BIOL 252 1st Edition Lecture 9 Outline of Last Lecture I. The Skin: Its Structure and FunctionII. The EpidermisIII. The DermisIV. HypodermisV. Skin ColorationOutline of Current LectureI. The Skin: Its Structure and FunctionCurrent LectureI. Skeleton Functiona. Protectionb. Supportc. Movementd. Electrolyte balancei. Calcium levels kept stable (NT release)e. Blood formationII. Histology of Osseous Tissuea. Osteogenic celli. Multipotential stem cellb. Osteoblast:i. Blast = in a developmental stageii. Complete process of differentiation and become osteocytec. Osteocytei. Live completely surrounded by the matrix they have producedii. Lacunae: packet w/in bone matrix where osteocytes liveiii. Interconnect themselves w/ dendrites/arms in canaliculi (channels)iv. Gap junctions allow diffusion and passing along of nutrientsd. Osteoclastsi. Breakdown bone matrix III. The Matrixa. Made of fibers and ground substanceb. Fibers are proteins c. Ground substance is the fluid component of extracellular matrixi. 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.d. In bonei. Fibers are collagen (tough, resists stretching)ii. Ground substance – fluid is essentially gone1. Minerals precipitated out of solution2. Most is calcium (hydroxyapatite – calcium phosphate salt = 80% ofinorganic matrix) e. Bone in vinegari. Vinegar = acetic acidii. Acetic acid + calcium phosphate solubilizes the saltiii. Illustrates that if you extract mineral component of bone, properties of the bone remain same1. Flexibility comes from collagen2. Stiffness comes from hydroxyapatite3. Just removing stiffness f. Case: 5 year old girl is brought to clinic and legs bend under weighti. What could explain this condition at tissue level and what might be cause of tissue abnormality?1. Caused by:a. Dietary deficiency of calciumb. Vitamin D deficiencyg. Bone Matrix Pathologiesi. Osteogenesis imperfecta: excessively brittle bones resulting form improperly formed collagenIV. Long Bone Structurea. Epiphysis, diaphysis (shaft), epiphysisb. Epiphyseal line: once were epiphyseal plates – site of bone growth c. Spongy bone: has pockets, made of bone matrixi. Spaces are not lacunaeii. At the ends of boned. Compact bone: dense, heavier than spongy bonei. All around edgese. Nutrient forameni. Provide vascular and nervous supplyf. Bone marrowi. As adults, most is classified as yellowii. Yellow bone marrow: made primarily of adipose tissue (most of bone marrow throughout body)iii. Red bone marrow: found in more select region of bones1. Axial skeleton2. And more proximal parts of long bones3. Can replace yellow bone marrowg. Periosteumi. Connective tissue wraps around outside of boneii. If need to tear down bone matrix-use osteoclastiii. If need to build bone matrix-use osteoblasth. Endosteumi. Periosteum on the insideii. Wherever you have bone marrow coming in contact w/ bone surface, have endosteumiii. Bone is never in contact w/ marrowiv. Osteoclast and osteoblast presenti. Articular cartilagei. Where bone articulates w/ another boneV. Structure of Flat Bonea. No cartilaginous joints, have sutures b. Thickness of bone is like a sandwichc. On outside and inside = outer/inner compact boned. Middle/filling = spongy bonei. In the spaces of spongy bone = bone marrowii. Trabeculae: connecting roads that make up solid part of boneiii. Why do we need spongy bone?1. Lighter2. FlexibilityVI. Histology of Compact Bonea. Osteoni. Circular arrangement around blood vesselii. Unit of boneiii. Haversion systemiv. Collagen oriented in different directionsv. Provide strength in resisting compressionb. Layers = lamellaVII. Histology of Spongy Bonea. Bone matrix are arranged in two trabeculae (beams)b. Spongy bone contains slivers (spicules) and beams (trabeculae) of bone providingstrength w/ minimal weightc. Trabeculae align along lines of stress through the process of remodelingi. Change orientation over time until they are best aligned w/ stresses placed on your bonesVIII. Bone Formationa. 2 processesb. 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 membraneii. Most common in the skulliii. Bone production in flat bones occurs directly, through osteoblast activity in thin membranes (mostly) surrounding the brainc. Endochondral ossification: indirect, replacing cartilage w/ bonei. Cartilage model, breakdown and replace w/ boneii. Below the neck/headiii. STEPS:1. Early cartilage modela. Temporary structureb. Around cartilage = perichondriumc. Cartilage = hyaline cartilage2. Formation of primary ossification center, bony collar, periosteuma. Become very big (enlarge)b. After they enlarge, will die and leave behind open spacec. Bony collar forming around diaphysis 3. Vascular invasion, formation of primary marrow cavity, and appearance of secondary ossification centera. Cells dieb. Vascular invasion: blood vessels come in and take some periosteum w/ them4. Bone at birth, w/ enlarged primary marrow cavity and appearanceof secondary marrow cavity in one epiphysisa. Build walls on inside of cavityb. Secondary ossification centers begin same processi. Vascular invasionii. Formation of cavityiii. Filled w/ bonec. Replacing tissue – not converting it5. Bone of child w/ epiphyseal plate at distal enda. 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 borniv. Radiolucent cartilage appears dark in radiographs1. Dark lines = still growingd. Bone growth of epiphyseal platesi. Cells proliferating in the middleii. Bone is being added from diaphysis and epiphysisiii. Increase length of bones at the plates through cell division of cartilageiv. Increasing in thickness, degrading it on the edges and turning it into