Histology Exam 2

26 flashcards · Biology · by Jared Blackwell

  1. Describe the Epidermis

    Stratified squamous keratinized epithelium. Avascular. Cells of epidermis: Keratinocyte, Melanocyte, Langerhans cell, Merkel cell. Renewed by mitosis 2-4 weeks. Epidermal ridges (blue) keeps epidermis attached to dermis.

  2. Describe the Dermis

    Fibrous connective tissue. Highly vascularized (red arrows), nourishes epidermis. Mostly type I collagen; some elastic fibers. Two layers. Dermal papilla (red) helps epidermal ridges bind epidermis & dermis.

  3. Two layers of Dermis

    1) Papillary Layer: loose connective tissue, thin fibers, nourishes, supports, and defends epidermis. 2) Reticular Layer: Dense irregular CT, thick fibers, gives strength and elasticity to skin.

  4. Keratinocyte. Makes up most of Epidermis. Form a protective water barrier. Euchromatic nucleus, prominent nucleus, acidophilic cytoplasm (stains very pink).

  5. Layers of Hair Follicle. Root sheath, cortex, medulla, cuticle. Hair: Root sheat, cortex, medulla, cuticle.

  6. Langerhans cell. Antigen-presentation. Specialized macrophage in connective tissue. Comes from bone marrow. Clear cytoplasm. Use immunostaining to identify langerhans cells in stratum spinosum - show up yellow/orange dots. Birebeck granules looks like a tennis racket under TEM. Breakdown and Endocytosis of viruses.

  7. Merkel Cell Sensory cell, mechanoreceptors for fine touch. Clear cytoplasm only in stratum basale. Dense granules - neurotransmitters. T - Synapse with nerve ending. Cell + nerve ending = sensory receptor - Merkel (tactile) disk.

  8. Stratum Basale Always a single layer of cells that sit on basement membrane. Mitotically active cells that push cells up. Cytoplasm full of free ribosomes to synthesize protein keratin. Basal cell carcinoma most common but least dangerous skin cancer.

  9. Stratum Spinosum "Spiny-looking" keratinocytes. The "spines" form when cells shrink during slide prep. Has the most layers of kerantinocytes. Keratins are assembled into tonofibrils (intermediate filament) that anchors into desmosomes (yellow arrow). Squamous cell carcinoma.

  10. Stratum Granulosum Final stage of living cells. Full of basophilic granules. Dark staining dots called keratohyaline granules (Yellow arrows) that link tonofibril together. Secrete lamellar bodies - lipids that surround keratanocytes and create water resistance envelope. Electron dense.

  11. Stratum Corneum No nucleus or organelles. Dead cells are packed with keratin - acidophilic. Dead cells are surrounded by lamellar bodies (coat of lipids) provides water resistant.

  12. Blue arrow.

    Stratum Lucidum Only found in thick skin. Pale staining line between stratum granulosum and stratum corneum.

  13. Melanocyte. Found in stratum basale. Forms skin pigment via melanin. Look for round cells with clear cytoplasm because NO keratin (under LM) NO desmosome attachment. Can develop a melanoma due to lack of desmosomes. Not epidermal in origin, instead, they are embryonic neural crest cells that migrate to stratum basale. Electron dense Melanosomes that are far from nucleus. When it is a melanocyte. Inside a keratinocyte, it is near the nucleus to protect nucleus from DNA & UV radiation.

  14. Melanosome transported to tips of cytoplasmic processes. Donates part of cytoplasm = cytocrine secretion. Pigment donation via melanosomes come from stratum basale to protect mitotic stem cells.

  15. Describe skin color and melanin.

    In light skin people, melanins are degraded at a faster rate. UV radiation accelerates production of melanin granules NOT melanocytes. The number of melanocytes is similar in all people. The type of melanins and rate of melanin degradation is different.

  16. Meissner's corpuscle Found in the dermis. Common in lips, palms, soles of feet. Found in dermal papilla. Messy appearance - nerve fiber + Schwann cells form a tight spiral. Senses light touch.

  17. Pacinian corpuscle Found much deeper in dermis, sometimes in hypodermis. Very large, looks like a cut onion. Has: 1) nerve fiber 2) connective lamellae of schwann cells + collagen 3) CT capsule. Senses deep pressure and vibration.

  18. What are epidermal appendages

    Derived from epithelial cells but enter into dermis. Hair follicles, sweat glands, and sebaceous glands.

  19. Hair Follicle Blue: a root sheath that goes downward through basale and spinosum layers. Green: Duct of sebaceous gland Red: Dermal papilla. Yellow: Hair bulb terminal dilation, nourished by dermal papilla. In hair bulb, Keratinocyetes divided to form a matrix and grow upwards to form hair shaft (black arrow).

  20. Arrector pili muscle. Smooth muscle that pulls hair erect "goosebumps." Blue: Follicular buldge region of outer root sheath with reserve stem cells & melanocytes. -Regenerate wounded epidermis and damaged follicle or glands.

  21. Sebaceous glands Produce sebum which is a mix of lipds and cellular debris. Helps maintains skin and hair texture. Thick skin NO sebaceous glands (palms and soles of feet). Most abundant on face, forehead, and scalp. Always between arrector pili muscle and follicle. Exocrine gland composed of compound acinar gland connected to hair follicle. Poor staining cytoplasm because of lipid. Holocrine secretion cell dies and contributes to secretory product (sebum).

  22. Eccrine sweat glands Secrete water rich sweat for temp. regulation. Pseudostratified epithelium: -clear arrow: produce sweat -dark yellow: line lumen, secrete antimicrobials. Yellow: Myoepithelial cell. On top of basement membrane. Packed with actin, acidophilic. Contraction to expel sweat. Narrow lumen, water sweat NOT stored.

  23. Apocrine sweat glands Arrow: myoepithelial cell, contracts and expels sweat. Protein rich sweat. Begins at puberty and restricted to axillary and pernineal skin. Simple cuboidal epithelium. Large/wide lumen that stores sweat.

  24. What does thin and thick skin refer to?

    Refers to relative thickness of stratum corneum.

  25. -Basal Lamina. -Statum basale -Stratum spinosum -Stratum granulosum -Stratum coreneum -Exfoliation Stratum basale (constant cell mitosis, pushes up mature keratinocytes) --> Spinosum --> Granulosum (layers based on distinct maturation)--> Corneum (Keratinocytes fill with keratin, lose nucleus, and die) --> Exfoliation (desomsome loosens).

  26. Birbeck granule of Langerhans cell. Breakdown and Endocytosis of viruses. Formation of birbeck granules allows breakdown of HIV via receptor-mediated endocytosis. Without birbeck granules, Langerhans cell becomes HIV incubator.