The rotator cuff is a group of four muscles that hold your upper arm in place in your shoulder. It helps you make all the motions of your arm and shoulder. The head of your upper arm bone, also called the humerus, fits into the socket of your shoulder blade, or scapula. When you extend your arm out away from your body, the rotator cuff muscles keep it from popping out of the socket, or glenoid. Rotator cuff injuries are very common, especially in people over 40, athletes, and people whose work involves repeatedly lifting their arms overhead. Conservative treatments are usually successful.
The Human Skeleton - peshsexam2
Human muscle system , the muscles of the human body that work the skeletal system , that are under voluntary control, and that are concerned with movement, posture, and balance. Broadly considered, human muscle—like the muscles of all vertebrates—is often divided into striated muscle or skeletal muscle , smooth muscle , and cardiac muscle. Smooth muscle is under involuntary control and is found in the walls of blood vessels and of structures such as the urinary bladder , the intestines , and the stomach. Cardiac muscle makes up the mass of the heart and is responsible for the rhythmic contractions of that vital pumping organ; it too is under involuntary control. With very few exceptions, the arrangement of smooth muscle and cardiac muscle in humans is identical to the arrangement found in other vertebrate animals. This article is concerned with the skeletal muscles of the human body, with emphasis on muscle movements and the changes that have occurred in human skeletal musculature as a result of the long evolutionary process that involved the assumption of upright posture.
Anatomy of the Human Shoulder Joint
The humerus is the largest bone in the entire upper extremity. The top of the humerus joins with an area called the glenoid fossa on the scapula or shoulder blade. The bottom of the humerus touches the top of the radius and ulna which joins the upper arm with the lower arm.
The human shoulder is made up of three bones: the clavicle collarbone , the scapula shoulder blade , and the humerus upper arm bone as well as associated muscles , ligaments and tendons. All together it is made up of four joints as well as the muscles that are responsible for movement in the shoulder attached to the scapula, humerus and the clavicle. The rotator cuff muscles are a collection of muscles and tendons that surround the shoulder, giving it support and allowing its wide range of motion. The shoulder has the full range of motion from adduction, abduction, flexion, extension, internal rotation, external rotation, and degree circumduction in the sagittal plane.