Lesson 1&2 Chapter 9&10 – The Muscular System and Axial Musculature

Lesson 1&2 Chapter 9&10 – The Muscular System and Axial Musculature 1 Unit 4 Study Guide Excluded from this study: Microanatomy of skeletal muscle fibers from page 246 – 255 (Because it was covered in physiology) and Levers and Pulleys from page 261 – 262 [For Chapter 9, none for Chapter 10) In Unit 1.2, we learned the 3 categories of muscles: skeletal, cardiac, and smooth. - Skeletal: muscle allows us to move the body by pulling on the bones of the skeleton - Cardiac: muscle pushes blood through the arteries veins of circulatory system - Smooth: muscle pushes fluid and solids along digestive tract and other varies functions When naming structural features of muscles and their components, Greek words sarkos (“flesh”) and mys (“muscle”) are often used. Tendons attach the muscle to bone, skin, or another muscle. Aponeuroses are broad sheets of tendon to join muscles or bones together. Muscles having an origin (the attachment where the muscle starts) and an insertion (the attachment where the muscle ends) - The origin is usually stationary and proximal The insertion often moves and is distal If the muscle extends from a broad aponeurosis (wide layer of tendons) to a narrow tendon: - aponeurosis = origin tendon = insertion If there are several tendons at one end and only one at the other: - multiple = origins single = insertion Action of Skeletal Muscle Movements involve planes of motion, already covered: abduction, adducton, flexion, extension, pronation, supination, eversion, inversion, dorsiflexion, plantar flexion, protraction, retraction... Muscles can be grouped into their primary actions into 3 types: - Prime movers (Agonists): the muscle most responsible for a particular movement Synergists: muscles that help the prime mover in a movement Antagonists: provide opposing movement to the prime mover/agonist (so if agonist causes flexion, antagonist causes extension). During flexion by an agonist, the antagonist doesn’t completely relax, it ensures smooth movement through flexion) Lesson 1&2 Chapter 9&10 – The Muscular System and Axial Musculature Naming of Muscles and location  Muscles can be named according to:  Where they are  Their shape Trapezius = trapezoid Deltoid = triangle  Orientation of muscle fibres [ rectus: l, transverse: __ or oblique: /,\ ]  Unique features  Where they originate and insert First part: origin Second part: insertion  Their primary functions Agonist, synergist, antagonist  The actions that result from their primary function Agonist: e.g. biceps brachii produces flexion at the elbow Synergist: e.g. brachialis assists biceps brachii in flexing the elbow Antagonist: e.g. triceps brachii opposes movement of biceps brachii 2 Lesson 1&2 Chapter 9&10 – The Muscular System and Axial Musculature Lesson 2 Axial Musculature Four Groups of Axial Muscles: I. Muscles of head and neck II. Muscles of vertebral column III. Oblique and rectus muscles (abdominal and respiratory muscles) IV. Muscles of the pelvic floor 3 Lesson 1&2 Chapter 9&10 – The Muscular System and Axial Musculature 4 Muscles of the Head and Neck Common head and neck names that you must know:        Zygomaticus Buccinator Orbicularis oculi Orbicularis oris Masseter Temporalis Sternocleidomastoid        smiling muscle suck in your cheeks winking kissing/whistling chewing synergistic muscle for jaw closure head flexion (nod) Muscles of Expression Facial  [Cranial area] Occipitofrontalis (frontal belly) raises eyebrows and wrinkles in the forehead Epicranial aponeurosis is a collagenous sheet of tendon separating frontal and occipital belly. Occipitofrontalis (occipital belly) tenses and retracts scalp     [Facial area] Orbicularis oculi closes eyes Orbicularis oris constricts opening of mouth Buccinators moves food across teeth via sunction Platysma tenses the skin of the neck     [Extra-ocular area] Medial rectus moves eye inward, toward nose (adduction) Lateral rectus moves eye outward, away from nose (abduction) Superior rectus moves upward (elevation) Inferior rectus moves downward (depression)  Origin: skull Insertion: skin Lesson 1&2 Chapter 9&10 – The Muscular System and Axial Musculature   Superior oblique rotates top eye toward nose (intorsion) Inferior oblique rotates top eye away from nose (extorsion) Remember: rectus = I (vertical arrangement) oblique = /,\ (diagonal arrangement Muscles of Mastication    Temporalis assists in elevating the mandible Masseter elevates mandible and closes jaw (chewing) [most powerful muscle] Pyterygoid can elevate mandible, move jaw side-to-side, a movement called lateral excursion. Muscles of Mastication “-glossus” = tongue “Genio-“ = chin, “Hyp-“ = hyoid bone, “Palato-“ = palate, “Stylo-“ = styloid process    Palatoglossus Styloglossus Hyoglossus 5 Lesson 1&2 Chapter 9&10 – The Muscular System and Axial Musculature  6 Genioglossus All these muscles are used in various combinations to move the tongue.    Conditions you need to know Dysarthria – can’t move the tongue Dysphasia – can’t speak Dysphagia – can’t swallow Muscles of the Anterior Neck Lesson 1&2 Chapter 9&10 – The Muscular System and Axial Musculature Control the position of larynx, depress the mandible, tense floor of the mouth, and provide stable foundation for muscles of tongue & pharynx. Muscles of the Vertebral Column 7 Lesson 1&2 Chapter 9&10 – The Muscular System and Axial Musculature 8 The deepest muscles of the back are the intrinsic (or true) back muscles. They are innervated by the dorsi rami of the spinal nerves. “capitis” inserts on the skull “cervicis” insertion on upper cervical vertebrae “thoracic” insertion on lower cervical and upper thoracic vertebrae Erector spinae are subdivided into spinalis, longissimus, and illiocostalis. Lesson 1&2 Chapter 9&10 – The Muscular System and Axial Musculature 9 These groups are based on proximity to the vertebrae, with the spinalis group being the closest and illiocostalis being the farthest away. Extensor of Lumbar Region Muscles of the Back Lesson 1&2 Chapter 9&10 – The Muscular System and Axial Musculature 10 Muscles of the Thorax and Abdominopelvic Cavity Divided into cervical, thoracic and abdominal regions. Thoracic Region These muscles lie between vertebral columns and the ventral midline (middle of the body). You have muscles that help elevate the ribs; the sternocleidomastoid muscles helps elevate clavicle. The abdominal area has two muscles: Oblique and Rectus muscles. - Oblique muscles compress underlying structures or rotate spinal column. Rectus muscles flex the spinal column, opposing erector spinae muscles. Oblique muscles in the thorax lie between the ribs; external and internal intercostal muscles. External intercostal muscles are superficial to internal intercostal, and both are very important for respiratory movements of the ribs. Internal Intercostal muscles help for exhalation. Think of it as “internal” pushes in, pushing air out of lungs, thus exhalation. External Intercostal muscles help for inhalation: Think of it as “external” going out by expanding the insides, thus inhalation. Abdominal Region These muscles strengthen the wall of the abdomen which include: - External oblique superficial layer External oblique aponeurosis, covering rectus abdominis Internal oblique deep layer Rectus abdominis deep layer under external oblique Transversus abdominis deep layer under internal oblique Lesson 1&2 Chapter 9&10 – The Muscular System and Axial Musculature 11 [Abdominal cross section] Food for thought: After frantically expressing your mind about how you could eat a horse, you actually only managed to eat a small fraction of what a full horse would be. Anyways, you’re full and you find it difficult to breath with a full stomach. Why is that? Well… that’s because the stomach is located underneath the diaphragm and thus the diaphragm cannot move freely because of the ‘super tiny’ horse in your stomach! Muhaha. Now get back to studying. Muscles of the Perineum and the Pelvic Diaphragm These muscles support the organs of the pelvic cavity, flex the joints of the sacrum and coccyx, and control the movement of materials through the urethra and anus. Boundaries: - Anterior – symphysis pubis Posteriorly – coccyx Laterally ischial tuberosity Perineum: The region between the scrotum and the anus in males, and between the posterior vulva junction and the anus in females. It can be divided into two triangles: - An anterior or urogenital triangle A posterior or anal triangle Lesson 1&2 Chapter 9&10 – The Muscular System and Axial Musculature Pelvic floor This consists of the: - Urogenital diaphragm Extends between the pubic bones. Deep muscles constitute the pelvic floor and encircle the urethra. - Pelvic diaphragm Forms the muscular foundation of the anal triangle. Extends anteriorly superior to the urogenital diaphragm as far as the pubic symphysis. 12