Morphological composition of the skin
Histologically, the skin structure comprises main tissue layers, as well as a complex of glands and appendages.
1. Main layers
- Epidermis. The most superficial region. It is represented by stratified keratinizing squamous epithelium.
- Dermis. The connective tissue foundation located directly beneath the epithelium.
Note: Subcutaneous adipose tissue (hypodermis) lies beneath the dermis. Although anatomically closely related to the skin, histologically it is a separate structure.
2. Glandular apparatus
- Sweat glands.
- Sebaceous glands.
- Mammary glands. Developmentally, they are modified sweat glands.
3. Skin appendages These include keratinized structures: hair and nails.
Barrier and protective function
This is the primary function of the integument, essential for maintaining the constancy of the internal environment (homeostasis).
- Isolation. The skin maintains the unique chemical composition of the body. Intercellular tight junctions in the epithelium prevent the leakage of substances. In addition, the stratum corneum along with sebum forms a water-repellent hydrophobic film. This is why topical medicinal products are formulated on a hydrophobic base (ointments, oil-based creams).
- Mechanical and physical protection. Integumentary tissues are resistant to pressure and tearing. The pigment melanin contained in the cells absorbs ultraviolet radiation, protecting deeper structures.
- Biological and chemical barrier. A healthy epidermis is impermeable to bacteria and toxins. Sebum acidifies the environment (pH 4.2–5.6), which is detrimental to many microbes. Intraepithelial macrophages (Langerhans cells), as well as lymphocytes and plasma cells located in the dermis, are responsible for the immune response.
Thermoregulation and participation in metabolism
The skin functions as a sophisticated thermostat due to the coordinated action of blood vessels, glands, and receptors.
- Heat dissipation (cooling). Sweat evaporation and heat radiation through dilated blood vessels account for up to 80% of all heat loss by the body.
- Heat conservation. The lipid film from the sebaceous glands reduces heat loss, and cornified scales act as a thermal insulator due to low thermal conductivity.
Additional systemic functions:
- Receptor function: perception of pain, temperature, and tactile stimuli (pressure, touch).
- Excretory function: elimination of water (about 500 ml per day), nitrogenous waste, and salts as part of sweat.
- Synthetic function: production of vitamin D under the influence of ultraviolet rays in the epidermis.
- Depot function: the ability of dermal vessels to store up to 1 liter of blood.
- Metabolic function: participation in hormone metabolism and toxin breakdown.
Briefly: answers to topical questions
What cellular layers make up the epidermis?
The epidermis consists of several layers. In "thick" skin, 5 layers are distinguished:
- Basal layer
- Spinous layer
- Granular layer
- Clear layer
- Horny layer
In "thin" skin, the clear layer is absent, and the remaining layers are thinner.
What layers is the dermis divided into?
The dermis is divided into two main layers:
- Papillary layer (stratum papillare) — the superficial layer formed by loose connective tissue.
- Reticular layer (stratum reticulare) — the deep layer represented by dense irregular connective tissue.
Which cells produce the pigment melanin in the epidermis?
Melanin pigment in the epidermis is produced by melanocytes. These are dendritic cells located in the basal layer of the epidermis. They form specific membrane organelles — melanosomes containing the melanin pigment.
Which encapsulated nerve endings (receptors) are located in the dermis?
Encapsulated nerve endings are located in the dermis:
- In the papillary layer of the dermis: Meissner's corpuscles (tactile corpuscles).
- In the reticular layer of the dermis / connective tissue: lamellar corpuscles (Pacinian corpuscles) and Ruffini corpuscles.
What else to study on this topic
- Histological structure of the epidermis: layers and cells
- Dermis: papillary and reticular layers
- Structure and secretion types of sweat and sebaceous glands
- Comparative characteristics of thick and thin skin
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