Lecture 6 Muscles

1. Lecture 6Muscles

2. Fascicle Arrangement – relative to tendon • Parallel – biceps brachii • gaster • Convergent – pectoralis major • Circular – orbicularis oris • Pennate – several forms – • One + tendon(s) extends into muscle • Unipennate • Bipennate • multipennate

3. Muscle actions: Agonist (prime mover)- Antagonist- Synergist- Fixator- Points of attachment: Origin insertion

4. Lever Systems Lever- a rigid rod that moves around a fixed point (a fulcrum). Bone. Levers are acted on by two forces. Effort (E)- causes movement. Resistance (R)- opposes movement. Leverage- a mechanical advantage; when a less forceful effort can move a more forceful resistance.

5. First-Class Lever Similar to a seesaw. Can produce mechanical advantage (leverage) or not, depends on location of effort & resistance. Example- head resting on vertebral column. Weight of face is the resistance. Joint between skull & atlas is fulcrum. Posterior neck muscles provide effort.

6. Second - Class Lever Similar to a wheelbarrow. Always produces a mechanical advantage. Resistance is always closer to fulcrum than the effort. Example- raising up on your toes. Resistance is body weight. Fulcrum is ball of foot. Effort is contraction of calf muscles which pull heel up off of floor.

7. Third-Class Lever Most common levers in the body. Always produces a mechanical disadvantage. Example- flexor muscles at the elbow. Resistance is weight in hand. Fulcrum is elbow joint. Effort is contraction of biceps brachii.

8. Characteristics Used to Name Muscles Direction- orientation of fascicles relative to the midline. Rectus abdominis. Size- based on relative size of the muscle. Maximus, brevis, major. Shape- based on the relative form of the muscle. Deltoid, trapezius, serratus. Action- principal action of the muscle. Flexor, levator. Number of origins- number of tendons of origin. Biceps brachii. Location- structure near which a muscle is found. Temporalis, frontalis. Origin and Insertion- site where muscle originates and inserts. Sternocleidomastoid.

9. Most muscles produce their action as the effort in a ___________ lever action. • What criteria are associated with the name ‘pectoralis major’? • In what body region would you look for the ‘rectus abdominis’ and how would you expect the muscle to be oriented? • Where would you expect a prime mover in flexion of the next be located?

10. Axial Muscles • Face and Neck • Vertebral column • Oblique and rectus muscles • Pelvic floor: perineum • Appendicular Musculature • Pectoral Girdle + • Pelvic Girdle + • Generally larger muscles are superficial/ smaller are deep

13. Extraocular Muscles

15. Muscles of Mastication Four Pairs: Masseter, Temporalis, pterygoids (medial and lateral) Elevation: Masseter, temporalis, medial ptergoid Lateral movements: Medial and lateral pterygoids Protracts/retracts mandible Temporalis & ptergoids Depresses: lateral pterygoid

18. Tongue 4 extrinsic Arise elsewhere, but insert into tongue Naming: Suffix: ---glossus = tongue Prefixes: Genio = chin Hyo = hyoid bone Palato = palatine Stylo = styloid process

19. Palatoglossus Styloglossus Genioglossus • Hyoglossus

20. Muscles of Anterior Neck and Pharynx Swallowing and movement of bolus (swallowed food) into esophagus Close floor of oral cavity Depress Mandible Flex neck

21. Digastric m. extends from mandible to mastoid process used to open the mouth Mylohyoid m. extends from hyoid to mandible supports floor of mouth & elevates hyoid bone during swallowing Stylohyoid & Geniohyoid elevate the hyoid during swallowing Omohyoid Sternocleidomastoid muscle: flexes head – paired muscle

23. Muscles that Move the Vertebrae Ventral Muscles – Sternocleidomastoid - flexor Dorsal Muscles: extensors + Three layers: Superficial: splenus muscles - extend neck Muscles moving arm and pectoral girdle Intermediate: Erector spinae: extend vertebral column Origin: vertebral column Spinalis muscles: medial – along spine Longissimus – intermediate Iliocostalis – lateral Deep: transversospinalis group semispinalis, multifidis, rotatores & interspinales and intertransversarii run from transverse process to dorsal spine of vertebrae above & help rotate vertebrae

24. Splenius Sternocleidomastoid Semispinalis capitis

25. Spinalis Longissimus iliocostalis

26. Oblique and Rectus Muscle Anterior (ventral) abdomen and thoracic wall Flexion and rotation of spine Enclose and protect internal cavities Alter thoracic volume during breathing Groups: Thoracic Scalenes External/internal intercostals Abdominal – External and internal oblique muscles Transversusabdominis Rectus abdominis Linea alba Tendinous inscriptions

28. 4 pairs of sheetlike muscles rectus abdominis = vertically oriented external & internal obliques and transverses abdominis wrap around body to form anterior body wall form rectus sheath and linea alba Inguinal ligament from anterior superior iliac spine to upper surface of body of pubis Inguinal canal = passageway from pelvis through body wall musculature opening seen as superficial inguinal ring Inguinal hernia = rupture or separation of abdominal wall allowing protrusion of part of the small intestine (more common in males)

29. Diaphragm Separates Thoracic from Abdominopelvic cavity Dome-like sheet of muscle origin lower 5 ribs, costal cartilages and lumbar vertebrae Crura extend to lumbar vertebrae Insertion on central tendon Continuous with pericardium and pleural membrane 3 openings: Aortic hiatus Esophageal hiatus Caval opening (passage of v.c.)

31. Pelvic Floor • = Perineum • UG triangle • Anal triangle

32. Muscles of Perineum • Muscles of UG triangle: • Superficial muscles: • Bulbospongiosus: origin/insertion of differ male/female (see table 10.9) • Ishiocavernosus • Superficial transverse perenial • Deep muscles: • Deep transverse perineal • External urethral sphincter (differs slightly in male/female) • Muscles of anal triangle (pelvic diaphagm) • Coccygeus • Iliogoccygeus • Pubococcygeus • External anal sphincter

36. Appendicular Muscles

37. Movements of the Scapula – Pectoral Girdle • Elevation • Levator scapulae • Depression • Subclavius • Upward rotation • Serratus anterior • Downward rotation • Pectoralis minor, • Protraction • Pectoralis minor, subclavius • Retraction • Rhomboid major and minor • Trapezius – parts involved in all motions except protraction

40. Movements of Arm (Humerus) Abduction: Deltoid – other movements as well Adduction: pect. major + coracobrachialis Medial rotation: subscapularis, teres major + Lateral rotation: infraspinatus, teres minor Flexion: pectoralis major Extension: latissimus dorsi

43. Forearm Flexion: Biceps brachii Brachialis Brachioradialis Extension: Triceps brachii anconeus • Pronation: • Pronator teres • Pronator quadratus • Supination • supinator

44. Movements of Wrist and Hand Flexors in anterior compartment Extensors in posterior compartment ‘carpi’ refers to muscles moving hand – what kinds of movement? Muscles moving fingers are deep to those moving wrist

45. Movements of the Thigh: • Extension: Gluteus maximus and Hamstring muscles • Flexion: tensor fasciae latae, members of adductor group, quadriceps group, iliopsoas and sartorius • Adduction: members of adductor group (5) • Abduction: glutus medius and minimus, piriformes

48. Adduction of the Thigh: • Pectineus • Gracilis • Adductor brevis • Adductor longus • Adductor magnus • All involved in flexion + other actions

49. More Thigh Movements: • Medial Rotation: adductor group, gluteus medius & minimus, tensor facae latae, semimembraneous and semitendinosus • Lateral rotation: lateral rotator group (6) & gluteus maximus, obturators and piriformis

50. Movements at the Knee: • Flexion • Hamstring muscles • Gastrocnemius • Sartorius • Popliteus • Plantaris • Extension at Knee • Quadriceps muscles