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Week 13 The Integumentary System OBJECTIVES • Skin Histology: Identify the structures of the integument using prepared slides & models • Experiments and analysis: – Compare the density of eccrine sweat glands on 4 different body areas – Collect and analyze data on somatic sensory receptors The integumentary system consists of: • The Skin • Its Derivatives – Hair – Nails – Glands Objective 1 Structures of the Integument Skin Layers The two primary skin layers are: Epidermis: superficial layer made of keratinized stratified squamous epithelium (subdivided into 4-5 layers) Dermis: consists of areolar tissue and dense irregular connective tissue (subdivided into 2 layers) Plus: Hypodermis: attaches skin to underlying structures; made of areolar tissue and variable amounts of adipose The Epidermis is: • The superficial layer of the Integument • Composed of keratinized stratified squamous epithelium • Majority of cells are called keratinocytes • Avascular The epidermis has either 4 or 5 cell layers Thin skin has 4 layers; the stratum lucidum is absent Thick skin of the palms and soles of the feet has 5 layers Layers of the Epidermis: Mnemonic? Come Let’s Get Some (Bread/Brains/Beer…) Layer Structure Stratum corneum 20-30 rows of flat dead keratinocytes Stratum lucidum 2-3 rows of dead keratinocytes, found only in thick skin Stratum granulosum 3-5 rows of flat keratinocytes Stratum spinosum 8-10 rows of flat keratinocytes, Stratum basale single layer of keratinocytes; some melanocytes, and Merkel cells Thin vs. Thick Skin Pigmented Skin Melanocyte cytoplasm are unstained and appear white Melanosomes (w/ melanin) are stained dark Identify as: Thin skin or Thick skin? Pigmented or Non-pigmented skin? THIN THIN, PIGMENTED THICK The Dermis Dermal papillae Dermis The Dermis is: epidermis • Deep to the epidermis • Composed of connective tissue • Consists of a superficial papillary layer and a deep reticular layer • Contains sensory receptors, nerve fibers, glands, and hair follicles Papillary layer Reticular layer dermis Layers of the Dermis Papillary Layer Areolar C.T. • Collagen fibers • Elastic • Reticular fibers Reticular Layer Dense Irregular C.T. • Collagen fibers Skin Derivatives Hair shaft Pore Sebaceous (oil) gland Arrector pili muscle Hair root Hair follicle Hair bulb Hair papilla Eccrine (sweat) gland Skin derivatives found in the dermis: Sudoriferous (sweat) glands: Eccrine Apocrine Sudoriferous (sweat) glands Low magnification High magnification Skin derivatives found in the dermis: Hair Shaft Arrector pili muscle Sebaceous (oil) gland Hair Root Hair Follicle Hair Bulb Hair Papilla Hair Structures Hair Bulb Hair Shaft (visible hair) Hair Root (embedded) Histology – Hair Structures Hair Root Hair Follicle Hair Bulb Hair Papilla Histology – Arrector pili muscle (smooth muscle) Histology – Hair Structures Hair follicle Histology – Hair Structures Sebaceous (oil) gland Histology – Hair Structures Sebaceous (oil) gland Hair shaft Hair root Hair follicle Arrector pili Sebaceous (oil) gland Hair Root Hair Follicle Cutaneous Sensory Receptors Identify these from models Meissner's corpuscle Free nerve ending Pacinian corpuscle Hair follicle receptor (root hair plexus) Histology Pacinian corpuscles Meissner’s corpuscles Located deep in dermis Located in dermal papilla External See skin models for 3-D structure and structural clarity Internal Objective 3 General Sensation Experiments The cutaneous sensory receptors are nerve endings that receive stimuli from the external environment through the skin (Exteroceptors) Spinal cord Distribution and Discrimination Experiment A – 2-Point Discrimination Determine touch receptor density Experiment B – Mapping Temperature and Touch Receptors Compare density of cold, heat and touch receptors Experiment C – Tactile Localization Localizing the stimulus (receptive field) ? cm Adaptation Experiment D – Sensory Adaptation Timing pressure sensation adaptation Experiment E – Temperature Receptor Adaptation Compare sensation of hand immersed in hot water with sensation of hand already immersed (adapted)
