In The Name of God (A PROJECT OF NEW LIFE HEALTH CARE SOCIETY, KARACHI) Unit-3-A Anatomy & Physiology of Skin Shahzad Bashir RN, BScN, DCHN, MScN (Std. DUHS) Instructor New Life College of Nursing Updated October 07, 2015
Structure and Function. Skin include in integumentry system, Largest organ or system of the body. In adult it covers the area about 1.2-2 Square meters (22 Square feet), and weigh about 4.55 kg. About 16% of total body weight. It ranges in thickness varies from 0.5mm(0.2in.) on the eyelids to 4.0mm (0.16in.)on the heels. However most of the body is 1-2mm(0.040.08in.) thick. Slide 13-2
The Skin. The skin, hair, and nails are external structures that serve a variety of specialized functions. The sebaceous and sweat glands originating within the skin also have many vital functions. The skin is composed of three layers: the epidermis, dermis, and subcutaneous tissue. The skin is thicker on the palms of the hands and soles of the feet. Subcutaneous tissue, which contains varying amounts of fat. connects the skin to underlying structures. Slide 13-3
The Skin. The skin is a physical barrier that protects the underlying tissues and structures from: Microorganisms Physical trauma Ultraviolet radiation Dehydration. Slide 13-4
The Skin. It plays a vital role in: Temperature maintenance Fluid and electrolyte balance Absorption Excretion Sensation Immunity Vitamin D synthesis. Person's appearance. Slide 13-5
The Skin. Epidermis Keratinized stratified squamous epithelium The epidermis, the outer layer of skin, is composed of five distinct layers: Layers (from deep to superficial) Stratum basale or germinativum single row of cells attached to dermis; youngest cells Stratum spinosum composed on tonofilaments (bundles of protein) resist tension Stratum granulosum layers of flattened keratinocytes producing keratin (hair and nails made of it also) Stratum lucidum (only on palms and soles) Stratum corneum horny layer (cells dead, many layers thick) Slide 13-6
Epithelium: layers (on left) and cell types (on right) 7
The Skin. Epidermis It contain four principles types of cells: Kertinocytes (About 90%,Kertino=hornlike, Cytes =Cell, Produce Protein and Lamellar Granules) Malenocytes (About 8%, Maleno = Black, Develop from Ectoderm and produce Melanin= Yellow-red or brown-black pigments) La gherhe s Cell (About 1%,Arise from Red bone marrow, Participate in immune response) Merkel Cells(About 1%, Located in deepest layer of skin, Contact with flattened process of sensory neuron and help in sensation through Merkel or Tactile disc) Slide 13-8
Slide 13-9
Slide 13-10
Slide 13-11
The skin. Dermis The inner layer of skin is the dermis. It is connected to the epidermis by means of papillae. The dermis is a well- vascularized mainly composed of connective tissue layer containing collagen and elastic fibers, nerve endings, and lymph vessels. It is also the origin of hair follicles, sebaceous glands, and sweat glands. Two layers (see next slides) Papillary areolar connective tissue; includes dermal papillae Reticular reticulu etwork of collage a d reticular fibers Slide 13-12
*Dermal papillae * Dermis layers * * 13
Sebaceous Glands The sebaceous glands develop from hair follicles and. therefore, are present over most of the body, excluding the soles and palms. They secrete an oily substance called sebum that lubricates hair and skin and reduces water loss through the skin. Sebum is a mixture of triglycerides, cholesterol, proteins and inorganic salts. Sebum also has some fungicidal and bactericidal effects. Slide 13-14
Slide 13-15
Sweat glands Entire skin surface except nipples and part of external genitalia Prevent overheating 500 cc to 1 L/day! (is mostly water) Humans most efficient Produced in response to stress as well as heat Slide 13-16
Sweat Glands Sweat glands are of two types: eccrine and apocrine. The eccrine glands are located over the entire skin especially in Forehead, palms and soles, surface and secrete an odorless, colorless fluid, the evaporation of which is vital to the regulation of body temperature. The apocrine glands are concentrated in the axillae, perineum, and areolae of the breast and are usually open through a hair follicle. They secrete a milky sweat. Slide 13-17
Types of sweat glands Eccrine or merocrine Most numerous True sweat: 99% water, some salts, traces of waste Open through pores Apocrine Axillary, anal and genital areas only Ducts open into hair follices The organic molecules in it decompose with time odor Modified apocrine glands Ceruminous secrete earwax Mammary secrete milk 18
HAIR Hair consists of layers of keratinized cells mid is found over much of the body except for the lips, nipples, soles of the feet, palms of the hands, labia minora, and penis. Hair develops within a sheath of epidermal cells called the hair follicle. Hair growth occurs at the base of the follicle, where cells in the hair bulb are nourished by dermal blood vessels. The hair shaft is visible above the skin; the hair root is surrounded by the hair follicle. Slide 13-19
HAIR Attached to the follicle are erector pili muscles, which contract in response to cold or fright, decreasing skin surface area and causing the hair to stand erect. There are two general types of hair: Vellus hair (Short, pale, and line and is present over much of the body.) Terminal hair (Particularly scalp and eyebrows) is longer, generally darker, and coarser than the vellus hair. Puberty initiates the growth of additional terminal hair in both sexes on the axillae, perineum, and legs. Slide 13-20
* Slide 13-21 * Arrector pili is s ooth uscle
HAIR Shaft has 3 layers of cells Medulla(central core) Cortex (bulky layer) Cuticle (heavily keratinized; protects hair) Hair growth: averages 2 mm/week Active: growing Resting phase then shed Hair loss: Thinning age related Male pattern baldness Slide 13-22
Why do humans have arrector pili muscles? 23
24
HAIR Hair color varies and is determined by the type and amount of pigment production. Amount of melanin for black or brown; distinct form of melanin for red. White: Decreased melanin. Genetically determined though influenced by hormones and environment Hair serves useful functions. Scalp hair is a protective covering. Nasal hair and ear hair, as well as eyelashes and eyebrows, filter dust and other airborne debris. Slide 13-25
NAILS The nails, located on the distal phalanges of lingers and toes, are hard, transparent plates of keratinized epidermal cells that grow from a root underneath the skin fold called the cuticle. The nail body extends over the entire nailbed and has a pink tinge as a result of the rich blood supply underneath. At the base of the nail is the lunula, crescentshaped area. The nails protect the distal ends of the fingers and toes. Slide 13-26
Nails Of hard keratin Corresponds to hooves and claws Grows from nail matrix 27
28
29
Any Question? 30
31
References Tortora, G. J., & Grabowski, S. R. (2003). Principles of anatomy and physiology (12th ed.). New York: Wiley. 32