Muscular System
Chapter 6
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
Muscle Types (cont.)
Nuclei
Striations Intercalated
Disks
Voluntary or
Involuntary
Movement
Cardiac
Uninucleated
Yes
Yes
Involuntary
Skeletal
Multinucleated
Yes
No
Voluntary
Smooth
Uninucleated
No
No
Involuntary
Tendons and Ligaments


Tendon – connective tissue that attaches
muscle to bone
Ligament – connective tissue that attaches
bone to bone
Tendons and Ligaments (cont.)
Muscle Functions




Produces movement
Generates heat
Maintains posture
Stabilizes joints
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
Microscopic Anatomy of Skeletal Muscle
Skeletal Muscle Activity



Electronic impulses originate in the brain
Electricity travels through the nervous system
Nerves attach to muscle fibers
Skeletal Muscle Activity

Electricity causes SR to release Ca2+ ions which
start myosin heads to bind with actin tails



Sarcoplasmic reticulum (SR) – a specialized smooth ER
that store calcium (Ca2+)
Example: myosin - fish hooks
actin - chains
The end result is muscle contraction
Skeletal Muscle Activity
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.
Types of Body Movements

Flexion – a movement that decreases the
angle of the joint and brings two bones closer
together
Types of Body Movements

Extension – a movement that increases the
angle, or distance, between two bones or
parts of the body
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
Types of Body Movements

Rotation – movement of a bone around its
longitudinal axis

Ex. – Shoulder and head
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
Gross Anatomy of Skeletal Muscles

Head Muscles
Facial Muscles

Frontalis – Covers the frontal bone

Raises eyebrows and wrinkles forehead
Frontalis
Temporalis
Zygomaticus
Masseter
Buccinator
Orbicularis oris
Platysma
Orbicularis oculi
Facial Muscles

Orbicularis Oculi

Close eyes, squint, blink, and wink
Orbicularis oculi
Frontalis
Temporalis
Zygomaticus
Masseter
Buccinator
Orbicularis oris
Platysma
Facial Muscles

Orbicularis oris

Closes the mouth and protrudes the lips
Frontalis
Temporalis
Zygomaticus
Masseter
Buccinator
Orbicularis oris
Platysma
Orbicularis oculi
Facial Muscles

Buccinator


Flattens the cheek (as in whistling)
Aids in chewing
Orbicularis oculi
Frontalis
Temporalis
Zygomaticus
Masseter
Buccinator
Orbicularis oris
Platysma
Facial Muscles

Zygomaticus

“Smiling” muscle

Orbicularis oculi
Raises the corners of the mouth upward
Frontalis
Temporalis
Zygomaticus
Masseter
Buccinator
Orbicularis oris
Platysma
Facial Muscles

Masseter

Closes the jaw
Orbicularis oculi
Frontalis
Temporalis
Zygomaticus
Masseter
Buccinator
Orbicularis oris
Platysma
Facial Muscles

Temporalis

Helps close the jaw
Orbicularis oculi
Frontalis
Temporalis
Zygomaticus
Masseter
Buccinator
Orbicularis oris
Platysma
Gross Anatomy of Skeletal Muscles

Trunk and Neck Muscles
Anterior Muscles

Platysma

Pulls the corners of the mouth inferiorly
Frontalis
Temporalis
Zygomaticus
Masseter
Buccinator
Orbicularis oris
Platysma
Orbicularis oculi
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
rotates toward the
opposite side
Anterior Muscles

Pectoralis Major


Covers the upper part of the chest
Adduct and flex the arm
Anterior Muscles

Pectoralis Minor


Lies deep to the pectoralis major
Draws down the scapula or raises the ribs
Anterior Muscles

Intercostal Muscles


Deep muscles found between the ribs
Help raise and depress the rib cage for breathing
Anterior Muscles
Transverse
abdominis

Aponeurosis
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
Internal
oblique
External
oblique
Rectus
abdominis
Anterior Muscles
Transverse
abdominis

Aponeurosis
External oblique



Make up the lateral walls
of the abdomen
Flex the vertebral column
Rotate the trunk and
bend it laterally
Internal
oblique
External
oblique
Rectus
abdominis
Anterior Muscles
Transverse
abdominis

Aponeurosis
Internal oblique


Deep to the external
oblique
Same functions as the
external oblique
Internal
oblique
External
oblique
Rectus
abdominis
Anterior Muscles
Transverse
abdominis

Aponeurosis
Transverse abdominis


The deepest muscle of
the abdominal wall
Compresses the
abdominal contents
Internal
oblique
External
oblique
Rectus
abdominis
Anterior Muscles
Transverse
abdominis

Aponeurosis
Aponeurosis

A sheetlike tendinous
expansion, mainly
serving to connect a
muscle with the parts it
moves
Internal
oblique
External
oblique
Rectus
abdominis
Posterior Muscles

Trapezius



Most superficial muscles
of the posterior neck and
upper trunk
Extend the head
Elevate, depress, and
adduct the scapula
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
Posterior Muscles

Deltoid


The main muscles for
arm abduction
A favored injection site of
medication less than 5ml
(must be given
intramuscularly)
Gross Anatomy of Skeletal Muscles

Muscles of the Humerus

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”

Triceps brachii


The main muscle for
elbow extension
Called the “boxer’s”
muscle because it can
deliver a straight-arm
knockout punch