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5
The Skeletal System
PowerPoint® Lecture Slide Presentation by Jerry L. Cook, Sam Houston University
ESSENTIALS
OF HUMAN
ANATOMY
& PHYSIOLOGY
EIGHTH EDITION
ELAINE N. MARIEB
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
The Skeletal System
 Parts of the skeletal system
 Bones (skeleton)
 Joints
 Cartilages
 Ligaments
Axial vs. Appendicular
 Divided into two divisions
 Axial skeleton – bones that form the
longitudinal axis of the body
 Example: skull, bony thorax, & vertebral
column
 Appendicular skeleton – bones of the limbs
and girdles
 Example: arms, shoulder, legs, hips
Functions of Bones
 Support of the body
 Protection of soft organs
 Movement due to attached skeletal muscles
 Storage of minerals and fats
 Blood cell formation
Bones of the Human Body
 The adult skeleton has 206 bones
 Two basic types of bone tissue
 Compact bone
 Homogeneous
 Spongy bone
 Small needle-like
pieces of bone
 Many open spaces
Figure 5.2b
Classification of Bones
 Long bones
 Typically longer than wide
 Have a shaft with heads at both ends
 Contain mostly compact bone
 Examples: Femur, humerus
Classification of Bones
 Short bones
 Generally cube-shape
 Contain mostly spongy bone
 Examples: Carpals, tarsals
Classification of Bones
 Flat bones
 Thin and flattened
 Usually curved
 Thin layers of compact bone around a
layer of spongy bone
 Examples: Skull, ribs, sternum
Classification of Bones
 Irregular bones
 Irregular shape
 Do not fit into other bone classification
categories
 Example: Vertebrae and hip
Classification of Bones on the Basis of
Shape
Figure 5.1
Bone Markings
 Surface features of bones
 Sites of attachments for muscles, tendons, and
ligaments
 Passages for nerves and blood vessels
 Categories of bone markings
 Projections and processes – grow out from
the bone surface
 Depressions or cavities – indentations
Gross Anatomy of a Long Bone
 Diaphysis
 Shaft
 Composed of
compact bone
 Epiphysis
 Ends of the bone
 Composed mostly of
spongy bone
Figure 5.2a
Structures of a Long Bone
 Medullary cavity
 Cavity of the shaft
 Contains yellow
marrow (mostly fat)
in adults
 Contains red marrow
(for blood cell
formation) in infants
Figure 5.2a
Structures of a Long Bone
 Periosteum
 Outside covering
of the diaphysis
 Fibrous connective
tissue membrane
 Arteries
 Supply bone cells
with nutrients
Figure 5.2c
Structures of a Long Bone
 Articular cartilage
 Covers the
external surface of
the epiphyses
 Made of hyaline
cartilage
 Decreases friction
at joint surfaces
Figure 5.2a
Microscopic Anatomy of Bone
 Osteon (Haversian System)
 A unit of bone
 Central (Haversian) canal
 Opening in the center of an osteon
 Carries blood vessels and nerves
 Perforating (Volkman’s) canal
 Canal perpendicular to the central canal
 Carries blood vessels and nerves
Microscopic Anatomy of Bone
Figure 5.3
Microscopic Anatomy of Bone
 Lacunae
 Cavities containing
bone cells (osteocytes)
 Arranged in concentric
rings
 Lamellae
 Rings around the
central canal
 Sites of lacunae
Detail of Figure 5.3
Microscopic Anatomy of Bone
 Canaliculi
 Tiny canals
 Radiate from the
central canal to
lacunae
 Form a transport
system
Detail of Figure 5.3
Changes in the Human Skeleton
 In embryos, the skeleton is primarily hyaline
cartilage
 During development, much of this cartilage is
replaced by bone
 Cartilage remains in isolated areas
 Bridge of the nose
 Parts of ribs
 Joints
Bone Growth
 Epiphyseal plates allow for growth of long
bone during childhood
 New cartilage is continuously formed
 Older cartilage becomes ossified
 Cartilage is broken down
 Bone replaces cartilage
Bone Growth
 Bones are remodeled and lengthened until
growth stops
 Bones change shape somewhat
 Bones grow in width
Long Bone Formation and Growth
Figure 5.4a
Long Bone Formation and Growth
Figure 5.4b
Types of Bone Cells
 Osteocytes
 Mature bone cells
 Osteoblasts
 Bone-forming cells
 Osteoclasts
 Bone-destroying cells
 Break down bone matrix for remodeling and
release of calcium
 Bone remodeling is a process by both osteoblasts
and osteoclasts
Bone Fractures
 A break in a bone
 Healing time is approx. six to eight weeks for
simple fractures
 Healing time varies
Treatment
 Bone fractures are treated by reduction and
immobilization
 Realignment of the bone
 Closed reduction – bone ends are forced back
into normal position by doctor’s hands
 Open reduction – surgery is needed to put
bone ends together using pins or wires
 After reduction, it is immobilized by a cast or
traction to allow for healing
Types of fractures
 Simple (closed) – clean break, does not break skin
 Compound (open) – broken ends of the bone
protrude through soft tissue and skin
 Comminuted – bone breaks into many fragments
 Compression - bone is crushed
 Depressed – broken bone is pressed inward
 Impacted – broken bone end are forced into each
other
 Spiral – ragged break caused by twisting forces
 Greenstick – incomplete break, common in children
Common Types of Fractures
Table 5.2
Repair of Bone Fractures
 Hematoma (blood-filled swelling) is formed
 Break is splinted by fibrocartilage to form a
callus
 Fibrocartilage callus is replaced by a bony
callus
 Bony callus is remodeled to form a
permanent patch
Stages in the Healing of a Bone Fracture
Figure 5.5
The Axial Skeleton
 Forms the longitudinal part of the body
 Divided into three parts
 Skull
 Vertebral column
 Bony thorax
The Axial Skeleton
Figure 5.6
The Skull
 Two sets of bones
 Cranium
 Facial bones
 Bones are joined by sutures
 Only the mandible is attached by a freely
movable joint
Cranium
 Composed of eight large flat bones, all single,
except for two paired bones(parietal and temporal)
 Frontal bone
 Forms the forehead, under the eyebrows, and the
superior part of each eye’s orbit
 Parietal bone
 Paired bones that form the most superior and lateral
walls of the cranium
 Temporal bones
 Inferior to the parietal bones
Cranium
 Occipital bone
 Most posterior bone of the cranium. Forms the floor and
back wall of the skull
 In the base of this bone, is the foramen magnum, a large
opening that allows the brain to connect to the spinal cord
 Sphenoid bone
 Goes the width of the skull and forms part of the floor of the
cranial cavity
 Ethmoid bone
 Anterior to the sphenoid and forms the roof of the nasal
cavity and part of the medial walls of the orbits(eyes)
Facial Bones
 Fourteen bones compose the face. Twelve paired, only the
mandible and vomer are single
 Maxillae or maxillary bones
 Fuse to form the upper jaw
 All facial bones, except the mandible join the maxillae
 Palatine bones
 Paired bones that form the posterior part of the hard
palate
 Zygomatic bones
 Cheekbones
 Also form parts of the lateral walls of the eye orbit
 Lacrimal bones
 Form the medial walls of each orbit
 Serves as a passageway for tears
 Nasal bones
 Form the bridge of the nose
 Vomer bone
 Single bone
 Forms the nasal septum
 Inferior conchae
 Thin curved bones projecting from the lateral walls of the
nasal cavity
 Mandible
 Lower jaw
 Largest and strongest bone of the face
 Joins the temporal bones on each side of the face
 Forming the only freely movable joint in the skull
The Skull
Figure 5.7
Bones of the Skull
Figure 5.11
Human Skull, Superior View
Figure 5.8
Human Skull, Inferior View
Figure 5.9
Paranasal Sinuses
 Hollow portions of bones surrounding the
nasal cavity
Figure 5.10
Paranasal Sinuses
 Functions of paranasal sinuses
 Lighten the skull
 Give resonance and amplification to voice
Figure 5.10
The Hyoid Bone
 The only bone that
does not articulate
with another bone
 Serves as a moveable
base for the tongue
 It is suspended in the
midneck region above
the larynx
Figure 5.12
The Fetal Skull
 The fetal skull is large
compared to the
infants total body
length
Figure 5.13
The Fetal Skull
 Fontanelles – fibrous
membranes
connecting the cranial
bones
 Allow the brain
to grow
 Convert to bone
within 24 months
after birth
Figure 5.13
The Vertebral Column
 Spine extends from the skull, which it supports, to the
pelvis, where it transmits the weight of the body to the
lower limbs
 It is formed of 26 irregular bones connected by
ligaments
 The spine has a normal curvature
 Each vertebrae is given a name according to its location
 Vertebrae separated by intervertebral discs
 Intervertebral disks cushion and absorb shock between
the vertebrae
 As a person ages, they are susceptible to herniated
disks(slipped)
Vertebrae
 7 cervical
 12 thoracic
 5 lumbar
 sacrum
 coccyx
Vertebral Column
Figure
5.14
Form of the vertebral column
 Cervical vertebrae (C1 – C7)
 Forms the neck
 C1 – the atlas, allows you to nod “yes”
 C2 – the axis, allows for the rotation and you
to move from side to side to say “no”
 C3-C7 – smallest and lightest vertebrae
Form of the vertebral column
 Thoracic vertebrae (T1-T12)
 Lumbar vertebrae (L1-L5)
 Sacrum
 Formed by the fusion of five vertebrae
 Forms the posterior wall of the pelvis
 Articulates with the sacroiliac joints
 Coccyx
 Formed by the fusion of three to five small
irregularly shaped vertebrae
 Tailbone
Structure of a Typical Vertebrae
Figure 5.16
Regional Characteristics of Vertebrae
Figure 5.17a–b
Regional Characteristics of Vertebrae
Figure 5.17c–d
Curvature of the spine
 The disks and S-shaped structure of the
vertebral column work to prevent shock
 Primary curvatures – curvatures of the
thoracic and sacral regions and are present at
birth
 Secondary curvatures – cervical curvature
develops as a baby raises their head, and
lumbar curvature develops as a baby begins
to walk
Abnormal curvature of the spine
 May be present at birth or result from disease
or poor posture
 Scoliosis – medial or lateral (right or left)
curve
 Kyphosis – curve at the superior or thoracic
part of the spine
 Lordosis – curve at the inferior or lumbar part
of the spine
The Bony Thorax
 Forms a cage to
protect major
organs
 Made-up of
three parts
 Sternum
 Ribs
 Thoracic
vertebrae
Figure 5.19a
Sternum – breastbone
 Flat bone and the result of the fusion of 3
bones:
 Manubrium
 Body
 Xiphoid process
 It attaches to the first 7 ribs
Ribs
 12 pairs of ribs forms the walls of the thoracic cage
 True ribs – first 7 pairs of ribs attach directly to the
sternum by costal cartilages
 False ribs – next 5 pairs, either attach indirectly to
the sternum or are not attached to the sternum at all
 Floating ribs – last two pairs of false ribs lack the
sternal attachments
 Intercostal spaces are filled with intercostals
muscles that aid in breathing
The Appendicular Skeleton
 Composed of 126 bones, which attach the
limbs to the axial skeleton
 Limbs (appendages)
 Pectoral girdle
 Pelvic girdle
The Pectoral (Shoulder) Girdle
 Composed of two bones
 Clavicle – collarbone
 It attaches to the arm away from the thorax and
helps prevent shoulder dislocation
 Scapula – shoulder blade
 Triangular and are commonly called wings
 These bones allow the upper limb to have
exceptionally free movement
 Shoulder girdle is light and flexible, but very
susceptible to dislocation
Processes of the scapula
 Acromion process – enlarged end of the spine
and attaches to the clavicle
 Coracoid process – points over the shoulder
and anchors some muscles
Borders of the Scapula
 Superior
 Inferior angle
 Vertebral(medial)
 Axillary(lateral)
 Glenoid cavity – a shallow socket that
receives the head of the arm bone
Bones of the Shoulder Girdle
Figure 5.20a–b
Bones of the Shoulder Girdle
Figure 5.20c–d
Bones of the Upper Limb
 The arm is formed by
a single bone
 Humerus
 Head of the humerus
or proximal end fits
into the glenoid cavity
 The distal end forms a
joint with the ulna
Figure 5.21a–b
Bones of the Upper Limb
 The forearm has two
bones
 Radius – located on
the lateral side or
thumb side
 Ulna – located on the
medial side or pinky
side
Figure 5.21c
Bones of the Upper Limb
 The hand
 Carpals – eight bones arranged in two rows form the
carpus, or the wrist
 Metacarpals – palm
 Phalanges – fingers
 Each hand consists of 14 phalanges – three in each
finger
 Making proximal, middle, and distal
 The thumb is an exception, it has two, proximal and
distal
Bones of the Upper Limb
Figure 5.22
Bones of the Pelvic Girdle
 Hip bones (Coxal Bones)
 Composed of three pair of fused bones
 Ilium
 Ischium
 Pubic bone
 The total weight of the upper body rests on the pelvis
 Protects several organs
 Reproductive organs
 Urinary bladder
 Part of the large intestine
Ilium
 The ilium connects posteriorly with the
sacrum at the sacroiliac joint
 It is a large, flaring bone that forms most of
the hip bone
 If you put your hands on your hips, they are
resting on the ilium
 The upper edge of the ilium is the iliac crest
Ischium
 The ischium is the sitdown bone because it
forms the inferior part of the coxal bone
 The ischial tuberosity is a roughened area that
receives body weight when you are sitting
Pubis
 The pubis is the most anterior part of a coxal
bone
 The pubic bones of each hipbone fuse
anteriorly to form a cartilaginous joint called
the pubic symphysis
Bones of the Pelvic Girdle
 The ilium, ishcium, and pubis fuse at a deep
socket called the acetabulum
 The acetabulum receives the head of the thigh
bone(femur)
 The male and female pelvis differs
The Pelvis
Figure 5.23a
The Pelvis: Right Coxal Bone
Figure 5.23b
Gender Differences of the Pelvis
Figure 5.23c
Bones of the Lower Limbs
 The thigh has
one bone
 Femur –
thigh bone
Figure 5.24a–b
Femur
 Heaviest, strongest bone in the body
 The proximal end has a ball-like head, a neck, and
greater and lesser trochanters
 It has many sites for muscle attachment such as the
trochanters and gluteal tuberosity
 The head of the femur articulates or moves with the
acetabulum of the hip bone in a deep, secure socket
 Distally, the femur has lateral and medial condyles
that articulate or move with the tibia below
Bones of the Lower Limbs
 The leg has
two bones
 Tibia
 Fibula
Figure 5.24c
Tibia
 Larger and more medial
 At the proximal end, the medial and lateral
condyles articulate or move with the distal
end of the femur forming the knee joint
 Patella is the kneecap
 The patellar tendon attaches to the tibial
tuberosity, a roughened area on the anterior
tibial surface
 Distally, the medial malleolus is the inner
bulge of the ankle
Fibula
 Lies alongside the tibia is thin and sticklike
 The fibula has no part in forming the knee
joint
 The distal end has the lateral malleolus,
forming the outer part of the ankle
Bones of the Lower Limbs
 The foot
 Tarsus – ankle
 Metatarsals – sole
 Phalanges – toes
Figure 5.25
Foot
 Supports our body weight and serves as a lever that allows us
to propel or move our bodies forward when we walk or run
 Tarsus makes up the ankle
 It is composed of seven tarsal bones
 Most weight is carried by two tarsal bones:
 Calcaneus or heelbone
 Talus or ankle bone located between the tibia and the
calcaneus
 Five metatarsals form the sole
 Phalanges make up the toes
 Each toe has three phalanges, except for the great toe which
has two phalanges
Arches of the Foot
 Bones of the foot are
arranged to form three
strong arches
 Medial
longitudinal
 Lateral
longitudinal
 One transverse
Figure 5.26
Joints
 Articulations of bones
 Functions of joints
 Hold bones together
 Allow for mobility
 Ways joints are classified
 Functionally
 Structurally
Functional Classification of Joints
 Synarthroses – immovable joints
 Amphiarthroses – slightly moveable joints
 Diarthroses – freely moveable joints
Structural Classification of Joints
 Fibrous joints
 Generally immovable
 Cartilaginous joints
 Immovable or slightly moveable
 Synovial joints
 Freely moveable
Fibrous Joints
 Bones united by fibrous tissue
 Examples
 Sutures
 Syndesmoses
 Allows more
movement than
sutures
 Example: distal
end of tibia and
fibula
Figure 5.27a–b
Cartilaginous Joints
 Bones connected by cartilage
 Examples
 Pubic
symphysis
 Intervertebral
joints
Figure 5.27d–e
Synovial Joints
 Articulating
bones are
separated by a
joint cavity
 Synovial fluid is
found in the joint
cavity
Figure 5.24f–h
Features of Synovial Joints
 Articular cartilage (hyaline cartilage) covers
the ends of bones
 Joint surfaces are enclosed by a fibrous
articular capsule
 Have a joint cavity filled with synovial fluid
 Ligaments reinforce the joint
Structures Associated with the Synovial
Joint
 Bursae – flattened fibrous sacs
 Lined with synovial membranes
 Filled with synovial fluid
 Not actually part of the joint
 Tendon sheath
 Elongated bursa that wraps around a
tendon
The Synovial Joint
Figure 5.28
Types of Synovial Joints Based on Shape
Figure 5.29a–c
Types of Synovial Joints Based on Shape
Figure 5.29d–f
Inflammatory Conditions Associated with
Joints
 Bursitis – inflammation of a bursa usually
caused by a blow or friction
 Tendonitis – inflammation of tendon sheaths
 Arthritis – inflammatory or degenerative
diseases of joints
 Over 100 different types
 The most widespread crippling disease in
the United States
Clinical Forms of Arthritis
 Osteoarthritis
 Most common chronic arthritis
 Probably related to normal aging processes
 Rheumatoid arthritis
 An autoimmune disease – the immune
system attacks the joints
 Symptoms begin with bilateral
inflammation of certain joints
 Often leads to deformities
Clinical Forms of Arthritis
 Gouty Arthritis
 Inflammation of joints is caused by a
deposition of urate crystals from the blood
 Can usually be controlled with diet
Developmental Aspects of the Skeletal
System
 At birth, the skull bones are incomplete
 Bones are joined by fibrous membranes –
fontanelles
 Fontanelles are completely replaced with
bone within two years after birth