Download Unit 5 - Perry Local Schools

Unit 5
The Skeletal System
Bone Function
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Support
Protection
Assist in movements
Mineral homeostasis
Blood cell production
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Hemopoiesis - red bone marrow
Triglyceride storage
Types of Bones
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Long bones: longer than wide
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Short bones: almost cube shaped
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Most wrist and ankle bones
Flat bones: thin and extensive surface
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Such as thigh, leg, arm, forearm, fingers and toes
Such as cranial bones sternum, ribs and scapulas
Irregular bones:
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Such as vertebrae and some facial bones
• Sesamoid Bones
• develop within a tendon
Macroscopic Structure
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Parts of a long bone
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Diaphysis: shaft of long bone; made up mostly of
compact bone
Epiphysis: broad end of long bone; mostly
spongy bone
Metaphysis: growth area between diaphysis and
epiphysis
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Epiphyseal line = remnant of epiphyseal disk/plate
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Cartilage at the junction of the diaphysis and epiphyses
(growth plate)
Parts of a Long Bone
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Periosteum: fibrous covering over most of bone
Endosteum: membrane lining medullary cavity
Contains layer of osteoblasts (bone-forming
cells) &
osteoclasts (bone-destroying cells)
Medullary cavity: (yellow marrow) with fat and blood
cells
Nutrient Foramen = perforating canal allowing blood
vessels to enter and leave bone
Articular cartilage = pad of hyaline cartilage on the
epiphyses where long bones articulate or join
Microscopic Structure of Bone
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Matrix
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25% water, 25% collagen fibers, 50% mineral salts
Osteogenic cells in periosteum
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Develop into Osteoblasts (mature bone cell)
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Secrete collagen fibers
Build matrix and become trapped in lacunae
Osteoclasts are formed from monocytes
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Digest bone matrix for normal bone turnover
Compact Bone Structure
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Arranged in osteons (haversian systems)
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Central canal through center of osteon
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Cylinders running parallel to long axis of bone
Contains blood vessels, nerves, lymphatics
Concentric lamellae: layers of matrix
Lacunae:
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Contain osteocytes (bone cells)
Compact Bone Structure
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Canaliculi (“little canals”)
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Contain extensions of osteocytes
Permit flow of ECF between central canal and
lacunae
Compact bone is covered by periosteum
Perforating (Volkmann’s) canals
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Carry blood and lymphatic vessels and nerves from
periosteum
They supply central (Haversian) canals and also bone
marrow
Spongy Bone Structure
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Not arranged in osteons
Irregular latticework of trabeculae
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These contain lacunae with osteocytes and
canaliculi
Spaces between trabeculae may contain red
bone marrow
Spongy bone is lighter than compact bone,
so reduces weight of skeleton
Bone Formation
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Known as ossification
Timeline
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Initial bone development in embryo and fetus
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initial “skeleton” replaced by bone tissue beginning at 6
weeks of embryonic life
Growth of bone into adulthood
Remodeling: replacement of old bone
Repair if fractures occur
Bone Formation
Two different methods of ossification
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Intramembranous: bone forms in sheets
1.
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Few bones: flat bones of the skull, lower jawbone
(mandible), and part of clavicle
Endochondrial: forms hyaline cartilage then
develops into bone
2.
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All other bones form by this process
Intramembranous Ossification
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Four steps
1. Development of ossification center
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Mesenchyme cells  osteogenic osteoblasts
Osteoblasts secrete organic matrix
2.Calcification: cells become osteocytes
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In lacunae they extend cytoplasmic processes to each other
Deposit calcium & other mineral salts
3.Formation of trabeculae (spongy bone)
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Blood vessels grow in and red marrow is formed
4.Periosteum covering the bone forms
from mesenchyme
Endochondrial Ossification
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Six Steps
1. Formation of cartilage model of the “bone”
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As mesenchyme cells develop into chondroblasts
2. Growth of cartilage model
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Cartilage “bone” grows as chondroblasts secrete
cartilage matrix
Chondrocytes increase in size, matrix around them
calcifies
Chondrocytes die as they are cut off from nutrients,
leaving small spaces (lacunae)
Endochondrial Ossification
3. Primary ossification center
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Perichondrium sends nutrient artery inwards into
disintegrating cartilage
Osteogenic cells in perichondrium become osteoblasts
deposit bony matrix over remnants of calcified cartilage 
 spongy bone forms in center of the model
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As perichondrium starts to form bone, the membrane is
called periosteum
Endochondrial Ossification
4. Medullary (marrow) cavity
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Spongy bone in center of the model grows towards
ends of model
Octeoclasts break down some of new spongy bone
forming a cavity (marrow) through most of diaphysis
Most of the wall of the diaphysis is replaced by a collar
of compact bone
Endochondrial Ossification
5. Secondary ossification center
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Similar to step 3 of Intramembranous Ossification;
except that nutrient arteries enter ends (epiphyses) of
bones and osteoblasts deposit bony matrix 
spongy bone forms in epiphyses from center outwards
Occurs about time of birth
6. Articular cartilage and epiphyseal cartilage
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Ends of epiphyses becomes articular cartilage
Epiphyseal (growth) plate of cartilage remains between
epiphysis and diaphysis until bone growth ceases
Growth in Length
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Chondrocytes divide and grow more cartilage
on epiphyseal side of the epiphyseal plate
Chondrocytes on the diaphyseal side die and
are replaced by bone
Bone grows from diaphyseal side towards
epiphyseal side
Growth in length stops between 18-25 years
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Cartilage in epiphyseal plate is completely
replaced by bone (epiphyseal line)
Growth in Thickness
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As bones grow in length, they must
also grow in thickness (width)
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Perichondrial osteoblasts lay down
additional lamellae of compact bone
Simultaneously, osteoclasts in the
endosteum destroy interior bone to
increase width of the marrow
Remodeling and Repair
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Remodeling in response to use
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Resorption by osteoclasts and
Deposition by osteoblasts
Repair after a fracture
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Dead tissue removed
Chondroblasts  fibrocartilage 
spongy bone deposited by osteoblasts 
remodeled to compact bone
Types of Fractures
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Partial: incomplete break (crack)
Complete: bone broken into two or more
pieces
Closed (simple): not through skin
Open (compound): broken ends break skin
Green stick
• Fissured
• Comminuted
• Transverse
• Oblique
• Spiral
•
Types of Fractures
7-62
Copyright 2010, John Wiley & Sons, Inc.
Factors Affecting Growth
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Adequate minerals (Ca, P, Mg)
Vitamins A, C, D
Hormones
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Before puberty: hGH + insulin-like growth factors
Thyroid hormone and insulin also required
Sex hormones contribute to adolescent growth
spurt
Weight-bearing activity
• Deficiency of Vitamin A – retards bone development
• Deficiency of Vitamin C – results in fragile bones,
scurvy
• Deficiency of Vitamin D – rickets (children),
osteomalacia (adults)
• Insufficient Growth Hormone – dwarfism
• Excessive Growth Hormone – gigantism, acromegaly
• Insufficient Thyroid Hormone – delays bone growth
• Physical Stress – stimulates bone growth
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Calcium Homeostasis
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Blood levels of Ca2+ controlled
Negative feedback loops
Parathyroid hormone (PTH) increases
osteoclast activity + decreases loss of Ca2+ in
urine
Calcitonin decreases osteoclast activity
Negative Feedback
Exercise & Bone Tissue
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Bone strengthened in response to use
Bone reabsorbed during disuse; examples:
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During prolonged bed rest
Fracture with cast/immobilizer
Astronauts without gravity
Divisions of Skeletal System
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Two divisions: axial and appendicular
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Axial: bones around body axis
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Examples: skull bones, hyoid, ribs, sternum, vertebrae
Appendicular: bones of upper and lower limbs
plus shoulder and hip bones that connect them
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Examples: clavicle, humerus, radius and ulna, femur
Skull
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Eight Cranial bones
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Frontal, 2 parietal, 2 temporal, occipital, sphenoid,
and ethmoid
Fourteen Facial bones
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2 nasal, 2 maxilla, 2 zygomatic, 2 lacrimal
2 palatine, 2 inferior nasal conchae, 1 mandible,
1 vomer
Skull
Frontal (1)
• Forehead
• Frontal sinuses
• Supraorbital foramen
• Coronal suture
7-17
Skull
Parietal (2)
• Side
walls of cranium
• Roof of cranium
• Sagittal suture
7-18
Skull
Temporal (2)
• Squamosal
suture
• External acoustic meatus
• Mandibular fossa
• Mastoid process
• Styloid process
• Zygomatic process
7-19
Skull
Occipital (1)
• Back
of skull
• Foramen magnum
• Occipital condyles
• Lambdoidal suture
7-20
Skull
Sphenoid (1)
• Sella
turcica
• Sphenoidal sinuses
7-21
Skull
Ethmoid (1)
• Cribiform
plates
• Perpendicular plate
• Superior and middle
nasal conchae
• Ethmoidal sinuses
• Crista gallis
7-22
Facial Skeleton
Maxillary (2)
• Upper
jaw
• Alveolar processes
• Maxillary sinuses
• Palatine process
7-23
Facial Skeleton
Palatine (2)
• Posterior roof of mouth
7-24
Copyright 2010, John Wiley & Sons, Inc.
Facial Skeleton
Zygomatic (2)
• Prominences of cheeks
• Temporal process
7-25
Facial Skeleton
Lacrimal (2)
• Medial
walls of
orbits
Nasal (2)
• Bridge
of nose
7-26
Facial Skeleton
Vomer (1)
• Inferior
portion of
nasal septum
7-27
Facial Skeleton
Inferior Nasal
Conchae (2)
• Extend
from lateral
walls of nasal cavity
7-28
Facial Skeleton
Mandible (1)
• Lower
jaw
• Body
• Ramus
• Mandibular
condyle
• Coronoid process
• Alveolar process
• Mandibular
foramen
• Mental foramen
7-29
Unique Features of Skull
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Sutures: immovable joint between skull
bones
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Paranasal sinuses: cavities
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Coronal, sagittal, lambdoidal, squamous
Located in bones near nasal cavity
Fontanels: soft spot in fetal skull
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Allow deformation at birth
Calcify to form sutures
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hyoid
Vertebrae
Functions
 Encloses spinal cord
 Supports head
 Point of attachment for muscles of back, ribs
and pelvic girdle
Regions (from superior to inferior)
 7 cervical
 12 thoracic
 5 lumbar
 1 sacrum and 1 coccyx
Normal Curves in Column
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Four normal curves
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Cervical and lumbar curves are convex (bulge
anteriorly)
Thoracic and sacral curves are concave (bulge
posteriorly)
Curves increase strength, help in balance
and absorb shocks
Structure of Vertebra
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Body: disc-shaped anterior portion
Vertebral arch: posteriorly back from body
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With the body, creates a hole called vertebral foramen
Seven processes from this arch
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Transverse process extending laterally on each side
Spinous process extending dorsally
Two each of superior and inferior articular processes
that form joints with vertebrae
Vertebral
Column
• Rib facets
• Intervertebral discs
• Intervertebral foramina
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Cervical Area
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Cervical (C1-C7 from superior to inferior)
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C1: atlas
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Spinous process often bifid with transverse foramina
on transverse processes
Articulates with head, specialized to support head
Lacks body and spinous process
C2: axis
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Has body and spinous process
Dens (“tooth”) that creates a pivot for head rotation
Other Vertebrae
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Thoracic (T1-T12 )
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Lumbar (L1-L5)
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Largest and strongest; spinous processes short and
thick
Sacrum (S1-S5 fused into one unit)
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Larger than cervical
Have facets for articulations with ribs
Foundation for pelvic girdle
Contain sacral foramina for nerves and blood vessels
Coccyx: 4 coccygeal vertebrae fused into 1
Thorax
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Thoracic cage: sternum, costal cartilages,
ribs and bodies of T1-T12
Sternum: 3 portions fused by about age 25
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Manubrium, body, xiphoid process
True ribs #1-7: articulate with sternum by
costal cartilages
False ribs #8-12: articulate with coastal
cartilage of true ribs
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2 - Floating Ribs (no attachment)
Rib Structure
• Shaft
• Head – articulates
with vertebrae
• Tubercle
• Costal cartilage
7-40
Pectoral Girdle
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Function: attach bones of upper limbs to axial
skeleton
Clavicles and scapulas: bilateral
Clavicles
• Articulate with
manubrium
• Articulate with scapulae
(acromion process)
7-43
Scapula
• Spine
• Supraspinous fossa
• Infraspinous fossa
• Acromion process
• Coracoid process
• Glenoid cavity
7-44
Copyright 2010, John Wiley & Sons, Inc.
Upper Limb
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Humerus: arm bone
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Articulates with scapula (glenoid cavity)
Articulates with radius and ulna at elbow
Ulna: medial bone
Radius: lateral bone (thumb side)
Humerus
• Head
• Greater tubercle
• Lesser tubercle
• Anatomical neck
• Surgical neck
• Deltoid tuberosity
• Capitulum
• Trochlea
• Coronoid fossa
• Olecranon fossa
• Lateral epicondyle
• Medial epicondyle
7-46
Copyright 2010, John Wiley & Sons, Inc.
Radius
• Lateral forearm bone
• Head
• Radial tuberosity
• Styloid process
7-47
Ulna
• Medial forearm bone
• Trochlear notch
• Olecranon process
• Coronoid process
• Styloid process
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Wrist and Hand
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Carpals (wrist): 8 bones
Metacarpals: 5 bones of palm of hand
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Number 1-5 starting with thumb
Phalanges: 14 bones of fingers
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Each finger except thumb has proximal, middle
and distal phalanges; thumb lacks middle phalanx
Wrist and Hand
Carpals
• Trapezium
• Trapezoid
• Capitate
• Scaphoid
• Pisiform
• Triquetrum
• Hamate
• Lunate
7-49
Pelvic (Hip) Girdle
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Pelvic girdle includes two hip (coxal) bones
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Joined anteriorly at pubic symphysis
+ sacrum and coccyx
False (greater) pelvis: broad region superior
to pelvic brim; contains abdominal organs
True (lesser) pelvis: small region inferior to
pelvic brim; contains urinary bladder +
internal reproductive organs
Parts of Each Hip (Coxal) Bone
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3 separate bones fuse by age 23 to form a
hip bone
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Ilium: largest and most superior
Ischium: lower posterior part
Pubis: lower anterior part
Acetabulum - socket for head of femur
Lower Limb
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Femur: largest bone in the body
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Patella: kneecap in anterior of knee joint
Tibia: shin bone
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Articulates with hip proximally and with the tibia and
patella distally
Large medial, weight-bearing bone of leg
Fibula: longest, thinnest bone in body
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Lateral to tibia and smaller
Does not articulate with femur
Femur
• Head
• Fovea capitis
• Neck
• Greater trochanter
• Lesser trochanter
• Linea aspera
• Condyles (medial/lateral)
• Epicondyles (medial/lateral)
7-55
Patella
• Flat sesamoid bone
located in a tendon
7-56
Tibia
• Medial to fibula
• Condyles
• Tibial tuberosity
• Anterior crest
• Medial malleolus
7-57
Copyright 2010, John Wiley & Sons, Inc.
Fibula
• Lateral to tibia
• Head
• Lateral malleolus
• Does not bear any
body weight
Insert figure 7.54
7-58
Copyright 2010, John Wiley & Sons, Inc.
Ankle and Foot
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Tarsals (ankle) - 7 bones
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Large talus (ankle bone) and
Calcaneus (heel bone)
navicular
cuboid
lateral cuneiform
intermediate cuneiform
medial cuneiform
Ankle and Foot
Metatarsals (foot bones)
• Numbered 1 to 5 from medial to lateral
Phalanges (toe bones)
• Big toe has proximal and distal phalanges while others
have proximal, middle and distal phalanges.
7-59
Copyright 2010, John Wiley & Sons, Inc.
Male and Female Differences
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Males usually have heavier bones
Related to muscle size and strength
Female pelvis is wider and shallower than
male pelvis: allows for birth
Aging and Skeletal System
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Birth through adolescence: more bone
formed than lost
Young adults: gain and loss about equal
As levels of sex steroids decline with age:
bone reabsorption > bone formation
Bones become brittle and lose calcium
Life-Span Changes
• Decrease
in height at about age 30
• Osteoclasts outnumber osteoblasts
• Spongy bone weakens before compact bone
• Hip fractures common
• Bone loss rapid in menopausal women
• After age 70 bone loss between sexes is similar
• Vertebral compression fractures common
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Homeostatic Disorders
Sickle Cell Disease
Osteoporosis
Cleft Palate
Polydactyly