Skeletal System Notes

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  • The atlas is just under the head and it is named for Atlas, the Greek god who supported the world on his shoulders. Because the god Atlas often adorned maps, a compilation of maps came to be known as an atlasAxis because world rotates on an axis
  • When a low blood calcium condition exists, the parathyroid glands respond by releasing parathyroid hormone (PTH). This hormone stimulates osteoclasts to break down bone tissue, and as a result, calcium salts are released into the blood. On the other hand, if the blood calcium level is excessively high, the thyroid gland responds by releasing a hormone called calcitonin. Its effect is opposite that of parathyroid hormone; it inhibits osteoclast activity allowing osteoblasts to form bone tissue. As a result, the excessive calcium is stored in bone matrix. The actions of these hormones are both excellent examples of some important negative feedback loops present in our bodies
  • Skeletal System Notes

    1. 1. Skeletal System
    2. 2. Websites for HEEEELLLPPPP!!! 1. http://www.bio.psu.edu/people/faculty/strauss/anatomy/skel/skeletal. htm 2. http://depts.washington.edu/bonebio/bonAbout/structure.html 3. http://www.leeds.ac.uk/chb/lectures/anatomy3.html 4. http://homepage.mac.com/myers/misc/bonefiles/bonestruct.html 5. http://www.bbc.co.uk/science/humanbody/body/interactives/3djigsa w_02/index.shtml?skeleton 6. http://www.bartleby.com/107/17.html 7. http://sv.berkeley.edu/showcase/pages/bones.html 8. http://www.innerbody.com/image/skelfov.html 9. http://www.medtropolis.com/VBody.asp 10.http://wps.aw.com/bc_martini_eap_4/40/10466/2679495.cw/content/ index.html
    3. 3. 2 Divisions of Skeletal System • Axial skeleton • Appendicular skeleton
    4. 4. Axial Skeleton • 80 bones • Consist of bones in the: – Skull – Vertebral Column – Thorax – Hyoid
    5. 5. Appendicular • 126 bones • Bones in the: – Shoulders – Upper limbs – Lower limbs – Pelvic girdle
    6. 6. 206 Bones????• 24 Ribs • 1 Sternum • 26 Vertebrae • 56 Phalanges • 2 Clavicles • 2 Scapula • 2 Humerus • 2 Radius • 2 Ulna • 2 Femur • 2 Tibia • 2 Fibula • 2 Patella • 22 cranial/facial • 14 Tarsals • 16 Carpals • 10 metatarsals • 10 metacarpals • 2 pelvic bones • 1 hyoid • 6 ear ossicles
    7. 7. Classification of Bones: By Shape • Long bones – longer than they are wide (e.g., humerus) Figure 6.2a
    8. 8. Classification of Bones: By Shape • Short bones – Cube- shaped bones of the wrist and ankle – Bones that form within tendons Figure 6.2b
    9. 9. Classification of Bones: By Shape • Flat bones – thin, flattened, and a bit curved (e.g., sternum, and most skull bones) Figure 6.2c
    10. 10. Classification of Bones: By Shape • Irregular bones – bones with complicate d shapes (e.g., vertebrae and hip bones) Figure 6.2d
    11. 11. Classification of Bones: By Shape • Sesamoid – knee bone (e.g., patella only) Figure 6.2d Patella
    12. 12. Function of Bones • Support – form the framework • Protection – provide a protective case for the brain, spinal cord, and vital organs • Movement – provide levers for muscles
    13. 13. Function of Bones • Mineral storage – reservoir for minerals, especially calcium and phosphorus • Blood cell formation – (hematopoiesis) occurs within the marrow cavities of bones
    14. 14. Gross Anatomy of Bones: Bone Textures • Compact bone – dense outer layer • Spongy bone – honeycomb of trabeculae filled with bone marrow
    15. 15. Spongy Bone • Does NOT contain osteons (structural units) • Made up of trabeculae (irregular latticework) • Btw. spaces of trabeculae is filled with red bone marrow • Only site of RED bone marrow: (Forms blood cells) • Vertebrae • Skull • Hips • Ribs • Sternum • Ends of long bones
    16. 16. Typical Long Bone Structure
    17. 17. Bone Structure – Typical Long Bone • Diaphysis = shaft, yellow bone marrow produced here • Epiphyses = distal & proximal ends • Epiphyseal line = remnant of epiphyseal plate • Periosteum = outer, fibrous, protective covering, essential for bone growth & diameter • Endosteum = inner lining of medullary cavity, contains bone forming cells (osteoblasts) • Articular cartilage = pad of hyaline cartilage on the epiphyses where long bones articulate or join, reduces friction, absorbs shock • Medullary cavity= space w/in diaphysis that contains fatty yellow marrow (produces blood cells)
    18. 18. Structure of Long Bone Figure 6.3
    19. 19. Structure of Long Bone Figure 6.3a
    20. 20. Structure of Long Bone Figure 6.3b
    21. 21. Structure of Long Bone Figure 6.3c
    22. 22. Bone Tissue • mineral salt makes them hard – Magnesium salts – Calcium salts – Phosphorus salts • collagen fibers gives them tensile strength (the maximum stress the bone can handle w/out breaking)
    23. 23. Bone Surface Markings Foramen HOLE through which blood vessels, nerves, or ligaments pass through (ex. Foramen magnum)
    24. 24. Bone Surface Markings Meatus PASSAGE extending within a bone (ex. External auditory meatus)
    25. 25. Bone Surface Markings • Fossa DITCH or shallow depression on a bone (ex. Mandibular fossa of temporal bone)
    26. 26. Bone Surface Markings • Head rounded projection that forms a joint & supported (ex. Head of femur)
    27. 27. Bone Surface Markings • Crest Prominent ridge (ex. illiac crest of pelvic bone)
    28. 28. Chemical Composition of Bone: Organic • Osteo means bone • Osteoblasts – bone-forming cells • Osteocytes – mature bone cells • Osteoclasts – large cells that resorb or break down bone matrix
    29. 29. Microscopic Structure of Bone: Compact Bone
    30. 30. Microscopic Structure of Bone: Compact Bone • Haversian system, or osteon – the structural unit of compact bone
    31. 31. Parts of the Osteon (Haversian System) – Lamella – weight-bearing, column-like matrix tubes composed mainly of collagen
    32. 32. – Haversian, or central canal – central channel containing blood vessels and nerves
    33. 33. – Volkmann’s canals – channels lying at right angles to the central canal, connecting blood and nerve supply of the periosteum to that of the Haversian canal
    34. 34. Microscopic Structure of Bone: Compact Bone • Lacuna – small cavities in bone that contain osteocytes
    35. 35. • Canaliculi – hairlike canals that connect lacuna to each other and the central canal
    36. 36. Hyoid Bone • Only bone that does not articulate directly with another bone • Attachment point for neck muscles and assists during swallowing and speech
    37. 37. Vertebral Column • Formed from 26 irregular bones • Cervical vertebrae – 7 bones of the neck • C1=Atlas • C2=Axis – Thoracic vertebrae – 12 bones of the torso – Lumbar vertebrae – 5 bones of the lower back – Sacrum –5 fused bones – Coccyx- 3-5 fused bones (tailbone)
    38. 38. Vertebral Column Figure 7.13
    39. 39. Bony Thorax (Thoracic Cage) • Functions – Protects the heart & lungs
    40. 40. Comparison of Male and Female Pelves
    41. 41. Developmental Aspects: Fetal Skull • Bones are not fully connected and held together by fontanels • Fontanels – Unossified membranes – 4: anterior, posterior, mastoid, and sphenoid
    42. 42. Developmental Aspects: Fetal Skull
    43. 43. Bone Deposition • Occurs where bone is injured or added strength is needed • Requires a diet rich in – Protein – Vitamins C, D, and A – Calcium – Phosphorus – Magnesium – Manganese
    44. 44. Homeostasis of Bone Tissue Nutrition 1. Vitamin D absorbs calcium in small intestine 2. Vitamin A bone resorption 3. Vitamin C Hardens bones Hormones 1. Growth Hormone (from pituitary gland) stimulates growth 2. Parathyroid  Can increase calcium levels (PTH) 3. Thyroid Can decrease calcium levels (Calcitonin)
    45. 45. Developmental Aspects of Bones • By age 25, all bones are ossified • Until age of 25 osteoblasts dominate • Mid-old age osteoclasts dominate
    46. 46. Developmental Aspects: Old Age • Intervertebral discs become thin • Loss of stature by several centimeters is common after age 55 • All bones lose mass
    47. 47. Ossifications • Intramembranous= forms flat bones • Endochondral= forms all other bones • http://health.howstuffworks.com/adam- 200125.htm • http://commons.bcit.ca/biology/ossification/ files/ossification.html
    48. 48. Intramembranous ossification: FLAT BONES • Mesenchymal stem cells develop into osteoblasts that secrete osteoids that develop into bone tissue • Spongy bone is formed followed by compact bone surrounding medullary cavity
    49. 49. Endochondral Ossification: LONG BONES 1. Cartilage model formed 2. Primary ossification center formed in diaphysis 3. Blood vessels, medullary cavity formed 4. Secondary ossification center formed in epiphysis 5. Compact bone, articular cartilage, and epiphyseal plate take shape
    50. 50. Stages of Endochondral Ossification Figure 6.8 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
    51. 51. Functional Zones in Long Bone Growth • Growth zone – cartilage cells undergo mitosis, pushing the epiphysis away from the diaphysis “This is how you grow
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