Chapter 11 - Muscular System Flashcards
How many individual muscles are contained in the muscular system?
About 700
What is the muscular system composed of?
The voluntarily controlled muscles of the body
What is function of muscles in the muscular system?
To produce movements of body parts
How do skeletal muscles produce movement?
By exerting force on tendons, which pull the bones or other structures (such as skin)
What is the origin?
The attachment of a muscle’s tendon to a stationary bone
What is the insertion?
The attachment of the muscle’s tendon to the moveable bone
When two bones articulate with each other, do they both move?
No, they usually do not move equally in response to a contraction.
One bone remains stationary and the other is pulled toward it.
Is the origin usually proximal or distal?
Is the insertion usually proximal or distal?
Origin - proximal
Insertion - distal
Does the insertion get pulled towards the origin or
Does the origin get pulled towards the insertion?
Insertion pulled towards origin
What is the belly (body)?
The fleshy portion of the muscle between the tendons
What are the actions of a muscle?
The main movements that occur when the muscle contracts
What is reverse muscle action? (RMA)
During specific movements of the body, the actions are reversed.
Therefore the positions of the origin and insertion of a specific muscle are switched.
Where is the belly of the muscle the extends the forearm located?
The triceps brachii, is located posterior to the humerus
What is a lever? What are the levers of the body?
A rigid structure that can move around a fixed point
Bones
What is the fulcrum? What serves as fulcrums in the body?
A fixed point that a lever moves around.
Joints.
What two different forces act on levers at two different points?
Effort - which causes movement
Load (or resistance) - which opposes movement
What is effort?
The force exerted by muscular contraction
What is the load (or resistance)?
The weight of the body part that is moved, or
Resistance that the body is trying to overcome
When does motion occur?
When the effort applied to the bone at the insertion exceeds the load
If you were to raise your forearm holding a book, what would be the fulcrum, the effort and the load?
Fulcrum - elbow
Effort - force of contraction of the biceps brachii
Load - weight of the forearm + weight of book
What is a mechanical advantage?
If the load is closer to the fulcrum and the effort farther from the fulcrum
A small effort is required to move a large load
What is a mechanical disadvantage?
If the load is further from the fulcrum and the effort closer to the fulcrum
A large effort is required to move a small load
What are the three types of levers?
- First class lever
- Second class lever
- Third class lever
What is a first class lever?
Fulcrum is between the effort and the load
Scissors and see-saws
Does a first class lever have mechanical advantage or disadvantage?
Depends on whether the effort or the load is closer to the fulcrum
Give an example of a first class lever in the body.
When the head is raised,
Effort - contraction of posterior neck muscles
Fulcrum - atlanto-occipital joint
Load - weight of anterior portion of the skull
What is a second class lever?
The load is between the fulcrum and the effort
Wheelbarrow
Does a second class lever produce a mechanical advantage or disadvantage?
Always produce advantage (load is closer to fulcrum)
What does a second class lever sacrifice?
Sacrifices speed and range of motion for the greatest force
This lever produces the most force
Give an example of a second class lever in the body.
Standing up on your toes,
Fulcrum - ball of foot
Load - weight of the body
Effort - contraction of the calf muscle
What is a third class lever?
Effort is between the fulcrum and the load
Pair of forceps
Does a third class lever produce a mechanical advantage or disadvantage?
Always disadvantage - effort is always closer to the fulcrum
What does the arrangement of the third class lever favor?
Speed and range of motion over force
Give an example of a third class lever in the body.
The elbow joint
Fulcrum - elbow joint
Effort - the biceps brachii muscle
Load - weight of the arm
What kind of lever is the most common in the body?
Third class lever.
What are the five patterns that fascicles can form with respect to tendons?
- Parallel
- Fusiform (spindle-shaped, narrow toward the end and wide in the middle)
- Circular
- Triangular
- Pennate (shaped like a feather)
When a muscle fibre contracts, how much does it shorten?
To about 70% of its resting length
What is the benefit of long fibres in muscles?
Greater range of motion it can produce
What does the power of a muscle depend on?
It’s total cross-sectional area
(More fibres per cross-sectional area a muscle has, the more power it can produce)
A short fibre can contract as powerfully as a long one
The fascicle arrangement usually represents a compromise between what two things?
Power
Range of motion
What is the prime mover? (Or agonist)
One muscle contracts to cause an action while the paired muscle yields (the anatagonist)
What is the anatongonist?
The muscle that stretches or yields to the effects of the prime mover.
Can the agonist and antagonist muscles switch roles?
Yes! Extending or flexing the forearm causing them to switch.
Extending - triceps brachii is prime mover
Flexion - biceps brachii is prime mover
What happens if the agonist and antagonist contract at the same time?
If there is equal force, there is no movement.
What is a synergist?
A muscle that stabilizes intermediate joints or prevents unwanted movement in intermediate joints
Aid in the movement of the prime mover
*usually located close to the prime mover.
What is a fixator?
Stabilizes the origin of the prime mover so that the prime mover can act more efficiently
- steady the proximal end, while movement occurs at the distal end
What is a compartment?
A group of skeletal muscles, their associated blood vessels, and associated nerves that all have a common function
Describe the parallel arrangement of fascicles.
Parallel to longitudinal axis of muscle
Terminate at either end in flat tendons
Example - sternohyoid muscle
Describe the fusiform arrangement of fascicles.
Fascicles nearly parallel to longitudinal axis of muscle
Terminate in flat tendons, where diameter is less than belly
Example - digastric muscle
Describe the circular arrangement of fascicles.
Fascicles in concentric circular arrangements form sphincter muscles that enclose an orifice
Example - orbicularis oculi muscle
Describe the triangular arrangement of fascicles.
Fascicles spread over broad area converge at thick central tendon
Gives muscle a triangular appearance
Example - pectoralis major muscle
Describe the unipennate arrangement of fascicles.
Fascicles arranged only on one side of tendon
Example - extensor digitorum longus muscle
Describe the bipennate arrangement of fascicles.
Fascicles arranged on both sides of centrally positioned tendons
Example - rectus femoris muscle
Describe the multipennate arrangement of fascicles.
Fascicles attach obliquely from many directions to several tendons
Example - deltoid muscle
Describe the pennate arrangement of fascicles.
Short fascicles in relation to total muscle length
Tendon extends nearly entire length of muscle
What is the goal of stretching?
- Improved physical performance
- Decreased risk of injury
- Reduced muscle soreness
- Improved posture
How are muscles named? (7 features)
- Size
- Shape
- Action
- Number of origins
- Location
- Sites of origin
- Sites of insertion
Describe rectus.
Parallel to midline
*directional orientation
Describe transverse.
Perpendicular to midline
*directional orientation
Describe oblique.
Diagonal to midline
*directional orientation
Describe maximus.
Largest
Describe minimus.
Smallest
Describe longus.
Long
Describe brevis.
Short
Describe latissimus
Widest
Describe longissimus
Longest
Describe magnus.
Large
Describe major.
Larger
Describe minor.
Smaller
Describe vastus.
Huge
Describe deltoid.
Triangular
Describe trapezius.
Trapezoid
Describe serratus.
Saw-toothed
Describe rhomboid.
Diamond-shaped
Describe orbicularis.
Circular
Describe pectinate.
Comblike
Describe piriformis.
Pear-shaped
Describe platys.
Flat
Describe quadratus.
Square, four-sided
Describe gracilis.
Slender
Describe flexor.
Decreases joint angle
Describe extensor.
Increases joint angle
Describe abductor.
Moves bones away from midline
Describe adductor.
Moves bones closer to the midline
Describe levator.
Raises or elevates body part
Describe depressor.
Lowers or depresses body part
Describe supinator.
Turns palm anteriorly
Describe pronator.
Turns palm posteriorly
Describe sphincter.
Decreases size of an opening
Describe tensor.
Makes body part rigid
Describe rotator.
Rotates bone around longitudinal axis
Describe biceps.
Two origins
Describe triceps.
Three origins
Describe quadriceps.
Four origins
Give an example of the location description.
Temporalis
Muscle near the temporal bone
Give an example of origin and insertion description.
Sternocleiodmastroid
Originating on sternum and clavicle and inserting on mastoid process of temporal bone
Which type of lever produces the most force?
Second class levers
What is the occipitofrontalis: frontal belly?
Location: superficial to frontal bone
Action: draws scalp anteriorly, raises eyebrows, and wrinkles the skin of forehead horizontally as in look of surprise
What is the occipitofrontalis: occipital belly?
Location: posterior portion, superficial to occipital bone
Action: draws scalp posteriorly
What are the occipitofrontalis held together by?
Epicranial aponeurosis (sheet-like tendon)
What is the orbicularis oris?
Location: surrounds the mouth
Action: closes and protrudes lips, as in kissing, compresses lips against teeth, and shapes lips during speech
What is the zygomaticus major?
Location: runs along your cheekbone
Action: draws angle of mouth superiorly and laterally, as in smiling
What is the buccinator?
Location: major muscle portion of the cheek
Action: presses cheeks against teeth and lips, as in whistling, blowing and sucking; draws corner of mouth laterally; and assists in mastication (chewing) by keeping food between the teeth (and not between teeth and cheeks)
What gland passes through the buccinator?
Salivary gland - passes through buccinator to reach oral cavity
What is the orbicularis oculi?
Location: around your eye
Action: closes eye
- considered a sphincter b/c it closes an orifice
What is the masseter?*
Location: beside mouth, outside and superficial of buccinator
Action: elevates mandible, as in closing mouth
Origin: maxilla and zygomatic arch
Insertion: angle and ramus of mandible
What is the temporalis?*
Location: on the temporal bone
Action: elevates and retracts mandible
Origin: temporal bone
Insertion: coronoid process and ramus of mandible
What is the strongest muscle of mastication?
Masseter
What are the muscles of mastication?
Muscles that move the lower jawbone (mandible) at the TMJ (temporomandibular joint)
- masseter, temporalis, medial pterygoid
What is different about muscles of facial expression?
They move the skin rather than a joint
What is the difference between sphincters and dilators?
Sphincter - closes
Dilator - opens
What is the sternocleidomastoid?*
Location: sternum to below the ear
Action: rotate the head, flexes the neck, extends the head
Accessory: elevate sternum during forced inhalation
Origin: manubrium of sternum, clavicular head
Insertion: mastoid process of temporal bone and lateral half of superior nuchal line of occipital bone
Why is the sternocleidomastoid muscle an important landmark?
Divides the neck into two major triangles
- anterior and posterior
What is the rectus abdominis?*
Location: “abs” extends entire length of anterior abdominal wall
Action: compress abdomen to aid in defecation, urination, forced exhalation, and childbirth, flexes vertebral column (lumbar portion)
RMA: flexes pelvis in the vertebral column
Origin: pubic crest and pubic symphysis
Insertion: cartilage of ribs 5-7 and xiphoid process
What are tendinous intersections?
Rectus abdominis is interrupted by three transverse fibrous bands of tissue
- give rise to the “six” pack abs
Why do some people have a 6 pack and some people have an 8 pack of abs?
Everyone has three transverse fibrous bands that intersect the rectus abdominis (tendinous intersections) but some people have a fourth below the level of the umbilicus
What is the external oblique?
Location: superficial muscle, sides of abs
Action: compress abdomen and flex vertebral column, rotate vertebral column
What is the internal oblique?
Location: intermediate flat muscle, extends at right angles to the external oblique
Action: compress abdomen and flex vertebral column, rotate vertebral column
What do the muscles of the anterolateral abdominal wall do?
Help contain and protect the abdominal viscera; flex, laterally flex, and rotate the vertebral column, compress the abdomen during forced exhalation, and produce the force required for defecation, urination, and childbirth
What is the diaphragm?
Location: separates thoracic and abdominal cavities
Action: powers breathing, contraction results in inhalation (moves down), relaxation results in exhalation (moves up)
What are the muscles of the anterolateral abdominal wall?
Skin, fascia, four pairs of muscles (external oblique, internal oblique, transversus abdominis, rectus abdominis)
What is the external intercostal?
Location: superficial layer, they run interiorly and anteriorly from the rib above to the rib below
Action: elevate the ribs during inhalation to help expand the thoracic cavity
(Run armpit to stomach)
What is the most important muscle for breathing?
Diaphragm
-external (elevate during inhalation) and internal (exhalation) intercostal muscles also aid in breathing
What are the three major openings in the diaphragm?
Aorta (aortic hiatus)
Esophagus (esophageal hiatus)
Inferior vena cava (caval opening)
What are the two groups of muscles that move the pectoral girdle?
Anterior
Posterior
What is the trapezius?*
Location: superficial back muscle, extends from the skull and vertebral column medially to the pectoral girdle laterally (between the shoulder blades)
Action: elevate the scapula, adduct scapula, depress scapula, rotate scapula
Origin: superior nuchal line of occipital bone, ligamentum nuchae, spines of C7-T12
Insertion: clavicle and acromion and spine of scapula
What is the levator scapulae?*
Location: narrow, elongated muscle in the posterior portion of the neck
Action: elevate the scapula and rotates it downward
Origin: transverse processes of C1-C4
Insertion: superior vertebral border of scapula
What is the rhomboid major?
Location: lie deep to the trapezius, pass inferiorly and laterally from the vertebrae to the scapula
Action: elevates and adducts scapula, rotates it downward, stabilizes scapula
What are the axial muscles of the shoulder joint?
Pectoralis major and latissimus dorsi
- originate on the axial skeletal instead of the scapula
What is the main action of the muscles that move the pectoral girdle?
Stabilize the scapula so it can function as a steady origin for most of the muscles that move the humerus
What is the pectoralis major?*
Location: large, thick, fan-shaped muscle that covers the superior part of the thorax and forms the anterior fold of the thorax
Action: adducts and medially rotates the arm at the shoulder joint, clavicular head flexes arm, sternocostal head extends flexed arm to side of trunk
Origin: clavicle, sternum, and costal cartilage (2-6 ribs)
Insertion: greater tubercle and lateral lip of intertubercular sulcus of humerus
What is the latissimus dorsi?
Location: broad, triangular shaped muscle located on the interior part of the back that forms most of the posterior wall of the axilla
Action: extends, adducts, and medially rotates arm at shoulder joint; draws arm inferiorly and posteriorly
RMA: elevates vertebral column and torso (pull-up)
What is the deltoid?*
Location: thick, powerful shoulder muscle that covers the shoulder joint and forms the rounded contour
Action: abduct, flex & medially rotate, extend & laterally rotate arm at shoulder joint
Origin: acromial extremity of clavicle, acromion of scapula, spine of scapula
Insertion: deltoid tuberosity of humerus
What is the subscapularis?
Location: large triangular muscle that fills the subscapular fossa of the scapula and forms a small part of the apex of the posterior wall of the axilla
Action: medially rotates arm at shoulder joint
What is the supraspinatus?*
Location: rounded muscle, on the supraspinous fossa of the scapula, lies deep to the trapezius
Action: assists deltoid muscles in abducting arm at shoulder joint
Origin: supraspinous fossa of scapula
Insertion: greater tubercle of humerus
-especially subject to wear and tear
What are the four muscles of the shoulder that help strengthen and stabilize the shoulder joint? What do their tendons form?
Subscapularis Supraspinatus Infraspinatus Teres minor - join scapula to humerus - their tendons form the rotator cuff
What is the infraspinatus?
Location: triangular muscle, infraspinous fossa of the scapula
Action: laterally rotates arm at shoulder joint
What is the teres major?
Location: thick, flattened muscle inferior to the teres minor, helps form part of the posterior wall of the axilla
Action: extends arm at shoulder joint and assists in adduction and medial rotation of arm at shoulder joint
What is the teres minor?
Location: cylindrical, elongated muscle, often inseparable from the infraspinatus, which lies along its superior border
Action: laterally rotates and extends arm at shoulder joint
What is a rotator cuff injury?
Strain or tear in the rotator cuff muscles (baseball pitchers)
What are the flexor muscles of the elbow joint?
Biceps brachii
Brachialis
Brachioradialis
What are the extensor muscles of the elbow joint?
Triceps brachii
Anconeus
What is the biceps brachii?*
Location: largest muscle, anterior surface of the arm, spans both should and elbow joint
Action: flexes forearm at elbow joint, supinates forearm at radioulnar joint, flexes arm at the shoulder joint
Origin: long head originates from tubercle above glenoid cavity of scapula, short head originates from coracoid process of scapula
Insertion: radial tuberosity of radius and bicipital aponeurosis
What is the brachialis?
Location: deep to the biceps brachii, most powerful flexor of the forearm, “workhorse”
Action:flexes forearm at elbow joint
What is the brachioradialis?
Location: lateral border of distal end of humerus to superior styloid process of radius
Action: flexes forearm at elbow joint; supinates and pronates forearm at radioulnar joints to neutral positions
- when quick action is required, or weight lifted slowly during flexion
What are the triceps brachii?*
Location: large muscle located on the posterior surface of the arm
Action: extends forearm at elbow joint and extends arm at shoulder joint
Origin: long head originates from infraglenoid tubercle (scapula), lateral head originates from lateral and posterior surface of humerus, medial head originates from entire posterior surface of humerus inferior to a groove for the radial nerve
Insertion: olecranon of ulna
What is the pronator teres?
Location: crosses inside of elbow (from humerus to radius)
Action: pronates forearm at radioulnar joint and weakly flexes forearm at elbow joint
What is the supinator?
Location: top of elbow joint, humerus to radius
Action: supinates forearm at the radioulnar joint
- when you twist a corkscrew
What is the flexor carpi radialis?*
Location: center portion of forearm (anterior side)
Action: flexes and abducts hand (radial deviation) at wrist joint
Origin: medial epicondyle of humerus
Insertion: second and third metacarpals
What is the muscle group called that moves the digits?
Extrinsic muscles of the hand
b/c they originate outside the hand and insert into it
What are the two categories that the forearm muscles are divided into?
- Anterior (flexor) compartment (originate on humerus, insert on carpals, metacarpals, and phalanges)
- Posterior (extensor) compartment (originate on humerus, insert on metacarpals and phalanges)
What is the order (lateral to medial) of the superficial anterior compartment muscles?
- flexor carpi radialis
- palmaris longus
- fleor capi ulnaris
What is the palmaris longus?
Location: towards the pinky side, beside flexor carpi radialis
Action: weakly flexes hand at wrist joint
What is the flexor carpi ulnaris?*
Location: towards the pinky side, beside palmaris longus
Action: flexes and adducts hand (ulnar deviation) at wrist joint
Origin: medial epicondyle of humerus and superior posterior border of ulna
Insertion: pisiform, hamate, and base of 5th metacarpal
What is the flexor digitorum superficialis?*
Location: deep to the flexor carpi radialis, palmaris longus and flexor carpi ulnaris, largest superficial muscle of the forearm
Action: flexes middle phalanx of each finger at the proximal interphalangeal joint, proximal phalanx of each finger at metacarpalphalangeal joint and hand at wrist joint
Origin: medial epicondyle of humerus, coronoid process of ulna, and ridge along lateral margin or anterior surface (anterior oblique line) of radius
Insertion: middle phalanx of each finger
What is the extensor carpi radialis longus?
Location: from lateral supracondylar ridge of humerus to 2nd metacarpal
Action: extends and abducts hang at wrist joint (ulnar deviation)
What is the extensor digitorum?*
Location: middle of the forearm, posterior side
Action: extends distal and middle phalanges of each finger at interphalangeal joints, proximal phalanx of each finger at metacarpophalangeal joint and hand at wrist joint
Origin: lateral epicondyle of humerus
Insertion: distal and middle phalanges of each finger
What is the extensor carpi ulnaris?*
Location: posterior side, runs from elbow to pinky
Action: extends and adducts hand at wrist joint (ulnar deviation)
Origin: lateral epicondyle of humerus and posterior border of ulna
Insertion: 5th metacarpal
What movements do the intrinsic muscles of the hand produce?
Weak but intricate and precise movements of the digits
What are the three groups of intrinsic muscles of the hand?
- Thenar
- Hypothenar
- Intermediate
What does the most dexterity of the hand depend on?
The movements of the thumb
What are the general activities of the hand?
Free motion, power grip, precision handling, and pinch
What are the 5 principal movements of the thumb?
- Flexion - movement across palm
- Extension - back to anatomical postion
- Abduction - up and away from palm
- Adduction - towards the back of the hand
- Opposition - moves thumb to meet a finger
What is the most distinctive digital movement of humans?
Opposition of thumb.
What are the muscles of the erector spinae muscle group?
- Iliocostalis group (lateral)
- Longissimus group (intermediate)
- Spinalis group (medial)
What are the actions and location of the erector spinae muscles?
Location: largest mass muscle of the back, forms prominent bulge on either side of the vertebral column
Action: Extend the vertebral column, flexion, lateral flexion, rotatation of vertebral column, maintains lumbar curve
How are the upper limb muscles different from the lower limb muscles?
Upper limbs are characterized by versatility of movement
Lower limbs function in stability, locomotion, and maintenance of posture
What are the psoas major and iliacus commonly known as?
The iliopsoas muscle
they share a common insertion, lesser trochanter on femur
What is the psoas major?*
Location: lumbar vertebrae to hip bone
Action: Flex thigh at hip joint, rotate thigh laterally, flex trunk at hip joint (as in sitting up)
Origin: transverse processes and bodies of lumbar vertebrae
Insertion: lesser trochanter of femur
What is the iliacus?
Location: inside of hip bone
Action: Flex thigh at hip joint, rotate thigh laterally, flex trunk at hip joint (as in sitting up)
What are the three gluteal muscles?
- Gluteus maximus
- Gluteus medius
- Gluteus minimus
What is the gluteus maximus?*
Location: largest and heaviest, chief extensor of femur, butt muscle
Action: Extends thigh at hip joint, and laterally rotates thigh, helps lock knee in extension. RMA - extends torso
Origin: iliac crest, sacrum, coccyx, aponurosis of sacrospinalis
Insertion: iliotibial tract of fascia lata and superior lateral part of linea aspera (gluteal tuberosity) under the greather trochanter of femur
What is the gluteus medius?
Location: above the gluteus maximus, but deep to the gluteus maximus
Action: abducts thigh at hip joint and medially rotates thigh
*where you get injections
What is the adductor longus?
Location: medial aspect of thigh
Action: adducts and flexes thigh at hip joint and rotates thigh. RMA - extends thigh
Why are adductor muscles unique?
They cross the thigh obliquely from an anterior origin to a posterior insertion. As a result, they laterally rotate the hip joint when the foot is off the ground but medially rotate the hip joint when the foot is on the ground
What is the adductor magnus?
Location: medial aspect of thigh, posterior to adductor longus
Action: adducts thigh at hip joint and rotates thigh, anterior part flexes thigh at hip joint and posterior part extends thigh at hip joint
What is the quadriceps femoris?
Location: anterior portion of thigh and sides of thigh
Action: all four heads extend leg at knee joint, rectus femoris muscle acting alone also flexes thigh at hip joing
What are the 4 muscles of the quadriceps femoris?
- Rectus femoris
- Vastus lateralis
- Vastus medialis
- Vastus intermedius
What is the rectus femoris?*
Location: anterior portion of femur
Action:all four heads extend leg at knee joint, rectus femoris muscle acting alone also flexes thigh at hip joing
Origin: anterior inferior iliac spine
Insertion: patella via quadriceps tendon and then tibial tuberosity via patellar ligament
What is the vastus lateralis?
Location: lateral aspect of femur
Action: all four heads extend leg at knee joint, rectus femoris muscle acting alone also flexes thigh at hip joing
What is the vastus medialis?
Location: medial aspect of femur
Action: all four heads extend leg at knee joint, rectus femoris muscle acting alone also flexes thigh at hip joing
What is the vastus intermedius?
Location: deep to the rectus femoris
Action: all four heads extend leg at knee joint, rectus femoris muscle acting alone also flexes thigh at hip joing
What is the sartorius?
Location: long, narrow muscle from ilium to medial side of the tibia
Action: weakly flexes leg at knee joint, weakly flexes, abducts and laterally rotates thigh at hip joint
What is also know as the tailor’s muscle?
Sartorius
What are the three muscles of the hamstrings? What is the action of the hamstrings?
- Biceps femoris
- Semitendinosus
- Semimembranosus
Action: Flexes leg and extends thigh
What is the biceps femoris?*
Location: posterior aspect of femur (in the middle)
Action: flexes leg at knee joint and extends thigh at hip joint
Origin: long head arises from ischial tuberosity, short head arises from linea aspera of femur
Insertion: head of fibula and lateral condyle of tibia
What is the semitendinosus?
Location: medial to biceps femoris
Action: flexes leg at knee joint and extends thigh at hip joint
What is the semimembranosus?
Location: deep to semitendinosus
Action: flexes leg at knee joint and extends thigh at hip joint
What is the tibialis anterior?*
Location: anterior surface of tibia
Action: dorsiflexes foot at ankle joint and inverts (supinates) foot at intertarsal joints
Origin: lateral condyle and body of tibia and interosseous membrane
Insertion: 1st metatarsal and 1st (medial) cuniform
What is the extensor digitorum longus?*
Location: inbetween tibialis anterior and fibularis longus
Action: dorsiflexes foot at ankle joint and extends distal and middle phalanges of each toe at interphalangeal joints and proximal phalanx of each toe at metatarsophalangeal joint
Origin: lateral condyle of tibia, anterior surface of fibula, and interosseous membrane
Insertion: middle and distal phalanges of toes (2-5)
What is the fibularis (peroneus) longus?
Location: lateral aspect of tibia
Action: dorsiflexes foot at ankle joint and everts (pronates) foot at intertarsal joints
What is the gastrocnemius?*
Location: most superficial, big “calf” muscle
Action: plantar flexes foot at ankle joint and flexes leg at knee joint
Origin: lateral and medial condyles of femur and capsule of knee
Insertion: calcaneus by way of calcaneal tendon (achilles)
What is the soleus?
Location: lies deep to the gastrocnemius
Action: plantar flexes foot at ankle joint
What is the flexor digitorum longus?*
Location: medial aspect of tibia
Action: plantar flexes foot at ankle joint, flexes distal and middle proximal phalanx of each toe at interphalangeal joints/metatarsophalangeal joint
Origin: middle 3rd of posterior surface of tibia
Insertion: distal phalanges of toes 2-5
What do the muscles of the anterior compartment of the leg do?
Dorsiflex the foot
What is the strongest tendon of the body?
Achilles tendon (calcaneal)
What is the transverse abdominis?
Location: deep muscle of the abdomen, fascicles directed transversely
Action: compresses abdomen
What is the internal intercostal?
Location: occupy intermediate layer, run at right angles to the external intercostal, interiorly and posteriorly from rib above to rib below
Action: draw adjacent ribs together during forced exhalation to help decrease size of the thoracic cavity
(Run sternum to hip)
