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Skin and Its Layers

Integumentum commune, Cutis

For medical students2 min readUpdated 2026-10-10

The skin forms the general integument of the human body and represents a complex, multi-layered organ. It contains blood vessels, glands, sensory nerve endings, as well as hair and nails. Anatomically, the skin consists of two main parts: the epidermis and the dermis.

Embryological originThe epidermis forms from the ectoderm, while the dermis (proper skin) develops from the mesoderm.

Epidermal nutritionThe epidermis lacks blood vessels; it receives nutrition exclusively via diffusion from the underlying dermis.

Stratum lucidumThis layer of the epidermis is found only in thick skin (such as the palms of the hands and soles of the feet).

Subcutaneous tissueHistologically, the hypodermis is not part of the skin proper, but rather lies beneath it as a supporting layer.

General Structural Plan of the Integumentary System

The general integument of the body (integumentum commune) consists of the skin (cutis) and the underlying subcutaneous tissue. Within the skin lie sensory nerve endings, blood and lymphatic vessels, as well as glands, hair, and nails.

Functionally and histologically, the skin is divided into two main layers:

Epidermis (epidermis) — the superficial layer.
Dermis, or corium (dermis, corium) — the deep connective tissue framework.

Deep to the dermis lies the subcutaneous tissue (tela subcutanea). It is important to note that anatomically, it is not considered part of the skin layers proper, although it is topographically closely related.

Epidermis and Its Layers

The epidermis is derived from the ectoderm and is composed of keratinized stratified squamous epithelium. It lacks its own blood vessels, meaning cells are nourished entirely via diffusion from the underlying layer.

Layers of the epidermis (from deepest to most superficial):

Stratum basale (stratum basale). Formed by a single row of columnar cells. This is an active germinative layer where mitosis constantly occurs. It also contains melanocytes, which produce the pigment melanin.
Stratum spinosum (stratum spinosum). Consists of several layers of cells. They are characterized by special intercellular "spines" that tightly bind cells together and provide mechanical strength to the entire epidermis.
Stratum granulosum (stratum granulosum). Includes 3–5 rows of cells. Their cytoplasm accumulates keratohyalin granules.
Stratum lucidum (stratum lucidum). Not universally present — it is found only in so-called thick skin (soles and palms). Cells in this layer lack nuclei and are completely filled with eleidin.
Stratum corneum (stratum corneum). The most superficial stratum. Consists of flat, keratinized dead cells that continuously desquamate and renew. It performs the primary barrier and protective function.

Dermis (Corium)

The dermis (dermis, corium) is derived from the mesoderm. It consists of robust fibrous connective tissue.

The dermis is divided into two layers:

Papillary layer (stratum papillare). Formed by loose connective tissue. It forms specialized projections (papillae) that extend into the epidermis. This layer contains blood and lymphatic capillaries that nourish the overlying epithelium, as well as nerve endings.
Reticular layer (stratum reticulare). Formed by dense irregular connective tissue. It contains a dense network of collagen and elastic fibers, providing high mechanical strength and elasticity to the skin.

Skin Surface Relief

The skin surface is not completely smooth. It forms a complex pattern of surface markings:

Sulci and ridges (sulci cutis and cristae cutis). The pattern they create is strictly individual for each person and remains constant throughout life (this exact feature is utilized in fingerprinting/dermatoglyphics).
Skin creases and folds. These can be permanent or temporary (most commonly forming around joints during movement).

Subcutaneous Tissue (Hypodermis)

The subcutaneous tissue (tela subcutanea) lies deep to the dermis. It consists of loose connective tissue whose meshes enclose lobules of adipose tissue (fat panniculus). In certain anatomical regions (e.g., eyelids, auricle, scrotum), adipose tissue is entirely absent.

Main functions of the subcutaneous tissue:

thermal insulation of the body;
shock absorption against mechanical impacts and pressure;
mobility of the skin relative to underlying fascia and muscles;
energy storage (fat reserves).

Mnemonic

To remember the layers of the epidermis from deep to superficial, use the mnemonic: "Come Let's Get Sun Burned" (Corneum, Lucidum, Granulosum, Spinosum, Basale).

Frequently asked questions

What skin appendages (derivatives) are recognized in human anatomy, and specifically which types of glands belong to them?

Skin appendages in human anatomy include hair, nails, and glands. The following types of glands are recognized:

Sweat glands (glandulae sudoriferae).
Sebaceous glands (glandulae sebaceae) — their ducts empty into hair follicles.
Mammary glands — modified sweat glands.

Hair and nails are also derivatives of the cutaneous ectoderm.

What encapsulated and free nerve endings are located in the various layers of the skin?

Both free and encapsulated nerve endings are located throughout the various layers of the skin.

The epidermis contains free nerve endings and Merkel touch discs (which function as unencapsulated mechanoreceptors).
The papillary dermis houses encapsulated Meissner corpuscles, as well as non-encapsulated (free/unencapsulated) endings.
The reticular dermis contains deep encapsulated receptors: Pacinian lamellar corpuscles, Ruffini endings, and Krause end bulbs.

What cells, besides keratinocytes and melanocytes, are present in the epidermis?

In addition to keratinocytes and melanocytes, the stratified squamous keratinizing epithelium of the epidermis contains other specialized cells. These include:

Langerhans cells — specialized antigen-presenting dendritic cells of macrophage lineage.
Merkel cells — tactile epithelial cells that perform a sensory receptor function.
T lymphocytes — predominantly cytotoxic CD8+ lymphocytes localized in the basal and spinous layers.

Other dendritic and neuroectodermal cells are also present.

What are Langer's lines (cleavage lines) and how do they relate to the structure of the reticular dermis?

Langer's lines are tension lines of the skin that dictate the direction of wrinkle and fold formation. Their orientation is determined by the alignment of collagen fibers. The principle of Langer's lines applies to all body regions, even those where visible lines are absent. The reticular dermis (stratum reticulare), composed of dense irregular connective tissue, contains these collagen and elastic fibers that provide tensile strength and elasticity to the skin.

Are hair, nails, and subcutaneous tissue part of the skin?

Hair, nails, and glands are skin appendages located within its thickness. However, the subcutaneous tissue (tela subcutanea) lies deep to the dermis and is not classified as a layer of the skin proper.

How do the stratum corneum and other epidermal layers receive nutrients?

The epidermis contains no blood capillaries. All nutrients are delivered via diffusion from the capillaries of the papillary dermis.

What is the difference between thin skin and thick skin?

Thick skin (found on the palms and soles) features an additional layer—the stratum lucidum—which is absent in other regions of the body covered by thin skin.

Where in the skin is the pigment melanin produced?

Melanin is synthesized by specialized cells called melanocytes, which are located in the deepest layer of the epidermis, the stratum basale.

Go deeper

Cellular composition of the epidermis (keratinocytes, melanocytes, Langerhans, and Merkel cells)
The process of keratinization: from keratohyalin synthesis to cornified cell envelope formation
Anatomy and physiology of skin appendages (structure of hair follicles, sebaceous and sweat glands)
Morphological basis of dermatoglyphics: how ridges and sulci form