Lecture 1 Intergumentary System PDF

CHAPTER 1 INTERGUMENTARY SYSTEM By: SHARIFAH NORHAFIZAH BINTI SYED ABDUL HAMID HUMAN BIOLOGY 2 DMHB 4122 LEARNING OUTCOMES Definition...

CHAPTER 1 INTERGUMENTARY SYSTEM By: SHARIFAH NORHAFIZAH BINTI SYED ABDUL HAMID HUMAN BIOLOGY 2 DMHB 4122 LEARNING OUTCOMES Definition Part of integumentary system – Skin – Layer of skin – Thick and thin skin – Physiology of the skin  INTRODUCTION Definition: – The system that protects the body from various kinds of damage, such as loss of water or abrasion from outside. – The outer most covering of the body. – It also includes blood vessels, nerves and sensory receptors, sweat and oil glands, other derivatives. – Comprises the skin and appendages. Hair Scales Feathers Hooves Nails  SKIN The soft outer tissue covering vertebrates. The largest organ in the body. It is a complex organ that serves primarily a protective function. Thickness: 1.5 – 4.0 mm Strecthable & strong protective layer Waterproof Regenerates and self-healing/auto-healing Have 3 layers: – Dermis – Epidermis – Hypodermis LAYER OF SKIN LAYER OF SKIN  1. Epidermis The outermost layer. Thick keratinized stratified squamous epithelium consisting of four cell types and five layer. It does not contain blood vessels. Function: – Protection – Absorption of nutrients – Homeostasis. 1. Epidermis Keratin protein – gives waterproof feature to skin and protects the part under skin surface from injuries AVASCULAR – No blood vessels at this layer The basal cells of epidermis layer experience progressive process of MITOSIS Most cells are DEAD CELLS that are produced through the process of keratinization New cells produced from mitosis of basal cells of epidermis will push the former layer to the skin surface. Former cells are flattened, lose cellular contents and form keratin  KERATINIZATION Skin surface layer will get automatically removed at every 14 to 28 days Cell types I. KERATINOCYTES produce keratin; primary cell of epidermis Arise by stem cells in stratum basale Pushed to surface as continuously mitotic cells reproduce Keratin is produced as cells migrate Cells connected by desmosomes At surface, cells are dead keratin filled plasma membrane. Cell near surface dead as they are cut oof from nutrients. Cell types II. MELANOCYTES Produce pigment:melanin In stratum basale Have processes that contact all keratinocytes Transfer melanin to keratinocytes Melanin accumulates near cell’s apical surfaces to shield nucleus from UV Function: produces pigment for skin color and UV absorption Cell types III. LANGERHANS’ CELLS Contain macrophages, act in defence mechanism against pathogens Attack bacteria & viruses Stimulate immune system Damaged by UV exposure Cell types IV. MERKEL CELLS Touch receptor  2. Dermis This layer is the real skin; formed by binding tissues of fibrous, mostly elastic Cell types: – Fibroblasts – produce semi-fluid matrix – Macrophages – Mast cells and WBC Divide into 2 layers:  PAPILLARY LAYER  RETICULAR LAYER 2. Dermis  PAPILLARY LAYER RETICULAR LAYER Has papillae-bumps Most below dermis layer structure  allows Contains more perfect adjacent COLLAGEN fibre placement of epidermis compared to papillary and dermis layers More connective tissues Formed by areolar Criss-cross pattern of connective tissue and the collagen fibre forms structure is filled with strong elastic netting at several blood capillaries, reticular layer sensory nerves, lymph ducts, muscles, glands and hair follicles 3. Subcutaneous/ Hypodermis Placed below dermis layer Contains loose connective tissues/areolar, nerves, blood vessels and adipose tissues Function: Energy reservoir Provides the adhesion structure of skin with the structures underneath THICK AND THIN SKIN THICK AND THIN SKIN – They are distinguished on the basis of the thickness of the epidermis and not the entire thickness of the skin. – Most of the body covered with thin skin; which having 4 DISTINCT LAYERS. – Thick skin contains the Stratum Lucidum and may have 30 layers of keratinized cells. Continue…. PHYSIOLOGY OF SKIN PHYSIOLOGY OF THE SKIN Protective Barrier Regulator Of Body Temperature Synthesis Of Vitamin D Sensory Receptor Absorption Excretion BODY DEFENCE CHEMICAL BARRIER – Low pH at skin and sebum  slows down growth of bacteria on skin surfaces – Natural antibiotics – Katelisidin – protein that prevents bacterial infection in wounded skin – Melanin – pigment that prevents skin damages due to UV MECHANICAL/PHYSICAL BARRIER – Continuously contributed by skin structure and keratinization – Glycolipid stops the entrance of water and cell solutes BIOLOGICAL BARRIER – Contributed by Langerhans’ cells, macrophages and DNA – Langerhans’ cells in epidermis brings antigen to lymphocytes – Dermal macrophages – destroy bacteria and virus that penetrate epidermis – DNA structure – electron in DNA absorbs UV radiation and changes it to heat BODY TEMPERATURE REGULATION Normal body temperature depends to the balance between heat production and heat loss in body Control center for body temperature is at the hypothalamus in brain Control center will give impulses that causes either vasoconstriction or vasodilation of blood vessels BODY THERMOREGULATION VASOCONSTRICTION : shrinking of blood vessels – reduces blood flow to the areas away from skin surfaces – heat retention/storage VASODILATION :expansion of blood vessels  increases blood flow – loss of excessive heat HEAT PRODUCTION :product of body metabolism, especially from all muscles, hepar and glands in body HEAT LOSS : through body skin (sweat), kidney (urine), lungs (water vapor) and intestines (feces) Mechanism of body heat loss:  Radiation – the skin beams heat in infrared form further warming up nearby objects  Conduction – heat gets transferred from body to objects with direct contact like clothes, seats etc.  Convection/Heating – as heat flows through convection whereby air heating on skin surfaces causes the air gets lighter and moves upward to be replaced by colder air  Evaporation – the process of perspiration. Sweat on skin surfaces will evaporate/slowly drying and gives a cooling effect VITAMIN D SYNTHESIS Exposure of skin to UV light helps in the production of vitamin D Supported by calcium and phosphorus absorption from digestive system Vitamin D + calcium + phosphorus = formation and shape-retention of bone SENSORY ORGANS  Nerve fibres found in skin are sensory nerves  Nerve endings in skin receive sensory stimulations and pass the stimulations of pressure, temperature/heat (hot and cold) and pain to brain SENSORY ORGANS Meissner corpuscle Touch especially soft touches Pacinian corpuscle Firm pressure, proprioception vibration Krause body Temperature (cold), pressure Free nerve endings Heat, light pressure, pain Ruffini endings & Merkel’s discs Temperature (hot), continuous pressure Hair follicles receptor Movement across the surface of the skin ABSORPTION This function is limited Among the absorbed materials: – Lipid-soluble materials (e.g.: O2, CO2, steroids and lipid- soluble vitamins) – Plant oleoresins (e.g.: poison ivy and poison oak) – Organic solvents (e.g.: acetone, dry cleaning fluid, and paint thinner) – Metal dust (e.g.: plumbum, mercury, and nickel) EXCRETION Skin acts as the minor excretion organ for certain materials: – Sodium chloride and H2O in sweat (excessive sweating will cause sodium to be low in blood) – Urea (kidney function is impaired) – Aromatic materials (garlic and other spices)  SUMMARY The skin is the largest organ of the body, with a total area of about 20 square feet. The skin protects us from microbes and the elements, helps regulate body temperature, and permits the sensations of touch, heat, and cold. Skin is composed of three primary layers: the epidermis, the dermis and the hypodermis