Skin Physiology

Anatomical and morphological features

The skin of a newborn is characterized by exceptional thinness, delicacy, and the presence of a very dense capillary network. One of the key structural features is the weak adhesion between the epidermis and the dermis. This specific anatomical feature explains the high vulnerability of the skin: minimal mechanical impact or friction easily leads to the formation of blisters and erosions, along with a pronounced tendency toward maceration and trauma.

Despite its softness, the skin performs a crucial barrier-adaptive function. It protects the internal environment of the body from mechanical damage and helps adapt to new external factors after birth. In addition, rich innervation makes the skin the infant's primary sensory organ through which they perceive the surrounding world.

Functional specifics and immune defense

At an early age, skin physiology differs radically from that of adults. The respiratory and resorption (absorptive) functions come to the fore, prevailing over the others. At the same time, the barrier (protective) function and mechanisms of thermoregulation are extremely poorly developed.

Infants have a high susceptibility to infectious agents. This is due to a combination of factors:

• Immaturity of local defense factors of the skin and mucous membranes.
• High blood glucocorticoid levels caused by the body's stress response to birth (hormones exert an immunosuppressive effect).
• Presence of transitional dysbiocenosis on the surface of the skin.
• Dominance of protein catabolism (breakdown) over anabolism (synthesis).

Glandular apparatus and skin appendages

The functioning of skin glands at birth has pronounced specific features:

1. Sweat glands are anatomically present, but their functional activity during this period is extremely low.
2. Sebaceous glands, by contrast, are large at birth and actively secrete. Nevertheless, in the very first weeks of life, they undergo rapid involution (decrease in size and reduction in activity).

The infant's hair is represented by specific vellus hairs — lanugo. Their main distinctive feature is the complete absence of the medulla (core).

Vernix caseosa and care guidelines

At the moment of birth, the child's body is covered with vernix caseosa (vernix caseosa). This substance provides a critically important protective function, which is a direct continuation of the intrauterine protection of the fetus.

For this reason, current clinical guidelines strongly do not recommend routine bathing of the newborn in the first 24 hours after birth. If meconium or blood is present on the skin, these contaminants should be extremely gently washed off with warm tap water, taking care not to damage the protective layer of vernix caseosa.

Transitional changes and thermoregulation

In the early neonatal period, the skin undergoes a number of transitional (borderline) changes. These are completely physiological states that reflect the process of adaptation of the organism to extrauterine life. They do not require medical intervention and resolve on their own.

Hypothermic features deserve special attention. Due to the small thickness of the skin, abundant vascularization (dense capillary network), and a small amount of heat-insulating subcutaneous adipose tissue, the newborn is extremely prone to rapid heat loss. This requires careful control of the ambient temperature regime.

Class and exam questions

What else to study on this topic

• Mechanisms of development of transitional (borderline) skin changes
• Impact of birth stress and glucocorticoids on newborn immunity
• Physiology of thermoregulation and causes of hypothermic states in children
• Composition and barrier properties of vernix caseosa
• Causes of protein catabolism dominance over anabolism in the neonatal period

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.