Updated Spring 2009
Summary & Objectives Chapter 5 – The Skeletal System
Summary
A. The functions of the skeletal system are: support, movement, protection, storage of minerals, storage
of fat, and blood cell production.
B. Bones are categorized by their shape (long, short, flat, or irregular) or their structure (compact, or
spongy).
C. An osteon is the living, structural component of compact bone and is made of osteocytes, blood
vessels, nerves, and connective tissue.
D. The nonliving portion of bone is the matrix, which consists of calcium, phosphorous, and collagen.
These components give bone its characteristic hardness while maintaining flexibility.
E. During development, bone originates as cartilage, which grows and eventually becomes replaced by
the action of osteoblasts. A similar process heals fractures.
F. Growth hormone, from the pituitary, regulates bone growth, especially during puberty.
G. Bones are continuously being remodeled by osteoblasts (cells that build bone) and osteoclasts (cells
that breakdown bone).
H. The human skeletal system (206 bones) is divided into two parts: the axial skeleton and the
appendicular skeleton.
I. Joints are junctions between bones and are classified according to their structure and amount of
movement they allow (fibrous, cartilaginous, or synovial). Synovial joints can be hinge joints or ball-
and-socket joints.
J. Ligaments hold synovial joints together, connecting bone to bone.
K. Movements at joints include: flexion, extension, adduction, abduction, rotation, circumduction,
supination, and pronation.
L. Some diseases or conditions that affect the skeletal system include osteoporosis, arthritis, fractures,
and sprains.
Objectives
1. Identify the functions of the skeletal system.
2. Identify the important molecules that make bone both hard and flexible.
3. Describe the action of osteoblasts, osteocytes, and osteoclasts.
4. Compare and contrast the structure of compact bone with spongy bone.
5. Explain the controversial roles of “natural” and “synthetic” growth hormone in human health.
6. Describe how bone develops during embryogenesis and how a fracture heals.
7. Identify imbalances that may lead to osteoporosis and how to prevent these imbalances.
8. Describe the difference between the axial skeleton and the appendicular skeleton.
9. Compare and contrast the three different types of joints and identify examples and the orientation of
any movement that can occur.
10. Describe how arthritis, strains, and torn ligaments affect joints.
Highlighted Book Terms:
skeleton, osteon, spongy bone, compact bone, periosteum, osteocytes, osteoblasts , osteoclasts,
osteoporosis, red bone marrow, yellow bone marrow, axial skeleton, appendicular skeleton, pectoral girdle,
pelvic girdle, fibrous joint, sutures, cartilaginous joint, synovial joint, ligament, hinge joint, ball-and-socket
joint, sprain, bursae, arthritis
Additional terms (some from lecture):
flexion, extension, adduction, abduction, rotation, circumduction, fracture, pubic symphysis, anterior
cruciate ligament (ACL), posterior, The Mitchell Report
