Anatomy of the Hair, Nails, and Skin

Hair Three types Lanugo Vellus Terminal Hair is a slender filament composed of keratinized cells . Hair grows from a tube located in the skin called the hair follicle. There are 3 types of hair. One is lanugo which is fine, downy, not pigmented and generally appears on the fetus. By the time of birth this hair generally replaced The second kind of skin is vellus which is also fine and pale. This type of hair is mostly present on children however it is found on men and women. Thee last type of hair is terminal hair. This hair is longer, coarser, and is usually more heavily pigmented

Hair structure Bulb Root Shaft Dermal papilla Hair matrix Medulla Cortex Cuticle The bulb is a swelling at the base where the hair originates in either the dermis or hypodermis The root is the remainder of the hair within the follicle and the shaft is the portion above the skin surface The dermal papilla is the area in which the bulb grows around and provides the hair with its sole source of nutrition The hair matrix is the hairs growth center and is the only area which contains live cells The medulla is the inner core of the hair shaft The cortex is the thickest part of the shaft and is composed of several layers of keratinized cells The cuticle is made up of scaly cells that overlap each other like shingles on a roof

Hair Texture Straight hair= round Wavy hair= oval Tight and curly= flat The texture of hair is based on the differences in cross-sectional shape When an individual has straight hair the shape of their hair tends to be round A person with wavy hair had oval shaped hair and someone with tight and curly hair has flat hair

Hair Color Brown- Eumelanin Black- Eumelanin Red- Eumelanin and pheomelanin Blonde- Pheomelanin Hair color is the result of pigment molecules in the cells of the hair shaft Both brown and black hair are colored due eumelanin Red hair has low concentration of eumelanin and a high concentration of pheomelanin The pigment in blond hair is pheomelanin

Hair Growth and Loss Stages Anagen Catagen Telogen The anagen stage is when the hair follicle is growing and 90% percent on the hair is in this stage. Catagen in this stage hair growth has stopped The Telogen hair is the phase when the hair begins to shed

Nails Thin, scaly cells Keratin Nail plate Nail body Nail fold Nail groove Nail bed Eponychium The nail is composed of thin scaly and dead cells and filled with keratin fibers The nail plate is the hard part of the nail and the overhanging part of the nail is known as the free edge The nail body is the part of the nail that is attached The nail fold is the skin surrounding the nail plate and the nail groove separates the two The nail bed is the skin underneath the nail plate The (EP-o-NICK-ee-um) is the cuticle

Functions of Skin Resistance to trauma and infection Barrier Vitamin D synthesis Sensation Thermoregulation Non verbal communication The skin receives more damage than any other organ in the body. The skin is able to cope with the damage it receives because of the epidermal cells which contain keratin. Very few infectious agents can actually penetrate the skin which helps protect the body from disease. The skin is a very good barrier to water which is very important when you bathe and go swimming. The skin prevents the body from absorbing excess water during these activities. Not only does the skin prevent the body from taking in too much water it prevents the body from losing large amounts of water. The epidermis is one of the body’s main defense against cancer causing radiation. The first step of vitamin D synthesis is carried out by the skin. The skin is the body’s largest sense organ. The skin can detect many different environmental changes. The skin can help detect changes in temperature, textures, pressure and tissue injury. Thermoregulation. The skin contains cutaneous nerve endings called thermoreceptors which are responsible for monitoring the bodies surface temperature. The skin allows for humans to be much more expressive than other mammals. The skin, hair and nails are very important for humans when it comes to their social wellness.

Epithelial cells of the skin Keratinized stratified Squamous Non-keratinized stratified squamous Keratinized stratified squamous- the function of these cells includes resistance to abrasion and penetration by pathogenic organisims. These cells help with water loss through skin. Also these cells contain a layer of dead skin making it easier to resist abrasion. These cells are mostly located on thick skin Non-keratinized stratified squamous- the function of these cells is to resist abrasion and penetration by pathogenic organisms

2 Main layers There are two main layers of the skin. The first layer of the skin is called the epidermis The second layer of the skin is the dermis There are also two types of skin The first type is thick skin which contains an extra layer in the epidermis. This type of skin is only located on the palms of your hands and the soles of your feet. The second type of skin is thin skin which contains only 4 layers in the epidermis. This skin is located over the entire body.

Epidermis The epidermis is the first layer of the skin The epidermis has 5 layers(deep to superficial) Stratum Basale Stratum Spinosum Stratum Granulosum Stratum Lucidum (thick skin only) Stratum Corneum The first layer of the skin is called the epidermis from deep to superficial the layers of the epidermis are The stratum lucidum is seen only in thick skin

Dermis The (dermis) is the underlying or inner layer of the skin. The dermis is composed of three types of tissue that are present throughout and not in layers. These types of tissue are: collagen elastic tissue reticular fibers

Subcutaneous Tissue The subcutaneous tissue is a layer of fat and connective tissue that houses larger blood vessels and nerves. The size of this layer varies throughout the body and from person to person.

References Saladin Anatomy and Physiology