The triceps surae consists of two

muscle Muscle is a soft tissue, one of the four basic types of animal tissue. There are three types of muscle tissue in vertebrates: skeletal muscle, cardiac muscle, and smooth muscle. Muscle tissue gives skeletal muscles the ability to muscle contra ...

s located at the calf – the two-headed

gastrocnemius The gastrocnemius muscle (plural ''gastrocnemii'') is a superficial two-headed muscle that is in the back part of the lower leg of humans. It is located superficial to the soleus in the posterior (back) compartment of the leg. It runs from its t ...

and the

soleus In humans and some other mammals, the soleus is a powerful muscle in the back part of the lower leg (the calf). It runs from just below the knee to the heel and is involved in standing and walking. It is closely connected to the gastrocnemius mus ...

. These muscles both insert into the

calcaneus In humans and many other primates, the calcaneus (; from the Latin ''calcaneus'' or ''calcaneum'', meaning heel; : calcanei or calcanea) or heel bone is a bone of the Tarsus (skeleton), tarsus of the foot which constitutes the heel. In some other ...

, the bone of the heel of the human

foot The foot (: feet) is an anatomical structure found in many vertebrates. It is the terminal portion of a limb which bears weight and allows locomotion. In many animals with feet, the foot is an organ at the terminal part of the leg made up o ...

, and form the major part of the muscle of the posterior leg, commonly known as the calf muscle.

Structure

The triceps surae is connected to the foot through the

Achilles tendon The Achilles tendon or heel cord, also known as the calcaneal tendon, is a tendon at the back of the lower leg, and is the thickest in the human body. It serves to attach the plantaris, gastrocnemius (calf) and soleus muscles to the calcane ...

, and has three heads deriving from the two major masses of muscle. * The superficial portion (the gastrocnemius) gives off two heads attaching to the base of the

femur The femur (; : femurs or femora ), or thigh bone is the only long bone, bone in the thigh — the region of the lower limb between the hip and the knee. In many quadrupeds, four-legged animals the femur is the upper bone of the hindleg. The Femo ...

directly above the

knee In humans and other primates, the knee joins the thigh with the leg and consists of two joints: one between the femur and tibia (tibiofemoral joint), and one between the femur and patella (patellofemoral joint). It is the largest joint in the hu ...

. * The deep (profundus) mass of muscle (the soleus) forms the remaining head which attaches to the superior posterior area of the tibia. The triceps surae is innervated by the

tibial nerve The tibial nerve is a branch of the sciatic nerve. The tibial nerve passes through the popliteal fossa to pass below the arch of soleus. Structure Popliteal fossa The tibial nerve is the larger terminal branch of the sciatic nerve with root val ...

, specifically, nerve roots L5–S2.

Function

Contraction of the triceps surae induce plantar flexion (sagittal plane) and stabilization of the ankle complex in the

transverse plane A transverse plane is a plane that is rotated 90° from two other planes. Anatomy The transverse plane is an anatomical plane that is perpendicular to the sagittal plane and the dorsal plane. It is also called the axial plane or horizonta ...

. Functional activities include primarily movement in the

sagittal plane The sagittal plane (; also known as the longitudinal plane) is an anatomical plane that divides the body into right and left sections. It is perpendicular to the transverse and coronal planes. The plane may be in the center of the body and divi ...

, stabilization during locomotion (walking, running), restraining the body from falling and power

jumping Jumping or leaping is a form of locomotion or movement in which an organism or non-living (e.g., robotic) mechanical system propels itself through the air along a ballistic trajectory. Jumping can be distinguished from running, galloping and ...

. By controlling the disequilibrium torque, the triceps surae can affect force through the exchange of potential into

kinetic energy In physics, the kinetic energy of an object is the form of energy that it possesses due to its motion. In classical mechanics, the kinetic energy of a non-rotating object of mass ''m'' traveling at a speed ''v'' is \fracmv^2.Resnick, Rober ...

Clinical significance

Calf strain (torn calf muscle)

A calf strain refers to damage to a muscle or its attaching tendons. A premature return before recovery is achieved will result in a prolonged recovery or incomplete return to baseline prior to injury. Stretches such as alternating calf raises can improve

flexibility Stiffness is the extent to which an object resists deformation in response to an applied force. The complementary concept is flexibility or pliability: the more flexible an object is, the less stiff it is. Calculations The stiffness, k, of a ...

as well as mobilize legs before running. Calf muscles are a common place for

fasciculation A fasciculation, or muscle twitch, is a spontaneous, involuntary muscle contraction and relaxation, involving fine muscle fibers. They are common, with as many as 70% of people experiencing them. They can be benign, or associated with more seriou ...

Additional images

File:Triceps surae - animation.gif, Animation. Gastrocnemius and soleus are shown in different colors. File:Sobo 1909 303.png, Illustration of the

. File:Sobo 1909 304.png, Illustration of

. File:Sobo 1909 579-580.png, Nerves, arteries and veins surround the gastrocnemius and soleus. File:Braus 1921 293.png, Cross section of the lower leg, with triceps surae at back (soleus and gastrocnemius) File:Sobo_1909_720.png, Nerves and blood-vessels overlying the triceps surae File:Medial view of a cadaver dissection of the gastrocnemius–soleus junction - with text.png, Photograph of the

junction.

Etymology and pronunciation

The term is pronounced . It is from Latin ''caput'' and ''sura'' meaning "three-headed uscleof the calf".