BIOL243 Human Anatomy & Physiology I PDF

BIOL243 – HUMAN ANATOMY & PHYSIOLOGY I Charles Smith, PhD CSCS HUMAN ANATOMY & PHYSIOLOGY Ch. 10 – Skeletal Muscle System IDENTIFYING SKELETAL MUSCLES 3 Functional Groups: 1. Agonists “Prime movers” Produce a specific movement 2. Antagonists Oppose the agon...

BIOL243 – HUMAN ANATOMY & PHYSIOLOGY I Charles Smith, PhD CSCS HUMAN ANATOMY & PHYSIOLOGY Ch. 10 – Skeletal Muscle System IDENTIFYING SKELETAL MUSCLES 3 Functional Groups: 1. Agonists “Prime movers” Produce a specific movement 2. Antagonists Oppose the agonist’s movement(s) Typically located on the side opposite their agonist e.g., the triceps (posterior) are antagonists to the biceps (anterior) 3. Synergists “accessory” muscles Work with the agonists Add extra force to same movement Fixators: immobilize bone or muscle origin rather than enhance agonist’s action(s) Helps for stability These groupings are non-exclusive A muscle may be the agonist for one movement… …the antagonist to another …and/or a synergist to yet another movement HOW TO NAME YOUR MUSCLES Location To what bone or body region is this muscle associated? e.g., temporalis muscle found over the temporal bone Shape Does this muscle have a distinctive shape? e.g., the deltoid muscle shaped like a triangle; the rhomboids like a rhombus Size Maximus = Biggest; Minimus = Smallest Longus = Longer; Brevis = Shorter Fiber or Fascicle Direction Rectus = fibers run straight Transversus = fibers run @ right angles Oblique = fibers run at angles to an imaginary axis Number of Origins e.g., Biceps have two origins; Triceps have three HOW TO NAME YOUR MUSCLES Location of Attachments Based upon their origin and insertion points (origin named 1st) Origin: attachment to the immovable (or less movable) bone Insertion: attachment to the movable bone All muscle actions serve to bring the insertion point closer to the origination e.g., sternocleidomastoid (SCM) muscle originates at the sternum & clavicle then inserts at the mastoid process Muscle Action What does this muscle do? e.g., flexors, extensors, abductors Some of these criteria even get combined e.g., Extensor carpi radialis longus → the long muscle on the radius that extends the wrist Basically, use the name to help reverse engineer CLASSING BY FASCICLE DIRECTIONS The arrangements in the fascicles give us the muscles striations Gives muscles different shapes and functions Can also be used to help decide what the function is At least along what plane the muscle’s action will take place Common Patterns: Circular: concentric rings (i.e., orbicularis orbis) Convergent: broad, converging toward a single tendon (i.e., pec major) Parallel: parallel to the long axis (i.e., sartorius) Pennate: spindle-shaped with parallel fibers (i.e., rectus femoris; deltoids) Fusiform: large muscle belly, tapered ends near tendon (i.e., biceps brachii) LEARNING SKELETAL MUSCLES The human body has >600 muscles Ideally, one would learn each muscle’s: Description: where it is located relative to other muscles Origin & Insertion Points: where it attaches; often crossing a joint Action(s): what movement does its contraction cause Innervation: what nerve supplies it with motor stimulus For now, we will focus on descriptions & actions More than that in a single, introductory A & P course is…not feasible/helpful 1. Use what’s covered in lab to help tie things together Tie location to description Tie location to action(s); attachments to action(s) 2. Reverse engineer from the muscle’s name Can help, but limited; some memorization still required 3. When in doubt, find the muscle on yourself FACIAL EXPRESSION MUSCLES Muscles different because they insert into skin (not bone) Important for non-verbal communication Body Language Bell’s Palsy: hemiparalysis of these muscles Zygomaticus major: raises lateral corners of mouth (i.e., smiling) Orbicularis oris: closes & protrudes lips (i.e., puckering, kissing, whistling) Orbicularis oculi: closes eye (i.e., blinking, squinting); pulls eyebrows inferiorly (i.e., furrowed brow) Mentalis: wrinkles the chin; protrudes lower lip (i.e., pouty lips) Currugator supercili: pulls eyebrows medially & inferiorly; wrinkles eyebrows vertically (i.e., angry eyebrow) Epicranius (Occipitofrontalis): frontal belly raises eyebrows & wrinkles forehead skin horizontally (i.e., surprise) Platysma: tenses skin of the neck MASTICATION & NECK MUSCLES Mastication (Chewing) Masseter & Temporalis: Jaw closure Medial & Lateral pterygoids: deep muscles; grinding movements Anterior Neck Sternocleidomastoid (SCM): forward flex neck; laterally flex neck ipsilaterally (same side) & rotate neck contralaterally (opposite side) Scalenes: laterally flex & rotate neck; elevate first two ribs for inspiration Posterior Neck Trapezius: originate on occipital bone; stabilize, elevate, retract, and rotate scapula Levator scapulae: originate on C1 – C4; elevate and retract scapula SPINAL MUSCLES Erector Spinae group: 3 muscles which collectively act to keep back erect & extend spinal column Will laterally flex spinal column ipsilaterally if only activated unilaterally All three run length of spine, in totality, but can have subsections at each spinal segment (capitis, cervicis, thoracis, lumborum) Iliocostalis: most lateral Subgroups: cervicis, thoracis, lumborum Longissimus: intermediate Subgroups: capitis, cervicis, thoracis Spinalis: most medial Subgroups: thoracis & cervicis Quadratus lumborum (QL): similar actions to erector spinae THORACIC MUSCLES Respiratory Muscles: Diaphragm: inspiration; depresses to expand thoracic cavity Its contraction (depression) and relaxation (elevation) dictate respiratory rate External Intercostals: inspiration; elevates rib cage to expand thoracic cavity Internal Intercostals: expiration; depresses rib cage to compress thoracic cavity Abdominals: Rectus Abdominis: forward flex and rotate lumbar vertebrae; stabilize pelvis during walking; aka your 6-pack (well really….8-pack) External Oblique: forward flex lumbar vertebrae; aid back muscles to laterally flex trunk ipsilaterally & rotate trunk contralaterally Internal Oblique: same as external oblique Transversus Abdominis: deepest abdominal muscle; compress abdominal contents & stabilize spine SHOULDER GIRDLE & UPPER ARM (ANTERIOR) Pectoralis major: adducts & internally (medially) rotates shoulder Deltoid Anterior deltoid: flexes & internally (medially) rotates shoulder Pectoralis major Medial deltoid: abducts shoulder Biceps brachii: flexes elbow & supinates forearm Serratus Anterior Brachialis: flexes elbow Biceps brachii Brachialis Brachioradialis: assists in elbow flexion; Brachioradialis stabilizes elbow Serratus anterior: aka “boxer’s muscle”; protracts scapula SHOULDER GIRDLE & UPPER ARM (POSTERIOR) Supraspinatus Latissimus dorsi: extends, adducts, and internally Spine of scapula (medially) rotates shoulder Greater tubercle of humerus Triceps brachii: extends elbow Infraspinatus Supraspinatus: abducts shoulder Teres minor Teres major Infraspinatus: externally (laterally) rotates shoulder Triceps brachii: Teres minor: same as infraspinatus Lateral head Long head Subscapularis: abducts shoulder Latissimus dorsi Rhomboids: attach to medial border of scapula; stabilize & retract scapula *red text = rotator cuff muscles Synergists & fixator muscles for shoulder; prevent dislocation Commonly injured in activities involving a lot of arm movements FOREARM MUSCLES Forearm Flexors: Pronator teres: pronates forearm; assists with elbow flexion Flexor carpi radialis: flexes & abducts wrist Palmaris longus: flexes wrist; tenses skin & fascia of hand during hand movements Flexor carpi ulnaris: flexes & adducts wrist Forearm Extensors: Extensor carpi radialis longus: extends & abducts wrist Extensor carpi radialis brevis: extends & abducts wrist Extensor digitorum: prime mover in finger extension & abducts (flare) fingers Extensor carpi ulnaris: extends & abducts wrist  THIGH MUSCLES (ANTERIOR/MEDIAL) Iliopsoas Adductor Group Iliacus: flexes hip; also flexes trunk at hip Adductor magnus: flexes, adducts, & internally (medially) rotates hip; posterior fibers Psoas major: same as iliacus; also laterally flexes trunk ipsilaterally assist hip extension Adductor longus: flexes, adducts, & internally Quadriceps Group (medially) rotates hip Rectus femoris: flexes hip & extends knee Adductor brevis: flexes, adducts, & internally Vastus lateralis (VL): extends & stabilizes knee (medially) rotates hip Vastus medialis (VM): extends knee Pectineus: flexes, adducts, & internally Vastus intermedius (VI): extends knee (medially) rotates hip Sartorius: flexes, abducts, and externally Gracilis: flexes, adducts, & internally (laterally) rotates hip (medially) rotates hip Tensor fasciae latae (TFL): flexes, abducts, & internally (medially) rotates hip; Pectineus Adductor longus Gracilis Adductor magnus HIP MUSCLES (POSTERIOR) Glutes Gluteus maximus: extends, abducts, & externally (laterally) rotates hip; Gluteus medius: abducts & internally (medially) rotates hip Gluteus minimus: same as gluteus medius Piriformis: externally (laterally) rotates hip (when hip extended); abducts hip (when hip flexed) Commonly implicated in cases of sciatica THIGH MUSCLES (POSTERIOR) Hamstrings Biceps femoris: extends hip; flexes knee; externally (laterally) rotates knee (when knee flexed) Semitendinosus: extends hip; flexes & internally (medially) rotates knee Semimembranosus: same as semitendinosus Iliotibial (IT) band Thick fascial band on lateral aspect of thigh Stems off gluteus maximus & TFL Aids with pelvic stability Will become hurt when abductors are weak Dancer’s Hip: IT band moves over greater trochanter creating a “snapping” noise & inflammation SHANK MUSCLES (ANTERIOR COMPARTMENT) Tibialis anterior: dorsiflexes & inverts ankle Extensor digitorum longus: dorsiflexes ankle & extends toes Extensor hallucis longus: dorsiflexes ankle & extends big (great) toe Shin Splints: excess tightness or hypertrophy of anterior compartment muscles puts pressure on tibia causing pain While not powerful, muscles key for preventing toe dragging while walking SHANK MUSCLES (LATERAL COMPARTMENT) Peroneals Fibularis longus: plantar flexes & everts ankle May aid in applying pressure to lateral arch keeping foot flat on ground Fibularis brevis: plantar flexes & everts ankle Important for ankle & foot arch stabilization SHANK MUSCLES (POSTERIOR COMPARTMENT) Triceps surae Gastrocnemius: plantar flexes ankle (when knee extended); aids with knee flexion (when ankle dorsiflexed) Attaches to calcaneus via calcaneal (Achilles) tendon Commonly injured with ankle sprains Can rupture in “stop & go” movements involving rapid plantar flexion with knee extension (i.e., pushing off) Soleus: plantar flexes ankle Plantaris: aids in knee flexion & ankle plantar flexion Popliteus: flexes and internally (medially) rotates knee “unlocks” extended knee so that flexion can begin SKELETAL MUSCULAR SYSTEM SUMMARY Muscles are commonly named based upon their: Location Shape Size Fiber/fascicle Direction Pennation Number of origins Locations of Attachments Action(s) or some combination To study muscles: Group them based upon location and/or actions Then use the names Add in clinical pathologies for fun OR to help differentiate between similar muscles Don’t forget to try to find these muscles on yourself Tactile & Kinesthetic learning can be POWERFUL tools SAMPLE QUESTIONS 1. Which muscle of the shoulder girdle are also referred to as “rotator cuff” muscles? 2. Which quadriceps muscle is the only one which acts upon both the knee and hip joints? 3. Which anterior compartment muscle of the shank both dorsiflexes and inverts the ankle? 4. Which posterior upper arm muscle has 3 heads? 5. The oblique muscles of the abdomen rotate the trunk toward which side?  COPYRIGHT © Pearson Edited by Charles Smith, PhD CSCS 2024