The ischial tuberosity known informally as the sit bones, or as a pair the sitting bones is a large swelling posteriorly on the superior ramus of the ischium. It marks the lateral boundary of the pelvic outlet; when sitting, the weight is placed upon the ischial tuberosity. The gluteus maximus provides cover in the upright posture, but leaves it free in the seated position; the distance between a cyclist's ischial tuberosities is one of the factors in the choice of a bicycle saddle. The tuberosity is divided into two portions: a lower, somewhat triangular part, an upper, quadrilateral portion; the lower portion is subdivided by a prominent longitudinal ridge, passing from base to apex, into two parts: The outer gives attachment to the adductor magnus The inner to the sacrotuberous ligament The upper portion is subdivided into two areas by an oblique ridge, which runs downward and outward: From the upper and outer area the semimembranosus arises From the lower and inner, the long head of the biceps femoris and the semitendinosus Ischial bursitis Sitting disability This article incorporates text in the public domain from page 235 of the 20th edition of Gray's Anatomy Goossens R, Teeuw R, Snijders C.
"Sensitivity for pressure difference on the ischial tuberosity". Ergonomics. 48: 895–902. Doi:10.1080/00140130500123647. PMID 16076744. Platzer, Werner. Color Atlas of Human Anatomy, Vol. 1: Locomotor System. Thieme. ISBN 3-13-533305-1. Anatomy photo:41:st-0204 at the SUNY Downstate Medical Center - "The Female Perineum: Bones" Anatomy photo:17:os-0114 at the SUNY Downstate Medical Center - "Major Joints of the Lower Extremity: Hip bone" pelvis at The Anatomy Lesson by Wesley Norman
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
Adductor longus muscle
In the human body, the adductor longus is a skeletal muscle located in the thigh. One of the adductor muscles of the hip, its main function is to adduct the thigh and it is innervated by the obturator nerve, it forms the medial wall of the femoral triangle. The adductor longus arises from the superior ramus of the pubis, it lies ventrally on the adductor magnus, near the femur, the adductor brevis is interposed between these two muscles. Distally, the fibers of the adductor longus extend into the adductor canal, it is inserted into the middle third of the medial lip of the linea aspera. The adductor longus is in relation by its anterior surface with the pubic portion of the fascia lata, near its insertion with the femoral artery and vein. By its posterior surface with the adductor brevis and magnus, the anterior branches of the obturator artery and nerves, near its insertion with the profunda artery and vein. By its outer border with the pectineus, by the inner border with the gracilis, its main actions is to laterally rotate the thigh.
As part of the medial compartment of the thigh, the adductor longus is innervated by the anterior division of the obturator nerve. The obturator nerve exits via the anterior rami of the spinal cord from L2, L3, L4. Adductor longus is derived from the myotome of spinal roots L2, L3, L4. Cross section image: pembody/body18b—Plastination Laboratory at the Medical University of Vienna Cross section image: pelvis/pelvis-e12-15—Plastination Laboratory at the Medical University of Vienna PTCentral
External obturator muscle
The external obturator muscle, obturator externus muscle is a flat, triangular muscle, which covers the outer surface of the anterior wall of the pelvis. It is sometimes considered part of the medial compartment of thigh, sometimes considered part of the gluteal region, it arises from the margin of bone around the medial side of the obturator membrane and surrounding bone, viz. from the inferior pubic ramus, the ramus of the ischium. The fibers springing from the pubic arch extend on to the inner surface of the bone, where they obtain a narrow origin between the margin of the foramen and the attachment of the obturator membrane; the fibers converge and pass posterolateral and upward, end in a tendon which runs across the back of the neck of the femur and lower part of the capsule of the hip joint and is inserted into the trochanteric fossa of the femur. The obturator vessels lie between the obturator membrane. In 33 % of people a supernumerary muscle is found between the adductor minimus. While this muscle, when present, is similar to its neighbouring adductors, it is formed by separation from the superficial layer of the external obturator, is thus not ontogenetically related to the adductor muscles of the hip.
This muscle originates from the upper part of the inferior pubic ramus from where it runs downwards and laterally. In half of cases, it inserts into the anterior surface of the insertion aponeurosis of the adductor minimus. In the remaining cases, it is either inserted into the upper part of the pectineal line or the posterior part of the lesser trochanter, it has been demonstrated by the course of the posterior branch of obturator nerve that the obturator externus is divided into a superior muscle fascicle and a main belly. The supernumerary muscle described above originates from the superior fascicle, while an anomalous fascicle — derived from the external obturator — originates from the main belly; the "original" external obturator, i.e. without these supernumerary muscular parts occurs in only 20% of cases, the external obturator undergoes ontogenetic variations. The external obturator muscle acts as the lateral rotator of the hip joint; as a short muscle around the hip joint, it stabilizes the hip joint as a postural muscle.
This article incorporates text in the public domain from page 477 of the 20th edition of Gray's Anatomy Cross section image: pelvis/pelvis-e12-15—Plastination Laboratory at the Medical University of Vienna lljoints at The Anatomy Lesson by Wesley Norman PTCentral
Adductor minimus muscle
In human anatomy, the adductor minimus is a small and flat skeletal muscle in the thigh which constitutes the upper, lateral part of the adductor magnus muscle. The adductor minimus originates on the pelvis at the inferior ramus of the pubis as the anterior-most part of the adductor magnus, it is inserted on the back of the femur at the medial lip of the linea aspera and thus crosses the proximal part of the true adductor magnus. The adductor minimus and the adductor magnus are separated by a branch of the superior perforating branch of the profunda femoris artery and the former muscle is considered independent from the latter because it is a separate entity, it shares innervation with the adductor magnus. In 33 % of people a supernumerary muscle is found between the adductor minimus; when present, this muscle originates from the upper part of the inferior ramus of the pubis from where it runs downwards and laterally. In half of cases, it inserts into the anterior surface of the insertion aponeurosis of the adductor minimus.
In the remaining cases, it is either inserted into the upper part of the pectineal line or the posterior part of the lesser trochanter. While similar to its neighbouring adductors, it is formed by separation from the superficial layer of the obturator externus, is thus not ontogenetically related to the adductors, it adducts and laterally rotates the femur
Adductor magnus muscle
The adductor magnus is a large triangular muscle, situated on the medial side of the thigh. It consists of two parts; the portion which arises from the ischiopubic ramus is called the pubofemoral portion, adductor portion, or adductor minimus, the portion arising from the tuberosity of the ischium is called the ischiocondylar portion, extensor portion, or "hamstring portion". Due to its common embryonic origin and action the ischiocondylar portion is considered part of the hamstring group of muscles; the ischiocondylar portion of the adductor magnus is considered a muscle of the posterior compartment of the thigh while the pubofemoral portion of the adductor magnus is considered a muscle of the medial compartment. Those fibers which arise from the ramus of the pubis are short, horizontal in direction, are inserted into the rough line of the femur leading from the greater trochanter to the linea aspera, medial to the gluteus maximus; those fibers from the ramus of the ischium are directed downward and laterally with different degrees of obliquity, to be inserted, by means of a broad aponeurosis, into the linea aspera and the upper part of its medial prolongation below.
The medial portion of the muscle, composed principally of the fibers arising from the tuberosity of the ischium, forms a thick fleshy mass consisting of coarse bundles which descend vertically, end about the lower third of the thigh in a rounded tendon, inserted into the adductor tubercle on the medial condyle of the femur, is connected by a fibrous expansion to the line leading upward from the tubercle to the linea aspera. By its anterior surface the adductor magnus is in relation with the pectineus, adductor brevis, adductor longus, femoral artery and vein, profunda artery and vein, with their branches, with the posterior branches of the obturator artery, obturator vein and obturator nerve. By its posterior surface with the semitendinosus, semimembranosus and gluteus maximus muscle. By its inner border with the gracilis and sartorius. By its upper border with the obturator externus, quadratus femoris, it is a composite muscle as the adductor and hamstring portions of the muscle are innervated by two different nerves.
The adductor portion is innervated by the posterior division of the obturator nerve while the hamstring portion is innervated by the sciatic nerve. At the insertion of the muscle, there is a series of osseoaponeurotic openings, formed by tendinous arches attached to the bone; the upper four openings are small, give passage to the perforating branches of the profunda femoris artery. The lowest is large, transmits the femoral vessels to the popliteal fossa; the upper, lateral part of the adductor magnus is an incompletely separated division considered a separate muscle — the adductor minimus. These two muscles are separated by a branch of the superior perforating branch of the profunda femoris artery; the adductor magnus is a powerful adductor of the thigh, made active when the legs are moved from a wide spread position to one in which the legs parallel each other. The part attached to the linea aspera acts as a lateral rotator; the part which reaches the medial epicondyle acts as a medial rotator when the leg is rotated outwards and flexed, acts to extend the hip joint.
In other tetrapods, the adductor magnus crosses the knee joint and inserts into the tibia. In humans, the distal part of the tendon detaches and becomes the medial collateral ligament of the knee; because of this, the medial collateral ligament of the knee in humans may contain a few muscle fibres as an atavistic variation. Adductor hiatus This article incorporates text in the public domain from page 473 of the 20th edition of Gray's Anatomy Anatomy photo:14:st-0401 at the SUNY Downstate Medical Center PTCentral
Anatomical terms of muscle
Muscles are described using unique anatomical terminology according to their actions and structure. There are three types of muscle tissue in the human body: skeletal and cardiac. Skeletal striated muscle, or "voluntary muscle" joins to bone with tendons. Skeletal muscle maintains posture. Smooth muscle tissue is found in parts of the body; the majority of this type of muscle tissue is found in the digestive and urinary systems where it acts by propelling forward food and feces in the former and urine in the latter. Other places smooth muscle can be found are within the uterus, where it helps facilitate birth, the eye, where the pupillary sphincter controls pupil size. Cardiac muscle is specific to the heart, it is involuntary in its movement, is additionally self-excitatory, contracting without outside stimuli. As well as anatomical terms of motion, which describe the motion made by a muscle, unique terminology is used to describe the action of a set of muscles. Agonist muscles and antagonist muscles refer to muscles that inhibit a movement.
Agonist muscles cause a movement to occur through their own activation. For example, the triceps brachii contracts, producing a shortening contraction, during the up phase of a push-up. During the down phase of a push-up, the same triceps brachii controls elbow flexion while producing a lengthening contraction, it is still the agonist, because while resisting gravity during relaxing, the triceps brachii continues to be the prime mover, or controller, of the joint action. Agonists are interchangeably referred to as "prime movers," since they are the muscles considered responsible for generating or controlling a specific movement. Another example is the dumbbell curl at the elbow; the "elbow flexor" group is the agonist. During the lowering phase the "elbow flexor" muscles lengthen, remaining the agonists because they are controlling the load and the movement. For both the lifting and lowering phase, the "elbow extensor" muscles are the antagonists, they shorten during the dumbbell lowering phase.
Here it is important to understand that it is common practice to give a name to a muscle group based on the joint action they produce during a shortening contraction. However, this naming convention does not mean; this term describes the function of skeletal muscles. Antagonist muscles are the muscles that produce an opposing joint torque to the agonist muscles; this torque can aid in controlling a motion. The opposing torque can slow movement down - in the case of a ballistic movement. For example, during a rapid discrete movement of the elbow, such as throwing a dart, the triceps muscles will be activated briefly and to accelerate the extension movement at the elbow, followed immediately by a "burst" of activation to the elbow flexor muscles that decelerates the elbow movement to arrive at a quick stop. To use an automotive analogy, this would be similar to pressing your gas pedal and immediately pressing the brake. Antagonism is not an intrinsic property of a particular muscle group. During slower joint actions that involve gravity, just as with the agonist muscle, the antagonist muscle can shorten and lengthen.
Using the example above of the triceps brachii during a push-up, the elbow flexor muscles are the antagonists at the elbow during both the up phase and down phase of the movement. During the dumbbell curl, the elbow extensors are the antagonists for both the lifting and lowering phases. Antagonist and agonist muscles occur in pairs, called antagonistic pairs; as one muscle contracts, the other relaxes. An example of an antagonistic pair is the triceps. "Reverse motions" need antagonistic pairs located in opposite sides of a joint or bone, including abductor-adductor pairs and flexor-extensor pairs. These consist of an extensor muscle, which "opens" the joint and a flexor muscle, which does the opposite by decreasing the angle between two bones. However, muscles don't always work this way. Sometimes during a joint action controlled by an agonist muscle, the antagonist will be activated, naturally; this occurs and is not considered to be a problem unless it is excessive or uncontrolled and disturbs the control of the joint action.
This serves to mechanically stiffen the joint. Not all muscles are paired in this way. An example of an exception is the deltoid. Synergist muscles help perform, the same set of joint motion as the agonists. Synergists muscles act on movable joints. Synergists are sometimes referred to as "neutralizers" because they help cancel out, or neutralize, extra motion from the agonists to make sure that the force generated works within the desired plane of motion. Muscle fibers can only contract up to 40% of their stretched length, thus the short fibers of pennate muscles are more suitable where power rather than range of contraction is required. This limitation in the range of contraction affects all muscles, those that act over several joints may be unable to shorten sufficiently to produce