The Integumentary System PDF

The Integumentary System 1  The integumentary system is composed of: 1. Skin (cutaneous membrane) 2. Accessory structures (hair, oil and sweat glands, nails, and sensory receptors). It is the largest system of the human body....

The Integumentary System 1  The integumentary system is composed of: 1. Skin (cutaneous membrane) 2. Accessory structures (hair, oil and sweat glands, nails, and sensory receptors). It is the largest system of the human body. 2  The Integumentary System Functions of the integumentary system: 1. Body protection 2. Thermoregulation 3. Synthesis of Vitamin D 4. Provides sensory information 5. Maintains homeostasis. 3  Structures of the Skin The skin has 2 major layers: 1. Epidermis (outer layer) ▪ Epithelial tissues 2. Dermis (inner layer) ▪ Connective tissues 4  Hypodermis (subcutaneous tissue) is not part of the skin, and located underneath the dermis. Hypodermis: – Stabilizes the skin – Is made of elastic and adipose tissues – Has few capillaries and no vital organs – Is the site of subcutaneous injections (Ex: insulin injections). 5  Epidermis The superficial thinner portion, which is composed of epithelial tissue. Avascular (has no blood vessels). The epidermis is composed of keratinized stratified squamous epithelium. 6  Epidermis Contains 4 types of cells: ▪ Keratinocytes: produce keratin, to protect the skin and prevent dehydration. ▪ Melanocytes: produce melanin. ▪ Macrophages (Langerhans cells): involved in the immune responses. ▪ Tactile epithelial cells (Merkel cells): sensation of touch.  Epidermis The epidermis is composed of 4-5 layers: 1. The stratum corneum: the most superficial. 2. The stratum lucidum: only in thick skin 3. The stratum granulosum. 4. The stratum spinosum. 5. The stratum basal: the deepest. 8 Epidermis  Stratum Basal The deepest layer in epidermis. Composed of : 1. Keratinocytes. 2. Stem cells that undergo cell division. 3. Keratin intermediate filaments. 4. Melanocytes. 10  Stratum Spinosum Consists of: 1. Keratinocytes. 2. Keratin intermediate filaments insert into desmosomes, to provide strength and flexibility to the skin. 3. Langerhans cells and projections of melanocytes. 11  Stratum Granulosum Consists of keratinocytes that are undergoing apoptosis. Presence of darkly staining granules of a protein called keratohyalin. Also present in the keratinocytes are membrane-enclosed lamellar granules that release a lipid-rich secretion. 12  Stratum Lucidum Presents only in the thick skin of areas such as the fingertips, palms, and soles. It consists of clear, dead keratinocytes. This probably provides toughness to the skin. 13  Stratum Corneum Consist of flattened dead keratinocytes. Skin friction → increases keratin production → formation of Callus. Callus: Abnormal thickening of the stratum corneum. 14 Callus  Keratinization and Growth of the Epidermis Newly formed cells in stratum basal → pushed to the surface → Cells move from one layer to the next → and accumulate more keratin (keratinization) → undergo apoptosis. An excessive amount of keratinized cells shed from the skin of the scalp is called Dandruff. 16  Dermis Consists of: blood vessels, nerves, glands, hair follicles, and few cells. Divided into: 1. Thin superficial papillary layer: rich in nerve endings. 2. Thick deeper reticular layer: rich in regular collagen fibers that help resist stretching. 17 Dermis 18  The Structural Basis of Skin Color ▪ Color of skin is due to 3 pigments: Melanin, hemoglobin, and carotene. ▪ Because the number of melanocytes is about the same in all people, differences in skin color are due mainly to the amount of pigment. ▪ Exposure to ultraviolet (UV) light increases melanin production. ▪ The red skin color is due to hemoglobin. ▪ Vitamin A (in carrots) is used to synthesize pigments needed for vision, and is stored in the stratum corneum and fatty areas of dermis and hypodermis. 30 Accessory structures of the skin (Hair, hair follicles, sebaceous glands, sweat glands, and nails)  Hair Composed of dead, keratinized epidermal cells. The human body is covered with hair, except in Palms, Soles, Lips, and portions of external genitalia. Functions of Hair: – Protection and insulation. – Guards openings against particles and insects (ex: Nose). – Sensitive to very light touch.  Hair Parts of a hair include: 1. The shaft (above the skin) 2. The follicle (below the skin). 22  Hair A smooth muscle (Arrector pili muscle) is associated with the hair to arrect it. 23  Hair Glands The skin contains 4 types of glands: 1. Sebaceous (oil) glands: connected to hair follicles. 2. Eccrine sweat glands: the most numerous. 3. Apocrine sweat glands: located mainly in hairy skin. 4. Ceruminous glands: modified sweat glands located in the ear canal, that produce a waxy lubricating secretion. 24  Hair Glands Sebaceous glands secrete an oily substance called Sebum. Sebum coats the surface of hair and helps keep it from drying and becoming brittle. Sebum also prevents excessive evaporation of water from the skin, and inhibits the growth of some bacteria. 25  Hair Glands Eccrine sweat glands: Apocrine sweat glands: More common. Sweat appears milky or Secret sweats outwardly. yellowish in color. Distributed in most regions of Located mainly in hairy skin. the body. The duct opens at the hair The duct opens at the surface of follicle. the Epidermis. Start to function in Puberty. Start to function soon after birth. 26  Nails Nails: plates of hard, keratinized epidermal cells that form a clear, solid covering over the dorsal surfaces of digits. Nails structure: – Free edge – Nail body (plate) with a whitish lunula. – Nail root in the skin fold. 27  Sensory Receptors The skin contains different types of sensory receptors found in different layers: – Superficial: Merkel receptors and Meissner receptors (respond to slow vibration rates). – Deep: Pacinian corpuscle and Ruffini receptors (respond to high vibration rates). 28  Thin skin Thick skin Distribution All parts EXCEPT (palm Palm of hands and of hands and fingers, fingers, soles soles) Epidermal Strata No stratum lucidum Stratum lucidum present Hair Present No Sebaceous glands Present No Sweat glands Few More Sensory receptors Few More 29 Integumentary System Physiology  Wound Healing Two types of wound-healing depending on the depth of the injury: 1. Epidermal wound healing: following superficial wounds that affect only the epidermis. 31  Wound Healing 2. Deep wound healing: occurs when an injury extends to the dermis and subcutaneous layer. 32  1. 2. 3. 4. 33 Development of the Integumentary System The epidermis develops from the ectoderm. (Nails, hair, and skin glands are epidermal derivatives). The dermis develops from the mesoderm. 34  Aging The integumentary system changes with age: 1. Wrinkles develop. 2. Dehydration and cracking occurs. 3. Sweat production decreases. 4. A decrease in the numbers of melanocytes results in gray hair. 5. Decrease in skin thickness. 35  Aging With age, there is also an increased susceptibility to pressure ulcers “bed sores”. 36  Skin Cancer Caused by excessive exposure to ultraviolet light (from the sun). The three major types: 1. Basal cell carcinoma 2. Squamous cell carcinoma 3. Malignant melanoma. 37  Burns Burn: A tissue damage caused by excessive heat, electricity, radioactivity, or chemicals. Burns are graded according to their severity.  Burns A first-degree burn involves only the epidermis (sunburn). 39  Burns Burns A second-degree burn destroys the epidermis and part of the dermis (blister). 40  Burns Burns A third-degree burn is a full-thickness burn (destroys the epidermis, dermis, and subcutaneous layer). 41  Burns The rule of nines is used to estimate the surface area of an adult affected by a burn. 42 The End 43