Week 13 The Integumentary System

The integumentary system consists of: The Skin Its Derivatives Hair Nails Glands

Objective 1 Structures of the Integument

Anatomy of the Skin video Click on title to hyperlink website This silent film from 1926 takes us through the basic physiology of the human skin, combining anatomical education and basic healthcare advice. We see the epidermis and its replacement, the structure of the underlying dermis, nails, sweat glands and hair follicles.

Skin Layers The two primary skin layers are: Plus: 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 Epidermis

The superficial layer 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: 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

High power magnification Thin skin S. Corneum S. Granulosum S. Spinosum S. Basale High power magnification

Low power magnification Thick skin S. Corneum S. Lucidum S. Granulosum S. Spinosum S. Basale Low power magnification

Comparing the two together:

Pigmented Skin

How melanin granules pigment the skin:

Melanocyte cytoplams are unstained and appear white Melanosomes (w/ melanin) are stained dark

Pigmented skin Melanin granules Melanocyte

Review: ? ? ? ? ? Identify each layer S. corneum ? S. Lucidum ? S. Granulosum ? S. Spinosum ? S. Basale How do you distinguish each layer?

Identify as: Thin skin or Thick skin?

The Dermis Dermal papillae Dermis

Composed of connective tissue epidermis 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 Papillary layer dermis Reticular layer

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

Dermal papillae not normally noticeable in thin skin as in thick skin Review: Thin skin Stratified squamous Thick or thin skin? Tissue type? Papillary Areolar CT Dermal layer? Tissue type? Reticular Dense Irregular Dermal layer? Tissue type? Dermal papillae not normally noticeable in thin skin as in thick skin

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: Arrector pili muscle Sebaceous (oil) gland Hair Structures

Connective tissue root sheath Epithelial root sheath HAIR STRUCTURES Hair shaft Sebaceous gland Hair root Connective tissue root sheath Arrector pili muscle Epithelial root sheath (Hair follicle) Hair Bulb Hair Papilla

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

Histology – Hair Structures Hair Root Hair Follicle Hair Bulb Hair Papilla

Histology – Hair Structures Hair follicle

Histology – Arrector pili muscle (smooth muscle)

Histology – Hair Structures Sebaceous (oil) gland

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

Cutaneous Sensory Receptors 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

Meissner’s corpuscles Located in dermal papilla Histology Pacinian corpuscles Located deep in dermis Meissner’s corpuscles Located in dermal papilla External Internal

Meissner’s corpuscle - Histology Located in the dermal papilla Tactile receptors = Discriminative touch

Pacinian corpuscle - Histology Located deep in the dermis Deep pressure High magnification Low magnification

Review 5 1 6 2 4 3 9 8 7 10

Review 9 5 Hair shaft 6 Meissner's corpuscle 7 Free nerve ending 8 Sebaceous (oil) gland 10 Arrector pili muscle 1 Hair root 11 Pacinian corpuscle 2 Hair follicle 3 Hair bulb 4 Hair papilla 5 Eccrine (sweat) gland 12 Root hair plexus

Objective 2 General Sensation Additional Information

Although a part of the nervous system, cutaneous receptors have a direct impact on the integument, and so will be studied in this lab

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

There are 3 ways to classify cutaneous receptors: Location ………..…………. Stimulus (physiology) Structure (anatomy)

Classifications of Sensory Receptors by Location Exteroceptors Proprioceptors Interoceptors Lab 11 BIOL 204 Respond to stimuli arising outside the body: Touch Pain Temperature Pressure Detect stretch Respond to stimuli inside the body (viscera, vessels)

Classifications of Sensory Receptors by Stimulus Nociceptors detect pain Thermoreceptors detect heat and cold Mechanoreceptors detect touch and pressure Photoreceptors detect light Chemoreceptors detect chemicals and chemical changes These are the ones you utilized in Lab 12

Classifications of Sensory Receptors by Structure Unencapsulated Encapsulated Connective tissue capsule Free Nerve Ending Encapsulated Nerve Ending

Free (Unencapsulated) Nerve Endings Free nerve ending in the epidermis Root hair plexus Detect hair movement Mechanoreceptor Phasic Detect pain, temperature, tissue movements Nociceptor (tonic) Thermoceptor (phasic) (Mechanoreceptor)

Encapsulated Nerve Endings Examples Pacinian corpuscle Meissner’s corpuscle Detect light pressure, discriminative touch, vibration Mechanoreceptor Phasic Detect deep pressure, stretch, vibration Mechanoreceptors Phasic

Distribution of cutaneous sensory receptors

Functional Mapping of Somatosensory Cortex The picture represents the sensory information covered by a particular portion of the post-central gyrus. Consider what impact this may have on the receptive fields of the different areas tested in this experiment.

Adaptation: Tonic vs. Phasic Pain Stretch Temperature Pressure Sensation diminishes but never ceases Sensation ceases (becomes unnoticeable)

Receptive Fields and Adaptation of Select Receptors Phasic Tonic Phasic Tonic