CHAPTER 7 Muscles and Joints
Muscles Overview • Muscles support and maintain body posture through a low level of contraction • Skeletal muscles produce a substantial amount of heat when they contract
Types of Muscles • Skeletal • Attaches to the bones of the skeleton • Voluntary/striated • Operates under conscious control • Smooth • Called visceral muscle • Involuntary/not striated • Not under conscious control
Types of Muscles • Cardiac • Forms the wall of the heart • Involuntary
Attachment of Muscles • Tendon • Attaches muscles to bones • Point of origin • Point of attachment of the muscle to the bone that is less movable • Point of insertion • Point of attachment to the bone that it moves
Question True or False: Of the 3 types of muscle, cardiac is the only one that is voluntary.
Answer False. Skeletal is voluntary. Thankfully, we do not have to think about making our heart beat (cardiac) or moving food through our digestive tract (smooth).
Muscles of the Head and Neck • Buccinator • Located in fleshy part of cheek • Temporal • Located above and near the ear • Masseter • Located at the angle of the jaw • Raises the mandible and closes the jaw
Muscles of the Head and Neck • Sternomastoid • Also called the sternocleidomastoid • Extends from the sternum upward along the side of the neck to the mastoid process
Muscles of the Upper Extremities • Trapezius • Triangular-shaped muscle • Extends across the back of the shoulder • Covers back of neck • Inserts on clavicle and scapula
Muscles of the Upper Extremities • Latissimus dorsi • Originates from vertebrae of lower back • Crosses lower half of thoracic region • Passes between humerus and scapula • Inserts on anterior surface of humerus • Forms the posterior border of the armpit
Muscles of the Upper Extremities • Pectoralis major • Large, fan-shaped muscle • Crosses the upper part of the front chest • Originates from sternum • Crosses over to humerus
Muscles of the Upper Extremities • Deltoid • Covers the shoulder joint • Originates from clavicle and scapula • Inserts on lateral side of the humerus
Muscles of the Upper Extremities • Biceps brachii • Muscle has two heads • Originates from scapula • Inserts on the radius
Muscles of the Upper Extremities • Triceps brachii • Muscle has three heads • Originates from scapula and humerus • Inserts onto olecranon process of the ulna at the elbow
Question If you have a tension headache and the back of your neck feels like it is in a vice grip, which muscle is most likely responsible? • trapezius • sternocleidomastoid • biceps brachii • latissimus dorsi
Answer a. The trapezius muscle covers the back of the neck and shoulders, which is where most tension headaches occur.
Muscles of the Lower Extremities • Gluteus maximus • Forms most of the fleshy part of the buttock • Originates from ilium and inserts in the femur • Gluteus medius • Located above the upper outer quadrant of the gluteus maximus muscle • Originates from posterior part of ilium • Inserts in greater trochanter of the femur
Muscles of the Lower Extremities • Quadriceps femoris • Form anterior part of the thigh • Help extend the thigh • Hamstring muscles • Located in posterior part of the thigh • Help flex leg on the thigh • Help extend the thigh
Muscles of the Lower Extremities • Gastrocnemius • Main muscle of the calf • Attaches to heel bone by way of Achilles tendon • Used to plantar flex foot and flex toes • Tibialis anterior • Positioned on the front of the leg • Used to dorsiflex foot and turn foot inward
Question A runner suddenly grabs the back of his or her leg in pain. Which muscle group was injured? • quadriceps femoris • gastrocnemius • hamstring • tibialis anterior
Answer c. The quadriceps muscle group is on the anterior surface of the upper leg, and the hamstring group is on the posterior surface.
PATHOLOGICAL CONDITIONS Muscles
Muscular Dystrophy • Pronounced • (MUSS-kew-lar DIS-troh-fee) • Defined • Group of genetically transmitted disorders • Characterized by progressive weakness and muscle fiber degeneration • No evidence of nerve involvement or degeneration of nerve tissue
Polymyositis • Pronounced • (pol-ee-my-oh-SIGH-tis) • Defined • Chronic, progressive disease affecting the skeletal muscles • Characterized by muscle weakness and degeneration • Atrophy
Rotator Cuff Tear • Pronounced • (ROH-tay-tor kuff TAIR) • Defined • Tear in muscles that form a “cuff” over upper end of arm • Rotator cuff helps to lift and rotate the arm • Also helps to hold head of humerus in place during abduction of arm
Question True or False: The term muscular dystrophy means development of bad muscle, while polymyositis means inflammation of many muscles.
Answer True. Both diseases affect skeletal muscle, but their effects are different.
Animation Click Here to Play Shoulder Injuries Animation
Diagnostic Techniques, Treatments, and Procedures • Electromyography • Process of recording strength of contraction of a muscle when stimulated by electric current • Muscle biopsy • Extraction of a specimen of muscle tissue, through biopsy needle or incisional biopsy, for purpose of examining it under a microscope
ANATOMY & PHYSIOLOGY Joints
Joints Overview • Joint = articulation • Point at which two individual bones connect • Joints determine degree of movement • Movement ranges from free to limited • Suture = immovable joint • Purpose is to bind bones together
Classification of Joints (Structural) • Fibrous • Surfaces of bone fit closely together • Held together by fibrous connective tissue • Immovable joint • Example: suture between the skull bones
Classification of Joints (Structural) • Cartilaginous • Bones are connected by cartilage • Limited movement joint • Example: Symphysis • Joint between the pubic bones of the pelvis
Classification of Joints (Structural) • Synovial • Space between the bones = joint cavity • Joint cavity lined with synovial membrane • Synovial membrane secretes synovial fluid • Bones are held together by ligaments • Free movement joint • Example = shoulder
Classification of Joints (Functional) • Hinge • Allows a back and forth type motion • Example: elbow • Ball-and-socket • Allows movement in many directions around a central point • Example: shoulder joint and hip joint
Question True or False: The cartilaginous joint between the 2 halves of the pelvis (symphysis) is vital for childbirth.
Answer True. This softens during pregnancy, which allows for expansion as the baby passes through the pelvic bones and into the birth canal.
Question What enables our movable joints to move freely and without pain? • cartilage • fibrous tissue • connective tissue • synovial membrane
Answer d. This membrane secretes synovial fluid for lubrication in the joint cavity.