Extensor indicis muscle
In human anatomy, the extensor indicis is a narrow, elongated skeletal muscle in the deep layer of the dorsal forearm, placed medial to, parallel with, the extensor pollicis longus. Its tendon goes to the index finger, it arises from the distal third of the dorsal part of the body of ulna and from the interosseous membrane. It runs through the fourth tendon compartment together with the extensor digitorum, from where it projects into the dorsal aponeurosis of the index finger. Opposite the head of the second metacarpal bone, it joins the ulnar side of the tendon of the extensor digitorum which belongs to the index finger. Like the extensor digiti minimi, the tendon of the extensor indicis runs and inserts on the ulnar side of the tendon of the common extensor digitorum; the extensor indicis lacks the juncturae tendinum interlinking the tendons of the extensor digitorum on the dorsal side of the hand. The extensor indicis, it exists as a single tendon most of the time. Double tendons of the extensor indicis proprius was reported.
It is known that the extensor indicis proprius inserts to the index finger on the ulnar side of the extensor digitorum. However, the insertion on the radial side of the common extensor digitorum infrequently seen, namely the extensor indicis radialis. Split tendons of the muscle inserting on both ulnar and the radial side of the common extensor digitorum was reported. Anomalous hand extensors including the extensor medii proprius and the extensor indicis et medii communis are seen as variations of the extensor indicis due to the shared characteristics and embryonic origin; the extensor indicis extends the index finger, by its continued action assists in extending the wrist and the midcarpal joints. Because the index finger and little finger have separate extensors, these fingers can be moved more independently than the other fingers. Extensor digitorum Extensor medii proprius Extensor indicis et medii communis This article incorporates text in the public domain from page 456 of the 20th edition of Gray's Anatomy Platzer, Werner.
Color Atlas of Human Anatomy, Vol. 1: Locomotor System. Thieme. ISBN 3-13-533305-1. Ross, Lawrence M.. Thieme Atlas of Anatomy: General Anatomy and Musculoskeletal System. Thieme. ISBN 978-1-58890-419-5. CS1 maint: Extra text: authors list Anatomy photo:09:05-0106 at the SUNY Downstate Medical Center - "Extensor Region of Forearm and Dorsum of Hand: Deep Muscles of Extensor Region" lesson5musofpostforearm at The Anatomy Lesson by Wesley Norman Extensor_indicis at the Duke University Health System's Orthopedics program Ritter, Merrill A.. "The Extensor Indicis Proprius Syndrome". J Bone Joint Surg Am. 51: 1645–1648. Doi:10.2106/00004623-196951080-00016
Common extensor tendon
The common extensor tendon is a tendon that attaches to the lateral epicondyle of the humerus. It serves as the upper attachment for the superficial muscles that are located on the posterior aspect of the forearm: Extensor carpi radialis brevis Extensor digitorum Extensor digiti minimi Extensor carpi ulnaris Common flexor tendon Tennis elbow
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The phalanges are digital bones in the hands and feet of most vertebrates. In primates, the thumbs and big toes have two phalanges; the phalanges are classed as long bones. The phalanges are the bones that make up the toes of the foot. There are 56 phalanges in the human body, with fourteen on each foot. Three phalanges are present on each finger and toe, with the exception of the thumb and large toe, which possess only two; the middle and far phalanges of the fourth and fifth toes are fused together. The phalanges of the hand are known as the finger bones; the phalanges of the foot differ from the hand in that they are shorter and more compressed in the proximal phalanges, those closest to the body. A phalanx is named according to whether it is proximal, middle, or distal and its associated finger or toe; the proximal phalanges are those that are closest to foot. In the hand, the prominent, knobby ends of the phalanges are known as knuckles; the proximal phalanges join with the metacarpals of the hand or metatarsals of the foot at the metacarpophalangeal joint or metatarsophalangeal joint.
The intermediate phalanx is not only intermediate in location, but also in size. The thumb and large toe do not possess a middle phalanx; the distal phalanges are the bones at the tips of the toes. The proximal and distal phalanges articulate with one another through interphalangeal articulations; each phalanx consists of a central part, called the body, two extremities. The body is flat on either side, concave on the palmar surface, convex on the dorsal surface, its sides are marked with rough areas giving attachment to fibrous sheaths of flexor tendons. It tapers from above downwards; the proximal extremities of the bones of the first row present oval, concave articular surfaces, broader from side to side than from front to back. The proximal extremity of each of the bones of the second and third rows presents a double concavity separated by a median ridge; the distal extremities are smaller than the proximal, each ends in two condyles separated by a shallow groove. In the foot, the proximal phalanges have a body, compressed from side to side, convex above, concave below.
The base is concave, the head presents a trochlear surface for articulation with the second phalanx. The middle are rather broader than the proximal; the distal phalanges, as compared with the distal phalanges of the finger, are smaller and are flattened from above downward. In the hand, the distal phalanges are flat on their palmar surface and with a roughened, elevated surface of horseshoe form on the palmar surface, supporting the finger pulp; the flat, wide expansions found at the tips of the distal phalanges are called apical tufts. They support the fingertip nails; the phalanx of the thumb has a pronounced insertion for the flexor pollicis longus, an ungual fossa, a pair of unequal ungual spines. This asymmetry is necessary to ensure that the thumb pulp is always facing the pulps of the other digits, an osteological configuration which provides the maximum contact surface with held objects. In the foot, the distal phalanges are flat on their dorsal surface, it is tapers to the distal end.
The proximal part of the phalnx presents a broad base for articulation with the middle phalanx, an expanded distal extremity for the support of the nail and end of the toe. The phalanx ends in a crescent-shaped rough cap of bone epiphysis — the apical tuft which covers a larger portion of the phalanx on the volar side than on the dorsal side. Two lateral ungual spines project proximally from the apical tuft. Near the base of the shaft are two lateral tubercles. Between these a V-shaped ridge extending proximally serves for the insertion of the flexor pollicis longus. Another ridge at the base serves for the insertion of the extensor aponeurosis; the flexor insertion is sided by two fossae — the ungual fossa distally and the proximopalmar fossa proximally. The number of phalanges in animals is expressed as a "phalangeal formula" that indicates the numbers of phalanges in digits, beginning from the innermost medial or proximal. For example, humans have a 2-3-3-3-3 formula for the hand, meaning that the thumb has two phalanges, whilst the other fingers each have three.
In the distal phalanges of the hand the centres for the bodies appear at the distal extremities of the phalanges, instead of at the middle of the bodies, as in the other phalanges. Moreover, of all the bones of the hand, the distal phalanges are the first to ossify; the distal phalanges of ungulates carry and shape nails and claws and these in primates are referred to as the ungual phalanges. The term phalanx or phalanges refers to an ancient Greek army formation in which soldiers stand side by side, several rows deep, like an arrangement of fingers or toes. Most land mammals including humans have a 2-3-3-3-3 formula in feet. Primitive reptiles had the formula 2-3-4-4-5, this pattern, with some modification, remained in many reptiles and in the mammal-like reptiles; the phalangeal formula in the flippers of cetaceans is 2-12-8-1. In vertebrates, proximal phalanges have a similar placement in the corr
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
Extensor digitorum brevis muscle
The extensor digitorum brevis muscle is a muscle on the upper surface of the foot that helps extend digits 1 through 4. The muscle originates from the forepart of the upper and lateral surface of the calcaneus, from the interosseous talocalcaneal ligament and the stem of the inferior extensor retinaculum; the fibres pass obliquely forwards and medially across the dorsum of the foot and end in four tendons. The medial part of the muscle known as extensor hallucis brevis, ends in a tendon which crosses the dorsalis pedis artery and inserts into the dorsal surface of the base of the proximal phalanx of the great toe; the other three tendons insert into the lateral sides of the tendons of extensor digitorum longus for the second and fourth toes. Nerve supply: lateral terminal branch of Deep Peroneal Nerve. Same innervation of Extensor Hallucis Brevis Extensor digitorum brevis extends the first four digits at the metatarsophalangeal joint and assists in extending the second and fourth digits at the interphalangeal joint.
The fifth digit, lacking any insertion from extensor digitorum brevis, can only be raised by the long extensor. Extensor digitorum longus muscle Extensor hallucis brevis Extensor digitorum muscle Anatomy photo:16:st-0405 at the SUNY Downstate Medical Center - "The Foot: Muscles" "Anatomy diagram: 39960.000-1". Roche Lexicon - illustrated navigator. Elsevier. Archived from the original on 2014-01-01. PTCentral
Interphalangeal joints of the hand
The interphalangeal joints of the hand are the hinge joints between the phalanges of the fingers that provide flexion towards the palm of the hand. There are two sets in each finger: "proximal interphalangeal joints", those between the first and second phalanges "distal interphalangeal joints", those between the second and third phalangesAnatomically, the proximal and distal interphalangeal joints are similar. There are some minor differences in how the palmar plates are attached proximally and in the segmentation of the flexor tendon sheath, but the major differences are the smaller dimension and reduced mobility of the distal joint; the PIP joint exhibits great lateral stability. Its transverse diameter is greater than its antero-posterior diameter and its thick collateral ligaments are tight in all positions during flexion, contrary to those in the metacarpophalangeal joint; the capsule, extensor tendon, skin are thin and lax dorsally, allowing for both phalanx bones to flex more than 100° until the base of the middle phalanx makes contact with the condylar notch of the proximal phalanx.
At the level of the PIP joint the extensor mechanism splits into three bands. The central slip attaches to the dorsal tubercle of the middle phalanx near the PIP joint; the pair of lateral bands, to which contribute the extensor tendons, continue past the PIP joint dorsally to the joint axis. These three bands are united by a transverse retinacular ligament, which runs from the palmar border of the lateral band to the flexor sheath at the level of the joint and which prevents dorsal displacement of that lateral band. On the palmar side of the joint axis of motion, lies the oblique retinacular ligament which stretches from the flexor sheath over the proximal phalanx to the terminal extensor tendon. In extension, the oblique ligament prevents passive DIP flexion and PIP hyperextension as it tightens and pulls the terminal extensor tendon proximally. In contrast, on the palmar side, a thick ligament prevents hyperextension; the distal part of the palmar ligament, called the palmar plate, is 2 to 3 millimetres thick and has a fibrocartilaginous structure.
The presence of chondroitin and keratan sulfate in the dorsal and palmar plates is important in resisting compression forces against the condyles of the proximal phalanx. Together these structures protect the tendons passing behind the joint; these tendons can sustain traction forces thanks to their collagen fibers. The palmar ligament is more flexible in its central-proximal part. On both sides it is reinforced by the so-called check rein ligaments; the accessory collateral ligaments originate at the proximal phalanx and are inserted distally at the base of the middle phalanx below the collateral ligaments. The accessory ligament and the proximal margin of the palmar plate are flexible and fold back upon themselves during flexion; the flexor tendon sheaths are attached to the proximal and middle phalanges by annular pulleys A2 and A4, while the A3 pulley and the proximal fibres of the C1 ligament attach the sheaths to the mobile volar ligament at the PIP joint. During flexion this arrangement produces a space at the neck of the proximal phalanx, filled by the folding palmar plate.
The palmar plate is supported by a ligament on either side of the joint called the collateral ligaments, which prevent deviation of the joint from side to side. The ligaments can or tear and can avulse with a small fracture fragment when the finger is forced backwards into hyperextension; this is called a "palmar plate, or volar plate injury". The palmar plate forms a semi-rigid floor and the collateral ligaments the walls in a mobile box which moves together with the distal part of the joint and provides stability to the joint during its entire range of motion; because the palmar plate adheres to the flexor digitorum superficialis near the distal attachment of the muscle, it increases the moment of flexor action. In the PIP joint, extension is more limited because of the two so called check-rein ligaments, which attach the palmar plate to the proximal phalanx; the only movements permitted in the interphalangeal joints are extension. Flexion is more extensive, about 100°, in the PIP joints and more restricted, about 80°, in the DIP joints.
Extension is limited by the collateral ligaments. The muscles generating these movements are: The relative length of the digit varies during motion of the IP joints; the length of the palmar aspect decreases during flexion while the dorsal aspect increases by about 24 mm. The useful range of motion of the PIP joint is 30–70°, increasing from the index finger to the little finger. During maximum flexion the base of the middle phalanx is pressed into the retrocondylar recess of the proximal phalanx, which provides maximum stability to the joint; the stability of the PIP joint is dependent of the tendons passing around it. Rheumatoid arthritis spares the distal interphalangeal joints. Therefore, arthritis of the distal interphalangeal joints suggests the presence of osteoarthritis or psoriatic arthritis. Interphalangeal joints of foot Hand kinesiology at the University of Kansas Medical Center Diagram at depuy.com Volar Plate Injury - Hand Therapy This article incorporates text in the public domain from page 333 of the 20th edition of Gray's Anatomy