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Monday, May 30, 2011

Types Of Glands - Lesson 246

In this post we  would learn about glands of different types.
1. Sebaceous Glands: These glands are located in the corium layer of the skin over the entire body, ;with the exception of the palms (hands) and soles (feet). The oily substance which they secrete is called sebum. Sebum, which contains lipids, lubricates the skin and minimizes water loss. The sebaceous glands which are closely associated with hair follicles, and their ducts open into the hair follicle through which the sebum is released. These sebaceous are influenced by sex hormones, which cause them to hypertrophy at puberty and atrophy in old age. Overproduction of sebum during puberty contributes to blackhead (comedo) formation and acne in some individuals.

2. Sweat Glands: These glands are tiny, coiled glands found on almost all body surfaces (about two million in the body). In the palm of the hand they are very large in number (3000 glands per sq in) and on the sole of the foot. The coiled sweat gland originates deep in the corium and straightens out to extend up through the epidermis. The tiny opening on the surface is called a pore. 

The form of sweat, or perspiration is almost pure water, with dissolved materials such as salt making up less than 1 per cent of the total composition. It is colorless and odorless. The odor produced when sweat accumulates on the skin is due to the action of bacteria on the sweat. Sweat which cools the body as it evaporates into the air. The sympathetic nervous system controls the perspiration, whose nerve fibres are activated by the heart regulatory center in the hypothalamic region of the brain, which stimulates sweating.

The sweat gland which is a kind of special variety is active only from puberty onward and larger than the ordinary kind is concentrated in a few areas of the body which is adjacent the reproductive organs and the armpits. These glands, would secrete an odorless sweat, but it contains certain substances that are easily broken down by bacteria on the skin. The breakdown products are responsible for the characteristic human body odor. The milk-producing mammary gland is another type of modified sweat gland: it secretes milk only after the birth of a child.

In the next post we would go through vocabulary.

Tags: sebaceous sweat glands, sebaceous gland carcinoma, sebaceous glands hair follicles, overactive sweat glands, infected sweat glands, swollen sweat glands, blocked sweat gland, sweat glands in armpit, what are sweat glands, removal of sweat glands

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Monday, May 23, 2011

Accessory Organs Of The Skin - - Lesson 245

In this post we would learn about ‘accessory organs of the skin’. Then in our mind one question may arise? What are the accessory organs of the skin?
1. Hair: A fiber of hair is composed or consisted of a tightly fused meshwork of horny cells filled with the hard protein also called keratin. The growth of hair is similar to the growth of the epidermal layer of the skin. Deep-lying cells in the hair root which produce horny cells that move upwards or to the top through the hair follicles (shafts or sacs that hold the hair fibers). At the root of the hair follicle, melanocytes are located and they support the melanin pigment for the horny cells of the hair fiber. Whenever the melanocytes stop producing melanin, hair turns gray. Out of the five million hairs on the body, about 100,000 are on the head. They grow about a half inch (1.3cm) a month, and cutting the hair has no effect on its rate of growth.

2. Nails: Nails are hard, the plates called keratin plates covering the dorsal surface of the last bone of each toe and finger. They are composed of horny cells that are cemented together tightly and can extend indefinitely unless cut or broken. As a result of division of cells in the region of the nail root, a nail grows in thickness and length, which is at the base or proximal portion of the nail plate. Mostly nails grow about one mm a week, which means that the re-growth of fingernails may occur in 3-5 months. Toenails which grow more slowly than fingernails, it takes 12-18 months for toenails to be replaced completely.

The ‘lunula’ is a semilunar(half-moon), white region of the base of the nail plate, and it is normally found in the thumbnail of most people and in differing degrees in other fingers. Air mixed in with keratin and cells rich in nuclei give the lunula its whitish color. The cuticle, a narrow band of epidermis(layer of keratin), is at the base and sides of the nail plate. The growth of the nail and appearance are frequently altered during systemic disease. For example, grooves in nails may occur with high fevers and serious illness, and spoon nails(flattening of the nail plate) occurs in iron deficiency anemia.                                                                                             

In the next post we would learn about ‘glands’.

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Saturday, May 14, 2011

FUNCTIONS OF DERMIS AND SUBCUTANEOUS LAYER -- LESSON 244

In this post we would learn about the remaining part of the dermis and subcutaneous layer.
In the previous post we came across that the dermis is a layer of skin which is between epidermis and the subcutaneous tissues. This corium consists of interwoven elastic and collagen fibers in which colla- means glue is a fibrous protein material found in bone, cartilage, tendons, and ligaments, as well as in the skin. It is not only tough and resistant but also flexible. In kids, collagen is loose and delicate, and it becomes harder as the body ages. In women who bears pregnancy, overstretching of a woman’s skin may break the elastic collagen fibers and stretch the collagen resulting in linear markings called striae or stretch marks. Collagen fibers support and protect the blood and nerve networks that pass through the corium. This collagen diseases affect the connective tissues of the body. The examples of these connective tissue collages disorders are systemic lupus erythematosus and scleroderma. This dermis is composed of three types of major cells. They are 1. Fibroblasts,  2. Macrophages and 3. Adipocytes.

Subcutaneous layer:
The subcutaneous layer of the skin is another connective tissue layer. This tissue makes up deepest layer of the skin. It also helps to hold skin to all the tissues underneath it. It specializes in the formation of lipocytes or fatcells which are predominant in the subcutaneous layer, and they manufacture and store large quantities of fat. Subcutaneous fat can be measured by using body fat calipers giving a rough estimate of total body adiposity. Injection into the subcutaneous tissue is a administrated route of type insulin. Obviously, areas of the body and individuals vary as far as fat deposition is concerned. Functionally, this layer of the skin is important in protection of the deeper tissues of the body and as a heat insulator.

In the next post we would learn about ‘Accessory Organs of the skin’.

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Friday, May 6, 2011

FUNCTIONS OF EPIDERMIS AND CORIUM - LESSON 243

In this post we will learn the functions of epidermis and about Dermis or Corium.
In the last lesson we have learnt upto Melanocytes. Melanocytes form and consist of a black pigment called melanin that is transferred to other epidermal cells and gives color to the skin. In several races, the amount of melanin accounts for the color differences, but the number of melanocytes in all races is same. Individuals who possess darker skin contain more melanin within the melanocytes, not a larger number of melanocytes. For protection against the harmful effects of ultraviolet radiation, the presence of melanin in the epidermis is vital, which can manifest themselves as skin cancer. The persons or individuals who, through a flaw in their chemical makeup are incapable of forming melanin at all which are called albino (means white). Those persons will get skin and hair white. Their eyes because in the absence of pigment, the tiny blood vessels are visible in the iris (normally pigmented portion) of the eye.

The production of melanin increases with exposure to strong ultraviolet light, and this creates a suntan, which is a protective response. The skin becomes sunburned and inflamed (redness, swelling, and pain) when the melanin cannot absorb all the ultraviolet rays. Over a period of years, excessive or more exposure to sun can tend to cause wrinkles and cancer of the skin. Darker people (with dark skin) get less likely to develop skin cancer because the dark-skinned people have more melanin and also they have fewer wrinkles.

Corium (Dermis):-
The corium is also called dermis is a layer, directly below the epidermis. It is composed of blood and lymph vessels and nerve fibres, as well as the accessory organs of the skin, which are the hair follicles, sweat glands, and sebaceous glands. The supposition of the elaborate system of nerves, vessels, and glands, the corium contains connective tissue cells and fibers that account for the extensibility and elasticity of the skin.

In the next post we will learn about the remaining part of the dermis.

OK………..

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