ANATOMY_LC5_MUSCLES OF HEAD AND NECK

COURSE OUTLINE I. INTRODUCTION TO THE MUSCULAR SYSTEM II. FUNCTIONS OF THE MUSCLE III. TYPES OF MUSCLE TISSUE A. Skeletal Muscle B. Cardiac Muscle C. Smooth Muscle IV. ORGANIZATION OF MUSCLE TISSUE A. Connective Tissue Coverings B. Connective...

COURSE OUTLINE I. INTRODUCTION TO THE MUSCULAR SYSTEM II. FUNCTIONS OF THE MUSCLE III. TYPES OF MUSCLE TISSUE A. Skeletal Muscle B. Cardiac Muscle C. Smooth Muscle IV. ORGANIZATION OF MUSCLE TISSUE A. Connective Tissue Coverings B. Connective Tissues C. Nerve Supply D. Attachments and Actions of Skeletal Muscles E. Classification According to Fascicle Arrangements Figure 2: Hierarchy of a Typical Muscle Structure V. NAMING OF SKELETAL MUSCLES VI. DIVISIONS OF THE MUSCLE FUNCTIONS OF MUSCLE: MOVEMENT A. Axial Division/Muscles Skeletal Muscles: B. Appendicular Division/Muscles ○ Attached to bones by tendons. VII. AXIAL DIVISION: HEAD AND NECK ○ Cross joints so when they contract, the bones they attached will move. Smooth Muscles: I. INTRODUCTION TO THE MUSCULAR SYSTEM ○ Found on organ walls. Bones and joints do not produce movements; ○ Contractions produce movement of the organ muscles do (through contraction and relaxation) contents (such as the bolus in the esophagus and The human body has more than 600 individual the chyme in the stomach). muscles. Cardiac Muscle: Half body weight, more than any other organ system. ○ Produces atrial and ventricular contractions. Performance varies by fiber organization and skeletal ○ This pumps blood from the heart into the blood attachments. vessels. Figure 3. Types of Muscles in the Body FUNCTIONS OF MUSCLE: STABILITY Hold bones tightly together. ○ Stabilizes joints Small muscles hold the vertebral bones, or vertebrae in general. Figure 1. The Human Muscular System and its Composition ○ Stabilizes the spinal column. II. FUNCTIONS OF THE MUSCLE The muscles have the ability to contract, permitting the muscles to perform various functions such as: Movement Stability Control of Body Openings and Passages Protection Heat Production Figure 4. Stability of the Body BATCH 2028 1A 1 ANATOMY LC 5: INTRODUCTION TO THE MUSCULAR SYSTEM DR. DE GRANO 09/09/2024 FUNCTIONS OF MUSCLE: CONTROL OF BODY III. TYPES OF MUSCLE TISSUE OPENINGS AND PASSAGES MUSCLE CELLS Myocytes called muscle fibers SPHINCTERS Sarcolemma - the cell membrane of the myocyte Valve-like structure formed by muscles. Sarcoplasm - the cytoplasm of the myocyte Control the movement of substances in and out of Myofibrils - long structures in the sarcoplasm passages (e.g., cardioesophageal: sphincter ○ arrangement of filaments in myofibrils produces between the esophagus and stomach). striations Figure 8. Parts of a Muscle Fiber Figure 5: Internal and External Urethral Sphincter FUNCTIONS OF MUSCLE: PROTECTION Muscles serve as padding for internal organs. Act as a shock absorber and reduce friction at joints. Figure 9. The Three Muscle Groups in the Body Figure 6. Muscles as Protection of the Underlying Organs and Bones A. SKELETAL MUSCLE FUNCTIONS OF MUSCLE: HEAT PRODUCTION The major components of the muscular system: Connective tissue Heat is released with muscle contraction. Skeletal muscle tissue ○ Helps the body maintain the internal balance by Blood vessels maintaining a normal temperature. Nerves ○ Moving the body or performing body exercises can make the body warmer when the surrounding temperature is cold. The body also compensates for the cold temperature through shivering (shaking, either mild or uncontrollable, of the muscles due to cold, fear, or excitement), which is controlled by the central nervous system circuit found in the hypothalamus. Figure 10: Composition of Skeletal Muscle The highly structured and adaptable skeletal muscle tissue is essential for maintaining posture, producing heat, and enabling voluntary motions. Its unique appearance, particular cellular makeup, and capacity to react to nerve signals make it indispensable for Figure 7. Bodily Exercises to Compensate for Cold Temperature various physiological processes. BATCH 2028 1A 2 ANATOMY LC 5: INTRODUCTION TO THE MUSCULAR SYSTEM DR. DE GRANO 09/09/2024 Contractions, supplied by autonomic nerve fibers that terminate in the nodes of the conducting system and in the myocardium. Figure 11. The Skeletal Muscle System STRUCTURE OF SKELETAL MUSCLE TISSUE BELLY RAPHE Figure 13. Nodes of the Heart Responsible for Rhythmic Contraction. Fleshy part of the Interdigitation of the tendinous skeletal muscle ends of flat muscles C. SMOOTH MUSCLE Multiunit Smooth Muscle ○ Found in the iris of the eye & walls of blood vessels ○ Responds to neurotransmitters and hormones. Visceral (single unit) Smooth Muscle ○ Found in walls of hollow organs ○ Responds to neurotransmitters ○ Stimulate each other to contract so that muscle fibers contract and relax together in a rhythmic motion—peristalsis B. CARDIAC MUSCLE Figure 14. Multiunit and Visceral (single) Unit of Smooth Muscle IV. ORGANIZATION OF MUSCLE TISSUE Muscles are covered by fascia For large muscle groups many are encased in both a superficial and a deep fascia. Example: Muscles of the upper limbs and lower limbs Figure 12. Parts of Cardiac Muscle Tissue Intercalated Discs ○ Connect groups of cardiac muscles. ○ Allow the fibers in the groups to contract and relax together. allows the heart to work as a pump. Self-exciting: does not need nerve stimulation to contract. ○ nerves speed up or slow down contraction. Cardiac muscles have the property of producing Figure 15. Fascia spontaneous and rhythmic. BATCH 2028 1A 3 ANATOMY LC 5: INTRODUCTION TO THE MUSCULAR SYSTEM DR. DE GRANO 09/09/2024 CONNECTIVE TISSUE COVERINGS CONNECTIVE TISSUE 1. FASCIA 1. Epimysium Surrounds an individual skeletal muscle, separating Closely surrounds the skeletal muscles, binds it from other muscles. fascicles together Fascia may extend beyond the ends of the muscle Surrounds individual muscle to become a tendon (tough cord-like structure). Composed of irregular, dense connective tissue. Fascia may connect muscle to muscle and is called Found just below the fascia of the muscle. an aponeurosis (tough sheet-like structure) Separates muscles and other organs in the area. Arranged into bundles called fascicles. Allows muscle to contract and move powerfully while maintaining its structural integrity 2. Perimysium Connective tissue that divides the muscle into sections called fascicles. Surrounds fascicles. Allows activation of a specific subset of muscle fibers within a fascicle 3. Endomysium Made up of collagen and reticular fibers. It surrounds a muscle fiber and plays a role in transferring force produced by the muscle fibers to the tendons. ○ Muscle Fiber - composed of myofibrils that is further composed of thick and thin filaments. Figure 16. Tendons 2. FASCICLES Arranged bundles of skeletal muscle fibers (cells) Bound by connective tissues: Epimysium, Perimysium and Endomysium Figure 18. Organization of a Fasciculus NERVE TISSUE Nerve going to the muscle is a mixed nerve MIXED NERVE COMPOSITION MOTOR Supplied by: (60%) Alpha Fibers: from large cells in the Anterior Gray Horn Gamma Fibers: smaller cells in the spinal cord SENSORY Provided by myelinated fibers which arise from (40%) specialized sensory endings lying within the muscle or tendon. Muscle Spindles: stretch receptors within the body of a muscle which primarily detects changes in the length of a muscle. ○ Relay length information to the CNS via afferent nerve fibers. ○ This information can be processed by the brain as proprioception (the awareness of body position). This plays a role in flexibility. ○ Main function: produce muscle contraction Tendon Spindles (Golgi Tendon Organ): works with muscle spindles reflexively to Figure 17. The layers of the deep fascia regulate muscle stiffness. BATCH 2028 1A 4 ANATOMY LC 5: INTRODUCTION TO THE MUSCULAR SYSTEM DR. DE GRANO 09/09/2024 ○ When Golgi Tendon Organ (GTO) is Synergist stimulated, it causes a muscle to relax by ○ complement the action of the agonist by directly interrupting its contraction. providing the same but weaker movement or ○ Autogenic Inhibition: process when a indirect by stabilizing joints especially when more muscle is inhibited by a GTO. than 1 joint is involved ○ Main function: opposite of the muscle ○ multiple synergists can assist any agonist spindles Fixator: stabilizes the origin of the agonist by ○ Make sure that a muscle does not over isometrics contraction to permit efficient action contract or over work itself because it may Antagonist: produces the opposite movement of the lead to injury. agonist ○ In order for a specific movement to occur, either SYMPATHETIC FIBERS: unmyelinated fibers that the agonist (prime mover) or the antagonist must pass to the smooth muscle in the walls of the blood be relaxed via nervous reflex inhibition. vessels supplying the muscles. ○ Regulate blood flow ○ For instance, to contract an agonist, its specific to the muscles. antagonist should be relaxed in equal measure. The nerve enters the muscle at about the midpoint on its deep surface, often near the margin (motor point) Figure 21. Muscle Agonists and Antagonists in the Upper Arm Figure 19. Innervation of Skeletal Muscle: Sympathetic Fibers Figure 22. Fixators, Colored Blue of the Back Muscles to the Spinal Cord The same muscle can assume any of the above roles depending on the type of movement Figure 20. Origin and Insertion of Biceps Brachii with accompanying synergist muscles There are movements where gravity is “the agonist”. In this situation, there is a paradox where Movement is usually produced by a group of muscles the agonist muscles are inactive and relaxed whereas divided into the following roles: the antigravity (antagonist) muscles are active and expending energy Agonist (Prime mover) Example is shoulder adduction while standing erect. ○ responsible for most of the movement by To perform this movement, the pectoralis major & concentric contraction latissimus dorsi (actual adductors) are inactive since ○ uses most of the energy to do most of the work gravity is the prime mover and it is the deltoid (an ○ most movements involve 1 agonist but some abductor) that is active at work. have 2 agonists in equal measure BATCH 2028 1A 5  ANATOMY LC 5: INTRODUCTION TO THE MUSCULAR SYSTEM DR. DE GRANO 09/09/2024 Review of the body movements CLASSIFICATION ACCORDING TO FASCICLE Flexion bending a body part ARRANGEMENT Extension straightening a body part Parallel Muscles Have fascicles arranged in the same Hyperextension extending a body part past the (Majority) direction as the long axis of the normal anatomical position muscle During contraction, it shortens and Abduction moving a body part away from the gets larger in diameter anatomical position Examples: external obliques, fusiform Adduction moving a body part toward the muscles like the biceps brachii can anatomical position also be considered as parallel Plantar flexion pointing the toes down muscles Dorsiflexion pointing the toes up Convergent Muscle fascicles extending over a Circumduction moving a body part in a circle Muscles broad area come together, or Pronation turning the palm of the hand down converge, on a common attachment Supination turning the palm of the hand up site Inversion turning the sole of the foot medially Adaptable to different activities Eversion turning the sole of the foot laterally because the stimulation of different Retraction moving a body part posteriorly portions of the muscle can change Protraction moving a body part anteriorly the direction it pulls Elevation lifting a body part Example: pectoralis major (e.g. elevating the shoulders as in a Circular Muscles Fascicles are concentrically arranged shrugging expression) (sphincters) around an opening Depression lowering a body part Muscle contraction decreases the (e.g. lowering the shoulders) diameter of the opening and vice versa Surround body openings and hollow organs and acts as valves (e.g. digestive and urinary tracts) Examples: orbicularis oculi, orbicularis oris Pennate Muscles Fascicles form a common angle with (penna= "feathers") the tendon Contracting pennate muscles do not move their tendons as far as parallel muscles do More fibers/myofibrils than same-sized parallel muscle; produces less movement but more tension TYPES OF PENNATE MUSCLES ○ Unipennate: Fascicles are located on one side of the tendon (e.g. extensor digitorum) ○ Bipennate: has fascicles on both sides of the tendon as in the arrangement of a single feather (e.g. rectus femoris) ○ Multipennate: like a series of bipennate muscles lying alongside one another or may have the tendon lying Figure 23. Common Body movements within its center and the muscle fibers passing to it from all sides, converging as they go (e.g. deltoid) Figure 24.. Elevation and Depression Apply your knowledge: The doctor has asked you to abduct the patient’s leg so he can see the patient’s wound. In order to position the patient correctly, what will you have to do? Answer: Move the patient’s leg away from its position in the anatomical position Figure 25. Muscles According to Fascicle Shape BATCH 2028 1A 6 ANATOMY LC 5: INTRODUCTION TO THE MUSCULAR SYSTEM DR. DE GRANO 09/09/2024 V. NAMING OF SKELETAL MUSCLES E. LOCATION OF THE MUSCLE’S ORIGIN AND INSERTION Thyrohyoid muscle - originates on the thyroid cartilage and on the sternum and inserts on the part of the hyoid bone A lot of the terms are either Latin or Greek because Greeks and Romans conducted the first studies on the human anatomy in western culture, so the early anatomy pioneers used Greek and Latin terms in naming the skeletal muscles. Example: sterno (on the sternum) F. SHAPE OF THE MUSCLE Examples: Figure 26. Skeletal Muscles ○ deltoid (triangular) ○ trapezius (trapezoid in shape) A. DIRECTION OF MUSCLE FIBERS Rectus abdominis and femoris are straight G. ACTION OF THE MUSCLE muscles You have your flexor digitorum superficialis, The obliques (at an angle) and the transverse you have your extensor carpi ulnaris. (horizontal) muscles of the abdomen. It’s a good way of finding out the action of that Example: rectus (straight) muscle, because it is in the name of the muscle itself. B. RELATIVE SIZE OF THE MUSCLES Example: flexor and extensor (flexes or Names are often used to indicate length, which is extends a bone) related to muscle size. For example, brevis (short), longus (long). Pectoral muscles including major or minor. Gluteal muscles: Gluteus maximus (being the largest) and Gluteus minimus (being the smallest) Example: maximus (largest) C. LOCATION OF THE MUSCLE Many muscles are named after the bones Examples: ○ temporalis, on the temporal bone ○ The frontalis muscle is located on top of the frontal bone of the skull. ○ muscles of the arm that include the term brachii (of the arm) D. NUMBER OF ORIGINS Usually, the start of the muscles name is the origin Figure 28. Anterior and Posterior View of Muscles that Control the and then followed by the insertion Wrist and Hand Biceps, it has 2 heads (bi) Can also be based on: VI. DIVISIONS OF THE MUSCLE ○ Origin: attachment to bone that does NOT There are two divisions of the skeletal muscular move system. ○ Insertion: attachment to bone that MOVES Example: triceps (three heads: lateral head, AXIAL DIVISION/ MUSCLES longus, medius) Support and position the axial skeleton (like the vertebral, back, neck and pelvis). Arise on the axial skeleton Bigger division comprising 60% of the skeletal muscles in the body. Position the head and vertebral column. Move the rib cage (which helps in breathing), which assists the movements that make breathing possible. Form the pelvic floor. APPENDICULAR DIVISION/ MUSCLES Support, move, and brace the limbs. Figure 27. Stabilize or move structures of the appendicular Triceps brachii skeleton. 40% of skeletal muscles. Move and support the pectoral and pelvic girdles and the upper and lower limbs BATCH 2028 1A 7 ANATOMY LC 5: INTRODUCTION TO THE MUSCULAR SYSTEM DR. DE GRANO 09/09/2024 Figure 29. Muscles in the Anterior Region Figure 30. Muscles in the Posterior Region VII. AXIAL DIVISION: HEAD AND NECK A. SCALP NOTE: When the occipitofrontalis muscle contracts the 1st 3 Has only one muscle and that is the occipitofrontalis layers of the scalp actually moved forward or which has an occipital and a frontal belly backward and the loose areolar tissue of the 4th layer of the scalp allows the aponeurosis to move on the pericranium. The frontal belly of the occipitofrontalis can help raise the eyebrows in expressions of surprise or horror. The tension of the epicranial aponeurosis is produced by the cone of the occipitofrontalis muscle and it is important in all deep wounds of the scalp. Example: You have a bite on the forehead or any part on the scalp, it can resemble an incised wound. If you reach aponeurosis, if it has been divided, that wound will surely keep open and that is because of the opposing pull of the frontal and occipital bellies in the opposite direction. For you to be able to have a satisfactory healing you will have to close the aponeurosis layer as well. B. MUSCLES OF FACIAL EXPRESSION Figure 31. Layers of the Scalp Epicranial aponeurosis is clinically important. Because of the strength of this aponeurosis, superficial scalp wounds do not gape, and the margins of the wound are held together. Furthermore, deep sutures are not necessary when suturing superficial wounds because the epicranial aponeurosis does not allow wide separation of the skin. Deep scalp wounds gape widely when the epicranial aponeurosis is lacerated in the coronal plane because of the pull of the frontal and occipital bellies of the occipitofrontalis muscle in opposite directions (anteriorly and posteriorly) BATCH 2028 1A 8  ANATOMY LC 5: INTRODUCTION TO THE MUSCULAR SYSTEM DR. DE GRANO 09/09/2024 Overactive Corrugator supercilii and Procerus – these muscles are the ones that are hit with Botox to make them relax/have less lines on the face Zygomaticus major and minor will work to lift one corner of the lip Figure 32. Muscles of Facial Expression (2nd figure shows the cadaver image of the same muscles as the 1st figure) Figure 34. Both images show Bell’s palsy BELL'S PALSY Caused by an injury to the facial nerve or its branches producing paralysis on some or all the facial muscles on the affected side. The affected side actually sags and facial expression is distorted making it appear passive or sad. Loss of tonus of the Orbicularis oculi causes inferior eyelid to fall away from the surface of the eyeball causing lacrimal fluid to not spread enough leading to inadequate lubrication or hydration of the surface of the cornea results to ulceration or scarring which eventually leads to vision impairment. Paralyzed or weakened Buccinator and orbicularis oris cause food to accumulate in the oral vestibule, and need to remove it with a finger manually or if the sphincters are affected because of the unopposed pull from the contralateral side, you will have dripping of that corner and will result in dribbling of saliva as well as weakening of the lip muscle that can affect or impair the ability to produce sounds affecting some Figure 33. Image shows muscles that is active in producing labia sounds or your overall speech. Constant wiping these facial expressions of fluid results in localized skin irritation. Risorius helps lift the corners of your mouth into a smile. Risorius + Depressor labii inferioris it gives you the toothy smile OCCIPITOFRONTALIS Muscle Origin Insertion Main Action(s) Front belly Epicranial aponeurosis Skin and subcutaneous Elevates eyebrows and wrinkles skin of forehead; tissue of eyebrows and protracts scalp; increasing effectiveness of frontal forehead belly Orbicularis oculi Medial orbital margin; medial Skin around margin of orbit; Closes eyelids: palpebral part does so gently; orbital (orbital sphincter) palpebral ligament; lacrimal superior and inferior tarsal part tightly (winking) bone plates Corrugator Medial end of superciliary arch Skin superior to middle of Draws eyebrow medially and inferiorly, creating supercilii supra-orbital margin and vertical wrinkles above nose (demonstrating concern superciliary arch or worry) Procercus plus Fascia aponeurosis covering Skin of inferior forehead, Depresses medial end of eyebrow; wrinkles skin over transverse part of nasal bone and lateral nasal between eyebrows dorsum of nose (conveying disdain or dislike) nasalis cartilage Alar part of nasalis Frontal process of maxilla Major alar cartilage Depresses ala laterally, dilating anterior nasal aperture plus levator labii (inferomedial margin of orbit) (i.e. “flaring nostrils”, as during anger or exertion) superioris alaeque nasii Orbicularis oris Medial maxilla and mandible; Mucous membrane of lips Tonus closes oral fissure; phasic contraction (oral sphincter) deep surface of peri-oral skin; compresses and protrudes lips (kissing) or resists angle of mouth (modiolus) distension (when blowing) Levator labii Infra-orbital marginal (maxilla) Part of dilators of mouth; retract (elevate) and/or superioris evert upper lip; deepen nasolabial sulcus (showing Skin of upper lip Zygomaticus Anterior aspect, zygomatic sadness) minor bone BATCH 2028 1A 9 ANATOMY LC 5: INTRODUCTION TO THE MUSCULAR SYSTEM DR. DE GRANO 09/09/2024 Buccinator mandible, alveolar process of Angle of mouth (modiolus); Presses cheek against molar teeth; works with tongue (cheek muscle) maxilla and alveolar part of orbicularis oris to keep food between occlusal surfaces and out of mandible, pterygomandibular oral vestibule; resists distension (when blowing) raphe Zygomaticus major Lateral aspect of zygomatic Part of dilators of mouth; elevate labial commissure– bone bilaterally to smile (happiness); unilaterally to sneer (disdain) Angle of mouth Levator anguli oris Infra-orbital maxilla (canine Part of dilators of mouth; widens oral fissure, as when (modiolus) fossa) grinning or grimacing Risorius Parotid fascia and buccal skin Part of dilators of mouth; depresses labial commissure (highly variable) bilateral to frown (sadness) Depressor anguli Antero-lateral bases of Skin of lower lip Part of dilators of mouth; retracts (depresses) and/or oris mandible everts lower lip (pouting, sadness) Mentalis Body of mandible (anterior to Skin of chin Elevates and protrudes lower lip; elevates skin of chin roots of inferior incisors) (mentolabial sulcus) (showing doubt Platysma Subcutaneous fissure of Base of mandible; skin of Depresses mandible (against resistance); tenses skin infraclavicular and cheek and lower lip; angle of of inferior face and neck (conveying tension and supraclavicular regions mouth (modiolus); orbicularis stress) oris Table 1. Origin, Insertion, Action of Facial muscles Muscle of the Neck ○ Gross motor movements that move the head in every direction, as well as pull the skull towards the shoulders, spine, and scapula. Anterior triangle of neck ○ Sternocleidomastoid ○ One or both contract Posterior Neck Muscles ○ Semispinalis capitis, Splenius capitis, Trapezius Figure 35. Muscles of Mastication Muscle of Mastication: “Mom Makes Tasty Lasagna” M (Mom): Masseter M (Makes): Medial Pterygoid T (Tasty): Temporalis L (Lasagna): Lateral Pterygoid Figure 40. Muscles of the neck Hyoid Muscles ○ Primarily in the anterior triangle of the neck ○ Can be Suprahyoid or Infrahyoid depending on Figure 36. Muscles of Mastication: their position relative to the hyoid bone. a) Superficial lateral view; b) Deep lateral view ○ They move the mandible and the hyoid. Figure 41. Hyoid muscles Figure 37. Muscles of Mastication: a) Lateral view; b) Lateral view, pterygoid muscles exposed; c) Insertions, medial view of left mandibular ramus BATCH 2028 1A 10 ANATOMY LC 5: INTRODUCTION TO THE MUSCULAR SYSTEM DR. DE GRANO 09/09/2024 Figure 44. Prevertebral and lateral vertebral muscles supplied by cervical plexus (These are muscles found on the deeper side of the neck are.) Figure 42. Anterior triangle of neck (suprahyoid and infrahyoid) Reference(s): Wineski, L. E. (2019). Snell’s Clinical Anatomy By Regions (10th ed.). Philadelphia (PA): Wolters Kluwer. Dra. Ana Patricia Villanueva-de Grano lecture and PowerPoint presentation (9/09/2024) Figure 43. Prevertebral and lateral muscles BATCH 2028 1A 11