L10- Integumentary System PDF

L10- INTEGUMENTARY SYSTEM SKIN AND ITS APPENDAGES Dr.Pugazhandhi Bakthavatchalam Assistant Professor of Anatomy and Physiology, AUACAS, American University of Antigua MR.PUGAZHANDHI.B Part of L-9: Foramens in the skull and major structures passing throu...

L10- INTEGUMENTARY SYSTEM SKIN AND ITS APPENDAGES Dr.Pugazhandhi Bakthavatchalam Assistant Professor of Anatomy and Physiology, AUACAS, American University of Antigua MR.PUGAZHANDHI.B Part of L-9: Foramens in the skull and major structures passing through them LEARNING OUTCOMES At the end of this session the student would be able to: Classify skin and describe its various appendages Describe the structure of thick and thin skin with regard to epidermis, dermis, glands and appendages Differentiate between thick (non-hairy) and thin ( hairy) skin Briefly describe the receptors in the skin and list their function 2-Sep-24 3  INTRODUCTION Skin is the outer covering of the body Hair, sebaceous glands, nails and sweat glands are derivatives or appendages of skin The skin and its appendages constitute the integumentary system FUNCTIONS OF SKIN: Covers and protects the body. Control internal temperature. Produces vitamin D. Receptors to detect environmental stimuli. Regulates the movement of substances into and out of the body Forms the largest organ of the body, forms 16% of body weight 2-Sep-24 4  Layers of Skin  Epidermis: is outermost layer. Stratified squamous keratinized epithelium. Keratinization production of a waterproof protein. Pigments.  Dermis: living portion of skin mostly dense connective tissue. Contains :connective tissue fibers &cells ,vessels, sweat glands, sebaceous glands and hairs.  Hypodermis : Adipose tissue and Contains receptors Epidermis and dermis Epidermis (purple) Dermal papillae Dermis Superficial papillary layer contains loose connective tissue, blood vessels, nerves, and lymphatics Deeper reticular layer has dense fibrous irregularly arranged connective tissue Layers of epidermis are  Stratum basale (germinativum)  Stratum spinosum  Stratum granulosum  Stratum lucidum (may not be present)  Stratum corneum Corneum (squames) Granulosum (keratohyalin granules) Spinosum (desmosomes) Basale (germinal) TYPES OF EPIDERMAL CELLS  Types:1-THICK SKIN EPIDERMIS Is thick :0.8mm in palm ,1.4 mm in sole. Contains 4 types of cells: o 1-keratinocytes (85% of cells) o 2-Melanocytes o 3-Langerhans cells o 4-Merkel cells Arranged in five layers.  THIN SKIN  All over the body except sole & Palms.  Epidermis: is thinner, stratum Spinosum : 2-4layers, stratum Granulosum one incomplete layer No stratum lucidum ,Stratum corneum is thinner  Dermis contains: Numerous sweat glands are seen Contain hair, sebaceous glands and arrector pilli muscle  DIFFERNCES BETWEEN THIN AND THICK SKIN THIN SKIN THICK SKIN  Stratum spinosum and  Stratum spinosum and corneum are thin, stratum corneum are thick, stratum lucidum is absent lucidum is present  Epidermal ridges are  Epidermal ridges are present absent  Hair follicles, arrector pili  Hair follicles, arrector pili muscles, sebaceous glands muscles, sebaceous glands are absent are present  Many sweat glands are seen  Few sweat glands are seen  Sensory receptors are less  Sensory receptors are more  Covers all parts of the  Present in palms, palmar body except palms and surface of digits and soles soles 2-Sep-24 12  THE DERMIS 1-Papillary layer :  Forms dermal papillae  Loose connective tissue rich in collagen type III  Elastic fibers, connective tissue cells and rich in blood capillaries  Contain meisssners corpuscles Meissner’s (Tactile) Corpuscle Located in the dermlpapillae Receptor for light touch 14  2- Reticular layer  The thicker deep layer  Formed of dense connective tissue rich in interlacing wavy collage fibers  It is less cellular &less vascular  Contain many nerve receptors: ( Mechanoreceptors) Krause end bulbs Ruffini corpuscles Pacinian corpuscles  Pressure, Vibrations,  RECEPTORS OF SKIN The sensory receptors in the skin are: cutaneous mechanoreceptors Ruffini's end organ - sustained pressure Meissner's corpuscle - changes in texture, slow vibrations Pacinian corpuscle - deep pressure, fast vibrations Merkel's disc - sustained touch and pressure Free nerve endings thermoreceptor nociceptor bulboid corpuscles chemoreceptor 2-Sep-24 16 GLANDS AND SKIN APPENDAGES Sebaceous glands Clumps of epithelial tissue distributed within dermis Secrete “sebum”—oily, fat-based substance that is also anti-bacterial Located all over body Sweat glands Microscopic clumps of epithelial tissue distributed within dermis, duct extends out through dermis to pore their secretion. More than 2.5 million glands per person  Glands and skin appendages Sweat glands  Eccrine sweat glands, concentrated on hands and soles of feet and forehead, secrete sweat to cool body, also at conditions of fear and emotion.  Apocrine glands, concentrated in armpits and groin, analogous with sexual scent glands of other animals, odor comes from bacteria that concentrate here  Ceruminous glands: modified sweat glands in ear canal produce ear wax  Mammary glands: modified sweat glands in female breast produce mother’s milk Classification according to mode of secretions Merocrine-Secretory granules leave the cell by exocytosis without loss of other cellular materials. e.g. Pancreatic gland Apocrine-Secretory granules discharged together with parts of the apical cytoplasm. e.g. Mammary glands, some of sweat gland. Holocrine-Secretory granules shed with the whole cell. e.g. Sebaceous gland.  Merocrine Apocrine Holocrine SWEAT GLANDS Two types of sweat glands Eccrine Not associated with hair follicle Duct segment o less coiled, leads to epidermis o Stratified cuboidal epithelium Secretory segment o in deep dermis or hypodermis o Secretory cells o Myoepithelial cells lie between secretory cells, contraction expels sweat Apocrine Found in limited areas Empty into hair follicle  HAIR  Hair follicles are tubular invaginations of the epidermis, that develop as downgrowths of the epidermis into the dermis. Hair is made up of columns of dead keratinised cells  A central medulla, or core (not seen in fine hairs), surrounded by a keratinised cortex, and the outer third layer, which is highly keratinised and forms the thin hard cuticle on the outside of the hair  The base of the hair follicle/hair bulb, there is a dermal papilla, which contains the blood supply for the hair 22  HAIR  The ducts of the sebaceous glands discharge sebum onto the hair.  The arrector pili muscle is a small bundle of smooth muscle cells associated with the hair follicle.  Contractions of this muscle elevate the hair, forming goose bumps, to release heat and help sebum to be released from gland into duct. 23  NAIL http://slideplayer.com/slide/272912/ 2-Sep-24 24 REFERENCES Color.Textbook.of.Histology By Leslie P. Gartner 3rd edition Atlas and textbook.of.Histology by Ross 6th edition Junqueira - Basic Histology - Text and Atlas 11e Bluehistology.com Ross, M. Pawlina, W. Wheater’s Functional Histology: A Text and Atlas. Fifth Edition. 25