The phalangeal joints of the index finger, however, offer some independence to its finger, due to the arrangement of its flexor and extension tendons.The carpal bones form two transversal rows, each forming an arch concave on the palmar side. Because the proximal arch simultaneously has to adapt to the articular surface of the radius and to the distal carpal row, it is by necessity flexible. In contrast, the capitate, the "keystone" of the distal arch, moves together with the metacarpal bones and the distal arch is therefore rigid. The stability of these arches is more dependent of the ligaments and capsules of the wrist than of the interlocking shapes of the carpal bones, and the wrist is therefore more stable in flexion than in extension. The distal carpal arch affects the function of the CMC joints and the hands, but not the function of the wrist or the proximal carpal arch. The ligaments that maintain the distal carpal arches are the transverse carpal ligament and the intercarpal ligaments (also oriented transversally). These ligaments also form the carpal tunnel and contribute to the deep and superficial palmar arches. Several muscle tendons attaching to the TCL and the distal carpals also contribute to maintaining the carpal arch.Compared to the carpal arches, the arch formed by the distal ends of the metacarpal bones is flexible due to the mobility of the peripheral metacarpals (thumb and little finger). As these two metacarpals approach each other, the palmar gutter deepens. The central-most metacarpal (middle finger) is the most rigid.
Theta toxin (Θ-toxin)Theta toxin is also employed by Clostridium perfingens as a virulence factor. Theta toxin also promotes vascular degradation as its counterpart alpha toxin. A platelet-activation factor is employed which triggers an acute inflammatory response in nearby tissues. This inflammatory response leads to constriction of surrounding arteries and promotes an anaerobic environment for Clostridium perfingens growth and pathophysiology. Beta toxin (β-toxin)Beta toxin is an integral virulence factor in promoting enterocolitics and enterotoxemia. This toxin uses pores in the cellular biolipid membrane to import a pathogenic factor into organisms. Pathophysiology
Gas gangrene is caused by exotoxin-producing Clostridium species (most often C. perfringens, and C. novyi, but less commonly C. septicum or C. ramnosum), which are mostly found in soil, but also found as normal gut flora, and other anaerobes (e.g., Bacteroides and anaerobic streptococci).Bacterium of the Clostridial species produce two toxins: alpha and theta toxins, which cause necrotizing damage to tissues.Other organisms may occasionally cause gas gangrene (for example, Klebsiella pneumoniae in the context of diabetes).A gas composition of 5.9% hydrogen, 3.4% carbon dioxide, 74.5% nitrogen, and 16.1% oxygen was reported in one clinical case.Myonecrosis differs slightly from other types of necrosis. While the underlying causes are almost identical, the type of affected tissue (in particular, muscle tissue) is significantly more important for the patients general health. Superficial necrosis is unsightly and can lead to unattractive scarring, but otherwise does not affect the patients likelihood of survival or physical capability to the same extent.