Chapter 11 The Muscular System BIO 210 Lab

Chapter 11: The Muscular System BIO 210 Lab Instructor: Dr. Rebecca Clarke

Muscular System Includes all voluntary skeletal muscles Approximately 700 skeletal muscles “Newest” muscle Identified in 1996 Sphenomandibularis muscle Assists with mastication

Functions of Skeletal Muscles Attach to skeleton, produce motion Support soft tissue Form slings or sheets between bony elements Guard an entrance/exit Completely encircle the opening

Skeletal Muscle Organization Muscle cells (fibers) are organized in bundles (fascicles) Muscle organization affects power, range, and speed of muscle movement Arrangement of fascicles, shape and/or appearance provide clues to primary function

Skeletal Muscles and the Skeletal System Skeletal muscles have a direct or indirect association with the skeletal system Attach to: Bony processes via tendons Aponeuroses (singl …sis) = broad, flat sheets of tendinous connective tissue

Organization of Skeletal Muscle Fibers 4 patterns of fascicle organization: Parallel Convergent Pennate Circular

Parallel Muscles Fibers parallel to long axis of muscle plump, spindle-shape with: Central body Tendons at one or both ends When muscle contracts, gets shorter, larger in diameter Most skeletal muscles are this type Figure 11– 1 a

Convergent Muscles Broad, fan-shaped area converges on attachment site Versatile because muscle fibers pull in different directions depending on stimulation Figure 11– 1 b

Pennate Muscles Unipennate: fibers on 1 side of tendon Bipennate: fibers on both sides Multipennate: tendon branches in muscle Figure 11– 1 c, d, e

Circular Muscles Also called sphincters Fibers encircle opening Open and guard entrances/exits of external/internal passageways, e. g. , digestive, urinary tracts contraction diameter of opening Figure 11– 1 f

Origins and Insertions Muscles have 1 stationary point of attachment (origin) 1 moving point of attachment (insertion) Most muscles originate or insert on the skeleton Origin is usually proximal to insertion

Action Movement muscle produces when it contracts Body movements e. g. , flexion, extension, adduction, etc. Described in terms of bone, joint, or region

How does the name of a muscle help identify its location, appearance, or function?

Names of Skeletal Muscles Correct name of muscle includes the term “muscle” Exceptions: Platysma Diaphragm

Descriptive Names for Skeletal Muscles • • • Fascicle organization Location in the body Origin and insertion Relative position Structural characteristics Action

Fascicle Organization Describes fascicle orientation within muscle: i. e. , rectus (straight), oblique (diagonal), transversus (transverse)

Location in the Body Identifies body regions: e. g. , temporalis muscle

Origin and Insertion First part of name indicates origin Second part of name indicates insertion, e. g. , : coracobrachialis muscle, sternocleidomastoid

Relative Position External (superficialis): Visible at body surface Internal (profundus): Deep muscles Extrinsic: Muscles outside an organ Intrinsic: Muscles inside an organ

Structural Characteristics Number of tendons/head: bi = 2, tri = 3 Biceps brachii Shape: Trapezius, deltoid, rhomboid

Names for Muscle Size (1 of 2) Longus = long Longissimus = longest Teres = long and round Brevis = short Magnus = large

Names for Muscle Size (2 of 2) Major = larger Maximus = largest Minor = small Minimus = smallest

Action Movements: e. g. , flexor, extensor, levator Occupations or habits: e. g. , risor = laughter risorius e. g. , sartor = tailor sartorius

Naming Skeletal Muscles Table 11– 1 (1 of 2)

Axial and Appendicular Muscles Figure 11– 3 a

Axial and Appendicular Muscles Figure 11– 3 b

Divisions of the Muscular System • Axial muscles: • Position head and spinal column Move rib cage 60% of skeletal muscles Appendicular muscles: Support pectoral and pelvic girdles Support limbs 40% of skeletal muscles

Muscles of the Head Epicranium (scalp) Epicranial aponeurosis (galea aponeurotica) CT sheet between frontalis and occipitalis Frontalis (frontal belly of occipito-frontalis) Covers forehead; raises eyebrows, wrinkles forehead Figure 11– 4 b

Muscles of the Head Occipitalis (occipital belly of occipitofrontalis) Covers inferior occipital area; tenses and retracts scalp Temporoparietalis Tenses scalp, moves auricle of ear Figure 11– 4 a

Muscles of the Head Orbicularis oculi Surrounds eye (external) Closes eye (internal) Nasalis bridge of nose movements Figure 11– 4 b

Muscles of the Head Orbicularis oris Surrounds mouth Compresses, purses lips Depressor anguli oris Pulls down corner of mouth From body of mandible to angle of mouth Mentalis Medial on chin Protrudes lower lip Figure 11– 4 b

Muscles of the Head Zygomaticus (minor and major) From zygomatic arch to mouth Buccinator Wide, horizontal muscle in cheek Chewing, sucking, compresses cheeks Masseter Runs vertically over buccinator, covers lateral side of ramus of mandible Elevates mandible (closes jaw) Strongest jaw muscle Figure 11– 4 a

Muscles of the Head Risorius From parotid salivary gland to angle of mouth (crosses buccinator and masseter) Draws corner of mouth to side (grimace) Temporalis Large, fan-shaped, in temporal area deep to temporoparietalis Assists in elevating mandible Platysma Covers inferior mandible and anterior surface of neck Visible inferior to risorius Tenses skin of neck; depresses mandible (opens jaw) Figure 11– 4 b

Muscles of the Neck Sternocleidomastoid Long muscle at lateral side of neck (under platysma) Extends from clavicle and sternum to mastoid region of temporal bone Flexes neck down Figure 11– 4 a

Muscles of the Neck Scalenes (Fig 11 -10 b) 3 muscles on each side, from transverse processes of cervical vertebrae to 1 st and 2 nd ribs Flex neck laterally, assist in breathing (elevate ribs) Figure 11– 10 b, c

Muscles of the Neck and Back Trapezius Large kite-shaped muscles on back and neck Extend neck, elevate clavicle, move scapula upward Splenius capitis Deep to trapezius at back of neck; rotate head Figure 11– 13 a

Muscles of the Neck and Back Levator scapulae Deep to trapezius at lateral side of neck Lift scapulae Figure 11– 13 a

Muscles of the Anterior Torso Pectoralis major Large fan-shaped chest muscle Shoulder movements Pectoralis minor Under p. major Shoulder and scapula movements Serratus anterior Inferior to pectoralis minor Shoulder and scapula movements Figure 11– 13 b

Muscles of the Anterior Torso Intercostals In intercostal spaces (between ribs) Respiration External intercostals Fibers run medially from superior rib to inferior rib Elevate ribs (for external think: putting hands in front pockets) Internal intercostals Fibers run laterally from superior rib to inferior rib deep to external intercostals Depress ribs (for internal think: putting hands in back pockets) Figure 11– 14 b

Muscles of the Anterior Torso Obliques External obliques Superficial, fibers run medially and inferiorly Depresses ribs, compresses abdomen, bends and rotates spine Internal obliques Deep to external oblique, fibers run medially and superiorly from iliac crest Same action as above Figure 11– 13 b

Muscles of the Anterior Torso Rectus abdominis Deep to internal oblique, runs vertically near midline Depresses ribs, flexes spine Divided by linea alba Linea alba Aponeurosis at midline (from xiphoid process to symphysis pubis) Longitudinally divides rectus abdominis Rectus sheath A sheath formed by the aponeuroses of other abdominal muscles, within which the rectus abdominis moves Tendinous intersections separate parts of muscle Figure 11– 3 a

Muscles of the Ventral Cavities Subcostal Oblique, on deep side of posterior thoracic wall; form straps between ribs

Muscles of the Ventral Cavities Transversus abdominis Deepest, fibers run transversally Tightens abdominopelvic wall; protects viscera Figure 11– 11 a, c

Muscles of the Vertebral Column Quadratus lumborum Posterior and lateral to psoas major Attaches to last rib and lumbar vertebrae Both sides together, depresses ribs; alone, each side laterally flexes vertebral column Figure 11– 10 a

Muscles that Move the Thigh Psoas – originate on lumbar vertebrae Major – medial to quadratus lumborum Minor – medial and anterior to p. major Figure 11– 19 c, d

Muscles that Move the Thigh Iliacus – triangular sheet across iliac fossa Iliopsoas – iliacus + psoas major Figure 11– 19 c, d

Diaphragm Dome-shaped, muscular partition Divides thoracic and abdominopelvic cavities Central tendon, inferior vena caval hiatus, esophageal hiatus, aortic hiatus Major role in respiration Figure 11– 11 a, b

Perineum Muscular sheet that forms the pelvic floor

Muscles of the Pelvic Floor Figure 11– 12 a

Muscles of the Pelvic Floor Figure 11– 12 b

Functions of the Perineum • • • Supports organs of pelvic cavity Flexes sacrum and coccyx Controls movement of materials through urethra and anus

Muscles of the Posterior Torso Trapezius, splenius capitis, levator scapulae (see previous description) Latissimus dorsi – inferior to trapezius; broadest muscle of back; moves humerus Figure 11– 13 a

Muscles of the Posterior Torso Rhomboid(eus) – deep to trapezius between scapula and spine; move scapula Rhomboid minor and major Figure 11– 14 a

Muscles of the Posterior Torso Supraspinatus – in supraspinous fossa of scapula; abduction at shoulder Infraspinatus – in infraspinous fossa of scapula; lateral shoulder rotation Figure 11– 15 b

Muscles of the Posterior Torso Subscapularis – in subscapular fossa; medial shoulder rotation Figure 11– 15 a

Muscles of the Posterior Torso Teres major – runs horizontally inferior to infraspinatus, from scapula to humerus Teres minor – runs horizontally superior to teres major and inferior to infraspinatus; from scapula to humerus Figure 11– 15 b

Muscles of the Posterior Torso Serratus posterior – forms jagged edge, from vertebrae to ribs Internal oblique (see description above) Figure 11– 13 a

Muscles of the Upper Extremities

Muscles of the Upper Extremities: Brachium Deltoid - large, triangular muscle at top of shoulder; moves humerus Biceps brachii – anterior/lateral side of arm, 2 heads; flexes elbow and shoulder, supination Figure 11 -15 a

Muscles of the Upper Extremities: Brachium Brachialis - inferior to deltoid on lateral side of arm between biceps and triceps brachii; flexes elbow Biceps brachii – anterior/lateral side of arm, 2 heads; flexes elbow and shoulder, supination Figure 11– 16 b

Muscles of the Upper Extremities: Brachium Triceps brachii (Fig 11 -15 b) – posterior side of arm, 3 heads; extends elbow Coracobrachialis (Fig 11 -16) – superior lateral side of arm, between 2 brachii Figure 11– 15 a

Muscles of the Upper Extremities: Antebrachium - Anterior Brachioradialis – inferior to brachialis on lateral side of forearm; flexes elbow Pronator teres – antecubital region of forearm, diagonal orientation; pronates forearm Flexor carpi radialis – medial to brachioradialis, inferior to pronator teres; flexes wrist, abducts hand Figure 11– 16 b

Muscles of the Upper Extremities: Antebrachium - Anterior Palmaris longus – medial to above; flexes wrist Flexor carpi ulnaris – medial to above and adjacent to ulna; flexes, adducts wrist Figure 11– 16 b

Muscles of the Upper Extremities: Antebrachium - Posterior Extensor carpi ulnaris – adjacent to ulna, lateral to flexor carpi ulnaris; extends and abducts wrist Extensor digitorum – lateral to above; extends fingers II-V Extensor carpi radialis brevis – along upper lateral side of above Figure 11– 16 a

Muscles of the Upper Extremities: Antebrachium - Posterior Extensor carpi radialis longus – along medial side of brachioradialis; extends and abducts wrist FYI [Supinator – antecubital region of forearm deep to brachioradialis; supinates forearm] Figure 11– 16 a

Muscles that Move the Hand Fingers Also called extrinsic muscles of the hand Lie entirely within forearm Only tendons cross wrist (in synovial tendon sheaths)

Muscles that Move the Hand Fingers Figure 11– 17 a, b

Intrinsic Muscles of the Hand Figure 11– 18 a

Muscles of the Lower Extremities

Muscles of the Pelvis and Upper Leg Iliotibial tract – dense CT sheet on lateral thigh Gluteus - covers lateral surfaces of ilia Gluteus Maximus Medius Minimus Tensor fasciae latae - small tensor muscle of fascia, stabilizes iliotibial tract, laterally supports knee Figure 11– 19 a, b

Muscles of the Pelvis and Upper Leg – Anterior, Extensors Quadriceps femoris – anterior thigh area, strongest muscle group in body; extends knee; made of 4 muscles Vastus lateralis – anterior to iliotibial tract, lateral to rectus femoris Rectus femoris – runs “straight” vertically along anterior thigh; superior portion between tensor fasciae latae and sartorius Vastus medialis – medial to rectus femoris FYI [Vastus intermedius – deep, hidden by rectus femoris] Sartorius – long, slender, oblique; longest muscle in body; tailor’s muscle Figure 11– 20 b

Muscles of the Pelvis and Upper Leg – Medial, Adductors Pectineus – inferior and medial to iliopsoas Adductor longus – inferior to pectineus and medial to sartorius Gracilis – vertical along medial side of thigh and medial to adductor longus Adductor magnus (Fig 11 -20 a) – superior portion posterior to gracilis Figure 11– 20 b

Muscles of the Pelvis and Upper Leg – Posterior, Flexors (Hamstrings) Adductor magnus (see previous slide) Semimembranosus – lateral to adductor magnus (superior) and gracilis (inferior), medial and deep to semitendinosus Semitendinosus – superficial, lateral to semimembranosus Biceps femoris – lateral to semitendinosus, posterior to iliotibial tract Figure 11– 20 a

Muscles of the Lower Leg - Flexor Tibialis anterior – along anterior, lateral side of tibia Figure 11– 21 a, b

Muscles of the Lower Leg - Extensors Fibularis (peroneus) longus – along lateral side of fibula Fibularis (peroneus) brevis – inferior and deep to fibularis longus Figure 11– 21 a, b

Muscles of the Lower Leg - Extensors Extensor digitorum longus – lateral to tibialis anterior; extends toes II-V Gastrocnemius – calf muscle (2 heads) Soleus – deep (lateral and medial) to gastrocnemius Figure 11– 21 a, b

Muscles of the Lower Leg – large tendon from gastrocnemius and soleus to calcaneus Calcaneal (Achilles) tendon Figure 11– 21 a, b

Intrinsic Muscles of the Foot Figure 11– 22 a