The Integumentary System
Human Anatomy and Physiology
Types of Membranes
S yn ovia llin es jo in ts ;m ad e o f C T
S erou slin es b od y cavit ies th a t lack op en in g s
to th e ou ts id e ; red u ce fric t ion
M u cou slin es cavit ies an d tu b es th a t
op en to th e ou ts id e o f th e b od y
C u tan eou sorg an o f th e in teg u m en ta ry
sys tem ; aka sk in
M em b ran es
Functions of the Integumentary System
Protective covering Prevents harmful
substances and organisms from entering the body
Reduces water loss from deeper tissues
Regulation of body temperature
Houses sensory receptorsContains immune system cellsSynthesizes vitamin DExcretes small quantities of wasteAbsorption of drugs and other agents
Components of the Integumentary System
SkinHairNailsSebaceous glandsSweat glands
Layers of the Skin
EpidermisDermisSubcutaneous layer (hypodermis)
Thick versus Thin Skin
Thick Skin Palms of hands
and soles of feet Hairless Subject to much
abrasion Thicker epidermis
(has an extra layer)
Thin Skin Found everywhere else
on the body Has hair Lacks one layer of the
epidermis
“Thick” and “thin” are not describing actual depth of tissue!!!
Thickest skin = upper back
Thinnest skin = eyelids
Epidermis
Stratified squamous epitheliumLacks blood vesselsGrows from the bottom layer (stratum basale)Keratinization
Layers of Epidermis
Stratum corneumStratum lucidumStratum granulosumStratum spinosumStratum basaleBasement membrane
Epidermal Layers
Stratum corneum – flattened cells, desicated, anucleate cells, keratinized Water barrier Varies in thickness Thickens with unusual amounts of friction
calluses
Stratum lucidum – in thick skin only, cells in process of keratinization
Epidermal Layers continued…
Stratum granulosum – only a few cells thick, appears granular Cells contain numerous keratin granules
Stratum spinosum – several cells thick, numerous cytoplasmic processes called spines, nuclei elongatedStratum basale – single layer of cells on bottom, contains skin stem cells Cells appear cuboidal or low columnar
Dermis
Epidermal ridges and dermal papillaeIrregular dense connective tissueThicker than epidermisMuscle and nerve fibers, blood vessels, hair follicles, sebaceous glands, and sweat glands2 layers: papillary and reticular
Layers of Dermis
Papillary layer Thinner,
superficial layer Loose CT Contains blood
vessels that serve the epidermis
Contains nerve processes
Reticular layer Varies in thickness,
but generally thicker than papillary layer
Contains thicker collagen and elastic fibers
May contain smooth muscle cells
Subcutaneous Layer/Hypodermis
Loose connective tissue and adipose tissueConnective tissue fibers are continuous with dermisPanniculus adiposus – layer of adipose tissue that insulates and stores energyArrector pili muscles originate here
Cells of the EpidermisKeratinocytes Main cell type Produce keratin
Melanocytes In stratum basale Contain melanin granules
Langerhans cells Involved in contact
dermatitis reactions
Merkel cells In stratum basale Most abundant in
fingertips Sense light touch
Skin Color
There are 3 pigments involved in skin color: melanin, carotene, and hemoglobin.Melanin is the only pigment made by the skin (from tyrosine) and ranges in color from yellow red-brown black.Skin color differences result from the kind and amount of melanin made and retained by the skin cells.All humans have relatively the same number of melanocytes.
Skin Color continued…
Freckles and moles are local accumulations of melanin.A tan is darkening of the skin as a result of increased melanin production, usually in response to prolonged exposure to UV radiation.Carotene is a yelloworange pigment found in certain plant products. It tends to accumulate in the stratum corneum and in the fat of the hypodermis, and it is more obvious when large amounts of carotene-rich foods are eaten.
Skin Color continued…Hemoglobin gives a pinkish hue to fair skin which is most noticeable in Caucasian skin. A more crimson pigment results when the hemoglobin is highly oxygenated. Hemoglobin is found in the RBCs of the dermal capillaries.Hair color is genetically determined and results from the amount and type of pigment secreted by melanocytes near hair follicles.Dark hair has more melanin than light hair. Red hair contains an iron pigment called trichosiderin, and gray hair is a mixture of pigmented and unpigmented hair.
Nerve Supply to the Skin
Free nerve endings found in the epidermis and papillary dermis sense temperature, vibration, pain, etc.Encapsulated nerve endings: Pacinian corpuscles – deep dermis and
hypodermis; sense deep pressure Meissner’s corpuscles – in papillary
region of dermis; sense light touch
HairPresent on all surfaces except for palms, soles, lips, nipples, and parts of external reproductive organsMade of keratinized cellsHair follicleHair papillaHair shaftHair colorArrector pili
Nails
Protective coverings on the ends of fingers and toesNail plateNail bedLunula
Sebaceous Glands
Sebaceous glands are associated with hair folliclesSebumFound everywhere except palms and solesAcne
Sweat GlandsIn dermis or superficial subcutaneous layerEccrine glands
Most numerous Produce sweat on hot days
and during exercise
Apocrine glands Become active at puberty Secretions smell because of
bacterial activity Active during emotional
upset, fright, pain, sexual arousal
Ceruminous glands and mammary glands
Healing of Wounds
Inflammation = normal response to injury or stressEpidermal cutsDeep cuts Blood clots Scabs Scars
Healing of BurnsFirst degree burns Superficial partial-
thickness burn
Second degree burns Deep partial-
thickness burn
Third degree burns Full-thickness burn
Rule of 9s
Aging and SkinEpidermal cells reproduce slower larger and more irregular shapeAge spots – sites of oxidation of fats in secretory cells of apocrine and eccrine glandsDermis reduces wrinkling and saggingDrier skin because of less oil from sebaceous glandsGray or white hair from decreased melanin production
Aging – continued…
Slower hair growth and fewer hair follicles thinner hair and/or hair lossLess blood supply to nail beds impaired growthDiminished sensitivity to pain and pressure because of fewer receptorsFewer sweat glands, fewer dermal blood vessels, and declined ability to shiver decreased ability to control temperatureDiminished ability to activate vitamin D reduced skeletal health
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