integumentry system. integumentry system in details with diagrams
- 2. Introduction The skin also known as cutaneous membrane or integument, covers the external surface of the body and protects the interior of the body. It is a sensory organ which is an largest organ of the body in both surface area and weight. In adults skin covers an area about 2 sq.mts (22 sq.ft), weighs about 4.5 to 5 kgs and 16% of the body weight.
- 3. Three Layers of skin Epidermis: Stratified squamous epithelium; outer layer is "keratinized“ or "cornified“ Dermis: Dense irregular connective tissue Hypodermis: Adipose connective tissue (technically not part of system
- 5. Layers of the Epidermis From deepest to most superficial the layers of the epidermis are 1. Stratum basale (stratum germinativum) 2. Stratum spinosum 3. Stratum granulosum 4. Stratum lucidum (only in palms and soles) 5. Stratum corneum
- 6. Four Principle Cells of the Epidermis 1. Keratinocytes – produce the protein keratin, which helps protect the skin and underlying tissue from heat, microbes, and chemicals, and lamellar granules, which release a waterproof sealant 2. Melanocytes – produce the pigment melanin which contributes to skin color and absorbs damaging ultraviolet (UV) light
- 7. 3. Langerhans cells – derived from bone marrow – participate in immune response 4. Merkel cells – contact a sensory structure called a tactile (Merkel) disc and function in the sensation of touch
- 8. Dermis Connective tissue layer composed of collagen & elastic fibers, fibroblasts, macrophages & fat cells • Contains hair follicles, glands, nerves & blood vessels • Two major regions of dermis – papillary region – reticular region
- 9. Dermis - Papillary Region Top 20% of dermis. Finger like projections are called dermal papillae anchors epidermis to dermis. contains capillaries that feed epidermis. contains Meissner’s corpuscles in the dermis near dermo- epidermo junction. Detection of sensations of touch, shape and texture. Free nerve endings for sensations of heat, cold, pain, tickle, and itch.
- 10. Dermis - Reticular Region Dense irregular connective tissue. Contains interlacing collagen and elastic fibers. Packed with sebaceous glands, sweat gland ducts, fat & hair follicles. Provides strength, extensibility & elasticity to skin. stretch marks are dermal tears from extreme stretching. Epidermal ridges form in fetus. fingerprints are left by sweat glands open on ridges increase grip of hand
- 11. Glands of the Skin Specialized exocrine glands found in dermis are Sebaceous (oil) glands Sudoriferous (sweat) gland Ceruminous (wax) glands Mammary (milk) glands
- 12. Sebaceous (oil) glands Sebaceous (oil) glands are usually connected to hair follicles; they are absent in the palms and soles Produce sebum – contains cholesterol, proteins, fats & salts – moistens hairs – waterproofs and softens the skin – inhibits growth of bacteria & fungi (ringworm) Acne – bacterial inflammation of glands – secretions are stimulated by hormones at puberty
- 13. Sudoriferous (sweat) glands • Eccrine sweat glands (most areas of skin) – regulate body temperature through evaporation (perspiration) – help eliminate wastes such as urea. • Apocrine sweat glands– secretions are more viscous
- 14. Ceruminous Glands • Ceruminous glands – produce a waxy substance called cerumen. – found in the external auditory meatus – barrier for entrance of foreign bodies
- 15. FUNCTIONS OF SKIN Protection Thermoregulation Sensation Vitamin D synthesis Excretion & Absorption Psychological and social functions Blood reservoir
- 16. Protection Physical, chemical and biological barriers Tight cell junctions prevent bacterial invasion Lipids released retard evaporation Pigment protects somewhat against UV light Langerhans cells alert immune system
- 17. Thermoregulation Perspiration & its evaporation – lowers body temperature – flow of blood in the dermis is adjusted Exercise – in moderate exercise, more blood brought to surface helps lower temperature – with extreme exercise, blood is shunted to muscles and body temperature rises Shivering and constriction of surface vessels – raise internal body temperature as needed
- 18. Cutaneous Sensations Touch, Pressure, Vibration, Tickle, Heat & Cold (Thermal) Pain & Itch (Noxious)
- 19. Synthesis of Vitamin D Activation of a precursor molecule in the skin by UV light Enzymes in the liver and kidneys modify the activated molecule to produce calcitriol, the most active form of vitamin D. Necessary vitamin for absorption of calcium from food in the gastrointestinal tract
- 20. Excretion & Absorption Excretion 400 ml of water/day, Small amounts Nacl, CO2, Ammonia and Urea Absorption Water soluble – Negligible Lipid solubleVitamins -A, D, E, K Organic solvents Heavy metals Topical medicines