Anatomy Of The Integumentary System PDF

ANATOMY OF THE Integumentary System Karthik Harve Associate Professor Health and Social Sciences Cluster Singapore Institute of Technology SG 138683 [email protected] Learning Objectives At the end of today’s lecture, you should be able to understand the 1. Structural organizati...

ANATOMY OF THE Integumentary System Karthik Harve Associate Professor Health and Social Sciences Cluster Singapore Institute of Technology SG 138683 [email protected] Learning Objectives At the end of today’s lecture, you should be able to understand the 1. Structural organization of the Epidermis, Dermis and Hypodermis 2. Secretory and Excretory functions of the skin 3. Thermoregulatory and Synthetic functions of Skin 4. Sensory functions of the skin and dermatomal mapping 5. Elementary concepts of skin response to injury Important Functions of the Integumentary System ▪ Protect against physical, chemical and biological insults ▪ Water-proof barrier ▪ Absorb UV radiation ▪ Excretion and thermoregulation ▪ Sense the external environment ▪ Synthesis of vitamin and pigments Skin structure ❑ The cutaneous membrane forming the external body surface ❑ Largest organ in the body @ 15% of adult body weight ❑ Mainly formed by two layers: - Epidermis (E) : Ectodermally derived Epithelial tissue - Dermis(D): Mesodermally derived Connective tissue ❑ Epidermo-dermal Junction = Basement membrane ❑ Hypodermis (H) : subcutaneous layer of fascia & fat ❑ Accessories: - Glands, hair and nails (E) - Blood vessels, Smooth muscle, Lymphatics, Sensory organs (D & H) Creative Commons Attribution-Share Alike 3.0 Unported Two Types of Skin Hairy Skin (‘Thin’ skin) ❑ Presence of hair & certain type of glands ❑ Lack of encapsulated sense organs in the dermis ❑ Epidermis is thinner ❑ Most regions of the body except palms & soles Glabrous Skin (‘Thick’ skin) ❑ Lack of hair & certain type of glands ❑ Presence of encapsulated sense organs in the dermis ❑ Epidermis is thicker ❑ Confined to the palms and soles ❑ Characterized by furrows and ridges: Dermatoglyphics Creative Commons Attribution-Share Alike 3.0 Unported Skin: Principal layers Image source: Wheater’s Functional Histology, 6th Edition Epidermis: Stratified squamous epithelium Image source: Wheater’s Functional Histology, 6th Edition Attribution 4.0 International (CC BY 4.0) Individual layers of the Epidermis Stratum basale (B): Single layer of cuboidal/columnar epithelium Cells: keratinocytes, stem cells, melanocytes & Merkel cells The cells attached to a basement membrane Stratum spinosum (S): Several layers of spiny keratinocytes In each layer, cells attached to each other by desmosomes Stratum granulosum (G): A few layers of keratinocytes containing granulosomes Each cell contains keratins, keratohyalins & lamellar bodies Image source: Wheater’s Functional Histology, 6th Edition Many dying (pyknotic cells) may be seen Stratum Lucidum(Only in ‘Thick’ Skin; not shown): Stratum corneum (C): Located between layers ‘G’ and ‘C’ Thick layers of dead keratinocytes A few layers of keratinocytes that appear ‘clear’ Cross-linked keratins dominate these layers The ‘clear’ appearance is due to a protein ‘eleidin’ Appendages of Skin: Hair and Sebaceous glands Image Source: iStock Image Source: Visible Body Nail: Skin Appendage with Hard Keratin Image Source: Visible Body Sweat Glands and Functions ▪ Location: Throughout the body; in the dermis ▪ Thermoregulation ▪ Secrete sweat (water + salts + urea) ▪ Excretion of waste & toxins Eccrine sweat gland: structure Creative Commons Attribution-Share Alike 3.0 Unported Eccrine sweat gland ▪ Majority of sweat glands ▪ Cholinergic innervation ▪ Ducts open into skin surface Image Source: iStock Image Source: https://upload.wikimedia.org/wikipedia/commons/f/f3/Gray946.png Sweat Glands Sweat Gland Types (Merocrine) (Eccrine) Image Source: iStock Apocrine sweat gland ▪ Axilla, areola & genital areas ▪ Adrenergic innervation ▪ Ducts open into hair follicle Mechanism of apocrine secretion Image Source: iStock Creative Commons Attribution-ShareAlike 4.0 International License Same Same but Different! The Difference is Skin color ☺ Melanocytes Langerhans cells Merkel cells ❑ Location: Basal layer @1:4 to 1:15 vis-à-vis keratinocytes ❑ Function: Production of Melanin Pigment ❑ Location: Epidermal layers ❑ Location: Basal Layer & Hair follicle ❑ 3 Types: Pheomelanin, Eumelanin & Neuromelanin ❑ Function: Immunity; Antigen presentation ❑ Function: Sensory to touch ❑ Melanin produced is donated to keratinocytes as Melanosomes ❑ Antigen stimulus → Migrate to lymph nodes ❑ Basal surface contacts an axonal terminal ❑ Melanin: Protects against UV radiation ❑ Their numbers increase in skin inflammation ❑ May have a neuroendocrine function Image Source: Visible Body Attribution 4.0 International (CC BY 4.0)  Other sources of skin color ▪ Beta-Carotene (Source for Vitamin A) ▪ Hemoglobin in the capillaries of dermis ▪ Jaundice: Bilirubin stains the dermal fibres & Conjunctiva Image Source: Wiki Commons  The Dermis: Layers and Functions Papillary Layer: Loose connective tissue (areolar tissue) Forms ‘peg’ like projections into epidermis Helps to transfer nutrients to epidermis Contains sensory receptors for fine touch Reticular Layer: Dense connective tissue (collagen) Location for sweat glands, Hair follicles, Sebaceous glands, blood vessels Contains sensory receptors for deep pressure and vibration Image Source: Visible Body The Hypodermis: Subcutis/Superficial Fascia Image Source: iStock ▪ Location: below the dermis ▪ Main components: Loose connective tissue + Fat ▪ Act as padding; allow sliding of skin on deeper structures ▪ Fat helps in thermal insulation ▪ Rich in blood vessels: absorptive function (e.g. drugs) Image Source: iStock Sensory Structures in the Skin https://creativecommons.org/licenses/by/4.0/ Sensory Structures in the Skin Meissner’s Corpuscle ▪ Location: papillary dermis (finger tips) ▪ Fast-adapting receptors ▪ Sense fine discriminatory touch Creative Commons Attribution-Share Alike 3.0 Unported Pacinian Corpuscle ▪ Location: reticular dermis ▪ Fast-adapting receptors ▪ Sense deep transient pressure & vibration https://creativecommons.org/licenses/by/4.0/ Skin as a Sensory organ: Dermatomes and Mapping  Clinical Association and Application of Dermatomes Shingles: Varicella Zoster infection of Skin Cutaneous Hemangiomas Goraya G S, Singhal S, Paul B S, et al. (January 24, 2022) Aggressive Vertebral Hemangioma: The Mystery of Spastic Legs Unveiled by a Purple Shoulder. Cureus 14(1): e21568. doi:10.7759/cureus.21568 Clinical Association and Application of Dermatomes Referred Pain of Angina Pectoris The pain due to lack of blood supply to myocardium is felt or ‘referred’ to: → Left upper limb all the way to the little finger → Anterior chest → Neck and Jaw The reason being: The spinal segments conveying visceral pain from the injured myocardium also receive sensations from the skin of left upper limb, anterior chest wall, neck and jaw Skin as a thermosensor Image source: Wheater’s Functional Histology, 6th Edition Creative Commons Attribution 3.0 Unported Skin and Injury: Steps in Wound Healing Image Source: AdobeStock https://creativecommons.org/licenses/by/4.0/  Chronology of Wound Healing William R. Parrish, Breana Roides (2017) Physiology of Blood Components in Wound Healing:an Appreciation of Cellular Co-Operativity in Platelet Rich Plasma Action. J Exerc Sports Orthop 4(2):1-14. DOI: http://dx.doi.org/10.15226/2374-6904/4/2/00156 Wound Healing and Scarring Creative Commons Attribution-Share Alike 3.0 Unported Skin Burns Image Source: iStock Creative Commons Attribution 3.0 Unported Skin Aging https://creativecommons.org/licenses/by/4.0/ Image by Int. J. Mol. Sci. 2021, 22(8), 3974; https://doi.org/10.3390/ijms22083974 macrovector on Freepik Skin Lines and Clinical Relevance Skin tension lines represent a map of the direction in which the tension in the skin is maximal at different body sites, due to the pattern of arrangement of collagen fibres in the dermis These lines reflect internal tension within the skin caused by collagen fibres in the connective tissue of the dermis, superimposed by external tension. Relaxed Skin Tension Lines Langer’s cleavage lines Clinical Relevance of Tension Lines of Skin Incision made perpendicular to Incision made parallel to tension tension lines → Heal with Scarring lines → Heal with Less/No scarring https://www.scientificarchives.com/public/assets/articles/article-pdf-1664348751-476.pdf Goran_tek-en, CC BY-SA 4.0 , via Image courtesy of Blanco, JMA. et al. Wikimedia commons Wikimedia Commons End of Lecture