Week 13 The Integumentary System OBJECTIVES Skin Histology
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, PIGMENTED THICK
The Dermis Dermal papillae Dermis
The Dermis is: epidermis • Deep to the epidermis • Composed of connective tissue Papillary layer • Consists of a superficial papillary layer and a deep Reticular layer reticular layer • Contains sensory receptors, nerve fibers, glands, and hair follicles 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)
- Slides: 31