INTEGUMENT AND GLANDS 1. Which of the following statements in regards to skin is INCORRECT? skin functions as a barrier to bacteria and dessication, as a sensory eptor, and in vitamin D production skin is usually divided into three layers the epidermis (epithelial er), the dermis (dense connective tissue underlying the epidermis) and hypodermis (subcutaneous layer of fatty connective tissue) skin can be classified as thin or thick based on dermal thickness thin skin contains hair follicles and sweat glands and covers most of body surface all of the above are correct Correct. No, the answer is C. Skin is classified as thin or thick based on epidermal thickness. Thick skin covers the palms of the hands and has no hair follicles. Other functions of the skin include temperature regulation and protection from trauma and UV radiation. 2. The epidermis of thick skin consists of five layers. Which of the following is the correct sequence of layers from the dermis to the skin's surface? (s = stratum) s. basale, s. granulosum, s. spinosum, s. lucidum, s. corneum s granulosum, s. basale, s. spinosum, s. corneum, s. lucidum s. basale, s. spinosum, s. lucidum, s. granulosum, s. corneum s. basale, s. spinosum, s. granulosum, s. lucidum, s. corneum none of the above are correct Very good. No, the answer is D. Thin skin has the same basic structure except that the stratum lucidum is usually not seen, the individual layers are usually thinner, and hair follicles are present. 3. Which of the following associations concerning the epidermal layers is INCORRECT? stratum basale - 3 to 4 cell layers thick which stain acidophilic stratum spinosum - 4 to 5 layers of cells with cytoplasmic processes projecting to neighboring cells to form desmosomal junctions stratum granulosum - 1 to 2 layers of cells with many granules and tonofilaments stratum lucidum - thin transparent layer, more easily seen in thick skin stratum corneum - surface layer formed by non-nucleated keratinized cells Right. No, the answer is A. The stratum basale is the most basal layer right above the basement membrane It is only one cell layer thick and the cytoplasm of these cells stains basophilic reflecting their high metabolic and mitotic activity. It gives rise to all the layers above it and usually exhibits 1 or 2 mitotic figures per 1000 cells. It takes about 3-4 weeks for the epidermis to completely renew itself. The transparent nature of the stratum lucidum under the light microscope is probably due to the unique arrangement of keratin in the cytoplasm. 4. In cells of the stratum spinosum membrane coated granules begin to appear and cells of the stratum granulosum begin to accumulate keratohyalin granules True False Very good. No, the answer is true. Cells of the stratum spinosum begin to acquire Membrane Coated Granules (MCGs) and stratum granulosum cells accumulate keratohyalin granules (KH) which contain histidine rich protein, RNA, polysaccharides and lipids. These granules are almost always associated with tonofilaments. Here MCGs begin to release their content into the intercellular space to coat the cell surfaces, forming the primary intercellular barrier to water. The epidermis is permeable to water in both its deeper and most superficial portions but is impermeable from either direction at the level of the granular layer. There are no zonulae occludens in the epidermis. 5. Which of the following are NOT specialized cell types of the epidermis? Langerhans cells Mullers cells melanocytes Merkel cells all of the above are found in the epidermis Very good. No, the answer is B. Mullers cells are supporting cells found in the retina. The predominant cell type of the epidermis differentiates to produce keratin and is therefore called the epidermal keratinocyte. The keratinocyte goes through three distinct phases in its lifespan 1) growth and proliferation 2) maturation and outward displacement 3) dyshesion ( or desquamation) The other cells found in the epidermis are melanocytes, Langerhans cells, and Merkel cells. Melanocytes have a neural crest origin and reside in the stratum basale. They proclude melanin which protects the body from harmful UV radiation. Langerhans cells are thought to be of mesodermal origin. They appear as clear cells under light microscopy and on electron microscopy show racket shaped granules called Birbeck granules. Langerhans cells bear surface antigens common to most B and some T lymphocytes, monocytes, and macrophages. Merkel cells are found associated with nerve terminations (Merkel's disc) and are thought to play a role in sensation. Merkel cells have numerous cytoplasmic granules concentrated on their basal side. 6. Which of the following statements concerning melanocytes are correct? melanocytes contain tyrosinase, an enzyme necessary for the production of melanin pigments skin color is determined by the number of melanocytes present melanocytes produce melanin and distribute it to keratinocytes and hair melanocytes have two to three dendritic processes and are connected to other melanocytes by numerous desmosomes Correct. No. The first and third foils are correct. Skin color is determined by the amount of pigment (i.e., the number of melanosomes) present in the melanocytes and epidermal cells and NOT the number of melanocytes present. Melanocytes have numerous dendritic processes and have NO desmosomes as are found between other epidermal cells. 7. Which of the following statements concerning hair follicles is/are correct? the hair follicle consists of 5 layers which are from inside to outside; medulla, cortex, cuticle, internal root sheath, external root sheath hair cells, like epidermis, undergo keratinization the inner three layers of the hair follicle constitute the hair shaft there is always an arrector pili muscle connecting the hair follicle with the epidermis Very good. No. All foils are correct. The external root sheath of the follicle is continuous with the epidermis. Contraction of arrector pili muscles pulls the hair follicles vertical and results in "goose flesh". Hard keratin is formed in the cortex and cuticle; soft keratin in the medulla. Hard keratin has a higher sulfur content than soft keratin. 8. There are three recognized stages of the hair growth cycle. Which of the following stages is/are associated with the correct phase (s) and time span? catagen - resting phase, 3 to 4 months catagen - growth phase, 2 to 6 years anagen - regression phase, 2 to 3 weeks telogen - resting phase, 3 to 4 months Right. No. Only the fourth foil is correct. The correct sequence of stages and their occurences are as follows 1) anagen - growth phase, 2 to 6 years 2) catagen - regression phase, 2 to 3 weeks 3) telogen - resting phase, 3 to 4 months. 9. Which of the following statements is/are true? sebaceous glands, sweat glands, fingernails and hair follicles are all derivatives of the skin sebaceous glands produce sebum which is secreted directly into the upper hair follicle sweat glands are associated with myoepithelial cells and are important in temperature regulation the nail plate is made of soft keratin Very good. No. The first three foils are correct. The nail plate is made of hard keratin. Epithelial matrix cells at the proximal end of the nail plate multiply and undergo keratinization to form the nail. The development and growth of sebaceous glands, particularly during puberty, are stimulated by androgens and inhibited by estrogens. Sweat glands are found in high concentrations in palms and soles and increase their secretion in response to emotional stimuli. Sweat glands of the rest of the body respond to heat stress. Sweat glands are absent on the glans penis, clitoris, and labia minora. 10. Which of the following statements concerning glands is correct? endocrine glands rely on blood or lymph circulation to transport their secretion to a target organ exocrine glands are ductless exocrine glands retain their connection with the epithelial surface during development endocrine glands have ducts Right. No. The first and third foils are correct. Exocrine glands have ducts which carry their secretion to the surface while endocrine glands are ductless and depend on the circulatory system for transport of secretion. 11. Exocrine glands may be classified based on the organization of the secretory portion and the duct system portion of the gland. Which of the following glands are matched with the correct duct type/secretion type classification? crypts of Lieberkuhn - simple tubular fundic and Brunner's glands - simple branched tubular sweat gland - simple coiled tubular salivary glands and pancreas - compound tubulo-alveolar Very good. No. All foils are correct. The secretory portion of glands can be either tubular or alveolar (alveolar, acinus and sccular are all interchangeable terms). The duct portion is either simple (unbranched) or compound (branched). In addition to the matches made above, the following should be noted also Sebaceous gland - simple branched alveolar Cardiac gland of stomach - compound tubular. 12. Exocrine glands may be classified based on the cell participation in the secretory process of the gland. Which of the following modes of secretion are correctly matched to their appropriate secretory events? holocrine secretion - small portions of cell membrane are pinched off and released directly into circulation merocrine secretion - only the granule containing secretory material is secreted; neither the cell cytoplasm nor the cell membrane becomes part of the secretion holocrine secretion - after secretion the cell becomes extremely metabolically active in producing secretory product for the next round of secretion apocrine secretion - a small amount of the cell membrane or apical cytoplasm of the gland detaches with the secretory droplet Correct. No. The second and fourth foils are correct. In holocrine secretion the entire cell is released as the secretion pro- duct. No organelles remain to be recycled. Remember that exocrine glands release their secretion into ducts while endocrine glands release their products into blood or lymph circulation. 13. Which of the following glands are correctly matched with their secretion types? sebaceous glands - holocrine secretion salivary glands - merocrine secretion mammary glands - apocrine secretion salivary glands - holocrine secretion Correct. No. The first three foils are correct. 14. Another criteria for exocrine gland classification is based on the nature of secretion. Which of the following is/are true statements? mucous glands secrete a slimy, viscous material rich in carbohydrates that functions mainly in lubrication mixed sero-mucous glands undergo a process called mucoid transformation in their developmental sequence serous glands secrete a watery discharge usually containing digestive enzymes serous demilunes are the portions of the serous gland ducts that are immediately adjacent to the surface on which these glands secrete Very good. No. The first three foils are correct. In standard histological preparations mucous glands will stain lightly because the granular material is lost during tissue preparation, and their nuclei are flattened and basally located. Serous glands stain more densely due to the presence of a large amount of rough endoplasmic reticulum. Mixed sero-mucous glands contain both types of cells and their discharge includes both types of secretion. Mixed glands are formed initially as a layer of serous secretory cells covering a small intercalated duct. Some of the duct cells undergo mucoid transformation to become mucous secretory cells. Eventually this gives a mixed gland of mucous cells covered by a half-moon cap of serous cells called the serous demilune. The serous demilune is therefore associated with the gland and not the duct.