anatomy and physiology chapter 5 guided questions

Objective #2: Discuss the four cell types of the epidermis.

See Page 108, Fig 5.2 The epidermis is composed of stratified squamous epithelium and contains four principal types of cells: keratinocytes melanocytes Langerhans cells Merkel Cells Keratinocytes produce the protein keratin, which helps protect the skin and underlying tissue from heat, microbes, and chemicals. Keratin produces lamellar granules, which release a waterproof sealant. Melanocytes produce the pigment melanin, which contributes to skin colour and absorbs damaging ultraviolet (UV) light. Langerhans Cells participate in immune responses. Merkel Cells touch a sensory structure called a tactile (Merkel) disc and function in the sensation of touch.

Objective #4: Distinguish between the papillary layer and the reticular layer of the dermis, and locate the appropriate sensory receptor in each of these layers. See Page 109, Fig 5.1

The dermis, composed of connective tissue containing collagen and elastic fibres, has two regions. The papillary layer is areolar connective tissue that contains fine elastic fibres; dermal papillae; corpuscles of touch (Meissner's corpuscles); and free nerve endings for sensations of heat, cold, pain, tickle, and itch. The deeper part of the dermis is the reticular region, which consists of dense, irregular connective tissue that contains bundles of collagen fibres and some elastic fibres. Epidermal ridges increase friction for better grasping ability, and provide the basis for fingerprints and footprints. Typically, the ridges reflect contours of the underlying dermis.

Objective #8: Discuss the functions of the skin.

See Page 114, Fig 5.1 The major functions of the skin are the following: Thermoregulation Protection through physical, chemical, and biological barriers. Cutaneous sensations including: touch pressure vibration tickle heat cold pain Excretion and absorption Synthesis of Vitamin D

Objective #1: Name the layers of the skin; describe the structure of each; and name the general functions of the skin.

See Pages 107-108, Fig 5.1 Structurally the skin consists of the following two parts: Epidermis—the superficial portion of the skin composed of epitehlial tissue Dermis—the deeper layer of the skin primarily composed of connective tissue The subcutaneous layer (Sub Q) or hypodermis lies deep within the dermis. It consists of areolar and adipose tissue. It serves as an area for fat storage, blood vessel passage, and pressure nerve endings.

Objective #3: List the four/five layers of the epidermis, and explain the process of keratinization.

See Pages 108-109, Fig 5.2 The epidermis has four or five layers, depending on the degree of friction and mechanical pressure applied to the skin. From the deepest to the most superficial, the layers of the epidermis are the following: stratum basale (stratum germinativum) stratum spinosum stratum granulosum stratum lucidum (only in the palms and soles) stratum corneum The stratum basale is the deepest layer of the epidermis and contains some stem cells capable of undergoing cell division to form new cells. This layer is sometimes called the stratum germinativum to indicate its role in the formation of new cells. The stratum spinosum provides strength and flexibility to the skin. The stratum granulosum marks the transition between the deeper, metabolically active strata and the dead cells of the more superficial strata. This layer is also where a water repellent sealant forms between the cells. The stratum lucidum is present only in the fingers, palms, and soles. The stratum corneum is the most superficial layer; it consists of dead cells. Lamellar granules in this layer make it water-repellent. Constant exposure to friction causes this layer to increase in depth by forming a callus, an abnormal thickening of the epidermis. Keratinization, the replacement of cell contents with the protein keratin, occurs when cells move to the skin surface over a period of two to four weeks.

Objective #5: Name the pigment responsible for skin and hair colour, and explain how people of different races (and skin colour) differ with respect to this pigment; and name the cell that produces it.

See Pages 109-110 The wide variety of colours of skin is due to three pigments—melanin, carotene, and hemoglobin (in blood in capillaries)—in the dermis.

Objective #6: Describe the general structure of hair.

See Pages 110-111, Fig 5.3 Hair consists of the following: shaft above the surface a root that penetrates the dermis and subcutaneous layer cuticle hair follicle The functions of hair include protection, decreasing heat loss, and sensing light touch.

Objective #7: List the glands associated with the skin, and the products they secrete.

Skin glands are of three types as follows: Sebaceous (oil) glands usually are connected to hair follicles; they are absent in the palms and soles. Sebaceous glands produce sebum, which moistens hairs, waterproofs and softens the skin, and inhibits bacterial growth. Sudoriferous (sweat) glands are divided into apocrine and eccrine types. Eccrine sweat glands help to regulate body temperature through vaporation and to eliminate wastes such as urea. Apocrine sweat glands are limited to the skin of the axilla, pubis, and areolae; their ducts open into hair follicles. Ceruminous glands are modified sudoriferous glands that produce a waxy substance called cerumen. These glands are found in the external auditory meatus.