5
The Skeletal System
The Skeletal System
• Parts of the skeletal system
• Bones (skeleton)
• Joints
• Cartilages
• Ligaments
• Two subdivisions of the skeleton
• Axial skeleton
• Appendicular skeleton
Functions of Bones
• Support the body
• Protect ___ organs
• Skull and vertebrae for brain and spinal cord
• Rib cage for ____ cavity organs
• Allow movement due to attached skeletal muscles
• Store ____ and ______
• Calcium and phosphorus
• Fat in the internal marrow cavity
• ______ cell ______ (hematopoiesis)
Bones of the Human Body
• The adult skeleton has _____ bones
• Two basic types of bone tissue
• Compact bone
• Homogeneous
• Spongy bone
• Small needle-like pieces of bone
• Many ____ spaces
Classification of Bones on the Basis of Shape
• Bones are classified as:
• Long
• _____
• ______
• _______
Classification of Bones
• _____ bones
• Typically longer than they are wide
• _____ with heads situated at both ends
• Contain mostly _____ bone
• All of the bones of the limbs (except wrist, ankle, and kneecap
bones)
• Example:
• Femur
• Humerus
Classification of Bones
• Short bones
• Generally cube-shaped
• Contain mostly spongy bone
• Includes bones of the wrist and ankle
• _______ bones are a type of short bone which form within tendons
(patella)
• Example:
• Carpals
• Tarsals
Classification of Bones
• Flat ______
• Thin, flattened, and usually curved
• Two thin layers of compact bone surround a layer of ______ bone
• Example:
• Skull
• Ribs
• Sternum
Classification of Bones
• _______ bones
• Irregular shape
• Do not fit into other bone classification categories
• Example:
• Vertebrae
• Hip bones
Anatomy of a Long Bone
• ________
• Shaft
• Composed of compact bone
• Epiphysis
• Ends of the bone
• Composed mostly of _____ bone
Anatomy of a Long Bone
• ________
• Outside covering of the diaphysis
• Fibrous connective tissue membrane
• _______ (Sharpey’s) fibers
• Secure periosteum to underlying bone
• _______
• Supply bone cells with nutrients
Anatomy of a Long Bone
• Articular cartilage
• Covers the external surface of the _________
• Made of hyaline cartilage
• Decreases friction at joint surfaces
Anatomy of a Long Bone
• Epiphyseal plate
• Flat plate of _______ cartilage seen in young, growing bone
• Epiphyseal line
• ______ of the epiphyseal plate
• Seen in adult bones
Anatomy of a Long Bone
• Marrow (medullary) cavity
• Cavity inside of the shaft
• Contains _______ marrow (mostly fat) in adults
• Contains ____ marrow for blood cell formation in infants
• In adults, red marrow is situated in cavities of _____ bone and
epiphyses of some long bones
Bone Markings
• Surface features of bones
• Sites of attachments for _____ , _____, and ______
• Passages for ______ and blood vessels
• Categories of bone markings
• Projections or processes—grow out from the bone surface
• Terms often begin with “T”
• Depressions or cavities—indentations
• Terms often begin with “F”
Microscopic Anatomy of Compact Bone
• Osteon (Haversian system)
• A unit of bone containing _____ canal and matrix rings
• Central (Haversian) canal
• Opening in the center of an osteon
• Carries blood ____ and ____
• Perforating (Volkmann’s) canal
• Canal perpendicular to the central canal
• Carries blood vessels and nerves
Microscopic Anatomy of Bone
• _______
• Cavities containing bone cells (osteocytes)
• Arranged in concentric rings called lamellae
• ________
• Rings around the central canal
• Sites of lacunae
Microscopic Anatomy of Bone
• Canaliculi
• Tiny canals
• ______ from the central canal to lacunae
• Form a transport system connecting all bone cells to a nutrient
supply
Formation of the Human Skeleton
• In embryos, the skeleton is primarily _____ cartilage
• During development, much of this _______ is replaced by bone
• Cartilage remains in isolated areas
• Bridge of the nose
• Parts of ribs
• Joints
Bone Growth (Ossification)
• Epiphyseal plates allow for ______ growth of long bones during
childhood
• New cartilage is continuously formed
• Older cartilage becomes ______
• Cartilage is broken down
• Enclosed cartilage is digested away, opening up a medullary
cavity
• Bone replaces cartilage through the action of ______
Bone Growth (Ossification)
• Bones are _____ and ______ until growth stops
• Bones are remodeled in response to two factors
• Blood calcium levels
• Pull of gravity and muscles on the skeleton
• Bones grow in width (called appositional growth)
Types of Bone Cells
• Osteocytes—mature bone cells
• Osteoblasts—bone-forming cells
• Osteoclasts—_____ bone-destroying cells
• Break down bone _____ for remodeling and release of calcium in
response to ______ hormone
• Bone remodeling is performed by both _______ and osteoclasts
Bone Fractures
• Fracture—break in a bone
• Types of bone fractures
• _____ (simple) fracture—break that does not penetrate the skin
• _____ (compound) fracture—broken bone penetrates through the
skin
• Bone fractures are treated by reduction and immobilization
Common Types of Fractures
Repair of Bone Fractures
• _______ (blood-filled swelling) is formed
• Break is splinted by ______ to form a callus
• Fibrocartilage callus is replaced by a bony _____
• Bony callus is remodeled to form a _______ patch