Cutaneous - Histology

What is Cutaneous Tissue?

Cutaneous tissue, commonly referred to as the skin, is the largest organ of the human body. It serves as a protective barrier against environmental hazards, helps regulate body temperature, and provides sensory information. The skin is composed of three primary layers: the epidermis, the dermis, and the subcutaneous tissue (also known as the hypodermis).

What are the Layers of the Epidermis?

The epidermis is the outermost layer of the skin, made up of stratified squamous epithelium. It consists of five distinct layers:

Stratum basale: The deepest layer, containing stem cells that divide to form new keratinocytes.
Stratum spinosum: Known for its spiny appearance under a microscope, this layer provides strength and flexibility to the skin.
Stratum granulosum: This layer contains granules rich in lipids, which help form a waterproof barrier.
Stratum lucidum: Found only in thick skin like the palms and soles, it provides an additional layer of protection.
Stratum corneum: The outermost layer, composed of dead keratinized cells that are shed regularly.

What is the Dermis Composed of?

The dermis lies beneath the epidermis and is much thicker. It is divided into two regions:

Papillary layer: This upper layer contains loose connective tissue and is named for its finger-like projections called dermal papillae. These interlock with the epidermis to provide support and increase surface area for nutrient exchange.
Reticular layer: The deeper layer, composed of dense irregular connective tissue, providing strength and elasticity to the skin.

The dermis is rich in blood vessels, nerve endings, hair follicles, and glands, including sweat glands and sebaceous glands.

What is the Function of Subcutaneous Tissue?

The subcutaneous tissue (hypodermis) is the deepest layer of the skin. It is composed mainly of adipose tissue and connective tissue. This layer acts as an insulator to conserve body heat and as a shock absorber to protect underlying muscles and bones. It also serves as a storage site for fat, providing energy reserves.

What is the Role of Melanocytes?

Melanocytes are specialized cells located in the stratum basale of the epidermis. They produce melanin, the pigment responsible for skin color. Melanin protects the skin from the harmful effects of ultraviolet (UV) radiation by absorbing and dissipating the radiation.

What are Langerhans Cells?

Langerhans cells are immune cells found in the epidermis. They are part of the body's defense system, capturing and presenting antigens to T-cells, which helps initiate an immune response. These cells play a crucial role in skin immunity and in the detection of pathogens.

What are Merkel Cells?

Merkel cells are located in the stratum basale and are associated with nerve endings. They function as mechanoreceptors, which are responsible for the sensation of light touch. These cells contribute to the sensory capabilities of the skin.

What is the Importance of Hair Follicles and Glands?

Hair follicles are structures in the dermis from which hair grows. They are surrounded by sebaceous glands that secrete sebum, an oily substance that lubricates the hair and skin. Sweat glands, also found in the dermis, play a key role in thermoregulation by producing sweat that evaporates to cool the body.