MUSCLES OF THE BODY Ch 11 Leonardo Da

MUSCLES OF THE BODY Ch 11 Leonardo Da Vinci Human Anatomy Sonya Schuh-Huerta, Ph. D.

Muscles of the Body • Skeletal muscles – Produce movements • General principles of leverage • Muscles act with or against each other • Criteria used in naming muscles

Naming the Skeletal Muscles • Location – Example the brachialis is located on the arm (brachium) • Shape – Example the deltoid is triangular • Relative size – Maximus, minimus, & longus indicate size – Example gluteus maximus is the large one & gluteus minimus is the small one

Naming the Skeletal Muscles • Direction of fascicles & muscle fibers – Name tells direction in which fibers run – Example rectus abdominis & transversus abdominis (rectus = straight up; transverse across or at right angle to midline) • Location of attachments name reveals point of origin & insertion – Example brachioradialis

Naming the Skeletal Muscles • Number of origins – 2, 3, or 4 origins – Indicated by the words biceps (2), triceps (3), & quadriceps (4) • Action – Action can be part of the muscle’s name – Indicates type of muscle movement • Flexor, extensor, adductor, or abductor (ie. extensor digitorum)

Arrangement of Fascicles in Muscles • Skeletal muscles consist of fascicles – Fascicles arranged in different patterns – Fascicle arrangement tells about action of a muscle

Arrangement of Fascicles in Muscles • Types of fascicle arrangement – Parallel fascicles run parallel to the long axis of the muscle • Strap-like sternocleidomastoid • Fusiform biceps brachii

Arrangement of Fascicles in Muscles • Types of fascicle arrangement – Convergent • Origin of the muscle is broad • Fascicles converge toward the tendon of insertion • Example Pectoralis major

Arrangement of Fascicles in Muscles • Types of fascicle arrangement – Pennate • Unipennate fascicles insert into one side of the tendon • Bipennate fascicles insert into the tendon from both sides • Multipennate fascicles insert into one large tendon from all sides

Arrangement of Fascicles in Muscles • Circular – Fascicles are arranged in concentric rings • Surround external body openings • Sphincter general name for a circular muscle • Examples – Orbicularis oris & orbicularis oculi

Arrangement of Fascicles in Muscles (a) (b) (a) Circular (orbicularis oris) (e) (c) (b) Convergent (pectoralis major) (d) (f) (g) (c) Fusiform (biceps brachii) (d) Parallel (sartorius) (e) Multipennate (deltoid) (f) Bipennate (rectus femoris) (g) Unipennate (extensor digitorum longus)

Lever Systems: Bone-Muscle Relationships • Movement of skeletal muscles involves leverage – Lever a rigid bar that moves – Fulcrum a fixed point – Effort applied force – Load resistance

Lever Systems Effort x length of effort arm = load x length of load arm (force x distance) = (resistance x distance) Effort 10 kg 0. 25 cm Effort 25 cm Fulcrum 10 x 25 = 1000 x 0. 25 250 = 250 Load 1000 kg Load (a) Mechanical advantage with a power lever Fulcrum

Lever Systems: Bone-Muscle Relationships • Bones act as levers • Joints act as fulcrums • Muscle contraction provides effort – Applies force where muscle attaches to bone • Load bone, overlying tissue, & anything being lifted

Lever Systems: Bone-Muscle Relationships • Levers allow a given effort to – Move a heavier load – Move a load farther

Lever Systems: Bone-Muscle Relationships • First-class lever – Effort applied at one end – Load is at the opposite end – Fulcrum is located between load & effort (a) First-class lever Arrangement of the elements is load-fulcrum-effort. Load Effort L Fulcrum Load L Load Fulcrum Example: scissors Effort In the body: A first-class lever system raises your head off your chest. The posterior neck muscles provide the effort; the atlanto-occipital joint is the fulcrum; and the weight to be lifted is the facial skeleton.

Lever Systems: Bone-Muscle Relationships • Third-class lever – Effort is applied between the load & fulcrum – Work speedily – Always at a mechanical disadvantage (c) Third-class lever Arrangement of the elements is load-effort-fulcrum. Load Arrangement of the elements is load-effort-fulcrum. Effort L Fulcrum Load L Fulcrum Effort Example: tweezers or forceps In the body: Flexing the forearm by the biceps brachii muscle exemplifies third-class leverage. The effort is exerted on the proximal radius of the forearm; the fulcrum is the elbow joint; and the load is the hand distal end of the forearm.

Embryonic Development of the Muscles • Muscles organized into 4 groups – Musculature of the visceral organs – Pharyngeal arch muscles – Axial muscles – Limb muscles

Embryonic Development of the Muscles • Musculature of the visceral organs – Includes smooth & cardiac muscle – Develops from splanchnic mesoderm • Pharyngeal arch muscles – Includes • Skeletal muscles of the pharynx • Muscles of the head & neck – Develop from the 4 th to 7 th somitomeres

Development of the Muscles First (occipital) myotomes Somitomeres Eye Pharynx Limb bud Myotomes Limb bud (a) 6 -week embryo

Pharyngeal Arch Muscles Pharynx Muscles of facial expression e. g. , orbicularis oculi Chewing muscles e. g. , temporalis, masseter Suprahyoid muscles (most) Pharyngeal constrictors (key swallowing muscles) Trapezius (c) Pharyngeal arch (branchiomeric) muscles: 4 th– 7 th somitomeres

Axial Muscles • Lie anterior & posterior to the body axis • Muscles of the: – Thorax, abdomen, & pelvis • And many muscles of the: – Neck & some of the head • Function to move the trunk & maintain posture

Axial Muscles Extrinsic muscles of the eye Deep muscles of the back e. g. , erector spinae Tongue Muscles of the anterior & lateral trunk e. g. , 1. infrahyoid muscles Tongue (neck) muscles 2. intercostal muscles (thorax) 3. external & internal obliques (abdomen) 4. muscles of the pelvic floor (d) Axial muscles: 1 st– 3 rd somitomeres and myotomes

Limb Muscles • Limb muscles arise from lateral parts of nearby myotomes • Extensors – Muscle mass dorsal to limb bones • Flexors – Muscle mass ventral to limb bones

Limb Muscles Extensors e. g. , triceps brachii, extensor digitorum Extensors Flexors (e) Limb muscles: From myotomes Flexors e. g. , biceps brachii, flexor carpi radialis Extensors e. g. , quadriceps femoris, tibialis anterior Flexors e. g. , hamstrings, gastrocnemius

Muscle Actions & Interactions • A muscle cannot reverse the movement it produces • Another muscle must undo the action • Muscles with opposite actions lie on opposite sides of a joint

Muscle Actions & Interactions • Prime mover (= agonist) – Has major responsibility for a certain movement • Antagonist – Opposes or reverses a movement • Synergist helps the prime mover – By adding extra force – By reducing undesirable movements

Muscle Actions & Interactions (a) A muscle that crosses on the anterior side of a joint produces flexion* Example: Pectoralis major (anterior view) *These generalities do not apply to the knee and ankle because the lower limb is rotated during development. The muscles that cross these joints posteriorly produce flexion, and those that cross anteriorly produce extension. (b) A muscle that crosses on the posterior side of a joint produces extension* Example: Latissimus dorsi (posterior view) *These generalities do not apply to the knee and ankle because the lower limb is rotated during development. The muscles that cross these joints posteriorly produce flexion, and those that cross anteriorly produce extension.

Muscle Actions & Interactions (c) A muscle that crosses on the lateral side of a joint produces abduction Example: Medial deltoid (anterolateral view) (d) A muscle that crosses on the medial side of a joint produces adduction Example: Teres major (posterolateral view)

Muscle Compartments of the Limbs • Dense fibrous connective tissue divides limb muscles into compartments • Muscles in opposing compartments are – Agonist & antagonist pairs • Each compartment is innervated by one single nerve

Muscle Compartments of Arm & Forearm • The upper limb has anterior & posterior compartments – Anterior arm compartment muscles: • Flex the shoulder or arm • Innervation is the musculocutaneous nerve (we’ll learn later) – Anterior forearm compartment muscles: • Flex the wrist & digits • Innervation is the median or ulnar nerve (. . later)

Muscle Compartments of the Arm Extensors Flexors (a) Triceps brachii Lateral head Long head Medial head Posterior compartment of arm (extends elbow); innervation: radial nerve Humerus Brachialis Short head Long head (a) Muscles of the arm Anterior compartment of arm (flexes elbow); innervation: musculocutaneous nerve Biceps brachii

Muscle Compartments of the Thigh • Posterior compartment muscles – Extend the hip & flex the knee – Innervation is the tibial branch of the sciatic nerve (later) • Anterior compartment muscles – Flex the hip & extend the knee – Innervation is the femoral nerve (later) • Medial compartment – Adduct the thigh – Innervation is the obturator nerve (later)

Muscle Compartments of the Thigh (a) Adductors Hamstrings Vastus lateralis Femur Posterior compartment of thigh (flexes leg and extends thigh); innervation: tibial nerve (portion of sciatic nerve) Vastus intermedius Rectus femoris Vastus medialis Posterior compartment muscles Anterior compartment Medial compartment muscles Anterior compartment (extends (adducts thigh); innervation: Medial compartment leg); innervated by femoral nerve obturator nerve muscles of thigh and lateral compartment (a) Muscles of the thigh muscles of leg

Lab Guide for Learning the Muscles

Superficial Muscles of the Body Shoulder Trapezius Deltoid Head Temporalis Masseter Arm Triceps brachii Brachialis Forearm Pronator teres Brachioradialis Flexor carpi radialis Palmaris longus Pelvis/thigh Iliopsoas Pectineus Thigh Rectus femoris Vastus lateralis Vastus medialis Leg Fibularis longus Extensor digitorum longus Tibialis anterior Facial Epicranius, frontal belly Orbicularis oculi Zygomaticus Orbicularis oris Neck Sternohyoid Sternocleidomastoid Platysma Thorax Pectoralis minor Serratus anterior Pectoralis major Intercostals Abdomen Rectus abdominis Internal oblique Transversus abdominis External oblique Thigh Tensor fasciae latae Sartorius Adductor longus Gracilis Leg Gastrocnemius Soleus

Superficial Muscles of the Body Arm Triceps brachii Brachialis Forearm Brachioradialis Extensor carpi radialis longus Flexor carpi ulnaris Extensor digitorum Iliotibial tract Leg Gastrocnemius Soleus Fibularis longus Calcaneal (Achilles) tendon Neck Epicranius, occipital belly Sternocleidomastoid Trapezius Shoulder Deltoid Infraspinatus Teres major Rhomboid major Triangle of auscultation Latissimus dorsi Hip Gluteus medius Gluteus maximus Thigh Adductor magnus Gracilis Hamstrings: Biceps femoris Semitendinosus Semimembranosus

Muscles of the Head – Facial Expression • Muscles of facial expression – Lie in the face & scalp – Thin & variable in shape – Often insert in the skin not on bones – (Innervated by cranial nerve VII the facial nerve)

Muscles of the Face & Head Galea aponeurotica Frontal belly Corrugator supercilii Orbicularis oculi Levator labii superioris Epicranius Occipital belly Temporalis Zygomaticus minor and major Buccinator Risorius Orbicularis oris Mentalis Depressor labii inferioris Depressor anguli oris Platysma Masseter Sternocleidomastoid Trapezius Splenius capitis

Muscles of Mastication & Tongue Movement • 4 main pairs of muscles involved in mastication – Innervated by mandibular division of the trigeminal nerve (cranial nerve V) – Prime movers of jaw closure • Masseter & temporalis – Side-to-side movement • Pterygoid muscles – Compression of cheeks • Buccinator muscles PLAY A&P Flix: Buccinator PLAY A&P Flix: Masseter PLAY A&P Flix: Temporalis

Muscles of Mastication & Tongue Movement Temporalis Lateral pterygoid Orbicularis oris Medial pterygoid Masseter Buccinator Masseter pulled away (a) (b)

Muscles of the Anterior Neck & Throat – Swallowing • The neck is divided into anterior & posterior triangles • Anterior triangle – Divided into suprahyoid & infrahyoid muscles – Participate in swallowing • Pharyngeal constrictors – Swallowing muscles squeeze food into esophagus

Muscles of the Anterior Neck & Throat Tensor veli palatini Levator veli palatini Styloid process Superior pharyngeal constrictor Middle pharyngeal constrictor Hyoid bone Thyrohyoid membrane Inferior pharyngeal constrictor Esophagus Buccinator Mandible Mylohyoid (cut) Geniohyoid Hyoglossus Thyroid cartilage of larynx Trachea

Muscles of the Neck & Vertebral Column • Head movement: – Sternocleidomastoid – Splenius muscles – Neck movement – scalenes 1 st cervical vertebra Sternocleidomastoid Base of occipital bone Mastoid process Middle scalene Anterior scalene Posterior scalene (a) Anterior

Muscles of the Neck & Vertebral Column Mastoid process Splenius capitis Spinous processes of the vertebrae Splenius cervicis (b) Posterior

Muscles of the Neck & Vertebral Column • Trunk extension – Deep muscles of the back • Maintain normal curvatures of the spine • Form a column from sacrum to the skull – Erector spinae group • Largest of the deep back muscles

Muscles of the Neck & Vertebral Column Mastoid process of temporal bone Longissimus capitis Iliocostalis cervicis Longissimus cervicis Iliocostalis thoracis Longissimus thoracis Spinalis thoracis Erector spinae Ligamentum nuchae Semispinalis capitis Semispinalis cervicis Semispinalis thoracis Iliocostalis Longissimus Spinalis Multifidus Iliocostalis lumborum External oblique Quadratus lumborum

PLAY A&P Flix: Iliocostalis PLAY A&P Flix: Longissimus PLAY A&P Flix: Spinalis

Deep Muscles of the Thorax – Breathing • Deep muscles provide movements for breathing – External intercostal muscles • Lift the rib cage during inhalation – Internal intercostal muscles • Aid expiration during heavy breathing

Deep Muscles of the Thorax— Breathing External intercostal Internal intercostal PLAY A&P Flix: External intercostal muscles PLAY A&P Flix: Internal intercostal muscles

Deep Muscles of the Thorax – Breathing • Diaphragm – Most important muscle of respiration! – Flattens as it contracts • Increases the volume of the thoracic cavity • How does this aid in breathing? • Innervated by phrenic nerve (your brain controls)

Deep Muscles of the Thorax— Breathing Xiphoid process of sternum Foramen for inferior vena cava Foramen for esophagus Costal cartilage Central tendon of diaphragm Diaphragm Foramen for aorta Lumbar vertebra 12 th rib Quadratus lumborum Psoas major

Muscles of the Abdominal Wall • Lateral & anterior abdominal wall – Formed from 3 flat muscle sheets • External oblique • Internal oblique • Transversus abdominis – Fourth muscle pair • Rectus abdominis – Inserts at the linea alba

Muscles of the Abdominal Wall Pectoralis major Serratus anterior Linea alba Tendinous intersection Transversus abdominis Rectus abdominis Internal oblique External oblique Inguinal ligament (formed by free inferior border of the external oblique aponeurosis) Aponeurosis of the external oblique (a) PLAY A&P Flix: Internal obliques PLAY A&P Flix: External obliques

Muscles of the Abdominal Wall External oblique Rectus abdominis Internal oblique Transversus abdominis PLAY A&P Flix: Transverse abdominis PLAY A&P Flix: Rectus abdominis

Muscles of the Pelvic Floor • Pelvic floor (pelvic diaphragm) • Sheet of 2 muscles – Both support pelvic organs • Levator ani – Formed from iliococcygeus, puborectalis, & pubococcygeus • Coccygeus

Muscles of the Pelvic Floor Anterior Levator ani Pubococcygeus Symphysis pubis IIiococcygeus Urogenital diaphragm Urethra Vagina Anal canal Obturator internus Coccyx Piriformis Levator ani Posterior Coccygeus Pelvic diaphragm

Muscles of the Perineum Midline raphe Bulbospongiosus Ischiocavernosus Penis Clitoris Superficial transverse perineal muscle Urethral opening Vaginal opening Anus Levator ani Gluteus maximus Male Female

Superficial Muscles of the Anterior Thorax • Movements of the scapula – Pectoralis major – Pectoralis minor – Serratus anterior – Subclavius PLAY A&P Flix: Pectoralis major PLAY A&P Flix: Pectoralis minor PLAY A&P Flix: Serratus anterior

Superficial Muscles of Anterior Thorax Sternocleidomastoid Subclavius Clavicle Deltoid Pectoralis major Sternum Biceps brachii Subscapularis Pectoralis minor Coracobrachialis Serratus anterior Humerus

Superficial Muscles of the Posterior Thorax • Movements of the scapula – Trapezius – Levator scapulae – Rhomboid major – Rhomboid minor PLAY A&P Flix: Trapezius PLAY A&P Flix: Levator scapulae PLAY A&P Flix: Rhomboid major PLAY A&P Flix: Rhomboid minor

Superficial Muscles of the Posterior Thorax Levator scapulae Trapezius Supraspinatus Clavicle Deltoid Rhomboid minor Rhomboid major Spine of scapula Infraspinatus Teres minor Teres major Humerus Latissimus dorsi

Muscles Crossing the Shoulder Joint • Movements of the arm – Deltoid – Pectoralis major Clavicle Deltoid Sternum Pectoralis major Coracobrachialis Triceps brachii Lateral head Long head Medial head Biceps brachii PLAY A&P Flix: Deltoid Brachialis Brachioradialis (a) Anterior view

Muscles Crossing the Shoulder Joint • Movements of the arm PLAY A&P Flix: Latissimus dorsi PLAY A&P Flix: Supraspinatus PLAY A&P Flix: Infraspinatus Supraspinatus Spine of scapula Deltoid (cut) Greater tubercle of humerus Infraspinatus Teres minor Teres major Triceps brachii Lateral head Long head Latissimus dorsi Humerus Olecranon process of ulna Anconeus (b) Posterior view

Muscles Crossing the Shoulder Joint Supraspinatus • Movements of arm PLAY A&P Flix: Teres minor Spine of scapula Deltoid (cut) Greater tubercle of humerus Infraspinatus Teres minor PLAY A&P Flix: Teres major PLAY A&P Flix: Subscapularis Teres major Triceps brachii Lateral head Long head Latissimus dorsi Humerus Olecranon process of ulna Anconeus (b) Posterior view

Questions…? What’s Next? Lab: Muscles Next Lecture: Muscles cont… Wed Lab: Finish Muscles & Review