The Skeletal Muscle System

internal oblique

Deep to the external oblique Flexes and rotates the vertebral column. Can also compress the abdomen. This is useful in urination, vomiting, defecation, and childbirth because this muscle can powerfully compress the contents of the abdomen

gluteus minimus

Deep to the gluteus medius is the _____ _____. It also abducts and medially rotates the thigh.

The largest part of the muscle, which actually contains the muscle cells

Belly—

palmaris longus

Can only flex the hand due to its location

triceps brachii

Works to extend the forearm at the elbows

teres major

Works with the latissimus dorsi to adduct, extend, and medially rotate the arm. Like the latissimus dorsi, it inserts on the inside of the humerus

rhomboideus major

Works with the levator scapulae, the trapezius, the serratus anterior, and the pectoralis minor to move the scapula. This provides for a wide range of motion, and it also helps to stabilize the scapula, which is quite movable

rhomboideus minor

Works with the levator scapulae, the trapezius, the serratus anterior, and the pectoralis minor to move the scapula. This provides for a wide range of motion, and it also helps to stabilize the scapula, which is quite movable

cleido

____ refers to clavicle.

adductor magnus

"The adductor longus and the _____ _______ work together to adduct the thigh. These are the muscles that will ache after a horseback ride, unless you ride regularly. They also work together to laterally rotate the thigh. They are antagonists when it comes to flexion and extension, however. Extends the thigh.

first-class lever

A child sits on one end and another child sits on the other end. The fulcrum is in the middle. One child's weight is the effort, which lifts the other child (the resistance) up. So, the fulcrum is between the effort and resistance.

second-class lever

A common example of a _____-_____ lever is the wheelbarrow. In this kind of lever, the resistance is between the fulcrum and the effort.

flexor digitorum profundus

A deeper muscle that aids the flexor digitorum superficialis in its function.

fulcrum

A muscle, then, creates a pull on a lever made out of bone. A lever consists of a rigid bar that rotates around a fixed point called the ________.

pectoralis major

Adducts, flexes, and medially rotates the arm

brachioradialis

Aids the biceps brachii in flexing the forearm.

pronator quadratus

Aids the pronator teres in pronating the forearm at the elbow

flexor carpi ulnaris

Also flexes the hand. Rather than abducting the hand, however, the ____ ____ ____ acts as the antagonist of the flexor carpi radialis, adducting the hand.

transversus abdominis

Deep to the internal oblique Flexes and rotates the vertebral column. Can also compress the abdomen. This is useful in urination, vomiting, defecation, and childbirth because this muscle can powerfully compress the contents of the abdomen

zygomatic major

Elevates and draws the corners of the mouth laterally

frontalis

Elevates the eyebrows and wrinkles the forehead

pectoralis minor

Elevates the ribs, as in taking a deep breath, and depresses the scapula, as in pulling down on something above your head. It is located deep to the pectoralis major

extensor carpi radialis brevis

Extends and abducts the hand, shorter then the extensor carpi radialis longus

extensor carpi radialis longus

Extends and abducts the hand.

Muscles in the forearm that create movement in the hands or fingers

Extrinsic hand muscles—

external oblique

Flexes and rotates the vertebral column. Can also compress the abdomen. This is useful in urination, vomiting, defecation, and childbirth because this muscle can powerfully compress the contents of the abdomen

rectus abdominis

Flexes and rotates the vertebral column. Can also compress the abdomen. This is useful in urination, vomiting, defecation, and childbirth because this muscle can powerfully compress the contents of the abdomen

serratus anterior

Flexes and rotates the vertebral column. Can also compress the abdomen. This is useful in urination, vomiting, defecation, and childbirth because this muscle can powerfully compress the contents of the abdomen

biceps brachii

Flexes the forearm at the elbow. When you flex your forearm to show your muscle, the muscle that you see bulging is the ____ ____

prime mover or agonist

If one muscle is more important than the others in creating that movement, it is called the _____ ____ or ____.

linea alba or "white line"

If you are a relatively muscular person with little body fat, you can see a thin line that runs down the center of the abdominal wall. It starts near the end of the sternum and runs through the navel to the pubis. This is called the _____ _____, or "____ _____." It is not a muscle, and that is why it is labeled in blue ink. Instead, this is a band of connective tissue that binds all of the abdominal muscles.

third-class lever

In a ___-____ lever, the effort is between the fulcrum and the resistance. Depending on how you use a shovel, it can act as such a lever. When you hold the handle of the shovel still and lift the contents of the shovel with your other hand, you are using the shovel as a ___-_____ lever. One of the many examples of such a lever in your body is your forearm. When the biceps brachii pulls on your radius, your elbow acts as the fulcrum, and the items in your hand (the resistance) are lifted. This kind of lever actually requires a much greater force to be used as the effort, but the resistance can be lifted much farther than it can in the other two types of levers.

origins

In the limbs, the ____ are usually more proximal.

insertions

In the limbs, the _____ are usually more distal.

insertions

In the trunk, the _____ are usually more lateral.

origins

In the trunk, the _____ are usually more medial.

The point at which a muscle's tendon attaches to the more moveable bone

Insertion—

occipitofrontalis

Is a muscle made of two muscle bellies

extensor digitorum

Is the antagonist of the flexor digitorum superficialis, as it extends the hand and the four fingers (not the thumb).

sartorius

Is the longest muscle in the body. It flexes and laterally rotates the thigh, and also flexes the leg. When you sit on the floor cross-legged, you are using all three actions of your ________.

sternocleidomastoid

Is the prime mover of the muscles that rotate and flex the neck

gluteus maximus

It extends, abducts, and laterally rotates the thigh. Because it powerfully extends the thigh, it is a very important muscle for running.

extensor retinaculum

It is like a bracelet of dense regular connective tissue that winds around the wrist, covering the extensor tendons. This holds the tendons down as the muscles work. If it were not for the _____ _______, the extensor tendons would bow outward when the extensors contracted.

trapezius

It is sometimes called the shoulder-shrugging muscle, as it can also elevate, depress, and retract the scapula. To retract the scapula means to pull it back.

brachii

Latin for "of the arm"

biceps

Latin for two heads

the process of chewing

Mastication—

Muscle size; muscle shape; location of the muscle; orientation of the muscle's fascicles; muscle origin and insertion; number of heads (origins) on the muscle; and muscle function

Muscles are named in Latin for the following reasons: *These are not set rules though

orbicularis oris

Nicknamed the "kissing muscle" because it is in charge of the pursing motion of the lips

infraspinatus

One of the four muscles that provide joint security and are often called the rotator cuff muscles, the rotocuff, or the musculotendinous cuff.

subscapularis

One of the four muscles that provide joint security and are often called the rotator cuff muscles, the rotocuff, or the musculotendinous cuff.

supraspinatus

One of the four muscles that provide joint security and are often called the rotator cuff muscles, the rotocuff, or the musculotendinous cuff.

teres minor

One of the four muscles that provide joint security and are often called the rotator cuff muscles, the rotocuff, or the musculotendinous cuff.

biceps femoris

One of the three muscles are known collectively as the hamstring muscle group. Their main jobs are to flex the leg and extend the thigh. They flex the leg if other muscles stabilize the thigh, preventing it from moving.

semimembranosus

One of the three muscles are known collectively as the hamstring muscle group. Their main jobs are to flex the leg and extend the thigh. They flex the leg if other muscles stabilize the thigh, preventing it from moving.

semitendinosus

One of the three muscles are known collectively as the hamstring muscle group. Their main jobs are to flex the leg and extend the thigh. They flex the leg if other muscles stabilize the thigh, preventing it from moving.

The point at which a muscle's tendon attaches to the more stationary bone

Origin—

pronator teres

Pronates the forearm at the elbow, turning the forearm to a palms-down movement

platysma

Pulls the corners of the mouth down into a frown

straight

Rectus means _____

posterior triangle

Rotates and flexes the head

gluteus medius

Runs deep to the gluteus maximus. This is one of the most common parts of the body into which a health practitioner will inject medicine if an intramuscular injection is necessary. Why? The ______ ______ is far from the sciatic nerve, a major nerve in the buttocks that can be injured by the injection needle. The ______ ______ abducts and medially rotates the thigh.

supinator

Supinates the forearm, which turns the palm upward. The biceps brachii, because of its point of insertion at the radius, aids the ____ in this function

buccinator

The "cheek muscle" which is in charge of the rapid change in volume of the oral cavity

medial pterygoid

The _____ _______ elevates the mandible (along with the masseter and temporalis) in order to close the mouth.

lateral pterygoid

The ______ _______ depresses (lowers) the mandible. It is used to open the mouth.

rectus femoris

The _______ _____, the vastus lateralis, the vastus intermedius, and the vastus medialis are together called the quadriceps femoris. They are grouped together in this way because their insertions are all on a process of the tibia, the bump that you can feel on the tibia below the patella. In addition, the ______ ____ flexes the thigh.

deltoid

The _______ muscle packs three different groups of fascicles into one muscle. The anterior muscle fascicles in the _____ flex the arm. This means that the arm is raised up, as you would do if you pointed straight ahead. The lateral fascicles abduct the arm, bringing them straight out away from the body. Finally, the posterior fascicles extend the arm, which brings it from a flexed position back to the anatomical position.

gracilis

The ________ adducts the thigh and flexes the leg.

masseter

The ________ powerfully elevates the mandible, and it can be used to protract the mandible (to push the lower jaw forward)

temporalis

The _________ muscle's fascicles converge on the mandible, enabling the _______ to elevate the mandible powerfully. It also can be used to retract the mandible (to pull the jaw backward)

gastrocnemius

The __________ and soleus muscles form the bulge on the posterior side of the leg that is commonly called the calf. They both plantarflex the foot (which is the motion of standing on your tiptoes), and the ______ also flexes the leg. They insert into the calcaneus (heel bone) via the calcaneal tendon.

orbicularis oculi

The cause of closing the eye, such as winking

soleus

The gastrocnemius (gas trok nee' me us) and ________ muscles form the bulge on the posterior side of the leg that is commonly called the calf. They both plantarflex the foot (which is the motion of standing on your tiptoes). They insert into the calcaneus (heel bone) via the calcaneal tendon.

Achilles tendon

The gastrocnemius and soleus muscles insert into the calcaneus (heel bone) via the calcaneal tendon. This is also called the _____ ______, and is often the site of injury in athletes. Why is it called the ______ ______? This is a reference to the Greek legend of _____, a hero whose mother dipped him into the river Styx to make him invincible. However, she had to hold onto him when she dipped him into the river, so she held onto his heel. So, his heel was not covered in the water, and that was his only vulnerable spot.

is that muscles never work individually, even though we study them that way. They generally work in groups of two or more.

The most important thing to remember about muscle action:

first-class lever

The posterior neck muscles which tilt your head up are an example of such a lever in your body. The muscles pull down on the back of the head. The joint between your skull and your first cervical vertebra is the fulcrum, and your head is the resistance. Since the resistance is near the fulcrum, only a small effort is needed to pull a large resistance

vastus lateralis

The rectus femoris, the _____ _______, the vastus intermedius, and the vastus medialis are together called the quadriceps femoris. They are grouped together in this way because their insertions are all on a process of the tibia, the bump that you can feel on the tibia below the patella. The quadriceps femoris extends the leg.

brachium

The term ______ is Latin for "upper arm."

640

There are _____ individual skeletal muscles

the biceps brachii contract while the triceps brachii relax

To flex the forearm, what occurs?

supraspinatus, infraspinatus, teres minor, and subscapularis

To provide maximum range of motion, the socket is rather shallow. In addition, because ligaments reduce the range of motion in a joint, the ball of the humerus is held into the socket of the scapula by muscle tension during shoulder movements. The four muscles that cause this tension are the _____, _______, ____ _____, and _____.

force and weight

When a ___ (the effort) is applied, a _____ (the resistance) is moved.

antagonist

When a muscle works opposite of another muscle, it is called an _______

synergists

When muscles work together to create the same movement, they are called ______.

extensor carpi ulnaris

While the _____ _____ _____ extends the hand with extensor carpi radialis longus and extensor carpi radialis brevis above, it is also an antagonist to those same muscles because it adducts the hand.

latissimus dorsi

Works opposite the deltoid to adduct the arm. In other words, it brings an arm that is pointing sideways from the trunk back to anatomical position. It also medially rotates and extends the arm. It is a medial rotator of the arm, not a lateral rotator, as you might think, because it originates in the vertebral column, but its insertion is on the inside of the humerus, not on the outside.

zygomatic minor

elevates the upper lip

flexor carpi radialis

flexes and abducts the hand

flexor digitorum superficialis

flexes both the wrist and the four fingers (not the thumb) to which it inserts.

second-class lever

n your foot, your calf muscles pull on your heel. The ball of your foot acts as the fulcrum. Using this ____-_____ lever, your calf muscles can lift the entire weight of your body, but only a short distance. When you stand on your tiptoes, then, you are using this ___-____ lever so that one set of muscles lifts your entire body.