2. Figure 6.1: The bones and cartilages of the human skeleton, p. 177. Epiglottis Larynx Trachea Lung Respiratory tube cartilages in neck and thorax = Hyaline cartilages Key: = Fibrocartilages = Elastic cartilages = Bones of axial skeleton = Bones of appendicular skeleton 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)
3. Figure 6.2: Classification of bones on the basis of shape, p. 178. (a) (b) (d) (c) Long bone (humerus) Short bone (triquetral) Irregular bone (vertebra), left lateral view Flat bone (sternum)
4. 2 Types of Bone Tissue Spongy bone Compact bone
5.
6.
7. Figure 6.3: The structure of a long bone (humerus of arm), p. 180. (b) (c) (a) Proximal epiphysis Articular cartilage Yellow bone marrow Endosteum Epiphyseal line Spongy bone Periosteum Compact bone Medullary cavity Spongy bone Compact bone Articular cartilage Compact bone Periosteum Perforating (Sharpey’s) fibers Nutrient arteries Diaphysis Distal epiphysis
8. Figure 6.3a: The structure of a long bone (humerus of arm), p. 180. (a) Proximal epiphysis Articular cartilage Epiphyseal line Spongy bone Periosteum Compact bone Medullary cavity Diaphysis Distal epiphysis Fat
9. Figure 6.6: Microscopic anatomy of compact bone, p. 183. (a) (b) (c) Perforating (Sharpe’s) fibers Compact bone Periosteal blood vessel Periosteum Lacuna Blood vessel Endosteum lining bony canals and covering trabeculae Central (Haversian) canal Spongy bone Blood vessel continues into medullary cavity containing marrow Central (Haversian) canal Canaliculus Lacuna Lamella Osteocyte Osteon (Haversian system) Circumferential lamellae Lamellae Osteon Interstitial lamellae Central canal Perforating (Volkmann’s) canal
10. Figure 6.5: A single osteon, p. 182. Lamellae Collagen fibers Twisting force Nerve fiber Vein Artery with capillaries Structures in the central canal
11. Figure 6.3c: The structure of a long bone (humerus of arm), p. 180. (c) Yellow bone marrow Endosteum Compact bone Periosteum Perforating (Sharpey’s) fibers Nutrient arteries
12.
13.
14.
15. Figure 6.6a: Microscopic anatomy of compact bone, p. 183. (a) Perforating (Sharpey’s) fibers Compact bone Periosteal blood vessel Periosteum Blood vessel Endosteum lining bony canals and covering trabeculae Central (Haversian) canal Spongy bone Blood vessel continues into medullary cavity containing marrow Osteon (Haversian system) Circumferential lamellae Lamellae Perforating (Volkmann’s) canal
16. Figure 6.15: Fetal primary ossification centers at 12 weeks, p. 198. Parietal bone Radius Ulna Humerus Femur Occipital bone Clavicle Scapula Ribs Vertebra Ilium Tibia Frontal bone of skull Mandible
17.
18. Figure 6.7 : Intramembranous ossification, p. 184. Mesenchymal cell Collagen fiber Ossification center Osteoid Osteoblast Osteoid Osteocyte Newly calcified bone matrix Osteoblast An ossification center appears in the fibrous connective tissue membrane . • Selected centrally located mesenchymal cells cluster and differentiate into osteoblasts, forming an ossification center. Bone matrix (osteoid) is secreted within the fibrous membrane. • Osteoblasts begin to secrete osteoid, which is mineralized within a few days. • Trapped osteoblasts become osteocytes. 1 2
19. Figure 6.7 : Intramembranous ossification (continued), p. 184. Mesenchyme Condensing to form the periosteum Blood vessel Trabecula of woven bone Fibrous periosteum Osteoblast Plate of compact bone Diploë (spongy bone) cavities contain red marrow Woven bone and periosteum form. • Accumulating osteoid is laid down between embryonic blood vessels, which form a random network. The result is a network (instead of lamellae) of trabeculae. • Vascularized mesenchyme condenses on the external face of the woven bone and becomes the periosteum. Bone collar of compact bone forms and red marrow appears. • Trabeculae just deep to the periosteum thicken, forming a woven bone collar that is later replaced with mature lamellar bone. • Spongy bone (diploë), consisting of distinct trabeculae, persists internally and its vascular tissue becomes red marrow. 3 4 Intramembranous ossification : develops from FIBROUS CT MEMBRANE ( derived directly from mesenchyme) and results in the formation of MEMBRANE BONES = cranial bones and clavicles Note : all membrane bones are flat bones.
21. Figure 6.8: Endochondral ossification in a long bone, p. 185. Formation of bone collar around hyaline cartilage model. Hyaline cartilage Cavitation of the hyaline carti- lage within the cartilage model. Invasion of internal cavities by the periosteal bud and spongy bone formation. Formation of the medullary cavity as ossification continues; appearance of sec- ondary ossification centers in the epiphy- ses in preparation for stage 5. Ossification of the epiphyses; when completed, hyaline cartilage remains only in the epiphyseal plates and articular cartilages. Deteriorating cartilage matrix Epiphyseal blood vessel Spongy bone formation Epiphyseal plate cartilage Secondary ossificaton center Blood vessel of periosteal bud Medullary cavity Articular cartilage Spongy bone Primary ossification center Bone collar 1 2 3 4 5
22.
23.
24.
25.
26. Figure 6.9: Growth in length of a long bone – zones of the Epiphyseal plate Calcified cartilage spicule Osseous tissue (bone) covering cartilage spicules Growth ( proliferation) zone Cartilage cells undergo mitosis Resting (quiescent) zone Hypertrophic zone Older cartilage cells enlarge Ossification (osteogenic) zone New bone formation is occurring Resorption zone Calcification zone Matrix becomes calcified; cartilage cells die; matrix begins deteriorating Osteoblast depositing bone matrix Diaphyseal face Epiphyseal fac e
27. Figure 6.10: Long bone growth and remodeling during youth, p. 187. Growth Bone grows in length because: Cartilage grows here Cartilage grows here Cartilage replaced by bone here Cartilage replaced by bone here Remodeling Growing shaft is remodeled by: Articular cartilage Bone resorbed here Bone added by appositional growth here Bone resorbed here Epiphyseal plate 1 2 3 4 1 2 3
28.
29.
30.
31. Normal and osteoporotic bone Normal bone Osteoporotic bone www.mayoclinic.com/health/ osteoporosis /DS00128
32. Figure 6.11 : Hormonal control of blood calcium levels , p. 189. PTH; calcitonin secreted Calcitonin stimulates calcium salt deposit in bone Parathyroid glands release parathyroid hormone (PTH) Thyroid gland Thyroid gland Parathyroid glands Osteoclasts degrade bone matrix and release Ca 2+ into blood Falling blood Ca 2+ levels Rising blood Ca 2+ levels Calcium homeostasis of blood: 9–11 mg/100 ml PTH Imbalance Imbalance
33.
34.
35. Figure 6.12: Bone anatomy and stress, p. 190 Load here (body weight) Head of femur Compression here Point of no stress Tension here
Editor's Notes
Started on slide 7 Moved back to slide 6 Slide 7
Structure of a long bone Diaphysis Epiphysis – expanded ends of a long bone consists of mostly spongy bone tissue surrounded by thin layers of compact bone Spongy bone tissue in epiphyses contains red bone marrow in between the trabeculae hematopoiesis (process by which blood cells and platelets are produced) The ends of the epiphyses are covered by thin layers of hyaline cartilage called articular cartilages The surface of a long bone is covered by a membrane called PERIOSTEUM Periosteum double layered outer fibrous layer – highly vascularized because it is composed of dense irregular connective tissue blood vessels extend from the fibrous layer into the bone to provide nutrients and remove metabolic waste inner osteogenic layer – composed of two cell types osteoblasts – secrete bone tissue (derived from mesenchyme) osteoclasts - modified type of white blood cells; destroy bone tissue…. They cause BONE RESORPTION (break down of bone) -------------------------------- After slide 12, 13… moved on to 16? 17
Periosteum is attached to the surface of bone by collagenous fibers called the SHARPEY fibers (also called the PERFORATING fibers) (back to slide 8 to review what we’ve covered so far)
2 nd type of membrane in bones Endosteum – single layered membrane that covers the surfaces of trabeculae in spongy bone end lines the internal surface of the medullary cavity, Haversian canals, and the canaliculi (back to slide 12)
Ossification – Process by which embryonic skeleton is turned into the bony skeleton 2 forms prenatal (before birth, in utero) postnatal (after birth) 2 types of prenatal bone development intramembranous ossification – starting material is fibrous connective tissue membrane (derived from mesenchyme) bones formed via intramembranous ossification are the cranial bones (paired temporal bones, paired parietal bone, single frontal bone, single occipital bone, single ethrnoid bone, single sphenoid bone) AND CLAVICLES the above bones formed via intramembranous ossification are referred to as membrane bones- all membrane bones are flat bones NOT ALL FLAT BONES ARE MEMBRANE BONES HOWEVER, ALL MEMBRANE BONES ARE FLAT BONES. A flat bone is a structural class of bones with flattened, slightly curved appearance consists of 2 thin plates of periosteum-covered compact bones with endosteum covered spongy bone in between the plates (SLIDE 4) endochondral ossification
Prenatal ossification Endochondral ossification starting material is hyaline cartilage secreted by chondroblasts, which are derived from mesenchyme basically, endochondral ossification is the conversion of hyaline cartilage into bone tissue. How? osteoblasts infiltrate the hyaline cartilage and mineralization of the matrix from semi-solid to solid matrix bones form via endochondral ossification are called endochondral bones or cartilage bone (everything minus the 8 cranial bones and 2 clavicles) 126 named bones in the adult skeleton (10 membrane bones vs. 116 endochondral bones) Then she wrote out what she had on slide 23
Now, slide 24
Postnatal bone growth – after birth 2 types longitudinal (linear) bone growth appositional bone growth
Recall that epiphyseal plates are located at the junctions of the diaphysis and the 2 epiphyses of a long bone http://www.bbc.co.uk/schools/gcsebitesize/pe/images/bone_anatomy.gif
Hormonal Control of Bone Remodeling Calcium levels are maintained strictly between 9-11mg/100cc of blood Total Calcium in the adult is about 1.2kg… 99% is stored in bone tissue as the hydroxyapatites When blood levels of calcium fall below 9mg/100cc of blood, it is called HYPOCALCEMIA When blood levels of calcium rise above 11mg/100cc of blood, it is called HYPERCALCEMIA HYPOCALCEMIA AND HYPERCALCEMIA ARE HOMEOSTATIC IMBALANCES… hormones released to maintain normocalcemia (9-11mg/100cc) Homeostatic imbalance – Hypercalcemia stimulates the release of the hormone called calcitonin biological action of calcitonin: stimulates osteoblasts to produce bone tissue mineralized using calcium from blood blood calcium level drops into the normal range also inhibits osteoclasts from causing bone resorption Hypocalcemia stimulates the release of the hornone called PARATHYROID HORMONE (PTH) biological action: stimulates osteoclasts to cause bone resorption release calcium from bones into the blood also stimulates calcium absorption from the small intestine. However PTH action in the Small intestine is INDIRECT b/c PTH first stimulates the synthesis of another hormone called 1,25 dihydroxyvitamin D (vitamin D) directly stimulates calcium absorption from the SI PTH directly stimulates calcium reabsorption from tubular fluid inside the kidneys SUMMARY – PTH increases calcium levels in blood to 9-11mg/100cc of blood *refer to previous slide as necessary*
