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THE SKELETAL SYSTEM
1
BONE FUNCTION
• Support
• gives shape to head, etc.
• supports body’s weight
•Leverage
• articulation
•Bones and
muscles interact
• Inorganic Salt Storage
• calcium
• phosphate
• magnesium
• sodium
• potassium
• Blood Cell Formation
• hematopoiesis
• red marrow
• Protection
• for major organslungs, etc
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STRUCTURE: OSSEOUS TISSUE
•Connective tissue
•Specialized cells
•Extracellular fibers
•Ground substance
•Calcium phosphates are 2/3 of bone weight
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CLASSIFICATION SYSTEM
Bone Classification
• Long Bones- longer than wide
•Femur pg 111 (black book)
•Diaphysis – central shaft
•Marrow cavity
•Epiphysies –ends
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CLASSIFICATION SYSTEM, CON’T
•Short Bones
•Equal in dimensions
•Ex: carpals/tarsals
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CLASSIFICATION SYSTEM, CON’T
•Flat Bones
•Thin and broad
•Scapula
•these bones protect the internal organs and include the
skull (cranium), ribs, scapula (shoulder blade), sternum
(breast bone) and the pelvic girdle.
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CLASSIFICATION SYSTEM, CON’T
•Irregular Bones
•vertebrae
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CLASSIFICATION, CON’T
•Two types of bone tissue
•compact/dense
•Spongy - spaces
•Outer surfaces of bone:
•Periostium – outside layer
•Where tendons and ligaments
attach
•Endosteum – lines the marrow
cavity
•Active during repair or
remodeling, or normal growth
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PARTS OF A LONG BONE
• epiphysis
• distal
• proximal
• diaphysis
• compact bone
• spongy bone
• articular cartilage
• periosteum
• endosteum
• medullary cavity
• trabeculae
• marrow
• red
• yellow
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MICROSCOPIC STRUCTURE
OF COMPACT AND SPONGY BONE
•Histology:
•Osteocytes- bone cells
•Lacunae –
•pockets in spongy
bone
•Found between
lamellae
•Lamellae
•Calcified matrix
•Canaliculi
•Channels radiating
through the matrix
•Link to blood vessels
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MICROSCOPIC STRUCTURE OF COMPACT BONE
• osteon
•Functional unit of compact bone
•Aka Haversian system (pg 112 in black book)
•central canal
•Contains blood vessels surrounded by osteocytes
•perforating canal
•Contains linking blood vessels
•Found where bone is stressed
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MICROSCOPIC FEATURES OF SPONGY BONE
•Trabeculae
•Lamelle with no osteons
•It is rods or plates
•Found where there is not
much stress
•Cells Found in Bone
•Osteocytes –
•mature bone cells
•Osteoclasts –
•giant cells that regulate
Ca and phosphates in
fluids.
•Break down bone cells
•Osteoblasts – precursor
cells
Marrow Cavity (Osteoclasts)13
OSTEON
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BONE DEVELOPMENT
Endochondral Ossification
• most bones of the skeleton
•bones begin as hyaline cartilage
•form models for future bones
•Begins from center of shaft as early as 6 wks after fertilization
•Proceeds to both ends
•Epiphyseal plate: cartilage that separates shaft from end
•Shaft side – bond keeps advancing
•End side – keeps producing cartilage
•Hormones during teens speed process up
•Epiphysial line – what is left when growth is finished
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ENDOCHONDRAL OSSIFICATION
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GROWTH AT THE EPIPHYSEAL PLATE
First layer of cells
• closest to the end of
epiphysis
• resting cells
• anchors epiphyseal
plate to epiphysis
Second layer of cells
• many rows of
young cells
• undergoing mitosis
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GROWTH AT THE EPIPHYSEAL PLATE
Third layer of cells
• older cells
• left behind when new
cells appear
• cells enlarging and
becoming calcified
Fourth layer of cells
• thin
• dead cells
• calcified
extracellular matrix
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FACTORS AFFECTING BONE DEVELOPMENT,
GROWTH, AND REPAIR
• Deficiency of Vitamin A – retards bone
development
• Deficiency of Vitamin C – results in fragile
bones
• Deficiency of Vitamin D – rickets, osteomalacia
• Insufficient Growth Hormone – dwarfism
• Excessive Growth Hormone – gigantism,
acromegaly
• Insufficient Thyroid Hormone – delays bone
growth
• Sex Hormones – promote bone formation;
stimulate ossification of epiphyseal plates
• Physical Stress – stimulates bone growth
•Lack of stress causes fast bone loss (3 weeks
= 1/3 bone loss
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HOMEOSTASIS OF BONE TISSUE
•Adults – Bone is constantly breaking down and building up 18% of protein and mineral is replaced yearly
•Add calcium to body fluids: parathyroid hormone and
calcitriol work together
•Take calcium out of fluids and into bone: – action of calcitonin
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HOMEOSTASIS OF BONE TISSUE, CON’T
•Calcium: must abundant mineral in body – bones store it
•Average human contains 1-2 kg (2.2 – 4.4 lb) of Ca
•99% in bones
•30 % too much in fluids causes muscles & neurons to be
unresponsive
•35% too much in fluids causes: muscle and neurons to
convolse
•50% reduction in fluids may cause death
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INJURY AND REPAIR
•Fracture: cracks and
Types of Fractures
breaks in bone
•Classified by external
appearance Pg. 117 black
book
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FRACTURES
Open or closed (simple) fractures
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INJURY AND REPAIR
•Sequence of Repair
•1st: massive blood clot called a fracture hematoma occurs
•2nd Internal and external callus is formed
•3rd: external callus replaced by bone Old dead bone has
been dissolved
•4th Swelling marks new bone. Eventually remodels
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AGING AND THE SKELETAL SYSTEM
• decrease in height at about age 30
• calcium levels fall – NATURALLY: Osteopenia
• bones become brittle
• osteoclasts outnumber osteoblasts
• spongy bone weakens before compact bone
• bone loss rapid in menopausal women- 8% per decade.
Men 3% per decade as they age
• hip fractures common
• vertebral compression fractures common
Osteoporosis
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JOINTS

Rigid elements of the skeleton meet at joints or
articulations

Greek root “arthro” means joint

Articulations can be:
 Bone
to bone
 Bone
to cartilage
 Teeth
in bony sockets
CLASSIFICATIONS OF JOINTS


Joints can be classified by function or structure (in
this class we will only do the functional
classifications)
Functional classification – based on amount of
movement
 Synarthroses – immovable – common in axial
skeleton
 Amphiarthroses – slightly movable – common in
axial skeleton
 Diarthroses – freely movable – common in
appendicular skeleton
SYNARTHROSIS - IMMOVABLE

Includes
 Suture:
joint site
 Tooth
to socket
 Epiphysial plates
 Coronal suture
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AMPHIARTHROSIS – SLIGHTLY MOVABLE
Ex: between tibia
and fibula
 Symphysis: between
two pelvic bones

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SYMPHYSES

Hyaline cartilage – also present as
articular cartilage
Figure 9.2c
DIARTHROSIS -= FREELY MOVABLE
 Synovial joints –
 Usually

found at the end of the long bones
No bone touching bone
 Encapsulated
by cartilages
 Cushioned by synovial fluid
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SYNOVIAL JOINTS
Most movable type of joint
 All are diarthroses
 Each contains a fluid-filled joint cavity
 Most are “simple” and have just two articulating
surfaces
 Some are “compound” with more than two
articulating surfaces


Examples include the elbow (humerus, radius and
ulna) and knee (femur, tibia, fibula, patella) joints
A TYPICAL SYNOVIAL JOINT
Figure 9.3a
DIARTHROSIS, CONT

Kinds of movement
 Hinge
– elbow, knee angle
 Pivot – atlas and axis rotates
the head
 Saddle joints – at base of
thumbs (twiddling)
 Ball and socket – shoulder
and hip joints
 gliding – ends of clavicle,
between carples, at some
vertebrae
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Pivot joint
Hinge joint
Gliding joint
Ball and socket
Saddle joint
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Shoulder Joint
• Ball and socket joint synovial and diarthrotic
• Glenohumeral joint most movable joint in
the body
• Shallow glenoid fossa very easily dislocated
• Articular cartilage hyaline cartilage at the
ends of articulating
bones
Knee Joint
•
•
•
•
The largest and most complex joint
Synovial and diarthrotic
Primarily acts as a hinge joint
Two fibrocartilage menisci occur within the
joint cavity (absorb stress)
SAGITTAL SECTION OF KNEE JOINT
Figure 9.12a
SUPERIOR VIEW OF KNEE JOINT
Figure 9.12b
ANTERIOR VIEW OF KNEE
Figure 9.12c
KNEE JOINT

Extracapsular Ligaments
 Become
 Provide
taut when knee is extended
support of sides of the knee
 Extracapsular
 Fibular
 Tibial
ligaments:
(lateral) collateral ligament
(medial) collateral ligament
ANTERIOR VIEW OF KNEE
ANTERIOR VIEW OF FLEXED KNEE
Figure 9.12e
KNEE JOINT

Cruciate Ligaments

Prevent undesirable
movements at the
knee joint
Figure 9.13a
Ligaments and Tendons
Ligaments – attach bone to bone
Tendons – bone to muscle
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SKELETAL ORGANIZATION
Axial Skeleton
• head
• neck
• trunk
Appendicular Skeleton
• upper limbs
• lower limbs
• pectoral girdle
• pelvic girdle
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SKELETAL ORGANIZATION
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CRANIUM
Frontal (1)
• forehead
• roof of nasal cavity
• roofs of orbits
• frontal sinuses
• supraorbital foramen
• coronal suture
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CRANIUM
Parietal (2)
• side walls of cranium
• roof of cranium
• sagittal suture
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CRANIUM
Occipital (1)
• back of skull
• base of cranium
• foramen magnum
• occipital condyles
• lambdoid suture
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CRANIUM
Temporal (2)
• side walls of cranium
• floor of cranium
• floors and sides of orbits
• squamous suture
• external acoustic meatus
• mandibular fossa
• mastoid process
• styloid process
• zygomatic process
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CRANIUM
Sphenoid (1)
• base of cranium
• sides of skull
• floors and sides of orbits
• sella turcica
• sphenoidal sinuses
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CRANIUM
Ethmoid (1)
• roof and walls of nasal cavity
• floor of cranium
• wall of orbits
• cribiform plates
• perpendicular plate
• superior and middle nasal conchae
• ethmoidal sinuses
• crista galli
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FACIAL SKELETON
Maxillary (2)
• upper jaw
• anterior roof
of mouth
• floors of
orbits
• sides of nasal
cavity
• floors of
nasal cavity
• alveolar
processes
• maxillary
sinuses
• palatine
process
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FACIAL SKELETON
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FACIAL SKELETON
Palatine (2)
• L shaped bones located
behind the maxillae
• posterior section of hard
palate
• floor of nasal cavity
• lateral walls of nasal cavity
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FACIAL SKELETON
Zygomatic (2)
• prominences of cheeks
• lateral walls of orbits
• floors of orbits
• temporal process
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FACIAL SKELETON
Lacrimal (2)
• medial walls of orbits
• groove from orbit to nasal
cavity
Nasal (2)
• bridge of nose
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FACIAL SKELETON
Vomer (1)
• inferior portion of nasal
septum
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FACIAL SKELETON
Inferior Nasal Conchae (2)
• extend from lateral walls of
nasal cavity
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FACIAL SKELETON
Mandible (1)
• lower jaw
• body
• ramus
• mandibular condyle
• coronoid process
• alveolar process
• mandibular foramen
• mental foramen
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INFANTILE SKULL
Fontanels – fibrous membranes
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VERTEBRAL COLUMN
• cervical vertebrae (7)
• thoracic vertebrae (12)
• lumbar vertebrae (5)
• sacrum
• coccyx
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VERTEBRAL COLUMN
• cervical curvature
• thoracic curvature
• lumbar curvature
• sacral curvature
• rib facets
• vertebra prominens
• intervertebral discs
• intervertebral foramina
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CERVICAL VERTEBRAE
• Atlas – 1st; supports head
• Axis – 2nd; dens pivots to
turn head
• transverse foramina
• bifid spinous processes
• vertebral prominens –
useful landmark
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THORACIC VERTEBRAE
• long spinous processes
• rib facets
67
LUMBAR VERTEBRAE
• large bodies
• thick, short spinous
processes
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SACRUM
• five fused
vertebrae
• median sacral
crest
• posterior sacral
foramina
• posterior wall of
pelvic cavity
• sacral promontory
69
COCCYX
• tailbone
• four fused vertebrae
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THORACIC CAGE
• Ribs
• Sternum
• Thoracic vertebrae
• Costal cartilages
• Supports shoulder girdle
and upper limbs
• Protects viscera
• Role in breathing
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RIBS
• True ribs (7)
• False ribs (5)
• floating (2)
72
RIB STRUCTURE
• Shaft
• Head – posterior end;
articulates with vertebrae
• Tubercle – articulates with
vertebrae
• Costal cartilage – hyaline
cartilage
73
STERNUM
• Manubrium
• Body
• Xiphoid process
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PECTORAL GIRDLE
• shoulder girdle
• clavicles
• scapulae
• supports upper limbs
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CLAVICLES
• articulate with manubrium
• articulate with scapulae
(acromion process)
76
SCAPULAE
• spine
• supraspinous fossa
• infraspinous fossa
• acromion process
• coracoid process
• glenoid cavity
77
UPPER LIMB
• Humerus
• Radius
• Ulna
• Carpals
• Metacarpals
• Phalanges
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HUMERUS
• head
• greater tubercle
• lesser tubercle
• anatomical neck
• surgical neck
• deltoid tuberosity
• capitulum
• trochlea
• coronoid fossa
• olecranon fossa
79
RADIUS
• lateral forearm bone
• head
• radial tuberosity
• styloid process
80
ULNA
• medial forearm bone
• trochlear notch
• olecranon process
• coronoid process
• styloid process
81
WRIST AND HAND
• Carpals (16)
• trapezium
• trapezoid
• capitate
• scaphoid
• pisiform
• triquetrum
• hamate
• lunate
• Metacarpals (10)
• Phalanges (28)
• proximal phalanx
• middle phalanx
• distal phalanx
82
PELVIC GIRDLE
• Coxae (2)
• supports trunk of body
• protects viscera
83
COXAE
• hip bones
•acetabulum
• ilium
• iliac crest
• iliac spines
• greater sciatic notch
• ischium
• ischial spines
• lesser sciatic notch
• ischial tuberosity
• pubis
• obturator foramen
• symphysis pubis
• pubic arch
84
GREATER AND LESSER PELVES
Greater Pelvis
• lumbar vertebrae
posteriorly
• iliac bones laterally
• abdominal wall
anteriorly
Lesser Pelvis
• sacrum and coccyx
posteriorly
• lower ilium, ischium, and
pubis bones laterally and
anteriorly
85
MALE AND FEMALE PELVES
Female
• iliac bones more flared
• broader hips
• pubic arch angle greater
• more distance between
ischial spines and ischial
tuberosities
• sacral curvature shorter and
flatter
• lighter bones
86
LOWER LIMB
• Femur
• Patella
• Tibia
• Fibula
• Tarsals
• Metatarsals
• Phalanges
87
FEMUR
• longest bone of body
• head
• fovea capitis
• neck
• greater trochanter
• lesser trochanter
• linea aspera
• condyles
• epicondyles
88
PATELLA
• kneecap
• anterior surface of knee
• flat sesamoid bone located
in a tendon
89
TIBIA
• shin bone
• medial to fibula
• condyles
• tibial tuberosity
• anterior crest
• medial malleolus
90
FIBULA
• lateral to tibia
• long, slender
• head
• lateral malleolus
• does not bear any
body weight
91
ANKLE AND FOOT
• Tarsals (14)
• calcaneus
• talus
• navicular
• cuboid
• lateral cuneiform
• intermediate cuneiform
• medial cuneiform
• Metatarsals (10)
• Phalanges (28)
• proximal
• middle
• distal
92
ANKLE AND FOOT
93
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