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Contrahentes
The contrahentes (singular contrahens) are muscles widely present in the hands of mammals, including monkeys. They are on the palmar/plantar side. There is one each for digits I, II, IV and V, but not III. They pull the fingers/toes down and together. Human anatomy In humans, the adductor pollicis muscle in the hand and the adductor hallucis in the foot are well-developed remnants of the first contrahens, though they have lost the insertion on the distal phalanx of the thumb or big toe. The other contrahentes only appear as rare atavistic abnormalities. In other mammals, the contrahentes may have their origin either on the carpus or the metacarpus, which suggests that the palmar interossei muscles also contain elements of the contrahentes. They appear in the human fetus as a layer of flesh which mostly disappears. In other animals The contrahens of the fourth digit is absent in dogs but present in cats and rabbits. In primates, the contrahentes vary in number between zero and f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adductor Pollicis Muscle
In human anatomy, the adductor pollicis muscle is a muscle in the hand that functions to adduct the thumb. It has two heads: transverse and oblique. It is a fleshy, flat, triangular, and fan-shaped muscle deep in the thenar compartment beneath the long flexor tendons and the lumbrical muscles at the center of the palm. It overlies the metacarpal bones and the interosseous muscles. Structure Oblique head The oblique head (Latin: ''adductor obliquus pollicis'') arises by several slips from the capitate bone, the bases of the second and third metacarpals, the intercarpal ligaments, and the sheath of the tendon of the flexor carpi radialis. Gray's Anatomy 1918. (See infobox) From this origin the greater number of fibers pass obliquely downward and converge to a tendon, which, uniting with the tendons of the medial portion of the flexor pollicis brevis and the transverse head of the adductor pollicis, is inserted into the ulnar side of the base of the proximal phalanx of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thumb
The thumb is the first digit of the hand, next to the index finger. When a person is standing in the medical anatomical position (where the palm is facing to the front), the thumb is the outermost digit. The Medical Latin English noun for thumb is ''pollex'' (compare ''hallux'' for big toe), and the corresponding adjective for thumb is ''pollical''. Definition Thumb and fingers The English word ''finger'' has two senses, even in the context of appendages of a single typical human hand: # Any of the five terminal members of the hand. # Any of the four terminal members of the hand, other than the thumb Linguistically, it appears that the original sense was the first of these two: (also rendered as ) was, in the inferred Proto-Indo-European language, a suffixed form of (or ), which has given rise to many Indo-European-family words (tens of them defined in English dictionaries) that involve, or stem from, concepts of fiveness. The thumb shares the following with each of the o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Muscle
Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscle tissue, and are often known as muscle fibers. The muscle tissue of a skeletal muscle is striated – having a striped appearance due to the arrangement of the sarcomeres. Skeletal muscles are voluntary muscles under the control of the somatic nervous system. The other types of muscle are cardiac muscle which is also striated and smooth muscle which is non-striated; both of these types of muscle tissue are classified as involuntary, or, under the control of the autonomic nervous system. A skeletal muscle contains multiple fascicles – bundles of muscle fibers. Each individual fiber, and each muscle is surrounded by a type of connective tissue layer of fascia. Muscle fibers are formed from the fusion of developmental myoblasts in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adductor Hallucis
The Adductor hallucis (Adductor obliquus hallucis) arises by two heads—oblique and transverse and is responsible for adducting the big toe. It has two heads, both are innervated by the lateral plantar nerve. Structure Oblique head The ''oblique head'' is a large, thick, fleshy mass, crossing the foot obliquely and occupying the hollow space under the first, second, third and fourth metatarsal bones. It arises from the bases of the second, third, and fourth metatarsal bones, and from the sheath of the tendon of the Peroneus longus, and is inserted, together with the lateral portion of the Flexor hallucis brevis, into the lateral side of the base of the first phalanx of the great toe. Transverse head The ''transverse head'' (''Transversus pedis'') is a narrow, flat fasciculus which arises from the plantar metatarsophalangeal ligaments of the third, fourth, and fifth toes (sometimes only from the third and fourth), and from the transverse ligament of the metatarsals. It is insert ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atavism
In biology, an atavism is a modification of a biological structure whereby an ancestral genetic trait reappears after having been lost through evolutionary change in previous generations. Atavisms can occur in several ways; one of which is when genes for previously existing phenotypic features are preserved in DNA, and these become expressed through a mutation that either knocks out the dominant genes for the new traits or makes the old traits dominate the new one. A number of traits can vary as a result of shortening of the fetal development of a trait (neoteny) or by prolongation of the same. In such a case, a shift in the time a trait is allowed to develop before it is fixed can bring forth an ancestral phenotype. Atavisms are often seen as evidence of evolution. In social sciences, atavism is the tendency of reversion. For example, people in the modern era reverting to the ways of thinking and acting of a former time. The word ''atavism'' is derived from the Latin ''atavus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Palmar Interossei Muscles
In human anatomy, the palmar or volar interossei (interossei volares in older literature) are three small, unipennate muscles in the hand that lie between the metacarpal bones and are attached to the index, ring, and little fingers. They are smaller than the dorsal interossei of the hand. Structure 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. Pollical palmar interosseous 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. The "pollical" palmar interosseous muscle (PPIM), is present in more than 80% of individuals and was first described by . Its presence has been verified by numerous anatomists since, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tarsier
Tarsiers ( ) are haplorhine primates of the family Tarsiidae, which is itself the lone extant family within the infraorder Tarsiiformes. Although the group was once more widespread, all of its species living today are found in Maritime Southeast Asia, specifically the Philippines, Malaysia, Indonesia, and Brunei.They are found primarily in forested habitats, especially forests that have liana, since the vine gives tarsiers vertical support when climbing trees. Evolutionary history Fossil record Fossils of tarsiiform primates are found in Asia, Europe, and North America, with disputed fossils from Africa, but extant tarsiers are restricted to several Southeast Asian islands in Indonesia, Philippines, and Malaysia. The fossil record indicates that their dentition has not changed much, except in size, in the past 45 million years. Within the family Tarsiidae, there are two extinct genera, '' Xanthorhysis'' and ''Afrotarsius''. However, the placement of ''Afrotarsius'' is not ce ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metacarpophalangeal Joint
The metacarpophalangeal joints (MCP) are situated between the metacarpal bones and the proximal phalanges of the fingers. These joints are of the condyloid kind, formed by the reception of the rounded heads of the metacarpal bones into shallow cavities on the proximal ends of the proximal phalanges. Being condyloid, they allow the movements of flexion, extension, abduction, adduction and circumduction at the joint. Structure Ligaments Each joint has: * palmar ligaments of metacarpophalangeal articulations * collateral ligaments of metacarpophalangeal articulations Dorsal surfaces The dorsal surfaces of these joints are covered by the expansions of the Extensor tendons, together with some loose areolar tissue which connects the deep surfaces of the tendons to the bones. Function The movements which occur in these joints are flexion, extension, adduction, abduction, and circumduction; the movements of abduction and adduction are very limited, and cannot be performed while th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Interphalangeal Articulations Of 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 (except in the thumb, which has only one joint): * "proximal interphalangeal joints" (PIJ or PIP), those between the first (also called proximal) and second (intermediate) phalanges * "distal interphalangeal joints" (DIJ or DIP), those between the second (intermediate) and third (distal) phalanges Anatomically, the proximal and distal interphalangeal joints are very 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. Joint structure 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 duri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Muscles Of The Upper Limb
Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscle tissue, and are often known as muscle fibers. The muscle tissue of a skeletal muscle is striated – having a striped appearance due to the arrangement of the sarcomeres. Skeletal muscles are voluntary muscles under the control of the somatic nervous system. The other types of muscle are cardiac muscle which is also striated and smooth muscle which is non-striated; both of these types of muscle tissue are classified as involuntary, or, under the control of the autonomic nervous system. A skeletal muscle contains multiple fascicles – bundles of muscle fibers. Each individual fiber, and each muscle is surrounded by a type of connective tissue layer of fascia. Muscle fibers are formed from the fusion of developmental myoblasts in a p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hand
A hand is a prehensile, multi-fingered appendage located at the end of the forearm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs. A few other vertebrates such as the koala (which has two opposable thumbs on each "hand" and fingerprints extremely similar to human fingerprints) are often described as having "hands" instead of paws on their front limbs. The raccoon is usually described as having "hands" though opposable thumbs are lacking. Some evolutionary anatomists use the term ''hand'' to refer to the appendage of digits on the forelimb more generally—for example, in the context of whether the three digits of the bird hand involved the same homologous loss of two digits as in the dinosaur hand. The human hand usually has five digits: four fingers plus one thumb; these are often referred to collectively as five fingers, however, whereby the thumb is included as one of the fingers. It has 27 bones, not including the sesamoid bone, the number o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Muscles Of The Lower Limb
Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscle tissue, and are often known as muscle fibers. The muscle tissue of a skeletal muscle is striated – having a striped appearance due to the arrangement of the sarcomeres. Skeletal muscles are voluntary muscles under the control of the somatic nervous system. The other types of muscle are cardiac muscle which is also striated and smooth muscle which is non-striated; both of these types of muscle tissue are classified as involuntary, or, under the control of the autonomic nervous system. A skeletal muscle contains multiple fascicles – bundles of muscle fibers. Each individual fiber, and each muscle is surrounded by a type of connective tissue layer of fascia. Muscle fibers are formed from the fusion of developmental myoblasts in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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