Ch 18: Skin & Q Bank Flashcards
Introduction:
Integument, which is the covering of the top skin also is called the cutaneous layer. It is composed of the epidermis, an _epithelial laye_r of ectodermal origin, and the dermis, a layer of mesodermal connective tissue.
At the irregular junction between the dermis and epidermis, projections called dermal papillae interdigitate with invaginating epidermal ridges to strengthen adhesion of the two layers.
Beneath the dermis lies the subcutaneous tissue or hypodermis.
is a loose connective tissue layer usually containing pads of adipocytes. The subcutaneous tissue binds the skin loosely to the underlying tissues and corresponds to the superficial fascia of gross anatomy.
The specific functions of the skin fall into several broad categories.
Protective: It provides a physical barrier against thermal and mechanical insults such as friction and against most potential pathogens and other material. Microorganisms that do penetrate skin alert resident lymphocytes and antigen-presenting cells (APCs) in skin and an immune response is mounted. The dark pigment melanin in the epidermis protects cell nuclei from ultraviolet (UV) radiation. Skin is also a permeability barrier against excessive loss or uptake of water, which has allowed for terrestrial life. Skin’s selective permeability allows some lipophilic drugs such as certain steroid hormones and medications to be administered via skin patches.
The specific functions of the skin fall into several broad categories.
Sensory: Many types of sensory receptors allow skin to constantly monitor the environment, and various skin mechanoreceptors help regulate the body’s interactions with physical objects.
The specific functions of the skin fall into several broad categories.
Thermoregulatory: A constant body temperature is normally easily maintained thanks to the skin’s insulating components (eg, the fatty layer and hair on the head) and its mechanisms for accelerating heat loss (sweat production and a dense superficial microvasculature).
The specific functions of the skin fall into several broad categories.
Sexual signaling: Many features of skin, such as pigmentation and hair, are visual indicators of health involved in attraction between the sexes in all vertebrate species, including humans. The effects of sex pheromones produced by the apocrine sweat glands and other skin glands are also important for this attraction.
The dermal-epidermal interdigitations are of the peg-and-socket variety in most skin, but they occur as well-formed ridges and grooves in the thick skin of the palms and soles, which is more subject to friction. These ridges and the intervening sulci form distinctive patterns unique for each individual, appearing as combinations of loops, arches, and whorls, called dermatoglyphs, also known as fingerprints and footprints.
Skin can renw for life.
The epidermis forms the major distinction between thick skin, found on the palms and soles, and thin skin found elsewhere on the body.
75 to 150 μm for thin skin and from 400 to 1400 μm (1.4 mm) for thick skin.
Like all epithelia, the stratified squamous epidermis lacks microvasculature, its cells receiving nutrients and O2 by diffusion from the dermis.
The dermis of thin skin is more cellular and well vascularized than that of thick skin, with elastin and less coarse bundles of collagen.
From the dermis, the epidermis consists of four layers of keratinocytes (or five layers in thick skin,
The basal layer (stratum basale) is a single layer of basophilic cuboidal or columnar cells on the basement membrane at the dermal-epidermal junction
