Skeletal System and Bone Types Quiz

Skeletal System

• 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.

Types of Bones

• 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.

Bone Structure

• 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.

Bone Development

• 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.

Blood Supply of Bone

• 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.

Multiple Choice Questions (MCQ)

• 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.