1. Muscular System Chapter 6

2. Muscle Types Skeletal muscles – attach to the body’s skeleton Cardiac – heart Smooth – walls of hollow organs such as the stomach, urinary bladder, intestines, and respiratory tract

3. Muscle Types (cont.) NucleiStriationsIntercalated Disks Voluntary or Involuntary Movement CardiacUninucleatedYes Involuntary SkeletalMultinucleatedYesNoVoluntary SmoothUninucleatedNo Involuntary

4. Tendons and Ligaments Tendon – attaches muscle to bone Ligament – attaches bone to bone

5. Tendons and Ligaments (cont.)

7. Muscle Functions Produces movement Generates heat Maintains posture Stabilizes joints

8. Microscopic Anatomy of Skeletal Muscle Myofibrils – long ribbon-like organelles  Have striations A band – dArk color I band – light color Sarcomere – a segment of a myofibril Myofilaments – threadlike proteins consisting of actin and myosin  Actin – thin filaments  Myosin – thick filaments

9. Microscopic Anatomy of Skeletal Muscle

10. Skeletal Muscle Activity Electronic impulses originate in the brain Electricity travels through the nervous system Nerves attach to muscle fibers

11. Skeletal Muscle Activity Electricity causes SR to release Ca 2+ ions which start myosin heads to bind with actin tails  Sarcoplasmic reticulum (SR) – a specialized smooth ER that store calcium (Ca 2+ )  Example: myosin - fish hooks actin - chains The end result is muscle contraction

12. Skeletal Muscle Activity

13. Types of Body Movements Origin – attached to the immovable or less movable bone Insertion – attached to the movable bone  When the muscle contracts, the insertion moves toward the origin.

14. Types of Body Movements Flexion – a movement that decreases the angle of the joint and brings two bones closer together

15. Types of Body Movements Extension – a movement that increases the angle, or distance, between two bones or parts of the body

17. Types of Body Movements Adduction – moving a limb toward the body midline Abduction – moving a limb away (generally on the frontal plane) from the midline

18. Types of Body Movements Rotation – movement of a bone around its longitudinal axis  Ex. – Shoulder and head

19. Types of Body Movements Circumduction – a combination of flexion, extension, abduction, and adduction commonly seen in ball-and-socket joints such as the arm  The limb as a whole outlines a cone

20. Gross Anatomy of Skeletal Muscles Head Muscles

21. Facial Muscles Frontalis – Covers the frontal bone  Raises eyebrows and wrinkles forehead Orbicularis oris Temporalis Orbicularis oculi Masseter Frontalis Zygomaticus Platysma Buccinator

22. Facial Muscles Orbicularis Oculi  Close eyes, squint, blink, and wink Orbicularis oris Temporalis Orbicularis oculi Masseter Frontalis Zygomaticus Platysma Buccinator

23. Facial Muscles Orbicularis oris  Closes the mouth and protrudes the lips Orbicularis oris Temporalis Orbicularis oculi Masseter Frontalis Zygomaticus Platysma Buccinator

24. Facial Muscles Buccinator  Flattens the cheek (as in whistling)  Aids in chewing Orbicularis oris Temporalis Orbicularis oculi Masseter Frontalis Zygomaticus Platysma Buccinator

25. Facial Muscles Zygomaticus  “Smiling” muscle Raises the corners of the mouth upward Orbicularis oris Temporalis Orbicularis oculi Masseter Frontalis Zygomaticus Platysma Buccinator

26. Facial Muscles Masseter  Closes the jaw Orbicularis oris Temporalis Orbicularis oculi Masseter Frontalis Zygomaticus Platysma Buccinator

27. Facial Muscles Temporalis  Helps closes the jaw Orbicularis oris Temporalis Orbicularis oculi Masseter Frontalis Zygomaticus Platysma Buccinator

28. Gross Anatomy of Skeletal Muscles Trunk and Neck Muscles

29. Anterior Muscles Platysma  Pulls the corners of the mouth inferiorly Orbicularis oris Temporalis Orbicularis oculi Masseter Frontalis Zygomaticus Platysma Buccinator

30. Anterior Muscles Sternocleidomastoid  One head of the muscle arises from the sternum and the other arises from the clavicle  When both muscles contract, they flex the neck  When one muscle contracts, the head is rotated toward the opposite side

31. Anterior Muscles Pectoralis Major  Covers the upper part of the chest  Adduct and flex the arm

32. Anterior Muscles Pectoralis Minor  Lies deep to the pectoralis major  Draws down the scapula or raises the ribs

33. Anterior Muscles Intercostal Muscles  Deep muscles found between the ribs  Help raise and depress the rib cage for breathing

34. Anterior Muscles Rectus Abdominis  The most superficial muscles of the abdomen  Flex the vertebral column  Compress the abdominal contents during defecation and childbirth  Involved with forced breathing Aponeurosis Rectus abdominis External oblique Internal oblique Transverse abdominis

35. Anterior Muscles External oblique  Make up the lateral walls of the abdomen  Flex the vertebral column  Rotate the trunk and bend it laterally Aponeurosis Rectus abdominis External oblique Internal oblique Transverse abdominis

36. Anterior Muscles Internal oblique  Deep to the external obliques  Same functions as the external obliques Aponeurosis Rectus abdominis External oblique Internal oblique Transverse abdominis

37. Anterior Muscles Transverse abdominis  The deepest muscle of the abdominal wall  Compresses the abdominal contents Aponeurosis Rectus abdominis External oblique Internal oblique Transverse abdominis

38. Anterior Muscles Aponeurosis  A sheetlike tendinous expansion, mainly serving to connect a muscle with the parts it moves Aponeurosis Rectus abdominis External oblique Internal oblique Transverse abdominis

39. Posterior Muscles Trapezius  Most superficial muscles of the posterior neck and upper trunk  Extend the head  Elevate, depress, and adduct the scapula

40. Posterior Muscles Latissimus Dorsi  The large, flat muscle pair that covers the lower back  Extends and adducts the humerus  Important when executing a power stroke (swimming) or striking a blow

41. Posterior Muscles Deltoid  The main muscles for arm abduction  A favored injection site of medication less than 5ml (must be given intramuscularly)

42. Gross Anatomy of Skeletal Muscles Muscles of the Humerus

43. Biceps brachii  The main muscle for flexion of the forearm  The best way to remember its action is that “it turns the corkscrew and pulls the cork”

44. Triceps brachii  The main muscle for elbow extension  Called the “boxer’s” muscle because it can deliver a straight-arm knockout punch