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126 Cards in this Set
- Front
- Back
Name the 3 layers of skin
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epidermis
dermis hypodermis |
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Name the 5 layers of the epidermis
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stratum basale
stratum spinosum stratum granulosum stratum lucidum stratum corneum |
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Describe the epithelium of the epidermis
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stratified squamous keratinized epithelium
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Describe the connective tissues of the dermis
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dense irregular connective tissue
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Name the two layers of the dermis
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papillary layer (upper, loose)
reticular layer (lower, denser) |
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Characterize the hypodermis
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superficial fascia, loose, fatty connective tissue (not part of the skin proper)
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Name the 4 major cells of the epidermis
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keratinocytes, melanocytes, Langerhans Cells, Merkel Cells
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What is the major cell type of the epidermis?
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keratinocytes
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What defines the different layers of the epidermis?
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differentiation of the keratinocytes
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Describe the stratum basale as a whole
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the point of major cell proliferation
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Describe cell communication within the stratum basale
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connected to each other through desmosomes and connected to the basement membrane through hemidesmosomes
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Describe the cells characteristic of the stratum basale
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proliferating keratinocytes and immature post-mitotic cell
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Where do cells that are pushed out of the stratum basale go?
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to the stratum spinosum
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Describe the state of cells in the stratum spinosum
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protein synthesizing and preparing for keratinization
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Describe the shape of keratinocytes in the stratum spinosum
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large, cuboidal or polyhedral
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Describe the major protein being synthesized in the keratinocytes in the stratum spinosum
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keratins
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How does the stratum spinosum get its name?
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keratinocytes are connected to each other through desmosomes and due to artifactual shrinkage, they pull apart creating spines
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Describe the state of cells within the stratum granulosum
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the cells become flattened and storage of products becomes more important
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What are keratohyalin granules?
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aggregates of profilaggrin (phosphorylated protein needed for keratinization)
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How are keratohyalin granules visualized in the light microscope?
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deeply staining, lack a membrane
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What are lamellar bodies within the stratum granulosum?
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membrane-bound vesicles filled with lipid droplets and hydrolytic enzymes
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What is the function of lamellar bodies within the stratum granulosum?
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integral in forming the water-impermeable layer
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What layer does keratinization begin?
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stratum lucidum
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Describe the thickness of the stratum lucidum and why this is so
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Very thin because keratinization is a very rapid progress
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What is a keratinized squame?
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dead bag of highly cross-linked proteins
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What is keratinization?
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conversion of keratinocytes to keratinized squames
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Describe the composition of the keratinized squame
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2 sets of cross-linked proteins: 1 right under the plasma membrane (cornified envelope) and bundled proteins in the center
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Describe what happens to the cells organelles when keratinization occurs?
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organelles are destroyed
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What happens to the lamellar bodies during keratinization?
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contents are secreted and lipid droplets coat the plasma membrane making a water-impermeable barrier
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what happens to the keratins which have cross-linked to form the cornified envelope?
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they aggregate and become cross-linked by transglutaminase
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Describe the state of the stratum corneum
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consists of cornified squames connected to each other through desmosomes and embedded in a lipid layer
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What determines the thickness of stratum corneum
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the rate of squame production and the rate at which the cells slough off
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What is ichthyoses
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perturbations in the rate at which squames develop and get sloughed off
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What do melanocytes secrete?
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melanosomes (which contain melanin)
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What results due to melanosome synthesis impairment?
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albinism
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Describe the synthesis of melanin within the melanosome
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tyrosine is transported into melanosome vesicle, tyrosinase turns it into activated precursor which will form melanin
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Describe the intermediate step in melanin formation
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melanosomes are transported to the ends of the dendritic processes.
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Describe the final step in melanin formation
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Melanosome are secreted in an apocrine fashion, they are phagocytosed and taken to keratinocyte lysosomes, and melanin is the only part resistent to degradation.
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What is the main location of melanocytes?
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Mainly in the stratum basale with processes extending into the stratum spinosum
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What do melanocytes derive from?
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neural crest cells
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What is the function of Langerhans cells
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antigen-presenting cells
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How do the Langerhans cells accomplish their function?
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They accumulate antigens in the epidermis and travel to the lymph nodes where they present the antigen to the lymphocytes
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Describe the location of langerhans cells
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located within the nucleated layers of the epidermis (mainly the stratum spinosum)
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How can Langerhans cells be differentiated in the microscope?
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long processes extending between keratinocytes, light staining cytoplasm, indented nucleus
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Describe the originof the Langerhans Cells
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derived from the bone marrow much like the rest of the blood cells (probably similar lineage as monocytes)
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What is the function of the merkel cell?
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mechanoreceptors
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How do mechanoreceptors accomplish their function?
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contained dense-cored granules and make synaptse-like connection to sensory nerve fibers
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Describe the location of Merkel cells
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Located within the stratum basale particularly at areas of enhanced tactile perception
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How can Merkel cells be differentiated from keratinocytes?
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they can't without special stains
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What are dermal papillae?
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finger-like projections of the dermis that project into the epidermis
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What are rete ridges?
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the corresponding ridges of the epidermis that match up to the dermal papillae
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Where is the dermal papillae/rete ridges most noticeable?
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in areas that aren't hairy
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Describe the significance of the basal lamina of the epidermis
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it's typical, however autoimmune reactions to hemidesmosomes or basement membrane components results in blistering diseases
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Describe the papillary layer
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looser connective tissue, adjacent to the epidermis
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Describe the reticular layer of the dermis
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denser connective tissue, adjacent to the hypodermis
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Describe the cells of the dermis
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typical of connective tissue
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Where are the 2 main plexuses of blood vessels within the dermis located?
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between papillary and reticular layer and between cutaneous and subcutaneous layers
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In addition to the 2 venous/arterial plexuses, there is an addition 3rd plexus consisting solely of veins. Where is this located?
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within the reticular layer
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Describe the blood supply to the dermal papillae
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capillary loops follow the ridges (results in a pink color in the skin)
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Describe how thermoregulation is accomplished within the dermis
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arteriovenous anastomoses can shunt blood away in order to retain heat or it can engorge to allow the dissipation of heat.
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Describe the lymphatic organization of the dermis
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lymphatic vessels loop up into the dermal papillae and drain into one of two plexuses
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Where are the plexi located in the dermis?
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between the reticular and papillary layer and between the cutaneous and subcutaneous layers
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What two types of nerve endings do sensory nerves give rise to?
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free nerve endings and encapsulated nerve endings
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Where do free nerve ending terminate within the skin?
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in the dermis and epidermis
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Where can Meissner's corpuscles be located in the skin?
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in the dermal papillae
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What is the pilosebaceous unit?
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the hair follicle, glands, and arrector pili muscle complex
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Describe the structure of the hair follicle
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tubular invagination of the epidermis
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What is the lining of the hair follicle called?
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the outer root sheath
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Where is the hair bulb located in the hair follicle?
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at the base
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Name the cells of the hair bulb
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keratinocytes and melanocytes
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What forms the inner root sheath?
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concentric layers formed by keratinocyte proliferation
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What forms the hair shaft?
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concentric layers formed by keratinocyte proliferation
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What induces the development of the hair bulb?
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the dermal papillae at the base of the outer root sheath
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What does the dermal papillae of the hair bulb do to induce growth at the hair bulb?
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provides blood flow through the capillary loop
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Name the 2 types of dermal papillae in the skin
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dermal papillae of the dermo-epidermal junction and dermal papillae of the hair bulb
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If you were to look at a cross-section view of the hair follicle, name the layers from the outside in
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outer root sheath
inner root sheat hair shaft |
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Describe the orientation of the outer root sheath in comparison to the hair follicle
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at a 90 degree angle
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What about the outer root sheath differs from the inner root sheath and hair follicle
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derives from the epidermis, not the hair bulb
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How is the inner root sheath different from the hair shaft?
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it does not extend above the skin
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What happens to cells of the inner root sheath at the skin cell surface?
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they are sloughed off with the sebaceous gland secretion
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Describe the hair shaft
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consists of 2 to 3 layers, depending on the type of hair
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How is keratinization of the hair follicle keratinocytes different from that of the epidermis?
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1) different keratins are involved
2) cornified squames are not desquamated |
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Name the 3 phases of the hair growth
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anagen
catagen telogen |
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What is the status of hair growth in anagen?
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period of active growth
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What is happening to the hair bulb during anagen?
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hair bulb reforms and migrates deeper into the skin forming the inferior portion of the hair follicle
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What is the status of hair growth in catagen?
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regression
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What is happening to the hair bulb during catagen?
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bulb moves away from the dermal papillae and toward the surface of the skin
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What is the status of hair growth in telogen?
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resting, non-growing
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What is happening ot the hair bulb during telogen
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proximal end of the hair shaft is the keratinized remnant of the hair bulb. Hair is shed upon the beginning a new growth cycle
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What is the origin/insertion of the arrector pili muscle?
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attaches to the basement membrane of the epidermis adn the hair follicle
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What happens when the arrector pili muscle contracts?
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increases the angle between the hair follicle and the surface of the skin
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What innervates the arrector pili muscle?
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sympathetic nervous system (think of when the cat gets scared)
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Describe the sebaceous glands of the hair follicle
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simple alveolar
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Where are sebaceous glands located in reference to the hair follicle
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near the superficial aspect
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What is the function of sebaceous glands?
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to secrete lipids into the hair shaft and the surface of the skin
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What regulates the development of the sebaceous glands?
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sex steroids
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What is the cause of acne vulgaris?
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inflammation of the sebaceous glands
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What method do sebaceous glands use to secrete their fluid?
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holocrine secretion
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Describe the process of developing secretory material in the sebaceous gland
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immature cells near the basal lamina, they mature and get pushed out where they accumulate lipid droplets, then they move to the end of the gland where they undergo apoptosis and the material is dumped into the space
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Describe the pattern of size of the sebaceous glands
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vary depending on region
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What are the 2 major sweat glands of the integument system
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apocrine and eccrine
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What is the shape of the sweat glands of the integument system
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simple unbranched coiled tubular
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Where are eccrine sweat glands located?
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throughout the body (not with the hair follicles)
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What is the major function of eccrine sweat glands
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thermoregulation
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Where are apocrine glands typically found?
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within the pilosebaceous unit in the anogenital region, axillae, and areola
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Describe the development of apocrine sweat glands
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become active around puberty
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Name the epithelium of the excretory ducts of the eccrine and apocrine sweat glands
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stratified cuboidal
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What is a specialized cell located within both the eccrine and apocrine epithelium?
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myoepithelial cells
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How do eccrine and apocrine sweat glands differ?
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based on their secretion and the types of secretory cells
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Classify mammary sweat glands
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modified apocrine sweat glands
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How do mammary glands receive their blood supply?
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from the surrounding skin
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Describe the support tissue of the parenchyma cells of the mammary gland
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adipose tissue of the hypodermis
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When do the mammary glands become active? What causes this?
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Like apocrine glands, they become active at puberty due to the influence of sex steroids
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How are mammary glands similar to apocrine glands
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same secretory cells, same structure of acini and duct system, both contain myoepithelial cells
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Describe the type of secretion used by the mammary gland
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holocrine for proteins, apocrine for lipids
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How does secretion of mammary gland product occur?
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secretory endpiece continuously synthesize product and it backs up into the lumen. Myoepithelial cells contract and propel product out of the duct
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What causes the myoepithelial cells to contract?
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oxytocin from the posterior pituitary
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Describe the lobular composition of the mammary gland
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composed of 15-20 lobes which all open into the nipple
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What is the lactiferous duct?
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the main duct in the mammary gland
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What is the epithelium of the lactiferous duct?
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stratified squamous
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What is the lactiferous sinus?
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the slight dilation just prior to the opening of the lactiferous duct
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Describe the epithelium of ducts feeding into the lactiferous sinuses
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stratified cuboidal
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Where are myoepithelial ducts found in the mammary gland?
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in the epithelium between epithelial duct cells in the basal lamina
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What changes occur in the mammary gland due to pregnancy?
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terminal parts of the lactiferous ducts develope secretory acini
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When does secretion of the secretory acinus product begin in the mammary gland?
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after parturition
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What changes does the mammary gland undergo upon weaning?
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secretory acinus undergoes apoptosis and become phagocytosed
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