Skin Practical part Dr. Heba Kalbouneh Associate Professor ofAnatomy and Histology ##PLEASE NOTE: The doctor mentioned at the beginning that the lab slides required for the exam are those mentioned at the end of lec 2 Histology. Writer: Ghazal Al-Attiyat Skin of eyelids a and the back!!! Kalbouneh Heba Dr. Types of skin Kalbouneh Heba Dr. Thin skin Thick skin *4 layers *5 layers *less Prominent *Prominent stratum stratum corneum corneum * Less developed * Well developed stratum granulosum stratum granulosum *Dominant and *Palms of the hands lines most of the and soles of the feet body surface * Thinner dermis * Thicker dermis * No hair and * hair and sebaceous sebaceous glands glands The skin is composed of two layers: the outer epidermis and the deeper dermis, both of which rest on the hypodermis Kalbouneh Heba Dr. Stratum corneum Stratum granulosum Melanin granules Kalbouneh Stratum spinosum Dermal papilla Heba Stratum basale Epidermal ridge Dr. Stratum corneum Stratum granulosum Stratum spinosum Stratum basale Duct of eccrine sweat gland Kalbouneh Heba Dr. Stratum basale Stratum spinosum Kalbouneh Heba Dr. Stratum Spinosum→ the cells are connected by spines Epidermal (rete) ridges Dermal papillae Kalbouneh Heba Dr. **It is Thick skin →has stratum lucidum (light stained stratum) #When the prominent interdigitations are → prominent stratum corneum prominent, this causes friction ridges on the → No hair follicles outer skin → prominent granulosum layer → prominent papillae ** Thick skin Prominent stratum granulosum No apocrine sweat glands, sebaceous glands or hair follicles thick stratum corneum Dr. Heba Kalbouneh ** Thin skin Thin stratum corneum Not prominent stratum granulosum Can find sebaceous gland→ so there is a hair follicle not seen in this section The papillae are not prominent The normal histologic appearance of the skin is shown here. At the top is the epidermis.A thin layer of keratin overlies the epidermis. This layer of keratinization is thicker on the palms and soles and in areas where skin is rubbed or irritated. Beneath the epidermis is the dermis containing connective tissue with collagen and elastic fibers.At the center can be seen a hair follicle with surrounding sebaceous glands. Associated with the hair follicle is a small bundle of smooth muscle known as the Kalbouneh arrector pili that can cause the hair to "stand on end" and dimple the skin to form Heba "goose bumps". Dr. Skin section: keratin, epidermis The hair shaft isn’t seen because we lose it during section preparation Sebaceous glands → small cells, light stained because the sebum isn’t stained with H&E A small nucleus in the center of the cell Kalbouneh Heba Dr. Sebaceous gland Hair root Inner root sheath Arrector pili Outer root sheath Glassy membrane Dermis Dermal sheath Sweat gland Hair matrix (ducts) Dermal papilla Sweat gland (secretory cells) Hair bulb * ducts → dark stained, stratified cuboidal #It’s not required to differentiate between epithelium apocrine and eccrine sweat glands * secretory → light stained, single layer of **except if we’re given 2 histological section cuboidal epithelium next to each other A: Dermal papilla B: Hair matrix Melanocytes: Attached to basal lamina by hemidesmoses Not attached to neighboring keratinocytes Lightly stained cytoplasm > Found in stratum basale 1 melanocyte for every 10 basal keratinocytes Kalbouneh Heba Dr. Melanocyte Under the light microscope: The outline of the cell is rounded → because its processes don’t appear in histological preparation → It undergoes shrinkage during histological preparation → it is not attached to neighboring keratinocytes Dr. Heba Kalbouneh Freckles are clusters of concentrated melaninized cells Freckles do not have an increased number of the melanin-producing cells, or melanocytes, but instead have melanocytes that overproduce melanosomes changing the coloration of keratinocytes Kalbouneh Heba Dr. → larger and more active melanocytes Is there anything abnormal in the epidermis? If so, what might it indicate. Look for cells with pale cytoplasm in the epidermis. These cells are melanocytes and the large number of melanocytes in upper layers of epidermis is abnormal. In normal skin, melanocytes are found only in the basal layer of the epidermis. The condition suggests the Kalbouneh early stages in the development of melanoma. Heba Dr. We do immunohistochemistry against melanocytes in order to getthe dingnosis Langerhans cells: Originate from bone marrow (monocytes) Mainly in the stratum spinosum Langerhans cells recognize, phagocytose, and process foreign antigens Kalbouneh Heba Dr. Langerhans cells → rounded cells, lightly stained cytoplasm, with processes Dr. Heba Kalbouneh Melanocytes and Langerhans Cells Melanocytes localize to the stratum basale and extend processes between the keratinocytes of the stratum basale and spinosum. Melanocytes produce the pigment melanin that protects against ultraviolet radiation. Melanin is produced in membrane-bound organelles called melanosomes that derive from the Golgi. Melanosomes are transported to the ends of the melanocyte Melanocyte processes where neighboring keratinocytes phagocytose the Kalbouneh Langerhansmelanosomes.cell Langerhans cells are antigen-presenting cells in Keratinocyte Heba the immune system. Dr. Melanocytes :according to the location Sweat glands **apocrine sweat glands secrete in both modes of secretion: merocrine and aprocrine 21 Dr. Heba Kalbouneh Sweat Glands Eccrine sweat gland Apocrine sweat gland . Merocrine secretion . Empty into hair follicle . Empty directly onto skin surface . Location: armpits, groin, nipples . Viscous, cloudy secretion good . Location: most all over body (esp. nutrient source for bacteria (odor !!) abundant on palms & soles: ~ 500/cm2) . Secretion may contain Pheromones . Secretion begins at puberty and is . Clear, watery secretion (99% stimulated during emotional distress H2O; rest NaCl + some waste Scent glands products Kalbouneh Heba Dr. → simple coiled tubular glands: when a section is taken we find rounded: • Dark stained: duct • Lightly stained: secretary portion Apocrine sweat glands Eccrine (merocrine) sweat glands Kalbouneh 24 Heba Sweat glands appears rounded profiles within the epidermis: Dr. Apocrine larger in size with wide lumens in comparing with eccrine sweat glands. Apocrine sweat gland Eccrine sweat gland Kalbouneh Heba Dr. *Once I see the hair follicle , I realize it’s a skin This section is taken from axilla, genital a skin section area (where we have apocrine sweat ** The hair follicle is surrounded by glands) adipocytes, then the hair follicle extends down in the dermis ** Can’t be taken from the scalp because it doesn’t have apocrine sweat glands Apocrine or eccrine sweat glands???? Kalbouneh Heba Dr. Apocrine: Because the apical surfaces of • Eccrine sweat glands are seen in thin and the cells have apocrine mode thick skin, not only thick skin of secretion (separation of apical part of cells) Apocrine or eccrine sweat glands???? A: Duct B: secretory portion • Apocrine sweat glands: → wide lumens → not clear apical part of cells (separation of apical part) Meissner's corpuscles localize in the dermis between epidermal ridges. Meissner's corpuscles are touch receptors and enriched in fingers and toes Kalbouneh Heba Dr. Meissner’s corpuscle → according to its shape and location Dr. Heba Kalbouneh Meissner’s corpuscle Dr. Heba Kalbouneh Pacinian Corpuscle Pacinian corpuscles are large (~ 1 mm), onion-like structures in the dermis and hypodermis. Pacinian corpuscles contain a myelinated nerve ending in the central core of the structure. Pacinian corpuscles are sensitive to mechanical and vibratory pressure, Kalbouneh rapidly changing pressure Heba Dr. Kalbouneh Heba Dr. Sweat glands Pacinian corpusle Nerve Adipocytes Ring shaped cells: white adipocytes • This section is taken from: deep part of the reticular layer of dermis • eccrine sweat glands Meissner corpuscle Epidermal ridge Dermal papilla Kalbouneh Heba Dr. Pacinian corpuscles Kalbouneh Heba **In the center of Pacinian corpuscles! There is sensory nerve ending Dr. surrounded by connective tissue capsule forming the corpuscle Pacinian corpuscles Dr. Heba Kalbouneh The junction between dermis and epidermis Sebaceous gland Hair follicle Hair shaft/root /Hair fiber Arrector pili Dermal papilla Pacinian corpuscle Hair matrix Kalbouneh Sweat gland Heba Dr. Sebaceous gland Hair follicle Kalbouneh Arrector pili Heba Dr..