muscular system chapter 6. muscle types skeletal muscles – attach to the body’s skeleton cardiac...

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 – attaches muscle to bone Ligament – 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

Orbicularis oris

Temporalis

Orbicularis oculi

Masseter

Frontalis

Zygomaticus

Platysma

Buccinator

Facial Muscles

Orbicularis Oculi Close eyes, squint, blink, and wink

Orbicularis oris

Temporalis

Orbicularis oculi

Masseter

Frontalis

Zygomaticus

Platysma

Buccinator

Facial Muscles

Orbicularis oris Closes the mouth and protrudes the lips

Orbicularis oris

Temporalis

Orbicularis oculi

Masseter

Frontalis

Zygomaticus

Platysma

Buccinator

Facial Muscles

Buccinator Flattens the cheek (as in whistling) Aids in chewing

Orbicularis oris

Temporalis

Orbicularis oculi

Masseter

Frontalis

Zygomaticus

Platysma

Buccinator

Facial Muscles

Zygomaticus “Smiling” muscle

Raises the corners of the mouth upward

Orbicularis oris

Temporalis

Orbicularis oculi

Masseter

Frontalis

Zygomaticus

Platysma

Buccinator

Facial Muscles

Masseter Closes the jaw

Orbicularis oris

Temporalis

Orbicularis oculi

Masseter

Frontalis

Zygomaticus

Platysma

Buccinator

Facial Muscles

Temporalis Helps closes the jaw

Orbicularis oris

Temporalis

Orbicularis oculi

Masseter

Frontalis

Zygomaticus

Platysma

Buccinator

Gross Anatomy of Skeletal Muscles Trunk and Neck Muscles

Anterior Muscles

Platysma Pulls the corners of the mouth inferiorly

Orbicularis oris

Temporalis

Orbicularis oculi

Masseter

Frontalis

Zygomaticus

Platysma

Buccinator

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

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

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

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

Anterior Muscles

Internal oblique Deep to the external

obliques Same functions as the

external obliques

Aponeurosis

Rectus abdominis

External oblique

Internal oblique

Transverse abdominis

Anterior Muscles

Transverse abdominis The deepest muscle of

the abdominal wall Compresses the

abdominal contents

Aponeurosis

Rectus abdominis

External oblique

Internal oblique

Transverse abdominis

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

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