Digestion & Absorption Test 4

• Ruminants are hooved animals with a stomach divided into four chambers- rumen, reticulum, omasum, and abomasum. 
• The rumen is the largest stomach compartment and consists of several sacs.

The small pouches caused by sacculation (sac formation) , which give the colon its segmented appearance, are the haustra of the colon.

Diastema is a toothless gap on rabbit's jaw bone due to absence of canine. Diastema help in manipulation of food during mastication and "gnawing".

Rabbits have 28 teeth: those 4 big incisors in front, a set of 4 'peg' teeth hiding directly behind the incisors, and then 20 pro-molars and molars in the back of their mouths for grinding forages. Rabbits use their incisors to break off forages, and then the molars in back grind side-to-side in order to pulverize the fibers.

The pH in the stomach is acidic (less than 7). The stomach is the site of digestion of proteins. Hydrochloric acid is secreted in the stomach, which makes the pH acidic. The acidic pH is required for activation and activity of proteolytic enzyme pepsin. 

Number of monophyodont teeth in man is 12. Monophyodont teeth refers to teeth which are not replaced during lifetime. This formula denotes number of teeth in half jaw. Therefore, 3×4 = 12, i.e number of monophyodont teeth.

Rabbit is herbivorous animal and depends on cellulose based food. It has no canines in jaw. The dental formula is 2 0 3 3 / 1 0 2 3 for incisors, canine, premolar and molars in each jaw. Thus the canines are absent.

The mucus and bicarbonates present in the gastric juice play an important role in lubrication and protection of the mucosal epithelium from excoriation by the highly concentrated hydrochloric acid.

• The epiglottis moves back and forth to prevent the passage of food and liquids into the lungs.
• The usual upright position of the epiglottis allows air to flow into the lungs and the larynx.
• When you swallow, the epiglottis flattens backward to cover the entrance to your larynx and prevent food from entering the lungs and windpipe.
• The epiglottis returns to its usual position after swallowing.

• Pharynx is the region behind the mouth, beneath the nasal cavity, and above the oesophagus and larynx.
• This region of the body is considered to be the common passage in both ingesting food and breathing.

Those big front teeth, called incisors, get all the attention, but an adult rabbit actually has a full set of 28 teeth. There are six incisors total: two on the top, two on the bottom, and two "peg teeth," which are tiny incisors located right behind the upper incisors.

Enamel is the hardest, white coloured outer part of the tooth, which covers the crown of the tooth.

Peyer’s patches are groupings of lymphoid follicles in the mucus membrane that lines your small intestine. Lymphoid follicles are small organs in the lymphatic system that are similar to lymph nodes.

• Rabbit is herbivorous animal and depends on cellulose based food. Thus, it has no canines in jaw. 
• Instead, there is a space between the incisors and premolars called the diastema.

Thecodont dentition is found in mammals in which root of the tooth is firmly fixed in a socket of the jawbone, making the attachment strongest in vertebrates. This is a peg and socket attachment with the help of cementum that surrounds the root portion of the tooth.

• Hyoid apparatus is located on the floor of the buccal cavity and in between the two arms of the mandibular arch.
• The hyoid apparatus provides a surface for the attachment of tongue muscles and respiratory muscles. 

Hard palate is always on the upper side of the anterior buccal cavity. In rabbit that portion is made up of premaxilla, maxilla and Palatine bones.

• Velum palati is the posterior muscular portion of the palate, forming an incomplete septum between the mouth and the oropharynx and between the oropharynx and the nasopharynx.
• It assists the levator veli palatini in elevating the palate to occlude and prevent entry of food into the nasopharynx during swallowing.

The palate is the roof the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity.

Cheek teeth or post-canines comprise the molar and premolar teeth in mammals. Cheek teeth are multicuspidate (having many folds or tubercles).

Enamel is the hardest substance of the human body derived from the ectodermal ameloblasts. The water content in it is negligible (≈ 3%)

Jacobson Organ ,also known as Vomeronassal organ is an organ of chemoreception that is part of the olfactory system of amphibians and reptiles that detects heavy moisture borne odour particles.

The sweat glands of dog are located on it's tongue. This is the reason why dogs pant a lot in summer to release excess heat from the body.

• The stomach, located in the upper left portion of the abdominal cavity, has three major parts: a cardiac portion where the esophagus opens, a fundic region and a pyloric portion which opens into the first part of small intestine.
• The most important part is the fundic part which forms the body of the stomach and produces most of the digestive enzymes for digestion.

Parietal cells (also known as oxyntic cells), are the stomach epithelial cells, that secrete gastric acid (HCl) and intrinsic factor. These cells are only located in glands found in a particular area of the stomach, known as the fundus.

• The main constituent of gastric acid is hydrochloric acid which is produced by parietal cells (also called oxyntic cells) in the gastric glands in the stomach.
•  Parietal cells contain an extensive secretory network (called canaliculi) from which the hydrochloric acid is secreted into the lumen of the stomach.

The sphincter of Oddi, abbreviated as SO, is a muscular valve that controls the flow of digestive juices through the ampulla of Vater into the second part of the duodenum. The sphincter of Oddi is relaxed by the hormone cholecystokinin via vasoactive intestinal peptide.

Ameloblasts are cells present only during tooth development that deposit tooth enamel, which is the hard outermost layer of the tooth forming the surface of the crown.

In rabbits, upper incisors are attached to premaxilla. Upper premolars and molars are attached to the maxilla bone. While lower teeth are attached to dentary bone. Dentary comprises of the lower jaw.