Skeletal System and Bone Types Quiz

Study Notes

The skeletal system, also known as the skeleton, is composed of cartilage and bone.
Cartilage is softer and less rigid than bone, forming the temporary skeleton of a developing fetus.
Cartilage is retained throughout life in specific locations: articular cartilages, costal cartilages, air passages (nasal, laryngeal, tracheal, bronchial), and the external ear.

Long bones: Have a long, tubular shaft with a central medullary cavity. Examples include the humerus and femur. Small examples of long bones are metacarpals and phalanges.
Short bones: Subjected to pressure, have a thin cortex of compact bone with interior cancellous bone. Examples include carpal and tarsal bones.
Flat bones: Formed from inner and outer layers of compact bone with a spongy bone (diploe) layer between. Examples include the skull, ribs, sternum, and scapula.
Irregular bones: Bones that don't fit easily into the other categories. Vertebrae are an example
Pneumatic bones: Contain air spaces. Examples include the maxillary, sphenoidal, frontal, and ethmoidal sinuses, as well as the mastoid bone.
Sesamoid bones: Small bones deposited in tendons of muscles to reduce friction. The patella is an example.

Diaphysis: The central, tubular region of a long bone.
Medullary cavity: The lumen (inner hollow space) of the diaphysis.
Metaphysis: The flared region connecting the diaphysis to the epiphysis. Contains a largely cancellous (spongy) interior.
Epiphysis: The end of the bone. In growing individuals, the epiphysis is separated from the metaphysis by the epiphyseal plate (growth plate).
Periosteum: A connective tissue sheath covering the outer surface of the bone.
Spongy bone: Found inside the hard bone and forms the ends of long bones. Looks like a sponge. Contains red bone marrow.
Compact bone: Forms the surface layer of all bones and the tubular shaft of long bones.

Membranous ossification: Occurs in bones for protection of essential organs, such as the vault of the skull.
Cartilaginous ossification: Formation of bone from cartilage models. Bone initially forms within hyaline cartilage, with two centers of ossification:
- Primary ossification center: Forms the diaphysis, appearing during fetal life.
- Secondary ossification centers: Form the epiphysis, appearing after birth. Epiphyseal cartilage remains between epiphysis and diaphysis until growth is complete.

The arterial supply of bone comes from three sources:
- Periosteal arteries: Supply the outer compact bone.
- Articular arteries: Supply the joints and ends of bones.
- Nutrient arteries: Enter the bone through a nutrient canal, dividing into branches to supply the marrow and inner compact bone.

Long bone example: Humerus
Compact bone description: Found at the outer surface of all long bones
Nutrient artery function: Supplies bone marrow of the shaft
Primary ossification center description: Appears during fetal life in the middle of the shaft of the bone.