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.