skeletal system notes
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Skeletal System
Websites for HEEEELLLPPPP!!!
1. http://www.bio.psu.edu/people/faculty/strauss/anatomy/skel/skeletal.htm
2. http://depts.washington.edu/bonebio/bonAbout/structure.html3. http://www.leeds.ac.uk/chb/lectures/anatomy3.html4. http://homepage.mac.com/myers/misc/bonefiles/bonestruct.html5. http://www.bbc.co.uk/science/humanbody/body/interactives/3djigsa
w_02/index.shtml?skeleton6. http://www.bartleby.com/107/17.html7. http://sv.berkeley.edu/showcase/pages/bones.html8. http://www.innerbody.com/image/skelfov.html9. http://www.medtropolis.com/VBody.asp10.http://wps.aw.com/bc_martini_eap_4/40/10466/2679495.cw/content
/index.html
2 Divisions of Skeletal System
• Axial skeleton• Appendicular skeleton
Axial Skeleton
• 80 bones • Consist of bones in the:
– Skull– Vertebral Column– Thorax– Hyoid
Appendicular
• 126 bones• Bones in the:
– Shoulders– Upper limbs– Lower limbs– Pelvic girdle
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
Classification of Bones: By Shape
• Long bones – longer than they are wide (e.g., humerus)
Figure 6.2a
Classification of Bones: By Shape
• Short bones– Cube-
shaped bones of the wrist and ankle
– Bones that form within tendons
Figure 6.2b
Classification of Bones: By Shape
• Flat bones – thin, flattened, and a bit curved (e.g., sternum, and most skull bones)
Figure 6.2c
Classification of Bones: By Shape
• Irregular bones – bones with complicated shapes (e.g., vertebrae and hip bones)
Figure 6.2d
Classification of Bones: By Shape
• Sesamoid – knee bone (e.g., patella only)
Figure 6.2d
Patella
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
Function of Bones
• Mineral storage – reservoir for minerals, especially calcium and phosphorus
• Blood cell formation – (hematopoiesis) occurs within the marrow cavities of bones
Gross Anatomy of Bones: Bone Textures
• Compact bone – dense outer layer
• Spongy bone – honeycomb of trabeculae filled with bone marrow
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
Typical Long Bone Structure
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)
Structure of Long Bone
Figure 6.3
Structure of Long Bone
Figure 6.3a
Structure of Long Bone
Figure 6.3b
Structure of Long Bone
Figure 6.3c
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)
Bone Surface MarkingsForamen HOLE through which blood vessels, nerves, or ligaments pass through (ex. Foramen magnum)
Bone Surface Markings
Meatus PASSAGE extending within a bone (ex. External auditory meatus)
Bone Surface Markings
• Fossa DITCH or shallow depression on a bone (ex. Mandibular fossa of temporal bone)
Bone Surface Markings
• Head rounded projection that forms a joint & supported (ex. Head of femur)
Bone Surface Markings
• Crest Prominent ridge (ex. illiac crest of pelvic bone)
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
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Microscopic Structure of Bone: Compact Bone
Microscopic Structure of Bone: Compact Bone• Haversian system, or osteon – the structural unit
of compact bone
Parts of the Osteon (Haversian System)
– Lamella – weight-bearing, column-like matrix tubes composed mainly of collagen
– Haversian, or central canal – central channel containing blood vessels and nerves
– 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
Microscopic Structure of Bone: Compact Bone
• Lacuna – small cavities in bone that contain osteocytes
• Canaliculi – hairlike canals that connect lacuna to each other and the central canal
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Hyoid Bone
• Only bone that does not articulate directly with another bone
• Attachment point for neck muscles and assists during swallowing and speech
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)
Vertebral Column
Figure 7.13
Bony Thorax (Thoracic Cage)
• Functions– Protects the heart & lungs
Comparison of Male and Female Pelves
Developmental Aspects: Fetal Skull
• Bones are not fully connected and held together by fontanels
• Fontanels– Unossified membranes – 4: anterior, posterior, mastoid, and sphenoid
Developmental Aspects: Fetal Skull
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 Clip
Homeostasis of Bone Tissue
Nutrition1. Vitamin D absorbs calcium
in small intestine2. Vitamin A bone resorption3. 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)
Developmental Aspects of Bones
• By age 25, all bones are ossified
• Until age of 25 osteoblasts dominate• Mid-old age osteoclasts dominate
Developmental Aspects: Old Age
• Intervertebral discs become thin• Loss of stature by several centimeters is
common after age 55 • All bones lose mass
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
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
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
Stages of Endochondral Ossification
Figure 6.8
Formation ofbone collararound hyalinecartilage model.
Hyalinecartilage
Cavitation ofthe hyaline carti-lage within thecartilage model.
Invasion ofinternal cavitiesby the periostealbud and spongybone formation.
Formation of themedullary cavity asossification continues;appearance of sec-ondary ossificationcenters in the epiphy-ses in preparationfor stage 5.
Ossification of theepiphyses; whencompleted, hyalinecartilage remains onlyin the epiphyseal platesand articular cartilages.
Deterioratingcartilagematrix
Epiphysealblood vessel
Spongyboneformation
Epiphysealplatecartilage
Secondaryossificatoncenter
Bloodvessel ofperiostealbud
Medullarycavity
Articularcartilage
Spongybone
Primaryossificationcenter
Bone collar
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5
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Functional Zones in Long Bone Growth
• Growth zone – cartilage cells undergo mitosis, pushing the epiphysis away from the diaphysis
“This is how you grow