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Skeletal System

Skeletal System. Mrs. Rago BCTHS Anatomy & Physiology. Functions of Skeletal System . Support & stabilize Protect vital organs Assists in movement Makes blood cells Hematopoiesis Storage area. Associated Tissues. Cartilage Connective tissue Framework for bones in fetus Ligaments

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Skeletal System

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  1. Skeletal System Mrs. Rago BCTHS Anatomy & Physiology

  2. Functions of Skeletal System • Support & stabilize • Protect vital organs • Assists in movement • Makes blood cells • Hematopoiesis • Storage area

  3. Associated Tissues • Cartilage • Connective tissue • Framework for bones in fetus • Ligaments • Tough connective tissue • Attachment point for other bones • Tendons • Attach muscle to bone

  4. cartilage ligaments Tendons

  5. Bone Structure • Long Bones • Long & thinner but with expanded ends • Ex: forearm & thigh bones • Short Bones • Cubelike: length & width roughly equal • Ex: wrists & ankles • Flat Bones • Platelike • Ex: ribs, scapulae, & some of skull bones • Irregular Bones • Variety of shapes & are usually connected to several other bones

  6. Long bone- femur Irregular bone- patella Flat bone- scapula Short bones- wrist

  7. Parts of Long Bone • Epiphysis • Articulates with another bone (joint) • Covered with articular cartilage • Layer of hyaline cartilage • Diaphysis • Shaft of bone

  8. Theory behind long bones • Long bones are very useful in lifting heavy loads • Act as a lever when lifting a weight force Resistance First-class lever fulcrom

  9. Resistance Second-class Lever Fulcrom Force Resistance Force Third-class Lever Fulcrom

  10. Lever • Has 4 basic components • Rigid bar • Pivot or fulcrum (what the bar turns on) • Object that is moved against resistance • Force that supplies energy for the movement of the bar • Only first-class & second-class lever movements are found in the human body

  11. Development of Bone • Periosteum • Fibrovascular membrane that covers a bone • Endosteum • Line the medullary cavity • Medullary Cavity • Center of bone • Contains bone marrow

  12. periosteum endosteum Medullary Canal

  13. More bone Development • Osteoblasts • Precursors to osteocytes • Bone forming cells which deposit bony matrix around themselves • Deposit bone in the endosteum (area of cells that line the medullary cavity) • Osteocytes • Bone cells • Located in tiny chambers called lacunae

  14. Bone Development Again • Osteoclasts • Responsible for reabsorption of bone • Remove bone and replace it during remodeling • Occurs especially when repairing a broken bone • Also occurs when bone is reshaped (bow-legs) • Osteocytes deposit new bone

  15. Bone Marrow • Red bone marrow • Fills spaces within cancellous bone • Well supplied with blood • Produces blood cells = hematopoiesis • White & red blood cells • Found in adults, but only in select bones • Ribs, vertebrae, sternum, and pelvic bones • Found in humerus & femur but decreases with age

  16. Bone Marrow • Yellow Marrow • Connective tissue that consists largely of fat cells • Found predominantly in shafts of long bones in medullary cavity • Can become red marrow in times of need (major loss of blood) and produce blood cells if necessary

  17. Types of Ossification • Intramembraneous Ossification • Dense connective tissue membranes are replaced by deposits of inorganic calcium • Only bones of skull • Does not occur until a few months after birth • Soft spot = fontanelle

  18. Types of Ossification • Endochondral Ossification • Cartilage is formed first and then replaced by mature bone cells • Primary ossification center • Found in center of a long bone • Bone develops from 1̊ ossification center toward the ends of cartilaginous structure • Secondary ossification center • Appear later than 1 ̊ossicification centers • Are found in epiphyses • Spongy bone forms in all directions from 2̊ ossification center

  19. Histology of bone • Types of bone • Compact/dense bone • Dense & strong • Cancellous/spongy bone • Many open spaces

  20. Compact bone • Structure • Haversian Canal (osteon) • Allows for metabolism of surrounding mineral salts within compact bone • Looks similar to rings around central blood vessels • Blood vessels found within haversian or central canal • Concentric (circular) rings are called lamella • Lacunae • Tiny cavities that contain the osteocytes • Located between two lamella or rings of bone

  21. Compact Bone • Each lacunae are connected to all other lacunae through smaller canals= canaliculi • Canaliculi run horizontally between haversian canals • Also contain blood vessels • Same as Volkmann’s or perforating canals • Canaliculi • Allow osteocytes to get oxygen & nutrients and dispose of waste products & CO2

  22. Cancellous Bone • Also called spongy bone • Located at ends of long bones and also forms center of all other bones • Trabeculae • Network that forms the network of interconnecting sections of bone • Creates sponelike appearance to bone • Gives bone strength without adding weight

  23. Bone Marrow • Red bone marrow • Fills spaces within cancellous bone • Well supplied with blood • Produces blood cells = hematopoiesis • White & red blood cells • Found in adults, but only in select bones • Ribs, vertebrae, sternum, and pelvic bones • Found in humerus & femur but decreases with age

  24. Bone Marrow • Yellow Marrow • Connective tissue that consists largely of fat cells • Found predominantly in shafts of long bones in medullary cavity • Can become red marrow in times of need (major loss of blood) and produce blood cells if necessary

  25. Epiphyseal Plate • Separates diaphysis & epiphysis in long bones • Area of new cell growth in growing bones • Layers of cartilaginous cells • Layer 1- resting cells (found closest to end of epiphysis) • Layer 2- cells undergoing mitosis • Layer 3- older cells enlarging & becoming calicified • Layer 4- dead cells & calcified intercellular substance

  26. Resting cells Cells under going mitosis II III III Older cells enlarging and becoming calcified IV Dead cells and calcified intercellular substance

  27. Maintaining bones • Healthy body • Balance between amount of calcium in blood and calcium stored in bones • Excess calcium secrete via kidneys • Balance controlled by endocrine system • Parathyroid & calcitonin hormones

  28. Hormones involved in Bones • Growth hormone (GH) • Secreted by pituitary gland • Stimulates division of cartilage cells found within epiphyseal plates • Absence of GH • Long bones fail to develop normally and individual fails to grow, leading to pituitary dwarfism • Over production of GH (too much) • Pituitary gigantism • Height over 8 ft tall • Acromegaly • Hands, feet, & jaw enlarge

  29. Hormones • Thyroid hormone • Stimulates replacement of cartilage in epiphyseal plates • Halts bone growth by causing premature ossification • Deficiency (not enough) thyroid hormone may stunt growth • Secreted by thyroid gland • Parathyroid Hormone • Stimulates increase in number & activity of osteoclasts

  30. Hormones • Sex hormones • Estrogen & testosterone • Secreted from ovaries, testes, & adrenal glands • Promotes formation of bone tissue • Increase in abundance at puberty • Also stop bone lengthening at a relatively early age • This effect is stronger in females, because estrogen is stronger than testosterone, so females stop growing sooner than males

  31. Other factors affecting bone growth • Physical stress • Stimulates bone growth • Lack of exercise leads to thinner & weaker bones (atrophy) • Vitamin D • Necessary for absorption of calcium in small intestine • In vitamin D poor diet, calcium is not absorbed properly and deforms bones • Active form of Vit D requires exposure to ultraviolet light • Vitamin A & C • Vitamin A necessary for osteoblast & osteoclast activity (lack may prevent normal bone development) • Vitamin C required for collagen synthesis (also may prevent normal bone development)

  32. Hemopoiesis • Formation of blood cells • Occurs in bone marrow • Red marrow • Produces red blood cells (erythrocytes), white blood cells (leukocytes), and blood platelets • Called red marrow due to red, oxygen-carrying pigement (hemoglobin) that is found inside of the red blood cells

  33. Inorganic salt storage • Inorganic mineral salts account for 70 % of weight of bones • Inorganic salts are mostly tiny crystals of calcium phosphate (hydroxyapatite) • Low blood calcium results in parathyroid hormone stimulating osteoclasts to break down bone matrix releasing calcium into blood stream • High blood calcium results in calcitonin from the thyroid gland, which stimulates osteoblasts to form bone tissue

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