THE MUSCULAR SYSTEM The muscular tissue of the body constitutes from one-third to one-half of the body mass of the average vertebrate. Show Muscular tissue functions in: � movement and locomotion, through its direct connection with the skeletal system Because of the multiple functions of muscles, criteria for classifying muscles include: 1.
Color� red - highly vascularized and rich in myoglobin; resist fatigue
General Muscle terminology As you are familiar with from lab, many unique terms are associated with the muscular system, ranging from describing how a muscle works to the general shape of the muscle itself. The term "muscle" has at least two meanings: � muscle cell or fiber - the active contractile component: muscle cells and their endomysium Tension and strength are directly related to the number of cross-bridges between muscle filaments � in the shortest position, filament overlap interferes with cross-bridge formation and tension is low (Fig. 10.6a) Tonic fibers:� relatively slow contracting and produce low force Insertion: the point of attachment of a muscle that moves the most when the muscle shortens, and is the most distal end of limb muscles For the biceps, the belly lies anterior to the humerus, the origin the coracoid process of the scapula, and the insertion is the radial tuberosity. For the triceps, the origins are the posterior surface of the humerus and the infraglenoid tubercle of the scapula, and the insertion is the olecranon of the ulna. The action of skeletal muscles can be: � antagonistic - oppose or resist the action of another muscle (such as is the case of the biceps and the triceps) During muscle evolution, some muscles have fused with one another, others have split into distinct new muscles, some have become reduced in prominence, and others have changed their points of attachment and hence their evolution Muscle homology can be determined in three ways: - attachment similarity Cranial muscles External ocular muscles - six extrinsic ocular muscles which attach to the surface of the eye and are responsible for moving the eye within the orbit (Fig. 10.23, p. 366): Dorsal (superior) oblique Ventral (inferior) oblique Dorsal (superior) rectus Ventral (inferior) rectus Medial rectus Lateral rectus These muscles are innervated by the oculomotor nerveSome tetrapods also have a retractor bulbi, which pulls the eyeball further into the orbit to allow for coverage by the nictitating membrane (lacking in humans) Branchiometric muscles - develop from the myotomes caudal to those that produce the ocular muscles � closely associated with the visceral skeleton so they are used in both breathing and feeding.
The cucullaris is attached to the last branchial arch but is associated with the pectoral girdle In tetrapods the branchiometric musculature changed in tandem with changes in the visceral skeleton to make the animals more adapted to a terrestrial environment - resulted in a loss of many branchiometric muscles
Epibranchial and hypobranchial muscles - dorsal and ventral muscles associated with the head and trunk region that perform functions associated with jaw and tongue movement � muscles of fishes associated with feeding and breathing include: - Coracoarcuals - opens mouth Trunk/axial muscles The axial musculature associated with the
trunk can function either in locomotion or breathing In fishes, the trunk muscles remain divided into folded muscle segments or myomeres, that are divided
into myosepta � these muscles contract alternately to produce an undulating motion that propels the fish through the water In tetrapods, the trunk muscles function more in maintenance of posture, head movement, and respiration rather than in locomotion, which has shifted to the appendicular muscles The epaxial
muscles of the tetrapod trunk skeleton include: Longissimus dorsi - extends vertebral column Appendicular muscle development originates from the somites as ougrowths of the somite myotome into the limb bud - myotomic buds to the appendages As the limb bud grows, the appendicular musculature subdivides into the muscle mass that lies above the appendicular skeleton (dorsal muscles) and the mass that lies below the appendicular skeleton (ventral muscles) These muscle masses later differentiate into multiple muscle groups depending on the type of organism Fishes In general, most of the locomotion of fishes is dependent on the action of the axial musculature, which undergoes alternate contraction and relaxation to produce undulating movements of the body Fins (appendicular
appendages) function more in maintaining stability, braking and maneuvering - thus, the range of movement of fins is much more limited than that of tetrapod limbs � ventral muscles in fishes go to the formation of the abductor muscle, which pulls the fins ventrally and cranially The tetrapod appendicular musculature is more complex than that of fishes because the limbs function in both support and locomotion In tetrapods the function of the dorsal and ventral muscle groups is reversed from that seen in fishes � the dorsal muscles, which in fishes were responsible for adduction will instead abduct or extend the appendages
Locomotion The study of locomotion completes our understanding of the skeletal and muscular systems, because it examines the functional relationship between the two systems as well as between the organism and its environment We will discuss three important categories of locomotion: swimming, terrestrial locomotion, and flight. Swimming We can first distinguish vertebrates that swim by whether they are primary swimmers (species for which swimming is the sole pattern of locomotion) or secondary swimmers (species which have readapted completely or partially to an aquatic mode of life). Some general requirements of swimmers are that they must: 1) reduce the resistance that water offers to motions of the moving body Primary swimmers are generally undulatory swimmers that use the musculature of the fins only, or the fins in combination with the trunk and tail to propel themselves through the water Characteristics of the primary swimmers are: � a fusiform body that is held rigid by strong articulation of the vertebral
column Secondary swimmers are generally oscillatory swimmers that propel themselves
through the water with paddle-like movements of the appendages � appendages may also be modified into webbing or flippers to assist in propulsion In terms of terrestrial locomotion, there are many different modes that an animal may use: Cursorial - tetrapods that travel far or fast on the land. Cursorial animals possess a relatively elongate body, in which the vertebral column acts to increase running stride by stretching out to increase forward propulsion Saltatorial - tetrapods that jump or hop. Saltatorial animals have bodies in which the weight is shifted to the hind legs, the legs are powerful and strongly constructed, and the center of mass is aligned with the sacrum Scansorial - tetrapods adept at climbing. Scansorial animals have strengthened pectoral musculature and appendages, and modified phalanges for clinging to vertical surfaces Fossorial - tetrapods that are adept at digging, and live a somewhat subterranean existence. Fossorial animals have highly flexible vertebral columns, strong pectoral musculature, and modified phalanges for digging Each of these different modes of life requires dramatic modifications in the skeletal system (in terms of the parts of the body that receive the most stress) and the associated musculatureAnimals with bipedal locomotion or that are scansorial have a foot posture that is more plantigrade, in which the soles of the feet are placed flat on the ground. In contrast, most cursorial animals have a more digitigrade posture, in which the wrist and ankle are carried off the ground and the animal walks on its digits. Or, the animal may be extremely long legged, and walk only on the tips of the digits such that the terminal end of the digit is modified to form a hoof, and other digits are lost, a posture called unguligrade. Flight Tetrapods that fly can do so in three different ways. In birds, the primary flight muscles originate on the ventral surface of an expanded, keeled sternum:� pectoralis - depressor of the wing Adductor - moves a bone closer to the midline Antagonistic - condition in which a muscle opposes or resists the action of another muscle Aponeurosis - sheetlike tendon of a muscle Cursorial - tetrapods that travel far or fast on the land Depressor - produces a downward movement Digitigrade - posture in which the wrist and ankle are carried off the ground and the animal walks on its digits Epaxial - pertaining to structures that lie above or beside the vertebral axis Extensor - increases the angle at a joint Fascia-sheets of connective tissue that lie beneath the skin or ensheathe groups of muscles Flexor - decreases the angle at a joint Flight - use of wings to actively sustain movement through the air Fossorial - tetrapods that are adept at digging, and live a somewhat subterranean existence Gliding - use of broad membranes attached to limbs to increase surface area and travel a greater horizontal distance through the air Hypaxial - pertaining to structures that lie ventral to the vertebral axis Insertion - the point of attachment of a muscle that moves the most when the muscle shortens, or the most distal end of limb muscles Levator - produces an upward movement Origin - the end of a muscle that attaches to the more fixed part of the skeleton, which is the proximal end in limb muscles Oscillatory swimmers - propel themselves through the water with paddle-like movements of the appendages Parachuting - use of limbs and body to increase overall surface area to break an inadvertent fall Plantigrade - posture in which the soles of the feet are placed flat on the ground during locomotion Primary swimmers - species for which swimming is the sole pattern of locomotion Pronator - turns the palm downward Raphe - junction of two muscles at a band of connective tissue to form a line of fusion, such as linea alba Rotator - moves a bone around its longitudinal axis Saltatorial - tetrapods that jump or hop Scansorial - tetrapods adept at climbing Secondary swimmers - species which have readapted completely or partially to an aquatic mode of life from a terrestrial life Sphincter - decreases the size of an opening Supinator - turns the palm upward or anteriorly Synergistic - condition in which the muscles work together to produce a common effect Tensor - makes a body part more rigid Undulatory swimmers - use the musculature of the fins only, or the fins in combination with the trunk and tail, to propel themselves through the water Unguligrade - a locomotory posture used by long legged tetrapods, which walk only on the tips of the digits such that the terminal end of the digit is modified to form a hoof, and other digits are lost What is the movement of a limb away from the midline of the body?Abduction moves the limb laterally away from the midline of the body, while adduction is the opposing movement that brings the limb toward the body or across the midline.
What is moving a limb away from the midline of the body quizlet?Moving a limb toward the midline of the body is called adduction; abduction is moving a limb away from the midline of the body.
Which movement term is moving a limb towards the body?Movement that brings the anterior surface of the limb toward the midline of the body is called medial (internal) rotation. Conversely, rotation of the limb so that the anterior surface moves away from the midline is lateral (external) rotation (see Figure 9.5.
Which of the following techniques refers to drawing a limb away from the midline of the body by a muscle?Abduction - movement away from the midline of the body. For example, when an individual is performing jumping jacks, the outward movement of the arms and legs away from the shoulders and hips is called abduction. Adduction - the movement of a limb or other part toward the midline of the body or toward another part.
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