Читать книгу Pathy's Principles and Practice of Geriatric Medicine - Группа авторов - Страница 80

The stratum corneum, which is responsible for the barrier function of the epidermis, remains the same thickness with age. Keratinocytes are the primary cell type in the epidermis. Their turnover rate decreases, and as a result, wound healing takes longer in elderly people. Slow keratinocyte renewal leads to increased fragility of the epidermis and increased susceptibility to physical and chemical damage. Melanocytes, the cells responsible for pigmentation, decrease and regenerate more slowly, leading to dark age spots. Langerhans cells are responsible for the immune defence of the epidermis against carcinogenesis and infections. They also decrease with age, resulting in an increase in skin tumours and infections.⁹⁸ Vitamin D production also takes place in the epidermis. Elderly people tend to avoid sun compared to young adults, and vitamin D precursors are reduced in their epidermis. Thus, the production rate of vitamin D decreases with age.

The skin dermis loses its thickness with age. A decrease in collagen production and loss of fat cells contribute to the lessening of the dermis. Clinically, while the dermis becomes thinner due to these mechanisms, the skin appears wrinkled and sagging. Collagen and fatty tissue are responsible for the skin’s endurance against physical damage. As these are lost in the dermis with age, the skin becomes more fragile and is easily damaged or torn as the result of even minor physical insults. Sebum production from the sebaceous glands decreases with age, along with dermis vascularization and the number of sweat glands. These mechanisms cause the skin to seem dry and rough. Dermis vascularization and sweating from sweat glands are major actors for balancing body temperature and losing heat from the skin.⁹⁹ Since both mechanisms are impaired with age, elderly people tend to experience hyperthermia in hot weather. The opposite is also true: vasoconstriction of dermis arterioles and shivering are also impaired with age, resulting in undesired heat loss from the skin in cold weather.

Subcutaneous atrophy of fatty tissue changes the facial expression in the elderly. The cheeks become thinner, periorbital fatty tissue lessens, and cartilage such as that in the nose and ears seems to be enlarged. Subcutaneous fatty tissue increases in the abdomen.¹⁰⁰ Hair loss and greying hair, which have a genetic basis inherited from previous generations, cause an undesired appearance. Hair in the ears and nostrils and near the lips grows with age, and nails become harder, thicker, and yellowish. Toenails may become hard to cut, causing irregular growth and infections.