The Muscular System Part 2: Identification

Objectives Identify the major skeletal muscle of the human body Explain each identified skeletal muscle’s function or role

Muscles of the head & Face Occipitofrontalis Raises the eyebrows Orbicularis oculi Closes the eye lid Zygomaticus minor Raises the upper lip Zygomaticus major Pulls corner of the mouth up & out

Muscles of the head & Face Orbicularis oris Narrows mouth & purses lips Buccinator Pulls back the angle of the mouth & flattens the cheek area Aids whistling and smiling In babies it is used to suckle Masseter Lifts the lower jaw & closes the mouth

Smiling Frowning Requires only 4 muscles Levator labii superioris Zygomaticus minor Zygomaticus major Risorius Requires 8 muscles! Occipitofrontalis Corrugator supercilii Orbicularis oculi Dilator naris Platysma Depressor anguli oris Depressor labii inferioris Mentalis

Muscles of the Head & Face m. occipitofrontalis

Muscles of the neck Splenius capitis Moves the head & twists the neck Levator scapulae Lifts & twists the shoulder Sternocleimastoid Tilts & twists the neck Sternohyoid Depresses the larynx

Muscles of the neck Scalenus anterior, medius, & posterior Aid in breathing & neck flexion The anterior and middle scalene muscles elevate the first rib and rotate the neck to the same side The posterior scalene elevates the second rib and tilts the neck to the opposite side Trapezius Rotates, elevates and retracts the shoulder blade

Muscles of the neck m. sternocleimastoid m. sternohyoid m. scalenus anterior m. sternohyoid

Anterior Muscles of the torso Deltoid Raises arm away from the body to front, side, and rear External intercostals Elevate the ribs Pectoralis major Draws arm toward the body and rotates upper arm inward Biceps brachii Flexes forearm at the elbow and turns the palm upward

Anterior Muscles of the torso Serratus anterior Pulls shoulder blades away from the spine External oblique abdominal Flexes and rotates trunk Rectus abdominis Flexes spine and draws pelvis forward Pyramidalis Tenses the linea alba It is absent in 20% of normal humans

Anterior Muscles of the torso m. deltoid m. external intercostals Linea alba Anterior Muscles of the torso m. external oblique abdominal

Posterior Muscles of the torso Infraspinatus Rotates arm & stabilizes the shoulder Teres major & teres minor Lifts & twists arm, stabilizes the shoulder Triceps brachii Moves arm down towards the body and contracts to straighten the arm

Posterior Muscles of the torso Latissimus dorsi Extends, rotates and lowers arm, pulls shoulder back Largest surface area of any muscle in the body Gluteus maximus Raises thigh away from body at the hip, rotates the thigh, and tilts the pelvis when walking

Posterior muscles of the torso

Anterior Muscles of the arm Pronator teres pronates the forearm, turning the hand posteriorly Brachioradialis Flexes arm at the elbow Flexor carpi radialis Flexes hand at wrist Flexor digitorum superficialis Flexes joints of hand and wrist

Anterior muscles of the arm

Posterior Muscles of the arm Brachialis Flexes the elbow Extensor carpi radialis longus Extends the wrist at the joint & abducts the hand at the wrist Is a set of 5 muscles together Extensor digitorum Extends all finger joints

Posterior muscles of the arm

Anterior Muscles of the hand Abductor pollicis brevis Pulls thumb in toward the palm Flexor pollicis brevis Flexes the thumb at the first metacarpal joint Abductor digiti minimi Abducts the little finger Flexor digiti minimi brevis Flexes the little finger

Anterior muscles of the hand

Anterior Muscles of the LEg Iliopsoas Flexes the thigh at the hip Pectineus Flexes & draws thigh in toward the body Adductor longus Rotates and draws the thigh in toward the body Gracilis Flexes and rotates the leg

Anterior Muscles of the Leg Sartorius Flexes thigh at the hip and leg at knee joint, and turns thigh outward Rectus femoris Flexes the thigh at the hip and with other muscles extends the knee Vastus lateralis & vastus medialis Help to extend the knee Peroneus brevis Flexes the foot downward and stops it from turning inward

Anterior Muscles of the Leg Peroneus longus Flexes the foot downward and turns it outward Tibialis anterior Flexes the foot upward and inward, & supports the arch of the foot when running or walking Extensor hallucis longus Extends the big toe Extensor digitorum longus Extends toes & ankle

Anterior muscles of the leg

Posterior Muscles of the Leg Adductor magnus Rotates, flexes & extends the thigh Biceps femoris, Semitendinosus, & Semimembranosus Extends the thigh at the hip, flexes and rotates the leg All three muscles make up the hamstrings Plantaris Assists in knee flexion

Posterior Muscles of the Leg Gastrocnemius The main calf muscle It contracts to flex the ankle and pull up the heel, as when standing on tip–toe and flexes your knee Tibialis posterior Is the main muscle in turning the foot inward Fibularis longus & fibularis brevis Flex and turn the foot outward Soleus Flexes the foot and it needed for walking and running

Posterior Muscles of the Leg Achilles (calcaneal) tendon It serves to attach the plantaris, gastrocnemius, and soleus muscles to the calcaneus (heel) bone

Posterior muscles of the leg Achilles (calcaneal) tendon