Systems Biology
In this content, we learn about the unique anatomy of our largest single organ, the skin. There are three layers of the skin: the epidermis, the dermis, and the hypodermis, also known as the subcutaneous layer. The epidermis, being the outermost skin layer, protects us from infection, damage, and water loss. The majority of cells in the skin are keratinocytes, which produce an important structural protein known as keratin. Keratin is insoluble in water and protects epithelial cells from damage or stress. It is also found in hair and fingernails. For protection against UV radiation, melanin comes into play, a pigment produced by melanocytes located in the stratum basale.
The dermis, as the middle layer, is where a majority of skin functions occur, housing sweat glands, oil glands, blood vessels, hair follicles, arrector pili muscles, and sensory receptors. The hypodermis, although technically not part of the skin, is a layer of tissue below the dermis that connects it to the underlying bone and muscle tissue. It's filled with adipose tissue to insulate and fibrous tissue to maintain the skin's shape.
Lesson Outline
<body> <ul> <li>Introduction</li> <ul> <li>The skin is our largest single organ</li> <li>Three layers of the skin <ul> <li>Epidermis</li> <li>Dermis</li> <li>Hypodermis (subcutaneous layer)</li> </ul> </li> </ul> <li>Key structures of the skin</li> <ul> <li>Epidermis <ul> <li>Protects from infection, damage, and water loss</li> <ul> <li>Stratum basale: deepest layer of the epidermis and is composed of live, dividing cells</li> <li>Stratum corneum: most superficial layer of the epidermis and is composed of dead cells</li> </ul> </ul> </li> <li>Most cells of the skin are keratinocytes <ul> <li>Structural protein, protects epithelial cells</li> <li>Main component of skin, hair and fingernails</li> </ul> </li> <li>Melanocytes and melanin <ul> <li>UV radiation protection (absorbs radiation and dissipates as heat)</li> <li>Melanocytes produce melanin; have base rates of melanin synthesis but can be activated by sun exposure</li> </ul> </li> </ul> <li>Dermis</li> <ul> <li>Contains sweat glands, oil glands, blood vessels, hair follicles</li> <li>Arrector pili muscles: tiny smooth muscles that connect hair follicles to connective tissue in the dermis</li> <li>Sensory receptors, to react to temperature, pressure, pain, vibration</li> </ul> <li>Hypodermis</li> <ul> <li>Layer of tissue beneath the dermis</li> <li>Composed of adipose and fibrous tissue; connects skin to underlying bone and muscle</li> </ul> </ul>
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FAQs
The skin consists of three main layers, namely the epidermis, dermis, and hypodermis. The epidermis is the outer layer that provides a protective barrier against harmful substances and microorganisms. The dermis is the middle layer containing blood vessels, nerves, sweat glands, and hair follicles, responsible for regulating temperature, providing nutrients to the skin, and sensation. The hypodermis is the innermost layer, composed of fat and connective tissue, and serves as an insulation, shock absorption, and energy storage unit.
The epidermis is divided into several sublayers, including the stratum basale and the stratum corneum. The stratum basale is the innermost layer comprising a single layer of column-shaped cells, responsible for producing new skin cells through continuous cell division. These new cells migrate towards the surface and differentiate into various types of keratinocytes. The stratum corneum is the outermost layer of the epidermis, acting as a physical and water-resistant barrier. It is composed of dead, flattened keratinocytes filled with keratin, which prevent water loss and protect the body from harmful external substances.
Keratin and melanin play essential roles in skin anatomy. Keratin, a structural protein, provides strength, elasticity, and water-resistance to the skin. It is found in the outer layers of the epidermis and forms a protective barrier. Melanin, on the other hand, is a pigment responsible for the color of our skin, hair, and eyes. Melanin is produced by specialized cells called melanocytes located in the epidermis. It protects the skin from harmful ultraviolet (UV) radiation by absorbing and dissipating it as heat.
Sweat glands are essential components of the skin anatomy found in the dermis layer. There are two types of sweat glands – eccrine glands and apocrine glands. Eccrine glands are found all over the body and produce sweat consisting of water, salt, and waste products. Their primary function is to regulate body temperature by secreting sweat onto the skin surface, which then evaporates to cool the body. Apocrine glands, located mainly in the armpits and groin, produce a viscous sweat that, when broken down by bacteria on the skin, causes body odor. They play a role in temperature regulation, but they may also have pheromone-related functions.
Sensory receptors in the skin are specialized nerve endings that detect and respond to various stimuli, such as temperature, pressure, pain, and vibration. These receptors are primarily located in the dermis and relay the information they receive to the nervous system, enabling the body to respond and adapt to external conditions. Sensory receptors play a critical role in the skin's function by providing various sensations, such as touch, pain, and temperature, which help prevent injury, maintain comfort, and promote overall well-being by enabling appropriate responses to external stimuli.
