BIOLOGY 2401 ANATOMY PHYSIOLOGY PART I CHAPTER 10

BIOLOGY 2401 ANATOMY & PHYSIOLOGY PART I CHAPTER 10 THE MUSCULAR SYSTEM 1

Skeletal Muscles Work Together • Since muscles can only contract and shorten, to produce opposing motions it takes at least two different muscles. • Muscle classifications: • Agonist: muscle that causes an action • Antagonist: a muscle working in opposition to agonist • Example: the biceps brachii is the agonist when flexing the elbow to lift weights, but is the antagonist when the triceps brachii is extending the elbow to move a bowling ball back to prepare to bowl • Synergists: muscles that work together to cause a movement 2

Information Revealed By the Names of Skeletal Muscles • The naming of muscles usually follows one of 7 criteria: – Location of the muscle – frontalis, temporalis – Relative size of the muscle – maximus, minimus – Shape of the muscle – deltoid, trapezius, rhomboid – Direction of muscle fibers – rectus, oblique, transversus – Location of attachments – sternocleidomastoid – Number of origins – biceps, triceps, quadriceps – Action of the muscle – adductor, flexor 3

Arrangement of Fascicles • The fascicles of muscles can be arranged in a variety of ways – the most common are: 1. Parallel - fascicles are parallel to the long axis of the muscle. – Some of these are also classified as fusiform muscles. 2. Pennate - the fascicles are short and attach to a central tendon – Can be unipennate, bipennate or multipennate 3. Convergent - muscle has a broad origin but the fascicles converge to one tendon. – May be multipennate. 4. Circular - muscle has the fascicles arranged in concentric circles. 4

Lever Systems • Lever systems help move a load more efficiently or with greater speed. • Quickly show lever types next 5

Types of Lever Systems: First Class 6

Types of Lever Systems: Second Class 7

Types of Lever Systems: Third Class 8

Major Skeletal Muscles, Anterior View Print on full page for use as reference 9

Major Skeletal Muscles, Posterior View Print on full page for use as reference 10

For dissection labs • Wear closed toed shoes • Bring your own gloves 11

Muscles of the Scalp and Face • Epicranius consists of: – frontalis (or frontal belly of epicranius) – occipitalis (or occipital belly of epicranius) – These two muscles pull the scalp forward and backward • Various muscles are involved in opening and closing the eyes and mouth, and smiling – Ex: orbicularis oculi, orbicularis oris, zygomaticus, etc. • Usually insert in skin (rather than bone), and adjacent muscles often fuse • There are multiple muscles involved in mastication (chewing) – Prime movers – temporalis and masseter – Synergists – buccinator and orbicularis oris 12

Muscles of the Face 13

Muscles of Mastication 14

Muscles of the Neck: Head Movements • Sternocleidomastoid muscles flex the head/neck if they are both contracted or rotate the head if only one is contracted • The trapezius muscle works with the deeper splenius muscles to extend and hyperextend the head/neck 15

Muscles of the Deep Back: Trunk Movements Erector spinae is the prime mover of back extension Erector spinae muscles consist of three columns on each side of the vertebrae (iliocostalis, longissimus, and spinalis) Lateral bending of the back is accomplished by unilateral contraction of these muscles 16

Muscles of Respiration: Inspiration • Function of deep thoracic muscles is to promote movement for breathing • External intercostals – more superficial layer that lifts the rib cage and increases thoracic volume to allow inspiration • Diaphragm – most important muscle in inspiration 17

Muscles of Respiration: Expiration • Internal intercostals – deeper layer that aids in forced expiration 18

Muscles of the Abdominal Wall • • The abdominal wall is composed of 4 paired muscles 1. external obliques 2. internal obliques 3. rectus abdominis 4. transversus abdominis Their fascicles run at right and oblique angles to one another, giving the abdominal wall added strength They are involved with lateral flexion & rotation of the trunk They help promote urination, defecation, childbirth, vomiting, coughing, and screaming (and laughing) 19

Muscles of the Abdominal Wall 20

Muscles of the Abdominal Wall 21

Muscles of Pelvic Floor and Perineum • Pelvic diaphragm: Funnel-shaped, supports the pelvic viscera. Pierced by anal canal, urethra &, in female, vagina. • Perineum: diamond-shaped area inferior to pelvic diaphragm. Anterior half of diamond is urogenital triangle; posterior half is anal triangle 22

Shoulder Muscles Found on Thorax • Some of the muscles that control the shoulder (humerus or scapula) are found on the thorax – Anterior Thorax: • pectoralis major, • pectoralis minor, and • serratus anterior – Posterior Thorax: • latissimus dorsi, • trapezius, • levator scapulae, and • rhomboids 23

Shoulder Muscles on Thorax, Anterior View 24

Shoulder Muscles on Thorax, Posterior View 25

Muscles Inserting On and Moving the Humerus – Flexion at shoulder (humerus moves anteriorly) • Pectoralis major • Anterior fibers of deltoid – Abduction at shoulder (humerus moves laterally) • Lateral fibers of deltoid – Extention at shoulder (humerus moves posteriorly) • Latissimus dorsi • Posterior fibers of deltoid – Stability and rotation at the shoulder (4 rotator cuff muscles) • Supraspinatus • Infraspinatus • Teres minor 26 • Subscapularis

Muscles Inserting on Humerus, Ant. View 27

Muscles Inserting on Humerus, Posterior View 28

Rotator Cuff, Anterior View) 29

Muscles Moving the Antebrachium • Elbow flexion – Biceps brachii and – Brachialis • Elbow extension – Triceps brachii 30

Muscles Moving the Antebrachium 31

Muscles Moving the Antebrachium: Transverse Section • This transverse section shows the flexors in the anterior compartment and the extensors in the posterior compartment 32

Movements at the Hip Joint • Flexion of the Hip (femur moves anteriorly) • Anterior compartment muscles – Rectus femoris, tensor fascia latae and iliopsoas • Extension of the hip (femur moves posteriorly) • Posterior compartment muscles – Gluteus maximus and – 3 Hamstring muscles » Biceps femoris, Semitendinosus, Semimebranosus • Adduction of the hip (femur moves toward midline) • Medial compartment muscles – Adductors (5 of them) • Abduction and Rotation of the Hip – Gluteus medius, gluteus minimus, and sartorius 33

Movements at the Knee Joint: Some of the Same Muscles (+hip) • Extension of the knee (tibia and fibula move anteriorly) – The Quadriceps: • • Rectus femoris+hip Vastus lateralis Vastus medialis Vastus intermedialis (deep to rectus femoris) • Flexion of the knee (tibia and fibula move posteriorly): – The Hamstrings: • Biceps femoris+hip • Semitendinosus+hip • Semimembranosus+hip • Because the knee is “backwards” compared to the hip and most other joints, a muscle that flexes the hip would extend the knee. • And a muscle that extends the hip, would flex the knee. 34

Movements at the Hip: Flexors, Adductors and Rotators 35

Movements at the Hip: Extensors 36

Movements at the Knee: Extensors 37

Movements at the Knee: Flexors 38

Muscles Moving the Hip and Knee: Transverse Section 39

Movements at the Ankle – Plantar Flexion (toes point downward) • Posterior compartment muscles – Gastocnemius – Soleus – Dorsiflexion (toes point upward) • Anterior compartment muscles – Tibialis anterior 40

Movement at the Ankle: Plantar Flexors 41

Movement at the Ankle: Dorsiflexors • Muscles of the anterior compartment are the primary toe extensors and ankle dorsiflexors • They include the tibialis anterior 42

Practice Questions 43

A muscle that assists the muscle primarily responsible for a given action is a(n) A. Antagonist B. Synergist C. Primary antagonist D. Levator E. Originator 44

A muscle that is inserted on the mandible is probably involved in A. Frowning B. Kissing C. Wrinkling the forehead D. Chewing E. Blowing 45

Muscles ending in the suffix "-costal" would be associated with the A. neck. B. head. C. groin. D. abdomen. E. ribs. 46

Muscles with fibers that run straight or parallel to the long axis of the body are called A. Obliques B. Rectus C. Lateralis D. Transversus E. Medialis 47

The attachment site of the muscle tendon to the more movable bone is called the A. Proximal end B. Insertion C. Distal end D. Origin E. Belly 48

The names of the muscles can indicate all of the following EXCEPT A. The region of the body where the muscle is located B. Action of the muscle C. Fat content of the muscle D. The direction of the muscle relative to the long axis of the body E. Structural characteristics of the muscle 49

Muscles that act as sphincters to close openings are circular muscles. True False 50

The deltoid muscle is named for its location. True False 51

Specific muscle questions 52

The muscle that extends the forearm while doing push-ups is the A. Biceps B. Pectoralis C. Deltoid D. Brachialis E. Triceps 53

The muscular wall of the abdomen is composed of A. glossal muscles. B. oblique and rectus muscles. C. spinal erector muscles. D. pectoralis muscles. E. muscles of mastication. 54

The major abductor muscle of the upper arm is the A. subscapularis. B. deltoid. C. coracobrachialis. D. teres major. E. supraspinatus. 55

Which of the following muscles is NOT a muscle of the hamstring group? A. Semimembranosus B. Biceps femoris C. Semitendinosus D. Quadriceps femoris 56

The muscle that inserts on the acromion and scapular spine is the trapezius. True False 57

The semimembranosus muscle belongs to the group known as the "hamstrings. " True False 58