Skin Care Secrets
All About Your Skin
Your skin is an organ composed of a layer of
tissues that protect underlying muscles and organs. Skin is used for
insulation, vitamin D production, sensation, and excretion (through
sweat).
Mammalian skin often contains hairs, which in sufficient
density is called fur. The hair mainly serves to augment the insulation
the skin provides. On some animals the skin is very hard and thick,
and can be processed to create leather.
Damaged skin will try to heal by forming scar tissue,
often giving rise to discoloration and depigmentation of the skin.
The skin is often known as "the largest organ
in the human body": this applies to exterior surface, as it covers
the body, appearing to have the largest surface area of all the organs.
Moreover, it applies to weight, as it weighs more than any single
internal organ. For the average adult homo sapiens, it has a surface
area of between 1.5-2.0 square metres.
The skin on a person's face is seen by people that
person interacts with. For some people, then, facial skin care is
of importance, and cosmetics are made to deal with the appearance
of the person's face and condition of the skin, such as pore control
and blackhead cleansing.
Skin Layers
Skin is composed of the epidermis and the dermis.
Below these layers lies the hypodermis, which is not usually classified
as a layer of skin.
The outermost epidermis is made up of stratified squamous
epithelium with an underlying basement membrane. It contains no blood
vessels, and is nourished by diffusion from the dermis. The main type
of cells which make up the epidermis are keratinocytes, with melanocytes
and Langerhans cells also present.
The epidermis can be further subdivided in to the
following strata (beginning with the outermost layer): corneum, lucidum,
granulosum, spinosum, basale. Cells are formed through mitosis at
the innermost layers.
They move up the strata changing shape and composition
as they differentiate and become filled with keratin. They eventually
reach the corneum and become sloughed off. This process is called
keratinization and takes place within about 30 days.
Blood capillaries are found beneath the epidermis,
and are linked to an arteriole and a venule. Arterial shunt vessels
may bypass the network in ears, the nose and fingertips.
The dermis lies below the epidermis and contains a
number of structures including blood vessels, nerves, hair follicles,
smooth muscle, glands and lymphatic tissue. It is made up of dense
connective tissue - collagen, elastin and reticular fibres are present.
Erector muscles, attached between the hair papilla
and epidermis, can contract, resulting in the hair fibre pulled upright
and consequentially goose bumps. The main cell types are fibroblasts,
adipocytes (fat storage) and macrophages.
Sebaceous glands are exocrine glands which produce
sebum, a mixture of lipids and waxy substances: lubrication, water-proofing,
softening and antibatericidal actions are among the many functions
of sebum. Sweat glands open up via a duct onto the skin by a pore.
The dermis can be split in to the papillary and reticular
layers. The papillary layer is outermost and extends in to the dermis
to supply it with vessels. It is composed of loosely arranged fibres.
Papillary ridges make up the lines of the hands. The reticular layer
is more dense and is continuous with the hypodermis. It contains the
bulk of the structures (such as sweat glands). The reticular layer
is composed of irregularly arranged fibres and resists stretching.
The hypodermis is not part of the skin, and lies below
the dermis. Its purpose is to attach the skin to underlying bone and
muscle as well as supplying it with blood vessels and nerves. It is
made up of loose connective tissue and elastin. The main cell types
are fibroblasts, macrophages and adipocytes (the hypodermis contains
50% of body fat). Fat serves as padding and insulation for the body.
Skin Types
Skin can be divided into thick and thin types. Thick
skin is present on the soles of the feet and the palms of the hands.
It has a larger stratum corneum with a higher keratin content. Thick
skin does not grow hair; its purpose is to help grip. Thin skin is
present on the bulk of the body and has a smaller stratum corneum
and fewer papillae ridges. It has hair and is softer and more elastic.
Functions of the Skin
Protection: a barrier between the
internal and external environment in bodily defence
Sensation: enables irritability
Storage: acts as a storage centre
for lipids and water, as well as a means of synthesis of vitamin D
by action of UV on certain parts of the skin.
Absorption: Oxygen, nitrogen and
carbon dioxide can diffuse into the epidermis in small amounts.
Excretion: The concentration of urea
is 1/130th than that of urine. Excretion by sweating is at most a
secondary function to temperature regulation.
Skin Aging and Disease
As skin ages, it becomes thinner and more easily damaged.
Intensifying this effect is the decreasing ability of skin to heal
itself. Skin sagging is caused by the fall in elasticity. Skin also
receives less blood flow and lower gland activity.
In medicine, the branch concerned with the skin is
called dermatology.
The skin is subject to constant attack from without,
and so can be afflicted by numerous ailments, such as:
- Skin cancer
- Rashes
- Blisters
- Acne
- Fungal infections such as athlete's foot
- microbial infections.
- calcinosis cutis
- ulcer
Moles
A mole is a small spot of darkened pigment on the
skin, which forms where there is a high concentration of melanin.
Moles are usually circular or oval and not very large.
Most children are born with moles, and almost everyone has at least
one or two moles on their bodies, some more than others.
Sudden and unexpected changes in skin moles (e.g.
bleeding, irritation, darkening, sudden growth) can be a sign of skin
cancer so they need to be watched carefully. If a mole appears suspicious,
it can be biopsied and checked for signs of malignancy.
From Wikipedia
