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Week 13 The Integumentary System 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 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 Number of rows are less in thin skin and more in thick skin Thin vs. Thick Skin Identify as: Thin skin or Thick skin? THICK THIN 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 Cross section 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) The cutaneous sensory receptors are nerve endings that receive stimuli from the external environment through the skin (Exteroceptors) Spinal cord Cutaneous Sensory Receptors 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 Note: Although a part of the nervous system, cutaneous receptors can have a direct impact on the integument Consequences of Sensation Loss Diabetic neuropathy Nerve damage due to decreased blood flow •Ulcers and infections - skin damage undetected •Charcot's Joint (neuropathic arthropathy) •Loss of motor function Consequences of Sensation Loss Leprosy (Hansen’s disease) Lesions and infections from inability to detect tissue and bone injury resulting from nerve damage caused by the bacterium Mycobacterium leprae Appendage loss due to infection Blindness and nasal collapse also result from nerve damage Objective 2 General Sensation Experiments 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)
