10 Fun Facts about your Muscles! 1. You have all the muscle fiber you will ever have at birth. Once damaged they can’t be replaced. 2. Arnold Schwarzenegger has as many muscle fibers as you – They’re just thicker! 3. A single muscle cell of the Sartorius muscle in the thigh can be more than 12 inches long. 4. There are more than 600 voluntary muscles in the body. 5. The strongest muscle of the body is the masseter muscle used for chewing! 6. Your hand contains 20 different muscles. 7. If all your muscles could pull in one direction you could create a force of 25 tons! 8. Muscles account for approximately 40% of your body weight. 9. It takes 17 muscles in your face to smile, but it takes 43 muscles to frown. 10. You take approximately 5 million steps per year using your leg muscles!
Orthopedics-Muscular The medical specialty that studies the anatomy and physiology of the muscular and skeletal systems and uses diagnostic tests, medical and surgical procedures, and drugs to treat muscular and skeletal diseases.
Figure 9-1 Muscular system
Anatomy and Physiology -Primary Function: The muscular system moves the bony framework of the body -approx. 700 skeletal muscles in the body, as well as tendons and other structures associated with the muscular system.
-All of the muscles of the body are referred to as the musculature and the musculoskeletal system.
Three General Types of Muscles: 1. Skeletal muscles 2. Cardiac muscle 3. Smooth muscles
1. Skeletal Muscles: -Provide the means by which the body can move. -Voluntary -Striated (show bands of color when seen under the microscope)
2. Cardiac Muscle: -The cardiac muscle or heart pumps blood through the circulatory system. -Involuntary muscle
3. Smooth Muscles: -Are involuntary, nonstriated muscles -Thin layer around many organs and structures (blood vessels, intestines, etc.)
Figure 9-2 Types of muscle
Muscle Origins, Insertions, and Related Structures: 1. Tendons are cordlike, nonelastic, white fibrous band of connective tissue that connect muscle to bone. 2. The origin or beginning of a muscle is where its tendon is attached to a stationary or nearly stationary bone. 3. The insertion or ending of a muscle is where its tendon is attached to the bone that moves. 4. The belly of a muscle is where its mass is the greatest, midway between the origin and insertion.
Muscle Origins, Insertions, and Related Structures 5. A bursa is a synovial membrane filled with synovial fluid, acts as a cushion to reduce friction where a tendon rubs against the bone. 6. Each muscle is wrapped in fascia, a thin connective tissue that joins to the tendon. 7. Aponeurosis is connective tissue that attaches a flat muscle to bone or to other, deeper muscles. (lower back, palms, bottom of feet, abdominal region, scalp) 8. Retinaculum is a band of fibrous tissue and fascia that holds down the tendons in the wrist and ankle.
Muscles Animation Click on the screenshot to view an animation on the topic of muscles. Back to Directory
Figure 9-3 Tendon
Naming Muscles: -The names describe where the muscle is located, its shape, its size, or what action it performs.
Table 9-1 Muscle Names and Their Meanings
Table 9-1 (cont’d) Muscle Names and Their Meanings
Figure 9-4 Origin and insertion of a muscle
Relaxed Muscle Contracted Muscle Z lineMyosinActinZ line Sarcomore Cross-bridgesZ line Movement of Actin Filament Actin Binding sites Cross-bridge Myosin Figure 36-8 Muscle Contraction Section 36-2
Relaxed Muscle Contracted Muscle Z lineMyosinActinZ line Sarcomore Cross-bridgesZ line Movement of Actin Filament Actin Binding sites Cross-bridge Myosin Figure 36-8 Muscle Contraction Section 36-2 During muscle contraction, the knoblike head of a myosin filament attaches to a binding site on actin, forming a cross-bridge.
Relaxed Muscle Contracted Muscle Z lineMyosinActinZ line Sarcomore Cross-bridgesZ line Movement of Actin Filament Actin Binding sites Cross-bridge Myosin Figure 36-8 Muscle Contraction Section 36-2 During muscle contraction, the knoblike head of a myosin filament attaches to a binding site on actin, forming a cross-bridge. Powered by ATP, the myosin cross- bridge changes shape and pulls the actin filament toward the center of the sarcomere.
Relaxed Muscle Contracted Muscle Z lineMyosinActinZ line Sarcomore Cross-bridgesZ line Movement of Actin Filament Actin Binding sites Cross-bridge Myosin Figure 36-8 Muscle Contraction Section 36-2 During muscle contraction, the knoblike head of a myosin filament attaches to a binding site on actin, forming a cross-bridge. Powered by ATP, the myosin cross- bridge changes shape and pulls the actin filament toward the center of the sarcomere. The cross-bridge is broken, the myosin binds to another site on the actin filament, and the cycle begins again.
Types of Muscle Movement -Muscles function in antagonistic pairs to produce movement. (contraction vs. relaxation) -Examples: 1. Flexion and extension 2. Abduction and adduction 3. Rotation to the right and to the left 4. Supination and pronation 5. Eversion and inversion
Figure 9-6 Extension, adduction, pronation, abduction, flexion, and plantar flexion Mark Anderson/Rubberball/Getty Images Inc – Rubberball-Royalty Free
Figure 9-7 Rotation
Figure 9-8 Extension, supination, abduction, flexion, and inversion Anthony Saint James/Getty Images – Photodisc-Royalty Free
1. Muscles of the Head and Neck: Frontalis Temporalis Orbicularis oculi Orbicularis oris Masseter Buccinator Sternocleidomastoid Platysma
Figure 9-9 Muscles of the head and neck
2. Muscles of the Shoulders, Chest, & Back Deltoid Pectoralis major Intercostal muscles Trapezius Latissimus dorsi
Figure 9-10 Muscles of the shoulder and chest
Figure 9-11 Muscles of the shoulder and back
Biceps brachii Triceps brachii Brachioradialis Thenar muscles 3. Muscles of the Upper Extremity
Figure 9-12 Muscles of the upper extremity
Figure 9-13 Extensor muscles of the forearm and the extensor retinaculum Reprinted from McMinn’s Color Atlas of Human Anatomy, 2/E. McMinn, Hutchings, Human Anatomy, 19,46,66,71.78,127,137,237,238. Copyright 2002, with permission from Elsevier.
4. Muscles of the Abdomen External abdominal oblique Internal abdominal oblique Rectus abdominis
Figure 9-14 Muscles of the abdomen
5. Muscles of the Lower Extremity Anterior Leg -Quadriceps (4) rectus femoris vastus lateralis vastus intermedius vastus medialis -Sartorius -Peroneus longus -Tibialis anterior
5. Muscles of the Lower Extremity Posterior Leg -Gluteus maximus -Hamstrings (3) Biceps femoris Semitendinosus Semimembranosus -Gastrocnemius
5. Muscles of the Posterior Lower Extremity Lower Leg -Gastrocnemius -Soleus -Plantaris
Figure 9-15 Muscles of the lower extremity.
The Physiology of a Muscle Contraction -A muscle is composed of several muscle fascicles, each of which is wrapped in fascia and connected to the tendon. -Each muscle fascicle is a bundle of individual muscle fibers.
Figure 9-17 Parts of a muscle
-These muscle fibers run parallel to each other so that, when they contract, they all pull in the same direction. -A skeletal muscle fiber (one long muscle cell) is multi-nucleated.
-Each muscle fiber is composed of myofibrils that contain the proteins actin and myosin. -A muscle contracts in response to an electrical impulse from a nerve. -Each muscle fiber is connected to a single nerve cell at the neuromuscular junction.
-Acetylcholine is a chemical messenger that changes the permeability of the muscle fiber, which shortens the muscle and produces a muscle contraction. -Sodium flows into the muscle fiber stimulating the release of calcium.
Figure 9-18 Muscle strength and size
Diseases and Conditions Diseases of the Muscles: Atrophy Avulsion Compartment syndrome Contracture Fibromyalgia
Figure 9-19 Muscle contracture Michal Heron/Pearson Education/PH College
Diseases and Conditions Diseases of the Muscles: Hyperextension-hyperflexion injury Muscle contusion Muscle spasm Muscle strain Muscular dystrophy
Diseases and Conditions Diseases of the Muscles: Myalgia Myasthenia gravis Myopathy Myositis Repetitive strain injury (RSI) Rhabdomyoma Rhabdomyosarcoma Rotator cuff tear
Diseases and Conditions Movement Disorders: Ataxia Bradykinesia Dyskinesia Hyperkinesis Restless legs syndrome (RLS) Tremor
Diseases and Conditions Diseases of the Bursa, Fascia, or Tendon Bursitis Dupuytren’s contracture Fasciitis Ganglion Pitcher’s elbow Tendonitis Tenosynovitis
Figure 9-21 Ganglion Dr. P. Marazzi/Photo Researchers, Inc.