A hair follicle is a part of the skin, which grows a hair by packing old cells together. Attached inside the top of the follicle are sebaceous glands, which are tiny sebum-producing glands in almost all skin except on the palms, lips and soles of the feet. The thicker the hair, the more the number of sebaceous glands there are.
Also attached to the follicle is a tiny bundle of muscle fiber, called the "arrector pili", which is responsible for causing the follicle lissis to become more upright the surface of the skin. The muscle area can also cause the follicle to stick up slightly above the nearby skin (piloerection) with a pore incased with skin oil. This process results in goose bumps (or goose flesh). Stem cells are at the junction of the arrector and the follicle, and are principally responsible for the ongoing hair production during a process known as the Anagen stage.
The average growth rate of healthy hair follicles on the scalp is nearly per month.
At the base of the follicle is a structure that is called the papilla. The papilla is made up mainly of connective tissue and a capillary loop. Cell division in the papilla is either rare or non-existent.
Around the papilla is the hair matrix, a collection of epithelial cells often mixed with the pigment-producing (color) cells, known as melanocytes. Cell division in the hair matrix is responsible for the cells that will form the major structures of the hair fiber and the inner root sheath. The hair matrix epithelium is one of the fastest-growing cell areas in the human body, which is why some forms of chemotherapy which kill dividing cells or radiotherapy may lead to temporary hair loss. The papilla is usually oval or pear-shaped, with the matrix wrapped almost totally around it, except for a short stalk-like connection to the surrounding connective tissue that provides access for the capillary.
The root sheath is composed of an external (outside) and internal (inside) root sheath. The external root sheath appears empty with cuboid cells when stained with H&E stain. The internal root sheath is composed of three layers, Henle's layer, Huxley's layer, and an internal cuticle that is continuous with the outer layer of the hair fiber.
The hair fiber is composed of a cuticle that is continuous with the root sheath, an intermediate cortex, and an inner medulla.
The bulge is in the outer root sheath at the insertion point of the arrector pili muscle. It houses several types of stem cells, which supply the entire hair follicle with new cells, and take part in healing the epidermis after a wound.
Other structures associated with the hair follicle include arrector pili muscles, sebaceous glands and apocrine sweat glands. Hair follicle nerve receptors sense the position of the hairs.
Before a baby is born, the epithelium and underlying mesenchyma interact to form hair follicles.
Hair grows in cycles of various phases: anagen is the growth phase; catagen is the involuting or regressing phase; and telogen, the resting or quiescent (still) phase. Each phase has several morphologically and histologically distinguishable sub-phases. Prior to the start of cycling is a phase of follicular morphogenesis (formation of the follicle). There is also a shedding phase, or exogen, that is independent of anagen and telogen in which one of several hairs that might arise from a single follicle exits. Normally up to 90% of the hair follicles are in anagen phase while, 10–14% are in telogen and 1–2% in catagen phase. The cycle's length varies on different parts of the body. For eyebrows, the cycle is completed in around 4 months, while it takes the scalp 3–4 years to finish; this is the reason eyebrow hairs have a much shorter length limit compared to hairs on the head. Growth cycles are controlled by a chemical signal like epidermal growth factor.
Anagen is the color phase of hair follicles. The color of your hair will start to fade because the cell only last a couple months.
The catagen phase is a short transition stage that occurs at the end of the anagen phase. It signals the end of the active growth of a hair. This phase lasts for about 2–3 weeks while a club hair is formed.
The telogen phase is the resting phase of the hair follicle. The club hair is the final product of a hair follicle in the telogen stage, and is a dead, fully keratinized hair. Fifty to one-hundred club hairs are shed daily from a normal scalp.
Pirelli
Pirelli & C. SpA is a diverse (it does many things) company based in Milan, Italy. It operates in many countries.
Pirelli was founded 1872 in Milan by Giovanni Battista Pirelli. Pirelli initially worked in rubber and related processes. The company used to make scuba diving rebreathers (a special type of underwater breathing machine). Pirelli's activities are still focused on the building of tyres and cables (for energy and telecommunications). In 2005, Pirelli sold its cable division to Goldman Sachs, which changed the new group's name to "Prysmian".
In the 1950s, Alberto Pirelli had the famous Milanese skyscraper built. It is in the same area as the first Pirelli factory in the 19th century.
In 1974, Pirelli invented the "wide radial tyre". This was at the request from the Lancia rally racing team. They needed a tyre strong enough for their new Stratos.
Later, Porsche started using the same tyres with the Porsche 911 Turbo.
Today, the wide tyres are still the standard in sport & racing cars.
The "Pirelli Calendar" is published once a year. It often features famous actresses and fashion models. The calendar also features the work of many well respected fashion photographers.
The "Pirelli Internetional Award" is given annually for the best international multimedia involving the communication of Science & Technology conducted entirely on the Internet.
"Power is nothing without control" is the slogan of Pirelli Tyre Company.
Pirelli is the long time main sponsor of Italian football club "F.C. Internazionale Milano".
Pirelli has a history of sponsoring football teams. Pirelli is known for its long term primary sponsorship of the Italian football team Internazionale Milano F.C. Pirelli also supports rally. Pirelli Star Driver is an project to support young rally drivers. It is organised by Pirelli and the FIA.
Since 2007, Pirelli is the only tyre brand used in the FIM World Superbike Championship. The tyres are also used in the support classes.
Pirelli has the contract for the control tyre supply in the British Superbike Championship. This contract started in 2008 and will last until 2010 at least.
Pirelli is the official tyre supplier of the World Rally Championship. They replaced BF Goodrich for the 2008 season.
Pirelli competed in Formula One in three distinct periods. The first time was between and . The second time was between and . The third time was between and . They started 200 Grands Prix races, and won 44 of them.
Pirelli will return to the sport in as the sole tyre supplier. Bridgestone decided to withdraw as the supplier at the end of .
To test the new F1 tyre, Pirelli signed Nick Heidfeld. A 2009 version of a Toyota Racing chassis is being used to test the tyres. The testing is taking place during the second half of the season. In September 2010, Heidfeld was signed by Sauber to race the remainder of the season. Pirelli then hired former GP2 and Renault F1 driver Romain Grosjean to test for them.
Ball (dance)
A ball is a formal dance occasion. By formal is meant: people were invited, wore their best clothes ('evening attire'), and the ball was held in a splendid ballroom. In former times everyone danced, but only the wealthy went to balls. Girls had dance cards: men had to sign up to dance with them. Older people sat around the sides and watched the younger people dance. It was a society occasion.
Robin Warren