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

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 /vm8054/labs/Lab7/IMAGES/elastic%20cartilage% 20WITH%20LABEL%20copy.jpg

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

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 Periosteum covered compact bone on the outside Endosteum covered 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 Epiphyseal line – b/w diaphysis and epiphysis – Remnant of epiphyseal plate


13 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

14 Membranes of Bone Endosteum – Delicate membrane on internal surfaces of bone – Contains osteogenic cells

15 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

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

17 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

18 Bone Markings: Depressions and Openings Passages for blood vessels and nerves – Meatus – Sinus – Fossa – Groove – Fissure – Foramen

19 Microscopic Anatomy of Bone

20 Microscopic Anatomy of Bone: Compact Bone Haversian system (or osteon) – Lamellae – Central (Haversian) canal

21 Perforating (Volkmann ’ s) canals Lacunae Canaliculi Microscopic Anatomy of Bone: Compact Bone

22 Microscopic Anatomy of Bone: Spongy Bone Trabeculae – Align along lines of stress – No osteons – Irregularly arranged lamellae, osteocytes, and canaliculi – Capillaries in endosteum supply nutrients

23 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

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

25 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

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

27 Figure 6.9 Hyaline cartilage Area of deteriorating cartilage matrix Epiphyseal blood vessel Spongy bone formation Epiphyseal plate cartilage Secondary ossification center Blood vessel of periosteal bud Medullary cavity Articular cartilage Childhood to adolescence Birth Week 9 Month 3 Spongy bone Bone collar Primary ossification center 12345

28 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

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

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

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

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

33 Appositional Growth Growth in Width – Osteoblasts active in periosteum – Osteoclasts active in the endosteum – Building > Breaking down = thicker stronger bone

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

35 Hormonal Regulation of Bone Growth Growth hormone Thyroid hormone Testosterone and Estrogen l4zBWZI5Q/s1600/2008_01_17_pb%252520kids%252520growth.jpg

36 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

37 Control of Remodeling What controls continual remodeling of bone? – Hormonal mechanisms that maintain calcium homeostasis in the blood – Mechanical and gravitational forces

38 Hormonal Control of Blood Ca 2+ 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

39 Figure 6.12 Osteoclasts degrade bone matrix and release Ca 2+ into blood. Parathyroid glands Thyroid gland Parathyroid glands release parathyroid hormone (PTH). Stimulus Falling blood Ca 2+ levels PTH Calcium homeostasis of blood: 9–11 mg/100 ml BALANCE

40 Hormonal Control of Blood Ca 2+ May be affected to a lesser extent by calcitonin  Blood Ca 2+ levels  Parafollicular cells of thyroid release calcitonin  Osteoblasts deposit calcium salts   Blood Ca 2+ levels

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

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

43 Classification of Bone Fractures Bone fractures may be classified by four “ either/or ” classifications 1.Position of bone ends after fracture: Nondisplaced or Displaced 2.Completeness of the break Complete or Incomplete 3.Orientation of the break to the long axis of the bone: Linear or transverse 4.Whether or not the bone ends penetrate the skin Compound (open) or Simple (closed)

44 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 Injury-Lawyer.jpg

45 Table 6.2



48 Fracture Healing 1.Hematoma forms 2.Fibrocartilaginous callus forms

49 Fracture Healing 3.Bony callus formation 4.Bone remodeling

50 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 RicketsLegssmall.jpg/230px-XrayRicketsLegssmall.jpg

51 Homeostatic Imbalances Osteoporosis – Loss of bone mass – Spongy bone of spine and neck of femur become most susceptible to fracture – Risk factors Lack of estrogen, calcium or vitamin D; petite body form; immobility; low levels of TSH; diabetes mellitus; smoking

52 Developmental Aspects of Bones Embryonic skeleton ossifies predictably so fetal age easily determined from X rays or sonograms At birth, most long bones are well ossified (except epiphyses)

53 Developmental Aspects of Bones Nearly all bones completely ossified by age 25 Bone mass decreases with age beginning in 4th decade Rate of loss determined by genetics and environmental factors In old age, bone resorption predominates

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