[Biology Class Notes] on Difference Between Epidermis and Dermis Pdf

Tissue Type of Epidermis and Dermis

Epidermis and dermis are the layers of the human skin. It is the body’s largest organ and plays a crucial role in the overall health and well-being of the body. Skin acts as a barricade between the internal environment and the external environment of the body. The outermost care of the skin is essential. It is necessary to understand the different structures and functions of each layer of skin for taking good care of the skin. The skin surface is made up of different tiers and divided into three main layers: epidermis, dermis, and hypodermis. Let us learn in-depth what epidermis and dermis, the two most important layers of the skin is.

What is Epidermis?

The epidermis is the topmost layer of the skin. It is around 0.05 to 1.5 mm thick. The epidermis is made up of several cells. Keratinocytes cells are found abundantly in the epidermis layer of the skin. Another type of cell is melanocytes that are produced by the corns of the colour. The substance melanin provides the tone to the skin. The third type of cell found in this layer is Langerhans; these cells interact with the white blood cells and act as the immune defense.

(Image to be added soon)

Layer of Epidermis

Let us also discuss the deepest to the most superficial layer of the epidermis.

1. Stratum Basale

It is the deepest layer of the skin where mitosis occurs. It is the process where cells divide, making new epidermal skin cells. After the division of mitotic the cell undergoes keratinization, a process of progressive cell maturation and migrating to the surface of the skin. 

2. Stratum Spinosum

The cells generating from stratum basale accumulates quickly in this layer through desmosomes (structure joining adjacent cells together)

3. Stratum Granulosum

As the cells mature and undergo keratinization, it accumulates in this layer and gathers dense granules of basophilic keratohyalin. 

4. Stratum lucidum

Depending on the frictional forces, this layer varies throughout the body. Stratum lucidum, in its thickest form, is found on the palms of the hands and soles of the feet. 

5. Stratum corneum

The layer contains dead and dying cells that are full of mature keratin as it is the outermost layer of the epidermis. The cells change the substance and break the complex chemicals within the cells that causes their death.

What is Dermis?

After the topmost layer, the next middle layer of the skin is the dermis. It is around 0.3 to 3.0 mm thick. This layer consists of connective tissues. The layer consists of some essential components like firmer protein collagen and the fibres of elastic protein. Moreover, this layer contains various immune cells and factors that protect the skin.

(Image to be added soon)

Layer of Dermis

There are only two layers of the dermis, and those are as follows:

1. Papillary Dermis

The layer consists of areolar connective tissues, dermal papillae that enhances the surface area of the layer, and ridges that extend into the epidermis and dermal papillae. The ridges are responsible for the fingerprints on objects when touched. 

2. Reticular Dermis

The layer consists of dense connective tissues that contain interlacing bundles of elastic fibres and collagen. In between these fibres, there are small quantities of hair follicles, adipose tissue oil glands, nerves, and sweat gland ducts.

Difference Between Epidermis and Dermis

Let us learn the difference between epidermis and dermis based on specific characteristics.

1. Blood Vessels

Epidermis – The epidermis layer does not contain blood vessels. The oxygen and nourishment they get are from the deeper layers.

Dermis – Dermis layer has a thin network of blood vessels known as capillaries; they are densely located under the epidermis. 

2. Nerves 

Epidermis – This layer does not contain nerves.

Dermis – It contains nerves that conduct nerve impulses through the central nervous system towards the brain. The open nerve endings of this layer originate the sense of pain. 

3. Functions

Here are some of the functions of the epidermis layer

1. It is a barrier between the internal structure and the external environment of the body.

2. It does not allow the entrance of microorganisms, water, and other substances.

3. It protects the internal atmosphere of skin from UV rays of the sun and other pollutants.

Functions of The Dermis Layer

1. It gives skin strength, extensibility, elasticity, and firmness.

2. Helps provide nutrients and oxygen to the outer layer of the skin

3. Has antibodies that fight hazardous substances and microbes

4. The layer initiates the process of inflammation during skin injury to increase the blood in the bloodstream. It makes the immune cells navigate conveniently to fight microorganisms.