Hair and Nail PDF

Hair & Nail MODULE 4 Prepared by: MK SALAZAR-PASCUA Physical Sciences Department HAIR Functions Parts Growth Mechanism Types Hair Hairs (or pili) are characteristic of mammals. Hair is a keratinous filament growing out of the epidermis. It is primarily made of dead, keratiniz...

Hair & Nail MODULE 4 Prepared by: MK SALAZAR-PASCUA Physical Sciences Department HAIR Functions Parts Growth Mechanism Types Hair Hairs (or pili) are characteristic of mammals. Hair is a keratinous filament growing out of the epidermis. It is primarily made of dead, keratinized cells. hair shaft - non-living cells hair follicle - living cells hair bulb Hair Hairs develop in the fetus as epidermal downgrowths that invade the underlying dermis. Each downgrowth terminates in an expanded end that becomes invaginated by a mesodermal papilla. Central cells of the downgrowth become keratinized to form a hair Hair The presence of hair is a primary differentiator of mammals as a unique class of organisms. In humans, it is a cherished and highly visible indicator of health, youth, and even class. 01 Functions of the Hair 1. Protection Hair offers a protective covering, which regenerates on a regular basis. Head hair protects the scalp from UV radiation Hair serves as a filter (nose and ears)  Nose hair traps dust particles and microorganisms in the air and prevents them from reaching the lungs. Eyelashes and eyebrows protect the eyes from water, dirt, and other irritants. 2. Thermoregulation The hairs on the skin also help to control body temperature. ○ They lie flat when it is warm, and rise when it is cold. Hairs trap a layer of air above the skin, which helps insulate the skin against heat loss. ○ Head hair helps prevent heat loss from the head. 3. Balance Hair in the middle ear it serves as a mechanism for regulating balance. ○ Utricle and saccule contains sensory hair cells. ○ These cells contain otoconia that help monitor the position of the head in relation to gravity and linear motion 4. Sensation Hair also has a sensory function due to innervation of the hair papilla. The hair root is connected to the arrector pili that contract in response to stimuli, making the external hair shaft “stand up.” Goose-bumps Parts of the Hair Hair Shaft The hair shaft is the part of the hair not anchored to the follicle It is exposed at the skin’s surface. The hair shaft is made up of a cortex, surrounding cuticle cells, and sometimes a central medulla which is found in thicker hair. Hair Shaft: Cuticle It is the protective layer of the hair. It is made up of flat overlapping cells (scale-like) that cover the hair shaft from the root until it exits from the epidermis. It is responsible for lending the hair an untangled appearance and shape. Hair Shaft: Cuticle The cuticles hold the hair shaft on the follicle using a Velcro bond. It is important in the nourishment and moisturization of the hair. It stays open and closed when activated. The cuticles let the ingredients and chemicals into the strand and to the cortex. Hair Shaft: Cortex It is a layer of compressed keratinized cells Makes up bulk of the hair Plays an important role in determining the physical and mechanical properties of the hair, such as strength, texture, and color. It is composed predominantly of macrofibrils Hair Shaft: Medulla Medulla forms the central core of the hair Present in terminal hair follicles Hair Follicle The follicle is the primary structure from which hair can grow. It begins at the surface of the epidermis The histological arrangement of the follicle is divided into outer and inner root sheaths. External Root Sheath It is a ready supply of multipotent stem cells which differentiate into several cell types including melanocytes and keratinocytes. ○ insertion of the arrector pili muscle ○ ductal opening of the sebaceous gland. Outer Root Sheath It is also known as trichelemma It surrounds the hair follicle in the dermis and then blends into the epidermis on the surface of the skin, forming the structure commonly referred to as the pore Inner Root Sheath It consists of the Henle layer, the Huxley layer, and the cuticle layer It helps affix the growing hair shaft to the follicle It produces keratins and trichohyalin It forms a mold for the developing hair shaft. Dermal Papillae It contains fibroblasts that regulate the hair cycle and hair growth. The dermal papillae contains androgen receptors sensitive to DHT. It regulates follicular growth and differentiation. Hair Bulb The region of the follicle which actively produces hair. It extends into the dermal layer of the skin and surrounds the dermal papilla Arrector Pili Muscle It is a tiny muscle that attaches to the base of a hair follicle at one end and to dermal tissue on the other end. It contracts to generate heat when the body is cold, Hair Cycle Phase 1: Anagen The proliferation phase The hair follicle grows a new hair shaft. Scalp - 2 to 6 years Eyebrows and eyelashes - few months to grow. This is the only phase during which the inferior segment of the hair follicle is present. Phase 1: Anagen At birth, all hairs begin in the anagen phase At any one point in time, most hairs (85% to 95%) are commonly found in the anagen phase. Hairs can grow approximately 1 cm per month. Hair loss is continuous, with people losing about 100 hairs per day on average. Phase 2: Catagen Transition or regression phase. The shortest of all three phases 2-4 weeks Cell division in the matrix ceases, Hair follicle shrinks and detaches from the nourishing blood supply A club hair is formed with a white, hard node on the end. Phase 3: Telogen Resting phase On the scalp, these club hairs are typically held for about 100 days. These hairs are released and shed so anagen can begin again Exogen - hair fall and formation of new hair  Types of Hair Body Hair Texture Andre Walker Hair Types Types of Body Hair Lanugo Fine, soft, unpigmented hair Present in fetuses and newborns 5 months of gestation Types of Body Hair Vellus Short, fine and fuzzy hair that is much lighter in colour It lacks the medulla layer Temperature regulator Mostly found all over the body Types of Body Hair Terminal Hair that is darker and visible Influences by hormones Scalp, face, armpit, chest, and groin. It begins at the surface of the epidermis  The only parts of the external surface of the body that are truly hairless are the palms and soles of the hands and feet, lips, labia minora, and glans penis. Hair Texture Hair texture describes the circumference of the hair. There are three different hair texture types Fine Medium Thick Hair Texture Fine Fine hair is the most fragile hair texture. Each individual hair is thin and only has two hair layers; cortex and cuticle. Hair Texture Medium Medium hair is thicker than fine hair. The individual hairs have the same two hair layers that fine hair has, but may also have the third one – the medulla. Hair Texture Thick or Coarse Has all three hair layers; cortex, cuticle, and medulla. Gives the impression of a fuller head of hair Gets frizzy in humid weather Andre Walker Hair Typing System Hair type is primarily based on the hair’s curl pattern. The amount of curl in the hair is determined by the hair follicle The more oval or asymmetrical the follicle is, the curlier the hair will be. Hair type is determined by genetics. Type 1 - Straight Allows light to easily reflect its sheen. Natural oils flow smoothly Strong and resilient 1A - thin with a fine, soft texture. 1B - bit of body with a medium texture. 1C - straight, but it has a coarser texture. Type 2 - Wavy Has an S-shaped pattern Some sheen visible Prone to frizzing 2A - thin, fine-textured hair 2B - defined waves that fall close to the head. 2C - coarser texture and it easily frizzes Type 3 - Curly Tighter S-shaped pattern or loose coiled pattern that looks like a spring Strands tend to go back when pulled Natural shine may be visible or muted. 3A - loosely curled 3B - ranges from loose spiral ringlet curls to tight corkscrew curls. 3C - Pencil-width tight curls Type 4 - Coily Curls are very small, has a coily S-shape or Z-shaped zigzag pattern. Texture ranges from fine to coarse, and it may be soft or wiry. 4A - soft, pliable, dense S-shaped coils 4B - denser and thicker Z-shaped coils 4C - Z-pattern hair is the most fragile and prone to breakage. 02 Nail Nail The nail is a specialized structure of the epidermis that occurs at the tips of our fingers and toes. The nail body is formed on the nail bed, and it is designed to protect the tips of our fingers and toes Maximum mechanical stress. Parts of the Nail Nail Plate Composed of hard, keratinized, squamous cells that are loosely adherent to germinal matrix but strongly attached to the sterile matrix. It is the dead part of the nail unit. It is the main part of the nail exposed to cosmetics. Perionychium It is the nail complex It is composed of the nail bed, nail fold, eponychium, paronychium, and hyponychium. Nail Fold The most proximal aspect of the perionychium. It is composed of a dorsal roof and a ventral floor. ○ The dorsal roof rests above the forming nail It plays a role in housing cells that impart shine to the nail. ○ The ventral floor lies beneath the nail, immediately distal to the insertion of the extensor tendons. It is the site of the germinal matrix and is responsible for 90% of nail production. Eponychium The skin proximal to the nail that covers the nail fold. The nail fold that meets the proximal end of the nail body forms the nail cuticle The tissue distal to the eponychium in contact with the nail represents the cuticle. Paronychium The fold on each lateral aspect of the nail where the nail curves into the fingertip. Lateral nail fold “Side walls” of the nail Lunula It is the distal extent of the germinal matrix. It is a half-moon shaped white arc. This characteristic color change is due to the persistence of nail cell nuclei in the germinal matrix; distal to this location, nuclei are absent, and the nail is transparent. Sterile Matrix This is a secondary site of nail production It is tightly adherent to the nail plate and the periosteum of the distal phalanx. Hyponychium A junction formed between the sterile matrix and the fingertip skin beneath the nail margin. This region is susceptible to contamination from environmental interactions. It has a keratin plug Thanks! Do you have any questions?