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Integumentary System Integumentary System Chapter 5 Integumentary System Integumentary system consists of: 1) Skin….the cutaneous membrane-Composed of epidermis and dermis 2) Accessary structures- hair, nails, glands. Dermatology: branch of medicine that deals with the diagnosis and treatment of skin disorders. Epidermis Papillary layer Dermis Reticular layer Hypodermis Fat Hypodermis/subcutaneous layer- NOT a part of the skin: - attaches skin to the muscle underneath. - contains blood vessels and nerves and large amount of adipose tissue - permits independent movement of deeper structures Functions of Skin 1) Protection: Stratified squamous epithelium….protects from abrasions. Sweat and oils….protects from bacterial infections. Keratin….water-proofing protein….prevents dehydration. Melanin….brown pigment….protects from UV exposure. 2) Thermoregulation: Sweat glands….evaporation of sweat cooling. Blood vessels vasoconstrict/vasodilate control blood flow in the skin heat loss/conservation. 3) Sensation: Nerve endings…sense temperature, touch, pressure, pain. Abundant in skin of the face, fingers, nipples, genitals. Fewer in skin of the back, knees, elbows. 4) Excretion: sweat…water, salt, organic substances. 5) Fat storage: adipose tissue in skin and subcutaneous layers. 6) Immunity: WBCs in skin….protect from infections. 7) Blood reservoir: blood vessels in skin hold 5% blood can be diverted to other organs. 8) Synthesis of vitamin D: skin, kidneys, liver together help make vitamin D used to absorb Ca bone development and maintenance. 9) Communication: facial expression, reflection of age, emotions. Structure of Skin Epidermis Papillary layer Dermis Reticular layer Hypodermis Skin is composed of two layers: 1) Epidermis – top layer of the skin. Skin is defined as thin or thick based on the epidermis: Thinner in thin skin (most of the body) and thicker in thick skin (palm, soles). 2) Dermis – lower layer of the skin. Epidermis Epidermis Papillary layer Dermis Reticular layer Hypodermis Fat I) Epidermis : Made of stratified squamous epithelium…accommodates wear/tear. Avascular…blood vessels only till the base layer…cells are fed by diffusion. Nerve endings end at the base of epidermis…limited to dermis. It is 4 layered in thin skin. It is 5 layered in thick skin. Epidermis Thin skin: Thick skin: Covers most of the body. Covers palms and soles. Composed of 4 layers: Composed of 5 layers: Stratum corneum Stratum corneum Stratum granulosum Stratum lucidum Stratum spinosum Stratum granulosum Stratum basale Stratum spinosum Stratum basale Study each layer….going from the bottom layer top layer. Epidermis Stratum basale: bottom/deepest layer Consists of: a) Stem cells divide by mitosis new cells: b) Melanocytes make melanin (brown pigment) give color to the skin. c) Merkel/Tactile cells touch sensation. Epidermis Stratum spinosum: second layer from the bottom…derived from stratum basale cells. Consists of: a) Keratinocytes-makes keratin (water-proofing protein) prevents water loss through skin…prevents dehydration. b) Langerhans/Dendritic cells immune cells that protect against infections. Epidermis Stratum granulosum: third layer from the bottom…derived from stratum spinosum. Consists of: Flattened Keratinocytes…3-5 layers of cells accumulate keratin. Epidermis Stratum lucidum: - Absent in thin skin. - Found only in thick skin of palm and sole. - Consists of 3-5 rows of flattened dead keratinocytes that further accumulate keratin. Epidermis Stratum corneum: -Top layer of the epidermis. -Thicker in thick skin of palm and sole….thinner in thin skin. - Consists of rows of completely dead cells. - Packed (15-30 layers) with keratin-Responsible for water resistance -Forms tiny specks/clusters – dander continuously fall away – exfoliation. Dermis Epidermis Papillary layer Dermis Reticular layer Hypodermis II) Dermis – lower layer of the skin-Made of fibrous connective tissue, blood vessels and nerves. Also has glands and hair follicles. - Although not used to define thick vs. thin skin, it is thinner in thin skin and thicker in thick skin - Dermis is made of 2 regions: 1) Papillary region- upper, thinner region of dermis. 2) Reticular region- lower, thicker region of dermis. Dermis Epidermis Papillary layer Dermis Reticular layer Hypodermis Fat Dermis : 1) Papillary region- upper, thinner region of dermis. -Forms finger-like projections – dermal papillae Project into epidermis forms epidermal ridges (fingerprints reveal the pattern of epidermal ridges). Dermis Epidermis Papillary layer Dermis Reticular layer Hypodermis Dermis : 2) Reticular region- lower, thicker region of dermis. - Contains accessory structures – glands and hair follicles. - Collagenous fibers are arranged in parallel bundles establishes cleavage or tension lines. Dermis Bedsores/Decubitis ulcers: Comatose patients dermal blood vessels in papillary and reticular layers of dermis are pressed against deeper layers blood supply cuts off epidermis and dermis dies (necrosis) infection…open sores…ulcers. Skin Color Primary pigments found in epidermis:- 1. Melanin: brown color 2. Hemoglobin: red color from the blood 3. Carotene: yellow color Skin Color 1. Melanin: a) Brown color pigment produced by melanocytes present in stratum basale of epidermis. b) Number of melanocytes is similar in different races, only the levels of melanin synthesis is different. c) Melanin protects epidermis and dermis from harmful effects (UV) of sunlight Melanin production is controlled by: A. Genetics – affects the amount of melanin produced, its distribution, and the rate at which it is broken down. B. Exposure to UV more melanin produced skin becomes darker – skin tan C. Hormone MSH – produced by pituitary gland stimulates melanocytes to synthesize and distribute. melanin pigment melanocyte Skin Color 2. Hemoglobin-Blood contain red blood cells filled with hemoglobin More capillaries in dermis and thinner epidermis redder the skin. Skin Color 3. Carotene: yellow color from the pigment. - Pigment found in yellow fruits and vegetable - Can make vitamin A. -Greater consumption of carotene pigment accumulates in stratum corneum and subcutaneous fat yellow hue in Asian skin. Skin Color Disorders a)Albinism: melanocytes are present, but melanocytes cannot make melanin absence of melanin production- no color in skin, hair or eyes. b) Vitiligo: partial or complete loss of melanocytes patchy white spots on skin. c) Freckles and moles: overproduction of melanin in areas melanin accumulates in patches. d) Hemangiomas: too many blood capillaries in dermis patches of red-purple called strawberry birthmarks or also called port wine stains. May disappear during early childhood years or last life long. Vitiligo Albinism Freckles Hemangioma Skin Color Clues Skin color clues: help detect certain physiological disorders or conditions. 1) Cyanosis- bluish skin color…oxygen deficiency…hemoglobin turns darker red reflects bluish through the skin-due to respiratory obstruction/arrest, heart failure, exposure to extreme cold. 2) Jaundice- yellow skin color-liver cannot excrete bile (bilirubin)-due to liver disorder (hepatitis, cancer, cirrhosis), blood infections or blood group issues at birth 3) Erythema- red skin color…vasodilation due to exercise, high temperature, anger, embarrassment, heatstroke. 4) Bruise- blood vessel break bleeding hematoma under the skin changes from red to blue to yellow slowly fades away. 5) Pallor- pale skin…due to temperature drop, anemia, low blood pressure, emotional stress. Cyanosis Jaundice Bruise Skin – Vitamin D Synthesis & Ca Absorption Limited exposure to sunlight is beneficial! Exposure of skin to UV Skin epidermis (stratum basale and spinosum) use steroids to make vitamin D3 or cholecalciferol Liver converts it to an intermediary compound Kidneys convert it to hormone calcitriol Calcitriol is used to help absorb calcium and phosphorous by small intestine. Cholecalciferol/Vitamin D3 can be absorbed from food…egg yolk, fish oil, fortified milk. Lack of enough sunlight exposure or Vitamin D3(cholecalciferol) in diet –abnormal bone development maintenance & growth Rickets in children…weak bones, bowed legs (bending of bones) Osteomalacia in adults Accessory Structures Structures associated with skin…hair, glands and nails. Hair, glands and nails may be located in dermis but derived from epidermis….referred to as epidermal derivatives. Keratin may be loosely arranged (soft keratin in skin epidermis). Keratin may be tightly packed (hard keratin in nails and hair). Accessory structure-Hair Non-living structures produced in organs called hair follicles Anatomy: Shaft – part that projects beyond the skin. Root – part that is embedded in the skin. Bulb – swollen base of the hair. Hair/dermal papilla-contains blood vessels and nerves Arrector pili: a band of smooth muscle that connects hair follicle to the epidermis, when contracts lifts hair and follicle goose bumps hair erect Types of hair: Lanugo- fine hair of fetus shed soon after birth. Vellus hair- fine hair all over the body. Terminal hair- thicker hair on head, eyelash, eyebrow, nose, axillary, pubis. Accessory structure-Hair Alopecia: Partial or complete loss of hair due to hormonal changes or skin disease. Hirsutism: Excessive hair due to hypersecretion of androgens. More obvious in women and children. Accessory structure- Glands Glands: exocrine glands that discharge their secretions to outside through a duct. 1) Sudoriferous glands 2) Mammary glands 3) Sebaceous glands 4) Ceruminous glands Accessory
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