Third trochanter
Encyclopedia
In human anatomy, the third trochanter is a bony projection occasionally present on the proximal femur
near the superior border of the gluteal tuberosity
. When present, it is oblong, rounded, or conical in shape and sometimes continuous with the gluteal ridge. It generally occurs bilaterally without significant side to side dimorphism
.
A structure of minor importance in humans, the incidence of the third trochanter varies from 17–72% between ethnic groups and it is frequently reported as more common in females than in males. Structures analogous to the third trochanter are present in other mammals, including some primates.
It is called the third trochanter in reference to the greater
and lesser trochanter
s that are always present on the femur.
. It may function as (1) a reinforcement mechanism for the proximal femoral diaphysis
in response to increased ground reaction force and (2) to increase the attachment surface area for the gluteal musculature and thereby providing greater efficiency of contracture. Mechanical load from the gluteus maximus may, on the other hand, affect the morphology of the proximal femur, similar to how quadriceps
determines the size and shape of the tibial tuberosity, and thereby the shape of the third trochanter.
s (that were shorter and more robust than anatomically modern humans
) but generally absent in higher primates
.
Studying fossils of Ardipithecus ramidus (a Chimpanzee-human last common ancestor
candidate), noted that in this species — as well as in Proconsul, Nacholapithecus, and Dryopithecus
(Miocene
primates) — homologs
to the third trochanter and the hypotrochanteric fossa are present while both traits are absent in extant apes. They concluded that the hominid morphotype
is primitive and the femoral shape of apes is derived contrary to what was previously thought.
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
near the superior border of the gluteal tuberosity
Gluteal tuberosity
The lateral ridge of the linea aspera is very rough, and runs almost vertically upward to the base of the greater trochanter. It is termed the gluteal tuberosity, and gives attachment to part of the Glutæus maximus: its upper part is often elongated into a roughened crest, on which a more or less...
. When present, it is oblong, rounded, or conical in shape and sometimes continuous with the gluteal ridge. It generally occurs bilaterally without significant side to side dimorphism
Polymorphism (biology)
Polymorphism in biology occurs when two or more clearly different phenotypes exist in the same population of a species — in other words, the occurrence of more than one form or morph...
.
A structure of minor importance in humans, the incidence of the third trochanter varies from 17–72% between ethnic groups and it is frequently reported as more common in females than in males. Structures analogous to the third trochanter are present in other mammals, including some primates.
It is called the third trochanter in reference to the greater
Greater trochanter
The greater trochanter of the femur is a large, irregular, quadrilateral eminence and a part of the skeletal system.It is directed a little lateralward and backward, and, in the adult, is about 1 cm lower than the head...
and lesser trochanter
Lesser trochanter
The lesser trochanter of the femur is a conical eminence, which varies in size in different subjects-Anatomy:It projects from the lower and back part of the base of the femur neck.From its apex three well-marked borders extend:...
s that are always present on the femur.
Function
Its function is to provide an attachment for the ascending tendon of the gluteus maximus muscleGluteus maximus muscle
The gluteus maximus is the largest and most superficial of the three gluteal muscles...
. It may function as (1) a reinforcement mechanism for the proximal femoral diaphysis
Diaphysis
The diaphysis is the main or mid section of a long bone. It is made up of cortical bone and usually contains bone marrow and adipose tissue ....
in response to increased ground reaction force and (2) to increase the attachment surface area for the gluteal musculature and thereby providing greater efficiency of contracture. Mechanical load from the gluteus maximus may, on the other hand, affect the morphology of the proximal femur, similar to how quadriceps
Quadriceps muscle
The quadriceps femoris , also called simply the quadriceps, quadriceps extensor, quads, is a large muscle group that includes the four prevailing muscles on the front of the thigh...
determines the size and shape of the tibial tuberosity, and thereby the shape of the third trochanter.
Palaeontology
The third trochanter is associated with short, robust femora, and is frequently present and well developed in NeanderthalNeanderthal
The Neanderthal is an extinct member of the Homo genus known from Pleistocene specimens found in Europe and parts of western and central Asia...
s (that were shorter and more robust than anatomically modern humans
Anatomically modern humans
The term anatomically modern humans in paleoanthropology refers to early individuals of Homo sapiens with an appearance consistent with the range of phenotypes in modern humans....
) but generally absent in higher primates
Simian
The simians are the "higher primates" familiar to most people: the Old World monkeys and apes, including humans, , and the New World monkeys or platyrrhines. Simians tend to be larger than the "lower primates" or prosimians.- Classification and evolution :The simians are split into three groups...
.
Studying fossils of Ardipithecus ramidus (a Chimpanzee-human last common ancestor
Chimpanzee-human last common ancestor
The chimpanzee-human last common ancestor is the last species, a species of African apes, that humans, bonobos and chimpanzees share as a common ancestor....
candidate), noted that in this species — as well as in Proconsul, Nacholapithecus, and Dryopithecus
Dryopithecus
Dryopithecus was a genus of apes that is known from Eastern Africa into Eurasia during the late Miocene period. The first species of Dryopithecus was discovered at the site of Saint-Gaudens, Haute-Garonne, France, in 1856...
(Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
primates) — homologs
Homology (biology)
Homology forms the basis of organization for comparative biology. In 1843, Richard Owen defined homology as "the same organ in different animals under every variety of form and function". Organs as different as a bat's wing, a seal's flipper, a cat's paw and a human hand have a common underlying...
to the third trochanter and the hypotrochanteric fossa are present while both traits are absent in extant apes. They concluded that the hominid morphotype
Polymorphism (biology)
Polymorphism in biology occurs when two or more clearly different phenotypes exist in the same population of a species — in other words, the occurrence of more than one form or morph...
is primitive and the femoral shape of apes is derived contrary to what was previously thought.