A nerve is an enclosed, cable-like bundle of nerve fibres called axons, in the peripheral nervous system. A nerve provides a common pathway for the electrochemical nerve impulses called action potentials that are transmitted along each of the axons to peripheral organs or, in the case of sensory nerves, from the periphery back to the central nervous system; each axon within the nerve is an extension of an individual neuron, along with other supportive cells such as Schwann cells that coat the axons in myelin. Within a nerve, each axon is surrounded by a layer of connective tissue called the endoneurium; the axons are bundled together into groups called fascicles, each fascicle is wrapped in a layer of connective tissue called the perineurium. The entire nerve is wrapped in a layer of connective tissue called the epineurium. In the central nervous system, the analogous structures are known as tracts; each nerve is covered on the outside by a dense sheath of the epineurium. Beneath this is a layer of flat cells, the perineurium, which forms a complete sleeve around a bundle of axons.
Perineurial septae subdivide it into several bundles of fibres. Surrounding each such fibre is the endoneurium; this forms an unbroken tube from the surface of the spinal cord to the level where the axon synapses with its muscle fibres, or ends in sensory receptors. The endoneurium consists of an inner sleeve of material called the glycocalyx and an outer, meshwork of collagen fibres. Nerves are bundled and travel along with blood vessels, since the neurons of a nerve have high energy requirements. Within the endoneurium, the individual nerve fibres are surrounded by a low-protein liquid called endoneurial fluid; this acts in a similar way to the cerebrospinal fluid in the central nervous system and constitutes a blood-nerve barrier similar to the blood-brain barrier. Molecules are thereby prevented from crossing the blood into the endoneurial fluid. During the development of nerve edema from nerve irritation, the amount of endoneurial fluid may increase at the site of irritation; this increase in fluid can be visualized using magnetic resonance neurography, thus MR neurography can identify nerve irritation and/or injury.
Nerves are categorized into three groups based on the direction that signals are conducted: Afferent nerves conduct signals from sensory neurons to the central nervous system, for example from the mechanoreceptors in skin. Efferent nerves conduct signals from the central nervous system along motor neurons to their target muscles and glands. Mixed nerves contain both afferent and efferent axons, thus conduct both incoming sensory information and outgoing muscle commands in the same bundle. Nerves can be categorized into two groups based on where they connect to the central nervous system: Spinal nerves innervate much of the body, connect through the vertebral column to the spinal cord and thus to the central nervous system, they are given letter-number designations according to the vertebra through which they connect to the spinal column. Cranial nerves innervate parts of the head, connect directly to the brain, they are assigned Roman numerals from 1 to 12, although cranial nerve zero is sometimes included.
In addition, cranial nerves have descriptive names. Specific terms are used to describe their actions. A nerve that supplies information to the brain from an area of the body, or controls an action of the body is said to "innervate" that section of the body or organ. Other terms relate to whether the nerve affects the same side or opposite side of the body, to the part of the brain that supplies it. Nerve growth ends in adolescence, but can be re-stimulated with a molecular mechanism known as "Notch signaling". If the axons of a neuron are damaged, as long as the cell body of the neuron is not damaged, the axons would regenerate and remake the synaptic connections with neurons with the help of guidepost cells; this is referred to as neuroregeneration. The nerve begins the process by destroying the nerve distal to the site of injury allowing Schwann cells, basal lamina, the neurilemma near the injury to begin producing a regeneration tube. Nerve growth factors are produced causing many nerve sprouts to bud.
When one of the growth processes finds the regeneration tube, it begins to grow towards its original destination guided the entire time by the regeneration tube. Nerve regeneration is slow and can take up to several months to complete. While this process does repair some nerves, there will still be some functional deficit as the repairs are not perfect. A nerve conveys information in the form of electrochemical impulses carried by the individual neurons that make up the nerve; these impulses are fast, with some myelinated neurons conducting at speeds up to 120 m/s. The impulses travel from one neuron to another by crossing a synapse, the message is converted from electrical to chemical and back to electrical. Nerves can be categorized into two groups based on function: An afferent nerve fiber conducts sensory information from a sensory neuron to the central nervous system, where the information is processed. Bundles of fibres or axons, in the peripheral nervous system are called nerves, bundles of afferent fibers are known as sensory nerves.
An efferent nerve fiber conducts signals from a motor neuron in the central nervous system to muscles. Bundles of these fibres are known as efferent nerves; the nervous system is the part of an animal that coordinates its actions by transmitting signals to and from different parts of its body. In vertebrates it consists of two main par
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
Deep branch of ulnar nerve
The deep branch of the ulnar nerve is a terminal motor branch of the ulnar nerve. It is accompanied by the deep palmar branch of ulnar artery, it passes between the flexor digiti minimi brevis. It perforates the opponens digiti minimi and follows the course of the deep palmar arch beneath the flexor tendons; as the deep ulnar nerve passes across the palm, it lies in a fibrous tunnel formed between the hook of the hamate and the pisiform. At its origin it innervates the hypothenar muscles; as it crosses the deep part of the hand, it innervates all the interosseous muscles and the third and fourth lumbricals. It ends by innervating the medial head of the flexor pollicis brevis, it sends articular filaments to the wrist-joint 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
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
The deltoid muscle is the muscle forming the rounded contour of the human shoulder. It is known as the'common shoulder muscle' in other animals such as the domestic cat. Anatomically, it appears to be made up of three distinct sets of fibers though electromyography suggests that it consists of at least seven groups that can be independently coordinated by the nervous system, it was called the deltoideus and the name is still used by some anatomists. It is called. Deltoid is further shortened in slang as "delt". A study of 30 shoulders revealed an average mass of 191.9 grams in humans, ranging from 84 grams to 366 grams. Previous studies showed that the insertion of the intramuscular tendons of the deltoid muscle formed three discrete sets of muscle fibers referred to as "heads": The anterior or clavicular fibers arise from most of the anterior border and upper surface of the lateral third of the clavicle; the anterior origin lies adjacent to the lateral fibers of the pectoralis major muscle as do the end tendons of both muscles.
These muscle fibers are related and only a small chiasmatic space, through which the cephalic vein passes, prevents the two muscles from forming a continuous muscle mass. The anterior deltoids are called front delts for short. Lateral or acromial fibers arise from the superior surface of the acromion process of the scapula, they are called lateral deltoid. This muscle is called middle delts, outer delts, or side delts for short, they are mistakenly called medial deltoid, wrong, as their origin is the least medial portion of the deltoid. Posterior or spinal fibers arise from the lower lip of the posterior border of the spine of the scapula, they are called posterior deltoid or rear deltoid. Fick divided these three groups of fibers referred to as parts or bands, into seven functional components as did Kapandji and Sakoma Y et al.: the anterior part has two components. In standard anatomical position, the central components lie lateral to the axis of abduction and therefore contribute to abduction from the start of the movement while the other components act as adductors.
During abduction most of these latter components are displaced laterally and progressively start to abduct. From this extensive origin the fibers converge toward their insertion on the deltoid tuberosity on the middle of the lateral aspect of the shaft of the humerus. Though traditionally described as a single insertion, the deltoid insertion is divided into two or three discernible areas corresponding to the muscle's three areas of origin; the insertion is an arch-like structure with strong anterior and posterior fascial connections flanking an intervening tissue bridge. It additionally gives off extensions to the deep brachial fascia. Furthermore, the deltoid fascia contributes to the brachial fascia and is connected to the medial and lateral intermuscular septa; the deltoid is supplied by the posterior circumflex humeral artery and the deltoid branch of the thoracoacromial artery which branches from the axillary artery. The deltoid is innervated by the axillary nerve; the axillary nerve originates from the anterior rami of the cervical nerves C5 and C6, via the superior trunk, posterior division of the superior trunk, the posterior cord of the brachial plexus.
Studies have shown. Three of these lie in the anatomical anterior head of the deltoid, one in the anatomical middle head, three in the anatomical posterior head of the deltoid; these neuromuscular segments are supplied by smaller branches of the axillary nerve, work in coordination with other muscles of the shoulder girdle include pectoralis major and supraspinatus. The axillary nerve is sometimes damaged during surgical procedures of the axilla, such as for breast cancer, it may be injured by anterior dislocation of the head of the humerus. When all its fibers contract the deltoid is the prime mover of arm abduction along the frontal plane; the arm must be medially rotated for the deltoid to have maximum effect. This makes the deltoid an antagonist muscle of the pectoralis major and latissimus dorsi during arm adduction; the anterior fibers assist the pectoralis major to flex the shoulder. The anterior deltoid works in tandem with the subscapularis and lats to internally rotate the humerus; the lateral fibers perform basic shoulder abduction when the shoulder is internally rotated, perform shoulder transverse abduction when the shoulder is externally rotated.
They are not utilized during strict transverse extension such as in rowing movements, which use the posterior fibers. The posterior fibers assist the latissimus dorsi to extend the shoulder. Other transverse extensors, the infraspinatus and teres minor work in tandem with the posterior deltoid as external rotators, antagonists to strong internal rotators like the pecs and lats. An important function of the deltoid in humans is preventing the dislocation of the humeral head when a person carries heavy loads; the function of abduction means that it would help keep carried objects a safer distance away from the thighs to avoid hitting them, as during a farmer's walk. It ensures a precise a
Common palmar digital arteries
Three common palmar digital arteries arise from the convexity of the superficial palmar arch and proceed distally on the second and fourth lumbricales muscles. Alternative names for these arteries are: common volar digital arteries, ulnar metacarpal arteries, arteriae digitales palmares communes, or aa. digitales volares communes. Each of these arteries receive the corresponding volar metacarpal artery and divide into a pair of proper palmar digital arteries. Atlas image: hand_blood1 at the University of Michigan Health System - "Palm of the hand, superficial dissection, anterior view"
Superficial palmar arch
The superficial palmar arch is formed predominantly by the ulnar artery, with a contribution from the superficial palmar branch of the radial artery. However, in some individuals the contribution from the radial artery might be absent, instead anastomoses with either the princeps pollicis artery, the radialis indicis artery, or the median artery, the former two of which are branches from the radial artery. Alternative names for this arterial arch are: superficial volar arch, superficial ulnar arch, arcus palmaris superficialis, or arcus volaris superficialis; the arch passes across the palm in a curve with its convexity downward, If one were to extend the thumb, the superficial palmar arch would lie 1 cm distal from a line drawn between the first web space to the Hook of Hamate. The superficial palmar arch extends more distally than the deep palmar arch; the connection between the deep and superficial palmar arterial arches is an example of anastomosis, can be tested for using Allen's test.
Three common palmar digital arteries arise from the arch, proceeding down on the second and fourth lumbrical muscles, respectively. They each receive a contribution from a palmar metacarpal artery. Near the level of the metacarpophalangeal joints, each common palmar digital artery divides into two proper palmar digital arteries. Four digital branches arise from this palmar arch. Deep palmar arch Palmar carpal arch Dorsal carpal arch This article incorporates text in the public domain from page 598 of the 20th edition of Gray's Anatomy lesson5artofhand at The Anatomy Lesson by Wesley Norman Atlas image: hand_blood1 at the University of Michigan Health System - "Palm of the hand, superficial dissection, anterior view"