Ch 10- The Muscular System

• Movement

• stability/posture

• control of openings/passages

• heat production

• hormone secretion

• glycemic control

What are the main functions of muscle tissue?

Skeletal, cardiac, smooth

• all convert ATP into mechanical energy.

What are the three types of muscle tissue and their main function?

myology

The study of the muscular system.

Endomysium → Perimysium → Epimysium → Fascia.

List the connective tissue layers in a skeletal muscle from deep to superficial.

fascicle

A bundle of muscle fibers wrapped in perimysium.

Determines strength and direction of pull

How does fascicle orientation affect muscle function?

• Fusiform

• parallel triangular (convergent)

• pennate (uni-, bi-, multipennate)

• circular (sphincters)

Name the types of fascicle arrangements.

muscle compartment

Group of functionally related muscles plus nerves and blood vessels, enclosed by fascia.

Direct muscle attachments

muscle fibers attach to bone with little separation.

indirect muscle attachments

muscle connects to bone via tendon or aponeurosis.

retinaculum

A connective tissue band that tendons from separate muscles pass under.

Sometimes the "stationary" and "moving" ends are not consistent; proximal/distal or superior/inferior is preferred.

What is the issue with calling attachments "origin" and "insertion"?

• Intrinsic—entirely within a region.

• Extrinsic—acts on a region but originates elsewhere.

Distinguish intrinsic vs. extrinsic muscles

Prime mover, synergist, antagonist, fixator.

Name four functional groups of muscles.

• Identifies which nerve stimulates a muscle

• helps diagnose nerve or spinal injuries.

What is the importance of innervation in muscles?

• Capillaries in endomysium reach every fiber

• ~1.24 L/min at rest, increases during exercise.

How is blood supplied to skeletal muscles?

Based on location, structure, size, shape, action, or attachments; often Latin-based.

How are muscles named?

• Occipitofrontalis

  • frontal belly elevates eyebrows, occipital belly retracts scalp

What are the main muscles of the scalp?

• Orbicularis oculi (closes eye)

• levator palpebrae superioris (opens eye).

Muscles around the eyes and nose?

• Orbicularis oris: puckers lips, kissing muscle

• mentalis: pouting muscle; elevates/protrudes lower lips and wrinkles chin

• buccinator: cheek muscle, compresses cheek

• platysma: tenses lower face; makes scared/ yikes face

Muscles around the mouth and chin?

• Temporalis

• masseter

• medial and lateral pterygoids

Main muscles of chewing?

suprahyoid muscles

Aid chewing, swallowing, and speaking; elevate or depress mandible and hyoid.

infrahyoid muscles

Fix or depress hyoid/larynx; assist suprahyoid muscles.

Superior, middle, inferior—drive food into esophagus.

Three pharyngeal constrictors?

• Flexion, extension, lateral flexion, rotation

• can be ipsilateral or contralateral depending on attachment.

Actions of neck muscles?

• Sternocleidomastoid (rotates opposite side, flexes neck bilaterally)

• scalenes (ipsilateral flexion, contralateral rotation)

Flexors of the neck?

• Trapezius

• splenius capitis/cervicis

• semispinalis capitis/cervicis

  • extend, laterally flex, or rotate neck

Extensors of the neck?

• Diaphragm (flattens to inhale)

• external intercostals (elevate ribs)

• internal/intermost intercostals (depress ribs)

Muscles of respiration?

External oblique, internal oblique, transversus abdominis.

Layers of abdominal wall muscles?

Support viscera, stabilize spine, compress abdominal contents.

Functions of abdominal muscles?

• Paired vertical muscles

• flex waist

• segmented by tendinous intersections (“six-pack”)

• enclosed by rectus sheath

• linea alba and linea semilunaris are landmarks

Rectus abdominis structure?

prime mover (agonist)

The muscle that produces the main force for a movement.
- Example: Brachialis flexes the elbow.

synergist muscle

A muscle that assists the prime mover.
Example: Biceps brachii assists the brachialis in elbow flexion.

antagonist muscle

A muscle that opposes the action of the prime mover.
Example: Triceps brachii extends the elbow while brachialis flexes it.

fixator muscle

A muscle that stabilizes a bone or joint so another muscle can act.
Example: Rhomboid muscles fix the scapula during biceps contraction.

• Intrinsic muscles are entirely within the region they act on (e.g., hand muscles).

• Extrinsic muscles act on a region but originate elsewhere (e.g., forearm muscles moving the hand).

What is the difference between intrinsic and extrinsic muscles?

• Direct: Muscle fibers attach directly to bone with little separation.

• Indirect: Muscle attaches via a tendon or aponeurosis.

What are direct and indirect muscle attachments?

fascia

a sheet of connective tissue between muscles.

• Fusiform

• Parallel

• Triangular (convergent)

• Pennate

• Circular (sphincters)

Name the types of fascicle arrangements

Fusiform

thick in middle, tapered ends (strong, moderate range of motion).

Parallel

uniform width (long contraction, less force).

Triangular (convergent)

broad base to narrow end (strong, versatile).

Pennate

feather-shaped, more fibers = stronger contraction.

• Unipennate: one side of tendon

• Bipennate: both sides of tendon

• Multipennate: bunches converge to one point

Circular (sphincters)

encircle openings, constrict when contracting.

Extension, rotation, and lateral flexion of the vertebral column.

What actions do muscles of the back generally perform?

Latissimus dorsi and trapezius

• involved in upper limb movement.

Name two prominent superficial back muscles and their general function.

Serratus posterior superior and inferior

• extend from vertebrae to ribs and aid in deep breathing.

Name deep back muscles that aid in respiration.

• Iliocostalis (most lateral)

• longissimus (medial to iliocostalis)

• spinalis (most medial);

  • Function: Lateral flexion and extension of spine.

What are the three columns of the erector spinae and their location?

Extension and contralateral rotation of spine.

Action of semispinalis thoracis?

• Unilateral: ipsilateral flexion of spine

• Bilateral: extension of spine.

Action of quadratus lumborum?

Stabilize vertebrae and maintain posture; connect adjacent vertebrae.

Function of multifidus muscles

• Ischiocavernosus—maintains erection of penis/clitoris

• Bulbospongiosus—expels residual urine, aids erection

• Superficial transverse perineal—stabilizes perineal body

Name three muscles in the superficial perineal space and their functions.

• Deep transverse perineal—anchors perineal body

• Compressor urethrae (females)—aids in urine retention

• External anal sphincter—retains feces

Name muscles in the deep perineal space and their functions.

• Inguinal (viscera through inguinal canal)

• hiatal (stomach through diaphragm)

• umbilical (viscera through navel)

Name three common hernias.

Rotation, elevation, depression, protraction, retraction of scapula.

What movements do muscles of the pectoral girdle produce?

• Pectoralis minor—protracts scapula

• Serratus anterior—protracts scapula

Name anterior muscles of the pectoral girdle and their actions.

• Trapezius—elevation, depression, retraction

• Levator scapulae—elevates scapula

• Rhomboid major/minor—retract scapula

Name posterior muscles of the pectoral girdle and their actions.

Supraspinatus, Infraspinatus, Teres minor, Subscapularis

• stabilize humerus in glenoid cavity.

Name the rotator cuff muscles and their primary function.

• Deltoid—flexion, extension, abduction, medial/lateral rotation

• Teres major—extension, medial rotation

• Coracobrachialis—flexion, medial rotation

• Pectoralis major—flexion, adduction, medial rotation

• Latissimus dorsi—extension, adduction, medial rotation

Name muscles acting on the shoulder and their actions.

Flexion, extension, pronation, supination

What four movements occur at the elbow and forearm?

• Brachialis (prime mover)

• biceps brachii

• brachioradialis (synergists)

Name the elbow flexors.

Triceps brachii (three heads)

Name the prime mover of elbow extension.

• Pronation: pronator quadratus (prime), pronator teres (assists)

• Supination: supinator

Name muscles responsible for pronation and supination.

• Flexor carpi radialis—wrist flexion, radial deviation

• Flexor carpi ulnaris—wrist flexion, ulnar deviation

• Flexor digitorum superficialis—flexes wrist, MP, IP joints

• Palmaris longus—anchors palmar fascia/skin

Name anterior forearm flexors (superficial) and their actions.

• Flexor digitorum profundus—flexes wrist, MP, IP joints (sole flexor of distal IP)

• Flexor pollicis longus—flexes thumb phalanges

Name anterior forearm flexors (deep) and their actions.

Extends the wrist and causes radial deviation.

What is the action of extensor carpi radialis longus?

extensor carpi radialis brevis

Extends the wrist and causes radial deviation.

extensor digitorum

Extends the wrist, MP, and IP joints of fingers 2-5.

extensor digiti minimi

Extends the wrist and joints of the little finger.

extensor carpi ulnaris

Extends the wrist and causes ulnar deviation.

Abducts and extends the thumb.

What is the action of abductor pollicis longus?

Extends the proximal phalanx of the thumb.

What is the action of extensor pollicis brevis?

Extends the distal phalanx of the thumb.

What is the action of extensor pollicis longus?

Extends the index finger and assists wrist extension.

What is the action of extensor indicis?

carpal tunnel

A tight space under the flexor retinaculum where flexor tendons and the median nerve pass.

carpal tunnel syndrome

Compression of the median nerve in the carpal tunnel causing tingling, weakness, or pain in the hand.

Abducts the thumb.

What does abductor pollicis brevis do?

Flexes the thumb at the MP joint.

What does flexor pollicis brevis do?

Flexes the first metacarpal of the thumb (opposition).

What does opponens pollicis do?

Draws the thumb toward the palm (adduction).

What does adductor pollicis do?

Abducts the little finger.

What does abductor digiti minimi do

Flexes the little finger at the MP joint.

What does flexor digiti minimi brevis do?

Flexes the fifth metacarpal.

What does opponens digiti minimi do?

Abduct fingers 2-4; flex MP joints and extend IP joints.

What is the action of the dorsal interossei?

Adduct fingers 2, 4, 5; flex MP joints and extend IP joints

What is the action of the palmar interossei?

Flex MP joints and extend IP joints of fingers 2-5.

What is the action of the lumbricals in the hand?