Postanal Tail of Your Dog

Postanal Tail of Your Dog

A movable tail that extends past the anal opening is a characteristic of animals belonging to the chordate phylum Chordata. This feature distinguishes them from the remaining Bilateria. Other chordate characteristics include pharyngeal pouches, a hollow dorsal nerve cord, and a notochord.

A tail helps in balance and locomotion in aquatic species. Some terrestrial vertebrates also have tails that help in courting and signalling danger.

Origin

A movable muscular tail is one of the features that distinguishes vertebrates from all other chordates. The other four are a closed circulatory system, notochord, pharyngeal gill slits and endostyle/thyroid gland. Animals that lack these characteristics belong to phylum Invertebrates, which includes earthworms, scorpions and spiders.

The origin of the anal tail remains a mystery. It appears in the adult form only in members of a subphylum called Cephalochordata, which contains the extinct genus Pikaia, fossils of which are found in Burgess Shales from the Cambrian Period, more than 500 million years ago. The development of the tail in these animals is a fascinating case study, but the exact mechanism is not known.

Until the revolutionary introduction of phylogenetic systematics by Willi Hennig, zoologists tried to explain evolution by assembling stages anal tail of assumed transformations in observed morphologies of different species (evolutionsreihen). This type of thinking was replaced by tree-thinking with the advent of cladistics.

A human anal tail is the remnant of a vestigial structure that was shed during embryonic development. The tail is not involved in locomotion but can help with balance, courting and signaling danger. It is also useful for stabilizing the spine in certain positions. In some terrestrial vertebrates, the tail is skeletal and functional, while in others it is completely vestigial and nonfunctional.

Function

The post-anal tail is a muscular area that extends posteriorly from the anus in chordates. It may assist in balance and locomotion. The four features that distinguish chordates from species in other phyla are a post-anal tail, a notochord, a dorsal hollow nerve cord, and pharangeal slits (also known as gill slits). Although nonchordate animals possess tails, they differ from the muscular post-anal tails of chordates in that they are often stubby and not skeletal.

The pharangeal slits in the pharynx (throat) were part of a filter-feeding system that filtered out water and allowed for a more effective intake of food particles from the environment. In fish, the slits have become modified as gill arches. Humans have a similar mechanism in their ears and eustachian tubes.

Chordates are also distinguished by their heterodont teeth, which are different shapes in each tooth, unlike the homogeneous tooth shape of a reptile’s teeth. Their tails are also vestigial and nonfunctional, but they help with balance, courting, and signaling when danger is nearby.

The notochord is a longitudinal structure that gives the chordate its name and later develops into the vertebral column in vertebrates. It is flanked by somitic mesoderm from which segmental musculature and vertebral elements arise. The post-anal tail is an extension of the notochord and dorsal hollow nerve cord and contains skeletal elements that allow chordates to move and to control their balance.

Significance

All chordates have a postanal tail, a posterior elongation of the body that extends past the anal opening. This feature appears during embryonic development and is a key characteristic that distinguishes them from non-chordates. It provides skeletal support, a source of locomotion in aquatic species, and helps with balance, courting, and signaling when danger is nearby. Some terrestrial vertebrates also have tails for these purposes.

The evolution of a postanal tail involves the recruitment of cell populations to the posterior end of the embryo. Gont et al. found that tail cells in the Xenopus embryo are derived from late blastoporal lip cells and that they retain organizer activity, which contributes to caudal formation. The growth of the tail bud is associated with reshuffling of cell fate and specification, and it may be that trunk cells are reassigned to a caudal fate as the anal opening closes during tail bud emergence.

Interestingly, the urochordates (sea squirts) do not have a tail. However, some arthropods, such as insects and crabs, have a structure at the end of their abdomen that resembles a tail. This is called a pygidium and is used for similar purposes as Anal manufacturers a postanal tail. However, it is not a true tail as it does not attach to the back of the animal. This is because arthropods are invertebrates, not vertebrates.

Treatment

If your dog develops a condition that results in anal sac fluid or feces getting trapped under the tail, it may become painful and itchy. Your veterinarian will check your dog’s general health and take a complete history of the problem before suggesting treatment. X-rays and/or ultrasound of the anal area will help to diagnose your dog’s condition.

Anal furunculosis can be treated by a combination of hydrotherapy and antibiotics. Hydrotherapy involves showering the affected area under the tail several times a day with lukewarm or cool water, at moderate pressure, for about 15 minutes at a time. This helps to loosen the stool, allowing it to flow more easily and decreases irritation and swelling. Many dogs with anal furunculosis get significant relief by doing this, and it’s important to do it every day if possible.

Other conditions that cause the anal sac to become impacted include hemorrhoids, anal warts and anal fistulas. Hemorrhoids are swollen veins in the lower rectum and anus, warts are caused by the human papilloma virus, and fistulas are abnormal ‘tunnels’ connecting the anal canal to other organs.

If the anal fissure becomes severe, your vet might recommend surgery to correct it. This operation, called a lateral internal sphincterotomy, removes the anal fissure and a small piece of muscle that controls the sphincter. There is a risk of incontinence following the procedure, but this usually improves with time.