What are the layers of the skin's epidermis?

The skin is an important barrier of the human body. Although it looks fragile, it can effectively resist some viruses and bacteria that invade the human body. At the same time, the skin not only protects the internal body, but also plays an important role in regulating human respiratory function and maintaining body surface temperature. But human skin is far more than the layer visible to the naked eye, so what are the main layers of human skin?

The skin is divided into two layers: the epidermis and the dermis. The epidermis is on the surface of the skin and can be divided into two parts: the stratum corneum and the stratum germinativum. The keratinized cells make up the stratum corneum, which becomes dandruff after falling off. The cells of the germinal layer continue to divide and can replenish the shed stratum corneum.

The germinal layer contains melanocytes, which produce melanin that can prevent ultraviolet rays from damaging internal tissues. The epidermis is a stratified squamous epithelium, while the dermis is a dense connective tissue with many elastic fibers and collagen fibers, so it is elastic and tough.

Respiration: Wrapping your body with plastic wrap will make you feel stuffy, because the skin's breathing is blocked. But the breathing volume is only 5% of the lung breathing volume.

Thermoregulation: Skin is a strange substance: it allows air to pass through but does not conduct heat well. When the outside temperature changes, the skin is the first to respond, regulating blood circulation and sweating to keep the body temperature constant. This is also the function of the skin.

Sensing: The skin is also the body's sensor, and its layers are covered with countless sensory nerves. Able to quickly sense various stimuli from outside the body, including cold, touch, pain, pressure, and sensation. When the sensory nerves sense these stimuli, they will be transmitted to the brain, which will quickly become alert and issue orders to direct the body's organs to stay away from danger.

Metabolism: The skin's renewal cycle is 28 days, but due to current environmental pollution and aging, the skin's renewal cycle will also be extended.

Absorption: The skin has good absorption function, but its absorption is not as simple as imagined. Because it is an absorber with a "filter", only those special molecules that have been processed can pass through the skin's pores and reach the deep layers of the skin, thereby promoting skin absorption. Cosmetics are made using this property.

Secretion and excretion function: The human body has two sets of water excretion systems, one is the excretion system, namely the kidney excretion system; the other is the skin. It removes excess urea, ammonia, fat, iodine, bromine, arsenic, mercury and other substances from the body by secreting sweat and sebum, thereby assisting the kidney's excretion function.

Protective function: It covers every corner of the body and protects the internal organs and other organs of the body. At the same time, the stratum corneum of the skin, which contains a little oil, also has the function of preventing bacterial invasion and bacterial reproduction. The skin also has a refracting effect on light or UV rays to prevent it from damaging deeper layers of the skin. People also say that "skin is the body's first line of defense."