Week 13 The Integumentary System SB

The integumentary system consists of the skin and its derivatives: hair, nails, and glands

The two primary skin layers are: keratinized stratified squamous epithelium Epidermis: superficial layer made of keratinized stratified squamous epithelium (subdivided into 4-5 layers) areolar tissuedense irregular connective tissue Dermis:consists of areolar tissue and dense irregular connective tissue (subdivided into 2 layers) Hypodermis:attaches skin to underlying structures; made of areolar tissue and variable amounts of adipose Objective 1:Structures of the Integument

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: LayerStructure Stratum corneum rows of flat dead keratinocytes Stratum lucidum2-3 rows of dead keratinocytes, found only in thick skin Stratum granulosum3-5 rows of flat keratinocytes Stratum spinosum8-10 rows of flat keratinocytes, Stratum basalesingle layer of keratinocytes; some melanocytes, and Merkel cells

Thin vs. Thick Skin

Identify as: Thin skin or Thick skin? THINTHICK

The Dermis is : 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 Reticular layer Papillary layer epidermis dermis

Papillary Layer Areolar C.T. C Collagen fibers E Elastic R Reticular fibers Reticular Layer Dense Irregular C.T. Collagen fibers Layers of the Dermis

Skin derivatives found in the dermis: Sudoriferous (sweat) glands: Eccrine Apocrine

Sudoriferous (sweat) glands Low magnification High magnification Cross section

Skin derivatives found in the dermis: Arrector pili muscle Sebaceous (oil) gland Hair Shaft Hair Root Hair Follicle Hair Papilla Hair Bulb

Hair Root (embedded) Hair Shaft (visible hair) Hair Structures

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 Arrector pili Hair Root Hair Follicle Hair shaft Hair root Hair follicle Sebaceous (oil) gland

Other important structures found in the dermis are cutaneous sensory receptors

Sensory receptors can be “encapsulated” or “unencapsulated” nerve endings Free Nerve Ending Encapsulated Nerve Ending Connective tissue capsule

Free nerve endings mediate the following sensations: Nociceptors detect pain Thermoreceptors detect heat and cold Proprioceptors detect stretch Root hair plexus detect hair movement Root hair plexusFree nerve ending in the epidermis

Encapsulated Receptors Pacinian corpuscles mediate deep pressure Meissner’s corpuscles mediate light touch

Cutaneous Sensory Receptors Meissner's corpuscle Free nerve ending Pacinian corpuscle Hair follicle receptor (root hair plexus) Identify these from models

Cutaneous Sensory Receptors

Histology Pacinian corpuscles Located deep in dermis Meissner’s corpuscles Located in dermal papilla ExternalInternal See skin models for 3-D structure and structural clarity

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

Objective 2 General Sensation Experiments

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) Distribution and Discrimination

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