Chapter 5 Muscular System

MUSCLES Approximately 40% of your body weight Approximately 650 muscles Muscles only pull (they can’t push) You have over 30 facial muscles Eye muscles move more than 100,000 times a day

Overview of Muscle Tissues Consists of muscle cells that are highly specialized for contraction Muscle is the dominant tissue in the heart and in the walls of other hollow organs of the body. Essential function of muscle is contraction, or shortening – a unique characteristic that sets it apart from any other body tissue Muscles are responsible for essentially all body movement and can be viewed as the “machines” of the body.

There are 3 types of muscle tissue Skeletal Cardiac Smooth

Skeletal Muscle Functions Muscle plays six important roles in the body: Produce skeletal movement Maintains posture and body position Support soft tissues (abdominal wall & pelvic cavity) Guard entrances and exits (digestive and urinary tracts) Maintain body temperature (energy is converted to heat) Store nutrient reserves (proteins are broken down & amino acids are used)

Organization of Muscle Tissue Three layers of connective tissue are part of each muscle: Epimysium – dense layer of collagen fibers that surround the entire muscle Perimysium – divides the muscle into a series of compartments each containing a bundle of muscle fibers (fascicle); contains collagen & elastic fibers, blood vessels and nerves that maintain blood flow Endomysium – flexible, elastic connective tissue layer; surrounds the individual skeletal muscle cells and interconnects adjacent muscle fibers

Arrangement of Fascicles Parallel - fascicles run parallel to the long axis of the muscle *Most skeletal muscles are parallel muscles Fusiform – spindle-shaped muscles Figure 10.1

Arrangement of Fascicles Pennate – the fascicles form a common angle with the tendon (rectus femoris and deltoid) Convergent – fascicles converge on a common attachment site (pectoralis major) Figure 10.1

Arrangement of Fascicles Circular – fascicles are arranged in concentric rings around an opening (orbicularis oris) Figure 10.1

Axial and Appendicular Muscles Axial muscles arise on the axial skeleton (60% of skeletal muscles) ; position the head and spinal column and move the rib cage Appendicular muscles stabilize and move the appendicular skeleton (40% of skeletal muscles)

Naming of Skeletal Muscles Direction of muscle fibers Example: rectus (straight) Relative size of the muscle Example: maximus (largest) Slide 6.36a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Naming of Skeletal Muscles Location of the muscle Example: many muscles are named for bones (e.g., temporalis) Number of origins (where fixed end attaches to a bone, cartilage or connective tissue) Example: triceps (three heads) Slide 6.36b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Naming of Skeletal Muscles Location of the muscles origin and insertion (movable end attaches to another structure) Example: sterno (on the sternum) Shape of the muscle Example: deltoid (triangular) Action of the muscle Example: flexor and extensor Slide 6.37 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Head and Neck Muscles Figure 6.14 Slide 6.38 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Trunk Muscles Figure 6.15 Slide 6.39 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Deep Trunk and Arm Muscles Figure 6.16 Slide 6.40 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Muscles of the Pelvis, Hip, and Thigh Figure 6.18c Slide 6.41 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Muscles of the Lower Leg Figure 6.19 Slide 6.42 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Superficial Muscles: Anterior Figure 6.20 Slide 6.43 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Superficial Muscles: Posterior Figure 6.21 Slide 6.44 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Types of Ordinary Body Movements Flexion – bending at the joint Extension - straightening at the joint Hyperextension Rotation – rotating on axis Abduction – moving away from the midline Adduction – moving toward the body Circumduction – circular movement Slide 6.32 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Body Movements Figure 6.13 Slide 6.33 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Special Movements Dorsifelxion Plantar flexion

Special Movements Inversion Eversion Slide 6.34 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Special Movements Opposition Supination Pronation

Three Types of Contractions/Exercises Antagonistic muscles – work in opposition Example: bicep & tricep (flexor/extensor) Three Types of Contractions/Exercises These contractions provide resistance to make the muscle work harder for the purpose of developing muscular fitness: 1. Isometric 2. Isotonic 3. Isokinetic

Contract or tighten muscles but fibers do not change length Isometric Static contractions Contract or tighten muscles but fibers do not change length There is no movement of the joint to which the muscle is attached Examples: Block tackle in football Weight – lifter holds barbell above head

Isotonic Most common type of contraction The muscle either shortens (concentric) or lengthens (eccentric) and takes a joint through a full range of motion (ROM) by raising and lowering a fixed resistance Examples: Raising and lowering a weight

Isokinetic A muscle shortens at constant speed over the full range of motion Perform by using special equipment that contains a speed governor so that the speed of the movement is constant no matter how much tension is produced by the muscle Example: Rowing machine

Strain vs. Sprain What is a strain? Strains are injuries that involve the stretching or tearing of a musculo-tendinous (muscle and tendon) structure What is a sprain? A sprain is an injury involving the stretching or tearing of a ligament (tissue that connects bone to bone) or a joint capsule

Sprains and Strains are categorized according to severity. Grade I (mild) sprain or strain involves some stretching or minor tearing of a ligament or muscle. Grade II (moderate) sprain or strain is a ligament or muscle that is partially torn but still intact. Grade III (severe) sprain or strain means that the ligament or muscle is completely torn, resulting in joint instability.

Ankle Sprains

Examples of Strains

First Aid R – rest I - ice C - compression E - elevation

Information obtained from: http://www.mda.org/disease/dmd.html Duchenne Muscular Dystrophy (DMD) Definition - One of nine types of muscular dystrophy, a group of genetic, degenerative diseases primarily affecting voluntary muscles. Cause - An absence of dystrophin, a protein that helps keep muscle cells intact. Information obtained from: http://www.mda.org/disease/dmd.html

DMD continued..... Onset - Early childhood - about 2 to 6 years. Symptoms - Generalized weakness first affecting the muscles of the hips, pelvic area, thighs and shoulders. Calves are often enlarged. Progression - DMD eventually affects all voluntary muscles, and the heart and breathing muscles. Inheritance - X-linked recessive. DMD primarily affects boys, who inherit the disease through their mothers. Women can be carriers of DMD but usually exhibit no symptoms.