Skin

Skin

1. Epidermis

   • Consists of stratified squamous epithelium, composed of strata cells.
     • The cells of the Malpighian layer may contain pigment granules, and the horny layer is thick

2. Dermis

   • Consists of papillary layer and reticular layer.
     • The outer part of the dermis projects into the epidermis forming microscopic dermal papillae in which nerve fibers are found

3. Pigmented skin

   • Dark melanocytes in the basal layer of the epidermis

4. Sebaceous glands

   • Small glands of the simple branched aveolar type
   • Usually each is connected to a hair and opens by a short duct close to it
   • The cells of the sebaceous gland look full of cavities
     • These were occupied by fat globules which were dissolved

5. Sweat glands

   • Much longer and are of the simple coiled tublar type
   • Each gland opens on the surface through a long winding duct, while the secretory part of the gland lies deeply embedded in the dermis

6. Hair

   • A hair is an elongate structure, whose shaft projects obliquely on the surface of the body
   • It consists of a hair-medulla (formed of cells) in the middle followed by a hair-cortex (formed of a fibrous material) and a hair-cuticle on the surface (formed of scales)
   • The deeper part of the hair is the hair-root, which is lodged in the hair-follicle, which swells up at the base forming the hair-bulb into which project, from the dermis, blood vessels, nerves, and connective tissue forming the hair-papilla
   • The hair bulb is formed of an actively proliferating germinal epithelium, from which the growth of the hair takes place.
   • The walls of the hair-root and hair-follicle are formed of several layers of epithelial cells which are continuous at the surface with the malpighian layer of the epidermis
   • A number of unstriated muscle fibers are connected to the epidermis. They move the hair involuntarily and from what is known as the erector muscle of the hair