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Body Systems: The Basics
Published in Karen L. LaBat, Karen S. Ryan, Human Body, 2019
In the peripheral nervous system, up to three separate spinal nerves may contribute to a specific peripheral nerve in an arm or leg. Cutaneous sensory nerve distributions show the sections of skin served by individual peripheral sensory nerves. For example, the median nerve, a major nerve to the muscles of the hand also provides sensation to the skin on the thumb, index finger, middle finger, and the middle-finger side of the ring finger, primarily on the palmar aspect. The area boundaries for both dermatomal and cutaneous sensory nerve maps are inexact. Cutaneous nerve distributions can provide designers useful guidance for product placement, to prevent inadvertent injury to the more vulnerable peripheral nerves. Illustrations of these patterns can be difficult to locate, although Netter (1986, pp. 118–127), Gray (1966, pp. 971, 972, 996, 1000, 1003), and Jenkins (2002, pp. 120, 200, 291, 292, 347, 348) include cutaneous nerve maps. Cutaneous nerve distributions for the arms, hands, and legs are illustrated in Chapters 4, 5, and 7.
Work-Related Ill Health
Published in Céline McKeown, Office Ergonomics and Human Factors, 2018
The carpal tunnel is formed by eight small carpal bones in the wrist and the flexor retinaculum (also referred to as the carpal ligament). The finger flexor tendons travel from the forearm and pass under the carpal ligament and through this tunnel inside their synovial sheaths alongside the median nerve before inserting into the fingers (see Figure 11.5). The median nerve provides sensation to the thumb, middle finger, index finger, part of the ring finger, and a major proportion of the palm.
Work-Related III Health
Published in Céline McKeown, Office Ergonomics, 2007
The carpal tunnel is formed by eight small carpal bones in the wrist and the flexor retinaculum (also referred to as the carpal ligament). The finger flexor tendons travel from the forearm and pass under the carpal ligament and through this tunnel inside their synovial sheaths alongside the median nerve before inserting into the fingers (see Figure 11.5). The median nerve provides sensation to the thumb, middle finger, index finger, part of the ring finger and a major proportion of the palm.
Estimation of joint contact pressure in the index finger using a hybrid finite element musculoskeletal approach
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2020
Barthélémy Faudot, Jean-Louis Milan, Benjamin Goislard de Monsabert, Thomas Le Corroller, Laurent Vigouroux
All the tendons and muscles involved in index finger function were modelled: terminal extensor, flexor digitorum profundus (FDP) at distal interphalangeal (DIP) joint, extensor slip, radial band, ulnar band, flexor digitorum superficialis (FDS) at proximal interphalangeal (PIP) joint and long extensor (LE) (considering both extensor digitorum communis (EDC) and extensor digitorum indicis (EDI)), radial interosseus (RI), ulnar interosseus (UI), lumbrical (LU) at metacarpophalangeal (MCP) joint. Tendon paths were based on the same geometrical dataset (An et al. 1979) as the MSK model and scaled according to phalanx dimensions of the scanned subject. Each tendon was modelled using straight beams (B31) to connect the points given by the anatomical dataset, i.e. two points at each joint. The complex assembly of multi-directional fibres of the extensor hood mechanism was represented using a discrete rhomboidal network of strings as proposed by (Zancolli 1979). Multi-articular flexor tendons were held tight to the bone by annular pulleys and several small sheaths were modelled to hold the tendons of the extensor mechanism in the adequate position (see Figure 3(A)). Pulleys and sheaths were modelled with shell elements (S4) providing via-points for tendons and indirectly modelling the wrapping phenomena of tendons onto finger bones.
Development of a multifingered robotic hand with the thenar grasp function
Published in Advanced Robotics, 2020
Tomoo Yoneda, Daiki Morihiro, Ryuta Ozawa
The index finger is used for precision and power grasps. Especially, precision grasp is used for not only grasping objects but also in-hand manipulation and needs more actuators than the middle and ring fingers. However, due to the reduction of the structural complexity, we only consider the flexion/extension of the finger motion, and the distal two joints are coupled like the human index finger. Figure 7(b) shows the configuration of the gear trains of the index finger. Two driving degrees of freedom were given to three joints, and the distal two joints are softly interlocked at 1:1 by the passive gear train. The interlocked motion is realized not by the elastic deformation of the joint spring but by a set of equilibrium points that satisfy prescribed constraints, no driving force is required to maintain the prescribed connected motion. Thus, the actuator force can be efficiently used for grasps.