Human Hair

HUMAN HAIR

PKGhatak,MD

The hair is an appendage of the skin. The entire skin surface is covered with hair except on the palms of hands and soles of feet. Human hair is subdivided into two categories.

1. Terminal Hair. The coarser hairs that are present on the scalp, eyebrows, eyelashes, nostrils, under the armpits, pubic area; and in men mustaches and beards.

2. Body Hair. The finer hair covers the rest of the body.

Each hair has a bulbous end called a hair Follicle located in the deep layers of skin. It is supplied with nerve fibers and blood vessels. The part of the hair that remains underneath the superficial layer of skin (epidermis) is called the Root of the hair. The part of the hair on the top of the skin is called the Shaft. The cells of the hair follicles are responsible for the growth and maintenance of hair.

Under the microscope, the hair has loosely packed cells in the center called the Core. The core is surrounded by several layers of densely packed cells containing pigments, and a protein called Keratin; the outer layer of hair is made up of a single layer of cells called Cuticle.

The hair is surprisingly strong for its size. 100 strands of hair can support 20 lbs. of weight without breaking. Hair is wettable, soaks up water about a third of its weight. With air sacs in the core and water retaining property, the hair protects the head against strong sun and chill winds.

There is a small gland underneath the skin at the point where the hair emerges from the skin. It secretes a tiny amount of oil and the oil keeps hair shiny and silky looking. This oil coats all surfaces of straight hair evenly; in persons with wavy or kinky hairs the oil cannot get to the entire shaft uniformly and these types of hair look dry and disorderly.

The body hairs grow slowly, whereas scalp hairs grow about 1 inch in 3 months. The rate of growth is slower in older people and fastest in adolescence. Growth takes place at the root of the hair, and as hair grows it sprouts out of the skin surface. Each individual hair has its own life cycle; independent of its neighbors. It decides when to grow, when to rest and when to die and fall off. And then it begins to grow again and the cycle continues. Because we lose so few hairs at a time that we do not notice the hair loss. Hair on the scalp grows to shoulder length in 3 years and reaches waist length in 5 years. Generally, after 6 years growth stops and hair rests for a period of time and at the end of 6 to 7 years it dies and falls off. During its lifetime, a hair may grow 5 feet in length if not trimmed. In the Guinness Book of Records, you may find evidence of longer hair. Body hair has a shorter life and growth remains limited.

The keratin of hair gives hair its flexibility and strength. It is made of amino acids of which Cystine has a disulfide bond. This disulfide bond gives keratin its special properties. When hairs are treated with alkaline agents this disulfide bond is weakened and curly hairs could be strengthened or straight hair may be given a curly shape. Then an acidic agent is applied to neutralize alkali and to make the changes last longer. The color of hair is due to the presence of a pigment called Melanin produced at the root of the hair by cells called Melanocytes. Two types of melanin are produced by these cells. Long arms of these cells deposit the pigments in rows, like a string of pearls, in the cortex cells of the hair. One color is black and the other is red. By the various combination of these two pigments, hairs get various shades of black, brown, yellow and red. The gray color of hair is due to the presence of only a few melanin pigments, non-pigmented hair looks yellowish due to the color of keratin.

The terminal hair depends on Androgen for its regulation of longitudinal growth, thickness, and vigor, whereas Estrogen slows the growth rate but prolongs the growth period. The thyroid hormone maintains its health. Body hair depends mostly on thyroid hormone for its health and growth. Zinc and B vitamins, particularly pantothenic acid, is required for the nutrition of hair. Steroid hormone may slow or weaken roots of hairs when used for a prolonged period. Certain chemicals like arsenic are taken up by the hair and remain unchanged in hairs for years even after burials. Drugs used in cancer treatment may arrest the growth of all fast growing cells of the roots of hair all at the same time, making hairs fall off in 2 to 3 weeks. But after completion of treatment hair will grow back. Thallium used in cardiac stress laboratories may cause hair to fall for the same reason. Many other drugs may influence hair one way or other.

The roots of the hair are the living part of the hair. The shaft of hair is a dead tissue. The DNA of hair cells can help identify an individual.

In hair, we admire the texture, wave, color, and silkiness - all about a dead tissue and the living part is unseen and remains buried under the skin.

 

 

revised 2020

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Blood Sugar

Blood sugar

PKGhatak,MD

We need energy at all times just to stay alive and a higher rate of energy supply when we are engaged in activities. The lowest rate of energy requirement for an average person is 70 Kilocalories/hr. (Kcal); this is also called the Basic Metabolic Rate (BMR). The actual BMR varies according to height, weight, gender, age and ethnicity of the person and on the climate conditions.

The sugar that circulates in our blood is Glucose; table sugar is sucrose made up of one molecule each of glucose and fructose; milk sugar is lactose; a combination of glucose and galactose and fruits contain fructose. All sugars belong to a group called carbohydrates; also present in this group are- starch, dextrin, corn syrup, potatoes, wheat, cereal and rice. The body, for the most part, must break down starch and other sugars into glucose before turning glucose into energy. The human body is unable to break down cellulose, the most abundant carbohydrate in nature, the main constituent of trees and other vegetation. Cellulose provides the bulk of our daily meals.

As we eat food it gets mixed with saliva. Saliva contains an enzyme called Amylase and it begins to break down carbohydrates. The process continues in the stomach and in the upper small intestine where more amylase comes from the pancreas. As glucose is generated from other sugars and the breakdown of starch, it is picked up by the cells of the small intestine and then transported to the liver via blood. Any excess amount of glucose in the liver is converted into a complex glucose structure called Glycogen (commonly known as animal starch). The liver can easily turn glycogen into glucose and release it in circulation whenever there is a need. The muscles of our body store Glycogen as fuel for work.

Every living cell of the body has a chemical factory called Mitochondria. It is loaded with enzymes, catalysts, and a high-energy fuel packet called Adenosine Tri Phosphate (ATP). A chemical process called the Tricarboxylic acid cycle, better known as the Krebs cycle, is the main energy producing process in the body. We can view it as a furnace having three entry gates; one for the sugars, the other one for amino acids (derived from break down of proteins) and the third one for fatty acids (comes from fat). The products coming out of the Kerbs cycles are heat, ATPs, and other intermediate products. These intermediate products are in turn synthesized into fat, proteins, hormones, and other essential chemicals in the liver and other specific organs. Outside the mitochondria but within the cells, there is another process where glucose is directly converted into energy through a chemical pathway known as Hexose monophosphate shunt.

You must have known a friend or relative who would not add a grain of sugar in his coffee but at the same time drink two glasses of wine and finish half a bottle of ketchup over two hot dogs. They tend not to remember wine and prepared food containing carbohydrates. Yes, wine and drinks containing alcohol are carbohydrates. We eat about 300gm of carbohydrates on an average day; we need a minimum of 150 gm of carbohydrates daily in order to keep the chemical fire going in the body. When the minimum amount of carbohydrates is not present in the diet, the Krebs cycle will generate acetone from partially utilized amino acids and fatty acids. The human body cannot break acetone further. It is an acidic substance. It makes the cells sick and the kidneys work extra hard to eliminate acids. The appetite is lost and respiration becomes hurried. Over a period of time, the person loses weight. That is the basis of a high protein, low carbohydrate diet. It works for a short period of time but it is a different story a year or two later.

You must have noticed that in order to utilize sugar it must enter the cells first and then find its way to the mitochondria. In nature, nothing is left to a chance. The cell walls have pores, gates, binding sites, messengers, and controllers. Of these factors, Insulin is the most important member for glucose utilization. It is a hormone produced in the pancreas by Beta cells. If insulin is absent in the body or produced in less than normal amounts or the insulin is biochemically defective or antibodies against insulin making Insulin less effective. This will raise blood sugar levels in the blood. When the blood level exceeds the normal range, the condition is called Diabetes.

Normal blood sugar in the fasting state is less than 100 mg /100ml. When it exceeds 180 mg the sugar begins to show up in the urine. After a meal, depending upon the amount of carbohydrate ingested, the blood sugar may be anywhere from 100 to 180 mg/100 ml in normal individuals; in diabetics, it may be 200 mg or higher. In rare circumstances, the sugar may reach 1000 to 1200 mg /100ml.

The blood sugar may fall from having too much insulin in the body, from an insulin producing tumor or insulin administered inappropriately, or, in starvation or in conditions preventing a person from swallowing. When the level falls below 60 mg the person feels hungry, jittery, and tense and begins to sweat; when the level falls below 30 mg the person becomes confused and may behave in bizarre ways. In extreme cases of low sugar (hypoglycemia) unconsciousness, coma and death may follow.

Another hormone called Glucagon is produced by the alpha cells of the pancreas. Glucagon breaks down liver Glycogen into blood sugar and raises sugar levels.   Steroid hormones and adrenaline from adrenal glands are released in response to hypoglycemia and counteract some of these symptoms.

 

Normal blood sugar in an individual requires a balance between several hormones, insulin, food and a healthy gastrointestinal tract. In a diabetic individual, in addition to these, the level of physical activity is important also.

 

edited 2020.