Structure and functions of living organisms -ii - class-VI

The human heart allows the complete separation of the deoxygenated and oxygenated blood. It has four chambers, the upper two atria and the lower two ventricles. The right side chambers (right atrium and right ventricle) are concerned with the deoxygenated blood. The right atrium receives the deoxygenated blood from the body and the right ventricle pumps it to the lungs. This is the pulmonary circulation. It completes when the left side chamber of the left atrium receives it. So, the left side chambers are concerned with oxygenated blood. The left ventricle then transports it to the rest of the body in the systemic circulation. So, the pulmonary and the systemic circulation maintained by the human heart constitute the double circulation of the blood.

Circulatory system or cardiovascular system is the organ system that helps to transport oxygen, nutrients, hormones etc to all the cell of the body. It consists of heart, veins, arteries, capillaries. Thus, the correct answer is option D.

Vaso means vessels and constriction means narrowing, therefore, narrowing of blood vessels results in vasoconstriction. Normally, it is done due to the shrinking of smooth muscles of vessels to react according to the environment by raising blood pressure for stabilization, prevent loss of heat, control blood flow in body, transfer nutrients and prevent from blood and fluid loss but in some cases it can also be a severe health problem leading to hypertension or high bp.

The circulatory system transports gases, nutrients, and hormones. Nerve impulses are transmitted through the nervous system, not the circulatory system.

The Human circulatory system consists of a muscular four-chambered heart, a network of closed branching blood vessels and blood, the fluid which is circulated. The heart is a  4 chambered muscular organ present in the thoracic cavity in between the lungs. it does not have any bones. The chambers(spaces) of blood are filled with blood.T he muscular action of heart walls pump blood throughout the body through blood vessels. Hence the pumping 

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.

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.

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.

The nervous system is a collection of cells, tissues, and organs ( brain, spinal cord, nerves ) through which an organism receives information from its surroundings and then directs the organism to respond to the stimulus.

The brain regulates an array of functions necessary for survival. The brain houses our mind and our memories. Most available evidence suggests that the functions of memory are carried out by the hippocampus and other related structures in the temporal lobe of the brain. The brain also helps in the analysis of various body functions.

Human dentition can be describes as:

The nasal cavity is divided into two lateral halves by the nasal septum, which is formed by the vomer, the perpendicular plate of the ethmoid bone, and the septal cartilage.

Placental mammals have a maximum of three incisors and one canine per quadrant and usually have no more than four premolars and three molars per quadrant. Following dental formula represents the number of tooth in placental mammals.
Placental mammals =  I 3/3 C 1/1 P 4/4 M 3/3 =44

Humans, like other mammals, are diphyodont, meaning that they develop two sets of teeth. Among deciduous (primary) teeth, ten are found in the maxilla (upper jaw) and ten in the mandible (lower jaw), for a total of 20. The dental formula for primary teeth is 2.1.2/2.1.2.

A diastema is a space or gap between two teeth. It happens when there is an unequal relationship between the size of the teeth and the jaw.

Odontoblast is one of the dentin-forming cells, derived from mesenchyme of neural crest origin, lining pulp cavity of teeth; arranged in a peripheral layer in dental pulp, each with an odontoblastic process extending part way into dentinal tubules.

The four front teeth in each arch are called incisors, and their function is to cut food with their sharp thin edges.

A diastema is an area of extra space between two or more teeth. The two front teeth of the upper jaw area is where diastema is most frequently seen. Many children experience diastema as primary teeth fall out, though in most cases these spaces close when the permanent teeth erupt. Diastemas may also be caused by a tooth size discrepancy, missing teeth or an oversized labial frenum, the tissue that extends from the inside of the lip to the gum tissue where the upper two front teeth are located. Secondary reasons involve oral alignment issues such as a protrusion of the teeth. Thus, option B is correct.

The teeth of a carnivore are long and pointed, for tearing raw flesh. Herbivores have flat teeth and flat back molars to grind their food. Carnivores do not have flat back molars at all.  Some herbivores do have small, what we call “canine” teeth for biting into tough plants like apples but these are nothing compared to the size and shape of a carnivore’s teeth. True omnivores teeth are most similar to carnivore teeth. Thus, option B is correct. 

The four front teeth in each arch are called incisors, and their function is to cut food with their sharp thin edges. On each side of the incisors, at the corners of the mouth, are the canines. These teeth have one cusp, or pointed edge, and are used for holding or grasping food, and are very strong, stable teeth. Behind the canines are the premolars, which are designed for holding food like the canines because they have cusps, but they also function to crush food. Sometimes these teeth are referred to as bicuspids, meaning two cusps, but this is not always accurate because some premolars may have three cusps. Therefore the term premolar is preferred. The teeth farthest back in the mouth are the molars. These teeth have broad chewing surfaces with four or five cusps, and are designed for grinding food. The incisors and canines are called anterior teeth, because they are located in the front of the mouth, while the premolars and molars are called posterior teeth because they are located in the back of the mouth. Thus, option A is correct.

In anatomy, a heterodont is an animal which possesses more than a single tooth morphology. For example, members of the Synapsida generally possess incisors, canine, premolars, and molars. The presence of heterodont dentition is evidence of some degree of feeding/hunting specialization in a species. In contrast, homodont dentition refers to a set of teeth that possess the same tooth morphology. Acrodont is a formation of the teeth whereby the teeth are consolidated with the summit of the alveolar ridge of the jaw without sockets. Pleurodont is a formation of the teeth that are fused by their sides to the inner surface of the jaw bones. Thus, option D is correct.

The permanent molars occupy the most posterior portion of the dental arch. They have the largest occlusal surfaces of any of the teeth and have from three to five major cusps. Lower permanent molars always have two lingual cusps and upper permanent molars always have two buccal cusps. Lower molars have two roots and upper molars have three roots. Molar teeth by definition are cheek teeth that are not preceded by primary teeth. Permanent molars are accessional teeth without primary predecessors. In contrast to the molars, permanent incisors, canines and premolars are succedaneous (successional teeth). Premolar, canine and incisors does not have three roots. Thus, option A is correct.

A wisdom tooth or third molar is one of the three molars per quadrant of the human dentition. It is the most posterior of the three. Wisdom teeth generally erupt between the ages of 17 and 25. Most adults have four wisdom teeth (a third molar in each of the four quadrants), but it is possible to have fewer or more, in which case the extras are called supernumerary teeth. Wisdom teeth commonly affect other teeth as they develop, becoming impacted or "coming in sideways". They are often extracted when this occurs. 

Entamoeba gingivalis is a protozoan endoparasite, residing in the tartar and pus pockets of teeth of pyorrhoea infected human beings. It is the first parasitic amoeba known to human beings. 

The skeletal system is divided into an axial and appendicular skeleton and it provides both support protection to the brain as well as give shape to the face. The skull is part of the axial skeleton. Skull or cranium has 22 bones out which mandible  (lower jaw) is a single bone. It is lowest and strongest bone which hold the lower teeth in the socket and gives shape to the face. 

Hardest substance of the body is enamel. It is the thin outer covering of the tooth. It is composed of hydroxyapatite, which is a crystalline calcium phosphate. The color can vary from light yellow to a grayish white. It protects the tooth.

There are several types of teeth and each performs its own special function in the chewing process, depending on its size, shape, location within the jaws. Starting at the midline, the permanent dentition is comprised of incisors, canines, premolars and molars.
Therefore, the correct answer is option D.

Teeth are the hardest substance in the human body. The enamel on your teeth is the hardest and most highly mineralized substance in your body. It covers the outer layer of each tooth and it is the most visible part of the tooth. The enamel is made up mostly of minerals, primarily hydroxyapatite. So, enamel is the hardest substance in our body compared to dentine, collagen and melanin. 

Canines are pointed teeth located between the incisors and premolars, specifically adapted for tearing food, particularly flesh.

Dental pulp is an unmineralized oral tissue composed of soft connective tissue, vascular, lymphatic and nervous elements that occupies the central pulp cavity of each tooth. Pulp has a soft, gelatinous consistency. The pulp cavity extends down through the root of the tooth as the root canal which opens into the periodontium via the apical foramen. The blood vessels, nerves etc. of dental pulp enter and leave the tooth through this foramen. This sets up a form of communication between the pulp and surrounding tissue - clinically important in the spread of inflammation from the pulp out into the surrounding periodontium. 

Dentine is the calcified tissue of the body, is one of the components of the teeth along with enamel, cementum and pulp. It is generally surrounds the entire pulp is a covering beneath the enamel. 70% of the weight of dentine is made up of mineral hydroxylapatitie, while 20% is organic material and the rest 10% is water.

• The canines are the pointed and the sharp teeth which are found in the mouth of the humans. 
• These are the teeth that are used for tearing of the food. The sugarcane is made up of tough fibers. These fibers can be torn with the help of canine teeth. 
• Thus, the correct answer is option B. 

Human teeth have two sets of teeth during their life one temporary set of milk teeth and one permanent set. Once the milk teeth have replaced by permanents, then the permanent teeth are not going to replace again in life naturally after 12 years of age.

Human teeth have two sets of teeth during their life: one temporary set (milk teeth) and one permanent set milk teeth are young teeth that are replaced by permanent or adult teeth up to 12 years.

Canines are well developed in carnivore animals. They having pointed ends which help in tearing of fleshy food

An adult human has 32 permanent teeth which of four types, namely incisors, canines, premolar, and molars. Such type of dentition is called heterodont dentition.

Wisdom teeth are vestigial third molars, that help human ancestors in grinding down plant tissue. The skulls of human ancestors had larger jaws with more teeth to efficiently digest the cellulose that makes up a plant cell wall. As human diets changed, smaller jaws were naturally selected, yet the third molars or wisdom teeth still develop in humans.

In humans, there are 32 teeth present in which four different types of teeth are present and is known as heterodont dentition. In these four types canines,

Humans have 20 deciduous (baby) teeth that are replaced by permanent teeth. These are the teeth that grow twice.

Wisdom teeth are the third molars, and there are typically four of them in an adult set (one in each quadrant).

The permanent dental set in humans consists of 32 teeth. There are 2 canines in each jaw (upper and lower), totaling 4 canines.

Homodont teeth are teeth that are all similar in shape and size, commonly found in many reptiles and fish. Heterodont refers to teeth of different shapes, like in humans.

In one half of the upper jaw, there is 1 canine. Since there are two halves in the upper jaw, there are 2 canines total in the upper jaw.

Humans are diphyodont because they have two sets of teeth (milk and permanent) and heterodont because they have different types of teeth (incisors, canines, premolars, molars).

Incisors are the sharp, chisel-shaped front teeth primarily responsible for cutting and biting food. Canines are for tearing, while premolars and molars are for grinding.

A diastema is a gap or space between two teeth. It is commonly observed in animals like herbivores where certain teeth are absent.

The primary or milk dentition in humans consists of 20 teeth. These are eventually replaced by the permanent set of 32.

A diastema is specifically defined as a space or gap between two teeth in the dental arch.

Enamel is the hardest substance in the human body and forms the protective outer layer of the crown of the tooth.

Incisors are the front teeth shaped for cutting and nibbling. Canines are pointed for tearing, and molars are for grinding.

Primary (deciduous) dentition lacks premolars. The permanent set includes premolars, which replace the primary molars.

Opossums have the most teeth among land mammals - up to 50 teeth. Humans have 32, horses have around 36-44, and rats have 16. The answer is misspelled as 'Opssum' but refers to opossum.

Canines in the upper arch are also often called “eye teeth,” which, when you come to think of it, is kind of a weird name for them. But the most common explanation is actually pretty simple: these teeth lie directly below the eye sockets.

Van Leeuwenhoek examined single-celled organelles and called them as animalcules when he was working with the lenses.

• The molars or molar teeth are large, flat teeth at the back of the mouth. They are more developed in mammals. 
• They are used primarily to grind food during chewing.
• Molars show a great deal of diversity in size and shape across mammal groups. Hence, in mammals, mastication of the food is done by molars.
  

Carnassial teeth. which are pointed molars, would most likely be part of the dentition of a carnivore

A wisdom tooth or third molar is one of the three molars per quadrant of the human dentition. It is the most posterior of the three. Wisdom teeth generally erupt between the ages of 17 and 25

• The digestive glands (salivary glands, pancreas, liver, and gallbladder) produce or store secretions that the body carries to the digestive tract in ducts and breaks down chemically. 
• The teeth help in mechanical digestion by masticating (chewing) food.
•  The whole process starts in the oral cavity, where the saliva from the salivary glands mixes with the food and starts to begin the breakdown of food. This semi-digested food then travels down to the small intestine, where secretions from the liver, gallbladder, and pancreas further act on the food particles. Hence, Teeth are not only part of the digestive system that physically breaks down food.

Humans have four types of teeth, namely incisors, canines, premolars and molars. Each type of teeth has specific structure and function. The roots of teeth are embedded in the upper jaw and the lower jaw. Humans have 32 teeth, 8 incisors, 4 canines, 8 premolars and 12 molars. Canines and premolars have one root. Upper first premolars and lower molars have two roots. Upper molars have three roots.

Incisors are the front four teeth which are used for cutting/biting and slicing the food, canines are the pointed teeth which helps in tearing the food whereas molars are the teeth which are used for Grinding and chewing of food particles. 

A diastema is a gap between teeth mostly seen in the front teeth. It mainly occurs in mammals mostly in humans. It is caused by missing of teeth or undersized teeth.

The arrival of second teeth occurs at 6 years +/- 6 months. With the exception of the wisdom teeth, the last of the secondary teeth come in around 12 years of age. 

Carnassial teeth are the molar and premolar teeth modified for shearing flesh by having cusps with sharp cutting edges. They are typical of animals of the order carnivora (e.g., tigers, wolves), in which they are the first molars in the lower jaw and the last premolars in the upper.

Incisors are the most anterior teeth. Canines - all mammals have a single canine in each quadrant. The premolars lie immediately posterior to the canines. In the upper jaw, they are found in the maxillary. The most posterior teeth in the jaws of most mammals are molars. Humans have two incisors, one canine, two premolars, and three molars, I2 C1 P2 M3, in each quadrant of their upper jaws. The numbers for each quadrant of the lower jaw are the same, and the general formula is written I2/2 C1/1 P2/2 M3/3. 

Dental fluorosis, also termed as mottled enamel is an extremely common disorder. It is caused by overexposure to fluoride during the first eight years of life. This is the time when most permanent teeth are being formed. Clinical dental fluorosis is characterized by staining and pitting of the teeth. In more severe cases all the enamel may be damaged.. The early symptoms of skeletal fluorosis, include stiffness and pain in the joints.  Hence, the dental disease characterised by mottling of teeth is due to the presence of an ingredient in drinking water is fluorine.

So the correct answer is ''fluorine''

Heterodont is an animal which possesses more than a single tooth morphology. For example, humans possess incisors, canines (eyeteeth), premolars and molars.

Adult human teeth have 12 molars. They are biggest and strongest teeth. The large surface are o molars helps in grinding and chewing the food. They break up the food into pieces small enough for making it easy to swallow.

Osteoblast-bone forming cell. Ameloblast-enamel elaborating cell. Odontoblast- dentine elaborating cell. Dentoblast- tooth cell.

A normal adult mouth has 32 teeth. 

•  Incisors: The middlemost four teeth on the upper and lower jaws.
• Canines: The pointed teeth just outside the incisors. 
• Premolars: Teeth between the canines and molars.
• The molars or molar: teeth are large, flat teeth at the back of the mouth. Hence, an adult has 32 teeth.

Pulp cavity is the central cavity of a tooth containing the dental pulp and being made up of the root canal and the pulp chamber. Nasal cavity is present in nose, abdominal cavity in abdomen and chest cavity in chest.

The study of teeth generally referred to as dentistry. It is a branch of medicine that involves the study, diagnosis,
prevention, and treatment of diseases, disorders and conditions of the dentition along with oral cavity, including the oral mucosa, and the
adjacent and related structures and tissues of the maxillofacial zone.

Incisor is a narrow-edged tooth at the front of the mouth, adapted for cutting. In humans there are four incisors in each jaw. On each side of the incisors, at the corners of the mouth, are the canines. These teeth have one cusp, or pointed edge, and are used for holding or grasping food, and are very strong, stable teeth. Behind the canines are the premolars, which are designed for holding food like the canines because they have cusps, but they also function to crush food. Sometimes these teeth are referred to as bicuspids, meaning two cusps, but this is not always accurate because some premolars may have three cusps. Therefore, the term premolar is preferred. The teeth farthest back in the mouth are the molars. These teeth have broad chewing surfaces with four or five cusps, and are designed for grinding food. Thus, option D is correct.

There are 20 primary teeth which are lost as the child grows and is replaced by 32 permanent teeth. Primary dentition comprises of 8 incisors, 4 canines and 8 molars while permanent teeth comprises of 8 premolars in addition to newly formed 8 incisors, 4 canines and 12 molars. Premolars take the place of molars present in the primary dentition.

The seminiferous tubules are the location of the production of spermatozoa or sperms in the testicular lobule. The Leydig cells (interstitial cells) outside the seminiferous tubule synthesize and secrete testicular hormones called androgens or testosterone. Spermatogenesis is the process of immature male germ cells (spermatogonia) develop into mature sperms or spermatozoa. After this process, the conversion of the four equal haploid spermatids into spermatozoa (sperms) is called spermiogenesis. 

In frogs, body proportions do not change with their growth. This means that the weight and height of a frog increase and decrease proportionately. If one of these parameters increase, so does the other, and by the same proportion, and vice-versa. Hence, if a frog is twice as long as another, it will be approximately two times heavier also.

So, the correct answer is 'Two-fold'.

The graph of electrical activity of heart versus time produced by non-invasive medical procedure is called electrocardiograph. The process of recording the electrical activity of heart over a period of time is called as electrocardiography (ECG). The graph of electrical activity of brain versus time is called as electroencephalograph. The machine used to record the electrical activity of heart is called as electrocardiogram.