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