Anatomy and Physiology of The Mammalian Skin ; Epidermis, Dermis, Hypodermis, Subcutis

Описание: The mammalian skin is a complex organ with multiple layers and structures, serving as a protective barrier while supporting vital physiological functions. It is composed of three main layers: the epidermis, dermis, and hypodermis (subcutis). Here’s an overview:

1. Epidermis
Description: The outermost layer of the skin, primarily composed of keratinized epithelial cells.

Structure:

Stratum Corneum: The outermost layer, consisting of dead, flattened keratinized cells that provide a tough, protective barrier.

Stratum Lucidum (only in thick skin): A translucent layer found in areas like the palms and soles.

Stratum Granulosum: Contains keratohyalin granules essential for keratin formation.

Stratum Spinosum: Provides strength and flexibility; contains desmosomes that link cells.

Stratum Basale (or Germinativum): The basal layer where mitosis occurs, producing new keratinocytes. It also contains melanocytes (responsible for pigment) and Merkel cells (touch receptors).

Functions:

Acts as a barrier to protect against pathogens, UV radiation, and water loss.

Produces melanin to safeguard deeper layers from UV damage.

2. Dermis
Description: The middle layer, located beneath the epidermis, rich in connective tissue, blood vessels, and nerves.

Structure:

Papillary Layer: The upper layer of loose connective tissue with capillaries, nerve endings, and dermal papillae, which form fingerprints.

Reticular Layer: The deeper, denser connective tissue containing collagen and elastin fibers for strength and elasticity.

Contents:

Blood vessels: For oxygen and nutrient delivery.

Nerve endings: For sensory perception (touch, pressure, pain, and temperature).

Sweat glands, sebaceous glands, and hair follicles originate here.

Functions:

Supports the epidermis and provides nutrients.

Regulates body temperature through sweat glands and blood flow.

Senses external stimuli.

3. Hypodermis (Subcutis)
Description: The deepest layer of skin, consisting primarily of adipose (fat) tissue and connective tissue.

Structure:

Composed of fat cells (adipocytes) interspersed with connective tissue, nerves, and larger blood vessels.

Functions:

Provides insulation to conserve body heat.

Acts as a cushion to protect underlying muscles, bones, and organs from trauma.

Stores energy in the form of lipids.

Summary of Functions:
Protection: The skin acts as a physical and immunological barrier.

Sensation: Contains specialized receptors to detect pressure, temperature, pain, and touch.

Thermoregulation: Maintains body temperature through sweat glands and blood vessel regulation.

Metabolic Functions: Produces vitamin D through UV exposure and stores fat as an energy reserve.

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