Skin structures and functions ppt Dr.Mumux
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The skin is the largest organ of the body and consists of three layers - the epidermis, dermis and subcutaneous layer. The epidermis is made up of keratinocytes, melanocytes, Merkel cells and Langerhans cells arranged in five layers. The dermis lies below the epidermis and contains hair follicles, sweat and sebaceous glands, nerves and blood vessels. The subcutaneous layer is made of fat and connective tissue. The skin acts as a protective barrier, regulates body temperature, maintains fluid and electrolyte balance, acts as a blood reservoir and sensory organ, synthesizes vitamin D, and contributes to self-image.
Skin structures and functions ppt Dr.Mumux
- 1. Skin structures and functions Dr. Mumux Mirani (MPT Sports) Asst. Professor S. R. C. P. Gen. Medicine Unit - V Dermatology
- 4. SKIN: Organs are body structures composed of two or more tissues. The skin and its accessory organs make up the integumentary system. The organs of the integumentary system include the skin and its accessory structures including hair, nails, and glands, as well as blood vessels, muscles and nerves. Dermatology is the medical specialty for the diagnosis and treatment of disorders of the integumentary system.
- 5. Synonyms for skin used in medical field Cutis, derma, integument, cutaneous, dermatomes. Definition: It is a outer covering of the entire external surface of the body including the external auditory meatus and the outer tympanic membrane. It is in a continuation with mucous membrane at the orifices of the body.
- 8. Structure of the Skin The skin (cutaneous membrane) covers the body and is the largest organ of the body by surface area and weight consists of different tissues that are joined to perform a specific function. Thinnest on the eyelids, ear drum and external genital. Thickest on the heels the average thickness is 1 – 2 mm Colour: depends mainly on the vascularity of the epidermis and thickness of the keratin.
- 9. Types of Skin There are two major types of skin: Thin (hairy) skin covers all body regions except the palms, palmar surfaces of digits, and soles Thick (hairless) skin covers the palms, palmar surfaces of digits, and soles. Sweat glands are more in numbers. Absence of sebaceous glands and hair follicles.
- 10. Structure of the Skin It consists of two major layers: Outer, thinner layer called the epidermis, consists of epithelial tissue, supported on vascular dermis which provides a strong flexible base and nutrition. Inner, thicker connective tissue layer called the dermis Beneath the dermis is a subcutaneous (subQ) layer (also called hypodermis) which attaches the skin to the underlying tissues and organs.
- 11. Epidermis: keratinized stratified squamous epithelium with four distinct cell types and five distinct layers.
- 12. EPIDERMIS The epidermis has a number of important characteristics: Ectoderm in origin Superficial part of the skin Lacks blood vessels. Provide waterproofing to the skin Continuous mitosis occurs in the deepest layer called the stratum basale The layer of reproducing cells (the stratum basale), which lies at the base of the epidermis, is well-nourished by blood vessels from the deeper dermal layer. Cells are pushed outward as new cells are formed an become keratinized as they die.
- 13. Types of Cells in the Epidermis
- 14. 1. keratinocytes Principle cells originate from ectoderm - 90% of the cells produce keratin which is a tough fibrous protein that provides protection Cells push their way up to the surface from basal to cornified layer where they be dead cells filled with keratin. The keratin flakes are constantly rubbed off and replaced from cells below. Cells regenerate every 25-45 days
- 16. 2. Melanocytes cells produce brownish/black pigment called melanin. (8% of epidermal cells) that provides skin color. Find in stratum basale branching processes (dendrites) extends in all direction between adjacent keratinoctes. Melanin accumulates in melanosomes and transported along dendrites of the melanocytes to keratinocytes. Melanin accumulates on the superficial aspect of the keratinocyte shielding its nucleus from harmful UV light. Lack of melanin: albino
- 18. Differences in skin colour result from differing amounts of melanin and in the size of melanin granules. The amount of melanin produced is affected by genetics and environmental factors. Large amounts of melanin occur in some regions like freckles, moles, and nipples. Less melanin occurs in the lips, hands, and soles of the feet. All races have the same number of melanoctyes! The amount of melanin produced is determined by genetics. Skin colour
- 20. Albinism A single mutation can cause a deficiency or complete absence of melanin. Albinos have fair skin, white hairs, and unpigmented eyes
- 21. 3. Merkel’s cells Make contact with a sensory neuron ending called a Merkel disc (touch). which function in the sensation of touch along with the adjacent tactile discs Originate from stratum basale Epidermis of hairless skin Attach to keratinocytes by desmosomes
- 22. 4. Langerhans cells: involved in immune responses, arise from red bone marrow Star-shaped cells that migrate to epidermis. Epidermal dendritic cells (macrophages) Interact with a WBC called a T- helper cell Easily damaged by UV light.
- 24. Epidermis It consists of five layers: 1. Stratum germinativum – growing layer. 2. Stratum spinosum –layer with bridges. 3. Stratum granulosum –cells and nuclei disintegrating. 4. Stratum lucidum – clear cells. 5. Stratum corneum – keratin flakes.
- 25. (1) Stratum Corneum As a cell accumulates keratinohyalin granules, it is thought that rupture of lysosomal membranes release lysosomal enzymes that eventually cause cell death. The dead and dying cells filled with mature keratin form the stratum corneum (SC). The deeper cells of the stratum corneum retain their desmosomal junctions, but as they are pushed to the surface by newly forming cells of the stratum germinativum (SG),
- 26. (2) Stratum Lucidum Epidermis varies in thickness throughout the body depending mainly on frictional forces and is thickest on the palms of the hands and soles of the feet. The stratum lucidum (SL) is normally only well seen in thick epidermis and represents a transition from the stratum granulosum to the stratum corneum.
- 27. (3) Stratum Granulosum The progressive maturation of a keratinocyte is charcterized by the accumulation of keratin, called keratinization. The cells of the stratum granulosum (SGR) accumulate dense basophilic keratohyalin granules (seen on the close-up view). These granules contain lipids, which along with the desmosomal connections, help to form a waterproof barrier that functions to prevent fluid loss from the
- 28. (4) Stratum spinosum The cells that divide in the statum germinativum soon begin to accumulate many desmosomes on their outer surface which provide the characteristic “prickles” (see n on the close-up view) of the stratum spinosum (SS), which is often called the prickle-cell layer.
- 29. (5) Stratum germinativum (also called “stratum basale”) The stratum germinatum (SG) provides the germinal cells necessary for the regeneration of the layers of the epidermis. These germinal cells are separated from the dermis by a thin layer of basement membrane. After a mitotic division a newly formed cell will undergo a progressive maturation called
- 30. Dermis The dermis is the layer of skin beneath the epidermisthat consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptor/nerve endings that provide the sense of touch and heat. It contains the hair follicles, sweat glands, sebaceous glands, apocrine glands, lymphatic vessels and blood vessels. The blood vessels in the dermis provide nourishment and waste removal to its own cells as well as the Stratum basale of the epidermis. The dermis is structurally divided into two areas: a superficial area adjacent to the epidermis, called
- 32. (1) Papillary Region The papillary region is composed of loose areolar connective tissue. It is named for its fingerlike projections called papillae, that extend toward the epidermis. The papillae provide the dermis with a "bumpy" surface that interdigitates with the epidermis, strengthening the connection between the two layers of skin. In the palms, fingers, soles, and toes, the influence of the papillae projecting into the epidermis forms contours in the skin's surface. These are called friction ridges, because they help the hand or foot to grasp by increasing friction. Friction ridges occur in patterns (see: fingerprint) that are genetically and epigeneticallydetermined and are therefore unique to
- 33. (2) Reticular Region The reticular region lies deep in the papillary region and is usually much thicker. It is composed of dense irregular connective tissue, and receives its name from the dense concentration of collagenous, elastic, andreticular fibers that weave throughout it. These proteinfibers give the dermis its properties of strength, extensibility, and elasticity. Also located within the reticular region are the roots of the hair, sebaceous glands, sweat glands, receptors, nails, and blood vessels. Tattoo ink is held in the dermis. Stretch marks from pregnancy are also located in the dermis.
- 34. Subcutaneous Layer subQ layer (also called hypodermis) is not part of the skin but, among its functions, it attaches the skin to the underlying tissues and organs. This layer (and sometimes the dermis) contains lamellated (pacinian) corpuscles which detect external pressure applied to the skin. The subcutaneous layer (hypodermis) is composed of loose connective tissue and insulating adipose tissue. Contains half of the body’s fat; acts as padding and insulation. Contains the major blood vessels that supply the skin. common site for injection
- 36. Fat cells do not multiply after puberty -- as your body stores more fat, the number of fat cells remains the same. Each fat cell simply gets bigger! •Fat cells are large cells have very little cytoplasm, only 15 percent cell volume, a small nucleus and one large fat droplet that makes up 85 percent of cell volume. Cross-section view of your skin. The fat is in the subcutaneous layer, which is richly supplied with blood vessels.
- 37. Accessory Structures of the skin Hair – Non-living keratinized structure that extends beyond the surface of the skin in most areas of the body. What is arrector pili??? (involuntary smooth muscle located in the dermis and attached to the side of the each hair shaft) Skin glands – Sebaceous glands and Sweat glands Nails – Composed of hard, keratinized stratified squamous epithelial cells overlying the nail bed, located over the dorsal surfaces of the ends of fingers and toes.
- 38. Functions of the skin 1- Protection - physical barrier that protects underlying tissues from injury, UV light and bacterial invasion. - mechanical barrier is part non specific immunity (skin, tears and saliva). 2- Regulation of body temperature high temperature or strenuous exercise; sweat is evaporated from the skin surface to cool it down. To lose heat, the sweat glands produce sweat which evaporates from the surface and the blood vessels dilate. To conserve heat, the blood vessels contract and the arrector pili muscles produce ‘goose pimples’.
- 39. The skin plays a key role in the homeostatic mechanism that regulates body temperature. Response to increased body temperature Heat from cellular metabolism or the environment is transferred to the blood and carried to the hypothalamus of the brain. The hypothalamus signals the dermal blood vessels to dilate and sweat glands to secrete. Increased blood flow to the skin and evaporation of sweat results in a release of heat from the body.
- 40. Response to decreased body temperature Hypothalamus detects decrease in body temperature Hypothalamus stimulates dermal blood vessels to constrict and sweat glands to remain inactive. Decreased blood flow to the skin and lack of sweat reduce amount of heat loss. Skeletal muscles may also be stimulated (shivering) which increases cellular metabolism and thus, heat production.
- 41. 3. Fluid and electrolyte balance – Water, sodium chloride and urea are lost in sweat. The skin also prevents excess loss of body fluid, thereby contributing to homoeostasis. 4. Blood reservoir - dermis houses an extensive network of blood vessels carrying 8-10% of total blood flow in a resting adult. 5. Sensory – Nerve endings provide information on the environment, body position, impending damage (by pain, thermal and pressure receptors) and constitute an essential component of the body’s defense mechanism. 6. Synthesis of Vitamin D (cholecalciferol) - UV rays in sunlight stimulate the production of Vit. D. Enzymes in the kidney and liver modify and convert to final form; calcitriol (most active form of Vit. D.) Calcitriol aids in absorption of calcium from foods and is considered a hormone.
- 42. 7. Self concept – The skin is very important psychologically. Appearance is important to self-image and therefore self- confidence. It identifies us as who we are and to some extent where we belong (family likeness, race and culture). The facial skin particularly expresses state of health and contributes to non-verbal communication, as does hand skin. Destruction, disease involving skin causes severe difficulties for the patient and for the people he / she meets in society.
- 43. Thank you…