Agonist	Antagonist	Action(s)
Biceps brachii: anterior upper arm	Triceps brachii: posterior upper arm	The biceps brachii flexes the forearm, whereas the triceps brachii extends it.
Hamstrings: group of three muscles in the posterior thigh	Quadriceps femoris: group of four muscles in the anterior thigh	The hamstrings flex the lower leg, whereas the quadriceps femoris extend it.

There are also skeletal muscles that do not pull against the skeleton for movements. For example, there are the muscles that produce facial expressions. The insertions and origins of facial muscles are in the skin allowing muscles to contract to form a smile or frown, form sounds or words, and raise the eyebrows. There also are skeletal muscles in the tongue, and the external urinary and anal sphincters that allow for voluntary control of urination and defecation. In addition, the diaphragm contracts and relaxes to change the volume of the thoracic cavity during breathing but it does not move the skeleton to do this.

Exercise and Stretching

When exercising, it is important to first warm up the muscles. Stretching pulls on the muscle fibers and results in an increased blood flow to the muscles being worked. Without a proper warm-up, it is possible to damage some of the muscle fibers or pull a tendon. A pulled tendon, regardless of location, results in pain, swelling, and diminished function.

Most of the joints used during exercise are synovial joints, which have synovial fluid in the joint space between two bones. Exercise and stretching may have a beneficial effect on synovial joints. Synovial fluid is a thin, but viscous film with the consistency of egg whites. After proper stretching and warm-up, the synovial fluid may become less viscous, allowing for better joint function.

Skeletal Muscle Actions

There are many types of actions that are caused by the contraction of muscles, such as flexion, extension, abduction, adduction, rotation, dorsiflexion, plantar flexion, supination, and pronation. These muscle actions are summarized in Table 7.3.

Table 7.3 Muscle Actions

See Figures 7.13 and 7.14 for illustrations of muscle actions.

 

Figure 7.13  Flexion, Extension, Adduction, Abduction, Circumduction, and Rotation^[3]

 

 

Figure 7.14 Pronation, Supination, Dorsiflexion, Plantar Flexion, Inversion, Eversion, Protraction, Retraction, Elevation, Depression, and Opposition^[4]

 

Patterns of Fascicle Organization

As previously discussed in this chapter, skeletal muscle is surrounded by connective tissue at three levels. Each muscle fiber (cell) is covered by endomysium and the entire muscle is covered by epimysium. Groups of muscle fibers are “bundled” into fascicles and covered by connective tissue called perimysium. Fascicle arrangement by perimysium is correlated to the force generated by a muscle; it also affects the range of motion of the muscle. Based on the patterns of fascicle arrangement, skeletal muscles can be classified in several ways. The following are the most common fascicle arrangements.

Parallel muscles have fascicles that are arranged in the same direction as the long axis of the muscle.The majority of skeletal muscles in the body have this type of organization. Some parallel muscles are flat sheets that expand at the ends to make broad attachments. Other parallel muscles are rounder with tendons at one or both ends. Muscles that seem to be plump have a large mass of tissue located in the middle of the muscle, between the insertion and the origin, which is known as the central body. A more common name for this is belly. When a muscle contracts, the contractile fibers shorten it to an even larger bulge. For example, extend and then flex your biceps brachii muscle; the large, middle section is the belly. See Figure 7.15 for an image of the biceps brachii muscle. When a parallel muscle has a central, large belly that is spindle-shaped, meaning it tapers as it extends to its origin and insertion, it sometimes is called fusiform.

Figure 7.15 Biceps Brachii Muscle Contraction (Source: https://openstax.org/books/anatomy-and-physiology-2e/pages/11-1-interactions-of-skeletal-muscles-their-fascicle-arrangement-and-their-lever-systems#fig-ch11_01_03)

 

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Circular muscles are also called sphincters. When they relax, the sphincters’ circularly arranged bundles of muscle fibers increase the size of the opening, and when they contract, the size of the opening shrinks to close. The orbicularis oris muscle is a circular muscle that goes around the mouth. When it contracts, the oral opening becomes smaller, as when puckering the lips for whistling. Another example is the orbicularis oculi, muscles which surround each eye. Notice the names of the two orbicularis muscles (orbicularis oris and orbicularis oculi), where part of the first name of both muscles is the same. The first part of orbicularis, orb (orb = “circular”), is a reference to a round or circular structure; it may also make one think of orbit, such as the moon’s path around the earth. The word oris (oris = “oral”) refers to the oral cavity, or the mouth. The word oculi (ocular = “eye”) refers to the eye.

There are other muscles throughout the body named by their shape or location. The deltoid is a large, triangular-shaped muscle that covers the shoulder. It is so-named because the Greek letter delta looks like a triangle. The rectus abdominis (rector = “straight”) is the straight muscle in the anterior wall of the abdomen, while the rectus femoris is the straight muscle in the anterior compartment of the thigh.

When a muscle has a widespread expansion over a sizable area, but then the fascicles come to a single, common attachment point, the muscle is called convergent. The attachment point for a convergent muscle could be a tendon, an aponeurosis (a flat, broad tendon), or a raphe (a very slender tendon). The large muscle on the chest, the pectoralis major, is an example of a convergent muscle because it converges on the greater tubercle of the humerus via a tendon. The temporalis muscle of the cranium is another. Pennate muscles (penna = “feathers”) blend into a tendon that runs through the central region of the muscle for its whole length, somewhat like the quill of a feather with the muscle arranged similar to the feathers. Due to this design, the muscle fibers in a pennate muscle can only pull at an angle, and as a result, contracting pennate muscles do not move their tendons very far. However, because a pennate muscle generally can hold more muscle fibers within it, it can produce relatively more tension for its size. In a unipennate muscle, the fascicles are located on one side of the tendon. The extensor digitorum of the forearm is an example of a unipennate muscle. A bipennate muscle has fascicles on both sides of the tendon. In some pennate muscles, the muscle fibers wrap around the tendon, sometimes forming individual fascicles in the process. This arrangement is referred to as multipennate. A common example is the deltoid muscle of the shoulder, which covers the shoulder but has a single tendon that inserts on the deltoid tuberosity of the humerus.

See Figure 7.16  for an illustration of the seven different muscle shapes.

Figure 7.16 Muscle Shapes and Fiber Alignment (https://openstax.org/books/anatomy-and-physiology-2e/pages/11-1-interactions-of-skeletal-muscles-their-fascicle-arrangement-and-their-lever-systems#fig-ch11_01_03)

 

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Naming Skeletal Muscles

The Greeks and Romans conducted the first studies done on the human body in Western culture. Subsequent societies studied Latin and Greek, and therefore the early pioneers of anatomy continued to apply Latin and Greek terminology or roots when they named the skeletal muscles.

The large number of muscles in the body and unfamiliar words can make learning the names of the muscles in the body seem daunting, but understanding the etymology can help. Etymology is the study of how the root of a particular word entered a language and how the use of the word evolved over time. Taking the time to learn the roots of the words is crucial to understanding the vocabulary of anatomy and physiology. When you understand the names of muscles it will help you remember where the muscles are located and what they do. See Table 7.4 for some examples of Latin root words and their meanings related to muscles. Table 7.5 provides some mnemonic devices for common Latin roots found in muscle names. Pronunciation of words and terms will take a bit of time to master, but after some basic information, the correct names and pronunciations will become easier.

Table 7.4 Understanding a Muscle Name from the Latin^[7]

 

Table 7.5 Memory Tips for Latin Roots^[8]

Anatomists name the skeletal muscles according to a number of criteria, each describing the muscle in some way. These include naming the muscle after its shape, its size compared to other muscles in the area, its location in the body or the location of its attachments to the skeleton, how many origins it has, or its action.

The skeletal muscle’s anatomical location or its relationship to a particular bone often determines its name. For example, the frontalis muscle is located anterior to the frontal bone of the skull. Similarly, the shapes of some muscles are very distinctive and the names, such as orbicularis, reflect the shape. For the buttocks, the size of the muscles influences the names: gluteus maximus (largest), gluteus medius (medium), and the gluteus minimus (smallest). Gluteus means buttocks. Names  can indicate length—brevis (short), longus (long)—and identify position relative to the midline: lateralis (away from the midline), and medialis (toward the midline). The direction of the muscle fibers and fascicles are used to describe muscles relative to the midline, such as the rectus (straight) abdominis, or the oblique (at an angle) muscles of the abdomen.

Some muscle names indicate the number of muscles in a group. One example of this is the quadriceps femoris, a group of four muscles located on the anterior thigh. Other muscle names can provide information as to how many origins a particular muscle has, such as the biceps brachii. The prefix bi indicates that the muscle has two origins and tri, in triceps brachii, indicates three origins.

The location of a muscle’s attachment can also appear in its name. When the name of a muscle is based on the attachments, the origin is always named first. For instance, the sternocleidomastoid muscle of the neck has a dual origin on the sternum (sterno) and clavicle (cleido), and it inserts on the mastoid process of the temporal bone.

The last feature by which a muscle is named is its action. When muscles are named for the movement they produce, one can find action words in their name. Some examples are flexor (decreases the angle at the joint), extensor (increases the angle at the joint), abductor (moves the bone away from the midline), or adductor (moves the bone toward the midline).

The skeletal muscles are divided into axial (muscles of the trunk and head) and appendicular (muscles of the arms and legs) categories. This system reflects the bones of the skeletal system, which are also arranged in this manner. The axial muscles are grouped based on location, function, or both.

Major Skeletal Muscles

See Figure 7.17 for an illustration of the major skeletal muscles of the human body. Functions of muscles are further described in the following subsections.

Figure 7.17 Major Skeletal Muscles (https://openstax.org/books/anatomy-and-physiology-2e/pages/11-2-naming-skeletal-muscles

Muscles That Create Facial Expression

The origins of the muscles of facial expression are on the surface of the skull (remember, the origin of a muscle does not move). The insertions of these muscles have fibers intertwined with connective tissue and the dermis of the skin. Because the muscles insert in the skin rather than on bone, when they contract, the skin moves to create facial expression. See Figure 7.18 for an illustration of the muscles that create facial expressions.

Figure 7.18 Muscles of Facial Expressions (https://openstax.org/books/anatomy-and-physiology-2e/pages/11-3-axial-muscles-of-the-head-neck-and-back#fig-ch11_03_01 )

 

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Muscles that create facial expressions include the following:

• Occipitofrontalis: Muscle that raises the eyebrows and wrinkles the forehead. The muscle has a frontal belly and an occipital belly (near the occipital bone on the posterior part of the skull). The muscle on the forehead is the frontalis and the one on the back of the head is the occipitalis, but there is no muscle across the top of the head. Instead, the two bellies are connected by a broad tendon called the epicranial aponeurosis, or galea aponeurosis (galea = “helmet”).
• Orbicularis oris: The circular muscle around the mouth that compresses and puckers the lips.
• Orbicularis oculi: The circular muscle around each eye that closes the eye(s).
• Buccinator: Muscle found in the cheeks that allows you to whistle, blow, and suck. It also contributes to the action of chewing.
• Zygomaticus: Muscle from the zygomatic bone to the mouth. The “smiling’ muscle.

Muscles That Move the Eyes

• Extrinsic Eye Muscles: The movement of the eyeball is under the control of the extrinsic eye muscles, which originate outside the eye and insert onto the outer surface of the white of the eye. These muscles are located inside the eye socket and cannot be seen on any part of the visible eyeball. See Figure 7.19 for an illustration of the extrinsic eye muscles.

Figure 7.19 Muscles of the Eyes (a) The extrinsic eye muscles originate outside of the eye on the skull. (b) Each muscle inserts onto the eyeball (https://openstax.org/books/anatomy-and-physiology-2e/pages/11-3-axial-muscles-of-the-head-neck-and-back#fig-ch11_03_03)

 

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Muscles That Move the Lower Jaw

In anatomical terminology, chewing is called mastication. Muscles involved in chewing must be able to exert enough pressure to bite through and then chew food before it is swallowed. The muscles of mastication include the masseter and the temporalis.

• Masseter: The main muscle used for chewing because it lifts the mandible (lower jaw) to close the mouth.
• Temporalis: The muscle that lifts and pulls back the mandible. You can feel the temporalis move by putting your fingers to your temple as you chew.

See Figure 7.20 for an illustration of the masseter and temporalis muscles.

Figure 7.20 Masseter and Temporalis Muscles That Move the Lower Jaw (https://openstax.org/books/anatomy-and-physiology-2e/pages/11-3-axial-muscles-of-the-head-neck-and-back)

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Muscles That Move the Head

The head, attached to the top of the vertebral column, is balanced, moved, and rotated by the neck muscles. When these muscles contract, they can rotate, flex or extend. The major muscle that moves the head is the sternocleidomastoid.

• Sternocleidomastoid: Major muscle that laterally flexes and rotates the head. When both of them contract, the head flexes at the neck. It has a dual origin on the sternum (stern/o) and clavicle (cleid/o) and inserts on the mastoid process of the temporal bone. Place your fingers on both sides of the neck and turn your head to the left and to the right to feel the movement of this muscle. See Figure 7.21 for an illustration of the sternocleidomastoid.

Figure 7.21 Posterior and Lateral Views of the Neck Showing the Sternocleidomastoid Muscle (https://openstax.org/books/anatomy-and-physiology-2e/pages/11-3-axial-muscles-of-the-head-neck-and-back#fig-ch11_03_07)

 

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See Table 7.A in the “Chapter Resources” section for a description of the movements by the muscles that move the head.

Table 7.A Movements of the Muscles That Move the Head

Major Muscles of the Abdomen

There are four pairs of abdominal muscles that cover the anterior and lateral abdominal region and meet at the anterior midline. These paired muscles of the anterolateral abdominal wall can be divided into four groups: the external obliques, the internal obliques, the transversus abdominis, and the rectus abdominis. The different orientations of these muscles allows various movements and rotations of the trunk. The three layers of muscle also help to protect the internal abdominal organs in an area where there is no bone.

• External oblique(s): Flat superficial skeletal muscle in the antero-lateral wall of the abdomen. The external oblique is closest to the surface and extends inferiorly and medially, in the direction of sliding one’s four fingers into pants pockets.
• Internal oblique(s): Perpendicular to the external oblique is the intermediate internal oblique, extending superiorly and medially, the direction the thumbs usually go when the other fingers are in the pants pocket.
• Transverse abdominis: The deep muscle is the transversus abdominis. It is arranged transversely around the abdomen, similar to the front of a belt on a pair of pants.
• Rectus abdominis: The straight muscle in the anterior wall of the abdomen, commonly called the “sit-up” muscle. It originates at the pubic crest and symphysis, and extends the length of the body’s trunk.The linea alba is a white, fibrous band that is made of the bilateral rectus sheaths that join at the anterior midline of the body. These enclose the rectus abdominis muscles. Each muscle is segmented by three transverse bands of collagen fibers called the tendinous intersections. This results in the look of “six-pack abs,” as each segment hypertrophies on individuals at the gym who do many sit-ups.
• See Figure 7.22 for an illustration of the major abdominal muscles.

Figure 7.22 Abdominal Muscles (a) anterior b) posterior (Source:https://openstax.org/books/anatomy-and-physiology-2e/pages/11-4-axial-muscles-of-the-abdominal-wall-and-thorax#fig-ch11_04_01)^[13]

See Table 7.B in the “Chapter Resources” section for a description of the movements by the abdominal muscles.

Table 7.B Movements of the Abdominal Muscles^[14]

Major Muscles of the Chest (Thorax)

The muscles of the chest serve to facilitate breathing by changing the size of the thoracic cavity. When you inhale, your chest rises because the cavity expands. Alternately, when you exhale, your chest falls because the thoracic cavity decreases in size.

Diaphragm

The change in volume of the thoracic cavity during breathing is due to the contraction and relaxation of the diaphragm. See Figure 7.23 for an illustration of the diaphragm muscle. The diaphragm separates the thoracic and abdominal cavities, and is dome-shaped at rest. The diaphragm also has three openings for structures between the chest cavity and the abdomen. The inferior vena cava passes through the caval opening, and the esophagus and attached nerves pass through the esophageal hiatus. The aorta passes through the aortic hiatus of the posterior diaphragm. See Figure 7.24 for an illustration of these openings in the diaphragm.

Figure 7.23 Diaphragm (https://commons.wikimedia.org/wiki/File:Human_diaphragm.png)

 

Figure 7.24 Openings in the Diaphragm (Source: https://openstax.org/books/anatomy-and-physiology-2e/pages/11-4-axial-muscles-of-the-abdominal-wall-and-thorax#fig-ch11_04_02)

 

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Intercostal Muscles

There are two primary sets of muscles called intercostal muscles, which are found in the intercostal spaces or spaces between the ribs (cost/o=rib). The main role of the intercostal muscles is to assist breathing by changing the dimensions of the rib cage. See Figure 7.25 for an illustration of the intercostal muscles.

Figure 7.25 Intercostal Muscles (Source: https://openstax.org/books/anatomy-and-physiology-2e/pages/11-4-axial-muscles-of-the-abdominal-wall-and-thorax#fig-ch11_04_03)

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See Table 7.C in the “Chapter Resources” section for a description of the movements by the thoracic muscles.

Table 7.C Movements of the Thoracic Muscles

Major Muscles of the Shoulder and Upper Limbs

Muscles of the shoulder and upper limb can be divided into four groups: muscles that stabilize and position the pectoral girdle, muscles that move the arm, muscles that move the forearm, and muscles that move the wrists, hands, and fingers.

The pectoral girdle, or shoulder girdle, consists of the lateral ends of the clavicle and scapula, along with the proximal end of the humerus, and the muscles covering these three bones to stabilize the shoulder joint. The girdle creates a base from which the head of the humerus, in its ball-and-socket joint, can move the arm in multiple directions.

Major Muscles of the Pectoral (Shoulder) Girdle

• Pectoralis minor: Rotates shoulder anteriorly (throwing motion)
• Serratus anterior: Moves arm from side of body to front of body
• Trapezius: Elevates shoulders (shrugging); pulls shoulder blades together; tilts head backwards. The trapezius stabilizes the upper part of the back.
• Rhomboid major: Attaches the vertebral border of the scapula to the spinous process of the thoracic vertebrae. It stabilizes the scapula during pectoral girdle movement.
• Rhomboid minor: Attaches the vertebral border of the scapula to the spinous process of the thoracic vertebrae. It stabilizes the scapula during pectoral girdle movement

See Figure 7.26 for an illustration of the pectoral girdle muscles.

Figure 7.26 Pectoral Girdle Muscles (https://openstax.org/books/anatomy-and-physiology-2e/pages/11-5-muscles-of-the-pectoral-girdle-and-upper-limbs)

 

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See Table 7.D in the “Chapter Resources” section for a description of the movements by the muscles that position the pectoral girdle.

Table 7.D Muscles that Position the Pectoral Girdle

Muscles That Move the Humerus

Similar to the muscles that position the pectoral girdle, muscles that cross the shoulder joint and move the humerus bone of the arm include both axial and scapular muscles The two axial muscles are the pectoralis major and the latissimus dorsi. The rest of the shoulder muscles originate on the scapula.

• Pectoralis major: The pectoralis major is thick and fan-shaped, covering much of the superior portion of the anterior thorax. It flexes the arm at the shoulder, adducts and medially rotates the arm.
• Latissimus dorsi: The broad, triangular latissimus dorsi is located on the inferior part of the back, where it inserts into a thick connective tissue sheath called an aponeurosis. It extends arm at the shoulder, adducts and medially rotates the arm.

• Deltoid: The deltoid is the thick muscle that creates the rounded lines of the shoulder and is the major abductor of the arm, but it also facilitates flexing and medial rotation, as well as extension and lateral rotation.
• Subscapularis: The subscapularis originates on the anterior scapula and medially rotates the arm.
• Supraspinatus: The supraspinatus is superior to the spine of the scapula and abducts the arm.
• Infraspinatus: The infraspinatus is inferior to the spine of the scapula and laterally rotates the arm.
• Teres major: The thick and flat teres major is inferior to the teres minor and extends the arm and assists in adduction and medial rotation of it.
• Teres minor: The teres minor laterally rotates, adducts, and extends the arm.

See Figure 7.27 for an illustration of muscles that move the humerus.

Figure 7.27 Muscles That Move the Humerus (Source: https://openstax.org/books/anatomy-and-physiology-2e/pages/11-5-muscles-of-the-pectoral-girdle-and-upper-limbs)

 

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Rotator Cuff

The tendons of the deep subscapularis, supraspinatus, infraspinatus, and teres minor connect the scapula to the humerus, forming the rotator cuff (musculotendinous cuff), the circle of tendons around the shoulder joint. When baseball pitchers undergo shoulder surgery, it is usually on the rotator cuff, which becomes pinched and inflamed and may tear away from the bone due to the repetitive motion of bringing the arm overhead to throw a fast pitch.

See Table 7.E in the “Chapter Resources” section for a description of the movements by the axial and scapular muscles.

Table 7.E Movements of the Axial and Scapular Muscles

 

Major Muscles That Move the Forearm

The forearm, made of the radius and ulna bones, has four main types of action at the elbow joint: flexion, extension, pronation, and supination. The major muscles here include:

• Biceps brachii: The two-headed biceps brachii crosses the shoulder and elbow joints to flex the forearm, also taking part in supinating the forearm at the radioulnar joints and flexing the arm at the elbow joint. It performs a biceps curl and also allows the palm of the hand to point toward the body while flexing.
• Brachialis: Deep to the biceps brachii, the brachialis provides additional power in flexing the forearm at the elbow.
• Brachioradialis: The brachioradialis can flex the forearm quickly or help lift a load slowly. When bending the elbow (flexing)—the brachioradialis assists the brachialis. Brachioradialis also supinates and pronates the forearm.
• Triceps brachii: The three-headed triceps brachii muscle extends the arm at both the elbow and shoulder joints. Part of it also helps adduct the arm.

See Figure 7.28 for an illustration of muscles that move the forearm.

Figure 7.28 Muscles That Move the Forearm (Source: https://openstax.org/books/anatomy-and-physiology-2e/pages/11-5-muscles-of-the-pectoral-girdle-and-upper-limbs)

 

See Table 7.F in the “Chapter Resources” section for a description of the movements of the muscles that move the forearm.

Table 7.F Movements of the Forearm Muscles

 

See Table 7.G in the “Chapter Resources” section for a description of the movements by the muscles that move the wrist, hands, and forearm.

Table 7.G  Movements of the Muscles that Move the Wrist, Hands, and Forearm

 

See Table 7.H in the “Chapter Resources” section for a description of the movements by the hand muscles.

Table 7.H Movements of the Muscles of the Hand

Muscles of the Pelvis and Lower Limbs

The appendicular muscles of the lower body position and stabilize the pelvic or hip girdle, which serves as a foundation for the lower limbs. The pelvic girdle has less range of motion because it stabilizes and supports the body. The body’s center of gravity is in the area of the pelvis. If the center of gravity were not to remain fixed, standing up would be difficult. Therefore, what the leg muscles lack in range of motion and versatility, they make up for in size and power, facilitating the body’s stabilization, posture, and movement.

Major Muscles of the Upper Leg (Thigh)

Most muscles that insert on and move the femur originate on the pelvic girdle. The muscles found in the hip and thigh include the following:

• Iliopsoas: Muscle group consisting of the iliacus and psoas major muscles, flexes the thigh at the hip, rotates it laterally, and flexes the trunk of the body onto the hip when sitting up from a supine position.
• Gluteus maximus: The largest of the gluteus muscles that extends the femur and laterally rotates the thigh.
• Gluteus medius: The muscle deep to the gluteus maximus that abducts the femur at the hip and medially rotates the thigh.
• Gluteus minimus: Smallest of the gluteal muscles and deep to the gluteus medius. It abducts the hip and medially rotates the thigh.
• Gracilis: The gracilis muscle adducts the thigh in addition to flexing the leg at the knee.
• Quadriceps femoris group: A group of muscles often referred to as the “quads,” it consists of four muscles that extend and stabilize the knee. They move the lower leg out in front of the body, as when kicking. The tendon common to all four is the quadriceps tendon (patellar tendon), which inserts into the proximal part of the patella and continues at the distal area as the patellar ligament. The patellar ligament attaches to the tibial tuberosity.
  • Rectus femoris: The rectus femoris is on the anterior aspect of the thigh.
  • Vastus lateralis: Found on the lateral aspect of the thigh.
  • Vastus medialis: Located on the medial aspect of the thigh.
  • Vastus intermedius: Found between vastus lateralis and vastus medialis and deep to the rectus femoris.
• Sartorius: A band-like muscle that extends from the anterior superior iliac spine of the pelvis to the medial side of the proximal tibia. This versatile muscle flexes the leg at the knee and flexes, abducts, and laterally rotates the leg at the hip. This muscle allows us to sit cross-legged.
• Hamstring group: Group of three muscles that flex the knee, extend the hip and rotate the thigh. The tendons of these muscles form the popliteal fossa, the diamond-shaped space at the back of the knee. You can feel the hamstring tendons behind your knee. The three hamstring muscles include:
  • Biceps femoris: Muscle located on the lateral side of the posterior thigh.
  • Semitendinosus: Muscle located medially next to the biceps femoris.
  • Semimembranosus: Most medial muscle of the three from mid thigh to medial knee. Part of it is deep to semitendinosus.

See Figure 7.29 for an illustration of the hip and thigh muscles.

Figure 7.29 Hip and Thigh Muscles

 

A:”1122_Gluteal_Muscles_that_Move_the_Femur” by OpenStax is licensed under CC BY 4.0

See Table 7.I in the “Chapter Resources” section for a description of the movements by the gluteal muscles that move the femur.

Table I. Movements of the Gluteal Muscles That Move the Femur

See Table 7.J in the “Chapter Resources” section for a description of the movements by the thigh muscles that move the femur, tibia, and fibula.

Table 7.J Movements of the Thigh Muscles That Move the Femur, Tibia, and Fibula

 

Major Muscles of the Lower Leg

The lateral and medial muscles of the lower leg invert, evert, and rotate the foot and include:

• Tibialis anterior: A long and thick muscle on the anterolateral surface of the tibia. It dorsiflexes and inverts the foot.
• Calcaneal tendon: The calcaneal tendon, also referred to as the Achilles tendon, is a strong tendon that inserts on the calcaneal bone.
• Gastrocnemius: The most superficial and visible muscle of the calf is the gastrocnemius. It plantar flexes the foot and assists in flexing the knee.
• Soleus: Deep to the gastrocnemius is the wide, flat soleus. This muscle also plantar flexes the foot

See Figure 7.30 for an illustration of muscles of the lower leg.

Figure 7.30 Muscles of the Lower Leg (Source: https://openstax.org/books/anatomy-and-physiology-2e/pages/11-6-appendicular-muscles-of-the-pelvic-girdle-and-lower-limbs)

 

A:”1123_Muscles_of_the_Leg_that_Move_the_Foot_and_Toes” by OpenStax is licensed under CC BY 4.0

See Figure 7.31 for an illustration of the gastrocnemius and soleus.

Figure 7.31 Gastrocnemius and Soleus (https://commons.wikimedia.org/wiki/File:Lower_leg_muscles.svg)

 

 

See Table 7.K in the “Chapter Resources” section for a description of the movements by the muscles that move the feet and toes.

Table 7.K Movement of the Muscles That Move the Feet and Toes