Catalyst Questions What are the three zones of hair? What are the two types of sweat glands and where are can they be found in the body? What are the sebaceous glands? With what are they associated with?

Let’s Review… The bulb, root, and the shaft. Merorcrine which can be found on palms, soles, and forehead (all over really). Aprocrine are found in the groin, anal region, axilla, areola, and beard area. Produce oily secretion called sebum. –Sebum keeps the skin and hair from becoming dry, brittle, and cracked.

Class Updates! Test on Friday, September 26 th ! I have binders for sale, if you still do not have yours… Extra credit still offered for those who bring in tissue! MAKE UP TEST NEED TO BE DONE BY THE END OF THE WEEK!

Test Corrections You will have the opportunity to go over your test and correct wrong answers. For each, you have to give at least a sentence stating WHY it is the correct answer. For each correct answer given you get a HALF-POINT back. These are due Monday, September 22 nd !

What’s Happening in Science?

Functions of the Skin and the Epidermis

Objectives You will be able to list the functions of the skin and relate them to its structure. You will be able to describe the histological structure of the epidermis, dermis, and subcutaneous tissue.

5-8 Functions of the Integumentary System Structures that are part of the integument –Skin –Hair –Nails –Glands Overview of Functions –Protection –Sensation –Temperature regulation –Vitamin D production –Excretion –Immunity

FUNCTIONS OF THE SKIN Resistance to trauma and infection: The skin bears the brunt of most physical injuries to the body, but it resists and recovers from trauma better than organs do. The epidermal cells are packed with the tough protein keratin. Few infectious organisms can penetrate the intact skin. Water Retention: the skin is important as a barrier to water. It prevents the body from absorbing excess water when you are swimming or bathing, but even more importantly, it prevents the body from losing excess water.

FUNCTIONS OF THE SKIN Vitamin D Synthesis: Vitamin D is needed for bone development and maintenance. The skin begins the synthesis process, which is later finished by the kidneys and liver. Sensation: The skin is our most sensitive organ. It is equipped with a variety of nerve endings that react to heat, cold, touch, texture, pressure, vibration, and tissue injury. These sensory receptors are especially abundant on the face, palms, fingers, soles, nipples, and genitals.

FUNCTIONS OF THE SKIN Thermoregulation: In response to chilling, the skin helps to retain heat. There are nerve endings called thermoregulators that transmit signals to the brain and then signals are sent back to dermal vessels which either constrict when you are cold or expand when you are hot. If this is not enough, the brain also triggers sweating. Nonverbal communication: The skin is an important means of communication. Complex skeletal muscles insert on dermal collagen fibers and pull on the skin to create subtle and varied facial expressions.

Epidermis The epidermis is a keratinized stratified squamous epithelium, which means the surface consists of dead cells packed with keratin that are in multiple layers and are of a flat, scaly shape. The epidermis lacks blood vessels and depends on the diffusion of nutrients from the underlying connective tissue.

5-13 Epidermis Avascular; nourished by diffusion from capillaries of the papillary layer of the dermis Composed of cells arranged into layers or strata. Separated from dermis by basement membrane

FIVE LAYERS OF THE EPIDERMIS The Stratum Basale: consists mainly of cuboidal to low columnar stem cells and keratinocytes resting on the basement membrane. The Stratum Spinosum: consists of several layers of keratinocytes; in most skin, this is the thickest stratum. As the cells are pushed upward (from more cells being produced in the stratum basale), the cells of the stratum spinsoum cease dividing and begin to produce more and more keratin filaments, which cause the cells to flatten. The higher you go in the stratum spinosum, the flatter the cells appear.

FIVE LAYERS OF THE EPIDERMIS The Stratum Granulosum: consists of 3-5 layers of flat keratinocytes- more in thick skin than in thin skin- and some dendritic cells. The keratinocytes in this layer contain coarse, dark-staining granules of keratin, which give the layer its name

FIVE LAYERS OF THE EPIDERMIS Stratum Lucidum: is a thin, transluscent zone superficial to the stratum granulosum, seen only in thick skin. Here the keratinocytes are densely packed with eleidin. The cells have no nuclei or other organelles. This zone has a pale, featureless appearance with indistinct cell boundaries. Stratum Corneum: consists of up to 30 layers of dead, scaly, keratinized cells that form a durable, water-resistant surface layer.

5-17 Epidermal Layers and Keratinization

5-18 Subcutaneous tissue Deep to skin Consists of loose connective tissue with collagen and elastic fibers Types of cells –Fibroblasts –Adipose cells –Macrophages Also called –Hypodermis –Superficial fascia Contains about one-half of body’s adipose tissue. Functions as –Energy source –Insulation –Padding

5-19 Thick and Thin Skin Thick skin –Has all 5 epithelial strata –Found in areas subject to pressure or friction Palms of hands, fingertips, soles of feet –Fingerprints and footprints. Papillae of underlying dermis in parallel rows Thin skin –More flexible than thick skin –Covers rest of body –Hair grows here Callus. Increase in number of layers in stratum corneum. When this occurs over a bony prominence, a corn forms.

5-20 Effects of Aging on the Integumentary System Skin more easily damaged because epidermis thins and amount of collagen decreases Skin infections more likely Wrinkling occurs due to decrease in elastic fibers Skin becomes drier Decrease in blood supply causes poor ability to regulate body temperature Functioning melanocytes decrease or increase; age spots Sunlight ages skin more rapidly

5-21 Burns Classifications –First-degree –Second-degree –Third-degree Skin Grafts –Split skin –Artificial skin –Cadavers or pigs

5-22 The Rule of Nines Used to estimate amount of body that is burned. Note differing proportions in adult and child.

Half Sheet Complete the half- sheet questions as review and to ensure you are keeping up with the material. These questions are VERY representative of the types of questions you’ll see on your test.