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Arocha Anatomy & Physiology Skin Unit Playlist: Interactive 3D Models

Epidermis Skin Layers

The epidermis is the outermost layer of skin and is primarily comprised of keratinocytes—cells that produce the protein keratin. Keratinocytes form the skin’s protective barrier and are constantly reproducing to replace old or damaged cells. As keratinocytes replicate, they are pushed toward the skin’s surface. The epidermis is subdivided into 5 layers, or strata, which represent progressive stages of differentiation from deeper to more superficial layers. 

  • The stratum corneum varies in thickness throughout the body—it’s thickest on the soles of the feet and thinnest around the eyes. The stratum corneum is the outermost layer of the epidermis. It is comprised of dead keratinocytes. Because of its constant contact with the outside world, this layer is continuously sloughed off and replaced by new cells.
  • The stratum lucidum is layers of flattened clear, dead keratinocytes that contain large amounts of keratin. This layer is found only in the areas of the body where exposure to friction is greatest (fingertips, palms, soles of feet). (not represented in the 3D model)
  • The stratum granulosum is the granular layer of the epidermis. Here, the keratinocytes lose their nuclei and contain pigment-filled granules in their cytoplasm. Keratinocytes in the stratum granulosum also begin the production of keratin, which will eventually fill the entire cell. 
  • The stratum spinosum is the “spiny” or “prickly” layer of the epidermis and rests on top of the stratum basale. In this layer, keratinocytes are connected to each other by thin, spiny projections within the intercellular space. Specific immune cells, called Langerhans cells, are also present in the stratum spinosum. These cells help detect invading pathogens and initiate an immune response. 
  • The stratum basale is the innermost layer of epidermis that sits on top of the basement membrane. This layer contains small, rounded cells called basal cells, which are the precursor to keratinocytes. These cells continuously divide, pushing older cells into outer epidermal layers as new cells are produced. The stratum basale also houses melanocytes—the pigment-producing cells that give skin its color. 

Skin Tissue

Skin is the body’s largest organ. It comprises three layers—the epidermis, dermis, and hypodermis— and acts as a protective barrier between internal structures and the outside world. 

  • Skin regulates our internal temperature, repels water, synthesizes vitamin D, and registers tactile sensations such as heat, pain, pressure, and vibrations from the environment. Skin is also an immune organ that physically blocks and biochemically detects invading bacteria and toxins.
  • The epidermis is the outermost layer of skin and is primarily comprised of keratinocytes—cells that produce the protein keratin. Keratinocytes form the skin’s protective barrier and are constantly reproducing to replace old or damaged cells. 
  • The dermis is the skin’s thickest layer. It is filled with a matrix of collagen and elastin proteins that provide support, flexibility, and resilience, as well as several functional structures, such as mechanoreceptors, that enable interaction with the outside world. The dermis contains nerve endings, sudoriferous (sweat) glands, sebaceous (oil) glands, hair follicles, blood vessels, and lymphatics.
  • Also referred to as the subcutaneous layer, the hypodermis is a layer of fat and connective tissue below the dermis. This layer helps insulate and protect the internal organs, and also stores fat for future use. The hypodermis can vary in thickness throughout the body, and between individuals.

Epidermis Skin Layers 3D Model

Click model to interact. Click black, round "button" to open tool menu.

 

 
 
 

Skin Tissue 3D Model

Click model to interact. Click black, round "button" to open tool menu.