Exam 2 Compilation Notes
Exam 2 Compilation Notes BSC 215
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Chapter 5 Histology Intro to Tissues Tissue groups of cells that are similar in structure and cooperate to perform related functions epithelial covering connective support nervous control muscle movement Histology study of tissues Epithelial Tissue sheets of cells that cover body surface envelops organs and lines body cavities surrounds our veins etc forms critical boundaries between different environments external vs internal between various internal environs two broad epithelial types coveringlining and glandular Main Functions protection from pathogens UV light etc absorption ie on surface of intestines Filtration in veins and arteries as well as in kidneys Excretion releasing waste Secretion releasing something needed by the body Sensory Reception skin is exposed to outside environment uses nerve endings Characteristics polarity consist of apical and basal surfaces apical exposed to external environment or cavities of organs often possess microvilli or cilia basal site of attachment to other tissues associated with basal lamina noncellular glycoprotein mixture that serves a s a filter for substances diffusing from underlying connective tissue and a migration path Specialized Contacts epithelial cells fit tightly together tight junctions with help from desmosomes prevent materials form apical surface from diffusing to basal surface don t want hydrochloric acid to penetrate through stomach to lining Supported by Connective Tissue reticular lamina deep relative to basal lamina consists of network of fibers emanating from underlying connective tissue reticular lamina basal lamina basement membrane reinforces epithelial cell layer resists tearing Typically avascular obtains nutrients by diffusion selective from underlying connective tissue layer lnnervated nerve fibers are present Regeneration capability of cell division often at a high rate Epithelial Tissue Classificaton 1st word number of cell layers simple or stratified simple single layer functions in absorption and filtration stratified multilayer functions in areas of high abrasion 2nd word cell shape squamous cuboidal or columnar cell shape is usually given away by nucleus shape Simple Squamous Epithelium endothelium friction reducing lining of cardiovascular mesothelium serous membranes lining body cavity and organs description single layer of flattened cells with discshaped central nuclei and sparse cytoplasm function allows passage of materials by diffusion and filtration in sites where protection is not important secretes lubricating substances in serosae location kidney glomeruli air sacs of lungs Simple Cuboidal Epithelium description single layer of cube like cells with large spherical and central nuclei function secretion and absorption location kidney tubules ducts and secretary portion of small glands ovary surface Simple Columnar Epithelium description single layer of tall cells with round or oval nuclei some cells bear cilia layer may contain mucussecreting unicellular glands goblet cells function absorption secretion of mucus enzymes and other substances location nonciliated type lines most of the digestive tract gallbladder and excretory ducts of some glands ciliated variety lines small bronchi uterine tubes Pseudostratified Columnar description single layer of cells of differing heights some not reaching the free surface may contain goblet cells and bear cilia function secretion particularly of mucus propulsion of mucus by ciliary ac on location nonciliated type in male s spermcarrying ducts and ducts of large glands ciliated variety lines the trachea and most of the upper respiratory tract Stratified Squamous apical cells squamous deeper cell layers are cuboidal or columnar basal cells actively divide and push apically to replace surface cells basal cells have access to nourishment from connective tissue apical cells have less access and atrophy far tougher than simple epithelium present in areas of high use description thick membrane composed of several cell layers basal cells are cuboidal or columnar and metabolical active surface cells are flattened squamous in the keratinized type the surface cells are full of keratin and dead basal cells are a cite in mitosis and produce the cells of more superficial layers function protects underlying tissues in areas of high abrasion location nonkeratinized tpe forms the moist linings of the esophagus mouth and vagina keratinized variety forms the epidermis of the skin a dry membrane Stratified Cuboidal Epithelium rare exists in ducts of sweat and mammary glands two layers of cuboidal cells Stratified Columnar rare exists in pharynx male urethra glandular duct linings Transitional Epithelium description lines hollow urinary organ can stretch easily to accommodate liquid volume basal layer is cuboidal or columnar apical layer vary in appearance with organ distention function stretches readily and permits distention of urinary organ by contained urine location lines ureters bladder and part of the urethra major arteries and veins Connective Tissue Most abundant and widely distributed tissue in the body Connective Tissue Proper adipose and ligaments Cartilage Osseous Tissue bone Blood Function provide binding and support protection physical and immune movement in terms of ligaments and tendons heat production and insulation adipose tissue storage adipose tissue transport of substances Defining Characteristics originates from mesenchyme embryonic mesoderm we are triploblasts organisms because we have three layers of tissues at the beginning of our life varying degrees of vascularity from none to richly possess extracellular matrix Structural Elements ground substance fills space between cells and contains fibers interstitial fluid cell adhesion proteins allow cells to attach to elements of ECM proteoglycans protein with glycosaminoglycans GAC s attached serves as the medium through which nutrients can diffuse between capillaries and cells What s a GAC negatively charged polysaccharide that project from core protein traps water and generates viscosity of the ground substance Fibers support system collagen strongest of them all a fibrous protein secreted into ECS and bundle together into thick collagen fibers high tensile strength Elastic long thin and branching composed of protein called elastin ability to stretch and RECOIL very important in areas where elasticity is necessary skin lungs blood vessel walls Reticular Fibers short fine and collagenous form delicate networks around small blood vessels support soft tissues of organs abundant where connective tissue comes into contact with epithelial tissue Connective Tissue Cell Types undifferentiated cells are called blasts actively mitotic secrete ground substance and fibers for extracellular matrix Fibroblasts connective tissue proper Chondroblasts cartilage Osteoblasts bone Hematopoietic Stem Cell blood not located within tissue and doesn t produce matrix Once matrix is secreted cells become cytes not actively mitotic no longer secrete ground substance or fibers but can resort back to blasts Fibrocytes connect tissue proper Chondrocytes cartilage Osteocytes bone Erythrocytes and Leukocytes blood Connective tissue types differ in their cell type fiber type and amounts of fiber Connective Tissue Proper Looses Connective Tissue Areolar supports andbinds fibers holds body fluids ground substance defends against infection has WBC and macrophages stores nutrients fibroblasts dominant cell type loose arrangement of fibers reservoir for salts and water all body cells obtain nutrients and release wastes here lots of GGAC s hyaluronic acid very viscous Description gellike matrix with all three fiber types cells fibroblasts macrophages mast cells and some white blood cells function wraps and cushions organs its macrophages phagocytize bacteria plays important role in inflammation holds and conveys tissue fluid location widely distributed under epithelia of body eg forms lamina propria of mucous membranes surrounds capillaries Connective Tissue Proper Loose Connective Tissue White Adipose adipocytes dominant cell type storage fro triglycerides pushes nucleus to side cytoplasm periphery highly vascularized high metabolic activity accumulate subcutaneously brown adipose possess tons of mitochondria uses lipids to generate heat found in infants between shoulder blades review its digestion description matrix as in areolar but very sparse closely packed adipocytes have nucleus pushed to the side by large fat droplet function provides reserve food fuel insulates against heat loss supports and protects organs locations under skin around kidneys and eyeballs with abdomen and breasts Connective Tissue Proper Loose Connective Tissue Reticular closely resembles areolar only reticular fibers in its matrix description network of reticular fibers in a typical loose ground substance reticular cells lie on the network function fibers form a soft internal skeleton stroma that supports other cells types including white blood cells mast cells and macrophages location lymphoid organs Connective Tissue Proper Dense Connective Tissue Dense Regular collagen fibers dominate this tissue type all collagen fibers run in the same direction parallel to the tensile force fibroblasts finagled between collagen fibers fibroblasts continuously make collagen fiber rarely ground substance poorly vascularized forms tendons muscle to bone forms aponeuroses muscle to other muscle and bone forms fascia membrane around groups of muscles vessels and nerves forms ligaments connective fibers with greater elasticity bone to bone description primarily parallel collagen fibers a few elastin fibers major cell type is the fibroblast function attaches muscles to bones or to muscles attached bones to bones withstands great tensile stress when pulling force is applied in one direction location tendons most ligaments aponeuroses Connective Tissue Proper Dense Connective Tissue Dense Irregular same structural elements as dense regular connective tissue collagen fiber bundles thicker and arranged in all directions can withstand tensile forces coming from any direction exists in places where tensile forces attack from all sides Description primarily irregularly arranged collagen fibers some elastic fibers major cell type is the fibroblast function able to withstand tension exerted in many directions provides structural strength location dermis of skin submucosa of digestive tract fibrous capsules of organs and joints Cartilage can withstand both tension and compression very tough but flexible lacks innervation nervous system dispersed within it lacks vascularization receives nourishment by diffusion from blood vessels located in perichondrium connective tissue membrane that surrounds it ground substance with lots of GAC s attracts water collagen fibers viscous contains a tremendous amount of tissue fluid 80 H20 fluid enables tissue to recover quickly after compression chondroblasts are predominant cell type in maturing cartilage chondrocytes are the cells in mature cartilage that are packed together in cavities called lacunae Hyaline most abundant type of cartilage large amounts of collagen few chondrocytes in lacunae means its constantly growing also major component of epiphyseal plates regions of continued growth near ends of long bones description amorphous but firm matrix collagen fibers form an imperceptible network chondroblasts produce the matrix and when mature chondrocyte Heinlacunae function supports and reinforces has resilient cushioning properties resists compressive stress location forms most of the embryonic skeleton coves the ends of long bones in joint cavities forms costal cartilages of the ribs cartilages of the nose trachea and larynx Elastic histologically almost identical to hyaline cartilage more elastin fibers exists where a tremendous amount of elasticity needed external ear description similar to hyaline cartilage but more elastic fibers in matrix function maintains the shape of a structure while allowing great flexibility Fibrocartilage structurally intermediate between hyaline cartilage and dense connective ssue rows of chondrocytes in lacunae alternate with rows of collagen fiber resists both tension and compression very well description matrix similar to but less firm than that in hyaline cartilage thick collagen fibers predominate function tensile strength with the ability to absorb compressive shock location intervertebral discs pubic symphysis discs of knee joint Osseous Tissue support and protection of body structures ECM similar to cartilage but more collagen fibers ECM also infused with inorganic calcium salts osteoblasts are predominant cell type produce organic part of the matrix inorganic calcium salts deposited on and around collagen fibers Osteocytes like chondrocytes lie within depressions called lacunae Osteons composed of many concentric rings lamellae of bony material lamellae surround central canals that contain nerves and blood vessels description hard calcified matrix containing many collagen fibers osteocytes lie in lacunae very well vascularize function bone supports and protects by enclosing provides levers for the muscles to act on stores calcium and other minerals and fat marrow inside bones is the site for blood cell formation hematopoiesis Blood atypical connective tissuebut develops from mesenchyme and is surrounded by a matrix blood plasma primary cell types are erythrocytes RBC and WBC of various kinds fibers soluble under normal circumstances precipitate as clot when vessels are injured function transport of respiratory gases nutrients wastes and other substances Nervous Tissue primary tissue of the central and peripheral nervous systems brain spinal cord nerves cell type 1 neurons generate and transmit electrical impulse cell type 2 neuroglia assist in nervous impulse conduction and provide nourishment much more neuroglia than neurons neurons have projections dendrites receive stimuli axons send electrical impulses dont need much detail on the types of connective tissue M uscle composed of many cells and is very vascularized responsible for movement composed of myofilaments actin myosin filaments that operate in muscle contraction Skeletal Muscle Tissue voluntary under conscious control wrapped in connective tissue as large skeletal muscles contractile properties pull on bone to induce movement long cylindrical cells with many nuclei striated appearance due to alignment of myofilaments description long cylindrical multinucleate cells obvious striations function voluntary movement locomotion manipulation of the environment facial expression voluntary control location in skeletal muscles attached to bones or occasionally to skin Cardiac Muscle Tissue involuntary NOT under conscious control therefore you could take away the nerves and it would still continue beating Exists only in the wall of the heart Striated uninucleate branching pattern Cells connected by intercalated discs lntercalated discs promote coordinated cardiac muscle contraction description branching striated generally uninucleate cells that interdigitate at specialized junctions intercalated discs short cells Smooth Muscle Tissue Proper involuntary NOT under conscious control no striations single nucleus centrally located within cell exists in walls of hollow organs stomach contractions support movement of substances through passages description spindle like cells with central nuclei no striations cells arranged closely to form sheets function propels substances or objects Glandular Epithelium gland possesses one or more cells that secrete a product product is aqueous and contains proteins lipids or steroids secretion of product is active process obtain substances from blood to convert to product Endocrine gland internally secreting ductless lose ducts as they mature developmentally Produce hormones that are secreted by exocytosis into extracellular space Hormones taken up by blood distributed to target organ where they initiate cellular responses Most are multicellular some individual hormoneproducing cells exist in brain digestive tract Exocrine Gland externally secreting possess ducts Secrete products onto body surfaces or into body cavities Mucous sebaceous sweat salivary glands liver pancreas Most are multicellular but some are unicellular unicellular exocrine glands goblet cell produce a glycoprotein mucin that when dissolved in water makes a slippery substance called mucus multicellular exocrine glands consist of duct derived from epithelial tissue secretory unit acinus connective tissue supports secretory unit and provides blood and nervous input to gland connective tissue also forms fibrous capsules around the gland often dividing it into lobes Modes of Secretion merocrine secrete products via exocytosis pancreas sweat and salivary glands holocrine accumulate products until cells rupture sebaceous glands only Coverings and Linings continuous sheets composed of gt 1 tissue types epithelial connective tissue proper cutaneous membrane skin complex organ system dry membrane mucous membrane lines open body cavities wet membrane bathed by secretions contains either stratified squamous or simple columnar epithelial tissue epithelial tissues overlays layer of loose connective tissue lamina propria often the epithelial connective tissue overlays layer of smooth muscle tissue serous membrane wet membrane serous fluid bathes the membrane lines closed body cavities contrary to mucous membranes composed of simple squamous epithelium areolar connective tissue names of serous membranes vary with location in the body visceral connects to the organs while the parietal portion connects to the wall Tissue Repair requires cell division migration cells can migrate within your body look at developing embryo initiated by growth factors in injured area regeneration replacement of damaged tissue with same tissue type 1 Inflammation chemicals released by damaged cells macrophages and mast cells recruit clotting factors 2 Blood supply is resorted clot replaced by granulation tissue rich in capillaries fibroblasts proliferate contractile properties close wound macrophages digest clot and collagen fiber continues to be deposited 3 Surface epithelium starts regenerating under scab fibrous tissue becomes less prominent gt epithelium with underlying scar tissue body turns on itself and eats the scab fibrosis replacement of damaged tissue with fibrous connective tissue scars Developmental Considerations Chapter 6 Integumentary System Introduction integumentary system consists of the skin and its accessory organs hair nails and cutaneous glands inspection of the skin hair and nails is significant part of a a physical exam skin is the most vulnerable organ it is exposed to radiation trauma infection and injurious chemicals receives more medical treatment than any other organ system dermatology scientific study and medical treatment of the integumentary system FuncUon Protection against chemical physical and biological elements skin secretions melanin keratinization macrophages Langerhan s Cells Metabolic Function vitamin D synthesis critical for calcium metabolism Sensation sensory receptors Meissner s and Pacinian corpuscles Excretion sweat and sebaceous glands Body Temperature Regulation sweat glands evaporative cooling Nonverbal communication The lntegumentary System Epidermis outermost epithelial tissue nonvascularized Dermis fibrous connective tissue vascularized Hypodermis aka superficial fasciadeep to dermis superficial to fascia that covers muscle mostly adipose anchors skin to underlying structures but in a fluid wayNOT considered a layer of the skin Epidermis keratinized stratified squamous epithelium 5 Distinct Cell Types Stem Cells 1 undifferentiated ells that divide by mitosis 2 give rise to keratinocytes 3 only found in deepest epidermal layer stratum basale Keratinocytes Derive from stem cells 1 produce keratin a fibrous protein 2 tightly connected by desmosomes forces substances to be diffused THROUGH the cells instead of between 3 arise in deepest epidermal layer stratum basale undergo continuous mitosis cells push upward as made 4 as cells move superficially they lose connections with nourishing dermis and die most of our skin is dead Melanocytes 1 cells with spiderlike projections 2 produce melanin pigment synthesized from amino acids 3 only found in the deepest layer of epidermis stratum basale 4 melanin accumulates in melanosomes membranebound granules 1 line the upper edge of the cell and forms a shield for the cell from UV radiation 5 melanosomes shuttles to cell projections by actin filmanets taken up by keratinocytes gt pigment shield Tactile Merkel Cells 1 located at epidermisdermis junction 2 associated with disclike sensory nerve ending Merkel disc 3 Merkel Cell Merkel Disc sensory nerve ending gt touch receptor Langerhan s Cells aka Dendritic cells 1 arise in bone marrow migrate to epidermis 2 phagocytic engulfs foreign molecules 3 activate immune system 45 Distinct Layers Stratum basale 1 basal layer single lair of cells youngest keratinocytes 2 flPOOR highly active mitotically Stratum spinosum several layers thick cells contain intermediate filaments anchored to desmosomes keratinocytes appear irregular in shape scattered melanin granules Langerhan s cells most abundant here when dehydrated the desmosomes remain creating look like spiny backbones Stratum granulosum 4 5 thin but 35 cell layers keratinocyte appearance changes to flat cells without nuclei or organelles keratinohyaline granules form keratin in upper layers lamellated granules release glycolipids into extracellular space for waterproofing plasma membranes thicken protection above this layer nourishment from dermis capillaries is not possible Stratum lucidum 1 2 clear banOUd above the stratum granulosum a few rows of dead keratinocytes flat and clear thick skin only Stratum corneum 1 2 3 Dermis thickest layer contains 2030 cell layers keratin and highly thickened cell membranes provide maximum protection against abrasion glycolipid as waterproofing Connective tissue proper strong flexible fibroblasts macrophages WBC extensive fibers richly innervated and vascularized home for hair follicles and sebaceous glands Papillary Layer areolar connective rissue collagen elastin fibers significant vascularization superior surface dermal papillae house sub capillary plexus free nerve endings pain Meissner s corpuscles touch on palms and soles inferior papilla located atop dermal ridges gt epidermal ndges increase gripping ability house pores of sweat glands fingerprints Reficular Layer dense irregular connective tissue makes up 80 of dermis thickness deep to reticular layer cutaneous plexus provides nourishment Pacinian corpuscle pain and pressure sensation Skin Color Melanin most significant factor in skin color produced by melanocytes accumulate in the keratinocytes of stratum basale and stratum spinosum eumelanin brownish black therefore absorbs sunlight pheomelanin a reddish yellow sulfurcontaining pigment we all have the same number of melanocytes DarkSkinned Individuals melanocytes are more actives melanin granules in keratinocytes more spread out than tightly clumped melanin breaks down more slowly melanized cells seen throughout the epidermis LightSkinned Individuals melanin clumped near keratinocyte nucleus clumps of melanin freckles melanin breaks down more rapidly little seen beyond stratum basale Cyanosis blueness of the skin from deficiency of oxygen i the circulating blood airway obstruction drowning or choking lung diseases emphysema or respiratory arrest cold weather body using a lot of oxygen to maintain warmth and the blood moves slowly in colder weather or cardiac arrest Erythema abnormal redness of the skin due to dilated cutaneous vessels exercise hot weather sunburn 5 anger or embarrassment Pallor pale or ashen color when there is so little blood flow through the skin that the white color of dermal collagen is visible emotional stress low blood pressure circulatory shock cold anemia Albinism genetic lack of melanin that results in white hair pale skin and pink eyes have inherited recessive nonfunctional tyrosinase allele Jaundice yellowing of skin and sclera due to excess of bilirubin in blood cancer hepatitis cirrhosis and other compromised liver function Hematoma bruise mass of clotted blood showing through skin Evolution of Skin Color one of the most conspicuous signs of human variation results from combination of evolutionary selection pressures especially differences in exposure to UV radiation UV Radiation 1 causes skin cancer 2 breaks down folic acid needed for normal cell division fertility and fetal development 3 stimulates synthesis of vitamin D necessary for dietary calcium absorption 4 females need to produce more folic acid and are thus typically lighter skinned than males populations native to the tropics and their descendants tend to have well melajized skin to screen out excessive UVR populations native to far northern or southern latitudes where the sunlight is weak tend to have light skin to allow for adequate UVR populations at higher altitudes typically have darker skin because the thinner dryer air filters out less UV rays ancestral skin color is a compromise between vitamin D and folic acid requirements 1 darker skin better UVR protection but less Vitamin D 2 lighter skin lower UVR protection but more Vitamin D women have skin averaging about 4 lighter than men 1 need greater amounts of vitamin D and folic acid to support pregnancy and lactation UVR accounts for up to 77 of variation in human skin color Three Pigments of Skin Color melanin 1 only made in skin produced by melanocytes in stratum basale 2 all humans have essentially same of melanocytes but differentially express genes that code for melanin s composite proteins 3 freckles local accumulations of melanin 4 melanocytes are stimulated by sunlight to produce melanin tanwhy Because of the longer exposure to UVR your body realizes it needs to protect itself more from UVR carotene 1 found in plant products 2 accumulates in stratum corneum and hypodermis 3 carot carrot Hemoglobin 1 red color from oxygenated hemoglobin passing through capillary beds in stannous or subcapillary plexus 2 too much methemoglobin doesn t bind oxygen why Hair and Hair Follicles main function of hair sensation also protects against environment sunlight hair pili flexible strands of dead keratinized cells produced by hair follicle 1 keratin of hair is tougher than that of skin we don t have more hair that each other or chimpanzees we just have varying hair thicknesscoarseness and degrees of darkness Anatomy of Hair 1 shaft portion that projects from skin 2 root embedded in skin 3 Three concentric layers of keratinized cells 1 core medulla large cells air spaces 2 cortex several layers of flat cells surrounding medulla 3 cuticle single overlapping cell layers lots of keratin 4 melanocytes generate hair pigment at follicle base and pigment is transferred to cortex 5 follicles are ingrowths of epidermal surface into the dermis 1 composed of connective tissue root sheath dermisderived and outermost glassy membrane thickened basement membrane and epithelial root sheath epidermaldervied and innermost 6 hair bulb expansion at deep end of follicle 7 hair follicle receptor detects hair movement and transmits information to the brain 8 hair papilla contains capillaries supplies nutrients to hair and signals growth 9 cells of hair matrix actively divide older cells get pushed up 10 arrector pili smooth muscle controls hair erection goosebumps involuntary Hair Texture 1 straight hair is round 2 wavy hair is oval 3 curly hair is relatively flat Hair Color 1 brown and black hair is rich in eumelanin 2 red hair has a slight amount of eumelanin but a high concentration of pheomelanin 3 blond hair has an intermediate amount of pheomelanin and very little eumelanin 4 gray and white hair results from scarcity of absence of melanin in the cortex and the presence of air in the medulla Skin Appendages Sudoriferous sweat glands 1 lacking sweat glands nipples parts of external genitalia 2 exocrine widely distributed 3 Eccrine merocrine 1 flPOOR most numerous of the sweat gland types abundant on plasm soles forehead coiled tubular gland secretory apparatus in dermis duct extends to skin surface 4 Sweat DUIPOOR blood filtrate secreted by sweat gland cells into duct by exocytosis 99 water with salts antibodies metabolic wastes urea ammonia dermicidin natural bacterial killer rather acidic pH between 46 Function combat overheating heatinduced sweat forehead emotional sweat palms soles armpits Apocrine dont perform apocrine function named such because they have a large lumen far less numerous 2 secrete into a duct which empty into hair follicles 3 axillary and anogenital region 4 larger than eccrine 5 true sweat fats proteins yellow viscous 6 odorless but theorized that it is a pheromone increased secretion during sexual activity increased secretion during menstrual cycle 7 begin functioning at puberty androgen influenced 8 a closet scent gland 9 Modification on a theme 1 ceruminous glands in external ear canal secrete wax cerumin insect repellent 2 mammary gland specialized sweat glands that secrete milk 8 Sebaceous Glands L simple branched alveolar glands 2 located everywhere except palms and soles OD secrete sebum in a holocrine fashion central cells accumulate lipid unit they burst sebum secreted into hair follicle softens and lubricates hair and skin curbs water loss from skin bactericidal ICDU lh stimulated by sex hormones especially at puberty 1 sebaceous gland ducts become blocked by accumulated sebum whitehead 2 accumulated sebum oxidizes and dries blackhead 3 inflammation of sebaceous gland often caused by Staphylococcus infection acne Burn Tissue damage inflicted by severe heat radioactivity chemicals protein denaturation and cell death specifically keratin loss of body fluids containing electrolytes lead to osmotic shock first degree epidermis second degrees epidermis upper dermis third degree full thickness of skin 1 dont actually feel because you have burned all of your sensory nerves what you feel is the pain from the second and first degree burns around it fourth degree bones burned fluid loss estimated by of body burned 1 Rule of Nines 11 areas accounting for 9 of body area 1 anterior 45and posterior 45 head and neck 9 anterior 9 and posterior 9 upper limbs 18 anterior 18 and posterior 18 trunk 36 00 perineum of genitalia 1 anterior and posterior of lower limbs anterior of one limb936 Chapter 7 Skeletal System Skeletal Cartilage compression resistance surrounded by perichondrium perichondrium prevents expansion in compressed cartilage contains vessels nourishment Hyaline articular costal respiratory nasal Elastic ear epiglottis Fibrocartilage vertebral discs knee meniscus highly compressible high tensile strength appositional growth cells of perichondrium secrete ECM against existing cartilage growth from outside interstitial growth chondrocytes in lacunae divide and secrete ECM growth from Within Bone support bears weight cradles soft organs protection skull bones brain vertebrae spinal cord rib cage thoracic organs movement long bones muscle attachments level systems association with joints storage calcium and phosphate bank insulinlike growth factor hematopoiesis bloodcell formation in marrow cavities Bone Classification long bone longer than wide shaft 2 ends femur humerus carpals tarsals named for shape not size Short bone cubeshaped wrists ankles sesamoid formed in tendons flat bone thin flat curved sternum scapula ribs skull irregular bone various complicated shapes vertebra General Bone Structure osseous nervous cartialge fibrous connective muscle epithelial in vessels compact bone smooth and solid to the naked eye more dense than spongy bone spongy cancellous bone internal to compact bone irregular spaces with trabecular filled with red or yellow marrow 4 Main Cell Types all located within ECM that they generate osteogenic cells 1 osteogenic cells are highly mitotically active stem cells 2 found in periosteum and endosteum 3 differentiate into osteoblasts or remain as bone stem cells osteoblasts produce collagen fibers that spiral the length of the osteon osteoclasts 1 dissolve bone by producing HCI osteocytes occupy lacunae at lamellae junctions maintain bone matrix signal for bone repair Long Bone Structure diaphysis shaft long axis of bone compact bone collar surrounds central medullary marrow cavity which contains mainly fatty yellow bone marrow epiphysis bone ends more expanded in shape compact bone collar surrounds spongy with trabecular red marrow often infiltrates trabecular hematopoiesis joint interface contains articular hyaline cartilage cushion resist stress epiphyseal line between diaphysis and epiphysis remnant of epiphyseal plate disk of hyaline cartilage that participates in bone growth during young adulthood periosteum covers the outer surface of bone outer fibrous layer of dense irregular connective tissue inner osteogenic with osteoblasts and osteoclasts richly innervated and vascularized nerves and blood vessels enter diaphysis via nutrient foramen secured to bone by perforating Sharpey s fibers forms a continuum of tendons and ligaments and provides an anchoring point for them endosteum covers internal bone surfaces canals trabecular etc contains osteoblasts and osteoclasts Short Irregular and Flat Bone Structure preiosteum covers compact bone endosteum covers spongy bone no shaft or epiphysis contains bone marrow but no marrow cavity spongy bone called diplo Hematopoietic Tissue red marrow trabecular cavity of spongy bone of long bones or diploe of flat bones red blood cell production in femur and humerus limited to epiphyses with spongy bone red blood cell formation highly active in diplo of flat bones sternum and irregular bones hip Compact Bone structural unit osteon elongated cylinder parallel ot long axis osteon groups of hollow tubes of bone matrix each component tube lamella collagen fibers in adjacent lamellae run in opposite directions resist torsion much like Russian nesting dolls Central Haversian Canals contains blood vessels and nerve fibers surrounded by osteons Volksmann s perforating Canals perpendicular to long axis connects blood supply of periosteum to Haversian canal and medullary cavity osteocytes canaliculi canals connecting lacunae holes where cells are found to each other and to central canal distribute nourishment throughout bone Lamellae lnterstitial located between intact osteons fill gaps between osteons circumferential deep to periosteum superficial to endosteum circumference of diaphysis Spongy Bone trabeculae align along regions of high stress contain irregularly arranged lamellae and osteocytes connected by canaliculi no osteons Chemical Composition of Bone 33 organic cells and osteoid ground substance collagen 65 inorganic mineral salts calcium phosphates infiltrate and surround collagen account for hardness lntramembranous Ossification Bone develops from fibrous membrane of embryonic skeleton condensation of mesenchyme into soft sheet permeated with blood capillaries Endochondral Ossification KNOW THE DIFFERENCE BETWEEN ENDOCHONDRAL AND INTRAMEMBRANOUS cartilage mold formation of primary ossification center bony collar and periosteum vascular invasion formation of primary marrow cavity and appearance of secondary ossification one at birth with enlarged primary marrow cavity and appearance of secondary marrow cavity in one epiphysis bone of child with epiphyseal plate at distal end occurs during infancy and childhood the epiphyses fill with spongy bone cartilage limited to the articular cartilage covering each joint surface and to the epiphyseal plate a thin wall of cartilage separating the primary and secondary marrow cavities epiphyseal plate persists through childhood and adolescence serves as a growth zone for bone elongation by late teens to early 20s all remaining cartilage in the epiphyseal plate is generally consumed gap between epiphyses and diaphysis closes primary and secondary marrow cavities unite into a single cavity bone can no longer grow in length Bone Growth and Remodeling ossification continues throughout life with the growth and remodeling of bone can grow lengthwise and widthwise Bone Elongation epiphyseal plate a region of transition from cartilage to bone functions as growth zone where the bones elongate consists of typical hyaline cartilage in the middle with a transition zone on each side where cartilage is being replaced by bone metaphysis is the zone of transition facing the marrow cavity 1 Zones of Metaphysis 1 Zone 1reserve cartilage typical histology of resting hyaline cartilage 2 Zone 2 cell proliferation chondrocytes multiplying and lining up in rows of small flattened lacunae 3 Zone 3 cell hypertrophy cessation of mitosis enlargement of chondrocytes and thinning of lacuna walls 4 Zone 4 calcification temporary calcification of cartilage matrix between columns of lacunae 5 Zone 5 bone deposition breakdown of lacuna walls leaving open channels death of chondrocytes bone deposition by osteoblasts forming trabeculae of spongy bone Bone Structure Reflects Mechanical Stress Wolff s Law bone growth or remodeling in response to demands placed on it bone tickets midway along diaphysis bending stress is highest curved bones thickest at buckling point trabeculae form along compression lines large projections at muscle attachments Physiology of Osseous Tissue a mature bone remains a metabolically active organ involved in its own maintenance of growth and remodeling exerts a profound influence over the rest of the body by exchanging minerals with tissue fluid 1 disturbance of calcium homeostasis in skeleton disrupts function of other organ systems 1 especially nervous and muscular Mineral Deposition and Resorption 1 mineral deposition mineralization crystallization process in which calcium phosphate and other ions are taken from the blood plasma and deposited in bone tissue 1 fibers become encrusted with minerals that harden the matrix 1 calcium and phosphate hydroxyapatite from blood plasma are deposited along fibers 2 calcium and phosphate ion concetration must reach a critical value called the solubility product for crystal formation to occur 3 most tissues have inhibitors to prevent this so they do not become calcified 4 osteoblasts neutralize these inhibitors and allow salts to precipitate in the bone matrix 5 first few crystals seed crystals attract more calcium and phosphate from solution 6 abnormal calcification ectopic ossification 1 may occur in lungs brain eyes muscles tendons or arteries arteriosclerosis 2 calculus calcified mass in an otherwise soft organ such as the lung 7 mineral resorption the process of dissolving bone and releasing 4 5 1 1 7 minerals in to the blood performed by osteoclasts at the ruffled border hydrogen pumps in membranes secrete hydrogen into space between the osteoclast and bone surface chloride ions follw by electrical attraction hydrochloric acid pH 4 dissolves bone materials acid phosphatase enzyme digests the collagen ex orthodontic appliances tooth moves because osteoclasts dissolve ahead of the tooth where the pressure on the bone is the greatest osteoblast deposit bone more slowly in the lowpressure zone behind the tooth calcium homeostasis calcium and phosphate are used for much more than bone structure phosphate is a component of DNA RNA ATP phospholipids and pH buffers calcium needed in neuron communication muscle contraction blood clotting and exocytosis minerals are deposited in the skeleton and withdrawn when they are needed for other purposes depends on a balance between dietary intake urinary and fecal losses and exchanges between osseous tissue hypocalcemia calcium deficiency 1 excessive nerve excitability tetany hypercalcemia calcium excess 1 less nerve excitability muscle weakness sluggish reflexes 8 calcium homeostasis is regulated by three hormones 1 calcitriol calcitonin and parathyroid hormone 9 Calcitriol 1 a form of vitamin D produced by the sequential action of the skin liver and kidneys most active form of Vitamin D also from fortified milk 2 produced by the following process 1 epidermal keratinocytes use UV radiation to convert a steroid 7dehydrocholesterol to previtamin D3 2 liver adds a hydroxyl group converting it to calcidiol 3 kidneys add another hydroxyl groups converting that to calcitriol 3 behaves as a hormone that raises blood calcium concentration 1 increases calcium absorption by small intestine 2 increases calcium reabsorption from the skeleton 3 promotes kidney reabsorption of calcium ions so less is lost in urine 4 necessary for bone deposition need adequate calcium and phosphate 5 abnormal softness of bones in children rickets and in adults osteomalacia whiteout adequate Vitamin D 10 Calcitonin 1 secreted by C cells clear cells of the thyroid gland when calcium concentration raises too high 2 lowers blood calcium concentration in two ways 1 osteoclast inhibition reduces osteoclast activity as much as 70 less calcium liberated from bones 2 osteoblast stimulation increases the number and activity of osteoblasts deposits calcium into the skeleton 3 important in child weak effect in adults 1 osteoclasts more active in children due to faster remodeling 2 deficiency does not cause disease in adults 3 reduces bone loss in women during pregnancy and lactation 11 Parathyroid Hormone PTH 1 secreted by the parathyroid glands which adhere to the posterior surface of the thyroid gland 2 PTH released when there is low blood calcium levels 3 PTH raises calcium blood level by four mechanisms 1 binds to receptors on osteoblasts 1 stimulating them to secrete RANKL which raises the osteoclast population 2 promotes calcium reabsorption by the kidneys less lost in urine 3 promotes the final step of calcitriol synthesis in the kidneys enhancing calciumraising effect of calcitriol 4 inhibits collagen synthesis by osteoblasts inhibiting bone deposition 2 sporadic injection or secretion of low levels of PTH causes bone devotion and can increase bone mass 3 know which one raises and which one lowers and how they do that Fractures know different types of fractures nondisplaced displaced complete incomplete Hnear transverse compound simple Bone Repair hematoma formation blood vessels fo bone and periosteum hemorrhage mass of clotted blood fibrocartilaginous callous formation granulation tissue capillaries grow into hematoma phagocytic cells clean up debris bone shards fibroblasts osteoblasts enter fracture site to begin bone reconstruction 1 collagen fibers span the break connecting bone ends 2 fibroblasts differentiate into chondroblasts that secrete cartilage matrix 3 osteoblasts begin forming spongy bone Know difference between axial and appendicular skeleton 206 bones
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