![]() ![]() The cloaca also receives the openings of ureters, urinary bladder and the oviducts in female frog. Its hinder end leads to a cavity called cloaca. The large intestine is a short and wide tube. The ileum leads at its lower end into the large intestine or colon or rectum. ![]() This layer consists of two types of cells – goblet cells which produce mucus and absorptive cells which absorb digested food material. The mucosa layer of ileum has thrown into finger – like folds called villi which increase the absorptive area of intestine. The small intestine has all the four usual layers of the alimentary canal viz., serosa, muscularis, submucosa and mucosa. The duodenum receives the hepatopancreatic duct. The duodenum run forward and forms ‘U’ shaped structure with the stomach. It is differentiated into proximal duodenum and distal ileum. The small intestine is long, narrow and tubular. It consists of two parts – the small intestine and the large intestine. The stomach leads into the longest tubular part of the alimentary canal – the intestine. The stomach leads into the intestine through a pyloric sphincter. Internally there are longitudinal folds in the stomach which enable the stomach to expand whenever needed. It is differentiated into anterior, broader and larger cardiac stomach and posterior, narrower and smaller pyloric stomach. Stomach is a thick, muscular and ‘J’ shaped part of the alimentary canal. The oesophagus leads into the stomach but there is no clear demarcation line between oesophagus and stomach to differentiate these two parts externally. It is short because of the absence of neck. The gullet leads into a short and wide tubular oesophagus. The upper surface of the tongue has small papillae (taste buds) and mucous glands. The tongue can be everted and retracted with the help of protractor and retractor hypoglossal muscles while capturing the prey. The floor of the bucco-pharyngeal cavity contains a large, thick, fleshy, bifid tongue. These act as resonators (increase the pitch of sound) at the time of croaking. In male frogs, a pair of opening of vocal sacs is found on the floor of the buccal cavity near the jaw angles. The openings of the Eustachian tubes connect the pharynx with the middle ear. The vertical slit like glottis leads to the laryngo tracheal chamber. Gullet is the larger and transverse aperture which leads the buccopharyngeal cavity into the oesophagus and it opens only at the time of swallowing of the food. This region has a gullet in the centre, glottis below the gullet and a pair of openings of Eustachian tubes, one on either side near the left and the right jaw angles. The region posterior to the in-bulgings is the pharyngeal region. The maximum portion of the roof of the buccal cavity is occupie by the in-bulging of the eye-balls. Through the internal nares, the external nostrils or nares open into the bucco-pharyngeal cavity. The roof of the bucco-pharyngeal cavity also has a pair of internal nares one on the outer side of vomerine teeth. Teeth are not used for chewing but prevent the escape of prey, so they are prehensile in function. ![]() The teeth are homodont (similar), acrodont (attached to the bones) and polyphyodont (in many sets). They are in two patches one on each side of the median line of the roof of the bucco-pharyngeal cavity. The vomerine teeth are found on vomer bones. They are small hook like and are arranged closely in a row. The maxillary teeth are found on maxilla bone of upper jaw. They are of two types-maxillary teeth and vomerine teeth. It is bounded by two jaws-upper and lower jaws. The mouth leads into a wide and broad buccopharyngeal cavity. ![]()
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