Structure and function of the skin

The brain gathers information about the outside environment through the senses. Special sense organs and generic sense organs are two common categories for the sense organs.

In the past, the five senses of taste, smell, sight, hearing, and touch were acknowledged. But today, touch is viewed as a general sense made up of various types of nerve endings dispersed all over the body. The remaining five senses—balance added—taste, smell, sight, and hearing—are now referred to as the special senses. They are made up of extremely specialized sensory cells and highly localized organs. Since the sensations are the result of molecules interacting with receptors for smell or taste, smell and taste are both chemical senses. Light stimulation affects how the sense of vision functions. While both hearing and balance are mechanically stimulated, balance is stimulated by gravity or motion, whereas hearing is stimulated by sound waves.

Sensory Pathway

Regardless of their size, shape, or location, all sense organs share some crucial functional traits. They must first be able to feel or recognize a stimuli in their surroundings. Of course, many senses pick up on and react to various stimuli in various ways. The stimulus must be converted into an electrical signal or nerve impulse, regardless of whether it is light, sound, a change in temperature, or the presence of molecules that are classified as taste or smell. This signal is then sent to the brain via a "pathway" in the nervous system, where the sensation is felt.

The Skin

The body's exterior is covered in skin. In terms of weight and surface area, it is the largest organ in the body. The skin weighs 4.5–5 kg and extends over a surface area of nearly 2 square meters (2 m2). On the majority of the body part, it is 1-2 mm thick. The skin is the easiest body organ to examine. It is more vulnerable to injury, illness, and infection because of its exterior placement.

Structure of the Skin

Two main components make up the skin. which are

• Epidermis
• Dermis

Epidermis

The epidermis is the outer, superficial, thinner (0.1-0.2mm), stratified squamous epithelium layer of the skin. It lacks a supply of nerves and blood. The epidermis primarily consists of four types of cells:

• Keratinocytes
• Melanocytes
• Langerhans cells
• Merkel cells

The keratin protein, which is made by keratinocytes, shields the skin and underlying tissues from heat, bacteria, and pollutants. Keratinocytes make up most epidermal cells, about 90%. Melanin, a pigment that gives skin its color and absorbs harmful ultraviolet (UV) rays, is produced by melanocytes. Melanocytes make up about 8% of the epidermal cells. Invading germs are repelled by the skin's Langerhans cells. The epidermis's deepest layer contains Merkel cells, which are responsible for detecting touch.

Four to five strata or layers make up the epidermis in the majority of body regions. which are

• Stratum cornium,
• Stratum lucidium,
• Stratum granulosum,
• Stratum spinosum,
• Stratum basale,

Stratum Cornium

• Is the thicker, keratinized, outer, flat layer. It is made up of 25–30 layers of decomposed keratinocytes. Continuously shed, deeper layer cells take its place.

Stratum Lucidium

• Is close to stratum cornium. It is made up of translucent, flat cell layers. The thick skin of places like the fingertips, palms, and soles contains this stratum.

Stratum Granulosum

• Lies immediately beneath stratum lucidium. The keratinization of the cells in this layer is currently occurring.

Stratum Spinosum

• Lies beneath the stratum granulosum. The cells in this stratum are poly-hydral in shape and are synthesizing proteins.

Stratum Basale

• Is the final layer of epidermis before stratum spinosum, and it rests on the basement membrane. Because it is responsible for the formation of new cells, this layer is also known as the stratum germinativum.

Dermis

The deeper layer of the skin is known as the dermis. Collagen and elastic fibers make up the strong connective tissue network that makes up this structure. The dermis receives its tremendous strength to stretch and recoil from this network. Dermis makes up the majority of the skin. The dermal layer contains blood vessels, nerves, glands, and hair follicles.

The dermis is made up of deeper reticular layers and superficial papillary layers.

Papillary Layer

• It is situated close to the epidermis's stratum basale. The bundles of collagenous fibers contain loose connective tissue. It also has leaky capillaries that provide the epidermis with nutrients. In some locations, the papillary layer has unique nerve endings known as Meissner's corpuscles, which act as touch receptors. Papillary layer indentations on the soles and palms reflected over the epidermis to form ridges.

Reticular Layer

• The papillary layer is nearby. It is composed of thick connective tissue with crisscrossing bundles of collagenous fibers that form a stroma of elastic network. Numerous blood and lymphatic vessels, nerves, fat cells, sebaceous (oil) glands, and hair roots are embedded in the reticular layer.

Functions of the Skin

• Protection
  • It guards against harmful microorganisms, foreign objects, and excessive fluid loss from the body.
• Temperature Regulation
  • The sweat removes heat from the body.
• Excretion
  • A small amount of waste products, including urea and sodium chloride, are excreted from the body through sweat.
• Absorption
  • The skin absorbs certain medications, the gases oxygen and carbon dioxide, as well as the fat-soluble vitamins A, D, E, and K.
• Synthesis
  • In response to UV radiation from sunshine, the skin produces vitamin D. For the intestine to properly absorb calcium, vitamin D is required.
• Sensory Reception
  • It has sensory receptors for pain, touch, pressure, heat, and cold.