Skeletal System
Structure and Growth of Bones
Organization of the Skeleton
Functions of the Skeletal System
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•
•
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•
Supports the body
Protects soft body parts
Produces blood cells
Stores minerals and fat
Permits flexible body
movement
• Bone
– compact bone
• dense matrix of salts
(calcium phosphate)
– spongy bone
• thin plates with open
spaces
– bone marrow
• red: produces blood
cells
• yellow: stores fat
cells = osteocytes
Tissues of the
Skeletal System
• Cartilage
Tissues of the
Skeletal System
– hyaline
• firm yet flexible
• at ends of long
bones, ribs, in nose
– fibrocartilage
• strong for support
• in knee, disks
between vertebrae
– elastic cartilage
• most flexible
• in ear flaps
cells = chondrocytes
Tissues of the
Skeletal System
• Fibrous connective
tissue
– periosteum
• covers long bones
• contains blood and
lymphatic vessels,
nerves
– ligaments
• connect bone to bone
– tendons
• connect muscles to
bones at joints
cells = fibroblasts
Cells Involved in Bone Growth and Repair
Osteoprogenitor cells
(unspecialized, give rise to other cells)
Osteoblasts
Monocytes
(bone-forming cells)
(red bone marrow)
Osteocytes
Osteoclasts
(mature bone cells)
(bone resorption)
Bone Development and Growth
• Bone formation = ossification
– Bones of the skull form by
Intramembranous ossification
• Bones develop between sheets of fibrous
tissue
– Most bones form by Endochondral
ossification
• Cartilage models are formed first
• At ossification centers, cartilage is
gradually replaced by bone
Endochondral Ossification
Spongy bone
resorbed to form
medullary cavity
Formed by
secondary
ossification
Forms during
fetal development
Forms spongy
bone surrounded
by compact bone
Band of cartilage
that allows
continued growth
Remodeling of Bones
• Osteoclasts
– break down bone
– remove worn cells
– assist in depositing calcium in the
blood
• Osteoblasts
– take calcium from blood
– form new bone
Blood clot
forms in space
between
broken ends
Bone Repair
Osteoblasts
produce
spongy bone
Fibrocartilage
fills space
Spongy bone
resorbed,
compact bone
built on periphery
Applying Your Knowledge
1.
2.
3.
4.
5.
Osteoblast
Compact bone
Spongy bone
Osteoclast
Osteocyte
Spongy bone
resorbed,
compact bone
built on periphery
A. Where is red marrow located?
B. Which one is a mature bone cell?
C. Which one would be responsible for resorbing
spongy bone as in the figure on the right?
Axial Skeleton: Midline of the Body
• Skull
• Hyoid bone
• Vertebral
column
• Rib cage
Bones of the Skull
The Vertebral Column
The Rib Cage
Appendicular Skeleton:
Pectoral and Pelvic Girdles and the Limbs
Bones of Pectoral Girdle, Arm, Hand
Bones of Pelvic Girdle, Leg, Foot
Joints: Articulations between Bones
• Fibrous joints: immovable
• Cartilaginous joints
• connected by hyaline or
fibrocartilage cartilage
• slightly movable
• Synovial joints
• separate the bones by a cavity
• freely movable
• Hinge
• Ball-and-socket
Knee Joint
Movements Permitted by Synovial Joints
Applying Your Knowledge
For A and B
1.
2.
3.
4.
5.
Skull
Thoracic vertebrae
Cervical vertebrae
Lumbar vertebrae
Coccyx
A.
B.
C.
D.
For C and D
1.
2.
3.
4.
5.
Radius
Femur
Phalanges
Sternum
Coxal bone
Which vertebrae are attached to ribs?
Which forms the “tailbone”?
Which forms the fingers and toes?
Which bone is in the upper leg?