Integumentary System PDF

Integumentary System By Dr. Amal Elsheikh Department of Anatomy College of Medicine IAU  Skin Types of Skin Thick: covers palms of hands and soles of feet. Thin: covers rest of body, mostly hairy Thin Thick  Layers...

Integumentary System By Dr. Amal Elsheikh Department of Anatomy College of Medicine IAU  Skin Types of Skin Thick: covers palms of hands and soles of feet. Thin: covers rest of body, mostly hairy Thin Thick  Layers of Skin 1- Epidermis Stratified squamous keratinizing epithelium 2- Dermis Papillary layer of loose connective tissue and reticular layer of dense irregularly arranged Connective Tissue(CT) Hypodermis Subcutaneous tissue, loose CT, contains adipose tissue A. Epidermis – Stratified Squamous Keratinized Epithelium 5 4 Five Layers 2 1. Stratum basalis 2. Stratum spinosum 3 3. Stratum granulosum 4. Stratum lucidum 5. Stratum corneum 1 1. Stratum Basalis Consists of a single layer of columnar epithelial cells which rests on a well-developed basement membrane. Hemidesmosomes and desmosomes and many mitotic cell mitotic figures are detected. The cytoplasm contains tono-filaments. Cells containing melanin may be either melanocytes or keratinocytes cells with melanin 2. Stratum Spinosum It is formed of polygonal cells with central nuclei. The cells attached to each other by desmosomes. The attachment sites give spiny appearance. Another cytoplasmic feature is the appearance of membrane-coating granules (Odland bodies) 3. Stratum Granulosum Consists of flattened elongated cells containing in their cytoplasm irregularly shape non-membrane bound keratohyalin granules. Membrane-coating granules are discharged into the intercellular spaces (forming a skin barrier). 4. Stratum lucidum Stratum lucidum This layer is prominent in thick skin not in thin skin. Thin poorly staining clear layer consisting of flattened non-nucleated cells 5. Stratum Corneum This is the outermost layer of the epidermis. Consists of 15-20 layers of dead, flattened, anucleate, keratin-filled keratinocytes. protects against friction and water loss.  09:49 Thin Skin It covers all the body except the palms of hands & soles of feet. It differs from thick skin in: It contains hairs, hair follicles and sebaceous glands. Stratum lucidum is absent. Stratum spinosum& granulosum and corneum are thinner than those of thick skin. Principles of Skin  The Cell Types in Epidermis  1. Keratinocytes: Keratinocytes are the predominant cell type of epidermis and originate in the basal layer, produce keratin, and are responsible for the formation of the epidermal water barrier by making and secreting lipids.  2. Melanocyte : in the basal epidermis synthesize dark melanin pigment in melanosomes and transport these to adjacent keratinocytes, which accumulate them to protect nuclear DNA from UV damage.  3. Langerhan’s cells : Located in stratum spinosum. They are branched star shaped cells. The most characteristic feature of these cells are the Birbeck granules in their cytoplasm. Functions: Act as an antigen- presenting cells. It comprise a major component of the skin immunity.  4. Merkel’s cells : Located in the basal layer of epidermis. Their cytoplasm contain small dense neurosecretory granules near the basolateral cell membrane, which is in direct contact with the expanded, disc-like ending of a sensory nerve. Functions: mechanoreceptor for tactile sensation.  B. Dermis Layers of the Dermis Papillary layer  Underlies epidermis Dermal Papillae  Aerolar connective tissue  Supports, nourishes epidermis  Provides sensory nerves, lymphatics, and capillaries Reticular layer  Tough, dense, fibrous layer  Dense irregular connective tissue  Collagen fibers - limit stretch  Elastic fibers - provide flexibility Structures in the dermis The dermis consists of many structures in it. Most of these structures are ingrowths from the epidermis. The structures are, 1) Blood vessels 2) Sensory (touch) nerve endings 3) Sweat glands and their ducts 4) Hair follicles 5) Sebaceous glands 6) Arrector pili muscles  Structures in dermis Sebaceous glands :- These consist of secretory epithelial cells which secrete an oily secretion called sebum. Their ducts open into the hair follicle and soften the hair. These glands are present in hairy areas mostly Sweat glands :- These glands are widely distributed in skin. Each gland has a coiled body under the skin and duct opens on pores on the skin. The glands are Arrector pili muscles:- most numerous in palms of hands, These are small bundles of smooth muscles soles of feet, axilla and groin. attached to hair follicles. Contraction causes the hair to stand and causes goose flesh. Finger prints The surface of the epidermis is ridged by projections from the cells in the dermis called papilla. The pattern of these ridges is different in every person. These impression made by these ridges form the fingerprints.  C. The Hypodermis Hypodermis This layer contains adipose tissue and serves to attach the dermis to its underlying tissues. Epidermal appendages Structures that arise directly from the epidermis. These include: 1. Hair follicles 2. Sweat gland: eccrine and apocrine 3. Sebaceous gland 4. Nail 1. Hair follicles The hairs are a down growth of epidermal cells into the dermis. At the base of the follicle a cluster of cells is present called the bulb. The multiplication of cells in the bulb causes the hair to grow. The part of the hair inside is called the root and the part above the skin is called shaft.  2. Sweat glands Eccrine glands Apocrine glands Diagram showing two types of sweat glands present in the skin layer; one kind are the apocrine sweat glands which secrete fluid into the sac of hair follicle through which it eventually comes out on the skin. The other kind is the eccrine sweat gland which secretes sweat directly onto the surface of the skin. 3. Sebaceous Gland Simple branched acinar gland. They are present between the hair follicle and arrector pili muscle. Holocrine secretion – entire cell breaks up to form secretion Secretes an oily substance called sebum Sebaceous glands are absent in the palm and sole.  4. The Nails These protect the tips of the fingers and toes. The nail has a root embedded in the skin. The exposed part is called nail plate. The nail grows from the epidermis from a germinal part called nail bed. Cutaneous Nerve Endings Free nerve endings pain & temperature Merkel’s cells tactile sensation (in stratum basale) Meissner’s Corpuscles touch Pacinian Corpuscles. vibration & pressure Ruffini endings pressure Sources of Skin Color Melanocytes Make melanin from tyrosine Melanin provides UV protection Gives reddish-brown to brown-black color Carotene Contributes orange- yellow color Provided from diet (carrots and tomatoes) Hemoglobin - blood pigment THE FUCTIONS OF SKIN 1. Excretion: -Skin excretes some water and salts in sweat. 2. Protection: - Skin protects from bacteria, water and excess heat and cold. 3. Temperature regulation: -Skin plays a major role in regulation of body temperature. 4. Sensory function: -Skin is an organ for sense of touch, pain, temperature and pressure. 5. Production of Vitamin D is also a function of the skin THE CLINICAL NOTES ABOUT SKIN Preparation of skin for surgery: The skin harbors many bacteria. Before any operation or surgery the skin has to be prepared so that infection does not enter inside. This preparation includes, Shaving the hair in the area. Washing the sebum with soap. Cleaning the skin with an antiseptic. Burns Burns cause damage to skin due to fire, electricity or acids etc. The structure of the skin is damaged, and infection and water loss are the result commonly. Burns are classified according to their severity (depth) As 1 st, 2nd and 3rd degrees burns. First degree burn :- The epidermis is damaged only. This heals and leaves no scar. Second degree burn :- Damage to the epidermis and upper region of dermis. If carefully treated and infection prevented can heal without scar. Third degree burn :- Destroys the entire thickness of skin. There is no pain as nerve endings are destroyed. Regeneration is not possible and skin grafting must be done. Determination of the burnt area To determine the area burnt we use the rule of nines. This method divides the body into 11 areas each equal to 9% of the total body surface, plus 1% for perineal area. ( see diagram) Ulcers: Ulcers can occur on the skin on various regions. One type occurs over pressure points i.e. areas where the skin is compressed for long time between a bony prominence and a hard surface e.g. a bed or chair. These ulcers occur in patients bedridden for a long time or those confined to wheelchairs.