BIOL 252 1st Edition Lecture 9 Outline of Last Lecture I The Skin Its Structure and Function II The Epidermis III The Dermis IV Hypodermis V Skin Coloration Outline of Current Lecture I The Skin Its Structure and Function Current Lecture I II III Skeleton Function a Protection b Support c Movement d Electrolyte balance i Calcium levels kept stable NT release e Blood formation Histology of Osseous Tissue a Osteogenic cell i Multipotential stem cell b Osteoblast i Blast in a developmental stage ii Complete process of differentiation and become osteocyte c Osteocyte i Live completely surrounded by the matrix they have produced ii Lacunae packet w in bone matrix where osteocytes live iii Interconnect themselves w dendrites arms in canaliculi channels iv Gap junctions allow diffusion and passing along of nutrients d Osteoclasts i Breakdown bone matrix The Matrix a Made of fibers and ground substance b Fibers are proteins c Ground substance is the fluid component of extracellular matrix i Interstitial These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute IV d In bone i Fibers are collagen tough resists stretching ii Ground substance fluid is essentially gone 1 Minerals precipitated out of solution 2 Most is calcium hydroxyapatite calcium phosphate salt 80 of inorganic matrix e Bone in vinegar i Vinegar acetic acid ii Acetic acid calcium phosphate solubilizes the salt iii Illustrates that if you extract mineral component of bone properties of the bone remain same 1 Flexibility comes from collagen 2 Stiffness comes from hydroxyapatite 3 Just removing stiffness f Case 5 year old girl is brought to clinic and legs bend under weight i What could explain this condition at tissue level and what might be cause of tissue abnormality 1 Caused by a Dietary deficiency of calcium b Vitamin D deficiency g Bone Matrix Pathologies i Osteogenesis imperfecta excessively brittle bones resulting form improperly formed collagen Long Bone Structure a Epiphysis diaphysis shaft epiphysis b Epiphyseal line once were epiphyseal plates site of bone growth c Spongy bone has pockets made of bone matrix i Spaces are not lacunae ii At the ends of bone d Compact bone dense heavier than spongy bone i All around edges e Nutrient foramen i Provide vascular and nervous supply f Bone marrow i As adults most is classified as yellow ii Yellow bone marrow made primarily of adipose tissue most of bone marrow throughout body iii Red bone marrow found in more select region of bones 1 Axial skeleton 2 And more proximal parts of long bones 3 Can replace yellow bone marrow g Periosteum i Connective tissue wraps around outside of bone V VI VII VIII ii If need to tear down bone matrix use osteoclast iii If need to build bone matrix use osteoblast h Endosteum i Periosteum on the inside ii Wherever you have bone marrow coming in contact w bone surface have endosteum iii Bone is never in contact w marrow iv Osteoclast and osteoblast present i Articular cartilage i Where bone articulates w another bone Structure of Flat Bone a No cartilaginous joints have sutures b Thickness of bone is like a sandwich c On outside and inside outer inner compact bone d Middle filling spongy bone i In the spaces of spongy bone bone marrow ii Trabeculae connecting roads that make up solid part of bone iii Why do we need spongy bone 1 Lighter 2 Flexibility Histology of Compact Bone a Osteon i Circular arrangement around blood vessel ii Unit of bone iii Haversion system iv Collagen oriented in different directions v Provide strength in resisting compression b Layers lamella Histology of Spongy Bone a Bone matrix are arranged in two trabeculae beams b Spongy bone contains slivers spicules and beams trabeculae of bone providing strength w minimal weight c Trabeculae align along lines of stress through the process of remodeling i Change orientation over time until they are best aligned w stresses placed on your bones Bone Formation a 2 processes b Intramembranous ossification direct w in membranes flat bones of the skull i Undifferentiated cells turn to osteoblasts create bone matrix w in confines of some membrane ii Most common in the skull iii Bone production in flat bones occurs directly through osteoblast activity in thin membranes mostly surrounding the brain c Endochondral ossification indirect replacing cartilage w bone i Cartilage model breakdown and replace w bone ii Below the neck head iii STEPS 1 Early cartilage model a Temporary structure b Around cartilage perichondrium c Cartilage hyaline cartilage 2 Formation of primary ossification center bony collar periosteum a Become very big enlarge b After they enlarge will die and leave behind open space c Bony collar forming around diaphysis 3 Vascular invasion formation of primary marrow cavity and appearance of secondary ossification center a Cells die b Vascular invasion blood vessels come in and take some periosteum w them 4 Bone at birth w enlarged primary marrow cavity and appearance of secondary marrow cavity in one epiphysis a Build walls on inside of cavity b Secondary ossification centers begin same process i Vascular invasion ii Formation of cavity iii Filled w bone c Replacing tissue not converting it 5 Bone of child w epiphyseal plate at distal end a Leave epiphyseal plate as cartilage for a while temporary b Also leave cartilage at articular cartilage permanent 6 When does this all happen a Done by the time you are born iv Radiolucent cartilage appears dark in radiographs 1 Dark lines still growing d Bone growth of epiphyseal plates i Cells proliferating in the middle ii Bone is being added from diaphysis and epiphysis iii Increase length of bones at the plates through cell division of cartilage iv Increasing in thickness degrading it on the edges and turning it into bone
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