Gait analysis is the systematic study of animal locomotion, more the study of human motion, using the eye and the brain of observers, augmented by instrumentation for measuring body movements, body mechanics, the activity of the muscles. Gait analysis is used to assess and treat individuals with conditions affecting their ability to walk, it is commonly used in sports biomechanics to help athletes run more efficiently and to identify posture-related or movement-related problems in people with injuries. The study encompasses quantification, as well as interpretation, i.e. drawing various conclusions about the animal from its gait pattern. The pioneers of scientific gait analysis were Aristotle in De Motu Animalium and much in 1680, Giovanni Alfonso Borelli called De Motu Animalium. In the 1890s, the German anatomist Christian Wilhelm Braune and Otto Fischer published a series of papers on the biomechanics of human gait under loaded and unloaded conditions. With the development of photography and cinematography, it became possible to capture image sequences that reveal details of human and animal locomotion that were not noticeable by watching the movement with the naked eye.
Eadweard Muybridge and Étienne-Jules Marey were pioneers of these developments in the early 1900s. For example, serial photography first revealed the detailed sequence of the horse "gallop", misrepresented in paintings made prior to this discovery. Although much early research was done using film cameras, the widespread application of gait analysis to humans with pathological conditions such as cerebral palsy, Parkinson's disease, neuromuscular disorders, began in the 1970s with the availability of video camera systems that could produce detailed studies of individual patients within realistic cost and time constraints; the development of treatment regimes involving orthopaedic surgery, based on gait analysis results, advanced in the 1980s. Many leading orthopaedic hospitals worldwide now have gait labs that are used to design treatment plans and for follow-up monitoring. Development of modern computer based systems occurred independently during the late 1970s and early 1980s in several hospital based research labs, some through collaborations with the aerospace industry.
Commercial development soon followed with the emergence of commercial television and infrared camera systems in the mid-1980s. A typical gait analysis laboratory has several cameras placed around a walkway or a treadmill, which are linked to a computer; the patient has markers located at various points of reference of the body, or groups of markers applied to half of the body segments. The patient walks down the catwalk or the treadmill and the computer calculates the trajectory of each marker in three dimensions. A model is applied to calculate the movement of the underlying bones; this gives a complete breakdown of the movement of each joint. One common method is to use Helen Hayes Hospital marker set, in which a total of 15 markers are attached on the lower body; the 15 marker motions are analyzed analytically, it provides angular motion of each joint. To calculate the kinetics of gait patterns, most labs have floor-mounted load transducers known as force platforms, which measure the ground reaction forces and moments, including the magnitude and location.
The spatial distribution of forces can be measured with pedobarography equipment. Adding this to the known dynamics of each body segment enables the solution of equations based on the Newton–Euler equations of motion permitting computations of the net forces and the net moments of force about each joint at every stage of the gait cycle; the computational method for this is known as inverse dynamics. This use of kinetics, does not result in information for individual muscles but muscle groups, such as the extensor or flexors of the limb. To detect the activity and contribution of individual muscles to movement, it is necessary to investigate the electrical activity of muscles. Many labs use surface electrodes attached to the skin to detect the electrical activity or electromyogram of muscles. In this way it is possible to investigate the activation times of muscles and, to some degree, the magnitude of their activation—thereby assessing their contribution to gait. Deviations from normal kinematic, kinetic or EMG patterns are used to diagnose specific pathologies, predict the outcome of treatments, or determine the effectiveness of training programs The gait analysis is modulated or modified by many factors, changes in the normal gait pattern can be transient or permanent.
The factors can be of various types: Extrinsic: such as terrain, clothing, cargo Intrinsic: sex, height, etc. Physical: such as weight, physique Psychological: personality type, emotions Physiological: anthropometric characteristics, i.e. measurements and proportions of body Pathological: for example trauma, neurological diseases, musculoskeletal anomalies, psychiatric disordersThe parameters taken into account for the gait analysis are as follows: Step length Stride length Cadence Speed Dynamic Base Progression Line Foot Angle Hip Angle Squat Performance Gait analysis involves measurement, where measurable parameters are introduced and analyzed, interpretation, where conclusions about the subject are drawn. The analysis is the measurement of the following: It consists of the calculation of speed, the length of the rhythm, so on; these me
A wheelchair is a chair with wheels, used when walking is difficult or impossible due to illness, injury, or disability. Wheelchairs come in a wide variety of formats to meet the specific needs of their users, they may include specialized seating adaptions, individualized controls, may be specific to particular activities, as seen with sports wheelchairs and beach wheelchairs. The most recognised distinction is between powered wheelchairs, where propulsion is provided by batteries and electric motors, manually propelled wheelchairs, where the propulsive force is provided either by the wheelchair user/occupant pushing the wheelchair by hand, or by an attendant pushing from the rear; the earliest records of wheeled furniture are an inscription found on a stone slate in China and a child's bed depicted in a frieze on a Greek vase, both dating between the 6th and 5th century BCE. The first records of wheeled seats being used for transporting disabled people date to three centuries in China. A distinction between the two functions was not made for another several hundred years, until around 525 CE, when images of wheeled chairs made to carry people begin to occur in Chinese art.
Although Europeans developed a similar design, this method of transportation did not exist until 1595 when an unknown inventor from Spain built one for King Phillip II. Although it was an elaborate chair having both armrests and leg rests, the design still had shortcomings since it did not feature an efficient propulsion mechanism and thus, requires assistance to propel it; this makes the design more of a modern-day highchair or portable throne for the wealthy rather than a modern-day wheelchair for the disabled. In 1655, Stephan Farffler, a 22-year-old paraplegic watchmaker, built the world's first self-propelling chair on a three-wheel chassis using a system of cranks and cogwheels. However, the device had an appearance of a hand bike more than a wheelchair since the design included hand cranks mounted at the front wheel; the invalid carriage or Bath chair brought the technology into more common use from around 1760. In 1887, wheelchairs were introduced to Atlantic City so invalid tourists could rent them to enjoy the Boardwalk.
Soon, many healthy tourists rented the decorated "rolling chairs" and servants to push them as a show of decadence and treatment they could never experience at home. In 1933 Harry C. Jennings, Sr. and his disabled friend Herbert Everest, both mechanical engineers, invented the first lightweight, folding, portable wheelchair. Everest had broken his back in a mining accident. Everest and Jennings saw the business potential of the invention and went on to become the first mass-market manufacturers of wheelchairs, their "X-brace" design is still albeit with updated materials and other improvements. The X-brace idea came to Harry from the men’s folding “camp chairs / stools”, rotated 90 degrees, that Harry and Herbert used in the outdoors and at the mines. There are a wide variety of types of wheelchair, differing by propulsion method, mechanisms of control, technology used; some wheelchairs are designed for general everyday use, others for single activities, or to address specific access needs. Innovation within the wheelchair industry is common, but many innovations fall by the wayside, either from over-specialization, or from failing to come to market at an accessible price-point.
The iBot is the best known example of this in recent years. A self-propelled manual wheelchair incorporates a frame, one or two footplates and four wheels: two caster wheels at the front and two large wheels at the back. There will also be a separate seat cushion; the larger rear wheels have push-rims of smaller diameter projecting just beyond the tyre. Manual wheelchairs have brakes that bear on the tyres of the rear wheels, however these are a parking brake and in-motion braking is provided by the user's palms bearing directly on the push-rims; as this causes friction and heat build-up on long downslopes, many wheelchair users will choose to wear padded wheelchair gloves. Manual wheelchairs have two push handles at the upper rear of the frame to allow for manual propulsion by a second person, however many active wheelchair users will remove these to prevent unwanted pushing from people who believe they are being helpful. Everyday manual wheelchairs come in two major varieties, folding or rigid.
Folding chairs are low-end designs, whose predominant advantage is being able to fold by bringing the two sides together. However this is an advantage for part-time users who may need to store the wheelchair more than use it. Rigid wheelchairs, which are preferred by full-time and active users, have permanently welded joints and many fewer moving parts; this reduces the energy required to push the chair by eliminating many points where the chair would flex and absorb energy as it moves. Welded rather than folding joints reduce the overall weight of the chair. Rigid chairs feature instant-release rear wheels and backrests that fold down flat, allowing the user to dismantle the chair for storage in a car. A few wheelchairs attempt to combine the features of both designs by providing a fold-to-rigid mechanism in which the joints are mechanically locked when the wheelchair is in use. Many rigid models are now made with ultralight materials such as aircraft-grade aluminium and titanium, wheelchairs of
The pelvis is either the lower part of the trunk of the human body between the abdomen and the thighs or the skeleton embedded in it. The pelvic region of the trunk includes the bony pelvis, the pelvic cavity, the pelvic floor, below the pelvic cavity, the perineum, below the pelvic floor; the pelvic skeleton is formed in the area of the back, by the sacrum and the coccyx and anteriorly and to the left and right sides, by a pair of hip bones. The two hip bones connect the spine with the lower limbs, they are attached to the sacrum posteriorly, connected to each other anteriorly, joined with the two femurs at the hip joints. The gap enclosed by the bony pelvis, called the pelvic cavity, is the section of the body underneath the abdomen and consists of the reproductive organs and the rectum, while the pelvic floor at the base of the cavity assists in supporting the organs of the abdomen. In mammals, the bony pelvis has a gap in the middle larger in females than in males, their young pass through this gap.
The pelvic region of the trunk is the lower part of the trunk, between the thighs. It includes several structures: the bony pelvis, the pelvic cavity, the pelvic floor, the perineum; the bony pelvis is the part of the skeleton embedded in the pelvic region of the trunk. It is subdivided into the pelvic spine; the pelvic girdle is composed of the appendicular hip bones oriented in a ring, connects the pelvic region of the spine to the lower limbs. The pelvic spine consists of the coccyx; the pelvic cavity defined as a small part of the space enclosed by the bony pelvis, delimited by the pelvic brim above and the pelvic floor below. Each hip bone consists of 3 sections, ilium and pubis. During childhood, these sections are separate bones, joined by the triradiate cartilage. During puberty, they fuse together to form a single bone; the pelvic cavity is a body cavity, bounded by the bones of the pelvis and which contains reproductive organs and the rectum. A distinction is made between the lesser or true pelvis inferior to the terminal line, the greater or false pelvis above it.
The pelvic inlet or superior pelvic aperture, which leads into the lesser pelvis, is bordered by the promontory, the arcuate line of ilium, the iliopubic eminence, the pecten of the pubis, the upper part of the pubic symphysis. The pelvic outlet or inferior pelvic aperture is the region between the subpubic angle or pubic arch, the ischial tuberosities and the coccyx. Ligaments: obturator membrane, inguinal ligament Alternatively, the pelvis is divided into three planes: the inlet and outlet; the pelvic floor has two inherently conflicting functions: One is to close the pelvic and abdominal cavities and bear the load of the visceral organs. To achieve both these tasks, the pelvic floor is composed of several overlapping sheets of muscles and connective tissues; the pelvic diaphragm is composed of the coccygeus muscle. These arise between the symphysis and the ischial spine and converge on the coccyx and the anococcygeal ligament which spans between the tip of the coccyx and the anal hiatus; this leaves a slit for the urogenital openings.
Because of the width of the genital aperture, wider in females, a second closing mechanism is required. The urogenital diaphragm consists of the deep transverse perineal which arises from the inferior ischial and pubic rami and extends to the urogential hiatus; the urogenital diaphragm is reinforced posteriorly by the superficial transverse perineal. The external anal and urethral sphincters close the urethra; the former is surrounded by the bulbospongiosus which narrows the vaginal introitus in females and surrounds the corpus spongiosum in males. Ischiocavernosus clitoridis. Modern humans are to a large extent characterized by large brains; because the pelvis is vital to both locomotion and childbirth, natural selection has been confronted by two conflicting demands: a wide birth canal and locomotion efficiency, a conflict referred to as the "obstetrical dilemma". The female pelvis, or gynecoid pelvis, has evolved to its maximum width for childbirth—a wider pelvis would make women unable to walk.
In contrast, human male pelvises are not constrained by the need to give birth and therefore are more optimized for bipedal locomotion. The principal differences between male and female true and false pelvis include: The female pelvis is larger and broader than the male pelvis, taller and more compact; the female inlet is oval in shape, while the male sacral promontory projects further. The sides of the male pelvis converge from the inlet to the outlet, whereas the sides of the female pelvis are wider apart; the angle between
Gait is the pattern of movement of the limbs of animals, including humans, during locomotion over a solid substrate. Most animals use a variety of gaits, selecting gait based on speed, the need to maneuver, energetic efficiency. Different animal species may use different gaits due to differences in anatomy that prevent use of certain gaits, or due to evolved innate preferences as a result of habitat differences. While various gaits are given specific names, the complexity of biological systems and interacting with the environment make these distinctions'fuzzy' at best. Gaits are classified according to footfall patterns, but recent studies prefer definitions based on mechanics; the term does not refer to limb-based propulsion through fluid mediums such as water or air, but rather to propulsion across a solid substrate by generating reactive forces against it. Due to the rapidity of animal movement, simple direct observation is sufficient to give any insight into the pattern of limb movement.
In spite of early attempts to classify gaits based on footprints or the sound of footfalls, it was not until Eadweard Muybridge and Étienne-Jules Marey began taking rapid series of photographs that proper scientific examination of gaits could begin. Milton Hildebrand pioneered the classification of gaits; the movement of each limb was partitioned into a stance phase, where the foot was in contact with the ground, a swing phase, where the foot was lifted and moved forwards. Each limb must complete a cycle in the same length of time, otherwise one limb's relationship to the others can change with time, a steady pattern cannot occur. Thus, any gait can be described in terms of the beginning and end of stance phase of three limbs relative to a cycle of a reference limb the left hindlimb. Gaits are classed as "symmetrical" and "asymmetrical" based on limb movement, it is important to note. In a symmetrical gait, the left and right limbs of a pair alternate, while in an asymmetrical gait, the limbs move together.
Asymmetrical gaits are sometimes termed "leaping gaits", due to the presence of a suspended phase. The key variables for gait are the forelimb-hindlimb phase relationship. Duty factor is the percent of the total cycle which a given foot is on the ground; this value will be the same for forelimbs and hindlimbs unless the animal is moving with a specially trained gait or is accelerating or decelerating. Duty factors over 50 % are considered a "walk". Forelimb-hindlimb phase is the temporal relationship between the limb pairs. If the same-side forelimbs and hindlimbs initiate stance phase at the same time, the phase is 0. If the same-side forelimb contacts the ground half of the cycle than the hindlimb, the phase is 50%. Gait choice can have effects beyond immediate changes in limb movement and speed, notably in terms of ventilation; because they lack a diaphragm and salamanders must expand and contract their body wall in order to force air in and out of their lungs, but these are the same muscles used to laterally undulate the body during locomotion.
Thus, they cannot move and breathe at the same time, a situation called Carrier's constraint, though some, such as monitor lizards, can circumvent this restriction via buccal pumping. In contrast, the spinal flexion of a galloping mammal causes the abdominal viscera to act as a piston and deflating the lungs as the animal's spine flexes and extends, increasing ventilation and allowing greater oxygen exchange. Any given animal uses a restricted set of gaits, different species use different gaits. All animals are capable of symmetrical gaits, while asymmetrical gaits are confined to mammals, who are capable of enough spinal flexion to increase stride length. Lateral sequence gaits during walking and running are most common in mammals, but arboreal mammals such as monkeys, some opossums, kinkajous use diagonal sequence walks for enhanced stability. Diagonal sequence walks and runs are most used by sprawling tetrapods such as salamanders and lizards, due to the lateral oscillations of their bodies during movement.
Bipeds are a unique case, most bipeds will display only three gaits - walking and hopping - during natural locomotion. Other gaits, such as human skipping, are not used without deliberate effort. While gaits can be classified by footfall, new work involving whole-body kinematics and force-plate records has given rise to an alternative classification scheme, based on the mechanics of the movement. In this scheme, movements are divided into running. Walking gaits are all characterized by a'vaulting' movement of the body over the legs described as an inverted pendulum. In running, the kinetic and potential energy fluctuate in-phase, the energy change is passed on to muscles, bones and ligaments acting as springs. Speed governs gait selection, with quadrupedal mammals moving from a walk to a run to a gallop as speed increases; each of these gaits has an optimum speed, at which the minimum calories per meter are consumed, costs increase at slower or faster speeds. Gait transitions occur near the speed where the cost of a fast walk becomes higher than the cost of a slow run.
Unrestrained animals will move at the optimum speed
A walker or walking frame is a tool for disabled or elderly people who need additional support to maintain balance or stability while walking. In the United Kingdom, a common equivalent term for a walker is Zimmer frame, a genericised trademark from Zimmer Holdings, a major manufacturer of such devices and joint replacement parts. Walkers started appearing in the early 1950s; the first US patent was awarded in 1953 to William Cribbes Robb, of Stretford, UK, for a device called "walking aid", filed with the British patent office in August 1949. Two variants with wheels were both awarded US patents in May 1957, the first non-wheeled design, called a "walker" was patented in 1965 by Elmer F. Ries of Cincinnati, Ohio; the first walker to resemble modern walkers was patented in 1970 by Alfred A. Smith of Van Nuys, California; the basic design consists of a lightweight frame, about waist high 12 inches deep and wider than the user. Walkers are available in other sizes such as pediatric or bariatric.
Modern walkers are height adjustable and should be set at a height, comfortable for the user, but will allow the user to maintain a slight bend in their arms. This bend is needed to allow for proper blood circulation through the arms; the front two legs of the walker may or may not have wheels attached, depending on the strength and abilities of the person using it. It is common to see caster wheels or glides on the back legs of a walker with wheels on the front; the person walks with the frame surrounding their front and sides and their hands provide additional support by holding on to the top of the sides of the frame. Traditionally, a walker is placed a short distance ahead of the user; the user walks to it and repeats the process. With the use of wheels and glides, the user may push the walker ahead as opposed to picking it up; this makes for easier use of the walker, as it does not require the user to use their arms to lift the walker. This is beneficial for those with little arm strength.
A walker is used by those who are recuperating from leg or back injuries. It is commonly used by persons having problems with walking or with mild balance problems. Related is a hemi-walker, a walker about half the size of a traditional walker, intended for use by persons whose dexterity is limited or non-existent in one hand or arm; these walkers are more stable than a quad cane, but are not recommended as as a traditional walker for those who can use it. A walker cane hybrid was introduced in 2012 designed to bridge the gap between an assistive cane and a walker; the hybrid has two legs. It can be used with two hands in front of the user, similar to a walker, provides an increased level of support compared with a cane, it can be adjusted for use with either one or two hands, at the front and at the side, as well as a stair climbing assistant. The hybrid is not designed to replace a walker which has four legs and provides four-way support using both hands. A different approach to the walker is the rollator called wheeled walker, invented by the Swedish Aina Wifalk in 1978, herself a polio sufferer.
Although a brand name, "rollator" has become a genericized trademark for wheeled walkers in many countries, is the most common type of walker in several European countries. The rollator consists of a frame with three or four large wheels, handlebars and a built-in seat, which allows the user to stop and rest when needed. Rollators are often equipped with a shopping basket. Rollators are more sophisticated than conventional walkers with wheels, they are light-weight, yet sturdier than conventional walkers. The handlebars are equipped with hand brakes that can be lifted or pushed downward to stop the rollator; the brakes can be used in maneuvering the rollator. A recent study has found an increase in the use of rollators by young people "usually in their thirties who are setting a new standard for walking among young people"; the researchers conclude that this might be helpful in alleviating the stigma that using a rollator carries. A recent Norwegian-made version of Wifalk's rollator won the Red Dot Design Award 2011 in the "Life science and medicine" class.
The European norm for walking aids EN ISO 11199-2:2005 applies to walking frames. This type of walker provides support and stability to the dogs, while allowing them to rely on their hind legs and continue using them, it is suitable for dogs with mobility problems with hind legs. It helps them to exercise their back legs and can help maintaining any partial mobility they may have left or, in some cases, help to improve it; the Zimmer Frame was invented by Norman Metcalfe. It was aimed to help the disabled walk easier, it is an improvement of the classic walking aids. The Zimmer Frames have two wheels in the front. Baby walker Assistive technology American Family Physician, August 15, 2011: Geriatric Assistive Devices Retrieved 2012-03-03 Mayo Clinic - Slide show: Tips for choosing and using walkers Retrieved 2012-03-03 Walker Facts - Canadian non-profit information website about walkers and rollators Retrieved 2012-03-03 Archives of Ph
A neuromuscular junction is a chemical synapse formed by the contact between a motor neuron and a muscle fiber. It is at the neuromuscular junction that a motor neuron is able to transmit a signal to the muscle fiber, causing muscle contraction. Muscles require innervation to function—and just to maintain muscle tone, avoiding atrophy. Synaptic transmission at the neuromuscular junction begins when an action potential reaches the presynaptic terminal of a motor neuron, which activates voltage-dependent calcium channels to allow calcium ions to enter the neuron. Calcium ions bind to sensor proteins on synaptic vesicles, triggering vesicle fusion with the cell membrane and subsequent neurotransmitter release from the motor neuron into the synaptic cleft. In vertebrates, motor neurons release acetylcholine, a small molecule neurotransmitter, which diffuses across the synaptic cleft and binds to nicotinic acetylcholine receptors on the cell membrane of the muscle fiber known as the sarcolemma. NAChRs are ionotropic receptors.
The binding of ACh to the receptor can depolarize the muscle fiber, causing a cascade that results in muscle contraction. Neuromuscular junction diseases can be of autoimmune origin. Genetic disorders, such as Duchenne muscular dystrophy, can arise from mutated structural proteins that comprise the neuromuscular junction, whereas autoimmune diseases, such as myasthenia gravis, occur when antibodies are produced against nicotinic acetylcholine receptors on the sarcolemma. At the neuromuscular junction presynaptic motor axons terminate 30 nanometers from the cell membrane or sarcolemma of a muscle fiber; the sarcolemma at the junction has invaginations called postjunctional folds, which increase its surface area facing the synaptic cleft. These postjunctional folds form the motor endplate, studded with nicotinic acetylcholine receptors at a density of 10,000 receptors/micrometer2; the presynaptic axons terminate in bulges called terminal boutons that project toward the postjunctional folds of the sarcolemma.
In the frog each motor nerve terminal contains about 300,000 vesicles, with an average diameter of 0.05 micrometers. The vesicles contain acetylcholine; some of these vesicles are gathered into groups of fifty, positioned at active zones close to the nerve membrane. Active zones are about 1 micrometer apart; the 30 nanometer cleft between nerve ending and endplate contains a meshwork of acetylcholinesterase at a density of 2,600 enzyme molecules/micrometer2, held in place by the structural proteins dystrophin and rapsyn. Present is the receptor tyrosine kinase protein MuSK, a signaling protein involved in the development of the neuromuscular junction, held in place by rapsyn. About once every second in a resting junction randomly one of the synaptic vesicles fuses with the presynaptic neuron's cell membrane in a process mediated by SNARE proteins. Fusion results in the emptying of the vesicle's contents of 7000-10,000 acetylcholine molecules into the synaptic cleft, a process known as exocytosis.
Exocytosis releases acetylcholine in packets that are called quanta. The acetylcholine quantum diffuses through the acetylcholinesterase meshwork, where the high local transmitter concentration occupies all of the binding sites on the enzyme in its path; the acetylcholine that reaches the endplate activates ~2,000 acetylcholine receptors, opening their ion channels which permits sodium ions to move into the endplate producing a depolarization of ~0.5 mV known as a miniature endplate potential. By the time the acetylcholine is released from the receptors the acetylcholinesterase has destroyed its bound ACh, which takes about ~0.16 ms, hence is available to destroy the ACh released from the receptors. When the motor nerve is stimulated there is a delay of only 0.5 to 0.8 msec between the arrival of the nerve impulse in the motor nerve terminals and the first response of the endplate The arrival of the motor nerve action potential at the presynaptic neuron terminal opens voltage-dependent calcium channels and Ca2+ ions flow from the extracellular fluid into the presynaptic neuron's cytosol.
This influx of Ca2+ causes several hundred neurotransmitter-containing vesicles to fuse with the presynaptic neuron's cell membrane through SNARE proteins to release their acetylcholine quanta by exocytosis. The endplate depolarization by the released acetylcholine is called an endplate potential; the EPP is accomplished when ACh binds the nicotinic acetylcholine receptors at the motor end plate, causes an influx of sodium ions. This influx of sodium ions generates the EPP, triggers an action potential which travels along the sarcolemma and into the muscle fiber via the transverse tubules by means of voltage-gated sodium channels; the conduction of action potentials along the transverse tubules stimulates the opening of voltage-gated Ca2+ channels which are mechanically coupled to Ca2+ release channels in the sarcoplasmic reticulum. The Ca2+ diffuses out of the sarcoplasmic reticulum to the myofibrils so it can stimulate contraction; the endplate potential is thus responsible for setting up an action potential in the muscle fiber which triggers muscle contraction.
The transmission from nerve to muscle is so rapid because each quantum of acetylcholine reaches the endplate in millimolar concentrations, high enough to combine with a receptor with a low affinity, which swiftly releases the bound transmitter. Acetylcholine is a neurotransmitter synthesized from dietary choline and acetyl-CoA, is involved in the stimulation of muscle tissue in vertebrates as well as i
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