Hair

Anatomy and Structure of the Hair Follicle

Hair is a keratinized thread-like structure that develops from the epidermis and dips deep into the dermis. The hair follicle serves as the anchor that holds the hair in place beneath the skin surface. At the base of the follicle lies the hair bulb, which surrounds a cluster of connective tissue and blood vessels known as the dermal papilla. This papilla nourishes the growing cells. Just above the papilla is the hair matrix, an actively dividing layer of cells responsible for the production of the hair shaft itself.

The hair shaft consists of three distinct concentric layers:

• Cuticle: The outermost layer made of overlapping, transparent cells that protect the inner structure.
• Cortex: The middle layer that contains most of the hair's pigment, melanin, and provides strength and elasticity.
• Medulla: The innermost core, which may be absent in fine or light-colored hair.

Attached to the side of the follicle is the arrector pili muscle, a tiny bundle of smooth muscle fibers. When these muscles contract in response to cold or fear, they pull the hair upright, causing goosebumps on the skin and trapping a layer of air for insulation.

The Hair Growth Cycle: Anagen, Catagen, and Telogen

Hair does not grow continuously at an equal rate; instead, it follows a repeating cycle of growth, regression, and rest. Understanding this cycle helps midwives explain normal postpartum shedding to new mothers.

1. Anagen phase: This is the active growth phase where cells in the hair matrix divide rapidly. Hair can stay in this phase for several years, determining the maximum length of the hair.
2. Catagen phase: A short transitional phase lasting about two to three weeks. Cell division stops, and the hair follicle shrinks, detaching from the nourishing blood supply.
3. Telogen phase: The resting phase where the hair remains in the follicle without growing, lasting roughly three months. Eventually, a new anagen hair begins to push the old telogen hair out, resulting in normal daily shedding.

Physiological Functions of Hair in the Human Body

While human body hair is often viewed primarily for its cosmetic value, it plays several protective and sensory roles. Scalp hair acts as a physical barrier against ultraviolet radiation from the sun and provides thermal insulation in cold weather.

Eyelashes and eyebrows prevent sweat, dust, and foreign debris from entering the eyes. Fine vellus hairs distributed across the body surface contain sensory nerve endings wrapped around their follicles, making them sensitive to light touch and air movement. This sensory network alerts the body to the presence of insects or foreign particles on the skin before they can cause harm.

Common Hair Disorders and Clinical Presentations

Hair disorders can reflect local dermatological conditions or systemic health problems such as nutritional deficiencies or endocrine imbalances.

• Alopecia: General term for hair loss. Alopecia areata presents as patchy, smooth round areas of hair loss, while female or male pattern baldness follows a more predictable receding pattern.
• Hirsutism: Excessive growth of dark, coarse hair in a male-like pattern on women, often caused by high androgen levels seen in conditions like polycystic ovary syndrome (PCOS).
• Tinea capitis: A fungal infection of the scalp, commonly called ringworm of the scalp, presenting with scaly, red, circular patches and broken hair shafts.
• Pediculosis capitis: Infestation with head lice, characterized by severe itching and the presence of tiny white eggs attached tightly to the hair shafts near the scalp.

Nursing Assessment of the Hair and Scalp

Evaluating the hair and scalp is an essential part of the physical examination during antenatal or general clinical checks. The midwife inspects the hair for color, texture, distribution, and cleanliness. Normal hair should feel resilient and not break easily when gently pulled.

Palpation of the scalp checks for tenderness, lumps, scaling, or signs of inflammation. Dry, brittle hair can indicate nutritional deficiencies such as severe protein-calorie malnutrition or iron deficiency anemia, which are vital to screen for during pregnancy. Documenting any abnormalities ensures proper referral and ongoing care.