Lecture Human anatomy and physiology - Chapter 10: The muscular system (part a)

The muscular system (part a), the following will be discussed in this chapter: Skeletal muscles: functional groups, naming skeletal muscles, muscle mechanics: arrangement of fascicles, muscle mechanics: lever systems, classes of lever systems,...

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PowerPoint ® Lecture Slides

prepared by Janice Meeking, Mount Royal College

C H A P T E R

10

The Muscular System:

Part A

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Skeletal Muscles: Functional Groups

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Skeletal Muscles: Functional Groups

• Reduce undesirable or unnecessary

movement

• Synergists that immobilize a bone or

muscle’s origin

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Naming Skeletal Muscles

with the muscle

triangle)

minimus (smallest), longus (long)

(fibers run straight), transversus, and oblique (fibers run at angles to an imaginary defined axis)

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Naming Skeletal Muscles

and triceps (3 origins)

point of origin or insertion

flex or extend, respectively

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Muscle Mechanics: Arrangement of Fascicles

• Fascicles arranged in concentric rings (e.g.,

orbicularis oris)

• Fascicles converge toward a single tendon

insertion (e.g., pectoralis major)

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• Fascicles parallel to the long axis of a straplike muscle (e.g., sartorius)

• Spindle-shaped muscles with parallel fibers

(e.g., biceps brachii)

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• Short fascicles attach obliquely to a central

tendon running the length of the muscle (e.g., rectus femoris)

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(a) (b)

(e)

(d)

(g) (f)

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Muscle Mechanics: Lever Systems

• Lever—rigid bar (bone) that moves on a fixed point or fulcrum (joint)

• Effort—force (supplied by muscle contraction) applied to a lever to move a resistance (load)

• Load—resistance (bone + tissues + any added weight) moved by the effort

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Fulcrum Load

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25 cm

50 cm

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Classes of Lever Systems

• First class

• Fulcrum between load and effort

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(a) First-class lever Arrangement of the elements is

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(a) First-class lever Arrangement of the elements is

load-fulcrum-effort

In the body: A first-class lever system

raises your head off your chest The posterior neck muscles provide the effort, the atlanto-occipital joint is the fulcrum, and the weight to be lifted is the facial skeleton.

Load

Fulcrum

Effort

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• Load between fulcrum and effort

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(b) Second-class lever Arrangement of the elements is

fulcrum-load-effort

Example: wheelbarrow

Load Load

Effort

Fulcrum

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(b) Second-class lever Arrangement of the elements is

fulcrum-load-effort

In the body: Second-class leverage is

exerted when you stand on tip-toe The effort is exerted by the calf muscles pulling upward on the heel; the joints of the ball of the foot are the fulcrum; and the weight of the body is the load.

Load Effort

Fulcrum

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• Effort applied between fulcrum and load

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(c) Third-class lever Arrangement of the elements is

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(c) Third-class lever Arrangement of the elements is

load-effort-fulcrum

In the body: Flexing the forearm by the biceps brachii muscle exemplifies third-class leverage The effort is exerted

on the proximal radius of the forearm, the fulcrum is the elbow joint, and the load is the hand and distal end of the forearm.

Load

Effort

Fulcrum

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Major Skeletal Muscles of the Body

• Grouped by function and location

• Information for each muscle

• Name and description—note information in the name

• Origin and insertion—there is usually a joint between the origin and the insertion

• Action—insertion moves toward origin; best learned by acting out muscle movement on one’s own body

• Innervation—name of major nerve that supplies the

muscle

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Pectineus Rectus femoris Vastus lateralis Vastus medialis

Fibularis longus Extensor digitorum longus Tibialis anterior

Temporalis Epicranius, frontal belly

Orbicularis oculi Zygomaticus Orbicularis oris

Sternohyoid Sternocleidomastoid

Pectoralis major

Pectoralis minor Serratus anterior Intercostals

External oblique

Rectus abdominis Internal oblique Transversus abdominis

Sartorius

Tensor fasciae latae Adductor longus Gracilis

Gastrocnemius Soleus

Masseter

Platysma

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Arm

Triceps brachii Brachialis

Forearm

Brachioradialis

Extensor carpi ulnaris

Extensor digitorum

Iliotibial tract

Leg

Gastrocnemius Soleus

Thigh

Biceps femoris

Adductor magnus

Semitendinosus Semimembranosus

Latissimus dorsi Rhomboid major

Infraspinatus

Deltoid Teres major

Flexor carpi ulnaris

Extensor carpi radialis longus

Calcaneal (Achilles) tendon

Hamstrings:

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Muscles of the Head

1 Muscles of facial expression

2 Muscles of mastication and tongue

movement

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Muscles of Facial Expression

nerve)

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Muscles of Facial Expression

pulling the scalp forward and backward

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Frontal belly

Occipital belly

Temporalis

Masseter Sternocleidomastoid Trapezius

Splenius capitis

Epicranius

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Muscles of Mastication and Tongue Movement

• Prime movers of jaw closure

• Temporalis and masseter

• Grinding movements

• Medial and lateral pterygoids

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Muscles of Mastication and Tongue

Movement

(trigeminal nerve)

group) also help by holding food between the teeth

(hypoglossal nerve)

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Orbicularis

oris

Temporalis

Masseter Buccinator

(a)

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Muscles of Mastication and Tongue Movement

PLAY A&P Flix™: Temporalis

PLAY A&P Flix™: Masseter

PLAY A&P Flix™: Buccinator

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Lateral pterygoid Medial pterygoid

Masseter pulled away

(b)

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Styloglossus Hyoglossus

Stylohyoid Hyoid bone Thyrohyoid

Genioglossus

Mandibular

symphysis

Geniohyoid Thyroid cartilage

(c)

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Muscles of the Anterior Neck and Throat

1 Suprahyoid

2 Infrahyoid

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Suprahyoid Muscles of the Anterior Neck

and Throat

(they move the hyoid bone and larynx)

• Form the floor of the oral cavity

• Anchor the tongue

• Move the hyoid bone and the larynx

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Infrahyoid Muscles of the Anterior Neck and Throat

larynx as swallowing ends and during

speaking

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Mylohyoid

Anterior belly Posterior belly

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Buccinator

Tensor veli palatini

Levator veli palatini

cartilage

of larynx Trachea Styloid process

(c)

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Infrahyoid Muscles of the Anterior Neck and Throat

PLAY Animation: Rotatable face

PLAY Animation: Rotatable head

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Muscles of the Neck and Vertebral Column

• Muscles that move the head

• Muscles that extend the trunk and maintain posture

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Muscles of the Neck and Vertebral Column: Head Movement

extension, rotation, and lateral bending

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Middle scalene Anterior scalene Posterior scalene

Mastoid process

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Splenius capitis

Spinous processes

of the vertebrae

Splenius cervicis

Mastoid process

(b) Posterior

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Muscles of the Neck and Vertebral Column: Head Movement

PLAY A&P Flix™: Semispinalis capitis

PLAY A&P Flix™: Splenius capitis

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Muscles of the Neck and Vertebral Column: Trunk Extension

• Erector spinae (sacrospinalis) group—prime movers of back extension and lateral bending

• Iliocostalis

• Longissimus

• Spinalis

• Semispinalis and quadratus lumborum—

synergists in extension and rotation

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Mastoid process

capitis Semispinalis cervicis

Multifidus

Quadratus lumborum

Semispinalis thoracis

Longissimus capitis Iliocostalis cervicis

Erector

Ligamentum nuchae

(d)

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Muscles of the Neck and Vertebral Column: Trunk Extension

PLAY A&P Flix™: Longissimus

PLAY A&P Flix™: Iliocostalis

PLAY A&P Flix™: Spinalis

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