Basal cell layer of epidermal skin - Stratum basale (germinativum)

Home > Know your skin > Epidermis > Basal cell layer of epidermis

Basal cell layer of skin (aka stratum basale or germinativum) is the lowermost sublayer of epidermis. This layer of basal cells is made up of one row of constantly dividing columnar or cubical undifferentiated keratinocytes.

This region is separated from the lower dermis by basement membrane and is attached to the basement membrane through hemidesmosomes.

Structure of basal cell layer

Stratum basale is usually one keratinocyte deep with melanocytes and Langerhans or immune cells dispersed in between. These melanocytes synthesize melanin pigment, giving color and hue to the skin and the hair. The amount of melanin produced though predetermined genetically, is affected by sun exposure levels leading to increase or decrease in production. The Merkel nerve endings (neuroectodermal origin) which have tactile or touch sensation function are also dispersed in this germinativum epidermis. As this basal stratum is in close contact with dermis, it is nurtured with oxygen and nutrients by dermis by diffusion process.

Functions of basal cell layer

Basal cell (stratum basale)
layers in epidermal skin

High degree of mitosis or cell proliferation activity is found in this basal region and hence the name 'germinativum' (germinating). This cuboid keratinocyte divides into two daughter keratinocytes and the upper keratinocyte migrates towards outer epidermal layers undergoing progressive transformation called keratinisation. After moving into stratum spinosum, these keratinocytes change shape and become polygonal and start synthesizing keratin. Keratinocytes produce more and more keratin and eventually undergo programmed death (apoptosis). In humans, it is estimated that basal stratum turnover from epidermal proliferation units to desquamation every 40–56 days.

The lower basal daughter keratinocyte remains in the stratum basale and undergoes growth and maturation for the next mitosis. As the stratum cornium is continuously sloughed off, the mitosis and replacement activity at basal region should continuously go on. The proliferation and differentiation of basal epidermal region is regulated by Vitamin D3 (cholecalciferol).

Any chemical, physical, physiological, radiological or pathgenic disturbance of this cell proliferation activity at basal germinativum brings about dermal ailments.

Related topics:

1. Function of the stratum corneum.
2. Dermis layers - Structure of dermis.
3. Papillary dermis.
4. Reticular dermis.
5. Function of hypodermis.

Interesting topics:

1. Skin sensitive to touch.
2. Different type of facial skin.
3. Main functions of human skin.
4. Know your skin.
5. Nourishing skin with fruits and vegetables.
6. Small itchy water blisters on hands and feet.
7. Cosmetic laser treatments - Types of cosmetic lasers.
8. What are salmon patches? - Nevus simplex birthmarks on babies.
9. What is a hemangioma? - What are the causes of hemangioma?
10. Hemangioma treatments - Hemangioma removal.

Reference:
Harding, C. R. (2004), The stratum corneum: structure and function in health and disease. Dermatologic Therapy, 17: 6–15. doi: 10.1111/j.1396-0296.2004.04S1001.x
Image source:
http://en.wikipedia.org/wiki/File:Epidermal_layers.png
Author:Mikael Häggström, based on work by Wbensmith
License: CC BY-SA 3.0
Current topic: Basal layer cells of epidermal skin.

Dermis layers - Structure of dermis

Home > Structure of dermis layer

Dermis layer is one of two structural layers of skin. It is located below the epidermis of the skin.

The Dermis, in turn, is made up of upper papillary and lower reticular layers. The structure of this area of skin is made up of a gelatinous ground substance (extrafibrillar and extracellular matrix) containing elastic fibers (yellow fibers), reticular fibers, glycosaminoglycans and collagen. These structures give dermis tensile strength.

Adipocytes (fat cells), fibroblasts, leucocytes and nerve cells are the major types of tissue components found in this region. Depending upon its location on the body, the thickness varies. It is thinnest on the eye lids and thickest on the back. The structure of dermis can also be divided as per its functional tissue components.

Connective tissue
Dense irregular connective tissue, comprising rows of fibroblasts (fiber forming cells) crowded between collagen and elastin fibers, is arranged in sheets in lower region and the upper region is made up of loose connective tissue.

Fat deposits
Fat deposits are found in this region. The thickness of the fat deposits vary in genders and men and women have different areas of fat concentration. Numerous adipocytes (fat cells) are present in groups known as fat lobules.

Vascular tissue
There is a network of blood vessels mainly comprising arterioles, venules and capillaries in this layer.
Extensive network of lymphtic vessels are present in dermis supplyin protective immune cells.

Appendages
Hair follicles are present in this region and are present throughout the body except lips, palms and soles.

Glands
Eccrine glands (sweat glands) are present in the dermis and are dispersed throughout skin regions. Apocrine glands (scent glands) are present in axilla and anogenital regions of dermis. Sebaceous glands (sebum or oil glands) are found in dermis.

Muscles

Structure of dermis layer

Smooth muscle structure like Arrector pili muscle is found attached to the base of hair follicle.

Sense organs
There is sensory as well as autonomic nerve network dispersed throughout dermis making skin sensitive to touch and other stimuli. Meissner's corpuscles (touch receptors), Pacinian corpuscles(pressure and vibration receptors), free nerve endings (itch, pain and temperature receptors) and nerve fibers are present.

Immune system
Leukocytes (white blood cells) like neutrophils, monocytes, macrophages, mast cells and T-lymphocytes are present here.

Related topics:

1. Papillary layer.
2. Reticular layer.
3. Function of hypodermis layer.
4. Different type of facial skin.
5. Major functions of skin.

Interesting topics in dynamic skin care:

1. Know the structure and function of your skin.
2. Nourishing skin with fruits and vegetables.
3. Small itchy water blisters on hands and feet.
4. Cosmetic procedures with lasers.
5. Nevus simplex - Salmon patches.
6. What is hemangioma?
7. Hemangioma removal.
8. Carotene in carrots.
9. Types of urticaria.
10. Chronic urticaria.

Current topic in skin care: Structure of dermis layer

Dermis - Papillary layer of dermis

Home > Dermis > Papillary layer of dermis

In dermis, papillary layer lies superficial to the reticular layer. Papillary region lying below the epidermis is closely connecting with it.

It is made up of finger-like (nipple-like) projections, extending into the epidermis. This type of structure strengthens the bond between the skin layers by greatly increasing the surface contact area between these regions.

Papillary region is composed of areolar tissue, the most common type of 'loose connective tissue'. This layer is approximately 300-400 µm deep. It is much thinner when compared to reticular region. Though it is strong enough to bind the skin, it is soft enough to give cushioning and flexibility. It exhibits significant empty space with loosely organised fibers which are interlacing.

Papillary dermis

Papillary region is dispersed with abundant blood capillaries. Epidermis is avascular (lacking blood vessels). The vasculature of this region supports the epidermis with the supply of nutrients and oxygen for the epidermal cell growth as well as with removal of metabolic wastes. With the unique arrangement for increasing or decreasing the blood flow, thermo-regulatory function of conserving or dissipating body heat is performed by this papillary structure.

The friction ridges (fingerprints) in the palms and fingers and also in the soles and toes are due to the papillary ridges. Apart from giving us grasp, these ridges, with their pattern being controlled genetically, are unique to individuals and provide fingerprints for identity.

Meissner's corpuscles (touch receptors) present in this region in sensitive areas make skin sensitive to touch. One of the important role of papillary layer of dermis is in formation hair, its growth and cycling.

Related topics in dynamic skin care:

1. Reticular region of skin.
2. Function of hypodermis layer.
3. Know your skin
4. Different type of facial skin.
5. Major functions of skin.

Interesting topics in dynamic skin care:

1. Nourishing skin with fruits and vegetables.
2. Small itchy water blisters on hands and feet.
3. Cosmetic procedures with lasers.
4. Nevus simplex - Salmon patches.
5. What is hemangioma?
6. Hemangioma removal.
7. Carotene in carrots.
8. Types of urticaria.
9. Chronic urticaria.

Image source: http://en.wikipedia.org/wiki/File:Normal_Epidermis_and_Dermis_with_Intradermal_Nevus_10x.JPG
Author: Kilbad
License: public domain
Current topic in dynamic skin care: Papillary dermis layer.

Dermis - Reticular layer of dermis

Home > Know your skin > Dermis > Reticular layer of dermis

In dermis, reticular layer lies below the papillary layer. Reticular dermis is the deepest part of the skin and lies superficial to the hypodermis.

Reticular region, ranging from 1-3mm in thickness, is much denser and thicker than the papillary region.

Dense irregular connective tissue and adipose tissue are the  major constituents of this region. Fibroblasts (fiber producing cells) and adipocytes (fat cells) abound this reticular region. It has densely packed thick collagen fibers, elastic fibers and reticular (netlike) fibers giving skin structural and tensile strength, elasticity and extensibility. These fibers are arranged in parallel to the surface of the skin. The reticular fibers (reticulin), made of Type III collagen, weave throughout reticular layer giving a net-like appearance and hence the name.

Most of the important epithelial glandular structures of skin like eccrine (sweat) glands, apocrine (scent) glands and Sebaceous (oil) glands are located here.

Blood and lymphatic vessels are found traversing this region carrying nutrients, oxygen and immune cells. The deeper vasculature to the skin, the deep cutaneous plexus, are located at the junction of reticular region and hypodermis.

Dermis - Reticular layer

The hair folicles and nails are located in the reticular layer. The 'arrectores pilorum' muscles are located here attached to individual hair follicle. They are responsible for  piloerection and produce goose bumps or cutis anserina. They are innervated by the sympathetic branch of the autonomic nervous system.

Nervous tissues and receptors are located in this area transmitting sensations like pain, cold and heat and make skin sensitive to touch. Special nerve cells like Meissner's, Vater-Pacini and Pacinian corpuscles are found here. They are responsible for transmitting the sensations of touch and pressure.

The criss-crossing collagen fibers form Langer's lines, also called as cleavage lines. They correspond to the natural orientation of collagen fibers. Surgical incisions made parallel to Langer's lines may heal better, faster and produce less scarring than those cutting across the fibers. Any damage to reticular layer of dermis can cause scarring.

Related topics in dynamic skin care:

1. Function of hypodermis layer.
2. Know your skin
3. Different type of facial skin.
4. Major functions of skin.

Interesting topics in dynamic skin care:

1. Nourishing skin with fruits and vegetables.
2. Small itchy water blisters on hands and feet.
3. Cosmetic procedures with lasers.
4. Nevus simplex - Salmon patches.
5. What is hemangioma?
6. Hemangioma removal.
7. Carotene in carrots.
8. Types of urticaria.
9. Chronic urticaria.

Image source: http://en.wikipedia.org/wiki/File:Normal_Epidermis_and_Dermis_with_Intradermal_Nevus_10x.JPG
Author: Kilbad
License: public domain
Current topic in dynamic skin care: Reticular dermis layer.