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  1. 1. General Histology and Histotechnique (1st semester; 2012-2013) by K-DumlaoINTEGUMENTARY SYSTEMFunctions:1. Body temperature regulation.2. Reservoir for blood3. Protection from external environment4. Cutaneous sensations5. Excretion and Absorption6. Vitamin D synthesisComposition:- Skin- Accessory structures: o Hair o Nails 1. Keratinocytes: keratin & lamellar granules o Various glands - 90% of the epidermal cells - Produced keratin (protein)Skin  Tough fibrous protein that help the skin- Largest organ of the body from heat, microorganisms, underlying tissues of skin and chemicals.Two principal parts: - Lamellar granules  Stratum granulosum1. Epidermis  Functions: Releases a water and proofing- Superficial portion sealant- With 5 layers2. Dermis- Inner portion- With 2 regions 2. Melanocytes: melanin - 8% of the epiderma cells - Produce pigment – melanin  skin colorEpidermis- A keratinized stratified squamous epithelium- Consists of 4 principal types of cells: 3. Langerhans cells - Arise from the bone marrow - Migrate to epidermis - Participate in immune responses
  2. 2. General Histology and Histotechnique (1st semester; 2012-2013) by K-Dumlao - Shed off when you take a bath  Continuous Friction - Callous  an abnormal thickening of epidermis due to friction 2. Stratum Lucidum - “lucid” – “clear” - Present in the skin of finger tips, palms, and soles. - 3 – 5 clear layers of flat dead keratinocytes with intermediate filaments and thickened plasma4. Merkel cells membrane.- It is the least numerous of epidermal cells- Located at the deepest part of stratum 3. Stratum Ganulosum basale/geminativum. - 3 – 5 layers of flattened keratinocytes- In contact with tactile disc or merkel disc - Consists of keratohyaline and lamellar granulesFunction: o A distinctive feature of the layer- Both participate in sensation of touch o Darkly staining granules of the stratum Function: Organized intermediate filaments into thicker bundles. 4. Stratum Spinosum - The superficial of basale - 8 – 10 layers of polyhedral keratinocytes - Fit closely together - Thorn – like spines bundles of intermediate filaments of the cytoskeleton joins the cell tightly to one another to provide strength and flexibility ofLayers of the Epidermis the skin. 5. Stratum Basale/Geminativum - Active in cell division - Compose of one layer of simple cuboidal/columnar keratinocytes.  Some considered them as stem cells  Continue cell divisions to produce new keratinocytes - Merker cell - Melanocytes Dermis - Second deeper part of the skin - Composed of connective tissue containing collagen and elastic fibers1. Stratum Corneum o Functions: for extensibility (stretch; obesity)- 25 – 30 layers of dead flat keratinocytes. and flexibility (Return to its original form)- Contains the dead flat intermediate filaments - Include cells such as fibroblasts, macrophages, and- Consists of keratohyaline some adipocytes o Function: Water repellant barrier - Blood vessels, nerves, glands, and hair follicles are- Lamellar granules embedded in dermal tissue- Lipid from lamellar granules (barrier in between)
  3. 3. General Histology and Histotechnique (1st semester; 2012-2013) by K-DumlaoTwo regions of Dermis: 3. Meissner’s corpuscle - Encapsulated1. Papillary region - Palmar and planthar- The superficial portion of the dermis - Fingertips- Consists of areolar connective tissue with tissue with elastic fibers 4. Ruffini corpuscles- Contains dermal papillae - Type II cutaneous mechanoreceptor  Finger-like projections that indent the epidermis to the dermis. 5. Pacinian corpuscleContains the following: - Located deeper part of the dermis - Encapsulated with multicellular ovoid structuresa. Meissner’s corpuscle Function: Respond to deeper pressure.- For touch sensationb. Free nerve endings- Contains the dendrites that initiates signals that are felt such as warm, coolness, pain, tickling and itching.*Papillary layer – small fine collagen2. Reticular region- Deeper portion of dermis- Consists of dense irregular connective tissue containing bundles of collagen and some elastic fibers.*Reticular layer – more coarsely-textured collagenfibers. Functions of the connective tissue of the dermis: 1. Tough collagen fibers and resilient elastic fibers provide mechanical strength for skin. Lines of tension in the dermis called Langer’s lines, affect healing after surgical incision 2. The ground substances of the dermis serve as the substrate for diffusion of nutrients and wastes to and from various other tissue components. 3. Mast cells, lymphocytes and macrophages in the connective tissue carry our surveillance for the immune system. 4. Finally, the dermis together with its associated blood vessels and nerves is capable of active responses to injury, yielding the defensive reactionSensory receptors / free nerve endings of the reticular of inflammation, followed by the healing processeslayer: of growth and repair1. Nociceptotrs – pain receptor Subcutaneous layer (Hypodermis)2. Tactile/Merkel disc - The hypodermis (hypo – “under” + dermis – “skin”)- Type one cutaneous mechanoreceptor or subcutaneous (sub – “below” + cutaneous) layer- For sensation touch
  4. 4. General Histology and Histotechnique (1st semester; 2012-2013) by K-Dumlao lies below the skin and is made up of loose - Scatters light from the dermis without altering its connective and adipose tissues. color- The hypodermis binds the skin to underlying organs - Whiteness of white skin while allowing the skin to move somewhat - Reflection of collagen independently of underlying structures.- Adipose tissue in the hypodermis provides padding 3. Blood and shock-absorption that helps to protect - Hemoglobin and RBC underlying tissues from damage; it is also important - Scatters red light in insulating against loss of body heat. - Responsible for the pinkness in pigmented skin- Because the subcutaneous layer contains numerous ***The amount of pigment, the thickness of dermis, blood vessels but no vital organs, it is a near-ideal and the degree of perfusion in dermal capillaries vary. place to inject drugs. This is why so many drugs are administered through subcutaneous injection by a Skin texture hypodermic (hypo-“under”+ dermic – “skin”) - Affect the thickness and smoothness of the needle. epidermis, by the quality of fibers in the dermis, and by the amount of fluid in dermal connective tissue.Types of skin Note:1. Thin skin Both edema (accumulation of excess fluid in connective- Covers all parts of the body except palms, palmar tissue) and dehydration can dramatically alter the surfaces of the digits, and soles appearance of skin- Epidermis is thin- Stratum lucidum lacking; stratum spinosum and Accessory structures of the skin stratum Corneum are thin 1. Hairs- Has fewer dermal papilla, lacks epidermal ridges 2. Glands- Has hair follicles, arrector pili muscle and oil glands 3. Nails but fewer sweat glands than thick- Sparser distribution of sensory receptors. Hairs - Composed of columns of dead, keratinized cells2. Thick skin bounded together by extracellular proteins- Covers palms, palmar surfaces of digits and soles Parts:- Thick epidermis 1. Shaft – superficial portion- With stratum lucidum and thicker stratum 2. Roots – penetrates into the dermis spinosum and stratum corneum. Concentric layers of shaft and root:- More numerous dermal papillae thus has epidermal ridges a. Medulla- Lack hair follicles, arrector pili muscle, sebaceous - Inner portion gland. - 2 or 3 rows of polyhedral-shaped cells containing- Has more sweat glands that thin skin pigment granules and hair spaces.- Sensory receptors are more densely clustered. b. CortexSkin color - Middle portion - It forms the major part of the shaft1. Melanin - Contains pigments granules of the hair- Produced by melanocytes - White/gray hair – air bubbles- Yellowish-brown color of the epidermis- Lesser melanin – Light will penetrate easily into the c. Cuticle skin --- prone to cancer. - Outermost layer - Single layer of flat cells that are heavily keratinized2. Collagen
  5. 5. General Histology and Histotechnique (1st semester; 2012-2013) by K-Dumlao 3. Follicle – tubular invagination lined by stratified squamous epithelium similar to epidermis; 6. Hair root plexuses surrounds the root of the hair; made up of: - Dendrites of neurons sensitive to touch a. External root sheath - Generate nerve impulses in hair shaft is moved.- Downward continuation of epidermis- Contains the stratum basale Glands b. Internal root sheath- It forms the cellular tubular sheath between the external root and the hair.Hair follicles are associated with:a. Sebaceous glands – secrete oil into the hair follicle as well as nerve ending and smooth muscle to form the pilosebaceous apparatus.b. Nerve endings – detects deflection of the hair shaft and also controls piloerection.c. Smooth muscle – arrector pili ; affect piloerection 4. Bulb – the base of hair follicle; onion-shaped structure; houses a. Papilla of the hair- Nipple-shaped indentation- Contains areolar connective tissue- A lot of Blood vessels that nourish the growing hair follicle b. Matrix- Germinal layer of the cell w/c rise from stratum basale.Function:- Responsible for growth of existing hairs- Produce new hairs when old hairs are shed.  Sebaceous glands 5. Arrector pili muscle – smooth muscle cells - Associated with hair follicles- Stimulated by autonomic nerve endings to contract - Holocrine glands pulling the hair shaft perpendicular to the skin  The whole cell is secreted surface during cold or fright.
  6. 6. General Histology and Histotechnique (1st semester; 2012-2013) by K-DumlaoFunction:- It coats the surface of the hair and help keep them from drying and becoming brittle- It prevents excessive evaporation of water from the skin.- It keeps the skin soft and pliable- It inhibits growth of certain bacteria Sweat glands- 3-4 millions producing their secretion- Exocytosis – release secretionTwo types:a. Ecrine 1. Nail body – visible portion of the nail- Simple coiled tubular gland 2. Free edge – part of that may end pass the distal- Common sweat gland ends of digitsFunction: 3. Nail root – proximal edge of the nail plate that- Regulates body temperature is buried in the skin.- Waste removal 4. Lunula – whitish crescent shaped covered by portion of the nail bed.b. Apocrine 5. Hyponichium – nail bed; skin of nail bed;- Simple coiled tubular gland provide support- Stimulated during emotional stress and sexual 6. Eponychium/cuticle – a horny epidermal excitement extension of the tip of the nail folds.- Secretion of cold sweat Nails- Plates of tightly packed, hard, keratinized epidermal cells.- Cells form a clear, solid covering over the dorsal surfaces of the distal portions of the digits- Parts: