Chapter 7
Skeletal System
Bone Classification
• Long Bones
• Short Bones
• Flat Bones
• Irregular Bones
• Sesamoid (Round)
Bones
1
Skeletal System
• Functions
– Support
– Protection
• internal organs
– Movement facilitation
• Bones act as the levers
• Articulations as the fulcrums
• Muscles provide the force
2
Skeletal System
• Functions
– Mineral Storage
• calcium and phosphorous
– Storage of Blood Cell Producing Cells
• red bone marrow
– Storage of Energy
• lipids stored in yellow bone marrow are
important source of chemical energy
3
Bone Function
• Support, Movement & Protection
• gives shape to head, etc.
• supports body’s weight
• Inorganic Salt Storage
• protects lungs, etc.
• calcium
• bones and muscles interact
• phosphate
when limbs or body parts move
• magnesium
• Blood Cell Formation
• hematopoiesis
• red marrow
• sodium
• potassium
4
Cells and Histology of Bone
• Cartilage, Osseous and Dense CT
• Osseous Tissue (4 cell types)
– Osteoprogenitor
• Found throughout the bone
• Have mitotic potential
• May differentiate into osteoblast
5
Cells and Histology of Bone
• Osseous Tissue (4 cell types)
– Osteoblast
• No mitotic potential
• Found on the surface of the bone
• Secrete mineral salts and organic components for
bone formation
6
Cells and Histology of Bone
• Osseous Tissue (4 cell types)
– Osteocytes
• No mitotic potential
• Found within the bone
• Maintain daily cellular activities of bone tissue
– Osteoclast
• Found on the surface of bone
• Function in the re-absorption of bone
7
Parts of a Long Bone
• Epiphysis
• distal end
• proximal end
• Articular Cartilage
• Covers each
epiphysis
• Hyaline cartilage
• Diaphysis
• Shaft
• Metaphysis
• Area between
diaphysis and
epiphysis in mature
bone
8
Parts of a Long Bone
• Periosteum
• Contains nerves,
blood vessels, osteo
cells
• Attachment point for
ligaments and
tendons
• Medullary cavity
• contains yellow
marrow
• Endosteum
• lines the medullary
cavity
9
Parts of a Long Bone
• Spongy Bone
• Irregular lattice work
of bone-trabeculae
• Spaces filled with red
marrow
• produces RBCs
10
Parts of a Long Bone
• Compact Bone
• Tightly packed tissue
• Parts
• Concentric Lamellae
• Concentric circles of
tightly packed tissue
• Volkmann’s Canals
• Penetrate compact
bone
• Allow blood vessels
and nerves into
medullary cavity and
other Haversian
Canals
11
Parts of a Long Bone
• Compact Bone
• Haversian Canals
• Run longitudinally
through the compact
bone
• Concentric lamellae
surround the canals
• Lacunae
• Open spaces between the
concentric lamellae that
contain osteocytes
• Look like “little lakes”
12
Parts of a Long Bone
• Compact Bone
– Canaliculi
• Tiny canals that radiate
away from the lacunae
– Osteon (Haversian System)
• Central canal,
surrounding lamellae,
lacunae, osteocytes and
canaliculi
13
Bone Development
Intramembranous Ossification
• bones originate within sheetlike layers of connective
tissues
• broad, flat bones
• skull bones (except mandible)
• intramembranous bones
Endochondral Ossification
• bones begin as hyaline cartilage
• form models for future bones
• most bones of the skeleton
• endochondral bones
14
Endochondral Ossification
• hyaline cartilage model
• epiphyseal plate
• primary ossification center
• osteoblasts vs. osteoclasts
• secondary ossification centers
15
Endochondral Ossification
• Hyaline cartilage
model
• “bone” created by
chondroblast
• Actual ossification of
this “bone” starts 6-7
weeks after
conception
16
Endochondral Ossification
• Interstitial and
Oppositional Growth
• Chondrocytes burst
and trigger
calcification
• Capillaries and bone
cells invade dying
cartilage
• Bone starts to calcify
17
Endochondral Ossification
• Primary Ossification
Center
• Blood vessels in midregion produce
ossification center
• Osteoblast form
spongy bone in the
area of calcified
cartilage, this causes
the center to enlarge
• Spongy bone is
destroyed by
osteoclast-forms
medullary cavity
18
Endochondral Ossification
• Secondary Ossification
Centers
• When blood vessels enter
the epiphysis
• Spongy bone created here
will stay
• Epiphyseal plate
• Layer of hyaline
cartilage between the 2
areas of growth
• Stays until you reach
maturity
19
Endochondral Ossification
• Remnants of hyaline
cartilage on the
epiphysis becomes
articulating cartilage
20
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
21
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
22
Homeostasis of Bone Tissue
•Bone Re-absorption – action of osteoclasts and parathyroid
hormone
•Bone Deposition – action of osteoblasts and calcitonin
23
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
24
Superficial Bone Anatomy
• Process
• bony prominence “bump”
• Condyle
• rounded or knuckle like process
• Tubercle
• small process
• Tuberosity
• large process (tibial tuberosity)
• Trochanter
• huge process (located on the proximal end of the femur)
25
Superficial Bone Anatomy
• Crest
• narrow ridge of bone
• Spine
• sharp slender process (holes and/or depressions)
• Fissure
• narrow slit through which blood vessels or nerves
pass
• Foramen
• opening through which blood vessels and nerves
pass
26
Superficial Bone Anatomy
• Meatus
• tubelike passageway running within a bone
• Sulcus or groove
• furrow that accommodates a soft structure such as
blood vessels, nerves or tendons
• Fossa
• depression in or on the surface of a bone
27
Skeletal Organization
Axial Skeleton
• head
• neck
• trunk
Appendicular Skeleton
• upper limbs
• lower limbs
• pectoral girdle
• pelvic girdle
28
Skeletal Organization
29
Skeletal Organization
• Hyoid Bone
– Supports tongue
– Attachment point
for muscles that
move tongue
30
Cranium
Frontal (1)
• Forehead
• Roof of nasal cavity
• Roofs of optical orbits
• Frontal sinuses
• Supraorbital foramen
•Blood vessels and
nerve
• Coronal suture
• Develops in two parts
•Completely fused by
age 5 or 6
31
Cranium
Parietal (2)
• Side walls of cranium
• Roof of cranium
• sagittal suture
•Fuses two parietal
bones together
•Coronal suture
•Fuses parietal
bones to frontal
bone
32
Cranium
Occipital (1)
• back of skull
• base of cranium
• foramen magnum
•Inferior part of
brain stem
connects with
spinal cord
• occipital condyles
•Either side of
foramen magnum
• lambdoid suture
•Fuses parietal
bones with
occipital bone
33
Cranium
Temporal (2)
• side walls of cranium
• floor of cranium
• floors and sides of orbits
• squamous suture
•Fuses parietal with
temporal
• external acoustic meatus
•Leads to inner ear
• mandibular fossa
•Where mandible meets
temporal bone
• mastoid process
•Neck muscle attachment
• styloid process
•Tongue and pharynx
attachment
• zygomatic process
34
Cranium
Sphenoid (1)
• base of cranium
• sides of skull
• floors and sides of orbits
• sella turcica
•Indentation along
midline within cranial
cavity
•Contains pituitary gland
• sphenoidal sinuses
35
Cranium
Ethmoid (1)
• roof and walls of nasal cavity
• floor of cranium
• wall of orbits
• cribriform plates
•Join two parts of ethmoid on
either side of nasal cavity
• perpendicular plate
•Forms most of nasal septum
• superior and middle nasal
conchae
•Support mucous membranes of
nasal cavity
• ethmoidal sinuses
• crista galli
•Projects upward into cranial
cavity
•Attaches brain membranes
36
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
37
Facial Skeleton
38
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
39
Facial Skeleton
Zygomatic (2)
• prominences of cheeks
• lateral walls of orbits
• floors of orbits
• temporal process
•Extends posteriorly
to join zygomatic
process of temporal
bone
40
Facial Skeleton
Lacrimal (2)
• medial walls of orbits
• groove from orbit to nasal
cavity
Nasal (2)
• bridge of nose
41
Facial Skeleton
Vomer (1)
• inferior portion of nasal
septum
42
Facial Skeleton
Inferior Nasal Conchae (2)
• extend from lateral walls of
nasal cavity
43
Facial Skeleton
Mandible (1)
• Lower jaw
• Body
•Horseshoe shaped
portion
• Ramus
•Flat, upward
projections
• Mandibular condyle
•Fits into mandibular
fossa
• Coronoid process
•Chewing muscle
attachment
• alveolar process
• mandibular foramen
• mental foramen
44
Infantile Skull
Fontanels – fibrous membranes
45
Vertebral Column
• cervical vertebrae (7)
• thoracic vertebrae (12)
• lumbar vertebrae (5)
• sacrum
• coccyx
46
Vertebral Column
• cervical curvature
•Smallest vertebrae
•Most dense bone tissue
• thoracic curvature
• lumbar curvature
• sacral curvature
• rib facets
• vertebra prominens
•Long spinous process on 7th
vertebra
• intervertebral discs
• intervertebral foramina
47
Cervical Vertebrae
• Atlas – 1st; supports head
• Axis – 2nd; dens pivots to
turn head
• transverse foramina
•Blood vessels leading to
the brain pass through
• bifid spinous processes
•Muscle attachment
• vertebral prominens
• useful landmark
48
Thoracic Vertebrae
• long spinous processes
• rib facets
49
Lumbar Vertebrae
• large bodies
•Support weight
• thick, short spinous
processes
•Nearly horizontal
50
Sacrum
• five fused vertebrae
•Fuse between age
15 and 30
• median sacral crest
•Fused spinous
processes
• posterior sacral
foramina
• posterior wall of
pelvic cavity
• sacral promontory
•Body of the 1st
sacral vertebra
51
Coccyx
• tailbone
• four fused vertebrae
•Fuse by age 25
52
Thoracic Cage
• Ribs
• Sternum
• Thoracic vertebrae
• Costal cartilages
• Supports shoulder
(pectoral) girdle and upper
limbs
• Protects viscera
• Role in breathing
53
Ribs
• True ribs (7)
•Attach to sternum by
costal cartilage
• False ribs (5)
•Costal cartilage does
not reach sternum
•Top 3 join cartilage of
7th True rib
•Bottom 2 don’t attach
at all
• floating (2)
54
Rib Structure
• Shaft
• Head
•posterior end
•articulates with
vertebrae
• Tubercle
•articulates with
vertebrae
• Costal cartilage
•hyaline cartilage
55
Sternum
• Manubrium
• Body
• Xiphoid process
56
Appendicular Skeleton
• Comprised of 2 parts
– Pectoral girdle and upper extremity
• Shoulders and arms
– Pelvic girdle and lower extremity
• Hips and legs
57
Pectoral Girdle
• attach bones of the
upper extremities to
the axial skeleton
•Shoulder Girdle
•clavicles anterior
• scapulae posterior
• supports upper limbs
58
Clavicles
•Long slender bone with
double curvature
•Sternal end
•Rounded end
•articulates with
manubrium
•Acromial end
•Broad flat end
• articulates with scapula
(acromion process)
59
Scapulae
•Triangular flat bone
•Posterior part of the thorax
•Between the 2nd and the 7th
rib
•Medial border
•5 centimeters from the
vertebral column
• spine
•Runs diagonally across body
• supraspinous fossa
• infraspinous fossa
60
Scapulae
• acromion process
• part of the spine that
expands past the body
• coracoid process
• located at the lateral
end of the superior
ridge
• glenoid cavity
• fossa inferior to the
acromian process
• Articulates with the
head of the humerus to
make a ball and socket
joint
61
Scapulae
62
Upper Limb
• Consists of 60 bones
• Each side contains 30 bones
–
–
–
–
–
–
1 humerus
1 radius
1 ulna
8 carpals
5 metacarpals
14 phalanges
63
Upper Limb
• Humerus
• Articulates
proximally with the
scapula and distally
with both the radius
and the ulna
• Largest bone in the
upper extremity
64
Humerus
• Head
•rounded proximal
end, articulates with
glenoid cavity
•Anatomical neck
•Slight groove below
head
•Epiphyseal plate
• Greater tubercle
•large lateral
process below the
anatomical neck
65
Humerus
• lesser tubercle
• anterior side
• Intertubercular groove
• Surgical neck
• Constricted portion
inferior to tubercles
• Fractures likely here
• Deltoid tuberosity
• Slight bump on the
anterior surface
• Insertion point for
deltoid muscle
66
Humerus
• Capitulum
• rounded knob
• articulates with head
of radius
• Trochlea
• Pulley-like surface
that articulates with
ulna
• Coronoid fossa
• Receives part of the
ulna when elbow is
flexed
• On anterior, distal
surface
67
Humerus
• Olecranon fossa
• posterior side
• receives olecranon
process of ulna when
elbow is extended
• Medial and Lateral
Epicondyles
• Found on either side
of distal end of
humerus
• Serve as attachments
of most forearm
muscles
68
Humerus
• Ulnar nerve
• Lies over the
posterior surface of
the medial epicondyle
• Can be rolled
between the finger
and the medial
epicondyle
69
Ulna
• medial forearm bone
• trochlear notch
•Curved area
between olecranon
and coronoid
process
•Articulates with
trochlea of
humerus
•Allows for flexion
and extension of
elbow
70
Ulna
• Olecranon process
• posterior projection
• proximal end
• Coronoid process
• anterior projectionlateral
• Styloid process
• posterior side of the
head of the ulna
• Head
• distal end of the ulna
71
Radius
• lateral forearm bone
• Head
•Disc like structure that
articulates with
capitulum of humerus
and radial notch of ulna
• Radial tuberosity
•Proximal end inferior
to head
•Anterior surface
• Styloid process
•Distal end
•Articulates with
scaphoid bone
72
Wrist and Hand
• Carpals (16)
• trapezium
• trapezoid
• capitate
• scaphoid
• pisiform
• triquetrum
• hamate
• lunate
• Metacarpals (10)
• Phalanges (28)
• proximal phalanx
• middle phalanx
• distal phalanx
73
Pelvic Girdle
•Provide a strong support for
the lower extremities
• Coxae (2)
•Each is 3 bones fused
together
•Os coxa (1)
•Sacrum
• supports trunk of body
• protects viscera
74
Coxae
• hip bones
•Acetabulum
•lateral fossa of the
os coxa where 3
pelvic bones merge
• Ilium
•Superior to other 2
portions
•iliac crest
•superior border
•serves as insertion
point for
abdominal wall
muscles
75
Coxae
• Ilium
• Iliac fossa
• internal surface seen
from the medial side
• gives the pelvis a bowl
shape appearance
• Greater sciatic notch
• Inferior to iliac crest
• Posterior to
acetabulum
• Allows for major
nerves and blood
vessels to travel from
sacrum to legs
76
Coxae
• Ischium
• inferior, posterior
portion of the coxal
bone
•
ischial spines
• Posterior, superior
to ischial tuberosity
• lesser sciatic notch
• Inferior to ischial
spine
• ischial tuberosity
• tuberosity that we
sit on
77
Coxae
• Pubis
• orbturator foramen
• between ischium,
pubic bone and
acetabulum
•
symphysis pubis
• Joins with other
pubic bone at
symphysis pubis
• Hormone, relaxin,
is released during
child birth that
allows greater
flexibility of the
fibrocartilage
78
Greater and Lesser Pelvis
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
79
Male and Female Pelvis
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
80
Lower Limb
• Femur (2)
• Patella (2)
• Tibia (2)
• Fibula (2)
• Tarsals (14)
• Metatarsals
(10)
• Phalanges
(14)
81
Femur
• Longest &
heaviest bone of
body
•Body of femur
angles toward the
midline
•makes knees
closer than hips
•Degree is
greater in
females
82
Femur
• Head
• rounded end
• articulates with
acetabulum
• Neck
• Distal to the head
• Elderly people break this
area often
•
Greater trochanter &
Lesser trochanter
• large processes below the
neck
• serve attachment points
for some thigh and
buttock muscles
83
Femur
• Shaft
• diaphysis
•
Linea aspera
• Posterior side of shaft
• Serves as insertion point
for adductor muscles of
the leg
• Medial & Lateral
epicondyles
• Distal end of femur
• Articulates with proximal
end of tibia
84
Femur
• Intercondylar fossa
•
important area for the
ligaments in the knee
• Patellar surface
• distal anterior surface
between the condyles that
forms a gliding joint with
the patella
85
Patella
• kneecap
•Inferior end is
called the Apex
• anterior surface of
knee
• flat sesamoid bone
located in a tendon
86
Tibia
• shin bone
•Large, medial, weight
bearing bone of the lower
extremity
•Lateral & Medial
Condyles
•Articulate with
epicondyles of femur
•Inferior surface of
the lateral condyle
articulates with the
fibula
87
Tibia
• Tibial tuberosity
• Anterior surface of
the tibia
• Surface serves as
attachment point for
the patellar ligaments
and tendons
• anterior crest
• Extends downward
from tibial tuberosity
88
Tibia
• Intercondylar Eminence
• Upward projection
between the condyles
of the tibia
• Cruciate ligaments
attach here
• Medial malleolus
• Medial projection on
the distal end of the
tibia
• Provides medial
supports to the hinge
joint of your ankle
89
Fibula
• Lateral to tibia
• Non weight-bearing
• Long, slender
• Head
•proximal end
•more rounded
• Lateral malleolus
•Distal end
•articulates with the
tibia and talus
•Lateral support to
the ankle
•Longer pointier end
90
Ankle and Foot
• Tarsals (14)
• Calcaneus
•Largest and
strongest tarsal
•Supports body
weight
•Serves as lever
attachment for
gastrocnemius
91
Ankle and Foot
• Talus
• Uppermost tarsal
• Only bone that
articulates with
the tibia and fibula
• Initially bares all
body weight, then
transfers half to
the calcaneus and
half to the other
tarsals
92
Ankle and Foot
• Navicular
• just anterior to the talus
•
cuboid
• Lateral side of the foot
• Articulates with
calcaneus, the 4th and
5th metatarsal
lateral cuneiform
• intermediate
cuneiform
• medial cuneiform
•
• Each cuneiform that
articulates with the
corresponding
metatarsal
93
Ankle and Foot
• Metatarsals (10)
• numbered from the
medial to the lateral
side
• Phalanges (28)
• proximal
• middle
• distal
94
Life-Span Changes
• decrease in height at about age 30
• calcium levels fall
• bones become brittle
• osteoclasts outnumber osteoblasts
• spongy bone weakens before compact bone
• bone loss rapid in menopausal women
• hip fractures common
• vertebral compression fractures common
95
Clinical Application
Types of Fractures
• green stick
• fissured
• comminuted
• transverse
• oblique
• spiral
96
Clinical Application: Fractures
• Impacted
• one fragment is firmly driven into the other
• Displaced
• anatomical alignment is NOT preserved
• Non-displaced
• anatomical alignment is preserved
• Stress
• partial fracture resulting in bones inability to
withstand forces
• About 25% involve distal end of the fibula
97
Clinical Application: Fractures
• Pathologic
• caused by weakening of the bone due to a disease
• Pott’s
• fracture of the distal end of the fibula with serious
injury to the distal tibial articulation
• Severe eversion sprain may lead to this
• Colle’s
• fracture at the distal end of the radius in which the
distal end is displaced posteriorly
• Occurs frequently when you try to stop yourself
from falling
98
Clinical Application: Fracture
Repair
• Fracture breaks blood
vessels found in the
Haversian system
• Blood clot forms at the
site of the break within 6
to 8 hours (fracture
hematoma)
• Fracture hematoma
• serves as the focus for
cellular invasion
99
Clinical Application: Fracture
Repair
• Callus forms
• New bone tissue
developed around the
fracture
• Site of osteoblast
activity
100
Clinical Application: Fracture
Repair
• Remodeling
• Dead bone is
absorbed by
osteoclast
• Compact bone
replaces spongy bone
in the fractured area
101
Clinical Application: Disorders
• Osteoporosis
• Age related disease
characterized by
decreased bone mass
an increased chance
of fractures
• Decreased levels of
estrogen (sex
hormones that
stimulate osteoblast)
QuickTime™ and a
decompressor
are needed to see this picture.
102
Clinical Application: Disorders
• Osteoporosis
• White women more than men and people of color
• Other factors linked to osteoporosis
• Body build
• short people have less bone mass
• Weight
• thin people have less adipose, which stores estrogen
• Smokers• low estrogen levels
• Calcium deficiency and mal-absorption
• Vitamin D deficiency
• Certain drugs• alcohol, cortisone, etc.
• Premature menopause
103
Clinical Application: Disorders
• Osteoporosis Prevention
– Exercise
• muscle action stimulates blood flow to bone
tissue
– Estrogen pills• for post menopause women
– Calcium supplements/ vitamins
– Prescription anabolic steroids• increase hormone levels
– Sodium Fluoride stimulates oteoblast
104
Clinical Application: Disorders
• Osteogenic Sarcoma
• Malignant bone tumor that affects osteoblast
• People between ages of 10-25
• Left untreated it will metasticize and lead to
death
• Treatment includes chemotherapy following
amputation of affected area
105
Clinical Application: Disorders
• Rickets
– Vitamin D deficiency in children
– Body can’t transport Ca+2 and P-3 from GI tract to
blood
– Osteoblasts in diaphysis don’t calcify causing bones
to stay soft
– Weight of body causes the legs to bow
– Cure and prevention
• Dietary- add vitamin D, calcium and phosphorus in large
amounts
• Exposing the skin to ultraviolet rays of light
106