Hair is composed of 95% keratin, a fibrous and helical protein in a helix shape.  There are two key components to your hair structure.   The hair follicle and the hair shaft. While working together, each has a distinct role in the composition of your strands.  

The hair follicle sits underneath the skin’s surface and extends down into the dermis layer of your skin. Each follicle has a sebaceous gland that produces lipid-rich sebum (an oil) which naturally protects the hair and moisturizes the scalp.  At the base of the hair follicle is a hair bulb. This is where the actual hair growth process occurs.  Blood vessels deliver nutrients to the cells inside of the hair bulb. As hair cells grow, they are attached to the follicle and the older cells are pushed outwards resulting in the strand-like appearance of your hair.  The hair shaft is the hard filamentous strands visible above the skin’s surface.   The innermost layer is made up of the sugar and amino acids, glycogen, citrulline and is referred to as the medulla.   The cortex or middle layer that surrounds the medulla. It contains keratin bonds that aid in elasticity and melanocytes, special cells that produce melanin pigment that determines hair color.   The outermost layer of the hair. It’s covered by a single molecular layer of lipids that repels water and gives hair its shine.  This is referred to as the cuticle.  According toNCBI study, these nutrients are important building blocks for keratin protein and a key part of making sure our hair is thick, healthy, and strong.  Biotin  is a water-soluble form of vitamin B that supports hair growth and defends hair from environmental damage.   Iron supports hair growth because it helps to form red blood cells that deliver oxygen and nutrients to the hair follicles. Hair loss is often a symptom of iron deficiency anemia. Vitamin C is a powerful antioxidant and protects hair follicles from damaging free radicals that contribute to discoloration and even hair loss.
18 amino acids are involved in the composition of hair, such as proline, threonine, leucine or arginine, keratin is particularly rich in cysteine  which form disulfide bridges between molecules, giving its rigidity and strength to the whole.   Even though your hair is made of cells that are technically no longer living, you can still take care of your strands to help your hair look its best.   If you keep your hair healthy and well maintained it generally appears shiny and flexible.   Wash your hair with quality shampoo.  Clean your scalp.  Condition your hair to your satisfaction.