Lecture 1.04: Integumentary System

organs

made up of two or more tissues types working together to perform specific functions

four tissue types

epithelial, connective, muscular, nervous

lumen

the inside space or cavity enclosed by a membrane-bound organelle or tubular cellular structure

mucous membrane (muscosa)

epithelial lining and lamina propia (areolar ct)

serous membrane (serosa)

areolar ct and simple squamous epithelium (mesothelium)

visceral layer

contacts organ

parietal layer

lines the body cavity

serous fluid

secreted by serous membranes

synovial membrane

lines some joints of the body

synoviocytes

cell that create the lining of connective tissue

synovial fluid

secreted by synoviocytes

meningeal membranes (meninges)

line the cranial and vertebral cavities; associated with cerebrospinal fluid

cutaneous membrane (skin)

largest body membrane; epidermis (keratinized stratified squamous epithelium), dermis (areolar ct, dense irregular ct)

integument

epidermis and dermis layers

subcutaneous layer (hypodermis)

underlies the integument

functions of integument

protection, prevention of water loss and gain, temperature regulation, metabolic regulation, immune defense, sensory reception, secretion

epidermis

epithelial layer of the skin; keratinized stratified squamous epithelium, avascular, composed of several layers (strata)

epidermal strata

stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, stratum basale

thick skin

contains five layers of epidermis (includes stratum lucidum); found in palms (palmar surface) of hands and soles (plantar surface) of feet; no hair follicles or sebaceous glands

thin skin

lacks stratum lucidum, so have four epidermal layers that cover most of the body

stratum corneum

most superficial stratum of epidermis, thickness varies from 20 to 30 layers of dead, scaly, interlocking keratinized cells (keratinocytes) called corneocytes, cells are anucleate and tightly packed, cells from stratum basale take about 2 weeks to migrate to stratum corneum where they spend another 2 weeks, eventually shed from epidermal surface as flattened scales called squames, hair follicles or ducts of sweat glands may pass through this layer

stratum lucidum

thin, translucent region, two to three cell layers thick; present only in thick skin; palms of the hand and soles of the feet; cells lack organelles and are filled with eleidin, a transparent intermediate product of keratin maturation

stratum granulosum

three to five layers of keratinocytes undergoing keratinization; cytoplasm fills with keratin filaments and organelles degrade; keratohyalin granules involved in keratinization process; lamellar granules that release contents (lipids) into extracellular space which forms a cement that support the water barrier

stratum spinosum

several layers of polygonal cells; receives daughter cells from S. basale; keratinocytes attach to each other via desmosomes; some epidermal dendritic cells (Langerhan’s cells) present in this stratum

stratum basale (stratum germinativum)

single layer of cells, cuboidal, or columnar in appearance; cells are attached to the basement membrane; cell include kertinocytes, melanocytes, and tactile cells (merkel cells, found associated with axon terminals); most mitotically active layer with visible mitotic figures inside some cells; keratinocyte stem cells divide to replace keratinocytes shed at epidermal surface

melanin

pigment produced by melanocytes; eumelanin (brown, black), pheomelanin (yellow, red); increases with exposure to ultraviolet radiation; relative amounts of two types of melanin give people different complexions; all people have about the same number of melanocytes, activity varies

hemoglobin

oxygen-binding blood pigment inside erythrocytes; red in color

carotene

yellow-orange pigment from foods such as carrots; it builds up in the stratum corneum and subcutaneous fat

albinism

little or no melanin production; hair is white, skin is pale, irises of eyes are pink

vitiligo

partial or complete loss of melanocytes from patches of skin, results from an immune system malfunction

bronzing

hyperpigmented skin at joints appears bronze; related to hormones/medications; not a suntan

melasma

sun exposure related brown patches on the face

cyanosis

skin appears bluish as a result of oxygen deficiency in blood; peripheral cyanosis in cold weather

erythema

skin appears abnormally red; dilation of blood vessels; common feature of rosacea

hematoma

collection of blood outside of a blood vessel; a bruise (contusion) is observable through the skin

jaundice

skin and sclera (white of the eyes) appear yellowish; excess of the pigment bilirubin in the blood

pallor

skin appears ashen, pale; tongue and eyelids can be diagnostic; could be emotional shock, stress, anemia

nevus

also known as a mole; localized overgrowth of melancytes

freckles

yellow or brown spits of high melanocyte activity

hemangioma

proliferation of blood vessels that form a benign tumor

capillary hemangioma

strawberry birthmarks; raised and red to purple; may appear/disappear in childhood

cavernous hemangiomas

port wine stains; flat and involve larger dermal vessels; may last a lifetime

friction ridges

folds of epidermis and dermis on fingers, palms, soles, and toes; increase friction for grasping

dermis

has two layers: papillary layer, reticular layer

papillary layer

superficial; adjacent to epidermis, composed of areolar ct

dermal papillae

projections of the dermis toward the epidermis; interlock with epidermal ridges increasing surface area between epidermis and dermis; contain capillaries that supply nutrients to the epidermis and also contain sensory receptors (Meissner’s corpuscles)

reticular layer

deeper and thicker layer; composed of dense irregular ct; large collagen bundles project in all directions; includes many blood vessels, glands, hair follicles, nerves, and pacinian corpuscles

blood vessels

help control body temperature and blood pressure

vasoconstriction

narrowed diameter of vessels; reduces blood flow to skin, helps conserve heat

vasodilation

widening diameter of vessels; increases blood flow to skin, helps release heat

lines of cleavage

tension lines; identify the orientation of fiber bundles

striae

stretch marks; when skin is overstretched from rapid growth and shrinkage, collagen fibers may tear

innervation

nerve fibers are extensively dispersed in dermis; monitor sensory receptors, control blood flow, control glandular secretion

sensory receptors in the skin

free (bare) nerve endings (ex. nociceptors); encapsulated receptors

nerves associated with hair

hair root plexus is sensory; motor neurons to glands and arrector pili muscle