BIOL235 Unit 1 Ch 5

Integumentary system

is composed of skin, hair, oil/swet glands, nails and sensory receptors

Dermatology

Study of integumentary system structure, function and disorders

Skin

cutaneous membrane; covers external surface of body and is largest organ

Epidermis

superficial, thinner portion of skin composed of epithelial tissue (avascular)

Dermis

deeper, thicker portion of skin composed of connective tissue (vascular)

Subcutaneous layer (hypodermis)

layer deep to the dermis but not part of skin consisting of areolar and adipose connective tissue

Lamellate/pacininan corpuscles

nerve endings that are sensitive to pressure in the subcutaneous layer and sometimes dermis

Keratinocytes

make up 90% of epidermal cells, arranged in 4-5 layers and produce keratin protein

Keratin

tough fiberous protein that protect skin and underlying tissue

Melanocytes

make up 8% of epidermal cells, developed from ectoderm in embryo and have long slender projections that extend between keratinocytes and transfer melanin granules to them

Melanin

yellow-red/brown-black pigment that contribute to skin colour, absorb UV light and protects keratinocyte nuclei

Intraepidermal Macrophage (Langerhans cells)

cells that arise from red bone marrow and migrate to epidermis

Tactile epithelial cells (Merkel cells)

least numerous epidermal cells, located in the deepest layer of the epidermis where they contact the flattened processes of sensory neuron

tactile disc (merkel disc)

flattened processes of sensory neuron

Thin skin

most regions of the body are covered in this which has 4 strata (layers) in its epidermis (Stratum Basale, Stratum Spinosum, Stratum Granulosum, and a thin layer of Stratum Corneum)

Thick skin

where exposure to friction is highest (fingertips, palms, soles) this which has 5 strata (layers) in its epidermis (Stratum Basale, Stratum Spinosum, Stratum Granulosum, Statum Lucidum and a thick layer of Stratum Corneum)

Stratum Basale

deepest layer of epidermis, composed of a single row of cuboidal or columnar keratinocytes (contains STEM cells that undergo cell division to continuously produce new keratinocytes)

Stratum Spinosum

layer superficial to the stratum basale, consisting of 8-10 layers of keratinocytes which at this level produce coarser bundles of keratin in intermidiate filaments than in basal layer, these cells are connected here by desmosomes and have intraepidermal macrophages and projections of melanocytes present

Stratum Granulosum

middle layer of epidermis, consists of 3-5 layers of flattened keratinocytes that are undergoing apoptosis

Keratohyalin

Darkly staining granules of protein that distinguish the stratum granulosum that assembles keratin intermediate filaments into keratin

Lamellar granules

fuse with plasma membrane and release a lipid rich secretion which are deposited between cells of stratum granulosum, lucidum, and corneum. This secretion acts as a water repellant sealant that prevents water entry, water loss, and inhibit the entry of foreign molecules

Statum Lucidum

layer present only in thick skin, consists of 4-6 layers of flattened, clear, dead keratinocytes that have large amounts of keratin and thickened plasma membranes

Stratum Corneum

most superficial layer of skin that consists of an average of 25-30 layers of dead flattened cells, but can range from just a few to 50+ cells. The keratinocytes in this layer are extremely thin, flat, and are plasma membrane enclosed keratin sacs with no more organelles. These dead cells overlap like scales.

Callus

constant exposure of skin to friction stimulates increased cell production and increased keratin production which lads to this abnormal thickening of the stratum corneum

Keratinization

process by which cells accumulate more and more keratin as they progress from one epidermal layer to the next

Epidermal Growth Factor

hormone like proteins that help promote increased cell division when outer layers of the epidermis need to be replaced

Dandruff

when an excessive amount of keratinized cells shed from the skin of the scalp

Dermis

second deeper part of the skin composed of dense irregular connective tissue containing collagen and elastic fibers; contains predominantly fibroblasts, some macrophages and few adipocytes near the subcutaneous layer; blood vessels, nerves, glands, and hair folicles reside in this layer

Papillary region

thin superficial layer of dermis containing collagen and fine elastic fibers

Dermal Papillae

small nipple shaped structures that project from the papillary region into the the epidermis underside

capillary loops

present in all dermal papillae; provide blood flow for gas exchange with epidermal tissue

Corpuscles of touch (Meissner Corpuscles)

present in some dermal papillae; nerve endings that are sensitive to touch

Free nerve endings

present in some dermal papillae; nerve endings that lack apparent structural specificating and give rise to feelings of warmth, coolness, tickling, pain, itch

Reticular region

thick deep layer of dermis attached to subcutaneous layer containing bundles of thick collagen fibers, scattered fibroblasts and various wandering cells; houses blood vessels, nerves, sebaceous glands, sudoriferous glands, and hair follicles between fibers

netlike

the arrangement of collagen fibers in the reticular region is _______ in structure

strength, extensibility, elasticity

the reticular region provides skin with what 3 properties

extensibility

ability to stretch

elasticity

ability to return to original shape after stretching

Epidermal ridges

cover surfaces of palms, fingers, soles and toes; develop in 3rd month of fetal development where epidermis projects downward into dermis between papillae

grip, tactile sensitivity

epidermal ridges increase ___ and _________ ability

Unique

epidermal ridges are ________ to every individual

Melanin, Hemglobin, Carotene

3 pigments that impart a wide variety of colours on skin

Melanin

causes skin to vary from pale yellow to reddish brown to black

number

the ________ of melanocytes is roughly the same in all people varience comes from the amount of pigment produced

Pili (hair)

columns of dead, keratinized, epidermal cells bonded together by extracellular proteins, present on most skin surfaces (not palmer surfaces), and mostheavily distributed on scalp, eyebrows, auxillae and around genital areas;

Hair shaft

superficial portion of the hair which projects above the surface of the skin

Hair root

portion of the hair deep to the shaft that penetrates into the dermis and sometimes the subctaneous layer

medulla

2-3 rows or irregularly shaped cells that often contain large amounts of pigment granules located most interiorly in the hair

cortex

forms major part of shaft and consists of elongated cells surounding the medulla

cuticle

outermost layer of the hair consisting of a single layer of thin, flat cells that are heavily keratinized, arranged like shingles with their free edges pointed towards the ends of the hair

Hair follicle

surrounds the root of the hair

external root sheath

portion of hair follicle formed by a downward continuation of the epidermis

internal rooth sheath

portion of hair follicle formed by matrix which creates a cellular tubular sheath

Epithelial root sheath

Root sheath formed by both the internal and external root sheath

Dermal root sheath

dense dermis surrounding hair follicle

Hair bulb

onion shaped structure at base of each follicle surrounding dermal root sheath

Papilla of the hair

part of the hair bulb that has nipple shaped indentations containing areolar connective tissue and many blood vessels

Hair matrix

part of the hair bulb that is made up of a germinal layer of cells that arise from the stratum basale, which are responsible for the growth of existing hairs and the replacement of shed hairs in the same follicle

Arrector pili

smooth muscle that extends from the superficial dermis of the skin to the dermal root sheath; whe contracted it pulls hair shaft perpendicular to the skin surface causing goose bumps

Hair root plexis

dendrites of neurons that suround each hair follicle that are sensitive to touch and movement of the hair

Skin glands

epithelial cells that secrete a substance

Sebaceous glands (oil glands)

simple, branched acinar glands, often connected to hair follicles and prevent hairs from drying out and becoming to brittle

Sebum

oily substance; mixture of triglycerides, cholesterol, proteins and inorganic salts (can inhibit growth of skin bacteria)

Sudoriferous glands (sweat glands)

simple, coiled tubular glands that release sweat into hair follicles or onto skin through pores

Eccrine sweat glands

sudoriferous glands that are most common; produce mostly water with some ions

Thermoregulation

homeostatic regulation of body temp

insensible perspiration

sweat that evaporates from the skin before it is percieved

sensible perspiration

sweat that is excreted in large amounts and is seen as moisture on skin

Emotional sweating

kind of sweating that can come from Eccrine and Apocrine sweat glands that occurs during emotional, stress, fear or embaressment. (sweating for this condition occurs first to palms, soles, and auxillae first

Apocrine sweat glands

sudoriferous glands with larger ducts and lumens, found mainly in axillae, groin, areolae, and beared facial region

exocrine

type of secretion of apocrine sweat glands despite name

bacteria metabolize fats

the sweat excreted from apocrine sweat glands has more fats and proteins which alone are odourless but _____________ making musky odour

sexual activity, emotional sweating, thermoregulation

apocrine sweat glans are active during _____________, and _________, but not _____________

Ceruminous glands

modified sweat glands in external ear that produce waxy lubricant; these ducts open directly to surface of ear canal or into ducts of sebaceous glands

Cerumen

combined secretion of ceruminous glands and sebaceous glands into the inner ear; impedes enterance of foreign bodys/insects, waterproofs canal and prevents bacteria and fungi from entering cells

Sebaceous glands (oil glands)

Distributed largely in lips, glans penis, labia minora, and tarsal glands; small in trunk and limbs; absent in palms and soles.

Eccrine sweat glands

Distributed throughout skin of most regions of body, especially skin of forehead, palms, and soles.

Apocrine sweat glands

Distributed through skin of axillae, groin, areolae, bearded regions of face, clitoris, and labia minora.

Ceruminous glands

Distributed in external auditory cannal

Sebaceous glands (oil glands)

found in Dermis exclusively

Eccrine sweat glands

Found in mostly deep dermis and sometimes upper subcutaneous layer

Apocrine sweat glands

Found in deep dermis and upper subcutaneous layer

Ceruminous glands

Found in Subcutanous layer

Hair follicles

Termination of Sebaceous glands (oil glands) secretory duct

surface of epidermis

Termination of eccrine sweat glands secretory duct

Hair follicles

Termination of apocrine sweat glands secretory duct

surface of external auditory canal, ducts of sebaceous glands

Termination of ceruminous glands secretory duct

Sebaceous glands (oil glands), Apocrine sweat glands

Glands that have onset of function during puberty

Eccrine sweat glands, Ceruminous glands

Glands that have onset of function soon after birth

Nails

plates of tightly packed, hard, dead keratinized epidermal cells that form a clear solid covering over the dorsal surfaces of the distal portions of the digits

Nail body (plate)

visible portion of nail; cells have harder type of keratin than skin, and cells do not shed like skin

Free edge

part of the nail that may extend past the digit (appears white because their are no underlying capillaries)

Nail root

Portion of the nail that is buried in a fold of skin

Lunula

whitish cresent shaped area of the proximal end of the nail body

Hyponychium

thickened stratum corneum under free edge of nail; junction between free edge and skin of finger tip, securing the nail to finger tip

Nail bed

skin below the nail plate that extends from the lanula to the hyponychium

Stratum Granulosum

the nail bed is missing this strata of the epidermis

Eponychium (cuticle)

narrow band of epidermis that extends from and adheres to the lateral boarder of the nail and consists of the stratum corneum

Hang nail

small torn piece of skin at side of base of fingernail/toenail caused by dryness of eponychium

Nail matrix

portion of epithelium proximal to nail root that divides mitotically to produce new nail cells