Each lobule is polygonal and consists of a mass of polyhedral hepatic cells arranged in radial rows, called the hepatic cords, around a central or intralobular vein. Glands represent invaginations of the mucous epithelium. Mouth: The mouth is a transverse slit-like terminal aperture situated a little below the anterior tip of snout. Mucosa of small intestine is thrown into numerous folds, but there are no true villi nor definite glands nor crypts of higher vertebrates. On certain papillae are situated the taste buds. The inner mucous membrane lining is well developed and thrown out into large number of folds and equal number of alternating deep gastric pits, into the bases of which open the ducts of long tubular simple or branched gastric glands. Now the tongue is withdrawn into the buccal cavity.
It decomposes proteins and amino acids to ammonia from which urea is formed by a cyclical chain of reactions. Carbon dioxide of the blood diffuses out in the opposite direction. Bile only emulsifies fats, thus, liver is not a true digestive gland. These are separated from each other through septa. Liver converts it into harmless potassium sulphocyanide. Since the teeth in the right and left side of the mouth are mirror images of each other, the dental arrangement is represented as follows.
It starts with the lips and ends with the throat, covering the oral cavity, the tongue, and the jaw in between. General sensory innervation to the septum and lateral walls is delivered by the nasopalatine nerve branch of maxillary nerve and the nasociliary nerve branch of the ophthalmic nerve. Thereafter, chyme semi liquid mass of partially digested food moves along the digestive tract through the process of peristalsis. It transmits the nasopalatine nerve and greater palatine artery. The diameter of the oral fissure is controlled by the muscles of — principally the orbicularis oris. It must also be noted that frogs don't drink water like humans do.
The dentine of the tooth crown is covered by an extremely hard sub-stance called enamel. It is covered with small pimple-like bumps called taste buds, which enable it to distinguish five different flavors: sweet, bitter, salty, sour, and umami. Egestion or Defaecation : After absorption of digested food in the ileum, the remaining undigested solid residue like vegetable fibres and cellulose, etc. In the incisors of rodents, lagomorphs and elephants, pulp cavity is basally opened so these teeth grow continuously throughout life, and are called open rooted. Maybe you didn't want to spit half of that food out either as it would be kind of disgusting and embarrassing.
Atmospheric oxygen dissolves in the moisture of the respiratory surface and diffuses into the blood, through the thin wall of the capillary networks. Digestion and absorption of food takes place in this part. And yes, that made you look like a chipmunk. It takes place mainly in the duodenum and ileum as they are very much suited for this due to the development of various folds with villi-like processes, which increase the absorptive surface of these two regions of the alimentary canal. A mixture of the two kinds of air now rushes out through the open nostrils. Alimentary Canal: The alimentary canal of rabbit is a long coiled tube of variable diameter starting from mouth and terminatings at anus.
The first set is known as milk-teeth which are deciduous in the young condition. Together these two parts move back and forth to facilitate the tearing and chewing of food by the teeth. The vestibule communicates with the mouth proper via the space behind the third molar tooth, and with the exterior through the oral fissure. Frogs belong to Amphibia class and subphylum Vertebrata, which means that they are a class of vertebrates that live on land, but breed in water. Anus is guarded by anal sphincter. Their long ducts open behind the lower incisors. So they are also known as grinders.
Opposite the upper second molar tooth, the duct of the opens out into the vestibule, secreting salivatory juices. The middle ethmoidal sinuses empty out onto a structure called the ethmoidal bulla. Some specialised Kupffer cells are also found amongst liver cells which generally help in the destruction of many germs. It produces red blood corpuscles in the foetus of mammals. The Hydrochloric Acid: i Checks bacterial decomposition of the food, ii Stops the action of ptyalin on starch, iii Brings the food in acidic medium, iv Acts as an activator for the proenzymes-prorenin and propepsin, converting them into renin and pepsin respectively, and v Stops contractions of the stomach. The digested food is then assimilated in the small intestine and the waste is passed on to the large intestine.
Three pairs of glands are larger. In contrast to the hard palate, it is a muscular structure. In some individuals, a few nasal veins join with the sagittal sinus a dural venous sinus. It has no digestive enzymes; therefore, it does not take part directly in digestion but plays an important role in the process of digestion. A vascular periodontal membrane is found between the root and the socket.
True villi, glands and crypts of higher vertebrates are absent. Histology of the Alimentary Canal : Histologically, the wall of alimentary canal of frog and other vertebrates is made up of four distinct concentric layers. Crypts of Lieberkuhn are pocket-like structures between the villi. The buccal cavity is always distended with air and its mucous membrane is very richly supplied with blood vessels. Recently a large number of experiments have been conducted on the mechanism of the pulmonary respiration in frog. When feeding, the frog sits at a suitable place frequented by insects. Moreover, humans don't use their eyes while swallowing.
Our mission is to provide an online platform to help students to share notes in Biology. The act of swallowing, resulting in the passage of food back through the to the , simultaneously causes the epiglottis to close off the respiratory system, thereby ensuring that food does not enter the passages leading to the lungs. When stimulated, a reflex arc leads to contraction of the pharyngeal musculature and the elevation of the soft palate. It is always opened during breathing but closes while food is being swallowed. It secretes bile which is an alkaline dark green coloured fluid, having several organic and inorganic salts bile salts , bile pigments, cholesterol, lecithin, water as well as some waste substances.