Integumentary System 2023-1.ppsx

Integumentary System Skin & Related Structures (Chapter 6) OBJECTIVES • Learn the general functions of skin • Describe the layers of the epidermis & the epidermal cell types & their functions • Describe the process of keratinization • Describe the dermal structures & their functions • Describe s...

Integumentary System Skin & Related Structures (Chapter 6) OBJECTIVES • Learn the general functions of skin • Describe the layers of the epidermis & the epidermal cell types & their functions • Describe the process of keratinization • Describe the dermal structures & their functions • Describe structures & functions of the hypodermis • Describe unique features of foot pads & nasal planum • Learn the functions of hair/fur & describe the types of hair, the parts of hair follicles & how hair grows • Describe the structure, location & function of sebaceous glands & other skin glands Integumentary System      Composed of all 4 tissue types Includes hair, horns, hooves & claws, as well as skin-related glands Outer layer composed of dead cells Keratinization occurs as the cells die Protective & regulatory functions General Functions of Integument       Covers & protects underlying structures Prevents desiccation Assists in maintenance of normal body temperature Excretes water, salt & organic wastes Sensory organ – relays tactile & pressure info to CNS Vitamin D synthesis & nutrient Integument = Skin   2 layers  Epidermis – keratinized stratified squamous epithelium  Dermis (corium) – dense fibroelastic connective tissue Hypodermis = subcutaneous layer/subcutis  primarily adipose tissue for thermo insulaton & mechanical shock absorption  Pressure receptors = pacinian corpuscle  allows skin to move freely over Epidermis (Cells & Their Functions)   Keratinocytes – majority of epidermal cells Produce keratin = tough, fibrous, waterproof protein -> gives skin its resiliency & strength Melanocytes – produce melanin = dark brown-black pigment stored in membrane bound granules called melanosomes -> absorbed by keratinocytes -> melanin protects from UV exposure Epidermal Cells   Langerhan’s Cells – macrophages only found in epidermis -> originate in bone marrow & migrate to skin -> phagocytize microbes & stimulate other cells of immune system Merkel Cells – form Merkel disks w/ sensory nerve ending at epidermaldermal junction -> thought to aid in touch sensation Epidermal Layers (Deepest to Most Superficial)      Stratum germinativum (stratum basale)  Attached to epithelial basement membrane  New cells produced here and move up Stratum spinosum (spiny layer)  Langerhan’s cells located here Stratum granulosum (granular layer)  Keratinization occurs here Stratum lucidum (clear layer)  Keratinized clear cells, only in very thick skin areas Stratum corneum (horny layer)  Outermost, thickest layer  Cornified remnants of keratinocytes (dandruff) Keratinization  Produces keratin, a type of surface specialization, providing protection & waterproofing for skin’s surface  As older cells travel up from basal layer, they fill w/ keratohyaline & glycolipid granules , lose their nuclei, cytosol & organelles and become dead sheets of keratin -> dead cells & keratin slough off as dander/dandruff Dermis  Makes up the largest part of the skin  Provides structural strength of the skin  Composed of 2 layers:  papillary - loose connective tissue with fibers & ground substance; just beneath epidermis; forms dermal papillae  reticular - irregular connective tissue containing collagen, elastic & reticular fibers; 80% of dermis; most fiber bundles run parallel to one another, orientation depends on direction of the stress placed on them  Few cells compared to epidermis, including fibroblasts, adipocytes & macrophages  Contains hair follicles, nerve endings, touch (Meissner’s corpuscles) & temperature receptors, glands, smooth muscle, blood vessels & lymphatics Special Features of Integument Foot/Paw Pads = Thick layers of fat & connective tissue w/ tough, thick outer epidermal surface that is often pigmented & is composed of all 5 epidermal layers   Bear the weight of the animal  Protection against abrasion  Protection against thermal extremes  Sweat glands are functional & secrete onto the surface of the Special Features of Integument  Planum nasale (=nasal planum) Top of the nose in dogs, cats, pigs and sheep & goats Called planum nasolabiale in horses & cattle = only 3 epidermal layers in the dog; usually pigmented; no glands in epidermis or dermis in dog; tubular  Special Features of Integument Ergots & Chestnuts  Dark brown, horny patches on legs of horses & other equid species (See Figure 6.7 on pg 161) = vestiges of carpal & tarsal pads of the 2nd & 4th digits and the 1st digit, respectively  Cutaneous Pouches of Sheep    Infraorbital Interdigital Inguinal = Infolding of skin forming pouches containing sebaceous (oil) glands -> secretions used in marking territory, courtship, etc. Functions of Hair / Fur  Thermoregulation – insulate by trapping layers of air -> erection of hairs when cold (see below)  Camouflage – coat color (melanin/pheomelanin)  Intra- & Interspecies Communication – erection of hair when aroused or frightened    Degree of erection = implantation angle Arrector pili muscle – smooth muscle attached to hair follicle & innervated by sympathetic nervous system Touch perception – tactile hairs = sinus = tylotrich hairs = whiskers (used as probes)  Also are mixed intermittently throughout the Hair Growth Cycles   Anagen Phase – active growth when hair shaft lengthens Telogen Phase – quiescent, resting phase occurring when maximum length achieved, hair stops growing & follicle shortens   Telogen Effluvium – loss of large % of hair volume at one time due to metabolic stress or illness Catagen Phase – transitional period between anagen & telogen phases Skin Glands Sebaceous Glands     Located in dermis (not in foot pads or nasal planum) Simple or compound acinar gland; holocrine Duct empties into hair follicle -> arrector pili muscle squeezes secretion out or empties directly onto surface of skin Secretion = sebum (lanolin in sheep) – thick & oily -> composed of glycerides & free fatty acids -> coats hair & traps moisture -> keeps skin moist & supple; some antibacterial & antifungal properties  Can clog follicle causing whiteheads that turn black -> comedones (blackheads) that can Skin Glands Sweat (sudoriferous) glands  Present in most domestic species but only functional (produce sweat) in horse & to lesser extent in ruminants  2 Types (both merocrine secretion)   Eccrine – empty onto skin surface - simple, coiled tube in dermis connected to skin surface by a long duct; in foot pads & deep layers of fat in dogs Apocrine – empty into hair follicles – single, coiled secretory/excretory duct; in external ear canals of dogs Skin Glands Tail Glands  Oily patch at dorsal base of tail in dogs & cats  Sebaceous & apocrine glands  Assists in communication of identification of individuals; sensitive to sex hormone levels Anal Sacs  Lined w/ sebaceous & apocrine glands  Stores secretion produced -> expressed during defecation or when animal is frightened or excited  Used in marking territory & attracting mates Claws/Hooves, Horns & Antlers Claws & Hooves  Hard outer layer composed of keratin; inner layer = corium = modified dermis  For maintaining traction when running, walking & climbing  For catching prey  For defense Horns (ruminant ungulates) / Antlers (Cervids)  Horns are epidermal origin; structurally similar to hair  Antlers are dermal bone & arise from skull; found primarily in males & are shed annually  Function in defense & offense / courtship