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Microanatomy Characteristics, Unit 2 Warning: Not all of the structures we need to know are listed here! Cartilage: Hyaline cartilage: avascular, clear amorphous ground substance Elastic cartilage: lg round cells, avascular, matrix filled with black staining fibers(3 types)-elastic (Y branching, straight), reticular (right angle branching, squiggly), collagen(straight unbranched bundles), dots are cross sectional view of fibers, without stain would look like hyaline cartilage Fibrocartilage: Primary fiber type=Collagen type I, lrg round cell, not as much grd substance as hyaline cartilage Bone: Osteoclasts: large multinucleated, can sometimes see Howships’ lacunae Indications of Endochondral Ossification: hypertrophy of cartilage cells, periosteal collar Indications of internal remodeling: Interstitial lamellae=osteocytes running through, arching over, but no central canal, remnants of osteons, is it living or not? Don’t know, may still be connection to bv somewhere for nutrients? Resorption tunnel=hole created by osteoclasts, no concentric rings ard it Closing cone=large hole, bigger than central canal, couple layers only, forming osteon Zone of prolif: stacks of coins, process occurring is interstitial growth of cartilage (to be replaced with bone) Isogenous grp: more than one cell in each lacuna, indicates growth Intervertebral Disc: Spongy and compact bone, in between=intervertebral disc, nucleus pulposis is gelatinous , type of joint=symphysis, cartalaginous, amphiarthroses (slightly moveable) Volkmann’s canal:supplies nutrients to BVs of osteons, diagonal canal with BV, no concentric rings ard it Canaliculi (tunnels): spidery fibers, don’t extend past cement line, inside them are the cellular processes Muscle: Smooth muscle: Irregularly shaped fibers, round cross-sectional profiles, nucleus is cigar shaped and very peripherally located-on inside edge of cross-sectional profile, other dark spots visible are the nuclei of CT, difficult to see cell borders, contorted/corkscrew config of nuclei=contracted, smooth muscle can be partially contracted so some nuclei can be seen in contracted position, others in relaxed Skeletal Muscle: striated voluntary muscle, nuclei also peripherally located, can see striations, I bands – light stained, A Bands – dark stained, Sarcomere=middle of one I band to the middle of the next I band, myoglobin staining: dark stained(red) have high myoglobin content, low glycogen conent, large white fibers have low myoglobin and high glycogen content, EM Level: T tubules seen at junction of A and I bands, H bands=thick filaments only, held apart by crossbridging proteins (M line) Cardiac: Striated appearance, short, branched fibers, centrally located nucleus, intercalated discs visible on some longitudinal slides-can see dark thin lines(transverse portion, can’t see lateral portion, just know it’s btw two transverse), endomysial like CT partially surrounds myocytes-not completely like skeletal Tendon: (CT, how to tell diff from skeletal muscle) tightly packed collagen bundles are wavy in longitudinal section and lack cross striations, elongated nuclei squeezed between the bundles are characteristic, in cross section, the stellate shaped nuclei appear to be scattered throughout the bundles and not just located at the periphery of the bundles, many more nuclei per specific area in tendon Nervous: Nerve fibers: black, fibers entering muscle---supplying electrical signals for the command structure; voluntary command starts in cerebral cortex, travels through ventral horn, Nissl bodies visible in slides stained for ribosomes (the dendrites will be unstained bc they don’t have a lot of ribosomes), dendrites are thick and taper off, thin axon not always visible(has constant diameter), white space is myelin coating-not continuous sheet-Nodes of Ranvier are seen as lines that break it up, myelin makes up most of cell in cross section, Dark brown lipophilic staining slide: dark stained circles-myelin, white inside is the axon pointing out at you Dendritic spines – beaded appearance; increase surface area of receiving info Motor end plate: specialization of the nerve fiber, tip of nerve fiber embeds itself in membrane of muscle, forms neuormuscular synapse; speckled appearance (specializations of junctional folds), number of motor endplates and number of muscle cells determine the precision, each muscle fiber is innervated by a single motor end plate, but a given motor axon can innervate many muscle fibers. Muscle Spindle: designed to detect stretch of muscle; made up of intrafusal fibers; surrounded by CT fibers, relays info to CNS, identified by a spring-like axon wrapped around fibers-will see the speckles not the actual axons, made up nuclear bag fibers (group of nuclei), nuclear chain fibers. In cross section-connective tissue capsule surrounding cross sections of one to five small intrafusal fibers, can see one nucleus of the nuclear chain fibers. Glial cell cytoplasm not a lot of stain-little nuclei, many more of them, primarily support function, some may be oligodendrctyes-provide myelin coating to a portion of an axon (internodal segment)