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Most anal fissures are caused by stretching of the anal mucous membrane beyond its capability. [3] Superficial or shallow anal fissures look much like a paper cut, and may be hard to detect upon visual inspection; they will generally self-heal within a couple of weeks. However, some anal fissures become chronic and deep and will not heal.
The anal and posterior dorsal fin supported by a basal plate and three unjointed radials. The pectoral fin skeleton is composed of bones homologous to the tetrapod humerus , ulna , and radius , followed by a host of smaller bones anchoring the fin rays; the pelvic fin skeleton similarly has femur , tibia , and fibula .
The adult T. calyptocephalus is found in the gut of whales such as the sperm whale. It is normally present in the intestine, but can also occur in the bile duct . [ 3 ] The tapeworm can be almost 40 m (130 ft) in length with as many as 45,000 proglottids (segments). [ 4 ]
In effect, "tetrapod" is a name reserved solely for animals which lie among living tetrapods, so-called crown tetrapods. This is a node-based clade , a group with a common ancestry descended from a single "node" (the node being the nearest common ancestor of living species).
Generally, fissures are due to injury to the mucosa, or because of a poor local blood supply that prevents proper healing, with spasm of the external anal sphincter contributing. [9] The external anal sphincter can be relaxed by the application of glyceryl trinitrate creams, and constipation is managed with laxatives and improving hydration. [ 9 ]
Tetrapodomorpha (also known as Choanata [3]) is a clade of vertebrates consisting of tetrapods (four-limbed vertebrates) and their closest sarcopterygian relatives that are more closely related to living tetrapods than to living lungfish.
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Several groups of tetrapods, such as the reptillian snakes and mammalian cetaceans, have lost some or all of their limbs, and many tetrapods have returned to partially aquatic or (in the case of cetaceans and sirenians) fully aquatic lives. The tetrapods evolved from the lobe-finned fishes about 395 million years ago in the Devonian. [23]