Muscles (Let's talk muscles)

Number of Points of Origin

A small number of muscles are named after the number of points of attachment they have at their points of origin. These would be; The biceps brachii in your arm that has two points of origin. Brachii is Latin for branches your biceps muscle has two branches at its origin. The triceps brachii in your arm has three points of origin. And the quadriceps in your leg has four points of origin.

Origin and Insertion

An even smaller number of muscles are named after the parts of the body where they start and end -- their origin and insertion. The sternocleidomastoid muscle, for example, originates from both the sternum and clavicle (breastbone and collarbone) and inserts into the mastoid bone (just below the ear).

Mechanical Action of Extensors

Are the muscles that counter flexors. They increase the angle at a joint. The extensor pollicis longus, therefore, is the long muscle in the forearm that straightens out the thumb once it's been bent inward.

Mechanical Action of Levators

As is obvious from the word, are muscles that lift things up. The levator ani is the muscle that pulls the anus up at the end of the digestive tract. If that muscle starts to weaken, you can feel the anus starting to push out and down -- very uncomfortable.

Mechanical Action of Depressors

As would be expected, are the opposite of levators; they push or pull things downward. The depressor labii inferioris is the muscle located below (or inferior) to the lips that pulls the lower lip down. •Rotators, as the name implies, produce a circular movement around a joint -- the rotator cuff in the shoulder being the most obvious example.

Gluteus Brevis

Brevis identifies the shortest of a group. The adductor brevis runs across the thigh to assist in pulling the thigh in towards your body's midline as opposed to down the length of your inner thigh as do the adductor magnus and minimus. •In Latin, the word "latus" means "side." Thus latissimus identifies the largest muscle "in width" in a group. Latissimus dorsi is the name of the large muscles that run from under your arms, across your "sides," and then across the middle of your back. Bodybuilders refer to these as their "lats."

Face and Neck

Frontalis wrinkles your brow. Orbicularis oculi circles the eye. Muscles of facial expression: Levator labii superioris, which raises the lips from above. Zygomaticus minor and major that raises the lips from the side. Depressor anguli oris that pulls the lips down. Risoris that makes you smile. Mentalis that pulls the lip down with the chin.

Gluteus Longus

Longus, as you might suspect, refers to the longest of a group--as in the adductor longus, which is thinner than the adductor magnus and runs essentially parallel to it.

Gluteus Minimus

Minimus, not surprisingly, refers to the smallest of a group. Thus gluteus minimus identifies the smaller butt muscle located underneath its maximus big brother. •Longus, as you might suspect, refers to the longest of a group--as in the adductor longus, which is thinner than the adductor magnus and runs essentially parallel to it.

Mechanical Action of Adductors

Move the bones back towards the midline as we saw with both the adductor longus and the adductor brevis, which are located in the inner thigh and that we looked at previously. Tensor muscles make things rigid. The tensor fascia lata muscle in the leg tightens and gets rigid to support the knee.

Mechanical Action of Flexor

Muscles decrease the angle at a joint. The flexor pollicis longus is the muscle in the forearm that pulls on the thumb and bends or flexes it inward toward the palm. We already know that longus means it's the longest muscle in its group -- and, in fact, it runs the full length of the forearm from the elbow to the thumb. And "pollicis" is Latin for thumb. Thus, the name tells us that it's the long muscle that flexes the thumb.

Mechanical Action of Abductor

Muscles move bones away from a midline in the body. The term is used both generically to describe the action of any muscle that moves away from the midline (the gluteus medius, for example, is an abductor in that its action is to pull the thigh out from the midline) and as part of the formal name of a handful of muscles such as the abductor pollicis brevis, which pulls the thumb away from the palm.

Upper body anterior

Pectoralis major muscles originate in the sternum and clavicle. They attach under the arm and pull the arms up across the body and rotate them inward. These are your pecs. They are worked by butterflies and bench presses. The deltoid originates in the clavicle, with insertion in the arm below the shoulder. The deltoid elevates the arm when it contracts. Biceps brachii and brachialis work in tandem, attaching in the forearm, and lifting the forearm. Rectus abdominis is a paired muscle that runs down either side of the abdomen. It is supported by tendons that give the muscle the appearance of being segmented -- thus the six pack.

Thigh muscles

Sartorius, as discussed previously Adductor magnus and longus, which pull the legs together at the midline Rectus femoris, which helps you kick Vastus lateralis and vastus medialis, which along with the rectus femoris help extend the knee and form a cage around it.

Muscle shapes

Shape There are really only four shapes that you need to concern yourself with when it comes to naming muscles: trapezoids; ex. between shoulder blades (dimond shaped), deltoid (triangle shaped); shoulder, saw tooth (sarretted muscle); under armpit area, and flat muscles; (along either side of the neck.)

Mechanical Action of Sphincters

Sphincters close openings, as does the anal sphincter.

Neck muscles

Sternocleidomastoid muscles flex and rotate the head. Omohyoid muscles are used primarily in chewing and swallowing. Sternohyoid helps control the hyoid bone, which plays a key role in swallowing and speech. Thyroid cartilage.

Gluteus maximus

The largest muscle in a related group of muscles is often referred to as maximus or magnus. An example that you're familiar with is the gluteus maximus. Gluteus is Latin for your rear end -- or more politely, your buttock. Thus, gluteus maximus identifies the largest muscle in your butt--the one you feel when you squeeze the cheeks of your butt together. Another example is the adductor magnus, which is the large muscle running down the inner thigh that pulls the leg back in from the side. You can feel this muscle if you balance against a table, putting your hand against the inside of the opposite thigh and then resisting as that hand tries to push the leg out to the side

Mechanical Action of supinator (counter to pronator)

The musculus supinator, for example, is the muscle in your forearm that turns your palm back facing up after you've pronated it down. Supinator comes from the Latin word supinum, which means "lying on your back."

Muscles named by Function

The risorius is a facial muscle that is crucial for the expressions of smiling and laughter. Humans are the only animals that have a well developed risorius. Risorius comes from the Latin word "risus," which means "laugh." Masseter comes from the Greek word for "chew," and that's its function in the human jaw. The sartorius muscle (from the Latin word for "tailor") runs from the outer hip, across the thigh, and ends at the inner knee. This muscle pulls the leg up at the knee while simultaneously turning it inward. It is used to cross the legs in the manner of an old time tailor sitting on the floor and sewing hides together--hence the name. And finally, some muscles are named by where they are found in the body. The temporalis muscle is named after the temporal bone (your temple) on top of which it is located. Likewise, the zygomatic bone is your cheekbone, and the zygomaticus muscles are located over your cheekbone.

Back of body

The trapezius and latissimus dorsi, joined by a mass of tendons, pull across the back. Under the scapula are the Infraspinatus, teres minor, and teres major, which all serve to stabilize the shoulder blades so that the shoulders can move. Gluteus maximus and the gluteus minimus hidden underneath the maximus are primarily stabilizing muscles. They support the pelvis and the trunk where it sits on the femur (the thigh bone). These muscles are most noticeable when standing on one leg. Without special exercise--squats, lunges, and backward leg lifts--they tend to lose tone as we age. This is the saggy butt often associated with aging. Hamstrings: semitendinosus and biceps femoris (not to be confused with the biceps brachii in your arm) -- to flex the lower leg at the knee. (Semitendinosius comes from the Latin words for "half tightly stretched" and refers to normal tightness of the calf muscles.) Calf muscles: gastrocnemius, with its two heads -- medial and lateral. (Gastrocnemius comes from the Greek and Latin words for calf.)

Mechanical Action of Pronators

Turns limbs so that they face downwards or backwards. If you hold your arm out in front of you, palm up, it's the pronator teres muscle that allows you to turn the arm at the elbow so that the palm is now facing downwards. The Latin word "pronus" means "face down" -- as in lying prone. And "teres" is Latin for "rounded or cylindrical," which refers to the shape of the muscle.

Muscle sizes

When it comes to size, the key identifiers are maximus or magnus, minimus, longus, brevis, and latissimus.