Chapter 20

Musculoskeletal System

What is the Skeletal System?
Overview The adult human skeleton comprises 206 bones that are connected through cartilage, tendons, and ligaments. The skeleton provides a rigid…
Bone Structure
20.2: Bone Structure
Within the skeletal system, the structure of a bone, or osseous tissue, can be exemplified in a long bone, like the femur, where there are two types…
Joints
20.3: Joints
Joints, also called articulations or articular surfaces, are points at which ligaments or other tissues connect adjacent bones. Joints permit…
Bone Remodeling
20.4: Bone Remodeling
Bone remodeling is a continuous and balanced process of bone resorption by osteoclasts and bone formation by osteoblasts. In adults, it helps…
Skeletal Muscle Anatomy
20.5: Skeletal Muscle Anatomy
Skeletal muscle is the most abundant type of muscle in the body. Tendons are the connective tissue that attaches skeletal muscle to bones. Skeletal…
Classification of Skeletal Muscle Fibers
20.6: Classification of Skeletal Muscle Fibers
Skeletal muscles continuously produce ATP to provide the energy that enables muscle contractions. Skeletal muscle fibers can be categorized as type…
Muscle Contraction
20.7: Muscle Contraction
In skeletal muscles, acetylcholine is released by nerve terminals at the motor end plate—the point of synaptic communication between motor neurons…
Cross-bridge Cycle
20.8: Cross-bridge Cycle
As muscle contracts, the overlap between the thin and thick filaments increases, decreasing the length of the sarcomere—the contractile unit of…
Motor Units
20.9: Motor Units
A motor unit consists of two main components: a single efferent motor neuron (i.e., a neuron that carries impulses away from the central nervous…
The Spinal Cord
20.10: The Spinal Cord
The spinal cord is the body’s major nerve tract of the central nervous system, communicating afferent sensory information from the periphery to…
Nociception
20.11: Nociception
Nociception—the ability to feel pain—is essential for an organism’s survival and overall well-being. Noxious stimuli such as…
Bioengineering: Bone Strain During Dynamic Motion
20.13: Bioengineering: Bone Strain During Dynamic Motion
During landing, lower-body bones carry large mechanical loads and become deformed. This article uses musculoskeletal modeling to measure…
Developmental Biology: Zebrafish Jaw Biomechanics
20.14: Developmental Biology: Zebrafish Jaw Biomechanics
Skeletal morphogenesis is a tightly regulated process involving many cell types. This article uses finite element analysis to simulate the mechanical…
Biology: Subcellular Compartments of Muscle in C. elegans
20.15: Biology: Subcellular Compartments of Muscle in C. elegans
Age-associated decline in muscle mass and strength present a significant burden for health care are negatively correlated with mortality. In this…