Phalanx bone

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"Phalange" redirects here. Phalanx bone_sentence_0

For other uses, see Phalanx (disambiguation). Phalanx bone_sentence_1

Phalanx bone_table_infobox_0

Phalanx bonePhalanx bone_header_cell_0_0_0
DetailsPhalanx bone_header_cell_0_1_0
ArticulationsPhalanx bone_header_cell_0_2_0 Metacarpophalangeal, metatarsophalangeal, interphalangealPhalanx bone_cell_0_2_1
IdentifiersPhalanx bone_header_cell_0_3_0
LatinPhalanx bone_header_cell_0_4_0 phalanx

pl. phalangesPhalanx bone_cell_0_4_1

TA98Phalanx bone_header_cell_0_5_0 Phalanx bone_cell_0_5_1
TA2Phalanx bone_header_cell_0_6_0 ,Phalanx bone_cell_0_6_1

The phalanges /fəˈlændʒiːz/ (singular: phalanx /ˈfælæŋks/) are digital bones in the hands and feet of most vertebrates. Phalanx bone_sentence_2

In primates, the thumbs and big toes have two phalanges while the other digits have three phalanges. Phalanx bone_sentence_3

The phalanges are classed as long bones. Phalanx bone_sentence_4

Structure Phalanx bone_section_0

The phalanges are the bones that make up the fingers of the hand and the toes of the foot. Phalanx bone_sentence_5

There are 56 phalanges in the human body, with fourteen on each hand and foot. Phalanx bone_sentence_6

Three phalanges are present on each finger and toe, with the exception of the thumb and large toe, which possess only two. Phalanx bone_sentence_7

The middle and far phalanges of the fourth and fifth toes are often fused together (symphalangism). Phalanx bone_sentence_8

The phalanges of the hand are commonly known as the finger bones. Phalanx bone_sentence_9

The phalanges of the foot differ from the hand in that they are often shorter and more compressed, especially in the proximal phalanges, those closest to the torso. Phalanx bone_sentence_10

A phalanx is named according to whether it is proximal, middle, or distal and its associated finger or toe. Phalanx bone_sentence_11

The proximal phalanges are those that are closest to the hand or foot. Phalanx bone_sentence_12

In the hand, the prominent, knobby ends of the phalanges are known as knuckles. Phalanx bone_sentence_13

The proximal phalanges join with the metacarpals of the hand or metatarsals of the foot at the metacarpophalangeal joint or metatarsophalangeal joint. Phalanx bone_sentence_14

The intermediate phalanx is not only intermediate in location, but usually also in size. Phalanx bone_sentence_15

The thumb and large toe do not possess a middle phalanx. Phalanx bone_sentence_16

The distal phalanges are the bones at the tips of the fingers or toes. Phalanx bone_sentence_17

The proximal, intermediate, and distal phalanges articulate with one another through interphalangeal articulations. Phalanx bone_sentence_18

Bone anatomy Phalanx bone_section_1

Each phalanx consists of a central part, called the body, and two extremities. Phalanx bone_sentence_19

Phalanx bone_unordered_list_0

  • The body is flat on either side, concave on the palmar surface, and 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.Phalanx bone_item_0_0
  • 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.Phalanx bone_item_0_1
  • The distal extremities are smaller than the proximal, and each ends in two condyles (knuckles) separated by a shallow groove; the articular surface extends farther on the palmar than on the dorsal surface, a condition best marked in the bones of the first row.Phalanx bone_item_0_2

In the foot, the proximal phalanges have a body that is compressed from side to side, convex above, and concave below. Phalanx bone_sentence_20

The base is concave, and the head presents a trochlear surface for articulation with the second phalanx. Phalanx bone_sentence_21

The middle are remarkably small and short, but rather broader than the proximal. Phalanx bone_sentence_22

The distal phalanges, as compared with the distal phalanges of the finger, are smaller and are flattened from above downward; each presents a broad base for articulation with the corresponding bone of the second row, and an expanded distal extremity for the support of the nail and end of the toe. Phalanx bone_sentence_23

Distal phalanx Phalanx bone_section_2

In the hand, the distal phalanges are flat on their palmar surface, small, and with a roughened, elevated surface of horseshoe form on the palmar surface, supporting the finger pulp. Phalanx bone_sentence_24

The flat, wide expansions found at the tips of the distal phalanges are called apical tufts. Phalanx bone_sentence_25

They support the fingertip pads and nails. Phalanx bone_sentence_26

The phalanx of the thumb has a pronounced insertion for the flexor pollicis longus (asymmetric towards the radial side), an ungual fossa, and a pair of unequal ungual spines (the ulnar being more prominent). Phalanx bone_sentence_27

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. Phalanx bone_sentence_28

In the foot, the distal phalanges are flat on their dorsal surface. Phalanx bone_sentence_29

It is largest proximally and tapers to the distal end. Phalanx bone_sentence_30

The proximal part of the phalnx presents a broad base for articulation with the middle phalanx, and an expanded distal extremity for the support of the nail and end of the toe. Phalanx bone_sentence_31

The phalanx ends in a crescent-shaped rough cap of bone epiphysis — the apical tuft (or ungual tuberosity/process) which covers a larger portion of the phalanx on the volar side than on the dorsal side. Phalanx bone_sentence_32

Two lateral ungual spines project proximally from the apical tuft. Phalanx bone_sentence_33

Near the base of the shaft are two lateral tubercles. Phalanx bone_sentence_34

Between these a V-shaped ridge extending proximally serves for the insertion of the flexor pollicis longus. Phalanx bone_sentence_35

Another ridge at the base serves for the insertion of the extensor aponeurosis. Phalanx bone_sentence_36

The flexor insertion is sided by two fossae — the ungual fossa distally and the proximopalmar fossa proximally. Phalanx bone_sentence_37

Development Phalanx bone_section_3

The number of phalanges in animals is often expressed as a "phalangeal formula" that indicates the numbers of phalanges in digits, beginning from the innermost medial or proximal. Phalanx bone_sentence_38

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. Phalanx bone_sentence_39

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. Phalanx bone_sentence_40

Moreover, of all the bones of the hand, the distal phalanges are the first to ossify. Phalanx bone_sentence_41

Function Phalanx bone_section_4

The distal phalanges of ungulates carry and shape nails and claws and these in primates are referred to as the ungual phalanges. Phalanx bone_sentence_42

History of phalanges Phalanx bone_section_5

Etymology Phalanx bone_section_6

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. Phalanx bone_sentence_43

In animals Phalanx bone_section_7

Most land mammals including humans have a 2-3-3-3-3 formula in both the hands (or paws) and feet. Phalanx bone_sentence_44

Primitive reptiles usually had the formula 2-3-4-4-5, and this pattern, with some modification, remained in many later reptiles and in the mammal-like reptiles. Phalanx bone_sentence_45

The phalangeal formula in the flippers of cetaceans (marine mammals) varies widely due to hyperphalangy (the increase in number of phalanx bones in the digits). Phalanx bone_sentence_46

In humpback whales, for example, the phalangeal formula is 0/2/7/7/3; in pilot whales the formula is 1/10/7/2/1. Phalanx bone_sentence_47

In vertebrates, proximal phalanges have a similar placement in the corresponding limbs, be they paw, wing or fin. Phalanx bone_sentence_48

In many species, they are the longest and thickest phalanx ("finger" bone). Phalanx bone_sentence_49

The middle phalanx also a corresponding place in their limbs, whether they be paw, wing, hoof or fin. Phalanx bone_sentence_50

The distal phalanges are cone-shaped in most mammals, including most primates, but relatively wide and flat in humans. Phalanx bone_sentence_51

Primates Phalanx bone_section_8

The morphology of the distal phalanges of human thumbs closely reflects an adaptation for a refined precision grip with pad-to-pad contact. Phalanx bone_sentence_52

This has traditionally been associated with the advent of stone tool-making. Phalanx bone_sentence_53

However, the intrinsic hand proportions of australopiths and the resemblance between human hands and the short hands of Miocene apes, suggest that human hand proportions are largely plesiomorphic (as found in ancestral species) — in contrast to the derived elongated hand pattern and poorly developed thumb musculature of other extant hominoids. Phalanx bone_sentence_54

In Neanderthals, the apical tufts were expanded and more robust than in modern and early upper Paleolithic humans. Phalanx bone_sentence_55

A proposal that Neanderthal distal phalanges was an adaptation to colder climate (than in Africa) is not supported by a recent comparison showing that in hominins, cold-adapted populations possessed smaller apical tufts than do warm-adapted populations. Phalanx bone_sentence_56

In non-human, living primates the apical tufts vary in size, but they are never larger than in humans. Phalanx bone_sentence_57

Enlarged apical tufts, to the extent they actually reflect expanded digital pulps, may have played a significant role in enhancing friction between the hand and held objects during Neolithic toolmaking. Phalanx bone_sentence_58

Among non-human primates phylogenesis and style of locomotion appear to play a role in apical tuft size. Phalanx bone_sentence_59

Suspensory primates and New World monkeys have the smallest apical tufts, while terrestrial quadrupeds and Strepsirrhines have the largest. Phalanx bone_sentence_60

A study of the fingertip morphology of four small-bodied New World monkey species, indicated a correlation between increasing small-branch foraging and reduced flexor and extensor tubercles in distal phalanges and broadened distal parts of distal phalanges, coupled with expanded apical pads and developed epidermal ridges. Phalanx bone_sentence_61

This suggests that widened distal phalanges were developed in arboreal primates, rather than in quadrupedal terrestrial primates. Phalanx bone_sentence_62

Other mammals Phalanx bone_section_9

In ungulates (hoofed mammals) the forelimb is optimized for speed and endurance by a combination of length of stride and rapid step; the proximal forelimb segments are short with large muscles, while the distal segments are elongated with less musculature. Phalanx bone_sentence_63

In two of the major groups of ungulates, odd-toed and even-toed ungulates, what remain of the "hands" — the metacarpal and phalangeal bones — are elongated to the extent that they serve little use beyond locomotion. Phalanx bone_sentence_64

The giraffe, the largest even-toed ungulate, has large terminal phalanges and fused metacarpal bones able to absorb the stress from running. Phalanx bone_sentence_65

The sloth spends its life hanging upside-down from branches, and has highly specialized third and fourth digits for the purpose. Phalanx bone_sentence_66

They have short and squat proximal phalanges with much longer terminal phalanges. Phalanx bone_sentence_67

They have vestigial second and fifth metacarpals, and their palm extends to the distal interphalangeal joints. Phalanx bone_sentence_68

The arboreal specialization of these terminal phalanges makes it impossible for the sloth to walk on the ground where the animal has to drag its body with its claws. Phalanx bone_sentence_69

Additional images Phalanx bone_section_10

Phalanx bone_unordered_list_1

  • Phalanx bone_item_1_3
  • Phalanx bone_item_1_4

See also Phalanx bone_section_11

This article uses anatomical terminology. Phalanx bone_sentence_70

Phalanx bone_unordered_list_2

  • HandPhalanx bone_item_2_5
  • FootPhalanx bone_item_2_6

Credits to the contents of this page go to the authors of the corresponding Wikipedia page: bone.