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The Skeletal System
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Divisions of the Skeletal System
The human skeletal system is divided into two major divisions Axial Skeleton Appendicular skeleton
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Axial Skeleton The axial skeleton contains the bones of the head, neck, and torso (80 bones total)
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appendicular skeleton
The appendicular skeleton contains the bones of the upper and lower extremities (126 bones total)
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Human Skeleton The human skeleton has a total of 206 bones in all
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Bones Functions: Support Protection Movement Storage
Blood cell formation
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Bones Function- Support
Form the internal framework that supports and anchors all soft organs
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Bones Function- Protection Bones protect soft body organs
Ex. Skull protects brain
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Bones Function- Movement Skeletal Muscles attach to bones by tendons
Bones are used as levers to move body
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Bones Functions-storage Fat is stored in internal cavities of bones
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Bones Functions-storage Store minerals
Most important—Calcium and phosphorus
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Bones Functions-storage
Calcium in its ion form (Ca 2+ ) must always be present in blood for nervous system to transmit messages For muscles to contract For blood to clot Bones are a storage place for Calcium
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Bones Functions-storage Blood cell formation
Hematopoiesis (formation of blood cells) occurs in the cavities of bone marrow
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Bones Classification of bones 2 basic types of bone types Compact Bone
Spongy Bone
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Bones Compact Bone Dense Looks smooth
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Bones Spongy Bone Small needle-like pieces of bone Lots of open space
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Shapes of Bones Long Bones Short Bones Irregular Bones
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Bones Long Bones Longer than they are wide
Usually have a shaft with heads at both ends Mostly compact bones most bones of limbs
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Bones Short Bones Generally cube-shaped Mostly spongy bone
Ex. Patella (knee cap) , bones of wrist and ankle
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Flat Bones Thin, flattened, usually curved
Two thick layers of compact bone sandwiching a layer of spongy bone Bones of skull, ribs, sternum
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Irregular Bones Don’t fit other categories Ex. Vertebrate, hip bone
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Structure of a long bone
Diaphysis- Shaft Makes up most of the bone’s length Composed of compact bone Covered and protected by periosteum
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Structure of a long bone
Cavity of shaft In infants- this area forms blood cells Red marrow In adults primarily filled with yellow marrow (adipose) Called yellow marrow cavity or medullary cavity Red marrow is confined to spongy bone
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Structure of a long bone
Epiphyses- the ends of the long bone Epiphyseal line Thin line spanning the epiphysis
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Structure of a long bone
Epiphyseal plate Plate of hyaline cartilage Causes the lengthwise growth of a long bone By end of puberty the plate is completely replaced by bone
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Structure of Long Bone Surfaces of bones aren’t smooth Bone markings
Bumps, holes, and ridges Bone markings Reveal where muscles, tendons, and ligaments were attached Reveal where blood vessels and nerves passed Occipital bone marking
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Structure of Long Bone Bone markings Projections or processes-
Grow out from the bone surface Depressions or cavities Indentations in the bone Eye cavity
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Structure of a long Microscopic anatomy Compact bone:
To the naked eye looks very dense With microscope we see a much different picture!
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Structure of a long Microscopic anatomy Compact bone
Passageways carrying nerves and blood vessels Provides living bone with nutrients and route for waste disposal
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Structure of Long Bone Osteocytes The mature bone cells
Found in cavities of the bone matrix called lacunae ( a very tough matrix)
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Structure of Long Bone Osteocytes
Lacunae arranged in concentric circles called lamellae Lacunae arranged around central (Haversian) canals
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Structure of Long Bone Perforating (Volkmann’s) canals
Run into the compact bone at right angles to the shaft Let the inside of bone communicate with outside
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Bone Formation, Growth, and Remodeling
Embryo’s skeleton Primarily hyaline cartilage Young child Most of cartilage has been replaced by bone Remains in isolated areas Bridge of nose Parts of ribs joints
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Bone Formation, Growth, and Remodeling
Most bones develop using hyaline cartilage structures as their “models” Ossification- the formation of bone
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Bone Formation, Growth, and Remodeling
Ossification 2 major stages 1. hylane cartilage model is completely covered with bone by bone forming cells called osteoblasts
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Bone Formation, Growth, and Remodeling
Ossification Step Two: Hyaline cartilage model is digested away Opens up a medullary cavity within newly formed bone
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Bone Formation, Growth, and Remodeling
By birth Most hyaline cartilage models have been converted to bone Excepts two reasons Articular cartilages –cover bone ends Epiphyseal plates
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Bone Formation, Growth, and Remodeling
Articular cartilages Persist for life Reduce friction at the joint surfaces
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Bone Formation, Growth, and Remodeling
How is the articular cartilage injured? Trauma- twisting, sport injury Certain diseases Gradually over time
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Bone Formation, Growth, and Remodeling
When there is significant loss of the articular cartilage, the knee is considered to have “arthritis”.
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Bone Formation, Growth, and Remodeling
Epiphyseal plates Provide for longitudinal growth of long bones during childhood New cartilage is formed on external surface Old cartilage is broken down and replaced by bony matrix
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Bone Formation, Growth, and Remodeling
Epiphyseal plates Growth controlled by hormones Ends during adolescence, when the epiphyseal plates are completely converted to bone
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Bone Formation, Growth, and Remodeling
How do bones widen? –called Appositional Growth Osteoblasts in the periosteum add bone to the external face Osteoclasts in the endosteum remove bone from inner wall
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What happens when long bone growth ends?
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Bone Formation, Growth, and Remodeling
Bone Remodeling Bones continually remodeled in response to 2 factors: 1. calcium levels in the blood 2. the pull of gravity and muscles on the skeleton
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Bone Formation, Growth, and Remodeling
Bone Remodeling When blood calcium levels are low Parathyroid hormone (PTH) is released into blood PTH activates osteoclasts (bone destroying cells) to break down bone matrix and release calcium
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Bone Formation, Growth, and Remodeling
Bone Remodeling When blood calcium levels are too high (hypercalcemia) Calcium is deposited in bone matrix as hard calcium salts
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Bone Formation, Growth, and Remodeling
Bone Remodeling Essential for bones to: retain normal proportions Strengthen as body increases size and weight
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Bone Formation, Growth, and Remodeling
Bone Remodeling Bedridden or physically inactive people tend to lose bone mass and atrophy Because they aren’t subjected to stress
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Bone Formation, Growth, and Remodeling
Rickets Disease of children in which bones fail to calcify Bones soften and definite bowing of weight-bearing bones of legs occurs
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Bone Formation, Growth, and Remodeling
Rickets— Called osteomalacia in adults Causes Usually due to lack of calcium in diet Or lack of vitamin D Is needed to absorb calcium
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Divisions of the Skeletal System
Axial
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Bones of the Axial Skeleton
Bones of the axial skeleton are divided into four major groups Bones of the Skull Hyoid Bone Bones of the Spinal Column Sternum and Ribs
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Bones of the Axial Skeleton
Bones of the Skull (28 total) Cranial Bones (8 total) form the cranium which surrounds the brain
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Bones of the Axial Skeleton
Bones of the Skull (28 total) Cranial Bones 1) Frontal Bone (1 bone) Anterior Portion of Cranium (Forehead) Forms Anterior Cranial Floor Forms the Roofs of Orbits (Eye Sockets)
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Bones of the Axial Skeleton
Bones of the Skull (28 total) Cranial Bones 2) Parietal Bone (2 bones) Forms Superior Portion of Cranium
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Bones of the Axial Skeleton
Bones of the Skull (28 total) Cranial Bones 3) Temporal Bone (2 bones) Forms Lateral Portion of Cranium & Lateral Cranial Floor
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Bones of the Axial Skeleton
Bones of the Skull (28 total) Cranial Bones 4) Occipital Bone (1 bone) Forms Posterior Portion of Cranium & Posterior Cranial Floor
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Bones of the Axial Skeleton
Bones of the Skull (28 total) Cranial Bones 5) Sphenoid Bone (1 bone) Forms central portion of cranial floor Known as the “keystone of the cranium” because the sphenoid bone anchors all the other cranial bones
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Bones of the Axial Skeleton
Bones of the Skull (28 total) Cranial Bones 6) Ethmoid Bone (1 bone) Complex, irregularly shaped bone found between the nasal and the sphenoid bones
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Bones of the Axial Skeleton
Bones of the Skull (28 total) Facial Bones 1) Nasal Bone (2 bones) Forms the bridge of the nose
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Bones of the Axial Skeleton
Bones of the Skull (28 total) Facial Bones 2) Maxillary bone (2 Bones) Upper jawbone that forms the central portion of the face Forms the floor of the orbits and the anterior portion of the hard palate
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Bones of the Axial Skeleton
Bones of the Skull (28 total) Facial Bones 3) Zygomatic Bone (2 Bones) Forms the cheekbones and the lateral walls of the orbits
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Bones of the Axial Skeleton
Bones of the Skull (28 total) Facial Bones 4) Mandible Bone (1 Bone) Lower jawbone Largest and strongest bone of the face
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Bones of the Axial Skeleton
Bones of the Skull (28 total) Facial Bones 5) Lacrimal Bone (2 Bones) Forms the medial walls of the orbits Bones are paper thin
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Bones of the Axial Skeleton
Bones of the Skull (28 total) Facial Bones 6) Palatine Bone (2 Bones) Forms posterior portion of the hard palate and forms the lateral and posterior walls of the nasal cavity
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Bones of the Axial Skeleton
Bones of the Skull (28 total) Facial Bones 8) Vomer Bone (1 Bone) Forms the lower portion of the nasal septum
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Bones of the Axial Skeleton
Bones of the Skull (28 total) Bones of the Ear Three tiny bones located in the middle ear 1) Malleus (2 Bones) 2) Incus (2 Bones) 3) Stapes (2 Bones)
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Bones of the Axial Skeleton
Bones of the Skull (28 total) Bones of the Ear Smallest bones in the body Carry sound vibrations to inner ear Amplifies sound about 7x
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Bones of the Axial Skeleton
Hyoid Bone (1 total) The hyoid bone is a U shaped bone found in the neck between the mandible and the larynx It is the only bone in the body which does not form a joint with another bone (held in place by ligaments and muscles)
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Bones of the Axial Skeleton
Hyoid Bone (1 total) Function: Supports the base of the tongue
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Bones of the Axial Skeleton
Vertebral Column –Spine 26 irregular bones connected by ligaments Flexible, curved structure
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Bones of the Axial Skeleton
Vertebral Column –Spine Running through the central cavity of vertebral column is the delicate spinal cord Spine preserves and protects spinal cord
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Bones of the Axial Skeleton
Vertebral Column –Spine Single vertebrae are separated by pads of flexible fibrocartilage called intervertebral discs They cushion the vertebrae and absorb shock
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Bones of the Axial Skeleton
Vertebral Column –Spine Young Person Discs have high water content ( 90%) Discs are spongy and compressible
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Bones of the Axial Skeleton
Vertebral Column –Spine Aging The water content of disc decreases Drying of discs and weakening of ligaments predisposes older people to herniated discs (slipped disc) if slipped disc presses on spinal cord- major pain
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Bones of the Axial Skeleton
Vertebral Column –Spine The spine has 2 curvatures 1. Primary Curvature 2. Secondary Curvature
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Bones of the Axial Skeleton
Vertebral Column –Spine Primary Curvature- curvature in the thoracic and sacral regions Called primary because it is there when we are born
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Bones of the Axial Skeleton
Vertebral Column –Spine Secondary Curvature- Cervical curvature- develops when baby begins to lifts its head Lumbar curvature- develops when baby begins to walk
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Bones of the Axial Skeleton
Several types of abnormal spinal curvature 1. Scoliosis-
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Bones of the Axial Skeleton
Several types of abnormal spinal curvature 2. lordosis-
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Bones of the Axial Skeleton
Several types of abnormal spinal curvature 2. lordosis-
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Several types of abnormal spinal curvature
3. kyphosis-
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Bones of the vertebral column (backbone)
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Bones of the Axial Skeleton
Bones of the Spinal Column (26 total) 1) Cervical Vertebrae (7 Bones) Top seven vertebrae of the spinal column The atlas (to bear )is the first cervical vertebrae The axis is the second cervical vertebrae
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Bones of the Axial Skeleton
Bones of the Spinal Column (26 total) 1) Cervical Vertebrae (7 Bones)
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Bones of the Axial Skeleton
Bones of the Spinal Column (26 total) 2) Thoracic Vertebrae (12 Bones) Middle 12 vertebrae of the spinal column
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Bones of the Axial Skeleton
Bones of the Spinal Column (26 total) 3) Lumbar Vertebrae (5 Bones) Bottom five vertebrae of the spinal column
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Bones of the Axial Skeleton
Bones of the Spinal Column (26 total) 4) Sacrum (5 Bones Fused Into 1 Bone) Five separate vertebrae that fuse into 1 bone after the bones mature
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Bones of the Axial Skeleton
Bones of the Spinal Column (26 total) 5) Coccyx (4 or 5 Bones Fused Into 1 Bone) Tailbone; consists of separate vertebrae that have fused together
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Bones of the Axial Skeleton
Sternum and Ribs (25 total) Sternum (1 Bone) “Breastbone”
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Bones of the Axial Skeleton
Ribs You have two types of ribs True Ribs False Ribs
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Bones of the Axial Skeleton
Sternum and Ribs (25 total) Ribs (12 pairs = 24 Ribs) True Ribs (First 7 pairs) Ribs attach directly to the sternum by costal cartilage
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Bones of the Axial Skeleton
Ribs False Ribs (Bottom 5 pairs) Rib pairs 8, 9, & 10 attach indirectly to the sternum by the costal cartilage of rib pair #7 Rib pairs 11 & 12 are called floating ribs because they do not attach to the sternum at all
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Bones of the Axial Skeleton
All ribs attach to a thoracic vertebrae posteriorly
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Bones of the Axial Skeleton
Bones of the Upper Extremities The sternum, ribs, and vertebral column create the thorax
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Bones of the Appendicular Skeleton
Bones of the Upper Extremities Clavicle (2 Bones) Collarbone
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Bones of the Appendicular Skeleton
Bones of the Upper Extremities Scapula (2 Bones) Shoulder Blade
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Bones of the Appendicular Skeleton
Bones of the Upper Extremities The scapula and clavicle together make up the shoulder girdle
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Bones of the Appendicular Skeleton
Bones of the Upper Extremities Humerus (2 Bones) Long bone of the upper arm
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Bones of the Appendicular Skeleton
Bones of the Upper Extremities Radius (2 Bones) Ulna (2 Bones) The radius and ulna are bones of the forearm The radius is on the thumb side and the ulna is on the little finger side
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Bones of the Appendicular Skeleton
Bones of the Upper Extremities Carpals (16 Bones; 8 in Each Hand) Bones of the wrist
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Bones of the Appendicular Skeleton
Bones of the Upper Extremities Metacarpals (10 Bones, 5 in Each Hand) Bones in the palm of the hand
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Bones of the Appendicular Skeleton
Bones of the Upper Extremities Phalanges (28 Bones, 14 in Each Hand) Bones of the fingers (3 in each finger and 2 in the thumb)
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Bones of the Appendicular Skeleton
Bones of the Lower Extremities (Label bones in your notes !)
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Skeletal Differences in Men & Women
Male Female 110
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Skeletal Differences in Men & Women
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Bones of the Appendicular Skeleton
Bones of the Lower Extremities Femur Bone Thigh bone Longest, largest, and strongest bone in the body
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Bones of the Appendicular Skeleton
Bones of the Lower Extremities Patella (2 Bones) Kneecap
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Bones of the Appendicular Skeleton
Bones of the Lower Extremities Tibia Fibula The tibia and fibula are the bones of the lower leg Tibia “shin bone” is larger, medial, and more superficial than the fibula
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Bones of the Appendicular Skeleton
Bones of the Lower Extremities Tarsal Bones (14 Bones, 7 in Each Foot) Bones that form the heel and the posterior portion of the foot
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Bones of the Appendicular Skeleton
Bones of the Lower Extremities Metatarsals (10 Bones, 5 in each foot) Bones that form the long portion of the foot
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Bones of the Appendicular Skeleton
Bones of the Lower Extremities Phalanges (28 Bones, 14 in each foot) Bones of the toes (3 in each toe except big toe; big toe has 2 bones)
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