Bram Welch-Horan (tbw5) SSN Session Skin Jennifer Chang (jtc2109) Bram Welch-Horan (tbw5) October 19, 2005

Functions Protection - barrier to outside environment abrasion, moisture, UV light, microorganisms Homeostasis - maintenance of internal environment temperature, water and salts Sensation touch, temperature, pain, pressure, vibration Immune surveillance Langerhans’ cells – type of macrophage Endocrine function synthesizes vitamin D

Types of Skin Thick – covers palms of hands and soles of feet, glabrous vs. Thin – covers rest of body, mostly hairy Hairy Glabrous

3 layers Epidermis stratified squamous keratinizing epithelium Dermis papillary layer of loose connective tissue underlain by dense irregularly arranged CT Hypodermis aka subcutaneous tissue, loose CT, contains adipose tissue Subcutaneous layer corresponds to the superficial fascia

Epidermis – stratified squamous keratinized epithelium 5 Layers 1. Stratum corneum 2. Stratum lucidum 3. Stratum granulosum 4. Stratum spinosum 5. Stratum basalis

Stratum corneum Stratum granulosum Superficial keratinized layer Cells have no nuclei or organelles Sealed extracellular space Most superficial cells are sloughed off Stratum granulosum Basophilic granules of keratohyalin Promotes aggregation of keratin filaments into tonofibrils Lamellar bodies – water barrier Stratum corneum

Stratum Spinosum several cell layers thick desmosomes several cell layers thick attached by intercellular bridges (desmosomes) cells artificially pulled apart, the attachment sites give spiny appearance Langerhans’ cells found here

Stratum Basalis mitotic cell cells with melanin Mitotic cell layer, attaches to basement membrane via hemidesmosomes Cells containing melanin may be either melanocytes or keratinocytes Melanin - pigment - protection from UV rays - synthesized in melanocytes using tyrosinase - taken up by keratinocytes

Question 1 In the stratum basalis, ______ are found. They attach keratinocytes to ______. Hemidesmosomes, basal lamina Desmosomes, basal lamina Hemidesmosomes, other keratinocytes Desmosomes, Langerhans cells Lab 8, slide 2

Question 1 In the stratum basalis, ______ are found. They attach keratinocytes to ______. Hemidesmosomes, basal lamina Desmosomes, basal lamina Hemidesmosomes, other keratinocytes Desmosomes, Langerhans cells Lab 8, slide 2

Question 2 Which of the following regarding these cells is true? They are mitotic They do not have organelles They contain keratohyalin granules They synthesize melanin

Question 2 Which of the following regarding these cells is true? They are mitotic They do not have organelles They contain keratohyalin granules They synthesize melanin

Question 3 This brown substance is synthesized in which cell layer? Stratum corneum Stratum granulosum Stratum spinosum Stratum basalis

Question 3 This brown substance is synthesized in which cell layer? Stratum corneum Stratum granulosum Stratum spinosum Stratum basalis

Specialized Structures in Skin Nerve supply Hair follicles Sweat glands Sebaceous glands (Nails) (Mammary glands) (http://www.columbia.edu/~johan/images/arm.jpg)

The Dermis Papillary layer Reticular layer loose CT bv’s, nerves, lymphatics papillae into epidermis Meissner’s corpuscles Reticular layer dense CT (less cellular) eccrine sweat glands Pacinian corpuscles anatomy: Langer’s lines (Ross, 4/e, p. 425)

Cutaneous Nerve Endings (Free nerve endings) pain & temperature (Merkel’s cells) high-res. tactile sensation (in stratum basale) Meissner’s Corpuscles touch Pacinian Corpuscles vibration & pressure (Skin lab, slide 16; Cajal stain)

Meissner’s Corpuscles in dermal papillae (papillary layer of dermis) mechanoreceptors 2-point discrimination encapsulated CT capsule contrast w/ free nerve endings (Ross, 4/e, p. 412)

Pacinian Corpuscles (Ross, 4/e, p. 431)

Pacinian Corpuscles in deeper dermis & hypodermis vibration & pressure reticular layer vibration & pressure encapsulated characteristic appearance “onion” / “bull’s eye” diagnostic for dermis or hypodermis hypodermis loose CT, bv’s, fat, etc. a.k.a., subcutaneous tissue, superficial fascia (Skin lab, slide 18)

Hair Follicles epithelially derived most of body surface epidermal invagination matrix of follicle equiv. to stratum basale most of body surface body temp. regulation sebaceous glands secrete into follicle arrector pili smooth muscle “goosebumps” assists gland secretion (Ross, 4/e, p. 414)

Sebaceous Glands associated w/ hair follicle secrete sebum between shaft & follicle holocrine secretion oil-filled cells apoptose secretory product & cell debris discharged from gland sebum may be protective but is involved in acne (Skin lab, slide 21)

Eccrine Sweat Glands coiled tubular glands in dermis (reticular layer) not associated with hair follicles; widely distributed secretory portion (w/ basal lamina) myoepithelial cells contract  expel sweat ducts – cuboidal cells stratified (2 layers) corkscrew path reabsorb H2O, salt sweat is hypotonic contains H2O, salt, IgA temp. regulation (Skin lab, slide 13)

Sweat Ducts (Skin lab, slide 12)

Question 4 What is the function of this nerve ending, and which skin layer is it in? a) pain; hypodermis b) temp.; reticular layer c) two-pt. discrimination; papillary layer d) itch; epidermis (Skin lab, slide 15)

Question 4 What is the function of this nerve ending, and which skin layer is it in? a) pain; hypodermis b) temp.; reticular layer c) two-pt. discrimination; papillary layer d) itch; epidermis (Skin lab, slide 15)

Question 5 The product of the gland in this image would most likely be: a) attractive to a potential mate b) hypotonic c) mainly water d) oily and associated with cell debris (Skin lab, slide 23)

Question 5 The product of the gland in this image would most likely be: a) attractive to a potential mate b) hypotonic c) mainly water d) oily and associated with cell debris (Skin lab, slide 23)