The splenic artery branches off from the aorta and the celiac trunk to deliver oxygenated blood to the spleen, while the splenic vein carries deoxygenated blood away from the spleen to the hepatic portal vein. 

In general teeth of reptiles (except crocodile) are acrodont. Thus, teeth are fixed over bone and not embedded in sockets in jaws. The fangs of snakes are modified maxillary teeth of upper jaw. If pulled out these teeth can be replaced.

Humans have two sets of teeth- the deciduous or milk teeth and the permanent teeth. The milk premolars are absent in infants. Thus, dental formula of infants are 2102/ 2102 as against 2123/ 2123 in adult humans.

Hyperbilirubinemia is excessive bilirubin in blood. It is also called jaundice. It leads to deposition of bilirubin in mucous membrane, sclera and skin so that the patient looks yellow or icterus. Urine is yellow. It is caused by obstruction in bile duct, excessive hemolysis, or viral infection.

Majority of mammals including human being forms two sets of teeth during their life, a set of temporary, milk or deciduous teeth replaced by a set of permanent or adult teeth. This type of dentition is called diphyodont. An adult human has 32 permanent teeth, which are of four different types, namely, incisors (I), canine (C), premolars (PM) and molars(M). Arrangement of teeth in each half of the upper and lower jaw in the order I, C, PM, M is represented by a dental formula which in humanis 2123/ 2123. In children the premolars and last molar are absent. Hence the child has dental formula 2102/ 2102. The number of teeths according to this dental formula will be 20. These teeth will be diphyodont and (32-20) or 12 teeth will be monophyodont.

Enamel is the hardest substance in the human body and contains the highest percentage of minerals, 96%, with water and organic material. The primary mineral is hydroxyapatite, which is a crystalline calcium phosphate.

Majority of mammals including human being forms two sets of teeth during their life, a set of temporary, milk or deciduous teeth replaced by a set of permanent or adult teeth. This type of dentition is called diphyodont. An adult human has 32 permanent teeth, which are of four different types, namely, incisors (I), canine (C), premolars (PM) and molars(M). Arrangement of teeth in each half of the upper and lower jaw in the order I, C, PM, M is represented by a dental formula which in human is 2123/ 2123. The premolars and last molars are absent in children. Thus the teeth which grow twice are incisors, canines and two molars i.e., a total of 20 teeth.

Enamel is the hardest material of animal kingdom. Enamel is ectodermal. It is secreted by Ameloblast cells of the ectoderm. lt has maximum amount of inorganic salt (96%) in It. Inorganic salt are mainly found in the form of phosphate and carbonate of Ca, Mg, Na and K. 3% of water is found in the enamel. Along with it Keratin and  ossein are also found in teeth. Ossein is a protein of bones, remaining part of tooth develops from mesoderm of embryo.

Cheek teeth or post canines comprise the molar and premolar teeth in mammals. Cheek teeth are multicuspidate (having many cusps or tubercles). Mammals have multicuspidate molars.

Stomach - Foveolar cells are mucus-producing cells, which cover the inside of the stomach, protecting it from the corrosive nature of gastric acid. The mucus produced by these cells is extremely important, as it prevents the stomach from digesting itself.
Duodenum - Brunner's glands (or duodenal glands) are compound tubular submucosal glands present in the duodenum. The main function of these glands is to produce a mucus-rich alkaline secretion (containing bicarbonate) in order to: protect the duodenum from the acidic content of chyme (which is introduced into the duodenum from the stomach); provide an alkaline condition for the intestinal enzymes to be active, thus enabling absorption to take place and lubricate the intestinal walls.
Large intestine - Goblet cells reside throughout the length of the small and large intestine and are responsible for the production and maintenance of the protective mucus blanket by synthesizing and secreting high-molecular-weight glycoproteins, known as mucins. 

Teeth appear to have first evolved in sharks, and are not found in the more primitive jawless fish. Lampreys do have tooth-like structures on the tongue, these are in fact, composed of keratin, not of dentine or enamel, and bear no relationship to true teeth. 

• The premaxilla is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. 
• In humans, they are fused with the maxilla and usually termed as the incisive bone (the portion of the maxilla adjacent to the incisors). Hence,  Incisor is present in premaxilla of the human jaw.

Coronary artery disease develops when the major blood vessels that supply our heart with blood, oxygen, and nutrients become damaged or diseased. The disease is caused when plaque blocks the arteries which supply blood to the heart.

Hemoglobin is a protein present in the red blood cells. The hemoglobin carries oxygen in the blood and transfers it in our body, it is the element that gives red color to our blood. Iron works as a booster towards hemoglobin production in the blood.

Cockroaches belong to phylum Arthropoda which has well developed the digestive system. The digestion of starch in the buccal cavity is followed by complete grinding of food in crop and gizzard which finally enters the stomach. The digestive enzymes secreted by the gastric caeca act upon the food in the stomach. These enzymes include amylase, maltase, invertase, tryptase and lipase. The remaining carbohydrates, proteins and fats are digested here.The digested food is absorbed through the stomach walls into the surrounding space which is called the haemocoel. The haemocoel consists of a large number of fat bodies which are fat cells having fat globules, protein granules and glycogen. They form storage structures which transport to different parts of the body. So, the correct answer is option C.

The oesophagus leads into the stomach. The stomach is a muscular sac. The stomach is the most important site of protein digestion. Stomach wall has peptic cells, chief cells secrete pepsinogen and oxyntic and parietal cells secrete hydrochloric acid. The pepsinogen is activated to pepsin on exposure to hydrochloric acid. The pepsin is a chief proteolytic enzyme of the alimentary canal. Another important enzyme of the stomach is lysozyme which is antibacterial. Thus, the correct answer is option C.

The pylorus is a narrow cone shaped constriction present at the end of the stomach and the beginning of the small intestine. It contains two region antrum which connects the parts of the stomach and pyloric canal which connects the stomach and small intestine.  Thus, the correct answer is option B.

The gastric mucosa is present is in the inner wall of the stomach which secretes 1.2 to 1.5 litres of gastric juice per day. Gastric juice is a mixture of HCl, mucous and digestive enzymes which makes food particles soluble, initiates protein digestion and converts the gastric contents to a semiliquid mass called chyme, thus preparing it for further digestion in the small intestine. This juice is highly acidic because of its hydrochloric acid content, and it is rich in enzymes. 

Indigestion is inability to properly digest food resulting in abdominal distension due to gas or flatus. It is caused by overeating, spicy food, anxiety and disturbed secretions of digestive tract.

• The lowest part of pharynx is the laryngopharynx. It has two apertures, the anterior slit is 'glottis', through which it opens into the larynx and the posterior slit is 'gullet', which leads to the oesophagus.
• Thus, larynx opens into the pharynx by glottis. The glottis bear a leaf-like a cartilaginous flap, called the 'epiglottis'. Epiglottis cover the glottis during swallowing, to prevent the entry of food into it.
  Hence, the correct answer is B.

The palate is the roof the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but, in most other tetrapods, the oral and nasal cavities are not truly separate. The palate is divided into two parts, the anterior bony hard palate, and the posterior fleshy soft palate (or velum). The diaphragm, located below the lungs, is the major muscle of respiration. It is a large, dome-shaped muscle that contracts rhythmically and continuously, and most of the time, involuntarily. The trachea, colloquially called windpipe, is a tube that connects the pharynx and larynx to the lungs, allowing the passage of air. Thus, option B is correct.

Respiratory membrane must be semi- permeable in nature to allow the passage of small molecules and ions. It should also support the process of diffusion. Only large molecules are transported using channels or porins. In root, the ascent of sap takes place through simple diffusion. If cell membrane was not semi permeable then it could have never happen. If it was permeable or impermeable then it is difficult for cell to survive. Thus, option C is correct.

Air enters the body through the nose and mouth. After the nose and mouth air goes through the pharynx or throat. After the pharynx, air goes into the larynx or voice box. 

Respiratory membrane must be semi- permeable in nature to allow the passage of small molecules and ions. It should also support the process of diffusion. only large molecules are transported using channels or porins. In root, the ascent of sap takes place through simple diffusion. If cell membrane was not semi permeable then it could have never happen. If, it was permeable or impermeable then it is difficult for cell to survive. 

Smoking is a practice in which a substance is burned and the smoke is breathed in and absorbed into the bloodstream. Most commonly used substance is the dried leaves of the tobacco plant. Smoking is primarily practised for recreational drug use.
 The combustion of the dried plant leaves vaporizes and delivers active substances into the lungs where they are rapidly absorbed into the bloodstream and reach bodily tissue. 
Smoking generally has negative health effects, because smoke inhalation may cause effects on physiologic processes such as respiration.
Hence, the smoke inhaled by the respiratory system.
So, the correct option is ' the respiratory system'.

Actually, only about 350 mL of air (out of total 500 mL tidal volume) enters the lung alveoli for the exchange of gases. The remaining 150 mL fills the respiratory passage and is termed as dead air space because no exchange of gases takes place here.

Liver is the largest organ in the body. It helps in digestion and removes waste products and worn-out cells from the blood. Liver performs many functions, like it forms and secretes bile that contains bile acids to aid in the intestinal absorption of fats and the fat-soluble vitamins as A, D, E, K and $B _{12}$. Hence, it stores vitamins as A, D, E, K and $B _{12}$.

• The oral and nasal cavities lie near the body midline, inferior and medial to the orbital cavities, anterior to the pharynx and medial to the infratemporal fossa.
• They are separated from one another by the palate. 
• Each cavity has an entrance and an exit. Hence, Nasal chambers and buccal cavity are separated by the palate.

Pharynx  connects the nasal cavity and mouth to the larynx and esophagus. It is the common pathway for food and air. There are three regions nasopharynx, oropharynx, and laryngopharynx. Nasopharynx  an air passage; uvula prevents food from entering it during swallowing. Oropharynx posterior to the mouth, passageway for food and air. Laryngopharynx passageway for food and air. Directly posterior to the epiglottis and extends to the larynx, then becomes continuous with esophagus. 

Small intestine is made up of three parts- duodenum, jejunum and ileum. The intestinal wall bears microscopic finger like projections called villi. The Mucosa layer forms crypts in between the bases of villi in the intestine (crypts of Lieberkuhn). The crypts produce digestive juice.

Various smooth muscle sphincters regulate the flow of bile and pancreatic juice through the ampulla: the sphincter of the pancreatic duct, the sphincter of the bile duct, and the hepatopancreatic sphincter (Sphincter of Oddi).The sphincter of Oddi controls the introduction of bile and pancreatic secretions into the duodenum, as well as preventing the entry of duodenal contents into the ampulla.

Folds of small intestine are conical shaped villi.  Small slit like space is found at the base of villi. These spaces are called crypts of Lieberkuhn. The crypts of Leiberkuhn secrete succus entericus or intestinal juice. The succus entericus mainly contains water (99%) and various digestive enzymes (1%). 

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.

• The liver breaks down and filters out harmful substances in the body. It also converts vitamins, nutrients and medicines into substances that our bodies can use.
•  A central role in the toxicity of alcohol may be played by acetaldehyde itself. Although the liver converts acetaldehyde into acetic acid, it reaches a saturation point where some of it escapes into the blood stream.
•  The accumulated acetaldehyde exerts its toxic effects by inhibiting the mitochondria reactions and functions. Hence, The reason why the liver of alcohol addicts gets damaged is that it Accumulate excess of fats.

Liver along with muscles stores excess glucose as glycogen, which can be used in times of starvation to maintain blood glucose levels. Excess carbohydrates are also stored as fat in adipose tissue around visceral organs and underneath the skin. During starvation the fat in the adipose tissue can be metabolised to derive energy.

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. The total number of teeth in upper jaw are 16 and 12 teeth in lower jaw. Thus total number of teeth are 28.

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. There is a gap in both the jaws at the location of canines. It is called as diastema. The total number of teeth in upper jaw are 16 and 12 teeth in lower jaw. The total number of teeth are 28. 

Palate is differentiated into two parts- (i) Hard Palate  and (ii) Soft Palate. 

Teeth are ecto-mesodermal in origin. Major portion of teeth arises from Dermis. Part of tooth present outside the gums only is derived from ectoderm or Epidermis (Enamel part). In human teeth of upper jaw are attached to the Maxilla bone. While teeth of lower jaw are attached to mandible jaw. But in rabbit upper incisors are attached to premaxilla. While upper premolars and molars attached to the maxilla bone. While lower teeth are attached to dentary bone. Dentary comprises of the lower jaw.

Carnassial tooth is the fourth premolar. In wild canines, it is the main tooth used to break up or crush hard material in their diet such as bones or large pieces of meat.