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Questions and Answers
Which muscles are responsible for controlling the position of the eye?
Which muscles are responsible for controlling the position of the eye?
Which muscle is classified as the strongest jaw muscle?
Which muscle is classified as the strongest jaw muscle?
What is the primary function of the orbicularis oris muscle?
What is the primary function of the orbicularis oris muscle?
Which of the following nerves supplies most of the muscles of mastication?
Which of the following nerves supplies most of the muscles of mastication?
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Which muscles are included in the extrinsic muscles of the eye?
Which muscles are included in the extrinsic muscles of the eye?
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What type of skeletal muscle is characterized by fibers that run parallel to the long axis of the muscle?
What type of skeletal muscle is characterized by fibers that run parallel to the long axis of the muscle?
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Which of the following types of muscles has fibers that form an angle with the tendon?
Which of the following types of muscles has fibers that form an angle with the tendon?
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In skeletal muscle terminology, which term refers to a muscle that opposes the action of the agonist?
In skeletal muscle terminology, which term refers to a muscle that opposes the action of the agonist?
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Which type of muscle has a broad area that converges at a single tendon attachment site?
Which type of muscle has a broad area that converges at a single tendon attachment site?
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What is the primary function of synergist muscles?
What is the primary function of synergist muscles?
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Which of the following is NOT considered a type of pennate muscle?
Which of the following is NOT considered a type of pennate muscle?
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What is the fixed point of attachment for a muscle called?
What is the fixed point of attachment for a muscle called?
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Which muscle organization type is also referred to as sphincters?
Which muscle organization type is also referred to as sphincters?
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What does the first part of a muscle's name typically indicate?
What does the first part of a muscle's name typically indicate?
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Which term describes muscles that are located superficial to the body?
Which term describes muscles that are located superficial to the body?
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What term is used to describe a muscle with a triangular shape?
What term is used to describe a muscle with a triangular shape?
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Which of the following is NOT a classification of fascicle organization within a muscle?
Which of the following is NOT a classification of fascicle organization within a muscle?
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What percentage of skeletal muscles are classified as axial muscles?
What percentage of skeletal muscles are classified as axial muscles?
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Which action corresponds with the muscle named 'flexor'?
Which action corresponds with the muscle named 'flexor'?
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What does the term 'longus' in muscle naming imply?
What does the term 'longus' in muscle naming imply?
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Which of the following describes muscles that are located inside an organ?
Which of the following describes muscles that are located inside an organ?
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Which muscle is NOT part of the rotator cuff?
Which muscle is NOT part of the rotator cuff?
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What is the primary function of the gluteus maximus muscle?
What is the primary function of the gluteus maximus muscle?
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Which pair of muscles make up the iliopsoas group?
Which pair of muscles make up the iliopsoas group?
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What is the action of the adductor magnus muscle's superior part?
What is the action of the adductor magnus muscle's superior part?
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Where do the gluteus medius and minimus muscles insert?
Where do the gluteus medius and minimus muscles insert?
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Which muscle is primarily responsible for extending the knee?
Which muscle is primarily responsible for extending the knee?
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What is the primary role of the hamstrings?
What is the primary role of the hamstrings?
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Which of the following muscles is considered an extensor of the ankle?
Which of the following muscles is considered an extensor of the ankle?
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Which muscle is responsible for rotating the tibia to unlock the knee?
Which muscle is responsible for rotating the tibia to unlock the knee?
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Which statement correctly describes the quadriceps femoris?
Which statement correctly describes the quadriceps femoris?
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What is the primary function of the flexors of the ankle?
What is the primary function of the flexors of the ankle?
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Which of the following actions does the iliopsoas perform?
Which of the following actions does the iliopsoas perform?
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What type of muscle fibers become smaller in diameter as people age?
What type of muscle fibers become smaller in diameter as people age?
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Which muscle assists in flexing both the hip and knee?
Which muscle assists in flexing both the hip and knee?
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Which of the following muscles is NOT a hamstring?
Which of the following muscles is NOT a hamstring?
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What is the action of the extensor digitorum longus?
What is the action of the extensor digitorum longus?
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Which type of hernia is commonly due to muscle defect in the diaphragm?
Which type of hernia is commonly due to muscle defect in the diaphragm?
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Which muscle is primarily involved in plantar flexion of the foot?
Which muscle is primarily involved in plantar flexion of the foot?
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What role do the flexors of the toes serve?
What role do the flexors of the toes serve?
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Which muscle is primarily responsible for flexing the shoulder?
Which muscle is primarily responsible for flexing the shoulder?
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What is the main role of the diaphragm?
What is the main role of the diaphragm?
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Which muscle group is involved in medial rotation of the shoulder?
Which muscle group is involved in medial rotation of the shoulder?
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Where does the external oblique muscle originate?
Where does the external oblique muscle originate?
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Which muscles are considered part of the rotator cuff?
Which muscles are considered part of the rotator cuff?
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What is the function of the pelvic floor muscles?
What is the function of the pelvic floor muscles?
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Which muscle assists the deltoid in arm abduction?
Which muscle assists the deltoid in arm abduction?
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What action do the external and internal intercostal muscles perform?
What action do the external and internal intercostal muscles perform?
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How does the insertion of the sternocleidomastoid muscle affect its function?
How does the insertion of the sternocleidomastoid muscle affect its function?
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Which muscle is NOT part of the abdominal wall?
Which muscle is NOT part of the abdominal wall?
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What is a common cause of a rotator cuff tear?
What is a common cause of a rotator cuff tear?
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What action do the flexor muscles of the forearm primarily perform?
What action do the flexor muscles of the forearm primarily perform?
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Which of these muscles is deep to the trapezius?
Which of these muscles is deep to the trapezius?
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Study Notes
Skeletal Muscle Classification
- Skeletal muscles are classified by fascicle organization: parallel, convergent, circular, and pennate.
- Parallel muscles have fibers running parallel to the muscle's long axis. Examples include sartorius and biceps brachii (fusiform).
- Convergent muscles have a broad origin that converges on a single tendon. Examples include pectoralis muscles.
- Circular muscles, also called sphincters, surround body openings. Examples include orbicularis oris and external anal sphincter.
- Pennate muscles have fascicles attaching obliquely to a central tendon. These are further divided into unipennate, bipennate, and multipennate types. Examples include extensor digitorum (unipennate), rectus femoris (bipennate), and deltoid (multipennate).
Origin, Insertion, and Action
- Origin: fixed point of attachment
- Insertion: moving point of attachment
- Most muscles originate or insert on the skeleton. Origin is usually proximal to insertion, but exceptions exist.
- Action: movement produced by muscle contraction. Examples include flexion, extension, adduction, and various specific movements.
Types of Muscles Based on Action
- Agonist (prime mover): produces a particular action.
- Synergist: assists the larger agonist, helping to start or stabilize. A synergistic muscle can also be a fixator.
- Antagonist: opposes the action of the agonist.
Muscle Opposition
- Agonists and antagonists work in pairs. When one contracts, the other relaxes. Examples include flexors-extensors, abductors-adductors, etc.
Muscle Terminology
- Correct muscle names often include the term "muscle." Examples include platysma and diaphragm.
- Muscle names can be determined by location, origin/insertion, fascicle organization, relative position, and structural characteristics.
Naming Skeletal Muscles
- Muscles are named based on various factors including: location in the body, origin and insertion points, fascicle organization, relative position, and structural characteristics.
Location in the Body
- Muscle names often reflect their location. Examples include temporalis (temporal bone) and frontalis (frontal bone).
Origin & Insertion
- The first part of a muscle's name often indicates its origin, while the second part indicates its insertion. Sternocleidomastoid muscle is an example (originating at sternum and clavicle, and inserting at the mastoid process).
Fascicle Organization
- Fascicle orientation within a muscle is described using terms like rectus (straight), transversus (across), and oblique (slanted).
Relative Position
- Muscles are classified as superficial (externus), deep (internus), extrinsic (outside an organ), or intrinsic (inside an organ) depending on their location relative to other structures or organs.
Structural Characteristics
- Factors such as the number of tendons (heads), shape (e.g., deltoid, trapezius), and size (e.g., longus, brevis) can be used to name and differentiate muscles.
Action
- Muscle actions are described by the specific movement they produce, such as flexion, extension, adduction, etc. Sartorius is an example, with a specific special action.
Combined Names (Example)
- Some muscles have combined names that describe their action and location. Flexor digitorum superficialis muscle is an example (flexes the fingers; located superficially).
Divisions of the Muscular System
- Axial muscles compose 60% of skeletal muscles. These muscles are involved in positioning the head and vertebral column, and moving the thoracic cage.
- Appendicular muscles (40% of skeletal muscles) support the pectoral and pelvic girdles, and move the upper and lower limbs.
Muscles of the Head & Neck
- Facial muscles control facial expressions and originate on the skull
- Muscles of mastication move the mandible.
- Extrinsic eye muscles control eye position.
- Muscles of the tongue have names ending in glossus.
- Muscles of the pharynx initiate swallowing.
Muscles of Facial Expression
- Occipitofrontalis (epicranius) is separated into frontal and occipital bellies by the epicranial aponeurosis. It raises the eyebrows.
- Orbicularis oculi closes the eyelids.
- Orbicularis oris constricts the mouth.
- Buccinator moves food within the cheeks.
Muscles of Mastication
- Masseter is the strongest jaw muscle.
- Temporalis helps lift the mandible.
- Buccinator moves food around the cheeks.
- Pterygoids (medial and lateral) assist jaw movements.
Extrinsic Muscles of the Eye
- 4 rectus muscles (superior, inferior, medial, lateral) control eye movement.
- 2 oblique muscles (superior, inferior) assist in complex eye movement.
- Note that the abducens and trochlear nerves control some eye muscles.
Muscles of the Neck
- Sternocleidomastoid muscle: flexes the neck (exceptions exist: origin is distal to insertion).
Muscles of the Abdominal Wall
- Oblique muscles (external and internal) help compress the underlying structures and rotate the vertebral column.
- Rectus muscles (rectus abdominis) flex the vertebral column and oppose the erector spinae muscles, helping control the spine.
Muscles of the Pelvic Floor
- Support pelvic organs, flex the sacrum and coccyx, and control urination and defecation. The external anal sphincter/urethral sphincter muscles are essential in this control.
- Perineum is an area of skin anterior to the anus; it extends to the vagina or base of the testicles.
- The perineum is rich in nerve endings
Muscles of Pectoral Girdle
- Trapezius, rhomboids, and levator scapulae are involved in moving the scapula.
- Serratus anterior muscle moves the scapula
Muscles Move Upper Limbs
- Muscles move the arm, forearm, and hand in various ways.
- Examples include, Deltoid, Latissimus dorsi, Pectoralis major, Subscapularis, Teres major, Infraspinatus, Teres minor
Muscles Move the Arm
- These muscles are generally involved in moving the arm in multiple directions, including: adduction, medial rotation, extension, etc.
- Specific examples include Pectoralis major, Latissimus dorsi, Deltoid, Supraspinatus, Infraspinatus, Subscapularis
Rotator Cuff
- The rotator cuff is composed of 4 muscles, including subscapularis, supraspinatus, infraspinatus, and teres minor.
- It forms a cuff to stabilize and rotate the upper arm.
Rotator Cuff Tear
- Possible causes that lead to tears include acute injuries (sports), or repetitive overhead work.
Muscles Move the Leg
- Extensors (e.g., quadriceps femoris) originate on the femoral surface and are important for knee extension
- Flexors (e.g., hamstrings) originate on the pelvic girdle are crucial for flexing the knee.
Extensors of the Knee
- Quadriceps femoris muscle (rectus femoris, vastus medialis, vastus lateralis, vastus intermedius) are important for extending the knee.
- Share one tendon
- Enclose the patella and insert at the tibial tuberosity
Flexors of the Knee
- Semitendinosus, semimembranosus, biceps femoris, and sartorius flex the knee and assist with hip flexion.
- Popliteus rotates the tibia to unlock the knee.
Muscles Move Foot & Toes
- Muscles like Gastrocnemius, Soleus, Peroneus longus, and brevis perform plantarflexion at the ankle.
- Tibialis anterior muscle opposes these extensors performing dorsiflexion.
- There are extensor and flexor muscles involved in movement of the toes.
Intrinsic Muscles of the Foot
- Located within the foot; help with fine motor control of the foot (e.g., toe movements).
Tendon Sheaths
- Wide bands of connective tissue, including the extensor and flexor retinaculum; protect the tendons as they move.
Carpal Tunnel Syndrome
- Thickening of flexor retinaculum; narrows the carpal tunnel, compressing the median nerve.
Hernia
- Protrusion of an organ through an abnormal opening (e.g., inguinal, umbilical, diaphragmatic).
Effects of Aging on Skeletal Muscles
- Skeletal muscle fibers diminish in size and elasticity due to fibrosis.
- Decreased exercise tolerance and recovery from injuries.
Skeletal Muscle Integration with Other Systems
- Skeletal muscles interact with other organ systems to maintain homeostasis and perform various bodily functions. Integration with other systems includes the urinary, nervous, endocrine, digestive, respiratory, circulatory systems.
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Description
Test your knowledge on the anatomy and functions of various muscles, including eye and jaw muscles. This quiz covers topics such as muscle types, action classifications, and nerve supply relevant to muscular function. Perfect for students studying anatomy or related fields!
