Arches of the foot
The arches of the foot, formed by the tarsal and metatarsal bones, strengthened by ligaments and tendons, allow the foot to support the weight of the body in the erect posture with the least weight. They are categorized as transverse arches; the longitudinal arches of the foot can be divided into lateral arches. The medial arch is higher than the lateral longitudinal arch, it is made up by the calcaneus, the talus, the navicular, the three cuneiforms, the first and third metatarsals. Its summit is at the superior articular surface of the talus, its two extremities or piers, on which it rests in standing, are the tuberosity on the plantar surface of the calcaneus posteriorly and the heads of the first and third metatarsal bones anteriorly; the chief characteristic of this arch is its elasticity, due to its height and to the number of small joints between its component parts. Its weakest part is the joint between the talus and navicular, but this portion is braced by the plantar calcaneonavicular ligament a.k.a. spring ligament, elastic and is thus able to restore the arch to its original condition when the disturbing force is removed.
The ligament is strengthened medially by blending with the deltoid ligament of the ankle joint, is supported inferiorly by the tendon of the Tibialis posterior, spread out in a fanshaped insertion and prevents undue tension of the ligament or such an amount of stretching as would permanently elongate it. The arch is further supported by the plantar aponeurosis, by the small muscles in the sole of the foot, by the tendons of the Tibialis anterior and posterior and Peronæus longus, flexor digitorum longus, flexor hallucis longus and by the ligaments of all the articulations involved; the lateral arch is composed of the calcaneus, the cuboid, the fourth and fifth metatarsals. Two notable features of this arch are its solidity and its slight elevation. Two strong ligaments, the long plantar and the plantar calcaneocuboid, together with the Extensor tendons and the short muscles of the little toe, preserve its integrity. While these medial and lateral arches may be demonstrated as the component antero-posterior arches of the foot, the fundamental longitudinal arch is contributed to by both, consists of the calcaneus, third cuneiform, third metatarsal: all the other bones of the foot may be removed without destroying this arch.
In addition to the longitudinal arches the foot presents a series of transverse arches. At the posterior part of the metatarsus and the anterior part of the tarsus the arches are complete, but in the middle of the tarsus they present more the characters of half-domes, the concavities of which are directed downward and medialward, so that when the medial borders of the feet are placed in apposition a complete tarsal dome is formed; the transverse arch is composed of the three cuneiforms, the cuboid, the five metatarsal bases. The transverse arch is strengthened by the interosseous and dorsal ligaments, by the short muscles of the first and fifth toes, by the Peronæus longus, whose tendon stretches across between the piers of the arches; the medial longitudinal arch in particular creates a space for soft tissues with elastic properties, which act as springs the thick plantar aponeurosis, passing from the heel to the toes. Because of their elastic properties, these soft tissues can spread ground contact reaction forces over a longer time period, thus reduce the risk of musculoskeletal wear or damage, they can store the energy of these forces, returning it at the next step and thus reducing the cost of walking and running, where vertical forces are higher.
The anatomy and shape of a person’s longitudinal and transverse arch can dictate the types of injuries to which that person is susceptible. The height of a person’s arch is determined by the height of the navicular bone. Collapse of the longitudinal arches results in. A person with a low longitudinal arch, or flat feet will stand and walk with their feet in a pronated position, where the foot everts or rolls inward; this makes the person susceptible to arch pain and plantar fasciitis. Flat footed people may have more difficulty performing exercises that require supporting their weight on their toes. People who have high longitudinal arches or a cavus foot tend to walk and stand with their feet in a supinated position where the foot inverts or rolls outward. High arches can cause plantar fasciitis as they cause the plantar fascia to be stretched away from the calcaneus or heel bone. Additionally, high or low arches can increase the risk of shin splints as the anterior tibialis must work harder to keep the foot from slapping the ground.
The non-human apes tend to walk on the lateral side of the foot, with an'inverted' foot, which may reflect a basic adaptation to walking on branches. It is held that their feet lack longitudinal arches, but footprints made by bipedally walking apes, which must directly or indirectly reflect the pressure they exert to support and propel themselves do suggest that they exert lower foot pressure under the medial part of their midfoot. However, human feet, the human medial longitudinal arch, differ in that the anterior part of the foot is medially twisted on the posterior part of the foot, so that all the toes may contact the ground at the same time, the twisting is so marked that the most medial toe, the big toe or hallux, tends
In vertebrate anatomy, hip refers to either an anatomical region or a joint. The hip region is located lateral and anterior to the gluteal region, inferior to the iliac crest, overlying the greater trochanter of the femur, or "thigh bone". In adults, three of the bones of the pelvis have fused into the hip bone or acetabulum which forms part of the hip region; the hip joint, scientifically referred to as the acetabulofemoral joint, is the joint between the femur and acetabulum of the pelvis and its primary function is to support the weight of the body in both static and dynamic postures. The hip joints have important roles in retaining balance, for maintaining the pelvic inclination angle. Pain of the hip may be the result of numerous causes, including nervous, infectious, trauma-related, genetic; the proximal femur is covered by muscles and, as a consequence, the greater trochanter is the only palpable bony structure in the hip region. The hip joint is a synovial joint formed by the articulation of the rounded head of the femur and the cup-like acetabulum of the pelvis.
It forms the primary connection between the bones of the lower limb and the axial skeleton of the trunk and pelvis. Both joint surfaces are covered with a strong but lubricated layer called articular hyaline cartilage; the cuplike acetabulum forms at the union of three pelvic bones — the ilium and ischium. The Y-shaped growth plate that separates them, the triradiate cartilage, is fused definitively at ages 14–16, it is a special type of spheroidal or ball and socket joint where the spherical femoral head is contained within the acetabulum and has an average radius of curvature of 2.5 cm. The acetabulum grasps half the femoral ball, a grip augmented by a ring-shaped fibrocartilaginous lip, the acetabular labrum, which extends the joint beyond the equator; the joint space between the femoral head and the superior acetabulum is between 2 and 7 mm. The head of the femur is attached to the shaft by a thin neck region, prone to fracture in the elderly, due to the degenerative effects of osteoporosis.
The acetabulum is oriented inferiorly and anteriorly, while the femoral neck is directed superiorly and anteriorly. The transverse angle of the acetabular inlet can be determined by measuring the angle between a line passing from the superior to the inferior acetabular rim and the horizontal plane; the sagittal angle of the acetabular inlet is an angle between a line passing from the anterior to the posterior acetabular rim and the sagittal plane. It measures 7° at birth and increases to 17° in adults. Wiberg's centre-edge angle is an angle between a vertical line and a line from the centre of the femoral head to the most lateral part of the acetabulum, as seen on an anteroposterior radiograph; the vertical-centre-anterior margin angle is an angle formed from a vertical line and a line from the centre of the femoral head and the anterior edge of the dense shadow of the subchondral bone posterior to the anterior edge of the acetabulum, with the radiograph being taken from the false angle, that is, a lateral view rotated 25 degrees towards becoming frontal.
The articular cartilage angle is an angle formed parallel to the weight bearing dome, that is, the acetabular sourcil or "roof", the horizontal plane, or a line connecting the corner of the triangular cartilage and the lateral acetabular rim. In normal hips in children aged between 11 and 24 months, it has been estimated to be on average 20°, ranging between 18° to 25°, it becomes progressively lower with age. Suggested cutoff values to classify the angle as abnormally increased include:30° up to 4 months of age. 25° up to 2 years of age. The angle between the longitudinal axes of the femoral neck and shaft, called the caput-collum-diaphyseal angle or CCD angle measures 150° in newborn and 126° in adults. An abnormally small angle is known as an abnormally large angle as coxa valga; because changes in shape of the femur affects the knee, coxa valga is combined with genu varum, while coxa vara leads to genu valgum. Changes in CCD angle is the result of changes in the stress patterns applied to the hip joint.
Such changes, caused for example by a dislocation, changes the trabecular patterns inside the bones. Two continuous trabecular systems emerging on auricular surface of the sacroiliac joint meander and criss-cross each other down through the hip bone, the femoral head and shaft. In the hip bone, one system arises on the upper part of auricular surface to converge onto the posterior surface of the greater sciatic notch, from where its trabeculae are reflected to the inferior part of the acetabulum; the other system emerges on the lower part of the auricular surface, converges at the level of the superior gluteal line, is reflected laterally onto the upper part of the acetabulum. In the femur, the first system lines up with a system arising from the lateral part of the femoral shaft to stretch to the inferior portion of the femoral neck and head; the other system lines up with a system in the femur stretching from the medial part of the femoral shaft to the superior part of the femoral head. On the lateral side of the hip joint the fascia lata is strengthened to
A joint or articulation is the connection made between bones in the body which link the skeletal system into a functional whole. They are constructed to allow for different types of movement; some joints, such as the knee and shoulder, are self-lubricating frictionless, are able to withstand compression and maintain heavy loads while still executing smooth and precise movements. Other joints such as sutures between the bones of the skull permit little movement in order to protect the brain and the sense organs; the connection between a tooth and the jawbone is called a joint, is described as a fibrous joint known as a gomphosis. Joints are classified both functionally. Joints are classified structurally and functionally. Structural classification is determined by how the bones connect to each other, while functional classification is determined by the degree of movement between the articulating bones. In practice, there is significant overlap between the two types of classifications. Monoarticular – concerning one joint oligoarticular or pauciarticular – concerning 2–4 joints polyarticular – concerning 5 or more joints Structural classification names and divides joints according to the type of binding tissue that connects the bones to each other.
There are four structural classifications of joints: fibrous joint – joined by dense regular connective tissue, rich in collagen fibers cartilaginous joint – joined by cartilage. There are two types: primary cartilaginous joints composed of hyaline cartilage, secondary cartilaginous joints composed of hyaline cartilage covering the articular surfaces of the involved bones with fibrocartilage connecting them. Synovial joint – not directly joined – the bones have a synovial cavity and are united by the dense irregular connective tissue that forms the articular capsule, associated with accessory ligaments. Facet joint – joint between two articular processes between two vertebrae. Joints can be classified functionally according to the type and degree of movement they allow: Joint movements are described with reference to the basic anatomical planes. Synarthrosis – permits little or no mobility. Most synarthrosis joints are fibrous joints. Amphiarthrosis – permits slight mobility. Most amphiarthrosis joints are cartilaginous joints.
Synovial joint – movable. Synovial joints can in turn be classified into six groups according to the type of movement they allow: plane joint and socket joint, hinge joint, pivot joint, condyloid joint and saddle joint. Joints can be classified, according to the number of axes of movement they allow, into nonaxial, monoaxial and multiaxial. Another classification is according to the degrees of freedom allowed, distinguished between joints with one, two or three degrees of freedom. A further classification is according to the number and shapes of the articular surfaces: flat and convex surfaces. Types of articular surfaces include trochlear surfaces. Joints can be classified based on their anatomy or on their biomechanical properties. According to the anatomic classification, joints are subdivided into simple and compound, depending on the number of bones involved, into complex and combination joints: Simple joint: two articulation surfaces Compound joint: three or more articulation surfaces Complex joint: two or more articulation surfaces and an articular disc or meniscus The joints may be classified anatomically into the following groups: Joints of hand Elbow joints Wrist joints Axillary articulations Sternoclavicular joints Vertebral articulations Temporomandibular joints Sacroiliac joints Hip joints Knee joints Articulations of footUnmyelinated nerve fibers are abundant in joint capsules and ligaments as well as in the outer part of intraarticular menisci.
These nerve fibers are responsible for pain perception. Damaging the cartilage of joints or the bones and muscles that stabilize the joints can lead to joint dislocations and osteoarthritis. Swimming is a great way to exercise the joints with minimal damage. A joint disorder is termed arthropathy, when involving inflammation of one or more joints the disorder is called arthritis. Most joint disorders involve arthritis, but joint damage by external physical trauma is not termed arthritis. Arthropathies are called polyarticular when involving many joints and monoarticular when involving only a single joint. Arthritis is the leading cause of disability in people over the age of 55. There are many different forms of arthritis; the most common form of arthritis, occurs following trauma to the joint, following an infection of the joint or as a result of aging and the deterioration of articular cartilage. Furthermore, there is emerging evidence that abnormal anatomy may contribute to early development of osteoarthritis.
Other forms of arthritis are rheumatoid arthritis and psoriatic arthritis, which are autoimmune diseases in which the body is attacking itself. Septic arthritis is caused by joint infection. Gouty arthritis is caused by deposition of uric acid crystals in the joint that results in subsequent inflammation. Additionally, there is a less common form of gout, caused by the formation of rhomboidal-shaped crystals of calcium pyrophosphate; this form of gout is known as pseudogout. Temporomandibular joint syndrome involves the jaw joints and can cause facial p
Ileret is a village in Marsabit County, Kenya. It is located in Northern Kenya, on the eastern shore of Lake Turkana, north of Sibiloi National Park and near the Ethiopian border. Numerous hominin fossils have been found near Ileret, including Homo erectus footprints dating back to about 1.5 million years ago, making them the second oldest hominin footprints found after those at Laetoli, Tanzania. Besides the Homo erectus footprints, numerous other fossils have been found near the Ileret site. In 2012-2013, a team of researchers from Stony Brook University found new hominin fossils near Ileret, in two sites within the Kolom Odiet area; the fossils were representative of three different individuals, composing of two partial skeletons - KNM-ER 64061 and KNM-ER 64062 - and an entirely completed mandible, KNM-ER 64060. KNM-ER 64060 and KNM-ER 64061 date back to 2.02 to 2.03 Ma, KNM-ER 64062 goes back 1.82 to 1.86 million years ago. The KNM-ER 64060 mandible is only missing the right central incisor.
The KNM-ER 64061 partial skeleton includes most of both humeral shafts, a partial right ulna and right clavicle, a right shoulder blade. Its longer bones appeared to be thick in its cross-sections; the KNM-ER 64062 skeleton possesses parts of a distal right humerus and scaphoid, parts of a right foot with both primitive and derived features. These three individuals most represent members of early Homo, the mandible being from Homo habilis and the partial skeletons being from Homo erectus. Fossilized footprints of Homo erectus were found in Kenya. Science reported that there were multiple trails of footprints found at the Ileret site: “two trails of two prints each, one of seven prints and a number of isolated prints.” These footprints reveal that these early hominins most traveled in groups—evidence which researchers see as a sign of social behavior. Certain social behaviors distinguish humans from other primate species. Researchers attempt to find evidence of similar behaviors in the fossil or footprint records, however, it is difficult because this kind of fossil evidence is lacking.
Homo erectus fossils were discovered in 1.5 million-year-old layers of sediment. These fossils supplied information about foot structure. Unlike the fossils, the footprints provide researchers with information about early foot anatomy. Moreover, other Homo erectus fossils have been found in nearby areas and are the the same age as the footprints found at Ileret. Differences have been found between common apes. According to Rutgers University, “the big toe is parallel to the other toes, unlike that of apes where it is separated in a grasping configuration useful in the trees.” The arch of the footprint is human-like and the toes are much shorter than those of an ape. Short toes are a sign of “upright bipedal stance.” Additionally, relevant observations point to similarities between modern humans. The footprints reveal comparable body weights and gaits; these early hominins are the first to have such similar body proportions to modern humans. Bipedalism is a characteristic of modern humans. Fossil evidence reveals.
It can be difficult to reconstruct gait evolution due to the inadequacy and scarcity of the fossil record. Fragments of bones are discovered and offer little information about hominins’ walking manners. Additionally, the hominin fossil record does not provide information concerning the social patterns of modern humans and other primates—patterns which drove evolution; the Ileret footprints provide significant evidence. The footprints provide evidence for a “modern human-like weight transfer” and support earlier discussions of Homo erectus’ arched foot. In 2007, the first of these footprints were discovered by Dr. JW Harris, Dr. BG Richmond, Dr. DR Braun. David R. Braun is an archaeologist working in both Eastern Africa. With an interest in stone tools, he directs the Koobi Fora Field School, he works at the Department of Anthropology at The George Washington University in Washington, D. C. Jack Harris is a professor in the Department of Anthropology at Rutgers University in New Jersey. Harris focuses on the continent of Africa and has spent time as research associate at the National Museums of Kenya.
He has begun work with some of the world’s distinguished primatologists. Human timeline Koobi Fora, a fossil site and field research camp Laetoli Footprints Human Timeline – Smithsonian, National Museum of Natural History
In human anatomy, the thigh is the area between the hip and the knee. Anatomically, it is part of the lower limb; the single bone in the thigh is called the femur. This bone is thick and strong, forms a ball and socket joint at the hip, a modified hinge joint at the knee; the femur is the only bone in the thigh and serves for an attachment site for all muscles in the thigh. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with the tibia and kneecap forming the knee. By most measures the femur is the strongest bone in the body; the femur is the longest bone in the body. The femur is categorised as a long bone and comprises a diaphysis, the shaft and two epiphysis or extremities that articulate with adjacent bones in the hip and knee. In cross-section, the thigh is divided up into three separate compartments, divided by fascia, each containing muscles; these compartments use the femur as an axis, are separated by tough connective tissue membranes.
Each of these compartments has its own blood and nerve supply, contains a different group of muscles. Medial fascial compartment of thigh, adductor Posterior fascial compartment of thigh, hamstring Anterior fascial compartment of thigh, extensionAnterior compartment muscles of the thigh include sartorius, the four muscles that comprise the quadriceps muscles- rectus femoris, vastus medialis, vastus intermedius and vastus lateralis. Posterior compartment muscles of the thigh are the hamstring muscles, which include semimembranosus and biceps femoris. Medial compartment muscles are pectineus, adductor magnus, adductor longus and adductor brevis, gracilis; because the major muscles of the thigh are the largest muscles of the body, resistance exercises of them stimulate blood flow more than any other localized activity. The arterial supply is by the obturator artery; the lymphatic drainage follows the arterial supply and drains to the lumbar lymphatic trunks on the corresponding side, which in turn drains to the cisterna chyli.
The deep venous system of the thigh consists of the femoral vein, the proximal part of the popliteal vein, various smaller vessels. The venae perfortantes connect the deep and the superficial system, which consists of the saphenous veins. Thigh weakness can result in a positive Gowers' sign on physical examination; the thigh meat of some animals such as chicken and cow is consumed as a food in many parts of the world
The skull is a bony structure that forms the head in vertebrates. It provides a protective cavity for the brain; the skull is composed of two parts: the mandible. In the human, these two parts are the neurocranium and the viscerocranium or facial skeleton that includes the mandible as its largest bone; the skull forms the anterior most portion of the skeleton and is a product of cephalisation—housing the brain, several sensory structures such as the eyes, ears and mouth. In humans these sensory structures are part of the facial skeleton. Functions of the skull include protection of the brain, fixing the distance between the eyes to allow stereoscopic vision, fixing the position of the ears to enable sound localisation of the direction and distance of sounds. In some animals such as horned ungulates, the skull has a defensive function by providing the mount for the horns; the English word "skull" is derived from Old Norse "skulle", while the Latin word cranium comes from the Greek root κρανίον.
The skull is made up of a number of fused flat bones, contains many foramina, fossae and several cavities or sinuses. In zoology there are openings in the skull called fenestrae. For details and the constituent bones, see Neurocranium and Facial skeleton The human skull is the bony structure that forms the head in the human skeleton, it forms a cavity for the brain. Like the skulls of other vertebrates, it protects the brain from injury; the skull consists of two parts, of different embryological origin—the neurocranium and the facial skeleton. The neurocranium forms the protective cranial cavity that surrounds and houses the brain and brainstem; the upper areas of the cranial bones form the calvaria. The membranous viscerocranium includes the mandible; the facial skeleton is formed by the bones supporting the face Except for the mandible, all of the bones of the skull are joined together by sutures—synarthrodial joints formed by bony ossification, with Sharpey's fibres permitting some flexibility.
Sometimes there can be extra bone pieces within the suture known as sutural bones. Most these are found in the course of the lambdoid suture; the human skull is considered to consist of twenty-two bones—eight cranial bones and fourteen facial skeleton bones. In the neurocranium these are the occipital bone, two temporal bones, two parietal bones, the sphenoid and frontal bones; the bones of the facial skeleton are the vomer, two inferior nasal conchae, two nasal bones, two maxilla, the mandible, two palatine bones, two zygomatic bones, two lacrimal bones. Some sources count the maxilla as having two bones; some of these bones—the occipital, frontal, in the neurocranium, the nasal and vomer, in the facial skeleton are flat bones. The skull contains sinuses, air-filled cavities known as paranasal sinuses, numerous foramina; the sinuses are lined with respiratory epithelium. Their known functions are the lessening of the weight of the skull, the aiding of resonance to the voice and the warming and moistening of the air drawn into the nasal cavity.
The foramina are openings in the skull. The largest of these is the foramen magnum that allows the passage of the spinal cord as well as nerves and blood vessels; the many processes of the skull include the zygomatic processes. The skull is a complex structure; the skull roof bones, comprising the bones of the facial skeleton and the sides and roof of the neurocranium, are dermal bones formed by intramembranous ossification, though the temporal bones are formed by endochondral ossification. The endocranium, the bones supporting the brain are formed by endochondral ossification, thus frontal and parietal bones are purely membranous. The geometry of the skull base and its fossae, the anterior and posterior cranial fossae changes rapidly; the anterior cranial fossa changes during the first trimester of pregnancy and skull defects can develop during this time. At birth, the human skull is made up of 44 separate bony elements. During development, many of these bony elements fuse together into solid bone.
The bones of the roof of the skull are separated by regions of dense connective tissue called fontanelles. There are six fontanelles: one anterior, one posterior, two sphenoid, two mastoid. At birth these regions are fibrous and moveable, necessary for birth and growth; this growth can put a large amount of tension on the "obstetrical hinge", where the squamous and lateral parts of the occipital bone meet. A possible complication of this tension is rupture of the great cerebral vein; as growth and ossification progress, the connective tissue of the fontanelles is invaded and replaced by bone creating sutures. The five sutures are the two squamous sutures, one coronal, one lambdoid, one sagittal suture; the posterior fontanelle closes by eight weeks, but the anterior fontanel can remain open up to eighteen months. The anterior fontanelle is located at the junction of the parietal bones. Careful observation will show that you can count a baby's heart
Anatomical terms of motion
Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints and specific sections of the body; the terminology used describes this motion according to its direction relative to the anatomical position of the joints. Anatomists use a unified set of terms to describe most of the movements, although other, more specialized terms are necessary for describing the uniqueness of the movements such as those of the hands and eyes. In general, motion is classified according to the anatomical plane. Flexion and extension are examples of angular motions, in which two axes of a joint are brought closer together or moved further apart. Rotational motion may occur at other joints, for example the shoulder, are described as internal or external. Other terms, such as elevation and depression, describe movement above or below the horizontal plane. Many anatomical terms derive from Latin terms with the same meaning. Motions are classified after the anatomical planes they occur in, although movement is more than not a combination of different motions occurring in several planes.
Motions can be split into categories relating to the nature of the joints involved: Gliding motions occur between flat surfaces, such as in the intervertebral discs or between the carpal and metacarpal bones of the hand. Angular motions occur over synovial joints and causes them to either increase or decrease angles between bones. Rotational motions move a structure in a rotational motion along a longitudinal axis, such as turning the head to look to either side. Apart from this motions can be divided into: Linear motions, which move in a line between two points. Rectilinear motion is motion in a straight line between two points, whereas curvilinear motion is motion following a curved path. Angular motions occur when an object is around another object decreasing the angle; the different parts of the object do not move the same distance. Examples include a movement of the knee, where the lower leg changes angle compared to the femur, or movements of the ankle; the study of movement is known as kinesiology.
A categoric list of movements of the human body and the muscles involved can be found at list of movements of the human body. The prefix hyper- is sometimes added to describe movement beyond the normal limits, such as in hypermobility, hyperflexion or hyperextension; the range of motion describes the total range of motion. For example, if a part of the body such as a joint is overstretched or "bent backwards" because of exaggerated extension motion it can be described as hyperextended. Hyperextension increases the stress on the ligaments of a joint, is not always because of a voluntary movement, it may be other causes of trauma. It may be used in surgery, such as in temporarily dislocating joints for surgical procedures; these are general terms. Most terms have a clear opposite, so are treated in pairs. Flexion and extension describe movements; these terms come from the Latin words with the same meaning. Flexion describes a bending movement that decreases the angle between a segment and its proximal segment.
For example, bending the elbow, or clenching a hand into a fist, are examples of flexion. When sitting down, the knees are flexed; when a joint can move forward and backward, such as the neck and trunk, flexion refers to movement in the anterior direction. When the chin is against the chest, the head is flexed, the trunk is flexed when a person leans forward. Flexion of the shoulder or hip refers to movement of the leg forward. Extension is the opposite of flexion, describing a straightening movement that increases the angle between body parts. For example, when standing up, the knees are extended; when a joint can move forward and backward, such as the neck and trunk, extension refers to movement in the posterior direction. Extension of the hip or shoulder moves the leg backward. Abduction is the motion of a structure away from the midline while adduction refer to motion towards the center of the body; the centre of the body is defined as the midsagittal plane. These terms come from Latin words with similar meanings, ab- being the Latin prefix indicating "away," ad- indicating "toward," and ducere meaning "to draw or pull".
Abduction refers to a motion that pulls a part away from the midline of the body. In the case of fingers and toes, it refers to spreading the digits apart, away from the centerline of the hand or foot. Abduction of the wrist is called radial deviation. For example, raising the arms up, such as when tightrope-walking, is an example of abduction at the shoulder; when the legs are splayed at the hip, such as when doing a star jump or doing a split, the legs are abducted at the hip. Adduction refers to a motion that pulls a structure or part toward the midline of the body, or towards the midline of a limb. In the case of fingers and toes, it refers to bringing the digits together, towards the centerline of the hand or foot. Adduction of the wrist is called ulnar deviation. Dropping the arms to the sides, bringing the knees together, are examples of adduction. Ulnar deviation is the hand moving towards the ulnar styloid. Radial deviation is the hand moving towards the radial styloid; the terms elevation and depression refer to movement below the horizontal.
They derive from the Latin terms with similar meaningsElevation refers to movement in a superior direction. For example