Chapter 6
Lecture Slides
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Learning Outcomes
• Functions of the Skeletal System
1. Describe the basic functions of the skeletal
system.
• Bone Structure
2. Describe the structure of a long bone.
3. Describe the microscopic structure of compact
bone.
Learning Outcomes
• Bone Formation
4. Compare intramembranous and endochondral
ossification .
5. Compare the functions of osteoblasts and
osteoclasts.
• Divisions of the Skeleton
6. Name the two divisions of the skeleton.
7. Describe the major surface features of bones.
Learning Outcomes
• Axial Skeleton
8. Identify the bones of the axial skeleton.
9. Compare the skull of an infant and an adult.
10. Compare cervical, thoracic, lumbar, and
sacral vertebrae.
• Appendicular Skeleton
11. Identify the bones of the appendicular
skeleton.
Learning Outcomes
• Articulations
12. Compare immovable, slightly movable, and
freely movable joints.
• Disorders of the Skeletal System
13. Describe common disorders of bones.
14. Describe common disorders of joints.
6.1 Functions of the Skeletal System
1.
2.
3.
4.
5.
Support
Protection
Attachment sites for skeletal muscles
Blood cell production
Mineral storage
6.2 Bone Structure
• Bones are composed of a number of tissues
– Bone tissue is the bulk of each bone
• There are four basic types of bone based on
shape
–
–
–
–
Long bones
Short bones
Flat bones
Irregular bones
• Structure of a Long
Bone
– Epiphysis
– Articular cartilage
– Diaphysis
– Medullary cavity
– Endosteum
– Epiphyseal disk
– Periosteum
• Spongy bone
– Interior of small
bones, skull bones,
and epiphyses
– Consists of
trabeculae and
spaces filled with
red bone marrow
– Reduces bone
weight without
reducing strength
• Compact bone
– Wall of diaphysis
and surface of
diaphysis
– Tightly packed
tissue with no
spaces
– Strong and gives
supportive strength
• Microscopic Structure
– Bone cells lie inside lacunae
– Compact bone
•
•
•
•
•
Osteons
Osteonic canals
Lamellae
Foramen
Canaliculi
– Spongy bone
• Lack osteons
• Receive nutrients by diffusion through canaliculi
6.3 Bone Formation
• Ossification is the process of bone
formation during the 6th or 7th week of
embryonic life
• Two types of bone formation
– Intramembranous ossification
– Endochondral ossification
• For both types of bone formation
– Primitive connective tissue cells become
osteoblasts
– Osteoblasts deposit bone matrix around
them
– Once trapped in matrix, osteoblasts
become osteocytes
• Intramembranous Ossification
– Forms most skull bones
– Steps involved
• Connective tissue membranes form at sites of
future intramembranous bones
• Some cells become osteoblasts
• Osteoblasts deposit spongy bone beginning at
center of bone
• Osteoblasts form layer of compact bone atop
the spongy bone
• To produce the correct bone shape
– Use osteoclasts to remove bone matrix
– Use osteoblasts to reform new bone matrix
• Endochondral Ossification
– Forms most bones of the body
– Example: long bones
– Steps involved
• Bones are preformed in hyaline cartilage
• Primary ossification center forms in center of
cartilage
• Periosteal osteoblasts form a compact bone
collar around primary ossification center
• Cartilage in the primary center calcifies and
chondrocytes die
• Blood vessels and nerves penetrate the center,
bring osteoblasts with them
• Osteoblasts form spongy bone at the primary
ossification center
• Secondary ossification center forms in the
epiphyses
• Osteoclasts remove the spongy bone and form
the medullary cavity
• Bone continues to grow
• At the end of the process, the epiphyseal plate
separates the epiphyses from the diaphysis
– Continued growth in diameter due to
formation of compact bone beneath the
periosteum
– Continued growth in length takes place
at the epiphyseal disk
• Cartilage grows on the epiphyseal side
• Cartilage is converted into bone on the
diaphysis side
– Osteoblasts and osteoclasts
continually reshape the bone as it
grows
– Bone growth in length continues until
age 25
• Epiphyseal plate is completely replaced
by bone
• Epiphyseal line is all that remains
• Homeostasis of Bone
– Bone is continually remodeled due to
activity of osteoclasts and osteoblasts
– Remodeling can be affected by
• Physical activity
• Dietary calcium intake
• Age
6.4 Divisions of the Skeleton
• Skeleton is divided into two divisions
– Axial skeleton
• Bones along the longitudinal axis of the body
– Appendicular skeleton
• Pectoral girdle and upper extremities
• Pelvic girdle and lower extremities
6.5 Axial Skeleton
• Skull
– Divided into two segments
• Cranium
• Facial bones
– Bones joined by sutures
• Immovable joints
– Several bones possess paranasal
sinuses
– Cranium
• Frontal bone
– Anterior part of cranium
• Parietal bones
– Sides and roof of cranium
• Occipital bones
– Posterior portion and floor of cranium
• Temporal bones
– Inferior to parietal bones on each side of
the cranium
– Temporomandibular joint
• Sphenoid bone
– Forms part of cranium floor, lateral posterior
portions of eye orbits, lateral portions of
cranium anterior to temporal bones
• Ethmoid bone
– Anterior portion of cranium, including medial
surface of eye orbit and roof of nasal cavity
– Nasal conchae
– Facial Bones
• Maxillae
– Form upper jaw, anterior portion of hard
palate, part of lateral walls of nasal cavity,
floors of eye orbits
– Maxillary sinus
• Palatine bones
– Form posterior portion of hard palate, lateral
wall of nasal cavity
• Zygomatic bones
– Cheek bones
– Also form floor and lateral wall of each eye
orbit
• Lacrimal bones
– Medial surfaces of eye orbits
• Nasal bones
– Form bridge of nose
• Vomer
– In midline of nasal cavity
– Forms nasal septum with the ethmoid bone
• Inferior nasal conchae
– Attached to lateral walls of nasal cavity
• Mandible
– Lower jawbone
– Only movable skull bone
– Hyoid bone
• Found in anterior portion of neck, inferior to
mandible
• Does not articulate with any other bones
• Used as attachment site for tongue muscles
– The infant skull
• Newborn skull is incompletely developed
• Possess fontanels
– Non-ossified areas
– Allow for flexibility during birth and growth
afterwards
• Vertebral Column
– Extends from skull to pelvis
– Flexible and sturdy longitudinal support for
trunk
– Formed by 24 movable vertebrae, a sacrum,
and a coccyx
– Possess intervertebral discs
• Shock absorbers
– Possess four distinct curvatures
• Structure of a
Vertebra
– All vertebrae have
common features
•
•
•
•
•
Neural arch
Vertebral foramen
Spinous process
Transverse process
Superior and inferior
articulating process
• Intervertebral
foramina
– Cervical vertebrae
• Support neck
• Possess unique transverse foramen
• Atlas: cervical vertebra 1
– Articulate occipital condyles of occipital
bone
– Supports head
• Axis: cervical vertebra 2
– Possesses the odontoid process
– Serves as a pivot point for axis
– Thoracic vertebrae
• Larger vertebra with longer spinous process then
cervical vertebrae
• Ribs articulate on the transverse processes and bodies
– Lumbar vertebrae
• Heavy, thick bodies to support greater stress and
weight
• Larger processes for attachment of back muscles
– Sacrum
• Five fused sacral bones
• Forms posterior wall of pelvic girdle
– Coccyx
• Tailbone
• Three to five fused rudimentary
vertebrae
• Thoracic Cage
– Composed of
•
•
•
•
Thoracic vertebrae
Ribs
Costal cartilages
Sternum
– Functions
• Protection of internal organs
• Support of upper body
– Ribs
• Attached to thoracic vertebrae
• True ribs (#1-7)
– Attached to sternum directly by costal
cartilages
• False ribs (#8-10)
– Attach to costal cartilage of superior ribs
• Floating ribs (#11-12)
– Do not attach anteriorly, no costal cartilages
– Sternum
• Flat, elongated bone in the anterior
midline of thoracic cage
• Composed of three fused bones
– Manubrium
– Body
– Xiphoid process
6.6 Appendicular Skeleton
• Consists of
– Pelvic girdle and upper extremity
– Pelvic girdle and lower extremity
• Composed of 126 individual bones
• Pectoral Girdle
– Composed of
• Two clavicles
• Two scapula
– Clavicle
• Articulates with
sternum and
scapula
– Scapula
• Located on each
side of vertebral
column
• Held in place by
muscles to allow
free shoulder
movement
• Upper Extremity
– Humerus
• Articulates with
scapula at the
shoulder and
ulna and radius
at the elbow
– Ulna
• Medial bone in
forearm
• Bone does not
move with hand
rotation
– Radius
• Lateral bone in
the forearm
• Bone that
rotates when the
hand is rotated
– Carpals
• Wrist bones
– Metacarpals
• Bones of the
palm of the
hand
– Phalanges
• Bones of the
fingers
• Pelvic Girdle
– Consists of
• Two coxal bones
• Sacrum
– Forms a rigid, bony pelvis
– The pelvic girdles of males and females
have several structural differences
– Coxal Bones
• Formed by three fused bones
– Ilium
- Ischium
-Pubis
• Attachment site for the legs
• Symphysis pubis
• Lower Extremity
– Femur
• Thigh bone
• Largest and
strongest bone in
the body
– Patella
• Kneecap
• Sesamoid bone in
tendon that
extends anterior to
knee
– Tibia
• Shinbone
• Larger of the lower leg
bones
• Bears body weight
– Fibula
• Slender, lateral bone
in lower leg
– Tarsals
• Ankle bones
– Metatarsals
• Bones of the
instep
– Phalanges
• Toe bones
6.7 Articulations
• An articulation is a joint or junction
between two bones
• Joints allow for varying degrees of
movement
• Three categories of joints
– Immovable
– Slightly movable
– Freely movable
• Immovable Joints (synarthrosis)
– Bones are tightly joined and separated by
thin fibrous connective tissue
– No movement at the joint
– Example: sutures
• Slightly Movable Joints
(amphiarthrosis)
– Bones separated by layer of cartilage or
fibrous connective tissue
– Limited flexibility
– Example: joints between vertebrae
• Freely Movable
Joints
(diarthrosis)
– Joints are freely
movable
– Structurally
more complex
– Several types of
freely movable
joints
– Gliding Joints
• Involve sliding of bones across each
other
• Example: carpal and tarsal bones
– Condyloid Joints
• Allow movement from side to side and
back and forth
• Example: between carpals and bones of
forearm
– Hinge Joints
• Allow movement
in one direction
only
• Example: knee
and elbow joints
– Saddle Joints
• Ends of each bone are saddle shaped
• Movement is side to side and back and
forth
• Example: joint between trapezium and
metacarpal of thumb
– Pivot Joints
• Allow rotational movement
• Example: atlas on the axis
– Ball-and-Socket
Joints
• A rounded head of
one bone fits into
a concavity on
another bone
• Movement may be
rotational or in any
plane
• Example: hip and
shoulder joint
– Movements at Freely Movable Joints
• Movement is caused by contraction of
muscles that span the joint
• Movement depends upon joint type and
location of muscle(s) involved
6.8 Disorders of the Skeletal
System
• Common disorders can be characterized
as
– Disorders of bones
– Disorders of joints
• Orthopedics
– Branch of medicine that specializes in treating
skeletal disease and abnormalities
Disorders of Bones
• Fractures: broken bones
– Complete: The break is completely through the
bone.
– Compound: A broken bone pierces the skin.
– Simple: A bone does not pierce the skin.
– Comminuted: The bone is broken into several
pieces.
– Segmental: Only one piece is broken out of the
bone.
– Spiral: The fracture line spirals around the bone.
– Oblique: The break angles across the bone.
– Transverse: The break is at right angles to the
long axis of the bone.
– Incomplete: The bone is not broken completely
through.
– Green stick: The break is only on one side of the
bone, and the bone is bowed.
– Fissured: The break is a lengthwise split in the
bone.
• Osteomyelitis
– Inflammation of bone and bone marrow
due to bacterial infection
• Osteoporosis
– Weakening of bone due to loss of calcium
salts
– Common in older people, especially
postmenopausal women
– Caused by inactivity and decrease in
hormone production
• Rickets
– Childhood disease
– Due to deficiency of calcium salts in bones
– Dietary deficiency in calcium or Vitamin D
– Children have a bowlegged appearance
Disorders of Joints
• Arthritis
– Characterized by inflammation, swelling, and pain
– Rheumatoid arthritis
• Most painful and crippling type
• Result is ossification of joint, making it
immovable
• Auto-immune dissorder
– Osteoarthritis
• Most common type
• Loss of articular cartilage makes movement
restricted and painful
• Bursitis
– Inflammation of bursa
• Dislocation
– Displacement of bones forming the joint
• Herniated disk
– Intervertebral disc protrudes out beyond vertebrae
– Caused by excessive pressure
– May apply pressure to nerves
• Spinal curvatures
– Kyphosis (hunchback)
• Excessive thoracic curvature
– Lordosis (swayback)
• Excessive lumbar curvature
– Scoliosis
• Abnormal lateral curvature
• Sprain
– Tearing or stretching of ligaments and
tendons without dislocation