exercise 7 integumentary system. functions protection insulates & cushions underlying body...
TRANSCRIPT
Exercise 7
Integumentary System
Functions
Protection Insulates & cushions underlying body
tissues Protects from mechanical damage,
chemical damage, thermal damage & bacterial invasion
Prevents water loss Regulates heat loss
Basic Structure
2 distinct regions Epidermis- superficial, composed of
epithelium Dermis- underlying connective tissue
Hypodermis (superficial fascia)- not part of skin; primarily adipose tissue
Epidermis
Avascular Keratinized, stratified squamous
epithelium 4 cell types 5 layers
Epidermal Cells
Keratinocytes Most abundant epidermal cells Produce keratin fibrils Keratin gives epidermis its durability Keratinocytes connected by
desmosomes Know figure 7.1
Epidermal Cells (continued)
Melanocytes Black cells that produce melanin Melanin production increases with
exposure to UV light (sunlight) Melanin protects cell nuclei by
shielding DNA from UV radiation Freckles are a concentration of
melanin in 1 spot
Epidermal Cells (continued)
Langerhans’ cells Immunity
Merkel cells Form touch receptors called Merkel
discs at epidermal-dermal junction
Epidermal Layers
Skin covering most of the body has 4 layers
Thick skin (palms of hands, soles of feet) has 5 layers
Know figure 7.2
Epidermal Layers (continued)
Stratum basale Basal layer Single row of cells adjacent to dermis Constantly undergoing mitotic
division to produce new cells Also called stratum germinativum
Epidermal Layers (continued)
Stratum spinosum Spiny layer Several cell layers immediately
superficial to basal layer Divide fairly rapidly
Epidermal Layers (continued)
Stratum granulosum Granular layer Thin layer 2 types of granules
Lamellated- contain a water-proofing glycolipid
Keratohyaline- combine with intermediate filaments to form keratin fibrils
Epidermal Layers
Stratum lucidum Clear layer Very thin & translucent Not present in regions of thin skin
Epidermal Layers (continued)
Stratum corneum Horny layer Outermost layer Accounts for bulk of epidermal thickness Cells are dead Fully keratinized Constantly being rubbed off & being
replaced by division of deeper cells
Dermis Dense irregular connective tissue 2 principal regions
Papillary layer Reticular layer
Both layers heavily invested with collagenic & elastic fibers, which give skin its elasticity
Abundant blood supply helps play a part in regulation of body temperature
Decubitus ulcers can form in bedridden patients who are not turned regularly; weight of the body exerts pressure, which restricts blood supply and leads to tissue death
Dermis (continued) Papillary layer
More superficial region Areolar connective tissue Attached to epidermis by dermal papillae (these also
produce finger prints) Abundant capillary networks Have pain & touch receptors (Meissner’s corpuscles)
Reticular layer Deepest skin layer Dense irregular connective tissue Contain arteries & veins, sweat & sebaceous glands,
and pressure receptors (Pacinian corpuscles)
Skin Color Result of:
Relative amount of melanin Relative amount of carotene Degree of oxygenation of blood
Can be a diagnostic tool Flushed skin may indicate hypertension, fever,
embarassment Pale skin may indicate anemia Bluish cast (cyanosis) may indicate inadequate
oxygenation from asphyxiation or respiratory insufficiency
Jaundice (yellowed tissues) usually means liver disease Bronzing of skin may be from hypoactive adrenal
cortex (Addison’s disease)
Accessory Organs Nails, hair, cutaneous glands Nails
Derivatives of epidermis Body- visible attached portion Free edge- portion that grows out away from body Root- embedded in skin; adheres to nail bed Nail folds- overlap borders of the nail Eponychium- cuticle Nail bed- extension of stratum basale Nail matrix- proximal part of nail bed containing germinal
cells; cells become keratinized & die Lunula- proximal region of matrix, appearing as a white
crescent Know figure 7.4
Hair & Associated Structures Hair
Consists of medulla surrounded by cortex & cuticle
Color is a manifestation of amount & kind of melanin
Root- portion enclosed within follicle Shaft- projects from surface of scalp Hair bulb- collection of germinal epithelial
cells; as cells are pushed from growing region, they become keratinized & die
Know figure 7.5
Hair (continued)
Follicle Formed from epidermal & dermal cells Papilla protrudes into hair bulb &
provides nutrients for growing hair Arrector pili muscle
Smooth muscle cells connect each follicle to papillary of dermis
Contraction causes goose bumps
Cutaneous Glands
2 types Sebaceous (oil) glands
All over the skin, except palms & soles Ducts usually empty into hair follicle Product is sebum, a mixture of oil & cells
that keeps skin soft & moist & keeps hair from becoming brittle
Become very active during puberty
Cutaneous glands (cont.) Sudoriferous (sweat) glands
Widely distributed Empty through pores 2 types
Eccrine (merocrine sweat glands) Found all over the body Produce clear perspiration; mostly water, salts
& urea Important in heat regulation
Apocrine Mostly in axillary & genital areas Secrete a milky protein- & fat-rich substance May contain pheromones
Know figure 7.7
Exercise 8
Classification of Covering and Lining Membranes
Epithelial Membranes Organ consisting of a epithelial sheet bound to
an underlying layer of connective tissue 3 main types
Cutaneous membrane (skin) Mucous membranes (mucosae)- epithelial cells on a
layer of loose connective tissue (lamina propria); line all body cavities open to exterior (respiratory, digestive, urogenital); constantly bathed by secretions
Serous membranes (serosae)- layer of simple squamous epithelium on a small amount of areolar connective tissue; usually paired; parietal layer lines body cavity, visceral layer covers outside of organs in that cavity; secretes serous fluid, which lubricates organs
Know figure 8.1
Synovial Membranes
Composed entirely of connective tissue
Line cavities surrounding joints Secrete a lubricating fluid Also line smaller sacs of connective
tissue (bursae & tendon sheaths) Know figure 8.2
Histology reviewBe able to identify muscle tissue: skeletal, smooth and cardiac by sight.
Be able to identify the following epithelia by site:simple squamous (kidney glomeruli)simple cuboidal (kidney tubules)simple columnar (digestive tract)pseudostratified columnar (upper respiratory tract)stratefied squamous (skin)stratefied cuboidal (ducts of sweat glands)stratefied columnar (ducts of large glands, male urethra)transitional (stretchy bladder)
Connective tissue: Bone, Blood, areolar, embryonic (mesechymal), adipose, dense, loose, cartilage
Cartilage (connective tissue)
Hyaline-trachia, sternum
Elastic cartilage Ear, epiglottis
Fibrocartilage Intervertabral discs