, such as ammonium sulfate and sodium bisulfite, act as neutralizers. In brightening preparations washing products (shampoos) use compounds such as luteolin and apigenin, which oxidize the outer layer of the hair shaft, while making it sensitive to ultraviolet rays.
1.8.2. Damage to the hair shaft
Damage to the hair shaft occurs as a result of a predisposition to the formation of hair shaft anomalies or as a result of the influence of external factors. The damage includes damage to the cortex and hair cuticle, damage to the hair root, damage to the hair sheath and damage to the root and the sebaceous gland.
1. Hair breakage – damage to the hair structure, resulting in the breakage of the hair layers.
2. Longitudinal splitting of the hair – characterized by fork-like splitting of the hair. The damage is caused by mechanical factors, such as improper hair care, excessive styling or cutting hair with blunt scissors.
3. Cleft hair – damage described in chapter 1.7 Hair shaft – defects of hair shaft.
4. Ring-shaped hair – the clinical picture of the hair is characterized by a keratinization disorder in the form of a ring around the hair shaft and alternating light and dark sections of the hair shaft.
Anatomy and physiology of skin and hair
5. Curly hair – characterized by twisting around the vertical axis of the hair.
6. Bayonet hair – characterized by thickening in the end sections of the hair shaft.
7. Multiple twin hairs – characterized by fragmentation of the papilla.
1.8.3. Dystrophic hair
Dystrophic hair is characterized by atrophy of the sheath and dysfunction of the hair matrix. Unlike normal hair, they may differ in hair curl shape, irregular contour, shade, length, and diameter thickness, because dystrophic hair may have a reduced of proximal diameter. The anomaly may occur in the case of hormonal changes, in particular the thyroid gland, as a result of treatment with non-steroidal anti-inflammatory drugs, or as a result of element deficiencies (such as zinc, iron or copper).
1.7.1.
The following hair shaft anomalies are distinguished:
1. Damage to the hair shaft without noted increased brittleness – congenital defects:
Ring-shaped hair (pili annulati) – it is a hereditary anomaly, rare, with a mild course. The clinical picture of hair is characterized by alternating dark and light bands. The anomaly is also referred to as “Morse code” hair. The characteristic appearance of the hair is caused by hair loss filled with air, which is directly related to increased light reflection. Inheritance occurs via an autosomal dominant pattern with variable expression (chromosome 12q [24.32–24.33]).
In addition, anomalies have also been reported in the case of the RECQL4 mutation associated with Rothmund-Thomson syndrome. The test results indicate that the anomaly may be a protein metabolic disorder.
Pseudopili annulati – a hair anomaly imitating pili annulati, in which an optical illusion occurs by partial twisting of the surface of the hair shaft.
1.7. Hair shaft – defects of hair shaft
Figure 1.8.
Hair shaft defects: A B Trichonodosis C
Pili multigemini D
Pili torti E Trichoclasia F Trichorrhexis invaginata G Monilethrix
