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Chapter 7 The Skeletal System
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Introduction Skeleton: supporting structure
Bones and associated cartilage, tendons, and ligaments Works with muscles for movement Mineral salts form the inorganic matrix of bone Leonardo da Vinci: constructed first correct illustrations of all bones
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The Functions of the Skeletal System
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The Functions of the Skeletal System (cont’d.)
Supports surrounding tissues Protects vital organs and soft tissues Provides levers for muscles to pull on Manufactures blood cells( hematopoiesis) in bone marrow. Stores mineral salts( phosphorous and calcium)
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The Functions of the Skeletal System (cont’d.)
Cartilage Connective tissue Environment in which bone develops in fetus Found at ends of bones and in joints Ligaments - Tough connective tissue Attach bones to bones Tendons Attach muscles to bones
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The Growth and Formation of Bone
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Introduction A three-month fetal skeleton is completely formed (cartilage) Ossification( formation of bones) and growth begin. Osteoblasts invade the cartilage. Longitudinal growth continues until: 15 years of age for girls 16 years of age for boys Bone maturation until 21 years of age
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Deposition of Bone Osteoprogenitor : undifferentiated bone cells
Osteoblasts: embryonic bone cells Formed beneath the fibrovascular membrane which covers the bone( periosteum) Osteocytes: mature osteoblasts Strain on bone (exercise) increases bone strength Osteoclasts: bone reabsorption and remodeling
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How is the deposition of bone controlled?
Why are children told to run and play during their formative years? How is the bone heal when it is brkoen?
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Deposition of bones is controlled by the amount of strain or pressure.
Example: heel bone(calcenum) Exercise will cause bone and muscles to grow thick and strong. Break in a bone, stimulate injured osteocytes to divide and secrete large quantiities of matrix to form new bone. Osteoclasts which are derived from immune system cells reabsorb the bones and remove the old bones.
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Types of Ossification Intramembranous Endochondral
Dense connective membranes replaced by calcium salts Cranial bones Endochondral Bone develops inside cartilage environment All other bones of the body
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Maintaining Bone Endocrine system control
Calcium storage Blood calcium levels Excretion of excess calcium Parathormone: calcium release Calcitonin: calcium storage
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The Histology of Bone
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Introduction Two types of bone: compact and cancellous (spongy)
Osteocytes are same but the arrangement of blood supply is different Cancellous has bone marrow
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The Haversian System of Compact Bone
CloptonHavers: histology of compact bone Haversian canals: run parallel to surface Surrounded by concentric rings of bone Lacunae: cavity containing osteocyte Lacunae connected by canaliculi
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Cancellous Bone Trabeculae: meshwork of bone
Spongy appearance created by trabeculae Bone marrow fills spaces between trabeculae
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Bone Marrow Red marrow Yellow marrow Hematopoiesis
Ribs, sternum, vertebrae, pelvis Yellow marrow Fat storage Shafts of long bones
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The Classification of Bones Based on Shape long short flat irregular sesamoid
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Introduction
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Long Bones Length exceeds width Consist of
Diaphysis: shaft- Interior of the shaft is called medullary cavity with yellow bone marrow. Metaphysis: flared portion Epiphysis: extremity
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Long Bones (cont’d.) Structure of a long bone
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Short Bones Not merely shorter versions of long bones Lack a long axis
Somewhat irregular shape Consist of thin layer of compact tissue over a majority of spongy bone. Examples?
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Flat Bones Thin bones found wherever need for extensive muscle attachment Usually curved Examples?
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Irregular Bones Very irregular shape
Example: vertebrae Spongy bone enclosed by thin layers of compact bone Examples?
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Sesamoid Bones Small rounded bones
Enclosed in tendon and fascial tissue Located adjacent to joints Examples?
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Bone Markings
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Introduction Processes: projections Fossae: depressions
Functions: muscle attachment, articulation, passageways
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Processes Processes: projections from the surface
Spine, condyle, tubercle, trochlea, trochanter, crest, line, head, neck
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Fossae Fossae: depressions Suture, foramen, meatus, sinus, sulcus
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Divisions of the Skeleton
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Divisions of the Skeleton (cont’d.)
Typically has 206 named bones Axial part Skull, hyoid, vertebrae, ribs, sternum Appendicular part Upper extremities or arms Lower extremities or legs
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The Axial Skeleton
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The Cranial Bones Frontal bone (1) Parietal bones (2)
Occipital bone (1) Temporal bone (2) Sphenoid bone (1) Ethmoid bone (1) Auditory ossicles (6)
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The Cranial Bones (cont’d.)
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The Cranial Bones (cont’d.)
(Photography by Dr. David Fankhauser, University of Cincinnati)
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The Cranial Bones (cont’d.)
(Photography by Dr. David Fankhauser, University of Cincinnati)
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The Facial Bones Nasal bones (2) Palatine bones (2)
Maxillary bones (2) Zygomatic bones (2) Lacrimal bones (2) Nasal conchae (2)
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The Facial Bones (cont’d.)
Vomer bone (1) Mandible (1)
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The Facial Bones (cont’d.)
Lateral view of some cranial and facial bones, labeled
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The Facial Bones (cont’d.)
Frontal view of the bones of the skull (Photography by Dr. David Fankhauser, University of Cincinnati)
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The Orbits Orbits: cavities enclose and protect the eyes Area of Orbit
Participating Bones Roof Frontal, sphenoid Floor Maxilla, zygomatic Lateral wall Zygomatic, greater wing of sphenoid Medial wall Maxilla, lacrimal, ethmoid
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(Photography by Dr. David Fankhauser, University of Cincinnati)
The Orbits (Photography by Dr. David Fankhauser, University of Cincinnati)
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The Nasal Cavities Nose framework surrounds the two nasal cavities
Area of Nose Participating Bones Roof Ethmoid Floor Maxilla, palatine Lateral wall Septum of medial wall Ethmoid, vomer, nasal Bridge Nasal
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The Foramina of the Skull
Passageways for blood vessels and nerves Foramen magnum: spinal cord passage
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The Hyoid Bone No articulation with other bones
Suspended by ligaments from styloid process Supports the tongue
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(Photography by Dr. David Fankhauser, University of Cincinnati)
The Hyoid Bone (Photography by Dr. David Fankhauser, University of Cincinnati)
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How to Study the Bones of the Skull
Refer to colored plates in textbook Use a model of a human skull Search for sutures as a guide
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The Torso or Trunk Vertebrae Seven cervical Twelve thoracic
Five lumbar Sacrum Coccyx
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The Thorax Thorax or rib cage made up of:
Sternum Costal cartilages Ribs Bodies of thoracic vertebrae Encloses and protects heart and lungs
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The Thorax (cont’d.)
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(Photography by Dr. David Fankhauser, University of Cincinnati)
The Thorax (cont’d.) (Photography by Dr. David Fankhauser, University of Cincinnati)
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The Sternum Breastbone Has three parts Manubrium Gladiolus
Xiphoid process Attachment for diaphragm and rectus abdominis
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The Ribs Also called costae Attach posteriorly to thoracic vertebrae
12 pairs True ribs, false ribs, floating ribs
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The Appendicular Skeleton
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The Bones of the Upper Extremities
Shoulder girdle: clavicle and scapula Arm Upper arm: humerus Forearm: ulna and radius Wrist: carpals Hand: metacarpals (5/hand) Fingers: phalanges (14/hand)
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The Bones of the Upper Extremities (cont’d.)
Bones of the wrist and hand
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The Bones of the Upper Extremities (cont’d.)
The carpal bones (Photography by Dr. David Fankhauser, University of Cincinnati)
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The Bones of the Upper Extremities (cont’d.)
The metacarpals and phalanges (Photography by Dr. David Fankhauser, University of Cincinnati)
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The Bones of the Lower Extremities
Pelvic girdle: ischium, ilium, pubis Leg Upper leg: femur Lower leg: patella, tibia, fibula Foot Tarsals Metatarsals (5/foot) Phalanges (14/foot)
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The Bones of the Lower Extremities (cont’d.)
Right ankle and foot, lateral view
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The Bones of the Lower Extremities (cont’d.)
Right ankle and foot, superior view
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The Bones of the Lower Extremities (cont’d.)
Lateral view of the bones of the foot (Photography by Dr. David Fankhauser, University of Cincinnati)
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The Bones of the Lower Extremities (cont’d.)
Superior view of the bones of the foot (Photography by Dr. David Fankhauser, University of Cincinnati)
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The Arches of the Foot
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The Arches of the Foot (cont’d.)
Enable foot to bear weight while standing and to provide leverage while walking Medial longitudinal: highest Lateral longitudinal Transverse Pes planus: flat foot
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Summary Listed the functions of the skeletal system
Described the process of growth and formation of bone Described the structure of compact and cancellous bone Defined the various processes and fossae associated with bones
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Summary (cont’d.) Named the bones of the axial and appendicular skeleton Described the arches of the foot
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