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BIOL 302 – Integument

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University of Waterloo
BIOL 302
Mungo Marsden

BIOL 302 – Histology – Tissues: Integumentary System Functions  Protective barrier: physical, chemical, biological, moisture  Thermoregulation: evaporation, heat radiation, insulation  Excretion: salts, urea  Metabolism: vitamin D precursors  Sense perception: touch Skin Structure  Epidermis o Surface o Epithelium o No blood vessels  Dermis o Connective tissue o Blood vessels o Sweat gland ducts o Hair follicle roots o Sensory receptors  Hypodermis o Deepest layer o Adipose tissue o Connective tissue o Sweat glands Epidermis  Keratinized simple squamous epithelium  Layers of progressively differentiating keratinocytes o Stratum corneum (upper)  Dead, flattened cell layer  Flakey appearance  For protection – dead cells are sloughed off  Stratum lucidium – bright staining layer between corneum and granulosum o Stratum granulosum  Only 3-5 cells deep  Dark staining  Dying nucleus – starting to disappear  Cells acquiring keratohyaline granules o Stratum spinosum  Thick layer  Some mitosis, flattened cells  Langerhans cells (immune) - macrophages  Spiny layer due to desmosomes  Bright line can be seen around cells o Stratum basale (lower)  Single layer  Sits on basal lamina, connects to dermis  Keratinocyte stem cells – mitotic  Melanocytes – synthesize melanin, look empty  Desmosomes and hemidesmosomes  Accessory Cells o Merkel cells  Touch  Stratum basale o Melanocyte  Clear, round  Transient cell: Makes pigment then loses contact and moves into stratum spinosa and dies. Makes the pigment then transfers it to keratinocytes. Increase uptake of melanin by keratinocytes.  Upon exposure to UV light, increase in melanin, increase branching and increase uptake. o Langerhans cells  Clear cell  Branching  In stratum spinosa Dermis  Dense irregular connective tissue  Vascularized, nerves (sensory receptors)  Epidermal specialization: hair, sweat glands, sebaceous glands  Dermis comes in two layers: layer looks less dense and layer that looks less dense o Lower layer – Reticular  Dense irregular connective tissue  Vascularized  Lots of collagen, some elastin o Upper layer - Papillary layer  Dense irregular tissue, but more loose – different thickness of collagen fibres  Elastin fibres  Papillae Hypodermis  Unilocular adipose connective tissue – stores energy  Major blood vessels – medium arteries and veins  Glands and ducts  Keratin stem cells Sensory Receptors  Epidermis o Merkel cell - high resolution o Bare nerve - pain, itch, heat  Dermis o Meissener’s corpuscle – light touch  Hypodermis o Pacinian corpuscle – deep vibrations Projections  Papillae – dermis  Epidermal ridges – epidermis Epidermal Derivatives  Sweat Glands o Simple tubular exocrine gland - secrete throughbio-duct o Merocrine secretion – through exocytosis, water secretion from clear cells and mucous secretion from dark c
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