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
Teres major muscle
The teres major muscle is a muscle of the upper limb. It is one of the seven scapulohumeral muscles, it is a somewhat flattened muscle. The teres major muscle is positioned above the latissimus dorsi muscle and assists in the extension and medial rotation of the humerus; this muscle is confused as a rotator cuff muscle, but it is not because it does not attach to the capsule of the shoulder joint, unlike the teres minor muscle for example. The teres major muscle originates on the dorsal surface of the inferior angle and the lower part of the lateral border of the scapula; the fibers of teres major insert into the medial lip of the intertubercular sulcus of the humerus. It is supplied by the lower subscapular nerve and additionally by the thoracodorsal nerve; these are distal to the upper subscapular nerve. These three nerves branch off the posterior cord of the brachial plexus; the nerves that innervate teres major consist of fibers from spinal nerves C5-C8. The tendon, at its insertion, lies behind that of the latissimus dorsi, from which it is separated by a bursa, the two tendons being, united along their lower borders for a short distance.
The fibers of these two muscles run parallel to each other and both muscles insert at the crest of the lesser tubercle of the humerus. Together with teres minor muscle, teres major muscle forms the axillary space, through which several important arteries and veins pass; the teres major is a medial rotator and adductor of the humerus and assists the latissimus dorsi in drawing the raised humerus downwards and backwards. It helps stabilise the humeral head in the glenoid cavity. Isolated teres, they are exclusively encountered in professional and high-level recreational athletes— baseball pitchers in particular. These injuries can be debilitating, requiring lengthy rehabilitation periods and missed seasons of athletics. No clear indications for surgical treatment exist. Outcomes have been good after both nonoperative and operative treatment. Accessory muscles of the scapula This article incorporates text in the public domain from page 442 of the 20th edition of Gray's Anatomy Anatomy figure: 03:03-06 at Human Anatomy Online, SUNY Downstate Medical Center PTCentral
Palmar interossei muscles
In human anatomy, the palmar or volar interossei are three small, unipennate muscles in the hand that lie between the metacarpal bones and are attached to the index and little fingers. They are smaller than the dorsal interossei of the hand. All palmar interossei originate along the shaft of the metacarpal bone of the digit on which they act, they are inserted into the base of the proximal phalanx and the extensor expansion of the extensor digitorum of the same digit. The first palmar interosseous is located at the thumb's medial side. Passing between the first dorsal interosseous and the oblique head of adductor pollicis, it is inserted on the base of the thumb's proximal phalanx together with adductor pollicis; this muscle, the so-called pollical palmar interosseous muscle, is present in more than 80% of individuals and was first described by Henle 1858. Its presence has been verified by numerous anatomists since, but others have either failed to mention it or considered it part of either adductor pollicis or flexor pollicis brevis.
However, the deep head of the flexor pollicis brevis originates on the thumb's ulnar sesamoid bone and the oblique portion of the adductor pollicis on several carpal bones as well as the bases of the second and third metacarpal bones and not on the first metacarpal. The other three palmar interossei originate on the side of the metacarpal facing the hand's midline; the tendons of these three muscles pass posterior to the deep transverse ligament before being inserted onto the extensor expansion. All of the interosseous muscles of the hand are innervated by the deep branch of the ulnar nerve; the palmar interossei are supplied by the palmar metacarpal artery of the deep palmar arch. The palmar interosseous muscles adduct the fingers towards the middle finger; this is in contrast to the dorsal interossei. In addition they flex the finger at the metacarpo-phalangeal joint and extend the finger at the interphalangeal joint and thus assist the lumbricals; the palmar interossei, together with the dorsal interossei and the lumbricals, are active components of the finger's extensor mechanism.
Fibers from some of the interossei contribute directly to the extensor hoods that wrap around the proximal phalanges while other fibers may contribute to the central tendon and lateral bands of the mechanism. All three intrinsic groups of muscles pass palmar to the axis of the metacarpophalangeal joints and therefore contribute to flexion there. Extension at the interphalangeal joints cannot be produced by the extensor digitorum alone, but active contraction of one of the three aforementioned intrinsic groups will because of their direct contribution to the extensor mechanism; the pollical palmar interosseous is absent in non-human primates and is an autapomorphic muscle unique to the human thumb which evolved from the oblique portion of adductor pollicis. In African apes, adductor pollicis is notably well-developed, with an origin on the carpus and its ligaments, an insertion that has migrated distally, in some cases as far as the distal phalanx; the insertion of the PPIM into the extensor mechanism is to have evolved with tool usage in early hominids.
As comparative anatomy studies of the human PPIM suggest that the muscle is evolutionarily derived from the adductor pollicis, it has been proposed that PPIM should be designated by the name musculus adductor pollicis accessorius, which indicates that the muscle is most a de novo structure derived from the adductor pollicis. Interosseous muscles of the hand Dorsal interossei of the hand Interosseous muscles of the foot Dorsal interossei of the foot Plantar interossei muscles
The triceps triceps brachii, is a large muscle on the back of the upper limb of many vertebrates. It is the muscle principally responsible for extension of the elbow joint; the long head arises from the infraglenoid tubercle of the scapula. It extends distally anterior to the teres posterior to the teres major; the medial head arises proximally from the groove of the radial nerve. The medial head is covered by the lateral and long heads, is only visible distally on the humerus; the lateral head arises from the dorsal surface of the humerus and proximal to the groove of the radial nerve, from the greater tubercle down to the region of the lateral intermuscular septum. Each of the three fascicles has its own motorneuron subnucleus in the motor column in the spinal cord; the medial head is formed predominantly by small type I fibers and motor units, the lateral head of large type IIb fibers and motor units and the long head of a mixture of fiber types and motor units. It has been suggested that each fascicle "may be considered an independent muscle with specific functional roles."The fibers converge to a single tendon to insert onto the olecranon process of the ulna and to the posterior wall of the capsule of the elbow joint where bursae are found.
Parts of the common tendon radiates into the fascia of the forearm and can cover the anconeus muscle. All three heads of the triceps brachii are classically believed to be innervated by the radial nerve. However, a study conducted in 2004 determined that, in 20 cadaveric specimens and 15 surgical dissections on participants, the long head was innervated by a branch of the axillary nerve in all cases. A tendinous arch is the origin of the long head and the tendon of latissimus dorsi. In rare cases, the long head can originate from the lateral margin of the scapula and from the capsule of the shoulder joint; the triceps is an extensor muscle of the elbow joint and an antagonist of the biceps and brachialis muscles. It can fixate the elbow joint when the forearm and hand are used for fine movements, e.g. when writing. It has been suggested that the long head fascicle is employed when sustained force generation is demanded, or when there is a need for a synergistic control of the shoulder and elbow or both.
The lateral head is used for movements requiring occasional high-intensity force, while the medial fascicle enables more precise, low-force movements. With its origin on the scapula, the long head acts on the shoulder joint and is involved in retroversion and adduction of the arm, it helps stabilise the shoulder joint at the top of the humerus. The triceps can be worked through either isolation or compound elbow extension movements and can contract statically to keep the arm straightened against resistance. Isolation movements include cable push-downs, lying triceps extensions and arm extensions behind the back. Examples of compound elbow extension include pressing movements like the push up, bench press, close grip bench press, military press and dips. A closer grip targets the triceps more than wider grip movements. Static contraction movements include pullovers, straight-arm pulldowns and bent-over lateral raises, which are used to build the deltoids and latissimus dorsi. Ruptures of the triceps muscle are rare, only occur in anabolic steroid users.
The triceps reflex, elicited by hitting the triceps, is used to test the function of the nerves of the arm. This tests spinal nerves C6 and C7, predominately C7, it is sometimes called a three-headed muscle, because there are three bundles of muscles, each of different origins, joining together at the elbow. Though a named muscle, the triceps surae, is found on the lower leg, the triceps brachii is called the triceps; the plural form of triceps was tricipites, a form not in general use today. In the horse, 84%, 15%, 3% of the total triceps muscle weight correspond to the long and medial heads, respectively. Many mammals, such as dogs and pigs, have a fourth head, the accessory head, it lies between the medial heads. In humans, the anconeus is sometimes loosely called "the fourth head of the triceps brachii". Illustration: upper-body/triceps-brachii from The Department of Radiology at the University of Washington Anatomy photo:06:11-0100 at the SUNY Downstate Medical Center Photo at Ithaca College Muscles/TricepsBrachii at exrx.net
A tendon or sinew is a tough band of fibrous connective tissue that connects muscle to bone and is capable of withstanding tension. Tendons are similar to ligaments. Ligaments join one bone to bone, while tendons connect muscle to bone for a proper functioning of the body. Histologically, tendons consist of dense regular connective tissue fascicles encased in dense irregular connective tissue sheaths. Normal healthy tendons are composed of parallel arrays of collagen fibers packed together, they are anchored to bone by Sharpey's fibres. The dry mass of normal tendons, which makes up about 30% of their total mass, is composed of about 86% collagen, 2% elastin, 1–5% proteoglycans, 0.2% inorganic components such as copper and calcium. The collagen portion is made up of 97–98% type I collagen, with small amounts of other types of collagen; these include type II collagen in the cartilaginous zones, type III collagen in the reticulin fibres of the vascular walls, type IX collagen, type IV collagen in the basement membranes of the capillaries, type V collagen in the vascular walls, type X collagen in the mineralized fibrocartilage near the interface with the bone.
Collagen fibres coalesce into macroaggregates. After secretion from the cell, the cleaved by procollagen N- and C-proteinases, the tropocollagen molecules spontaneously assemble into insoluble fibrils. A collagen molecule is about 300 nm long and 1–2 nm wide, the diameter of the fibrils that are formed can range from 50–500 nm. In tendons, the fibrils assemble further to form fascicles, which are about 10 mm in length with a diameter of 50–300 μm, into a tendon fibre with a diameter of 100–500 μm. Fascicles are bound by the endotendineum, a delicate loose connective tissue containing thin collagen fibrils. and elastic fibres. Groups of fascicles are bounded by the epitenon. Filling the interstitia within the fascia where the tendon is located is the paratenon a fatty areolar tissue; the collagen in tendons are held together with proteoglycan components including decorin and, in compressed regions of tendon, which are capable of binding to the collagen fibrils at specific locations. The proteoglycans are interwoven with the collagen fibrils – their glycosaminoglycan side chains have multiple interactions with the surface of the fibrils – showing that the proteoglycans are important structurally in the interconnection of the fibrils.
The major GAG components of the tendon are dermatan sulfate and chondroitin sulfate, which associate with collagen and are involved in the fibril assembly process during tendon development. Dermatan sulfate is thought to be responsible for forming associations between fibrils, while chondroitin sulfate is thought to be more involved with occupying volume between the fibrils to keep them separated and help withstand deformation; the dermatan sulfate side chains of decorin aggregate in solution, this behavior can assist with the assembly of the collagen fibrils. When decorin molecules are bound to a collagen fibril, their dermatan sulfate chains may extend and associate with other dermatan sulfate chains on decorin, bound to separate fibrils, therefore creating interfibrillar bridges and causing parallel alignment of the fibrils; the tenocytes produce the collagen molecules, which aggregate end-to-end and side-to-side to produce collagen fibrils. Fibril bundles are organized to form fibres with the elongated tenocytes packed between them.
There is a three-dimensional network of cell processes associated with collagen in the tendon. The cells communicate with each other through gap junctions, this signalling gives them the ability to detect and respond to mechanical loading. Blood vessels may be visualized within the endotendon running parallel to collagen fibres, with occasional branching transverse anastomoses; the internal tendon bulk is thought to contain no nerve fibres, but the epitenon and paratenon contain nerve endings, while Golgi tendon organs are present at the junction between tendon and muscle. Tendon length varies from person to person. Tendon length is, in practice, the deciding factor regarding potential muscle size. For example, all other relevant biological factors being equal, a man with a shorter tendons and a longer biceps muscle will have greater potential for muscle mass than a man with a longer tendon and a shorter muscle. Successful bodybuilders will have shorter tendons. Conversely, in sports requiring athletes to excel in actions such as running or jumping, it is beneficial to have longer than average Achilles tendon and a shorter calf muscle.
Tendon length is determined by genetic predisposition, has not been shown to either increase or decrease in response to environment, unlike muscles, which can be shortened by trauma, use imbalances and a lack of recovery and stretching. Traditionally, tendons have been considered to be a mechanism by which muscles connect to bone as well as muscles itself, functioning to transmit forces; this connection allows tendons to passively modulate forces during locomotion, providing additional stability with no active work. However, over the past two decades, much research focused on the elastic properties of some tendons and their ability to function as springs. Not all tendons are required to perform the same functional role, with some predominantly positioning limbs, such as the fingers when writing and others acting as springs to make locomotion more efficient. Energy storing tendons can recover energy at high efficiency. For example, during a human stride, the Achilles tendon stretches as the ankle joint dorsiflexes.
During the last portion of the stride, as the foot plantar-flexes (pointing the
Superficial branch of ulnar nerve
The superficial branch of the ulnar nerve is a terminal branch of the ulnar nerve. It supplies the palmaris brevis and the skin on the ulnar side of the hand, divides into a common palmar digital nerve and a proper palmar digital nerve; the proper digital branches are distributed to the fingers in the same manner as those of the median nerve. This article incorporates text in the public domain from page 942 of the 20th edition of Gray's Anatomy lesson5nervesofhand at The Anatomy Lesson by Wesley Norman
Fascial compartments of arm
The fascial compartments of arm refers to the specific anatomical term of the compartments within the upper segment of the upper limb of the body. The upper limb is divided into the arm and the forearm; each of these segments is further divided into two compartments which are formed by deep fascia – tough connective tissue septa. Each compartment encloses specific nerves; the compartments of the arm are the anterior compartment of the arm and the posterior compartment of the arm, divided by the lateral and the medial intermuscular septa. The compartments of the forearm are the anterior compartment of the forearm and posterior compartment of the forearm The lateral intermuscular septum extends from the lower part of the crest of the greater tubercle of the humerus, along the lateral supracondylar ridge, to the lateral epicondyle, it is perforated by the radial profunda branch of the brachial artery. The medial intermuscular septum, is thicker than the lateral intermuscular septum, it extends from the lower part of the crest of the lesser tubercle of the humerus below the teres major, passes along the medial supracondylar ridge to the medial epicondyle.
It is perforated by the ulnar nerve, the superior ulnar collateral artery, the posterior branch of the inferior ulnar collateral artery. The anterior compartment of the arm is known as the flexor compartment of the arm as its main action is that of flexion; the anterior compartment is one of the two anatomic compartments of the upper arm, the other being the posterior compartment. The anterior compartment contains three muscles; these muscles are all innervated by the musculocutaneous nerve which arises from the fifth and seventh cervical spinal nerves. The blood supply is from the brachial artery; the posterior compartment of the arm is known as the "extensor compartment", as its main action is extension. The muscles of this compartment are the triceps brachii and anconeus muscle and these are innervated by the radial nerve, their blood supply is from the profunda brachii. The triceps brachii is a large muscle containing three heads a lateral and middle; the anconeus is a small muscle. Some embryologists consider it as the fourth head of the triceps brachia as the upper and lower limbs have similar embryological origins, the lower limb contains the quadriceps femoris muscle which has four heads, is the lower limb equivalent of the triceps.
Anterior compartment of the forearm Posterior compartment of the forearm Compartment syndrome Fascia Fascial compartments of leg lesson4nervesofant&postarm at The Anatomy Lesson by Wesley Norman elbow/muscles/muscles2 at the Dartmouth Medical School's Department of Anatomy Dissection at tufts.edu https://web.archive.org/web/20080103065905/http://anatomy.med.umich.edu/musculoskeletal_system/axilla_ans.html