The Basics of Hair Anatomy

hair is an intricate network composed of both living and nonliving components. An experienced examiner can distinguish individual strands of hair. Nonliving components include the coiled-coil keratin phase and cuticle layers, while living members have the dermal papilla. During the anagen phase, cells in the follicle grow upwards to form significant parts of hair: pith, cortex, cuticle, and root sheath.

The Hair Follicle

The hair follicle is a small, stocking-like structure located in the outermost layers of your skin (epidermis and dermis). It contains sheaths that shape your hair, oil glands to condition it, and cells that produce new strands. It also controls the growth cycle and cycle of your hair. Hair follicles play a pivotal role in both hair texture and color. Curlier locks require circular strands, while straighter hair requires oval ones. Melanin, produced by cells within the follicular matrix, gives your locks its pigment. Follicles also determine your hair shape, with their shape dictating whether your locks are straight or curly.

Bilateral signals between the epidermis and mesenchyme at embryogenesis trigger hair follicle formation. Cells from the epidermis migrate downward to engulf mesenchymal cells in an epidermal condensate, which later forms the dermal papilla of the hair follicle. This structure then instructs epithelial cells that ensheath it during initial down growth to proliferate and differentiate into complex systems such as matrix matrixes, bulbs, and shafts.

The Hair Shaft

Hair is composed of dead cells compacted together into a dense mass. These cells are often called keratin, a protein that forms strong disulfide and hydrogen bonds, giving the hair its strength and resistance against breakage. The core of each hair shaft is called the cortex, consisting of long chains of keratin that provide it with structure, elasticity, stiffness, and color. The cortex lies within an outer protective shell known as the cuticle, which helps prevent damage to the hair.

Hair follicles are skin adnexa, formed through epithelial-mesenchymal interactions programmed during embryonic development. They produce, grow, and shed hair in an organized and regular cyclic fashion. They have new strands every cycle as the old ones shed off. Hair follicles also host sebaceous glands, which condition the scalp and hair, and are connected with their roots to anchor them securely within the dermis.

The Hair Matrix

Hair follicles are skin adnexes programmed to regenerate fully cyclically and autonomously during embryonic development. They act like small organs with three compartments: epithelial (hair matrix), mesenchymal (dermal papilla), and sebaceous. The germinal matrix at the base of each hair bulb, houses proliferating cells that form parts of a hair follicle, such as internal root sheaths and hair shafts. These cells also play a crucial role in transferring melanin pigmentation onto hair shafts to give them their unique hue. The hair matrix is located beneath a glassy basement membrane and exhibits the highest mitotic activity in the body. Cells proliferate into matrix keratinocytes that become root sheaths, sheaths, and shafts. After increasing into these forms, they go through a process known as keratinization, forming the thick outer rigid cuticle to protect the soft inner cortex and medulla areas of hair follicles from extreme heat damage. Additionally, when contracting, the arrector pili muscle bundles release heat, which elevates goosebumps while helping remove sebum from the gland into its respective duct.

The Hair Root

Hair plays an essential part in society, symbolizing health, attractiveness, and youth for both men and women. It serves to ward off cold air and dust while adding insulation and protecting from exposure to cold temperatures. Hair follicles deep within the scalp’s skin produce long, thin, cylindrically-shaped hair strands visible above its surface. Furthermore, this organ has a pigment that gives hair its color. Hair follicles contain a dermal papilla that provides new hair cells with nutrients from capillaries in the underlying skin. An arrector pili muscle attaches directly to the dermal papilla and feeds new hair cells as they grow out. When people get goosebumps or animals like cats are startled, they raise their fur in fear.