Seeley's Essentials of Anatomy and Physiology - Chapter 7: Muscular System

Comprehensive question-and-answer flashcards covering Chapter 7: Muscular System of Seeley's Essentials of Anatomy and Physiology, including muscle types, tissue architecture, mechanics, nomenclature, and regional muscular anatomy.

What are the three major types of muscle tissue and their primary histological and control characteristics?

Skeletal muscle (striated, voluntarily controlled, attached to bones), Cardiac muscle (striated, involuntarily controlled, located in the heart), and Smooth muscle (non-striated, involuntarily controlled, located in blood vessels and hollow organs).

What seven bodily functions are performed by the muscular system?

1. Movement of the body, 2. Maintain posture, 3. Respiration, 4. Production of body heat, 5. Communication, 6. Constriction of organs and vessels, and 7. Contraction of the heart.

Approximately what percentage of total body weight is made up of skeletal muscle and its associated connective tissue?

Approximately $40\%$ of body weight.

Why is an individual skeletal muscle, such as the biceps brachii, classified as a complete organ?

Because it is comprised of several different tissues: muscle, nerve, and connective tissue.

What connective tissue coverings surround a whole skeletal muscle, a muscle fascicle, and an individual muscle fiber?

The epimysium surrounds the entire skeletal muscle; the perimysium surrounds bundles of muscle fibers called fascicles; and the endomysium surrounds each individual skeletal muscle fiber.

In the structural hierarchy of skeletal muscle shown in this diagram, what term describes the bundle of muscle fibers encircled by the perimysium?

A muscle fascicle.

How do tendons, aponeuroses, and retinacula differ in structure and function?

Tendons are cord-like structures formed by merged connective tissue layers that connect skeletal muscle to bone; aponeuroses are broad, sheet-like tendons; and a retinaculum is a band of connective tissue that holds down tendons at each wrist and ankle.

How are muscle origin, insertion, and belly defined?

The origin is the attachment at the least mobile location (usually proximal); the insertion is the attachment on the bone undergoing the greatest movement; and the belly is the fleshy region located between the origin and the insertion.

What functional roles are played by an agonist (prime mover), an antagonist, a synergist, and a fixator?

An agonist (prime mover) is the main muscle responsible for producing a specific movement; an antagonist opposes that movement; a synergist is a smaller muscle working with the agonist; and a fixator is a synergist that prevents movement at another joint to stabilize a bone.

By approximately what percentage can an entire parallel muscle shorten when it contracts?

Approximately $30\%$.

What is the structural arrangement of a convergent muscle, and what is a primary anatomical example?

Fascicles spread across a broad area on one side and converge toward a common attachment site (pulling on a tendon, aponeurosis, or raphe); an example is the pectoralis muscles.

What are the three structural patterns of pennate muscles shown from left to right, along with an example of each?

Unipennate (e.g., extensor digitorum), bipennate (e.g., rectus femoris), and multipennate (e.g., deltoid).

How do pennate muscles compare to parallel muscles in terms of tendon travel distance, myofibril density, and tension production?

Pennate muscles do not move their tendons as far, but they contain more myofibrils and develop more tension than parallel muscles.

What describes the fascicle arrangement and primary role of circular muscles (sphincters)?

Fascicles are arranged concentrically around an opening; contraction decreases the opening diameter, allowing them to guard body entrances or hollow organs and act as valves (e.g., orbicularis oris).

How does the anatomical line of action crossing the anterior versus posterior side of the elbow joint determine muscle action?

Muscles whose lines of action cross the anterior side are flexors of the elbow (e.g., biceps brachii), while muscles crossing the posterior side are extensors of the elbow (e.g., triceps brachii).

How does the anatomical line of action crossing the lateral versus medial side of the hip joint determine muscle action?

Muscles crossing the lateral side are abductors of the hip (e.g., gluteus medius and minimus), while muscles crossing the medial side are adductors of the hip (e.g., adductor magnus).

Which shoulder muscles produce medial rotation and lateral rotation based on their line of action crossing the joint?

The subscapularis crosses anteriorly to produce medial rotation, while the teres minor crosses posteriorly to produce lateral rotation.

Approximately how many skeletal muscles are in the human body, and what percentage do axial muscles represent?

There are approximately $700$ skeletal muscles in the human body, and axial muscles make up $60\%$ of them.

What do the orientation descriptors 'rectus', 'transversus', and 'oblique' indicate in muscle names?

'Rectus' means straight along the body's longitudinal axis; 'transversus' runs across the longitudinal axis; and 'oblique' runs at a slant to the longitudinal axis.

What do the muscle action naming terms 'buccinator', 'risorius', and 'sartorius' literally mean?

Buccinator means trumpeter; risorius means laugher; and sartorius means like a tailor.

What facial movements are controlled by the occipitofrontalis, orbicularis oculi, and buccinator?

Occipitofrontalis raises the eyebrows; orbicularis oculi closes the eyelids; buccinator puckers the mouth and flattens the cheeks.

What expressions are produced by the zygomaticus, levator labii superioris, and depressor anguli oris?

Zygomaticus produces smiling by raising the upper lips and corners of the mouth; levator labii superioris produces sneering; depressor anguli oris produces pouting by lowering the corners of the mouth.

What are the three main muscles or muscle groups of mastication and their specific actions on the mandible?

Temporalis (elevates and draws mandible posteriorly, closes jaw), masseter (elevates and pushes mandible anteriorly, closes jaw), and pterygoids (two pairs that push mandible anteriorly, closes jaw).

What is the structural and functional difference between intrinsic and extrinsic tongue muscles?

Intrinsic tongue muscles reside entirely within the tongue and change its shape, while extrinsic tongue muscles originate outside the tongue, insert into it, and alter its position.

What are the primary functions of the sternocleidomastoid and trapezius muscles on head and neck movement?

The sternocleidomastoid is the prime mover for lateral neck movement; the trapezius extends and laterally flexes the neck and head.

What is the main function of the erector spinae group of muscles?

They help keep the back straight and maintain an erect body posture.

What respiratory roles are performed by the external intercostals, internal intercostals, and diaphragm?

External intercostals elevate the ribs during inspiration; internal intercostals depress the ribs during forced expiration; and the diaphragm contracts and moves during quiet breathing.

What four muscles comprise the anterior abdominal wall, and what mechanical action do all four share?

Rectus abdominis, external abdominal oblique, internal abdominal oblique, and transversus abdominis; all four compress the abdomen.

Which two muscles form the pelvic diaphragm (pelvic floor)?

The coccygeus and levator ani muscles.

How is the perineum anatomically divided into two triangles beneath the pelvic floor?

The anterior half is the urogenital triangle, and the posterior half is the anal triangle.

What scapular actions are carried out by the trapezius, levator scapulae, and rhomboids?

Trapezius extends the neck and head and moves the shoulders/upper back; levator scapulae elevates, retracts, and rotates the scapula (and laterally flexes neck); rhomboids retract, rotate, and fix the scapula.

What are the functions of the serratus anterior and pectoralis minor muscles?

Serratus anterior elevates the ribs; pectoralis minor elevates the ribs and depresses the scapula.

What is the critical stabilizing role of the rotator cuff muscles at the shoulder joint?

They stabilize the shoulder joint by holding the head of the humerus firmly within the glenoid cavity.

What arm movements are produced by the pectoralis major, latissimus dorsi, and deltoid?

Pectoralis major adducts the arm and flexes the shoulder; latissimus dorsi medially rotates and adducts the arm, and extends the shoulder; deltoid abducts the arm.

What are the primary actions of the biceps brachii, triceps brachii, and brachialis?

Biceps brachii flexes the elbow and shoulder and supinates the forearm; triceps brachii (3 heads) extends the elbow; brachialis flexes the elbow.

Which muscles are responsible for forearm supination and pronation?

The supinator and biceps brachii produce supination (palm facing up); two pronator muscles (pronator teres and pronator quadratus) produce pronation (palm facing down).

How many intrinsic muscles are contained within the hand, and what is the role of the interossei?

There are $19$ intrinsic muscles in the hand; the interossei muscles located between metacarpals abduct and adduct the fingers.

What movements are performed by the iliopsoas, gluteus maximus, and gluteus medius at the hip joint?

Iliopsoas flexes the hip; gluteus maximus extends the hip and abducts the thigh; gluteus medius abducts and rotates the thigh.

Which four muscles make up the quadriceps femoris, and what are their movements?

Rectus femoris (extends knee and flexes hip), vastus lateralis (extends knee), vastus medialis (extends knee), and vastus intermedius (extends knee).

What makes the sartorius muscle unique, and what actions does it perform?

It is the longest muscle in the body; it flexes both the hip and knee, and laterally rotates the thigh.

Which three muscles compose the hamstring group, and what actions do they perform?

Biceps femoris, semitendinosus, and semimembranosus; they flex the knee, rotate the leg, and extend the hip.

What actions are produced by the four muscles of the anterior compartment of the leg?

Tibialis anterior dorsiflexes and inverts the foot; extensor digitorum longus extends the four lateral toes, dorsiflexes, and inverts the foot; extensor hallucis longus extends the great toe, dorsiflexes, and inverts the foot; fibularis tertius dorsiflexes and everts the foot.

What are the roles of the gastrocnemius and soleus, and through what structure do they attach to the ankle?

Gastrocnemius plantar flexes the foot and flexes the leg; soleus plantar flexes the foot; both attach to the ankle via the calcaneal tendon (Achilles tendon).

What are the common actions of the lateral compartment muscles of the leg (fibularis longus and fibularis brevis)?

Both everts and plantar flexes the foot.

How many intrinsic muscles are located in the foot, and what movements do they perform?

There are $20$ intrinsic muscles within the foot, and they produce flexion, extension, abduction, and adduction of the toes.