The Musculoskeletal System
Types of Skeletal Systems
The musculoskeletal system provides form, support, stability, and movement to the body.
Hydrostatic Skeleton, Exoskeleton, and Endoskeleton
The hydrostatic skeleton, exoskeleton, and endoskeleton support, protect, and provide movement to the bodies of different types of animals.
Human Axial Skeleton
The axial skeleton forms the central axis of the human body and consists of the skull, vertebral column, and thoracic cage.
Human Appendicular Skeleton
The appendicular skeleton supports the attachment and functions of the upper and lower limbs of the human body.
Bones are made of a combination of compact bone tissue for strength and spongy bone tissue for compression in response to stresses.
Cell Types in Bones
The osteoblast, osteoclast, osteocyte, and osteoprogenitor bone cells are responsible for the growing, shaping, and maintenance of bones.
Intramembranous ossification stems from fibrous membranes in flat bones, while endochondral ossification stems from long bone cartilage.
Growth of Bone
Long bones lengthen at the epiphyseal plate with the addition of bone tissue and increase in width by a process called appositional growth.
Bone Remodeling and Repair
Bone is remodeled through the continual replacement of old bone tissue, as well as repaired when fractured.
Joints and Skeletal Movement
Classification of Joints on the Basis of Structure and Function
Joints, responsible for movement and stability of the skeleton, can be classified based on structure or function.
Movement at Synovial Joints
Synovial joints allow for many types of movement including gliding, angular, rotational, and special movements.
Types of Synovial Joints
Synovial joints include planar, hinge, pivot, condyloid, saddle, and ball-and-socket joints, which allow varying types of movement.
Muscle Contraction and Locomotion
Muscles are responsible for locomotion, the contractions of internal organs, and the contractions of the heart.
Skeletal Muscle Fiber Structure
Skeletal muscles are composed of striated subunits called sarcomeres, which are composed of the myofilaments actin and myosin.
Sliding Filament Model of Contraction
In the sliding filament model, the thick and thin filaments past each other, shortening the sarcomere.
ATP and Muscle Contraction
ATP is critical for muscle contractions because it breaks the myosin-actin cross-bridge, freeing the myosin for the next contraction.
Tropomyosin and troponin prevent myosin from binding to actin while the muscle is in a resting state.
Excitation–contraction coupling is the connection between the electrical action potential and the mechanical muscle contraction.
Control of Muscle Tension
Muscle tension is influenced by the number of cross-bridges that can be formed.