_ch_05_lecture_presentation (1) - CHAPTER 5 INTEGUMENTARY...

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INTEGUMENTARY SYSTEM CHAPTER 5
Integumentary System It consist of Cutaneous Membrane and Accessory Structures
Skin (Integument) Consists of two distinct regions Epidermis Dermis Hypodermis
Figure 5.1 Skin structure. Hair shaft Epidermis Papillary layer Dermis Reticular layer Hypodermis Dermal papillae Sweat pore Cutaneous plexus Adipose tissue Nervous structures Sensory nerve fiber with free nerve endings Lamellar corpuscle Hair follicle receptor (root hair plexus) Appendages of skin Sweat gland Arrector pili muscle Sebaceous (oil) gland Hair follicle
Epidermis Keratinized stratified squamous epithelium Four or five distinct layers Stratum basale Stratum spinosum Stratum granulosum Stratum lucidum (only in thick skin) Stratum corneum Four cell types Keratinocytes Melanocytes Dendritic (langerhans) cells Tactile (merkel) cells
Figure 5.2a The main structural features of the skin epidermis. Dermis Stratum spinosum Several layers of keratinocytes unified by desmosomes. Cells contain thick bundles of intermediate filaments made of pre-keratin. Stratum basale Deepest epidermal layer; one row of actively mitotic stem cells; some newly formed cells become part of the more superficial layers. See occasional melanocytes and dendritic cells. Stratum granulosum Typically five layers of flattened cells, organelles deteriorating; cytoplasm full of lamellar granules (release lipids) and keratohyaline granules. Stratum corneum Most superficial layer; 20–30 layers of dead cells, essentially flat membranous sacs filled with keratin. Glycolipids in extracellular space.
Keratinization is the formation of a layer of dead protective cells with protective protein Keratin Keratinocytes Tightly connected by desmosomes
Melanocytes 10–25% of cells in deepest epidermis Produce pigment melanin – packaged into melanosomes .
Tactile (merkel) cells Sensory touch receptors Associated with sensory neuron .
Dendritic (langerhans) cells Macrophages – key activators of immune system
Thin skin covers most of the body areas while thick skin is present in the plams of the hands and the soles of the feet
Cell Differentiation in Epidermis Cells change from stratum basale to stratum corneum Accomplished by specialized form of apoptosis Controlled cellular suicide Nucleus and organelles break down Plasma membrane thickens Allows cells to slough off as dandruff and dander Shed ~ 50,000 cells every minute
Stratum spinosum Stratum basale Melanocyte Dendritic cell Keratinocytes Stratum corneum Dermis Melanin granule Sensory nerve ending Tactile (Merkel) cell Desmosomes Stratum granulosum . Figure 5.2b The main structural features of the skin epidermis.
Dermis Strong, flexible connective tissue Cells Fibroblasts, macrophages, and occasionally mast cells and white blood cells Fibers in matrix bind body together Contains nerve fibers; blood and lymphatic vessels Contains epidermal hair follicles; oil and sweat glands Two layers Papillary Reticular
Figure 5.1

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