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Bones and Skeletal Tissues

Bones and Skeletal Tissues. Chapter 6. http://images5.fanpop.com/image/photos/26500000/-skeleton-dance-skeletons-26529088-725-544.png. Skeletal Cartilages. Contain no blood vessels or nerves

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Bones and Skeletal Tissues

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  1. Bones and Skeletal Tissues Chapter 6 http://images5.fanpop.com/image/photos/26500000/-skeleton-dance-skeletons-26529088-725-544.png

  2. Skeletal Cartilages • Contain no blood vessels or nerves • Perichondrium (dense irregular connective tissue girdle) contains blood vessels for nutrient delivery to cartilage • Types • Hyaline • Elastic • Fibrocartilage

  3. Epiglottis Larynx Thyroid cartilage Cartilage in external ear Cartilages in nose Trachea Cricoid cartilage Lung Articular Cartilage of a joint Cartilage in Intervertebraldisc Costal cartilage Respiratory tube cartilages in neck and thorax Bones of skeleton Pubic symphysis Axial skeleton Meniscus (padlike cartilage in knee joint) Appendicular skeleton Cartilages Articular cartilage of a joint Hyaline cartilages Elastic cartilages Fibrocartilages Figure 6.1

  4. Growth of Cartilage • Appositional • Cells secrete matrix against the external face of existing cartilage • Interstitial • Chondrocytes divide and secrete new matrix, expanding cartilage from within http://www.vetmed.vt.edu/education/curriculum/vm8054/labs/Lab7/IMAGES/elastic%20cartilage%20WITH%20LABEL%20copy.jpg

  5. Bones of the Skeleton Cartilage in external ear Cartilages in nose Articular Cartilage of a joint Cartilage in Intervertebraldisc Costal cartilage Pubic symphysis Meniscus (padlike cartilage in knee joint) Articular cartilage of a joint Figure 6.1

  6. Classification of Bones by Shape • Long bones • Short bones • Flat bones • Irregular bones

  7. Functions of Bones • Support • Protection • Movement • Mineral & Growth Factor Storage • Blood cell formation • Triglyceride storage • Hormone Production

  8. Bone Structure • Bones are organs! • Multiple tissue types • Bone (osseous) tissue, nervous tissue, cartilage, fibrous connective tissue, muscle and epithelial cells (in its blood vessels)

  9. Bone Texture • Compact • Dense outer layer; smooth and solid • Spongy (trabecular) • Honeycomb of flat pieces of bone (trabeculae) deep to compact • Space b/w trabeculae filled with red or yellow bone marrow

  10. Structure of Short, Irregular, and Flat Bones • Periosteumcovered compact bone on the outside • Endosteumcovered spongy bone within • diploë • Bone marrow b/w the trabeculae • Hyaline cartilage on articular surfaces

  11. Structure of Typical Long Bone • Diaphysis • Tubular shaft forms long axis • Compact bone surrounds medullary cavity • Epiphyses (bone ends) • Compact bone outside; spongy bone inside • Articular cartilage covers articular surfaces • Epiphysealline • b/w diaphysis and epiphysis • Remnant of epiphyseal plate

  12. Membranes of Bone • Periosteum • Outer fibrous layer • Inner osteogenic layer • Contains nerve fibers, nutrient blood vessels, and lymphatic vessels that enter the bone via nutrient foramina • Secured to underlying bone by Sharpey’s fibers

  13. Membranes of Bone • Endosteum • Delicate membrane on internal surfaces of bone • Contains osteogenic cells

  14. Hematopoietic Tissue (Red Marrow) • Infants (long bones) • Medullary cavities and spongy bone • Adults (long bones) • Little red marrow • Red marrow in flat and some irregular bones is most active http://www.gla.ac.uk/ibls/US/fab/images/generic/bocompac.jpg

  15. Bone Markings • Projections, depressions, and holes • Sites of attachment for muscles, ligaments, and tendons • Joint surfaces • Passageways for blood vessels and nerves

  16. Bone Markings: Projections • Sites of muscle and ligament attachment • Tuberosity • Crest • Trochanter • Line • Tubercle • Epicondyle • Spine • Process • Projections that help to form joints • Head • Facet • Condyle • Ramus

  17. Bone Markings: Depressions and Openings • Passages for blood vessels and nerves • Meatus • Sinus • Fossa • Groove • Fissure • Foramen

  18. Microscopic Anatomy of Bone

  19. Microscopic Anatomy of Bone: Compact Bone • Haversiansystem (or osteon) • Lamellae • Central (Haversian) canal

  20. Microscopic Anatomy of Bone: Compact Bone • Perforating (Volkmann’s) canals • Lacunae • Canaliculi

  21. Microscopic Anatomy of Bone: Spongy Bone • Trabeculae • Align along lines of stress • No osteons • Irregularly arranged lamellae, osteocytes, and canaliculi • Capillaries in endosteumsupply nutrients

  22. Chemical Composition of Bone • Organic • Bone cells • Osteoid—organic bone matrix secreted by osteoblasts • Ground substance, collagen fibers • Inorganic • Hydroxyapatites (mineral salts) • 65% of bone by mass • Mainly calcium phosphate crystals

  23. Bone Development • Ossification (osteogenesis): process of bone tissue formation • Formation of bony skeleton • Begins in 2nd month of development • Postnatal bone growth • Until early adulthood • Bone remodeling and repair • Lifelong

  24. Types of Ossification • Endochondral ossification • Bone forms by replacing hyaline cartilage • Majority of skeleton • Intramembranous ossification • Bone develops from fibrous membrane • Bones called membrane bones • Forms flat bones, e.g. clavicles and cranial bones

  25. Endochondral Ossification • Forms most all bones inferior to base of skull (except clavicles) • Begins late in 2nd month of development • Uses hyaline cartilage models • Hyaline cartilage must be broken down before ossification

  26. Month 3 Birth Childhood toadolescence Week 9 Articularcartilage Secondaryossificationcenter Spongybone Epiphysealblood vessel Area ofdeterioratingcartilage matrix Epiphysealplatecartilage Hyalinecartilage Medullarycavity Spongyboneformation Bonecollar Bloodvessel ofperiostealbud Primaryossificationcenter 1 2 3 4 5 Figure 6.9

  27. Intramembranous Ossification • Forms cranial bones of the skull and clavicles • Begins within fibrous connective tissue membranes formed by mesenchymal cells • Ossification centers appear • Osteoid is secreted • Woven bone and periosteum form • Lamellar bone replaces woven bone & red marrow appears

  28. Figure 6.9 Intramembranous ossification. Osteoblast Mesenchymal cell Osteoid Collagen fibril Ossification center Osteocyte Newly calcified bone matrix Osteoid Osteoblast 1Ossificationcentersappearinthefibrous connectivetissue membrane. 2 Osteoid is secreted within the fibrous membrane and calcifies. Fibrous periosteum Mesenchyme condensing to form the periosteum Osteoblast Plate of compact bone Trabeculae of woven bone Diploë (spongy bone) cavities contain red marrow Blood vessel 3 Wovenboneandperiosteumform. 4Lamellar bone replaces woven bone, just deep to the periosteum. Red marrow appears.

  29. Postnatal Bone Growth • Interstitial growth: •  length of long bones • Appositional growth: •  thickness and remodeling of all bones by osteoblasts and osteoclasts on bone surfaces

  30. Interstitial (Longitudinal) Growth • Epiphyseal plate cartilage organizes into 5important functional zones: • Resting (quiescent) zone • Proliferation (growth) • Hypertrophic • Calcification • Ossification (osteogenic)

  31. Resting zone Proliferation zone Cartilage cells undergo mitosis. 1 Hypertrophic zone Older cartilage cells enlarge. 2 Calcification zone Matrix becomes calcified; cartilage cells die; matrix begins deteriorating. 3 Calcified cartilage spicule Osteoblast depositing bone matrix Ossification zone New bone formation is occurring. 4 Osseous tissue (bone) covering cartilage spicules Figure 6.10

  32. Appositional Growth • Growth in Width • Osteoblasts active in periosteum • Osteoclasts active in the endosteum • Building > Breaking down = thicker stronger bone

  33. Bone remodeling Bone growth Articular cartilage Cartilage grows here. Epiphyseal plate Cartilage is replaced by bone here. Bone is resorbed here. Cartilage grows here. Bone is added by appositional growth here. Cartilage is replaced by bone here. Bone is resorbed here. Figure 6.11

  34. Hormonal Regulation of Bone Growth • Growth hormone • Thyroid hormone • Testosterone and Estrogen http://2.bp.blogspot.com/-FrC7iCwLqDk/Tb8hrWvYXnI/AAAAAAAAOOg/i-l4zBWZI5Q/s1600/2008_01_17_pb%252520kids%252520growth.jpg

  35. Bone Remodeling • Bone is constantly being “recycled” • Occurs @ surface of periosteum and endosteum • Deposit • Injury or needed strength, requires good diet • Osteoid seam and Calcification front • Resorption • Osteoclasts secrete: lysosomal enzymes, acids • Dissolved matrix is transcytosed

  36. Control of Remodeling • What controls continual remodeling of bone? • Hormonal mechanisms that maintain calcium homeostasis in the blood • Mechanical and gravitational forces http://tutor4physics.com/workliftbox.gif

  37. Hormonal Control of Blood Ca2+ • Most calcium in the body is in the bones • Less that 1.5g in blood – tightly regulated narrow range • Calcium is necessary for • Transmission of nerve impulses • Muscle contraction • Blood coagulation • Secretion by glands and nerve cells • Cell division

  38. Calcium homeostasis of blood: 9–11 mg/100 ml BALANCE BALANCE Stimulus Falling blood Ca2+ levels Thyroid gland Osteoclasts degrade bone matrix and release Ca2+ into blood. Parathyroid glands Parathyroid glands release parathyroid hormone (PTH). PTH Figure 6.12

  39. Hormonal Control of Blood Ca2+ • May be affected to a lesser extent by calcitonin  Blood Ca2+ levels  Parafollicular cells of thyroid release calcitonin  Osteoblasts deposit calcium salts   Blood Ca2+levels

  40. Response to Mechanical Stress • Wolff’s law: A bone grows or remodels in response to forces or demands placed upon it

  41. Hormones and Mechanical Stress • Hormones – • when remodeling occurs • As a response to what??? • Mechanical Stress • Where the remodeling occurs

  42. Classification of Bone Fractures • Bone fractures may be classified by four “either/or”classifications • Position of bone ends after fracture: • Nondisplaced or Displaced • Completeness of the break • Complete or Incomplete • Orientation of the break to the long axis of the bone: • Linear or transverse • Whether or not the bone ends penetrate the skin • Compound (open) or Simple (closed)

  43. Common Types of Fractures • In addition to the previous classification, all fractures can be described in terms of • Location • External appearance • Nature of the break http://www.schultzlegalgroup.com/images/Bone-Fracture-Injury-Lawyer.jpg

  44. Table 6.2

  45. Table 6.2

  46. Table 6.2

  47. Fracture Healing • Hematoma forms • Fibrocartilaginous callus forms

  48. Fracture Healing • Bony callus formation • Bone remodeling

  49. Homeostatic Imbalances • Osteomalacia and Rickets • Calcium salts not deposited • Rickets (childhood disease) causes bowed legs and other bone deformities • Cause: vitamin D deficiency or insufficient dietary calcium http://upload.wikimedia.org/wikipedia/commons/thumb/a/a9/XrayRicketsLegssmall.jpg/230px-XrayRicketsLegssmall.jpg

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