Histology and Physiology of the Skin


The eccrine sweat glands illustrated in the model by gold bundled rope, can be found all over the body and serve to regulate body temperature as well as excrete waste, although the body only excretes about 1% of toxins through this appendage of the excretory system. These glands are ducted out through the sweat pore, as opposed to apocrine glands which duct into the follicle. These apocrine excretions combines with p. bacteria and sebum leading to the odors associated with sudoriferous activity of the the axillae, genitals and feet.

The afferent sensory nerve channels are depicted in purple leading to several neurological appendages known as "mechanoreceptors": 

The "K" represents Krause's corpuscle, responsible for detecting cold. These send signals to the autonomic nervous system causing the arrector pilli muscles to contract, causing what we know as "goosebumps."
The "M" serves to depict Meissner's or "tactile" corpuscle, which responds to very light touch, changes in texture, and low frequency vibration. They are found throughout the integumentary system, but most concentrated in the lips and fingertips.
The "P" represents the Pacinian or "lamellar" corpuscle, responsible for sensations of vibration and pressure. They only respond to sudden stimuli.
The "R" represents Ruffini's corpuscle, found throughout the dermis. This appendage detects sensations of warmth and stretch. They are most concentrated in the hands to provide awareness and controll of finger position, making them essential to our perception of both grip and slip.
The rotary blade represents the Merkel discs which are very sensitive to skin indentation, pressure, hair movement, and other tactile stimuli.
The purple ribbon leading to the hair papilla depicts the hair follicle receptor, which is sensitve to touch.

The red ribbon depicts arterioles feeding the capillaries within the hair papilla. This ultimately provides the papilla with all of the nutrients, water, and oxygen necessary to grow the hair.
The blue ribbon represents the venules leading deoxygenated blood away from the pilosebaceous unit toward the heart and liver to be detoxified and oxygenated. These blood vessels extend throughout the dermis where there is direct blood supply. The live tissue of the epidermis, however, is fed through seeping of interstitial fluid through the dermal epidermal junction, as there is no direct blood supply.


The white paper with black lettering and the long brown paper protruding from within it represent the pilosebaceous unit.


The brown protrusion is representative of terminal hair in the anogen phase. This hair is attatched to the hair papilla by the hair bulb, where mitosis within the matrix forms the hair, external root sheath, and internal root sheath (tissue visible at base of hair during epilation).

The white paper surrounding the hair in the model represents the external root sheath, epithelial tissue lining the follicle.
"Valentino Garavani" is the sebaceous gland of the model. This gland produces sebum, which ducts into the follicle and out through the pores. The activity of this gland is what determines skin type, and consequentially is the largest guiding factor in determining ideology of conditions for which clients seek the help of estheticians.
The yellow glitter represents sebum, a protective oil that helps retain moisture and protect the skin from environmental factors. This material contributes to our acid mantle, a hydroplipidic film composed of sweat and sebum.
"Chanel" represents the arrector pilli muscle, which contributes to the thermoregulatory component of the integumentary system. When triggered by the autonomic nervous system's response to low temperatures detected by Krause's corpuscle, this muscle contracts, causing the pilosebaceous unit to shift, making hair stand straight up. This function is thought to insulate the skin by creating small air pockets, though the exact purpose for this function is unknown.

The subcutis (aka: subcutaneous layer, superficial fascia, adipose layer, or hypodermis) is composed primarily of adipocytes, which are loose connective tissue pictured in the model as large white masses. This layer of the integumentary system is comprised of 80% fat (aka adipose or subcutis tissue). This layer provides energy for the body and also contains bloodvessels, nerves, fibers, and fibroblasts. This layer provides contour and smoothness to the skin, but degrades with age. This loss of tissue can lead to a sagging sunken in appearance. This layer of the skin also aids in thermoregulation. 

The reticular layer of the dermis (aka: true skin, cutis, derma, or corium) is the denser and deeper of the two components of the dermis. It is pictured in the model as the deep brown pixelated later. The reticular layer is composed primerily of collagen and elastin fibers. Collagen is responsible for giving skin its strength and firmness, while elastin is responsible for giving the skin its elasticity. This layer makes up 80-90% of the dermis, which is 25x thicher than the epidermis.

The papillary layer of the dermis connects the reticular layer to the epidermis through a membrane of ridges and grooves called the dermal papillae. In the model this is the top later with the outlive of the trees representing the ridges of the dermal papilla Attached to the dermal papillae are either looped capillaries that nourish the basal cells of the epidermis or Merkel's disc. In this layer of the dermis, collagen and elastin are more widely spaced out.

The thin blue layer of sky above the trees in the model represents the dermal/epidermal junction which is where the dermis and epidermis connect. Collagen fibrils from the dermis and keratin fillaments from the epidermis adhere the two layers together at the DEJ.

This page depicts four of the five layers of the epidermis. The stratum lucidum (between the stratum granulosum and stratum corneum) has been omitted because it appears only on the palms, soles of the feet, eyes, and lips where hair follicles are not present. The stratum lucidum is responsible for our fingerprints, and the thickness of our palms and soles, thought to be an evolutionary adaptation to provide cushion for walking and better grip.

The bottom most layer of eyes represents the stratum germinativum (aka basal layer, stratum basale, birthing room, basement layer consists of a single layer of cells, primarily keratinocytes. These mother cells undergo mitosis, diving into two identical cells, providing the cells of the stratum spinosum. 
The jeweled eye in this layer that extends into the stratum spinosum represents a melanocyte. These cells produce melanosomes (pictured as the round jewels with glitter on them), that the melanocytes inject into keratinocytes in the stratum spinosom. Theres a 36:1 ratio of keratinocytes to melanocytes, respectively.
The merkel cell sensitive touch receptors are also found in this layer of the epidermis.

The next layer in the model depicts the small rectangular images, representing the spiny keratinocytes. In this layer cells coninue to divide and change shape. At this point the desmosomes of these cells push out of the cell giving them this spiny appearance. These desmosomes help strengthen and hold the cells together. In this layer, the keratinocytes have been injected with the melanosomes containing melanin. The lips in this layer represent a langerhans cell, which is a component of the immune function of the integumentary system. The langerhans cells are scavengers or any foreign bodies that could cause illness or harm. This is the largest layer of te epidermis.

The next layer of the model is an even smaller more compact collection of images representing the stratum granulosum (aka granular/grainy layer, big bang layer). It's in this layer of the epidermis that the melanosomes injected into the keratinoctyes explode, as depicted by the glitter on the images in the model. This glitter represents our melanin, the body's only natural defense to toxic UVA and UVB rays. These pigment granules have an SPF of four and act as an umbrella to protect the nucleus from direct sunlight. In this layer, cells excrete intercellular lipids, triglycerides, waxes, ceramides, fatty acids that help to defend agains transepidermal water loss (TEWL). Enzymes dissolve the desmosomes of the keratinocytes, and these cells become keratinized as the move up toward the stratum corneum. 

The last layer of the model represents the stratum corneum or "horny" layer. This semipermeable layer is composed of dead, hardened, dried up corneocytes glued together by the intercellular matrix of NMFs, They are referred to as "horny" becuase of their scaly appearance. Keratinocytes here secrete their lamellar granules creating a hydrophobic barrier to protect the skin. At the top of the model, photographs are drifting off the page, representing desquamating corneocytes. The cell turnover rate from a cell birthed in the stratum germinativum to being naturally shed is about 30 until age 30, where it increases by about an additional day for every year.

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