DMCH121 Lecture 1 - Normal Skin and Nail PDF

DMCH121 LECTURE 1 NORMAL SKIN & NAIL DEVELOPED BY: CESAR MENDEZ DPM FACFAS EDITED BY: ELIOT TO DCH MCLSC  Please download and install the Slido app on all computers you use Join at slido.com #1127496 ⓘ Start...

DMCH121 LECTURE 1 NORMAL SKIN & NAIL DEVELOPED BY: CESAR MENDEZ DPM FACFAS EDITED BY: ELIOT TO DCH MCLSC  Please download and install the Slido app on all computers you use Join at slido.com #1127496 ⓘ Start presenting to display the joining instructions on this slide. SKIN FACTS  Largest organ of the body  Weighing an average of 4 kg  Covering an area of 2 sq.m.  Either glabrous (smooth and without hair) or hairy https://medlineplus.gov/ency/imagepages/19679.htm THE SKIN Functions: 1. Protection (e.g., trauma, infection) 2. Sensation 3. Thermoregulation 4. Excretion 5. Metabolism (e.g., vitamin D production) 6. Social interaction https://www.bbraun.co.uk/en/patients/wound-healing/knowledge-series.html FUNCTIONS OF THE SKIN: PROTECTION  Acts as physical barrier against:  Trauma  Bacterial invasion  Excessive loss of fluids and proteins  Also protects tissues and structures from mechanical injury https://nationaleczema.org/blog/what-is-my-skin-barrier/ FUNCTIONS OF THE SKIN: PROTECTION  Skin cells involved with immune protection:  Langerhans cells  Tissue macrophages  Mast cells  Skin pigmentation protects against UV radiation  Melanin = Guard against damaged caused by UV-A (long form of UV radiation)  More predominant in dark skin vs. light skin individuals https://int.eucerin.com/about-skin/basic-skin-knowledge/skins-protective-barrier FUNCTIONS OF THE SKIN: SENSATION  Skin is filled with nerve endings that feel:  Pain  Pressure  Temperature  Nerve fibres originate from nerve roots along the spine  Supply areas of skin called dermatomes  The body’s network of dermatomes document sensory function  Loss or reduction of sensation → ↑ Chance of injury https://neupsykey.com/receptors-and-effectors/ FUNCTIONS OF THE SKIN: THERMOREGULATION  Skin regulate body temperature through an orchestrated effort involving:  Nerves  Blood vessels  Glands  Skin acts as a barrier between internal vs. external environments  When skin is exposed to cold (or when internal temperature falls):  Blood vessels constrict → Blood flow is reduced → Body heat is preserved  When skin becomes too hot (or internal temperature rises):  Tiny arteries in the skin dilates → ↑ Blood flow + sweat production → Body cools https://neupsykey.com/receptors-and-effectors/ FUNCTIONS OF THE SKIN: EXCRETION  Skin assists in thermoregulation by excretion of:  Waste products  Electrolytes  Water  More than 2 million skin pores work to release water and body wastes to the air  Each day, an adult loses about 500mL of water through the skin FUNCTIONS OF THE SKIN: METABOLISM  When exposed to sunlight, the skin synthesizes vitamin D  Then transmitted to other areas of the body  Assists in mineralization of bones and teeth https://www.sciencedirect.com/science/article/pii/S209012321400023X FUNCTIONS OF THE SKIN: SOCIAL INTERACTION  Skin has psycho-social function:  Closely linked to aspects of body image, physical attraction and communication  Damage to skin can perpetuate functional and physiologic consequences  Also, an impact on self-esteem  Please download and install the Slido app on all computers you use Which of the following is a FUNCTION of the skin? (Check all that apply) ⓘ Start presenting to display the poll results on this slide. THE HUMAN SKIN  Composed of:  Skin:  Epidermis  Dermis  Skin appendages  Sub-cutaneous fat  Fascia  Muscle https://my.clevelandclinic.org/health/body/10978-skin THE HUMAN SKIN  Layers:  Epidermis  Basement membrane/Basal lamina  Stratum germinativum  ~30 days from cell production to sloughing  Stratum spinosum  Stratum granulosum  *Stratum lucidum  Only on palms and soles  Stratum corneum  ~14 days from the bottom to shedding Baranoski, S. & Ayello, E.A. (2020). Wound Care Essentials (5th Ed.) THE HUMAN SKIN Epidermis Dermis THE HUMAN SKIN THE EPIDERMIS  Thin, outermost layer of the skin  Continually regenerate (Q21-28 days) from basal cell layer  Sheds the outermost cell layer during hand washing  Function: 1. Barrier to water loss 2. Protects against mechanical damage, chemicals and pathogens https://my.clevelandclinic.org/health/body/21901-epidermis THE EPIDERMIS (EPITHELIAL LAYER)  FOUR (five on palms and soles) strata/layers: 1. Stratum corneum 2. Stratum lucidum (only on palms and soles) 3. Stratum granulosum 4. Stratum spinosum 5. Stratum germinativum (basale)  FOUR cell types: 1. Keratinocytes = Produces keratin 2. Melanocytes = Synthesizes pigment (melanin) 3. Langerhans’s cells = Immunoreaction 4. Merkel’s cells = Mechanoreceptors Come Let’s Get Sun Burnt! THE EPIDERMIS (EPITHELIAL LAYER)  Strata/Layers:  Stratum corneum  Horny (i.e., tough) cell layer  Stratum lucidum  Palms and soles  Stratum granulosum  Granular cell layer  Stratum spinosum  Prickle cell layer  Stratum germinativum/basale  Basal cell layer https://courses.lumenlearning.com/suny-ap1/chapter/layers-of-the-skin/ THE EPIDERMIS (EPITHELIAL LAYER) THE EPIDERMIS (EPITHELIAL LAYER) https://plasticsurgerykey.com/anatomy-and-physiology-of-the-integumentary-system/ THE EPIDERMIS (EPITHELIAL LAYER) STRATUM GERMINATIVUM/BASALE  Deepest epidermal layer  Firmly attached to the underlying dermis  Single row of cuboidal keratinocytes  With melanocytes and Merkel cells interspersed  Cells in this layer are highly mitotic  I.e., They’re dividing often  A.k.a. stratum germinativum STRATUM GERMINATIVUM/BASALE https://med.libretexts.org/Bookshelves/Anatomy_and_Physiology/Human_Anatomy_%28Lang e_et_al.%29/04%3A_Integumentary_System/4.02%3A_Layers_of_the_Skin STRATUM SPINOSUM  Second deepest layer  8-10 layers of cells  Cells of the lower layers can still be mitotic  As cells get pushed upward, they begin to flatten and begin to make the precursors of keratin  A.k.a. the “prickly layer,” because in tissue sections, they shrink and pull back  Exposed desmosomes connecting adjacent cells appear to resemble spikes or spines https://labmedicineblog.com/2016/06/03/show-us-some-skin/ STRATUM GRANULOSUM  3-5 cell layers thick  Cell morphology begins to change dramatically as cells continue to flatten and their nuclei and organelles disintegrate  Accumulate granules containing a precursor of keratin + granules containing a waterproofing agent https://med.libretexts.org/Bookshelves/Anatomy_and_Physiology/Human_Anatomy_%28Lang e_et_al.%29/04%3A_Integumentary_System/4.02%3A_Layers_of_the_Skin STRATUM LUCIDUM  3-5 layers of flat, dead keratinocytes  Appears clear in the light microscope  Cells lack nuclei and organelles which typically stain well https://med.libretexts.org/Bookshelves/Anatomy_and_Physiology/Human_Anatomy_%28Lang e_et_al.%29/04%3A_Integumentary_System/4.02%3A_Layers_of_the_Skin STRATUM CORNEUM  Outermost stratum  20 – 30 layers of flat (squamous), highly keratinized, dead cells.  A.k.a. the cornified layer  The process by which cells in the stratum basale divide and then advance upward becoming more and more keratinized and less and less alive is known as cornification  Functions: 1. Protects against mechanical abrasion  Cells can absorb impacts and simply flake off if necessary 2. Prevents pathogen entry 3. Prevents desiccation (drying out) https://labmedicineblog.com/2016/06/03/show-us-some-skin/  Please download and install the Slido app on all computers you use Which of the following is the THINNEST layer of normal human skin? ⓘ Start presenting to display the poll results on this slide. THE CELLS OF THE EPIDERMIS  FOUR main cell types:  Keratinocytes  Produce keratin  Melanocytes  Synthesize pigments (melanin)  Langerhans's cells  Immunoreaction  Merkel’s cells  Mechanoreceptors https://quizlet.com/182377832/histology-skin-flash-cards/ KERATINOCYTES  Most numerous epidermal cell  Found in all layers of the epidermis  Tightly connected to one another by desmosomes  Provides continuity, strength, and protection  Is the reason skin flakes off in sheets rather than as individual cells  Chief function is the production of keratin  Tough fibrous protein → Gives strength and confers a lot of protective ability https://www.news-medical.net/health/What-is-the-Epidermis.aspx KERATINOCYTES  New cells are continuously made in the deepest layer pushing the older cells up  As the keratinocytes move farther from the deepest layer, they make the keratin that eventually dominates their cell contents  When they have reached the upper layer, they are nothing more than scale-like bags of keratin https://theory.labster.com/keratinocyte/ MELANOCYTES  Spider-shaped epithelial cells that synthesize the protein pigment melanin  Found in the deepest layer of the epidermis  Melanin is made and then packaged into membrane-bound granules called melanosomes  Granules are transferred to the keratinocytes in the 2 deepest layers of the epidermis MELANOCYTES  Melanin granules accumulate on the “sunny side” of the nucleus of the keratinocytes  Melanin granules protect the DNA within the nucleus from being damaged by the ultraviolet radiation from the sun MELANOCYTES https://www.researchgate.net/figure/In-the-skin-epidermis-melanocytes-produce-the-pigment- melanin-in-organelles-called_fig3_371168151 MERKEL CELLS  Clear cells found in the stratum basale/germinativum  Connected to other skin cells by desmosomes  Each Merkel cell is connected to an afferent nerve terminal  Forms the Merkel disk  Most plentiful in the basal layers of:  Fingers, toes, lips, oral cavity and outermost sheath of hair follicles (i.e., touch areas) https://www.cancer.gov/publications/dictionaries/cancer-terms/def/merkel-cell MERKEL CELLS  Exact function is unclear → Believed to be neuroendocrine  I.e., Release hormones into the blood in response to neural stimuli  Slowly adapting sensory touch receptors in cutaneous sensation  May also be involved:  Metabolic support of associated neurons  Neuron development and regeneration after injury  Neurotransmission for autonomic nerves, blood vessels and inflammatory cells https://www.nature.com/articles/nature13250 LANGERHANS CELLS  Scattered in the suprabasal layers of the epidermis among keratinocytes  Less numerous (3-5% of epidermal cells) than keratinocytes  Derived from bone marrow → Continuously repopulate the epidermis https://pubs.rsna.org/doi/10.1148/rg.283075108  Dendritic shape (like melanocytes) with clear cytoplasm  Contains Birbeck granules (looks like tennis racquets) = Distinguishing feature https://www.sciencephoto.com/media/426167/view/langerhans-cell-tem LANGERHANS CELLS  Immunologic function  Recognize foreign antigens  Bind antigen to their surface and process it  Bear the process antigen and migrate into lymphatics Grossman & Porth. (2014).  Become known as Dendritic cells when inside the regional lymph node  Become antigen-presenting cells  Innervated by the autonomic nervous system  I.e., Skin’s immune system is altered under stress  E.g., Acne when people are under stress  Please download and install the Slido app on all computers you use Which of the following statements is/are FALSE? (Check all that apply) ⓘ Start presenting to display the poll results on this slide. THE DERMIS  Thickest skin layer  Strong, structural matrix  Composed of three major protein fibers → Provides mechanical strength to skin  Collagen, elastin and reticular  Consists of blood vessels, nerves, hair, nails and skin glands  Function(s): 1. Provides support and nutrition to the epidermis 2. Regulates heat, immune response and sensation (receptors for pain and cold sensations) https://my.clevelandclinic.org/health/body/22357-dermis THE DERMIS – PAPILLARY & RETICULAR LAYERS  The papillary dermis is the upper 1/5 of the dermis  Consists of loose (areolar) CT  Provides an arena for immune cells to fight invaders  Projects upward (as dermal papillae) to interdigitate and form a strong connection with the epidermis  Heavily invested with blood vessels – they constrict in cold weather and dilate in warm weather  Also contains multiple sensory receptors https://med.libretexts.org/Bookshelves/Anatomy_and_Physiology/Human_Anatomy_%28Lang e_et_al.%29/04%3A_Integumentary_System/4.02%3A_Layers_of_the_Skin THE DERMIS – PAPILLARY & RETICULAR LAYERS  Rete ridges:  Undulating microstructures at the epidermal-dermal junction https://www.sciencedirect.com/science/article/abs/pii/S1742706122007589 THE DERMIS – PAPILLARY & RETICULAR LAYERS  Reticular dermis is lower 4/5  Consists of dense irregular connective tissue  The prominent, horizontally running collagenous fibres  Give the skin strength and resiliency  Elastin gives the skin the ability to stretch and recoil  The majority of the appendages of the skin are contained within the dermis Red = Papillary Blue = Reticular THE DERMIS – PAPILLARY & RETICULAR LAYERS  Dermal matrix:  Collagen  Elastin  Ground substance (proteoglycans)  Epidermal appendages  E.g., Sweat glands, hair follicles etc.  Neurovasculature THE DERMIS  Collagen and elastin  Provide support to the dermis  Together determines the skin’s physical characteristics  Collagen in the papillary layer of the dermis are non-elastic  Provides high tensile strength  ~70% of skin’s dry weight = Collagen  Wavy elastic fibers interconnect with collagen in the lower dermis and at the epidermal margin  Allows skin to remain pliable, and enables extensibility in the dermis  Please download and install the Slido app on all computers you use The dermis: (Check all that apply) ⓘ Start presenting to display the poll results on this slide. THE SUBCUTANEOUS LAYER  Composed of adipose (fatty) connective tissue  Located directly beneath the dermis  Fat cells (lipocytes) are separated by fibrous septa  Traversed by blood vessels, nerves, and lymphatics  Function(s): 1. Insulates from heat and cold 2. Absorbs shock 3. Acts as caloric reservoir → Used during illness or starvation  Thins considerable during aging ADNEXA  Adnexa = Area which houses the following:  Glands  Vessels  Nerves  Hair  Nails https://www.researchgate.net/figure/Prominent-skin-adnexal-structures-Adapted-from- Anatomy-of-the-Skin-by-Biorendercom_fig1_358208577 SEBACEOUS GLANDS  Simple alveolar glands found everywhere  Except palms of the hands and soles of the feet  Secrete an oily, lipid-rich secretion called sebum  Fun fact: Lanolin is actually sheep sebum  Typically secreted into a hair follicle or occasionally onto the body surface  Softens and lubricates the skin  Also decreases the skin’s permeability to water and is quite bactericidal ECCRINE SWEAT GLANDS (SUDORIFEROUS GLANDS)  Two types (both merocrine):  Eccrine sweat glands (onto skin surface)  Apocrine sweat glands (into hair follicle)  2 to 3 million over body surface  Not in mucous membranes, nail beds, nipples and portions of the external genitalia  Maximally distributed on palms and soles  Functions: 1. Respond to psychogenic and thermal stimulation 2. Regulates body temperature (by excreting sweat to the skin surface) MEROCRINE SWEAT GLANDS  Mecocrine gland = Organ that secretes chemicals without damaging its own cells  Eccrine more numerous than apocrine sweat glands  Especially prominent on the palms, soles, and forehead  Simple, coiled, tubular glands  Duct empties into a funnel-shaped pore at the skin surface.  Major function of merocrine sweating is to cool the body (thermoregulation) https://www.researchgate.net/figure/Basic-structure-of-sweat-glands-The-eccrine-sweat-gland-is_fig1_318503906 THE ACID MANTLE  Eccrine sweat is a dilute watery solution of some salts (including NaCl), vitamin C, antibodies, small amounts of nitrogenous wastes (urea, uric acid, and ammonia), and lactic acid  pH of sweat is 4-6 creating a film on the body known as the acid mantle  Such an acidic environment is bacteriostatic (prevents bacterial reproduction/growth) https://goodieco.com/blogs/goodieco/what-you-need-to-know-about-your-skin-barrier-and-why-you-should-care VASCULATURE OF THE SKIN  Arranged into THREE horizontal plexuses that are interconnected 1. Superficial vascular plexus in the papillary- reticular junction 2. Deep vascular plexus in the lower reticular dermis 3. Subcutaneous plexus (larges and deepest)  Functions: 1. Temperature regulation 2. Blood pressure regulation 3. Nutrition https://www.researchgate.net/figure/Cutaneous-vasculature-a-A-diagram-of-healthy-skin-highlighting-three-primary-layers_fig1_330451590 HAIR AND HAIR FOLLICLES  The hair follicle surrounds much of the hair root  Contains an outer connective tissue sheath + an inner epithelial root sheath.  At the base of the hair follicle is a single layer of mitotic cells derived from the stratum basale  This is the hair matrix  All the cells of the hair are derived from the hair matrix.  Just beneath the hair matrix is an obvious dermal papilla called the hair papilla  Contains the blood vessels that nourish the matrix and the cells of the hair follicle https://www.researchgate.net/figure/Schema-of-the-healthy-lower-anagen-scalp-hair-follicle-Different-compartments-of-the-HF_fig1_361062959 HAIR AND HAIR FOLLICLES  Wrapped around the bulb of the follicle is a network of sensory nerve endings  Aka hair root plexus  Allow the hairs to serve a sensory function https://courses.lumenlearning.com/suny-dutchess-anatomy-physiology/chapter/somatosensation/ HAIR AND HAIR FOLLICLES  Attached to each hair is a bundle of smooth muscle  Aka arrector pili muscle  In times of fright or cold, these muscles contract and cause the hair to stand on end (and produces goose bumps)  Increases airflow in mammals with significant hair and increases the apparent size of an animal with significant hair  Vestigial in humans  I.e., Structure that have no apparent function; Appears to be residual parts of past ancestor https://stock.adobe.com/ca/images/function-of-the-arrector-pili-muscle/807959349 HAIR AND HAIR FOLLICLES https://www.nursinghero.com/study-guides/cuny-csi-ap-1/hair-and-nails HAIR AND HAIR FOLLICLES The arrow indicates an arrector pili muscle. In this picture, you should also try to identify the shaft, root, follicle, hair papilla, and sebaceous gland. CUTANEOUS NERVE SUPPLY  Motor (efferent system)  Controls blood supply and appendages  Sensory (afferent system)  Controls pain, touch, itch, temperature  THREE cutaneous/afferent receptors: 1. Free nerve endings  Itch + Temperature + Pain 2. Hair nerve endings  Touch 3. Encapsulated nerve endings  Touch + Vibration CUTANEOUS NERVE SUPPLY  THREE different afferent receptors  Free nerve endings  Hair nerve endings  Encapsulated nerve endings https://www.researchgate.net/figure/Cutaneous-touch-receptors-Mechanosensory-afferents-innervating-mammalian-skin-display_fig1_51603914 NERVE ENDINGS  Encapsulated  Meissner corpuscles  Light and soft touch sensations  In the dermal papillae of hands and feet  Pacinian corpuscles  Deep, firm touch and vibration  On palms, soles and digits  Ruffini corpuscles  Detects stretch, joint activity and warmth Grossman, S. & Porth, C.M. (20140. Porth’s Pathophysiology. 9th Edition. NERVE ENDINGS  Unencapsulated  Merkel’s disks/receptors  Slow-adapting mechanoreceptor  Touch (pressure and texture) http://opentextbc.ca/biology/wp-content/uploads/sites/96/2015/03/Figure_36_02_02.png CHECK YOUR KNOWLEDGE Match the following: Pain Stretch Free nerve endings Texture Temperature Meissner corpuscles Pacinian corpuscles Itch Light touch Ruffini corpuscles Vibration Deep touch Merkel’s discs Joint activity CHECK YOUR KNOWLEDGE Match the following: Free nerve endings Pain Itch Temperature Meissner corpuscles Light touch Pacinian corpuscles Deep touch Vibration Ruffini corpuscles Stretch Joint activity Merkel’s discs Texture CUTANEOUS NERVE SUPPLY  Controls blood supply and appendages  Derived from autonomic nervous system https://www.sciencedirect.com/science/article/abs/pii/B9780444534910000304 THE FASCIAL & MUSCLE LAYERS The Fascia  Very tough, yet flexile skin layer  Consists of fiber creators  Function(s):  Connects subcutaneous tissue and above layers to muscle The Muscles  High metabolic demand  Very sensitive to reduced blood flow  Function(s):  Keeps muscle moving by absorbing oxygen THE SKIN Orsted, H.L. et al. (2017). Foundations of Best Practice for Skin and Wound Management THE NAIL PLATE  It is translucent in areas where it is not attached to the nail bed  Distal free edge  Lunula  Areas of the nail plate attached to the vascular nail bed appear pink https://www.informedhealth.org/structure-of-the-nails.html THE NAIL PLATE  Nail plate is hard, strong, and flexible  Hardness and strength due to high content of hard keratins and cystine- rich high-sulfur proteins  Flexibility depends on its water content, but the plate is unable to hold water because of its low lipid content STRUCTURE AND FUNCTION OF THE NAIL 1. Protect the distal phalanges 2. Facilitate fine grasping and pinching 3. Efficient natural weapon 4. Contribute to aesthetic appearance of hands and feet STRUCTURE OF THE NAIL  Proximal nail fold covers proximal third of the nail plate  The nail plate results from maturation and keratinization of the nail matrix epithelium and is firmly attached to the nail bed which partially contributes to its formation https://courses.lumenlearning.com/wm-biology2/chapter/glands/ STRUCTURE OF THE NAIL  Hyponychium:  The anatomic area between the nail bed and the distal groove, where the nail plate detaches from the dorsal digit  Eponychium:  A thin cuticular fold of stratum corneum from the proximal nail fold overlapping the matrix STRUCTURE OF THE NAIL  The transverse nail plate originates from THREE separate areas:  Proximal nail matrix → Dorsal nail plate  Distal nail matrix → Intermediate nail plate  Nail bed → Ventral nail plate STRUCTURE OF THE NAIL  Nail matrix:  Synthesizes the nail plate substance  Extends under the proximal nail fold 5 to 10mm in depth  Lunula  White semicircular area at the proximal end of the nail plate  Distal aspect of the matrix  Junction point between the nail matrix and the nail bed https://www.informedhealth.org/structure-of-the-nails.html ANATOMY OF THE TOENAIL ANATOMY OF THE TOENAIL NAIL GROWTH  The nail plate thickens progressively from its emergence its distal margin  Mean toenail thickness:  Men : 1.65 +/- 0.43mm  Women: 1.38 +/- 0.20mm  Thickness depends on the length of the matrix and nail bed  Increased thickness with age  Matrix disorders generally cause thinning of nails  Nail bed disorders generally cause thickening of nails NAIL GROWTH  Nails develops during the ninth embryonic week from the epidermis of the dorsal tip of the digit  Slow at birth, increases during childhood, maximizes between the second and third decades, and decreases after 50  Nail growth rate depends on the matrix  Mean nail growth:  Fingernails 3mm per month  Toenails 1mm per month NAIL GROWTH  Growth rates vary due to disease, drug use and trauma  Systemic illness, malnutrition, peripheral vascular and neurologic diseases, “nail trauma” onychomycosis, and antimitotic drugs will slow growth rates  Pregnancy, “nail trauma”, psoriasis, treatment with certain drugs (e.g., retinoids, itraconazole) will accelerate growth rates  Please download and install the Slido app on all computers you use Which of the following is TRUE? (Check all that apply ⓘ Start presenting to display the poll results on this slide. REFERENCES  Dockery, G.L. (1997). Cutaneous Disorders of the Lower Extremity. Philadelphia: W.B. Saunders Company  Grossman, S. & Porth, C.M. (2014). Porth’s Pathophysiology. (9th edition). Philadelphia, PA: Wolters Kluwer  Orsted, H.L., Keast, D.H., Forest-Lalande, L., Kuhnke, J.L., O’Sullivan-Drombolis, D., Jin, S., et al. Skin: Anatomy, physiology and wound healing. In: Foundations of Best Practice for Skin and Wound Management. A supplement of Wound Care Canada; 2017. 26