Chapter 20

Musculoskeletal System

What is the Skeletal System?
The adult human skeleton is composed of a total of 206 bones and provides a rigid framework for the human body. While the attachment of muscles…
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
In the human body, joints are points of articulation—locations where bones meet. Types of Joints There are three main types. The…
Bone Remodeling
20.4: Bone Remodeling
Even in the adult skeleton, bones are active tissues, continuously undergoing changes in architecture. This process, called bone remodeling, consists…
Skeletal Muscle Anatomy
20.5: Skeletal Muscle Anatomy
Skeletal muscles—striated tissues under the voluntary control of the somatic nervous system—are attached to bones through collagenous…
Classification of Skeletal Muscle Fibers
20.6: Classification of Skeletal Muscle Fibers
Skeletal muscles consists of three main fiber types—one slow and two fast twitch—each distinct and adapted to a particular function based…
Muscle Contraction
20.7: Muscle Contraction
A voluntary skeletal muscle contraction begins in the brain—as a conscious effort from the frontal lobe to the primary motor…
Cross-bridge Cycle
20.8: Cross-bridge Cycle
As a muscle contracts, the overlap between the thin and thick filaments increase, decreasing the length of the sarcomere, and using energy in the…
Motor Units
20.9: Motor Units
A motor unit refers to one motor neuron—located in the spinal cord—and the population of muscle fibers that it innervates. While every…
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, generally referred to as pain, is the process through which a noxious stimulus is transmitted through the peripheral and central nervous…
Examining the Shoulder
20.12: Examining the Shoulder
Examination of the shoulder can be complex, because it actually consists of four separate joints: are the glenohumeral (GH) joint, the…
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…