Digestive system Questions in English

(C) The dental formula expresses the arrangement of teeth in each half of the upper and lower jaw.
The dental formula for permanent teeth in an adult human is represented as: $\frac{2123}{2123} \times 2 = 32$.
This indicates that in each half of the upper and lower jaw,there are $2$ incisors,$1$ canine,$2$ premolars,and $3$ molars.
Therefore,the total number of teeth in an adult human is $32$.

(N/A) Thecodont is a type of dentition in which each tooth is embedded in a socket of the jaw bone. This is a characteristic feature of mammals.
Diphyodont is a type of dentition in which two successive sets of teeth are developed during the lifetime of an organism. In humans,a temporary milk or deciduous set of teeth is replaced by a set of permanent or adult teeth.

(N/A) There are four different types of teeth in an adult human. They are as follows:
$(i)$ Incisors: The eight teeth in the front are incisors. There are four incisors each in the upper jaw and the lower jaw. They are meant for cutting.
$(ii)$ Canines: The pointy teeth on either side of the incisors are canines. They are four in number,two each placed in the upper jaw and the lower jaw. They are meant for tearing.
$(iii)$ Premolars: They are present next to the canines. They are eight in number,four each placed in the upper jaw and the lower jaw. They are meant for grinding.
$(iv)$ Molars: They are present at the end of the jaw,next to the premolars. There are twelve molars,six each placed in the upper jaw and the lower jaw.
Hence,the dental formula in humans is $\frac{2123}{2123} \times 2 = 32$.
This means each half of the upper jaw and the lower jaw has $2$ incisors,$1$ canine,$2$ premolars,and $3$ molars. Thus,an adult human has $32$ permanent teeth.

(N/A) The walls of the alimentary canal are made up of four layers. These are as follows:
$(i)$ Serosa is the outermost layer of the human alimentary canal. It is made up of a thin layer of secretory epithelial cells,with some connective tissues underneath.
$(ii)$ Muscularis is a thin layer of smooth muscles arranged into an outer longitudinal layer and an inner circular layer.
$(iii)$ Sub-mucosa is a layer of loose connective tissues,containing nerves,blood,and lymph vessels. It supports the mucosa.
$(iv)$ Mucosa is the innermost lining of the lumen of the alimentary canal. It is mainly involved in absorption and secretion.

(N/A) Food is the basic requirement of all living organisms.
- The major components of our food are carbohydrates,proteins,and fats.
- Minerals and vitamins are also required in small quantities.
- Food provides energy for various activities.
- Food provides organic materials for the growth and repair of tissues.
- Water plays a crucial role in metabolic processes and prevents dehydration of the body.
- Bio-macromolecules in food cannot be utilized by our body in their original form.
- They must be broken down and converted into simple substances in the digestive system.
- The process of conversion of complex food substances into simple absorbable forms is called digestion,which is carried out by our digestive system through mechanical and biochemical methods.

(N/A) Digestive organs are the structures involved in the ingestion of food,digestion,absorption,and egestion.
These include the alimentary canal and associated digestive glands.
$1$. Alimentary Canal: It starts with the mouth and ends with the anus. Key parts include the mouth,oral cavity,pharynx,oesophagus,stomach,small intestine (duodenum,jejunum,ileum),and large intestine (caecum,colon,rectum,anus).
$2$. Associated Digestive Glands: These include the salivary glands (parotid,submaxillary,and sublingual glands),liver (with gall bladder),and pancreas.
The human digestive system is formed by the coordination of these organs to process food into absorbable nutrients.

(N/A) The human digestive system consists of the alimentary canal and associated digestive glands.
The alimentary canal begins with an anterior opening—the mouth,and it opens out posteriorly through the anus.
The mouth leads to the oral cavity or buccal cavity. The oral cavity has a number of teeth and a muscular tongue.
The pharynx serves as a common passage for food and air. The oesophagus and the trachea (wind pipe) open into the pharynx.
$A$ cartilaginous flap called epiglottis prevents the entry of food into the glottis—opening of the wind pipe—during swallowing.
The oesophagus is a thin,long tube which extends posteriorly passing through the neck,thorax and diaphragm and leads to a '$J$' shaped bag-like structure called stomach.
The stomach leads to the small intestine,which is distinguishable into three regions—a '$C$' shaped duodenum,a long coiled middle portion jejunum and a highly coiled ileum.
The opening of the stomach into the duodenum is guarded by the pyloric sphincter.
Ileum opens into the large intestine. It consists of caecum,colon and rectum. The caecum is a small blind sac which hosts some symbiotic micro-organisms. $A$ narrow finger-like tubular projection,the vermiform appendix which is a vestigial organ,arises from the caecum.
The caecum opens into the colon. The colon is divided into three parts—an ascending,a transverse and a descending part. The descending part opens into the rectum which opens out through the anus.
The digestive glands associated with the alimentary canal include the salivary glands,the liver and the pancreas.

(N/A) The mouth is the anterior opening of the alimentary canal.
It leads into the oral or buccal cavity.
The oral cavity contains a number of teeth and a muscular tongue.
The roof of the oral cavity is formed by the palate,which consists of an anterior hard palate and a posterior soft palate.
The uvula is a small,fleshy projection hanging from the middle of the soft palate.
The sides of the oral cavity are formed by muscular cheeks,which are connected to the lips.
The lips are muscular folds covered by skin on the outer surface and a mucous membrane on the inner surface.
The lower jaw contains the hyoid bone,to which the tongue is attached.

(N/A) Thecodont: Each tooth is embedded in a socket of the jaw bone. This type of attachment is called thecodont.
Diphyodont: At the age of $6$ years,a set of temporary milk teeth or deciduous teeth are replaced by a set of permanent or adult teeth. This type of dentition is called diphyodont.
Types of Teeth: The majority of mammals,including human beings,form two sets of teeth during their life:
$(i)$ Deciduous or milk teeth
(ii) Permanent or adult teeth
The number of milk teeth is $20$. The dental formula of a child is $\frac{2102}{2102}$.
An adult human has $32$ permanent teeth which are of four different types. There are $16$ teeth in each jaw. The arrangement of teeth in each half of the upper and lower jaw in the order of Incisors $(I)$,Canines $(C)$,Premolars $(PM)$,and Molars $(M)$ is represented by a dental formula,which in humans is $\frac{2123}{2123}$.
The hard chewing surface of the teeth is made up of enamel.

(N/A) Pharynx: The oesophagus and the trachea open into the pharynx.
The pharynx is located behind the nasal cavity,oral cavity,and larynx. It is divided into three parts:
$(i)$ Nasopharynx
$(ii)$ Oropharynx
$(iii)$ Laryngopharynx
Function: It serves as a common passage for food and air. $A$ cartilaginous flap called the epiglottis prevents the entry of food into the glottis during swallowing.
$(b)$ Oesophagus: The oesophagus is a thin,long tube. It is situated behind the trachea and in front of the vertebral column. It extends posteriorly,passing through the neck,thorax,and diaphragm,and leads to a '$J$'-shaped,bag-like structure called the stomach.
$A$ muscular gastro-oesophageal sphincter regulates the opening of the oesophagus into the stomach.
Function: It transports food into the stomach via peristaltic movements.
$(c)$ Stomach: The stomach is the most enlarged part of the digestive tract. It is located in the upper left portion of the abdominal cavity. It has three major parts:
$(i)$ Cardiac portion: The part into which the oesophagus opens.
$(ii)$ Fundic region: The main,dome-shaped part of the stomach.
$(iii)$ Pyloric portion: The distal part that opens into the first part of the small intestine (duodenum).
Function: It stores food temporarily,churns it,and mixes it with gastric juices to convert it into chyme.

(N/A) Small Intestine: It is a tube approximately $6.25 \,m$ long, beginning at the pyloric sphincter of the stomach. It is divided into three parts:
$(i)$ Duodenum: The initial $'U'$-shaped part, approximately $25 \,cm$ long.
$(ii)$ Jejunum: The long, coiled middle portion, approximately $1 \,m$ long.
$(iii)$ Ileum: The final, highly coiled part of the small intestine.
Function: Primary site for digestion of food and absorption of nutrients.
$(b)$ Large Intestine: It is approximately $1.5 \,m$ long and consists of the caecum, colon, and rectum.
$(i)$ Caecum: $A$ small blind sac that hosts symbiotic microorganisms. $A$ narrow, finger-like tubular projection, the vermiform appendix (a vestigial organ), arises from it.
$(ii)$ Colon: Divided into three parts: Ascending, Transverse, and Descending colon.
$(iii)$ Rectum: The descending colon opens into the rectum, which stores feces until it is eliminated through the anus.
Function: Absorption of water, minerals, and certain drugs.

(N/A) The wall of the alimentary canal from the oesophagus to the rectum possesses four layers:
$(a)$ Serosa: Serosa is the outermost layer and is made up of a thin mesothelium with some connective tissues.
$(b)$ Muscularis: It is formed by smooth muscles usually arranged into an inner circular and an outer longitudinal layer.
$(c)$ Sub-mucosa: The sub-mucosal layer is formed of loose connective tissues containing nerves,blood,and lymph vessels. In the duodenum,glands are also present in the sub-mucosa.
$(d)$ Mucosa: The innermost layer lining the lumen of the alimentary canal is the mucosa. This layer forms irregular folds in the stomach and small finger-like projections called villi in the small intestine.
The cells lining the villi produce numerous microscopic projections called microvilli,giving a brush-border appearance. These modifications increase the surface area enormously.
Villi are supplied with a network of capillaries and a large lymph vessel called a lacteal.
Mucosal epithelium has goblet cells which secrete mucus that helps in lubrication.
Mucosa also forms glands in the stomach (gastric glands) and crypts in between the bases of villi in the intestine (Crypts of Lieberkuhn).
All the four layers show modifications in different parts of the alimentary canal.

(N/A) The wall of the alimentary canal from the oesophagus to the rectum possesses four layers:
$(a)$ Serosa: Serosa is the outermost layer and is made up of a thin mesothelium (epithelium of visceral organs) with some connective tissues.
$(b)$ Muscularis: It is formed by smooth muscles,usually arranged into an inner circular and an outer longitudinal layer.
$(c)$ Sub-mucosa: The sub-mucosal layer is formed of loose connective tissues containing nerves,blood,and lymph vessels. In the duodenum,glands are also present in the sub-mucosa.
$(d)$ Mucosa: The innermost layer lining the lumen of the alimentary canal is the mucosa. This layer forms irregular folds (rugae) in the stomach and small finger-like projections called villi in the small intestine.
The cells lining the villi produce numerous microscopic projections called microvilli,giving a brush-border appearance. These modifications increase the surface area enormously.
Villi are supplied with a network of capillaries and a large lymph vessel called a lacteal.
Mucosal epithelium has goblet cells which secrete mucus that helps in lubrication.
Mucosa also forms glands in the stomach (gastric glands) and crypts in between the bases of villi in the intestine (Crypts of Lieberkuhn).
All the four layers show modifications in different parts of the alimentary canal.

(A) The arrangement of teeth in each half of the upper and lower jaw in the order of Incisors $(I)$,Canines $(C)$,Premolars $(PM)$,and Molars $(M)$ is represented by a dental formula.
For an adult human,the dental formula is $\frac{2123}{2123}$,which means there are $2$ incisors,$1$ canine,$2$ premolars,and $3$ molars in each half of both the upper and lower jaws.
This results in a total of $32$ teeth $(8 \times 4 = 32)$.

(B) Human beings possess four different types of teeth,namely incisors,canines,premolars,and molars. This arrangement of different types of teeth is known as heterodont dentition.
Incisors are chisel-shaped and are used for cutting and biting.
Canines are pointed and are used for tearing food.
Premolars and molars have broad,flat surfaces and are specialized for chewing and grinding food.

(N/A) $(1)$ Diphyodont: Human beings and the majority of mammals form 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.
$(2)$ Thecodont: In mammals,each tooth is embedded in a socket of the jaw bone. This type of attachment is called thecodont.

(N/A) $(1)$ Heterodont: In humans and many mammals,teeth are of different types based on their shape and function. These are categorized into four types: Incisors,Canines,Premolars,and Molars. This condition of having different types of teeth is known as heterodont dentition.
$(2)$ Appendix: The caecum is a small blind sac which hosts some symbiotic micro-organisms and is located at the junction of the small and large intestine. $A$ narrow,finger-like tubular projection,known as the vermiform appendix,arises from the caecum.

(N/A) $(1)$ Villi: Located in the mucosa of the small intestine. They provide a large surface area for the absorption of digested food components.
$(2)$ Oxyntic cells (Parietal cells): Located in the gastric glands of the stomach. They secrete dilute $HCl$ and intrinsic factor,which is essential for the absorption of vitamin $B_{12}$.

(N/A) The human alimentary canal consists of the following organs:
$(i)$ Mouth,$(ii)$ Pharynx,$(iii)$ Oesophagus,$(iv)$ Stomach,$(v)$ Small intestine,$(vi)$ Large intestine,$(vii)$ Rectum,$(viii)$ Anus.
The major digestive glands and their locations are:
$(i)$ Salivary glands: Located in the oral cavity; they secrete saliva.
$(ii)$ Liver: The largest gland of the body,located in the upper right quadrant of the abdominal cavity,just below the diaphragm. It secretes bile.
$(iii)$ Pancreas: Located in the '$U$' shaped curve of the duodenum. It functions as both an endocrine and an exocrine gland.

(A) The term 'Thecodont' describes the arrangement where teeth are embedded in the jaw bone socket.
Similarly,the term 'Diphyodont' describes the condition where teeth are formed twice in a lifetime,i.e.,a set of temporary milk or deciduous teeth replaced by a set of permanent or adult teeth.

(B) $(1)$ Bile is the correct answer because it does not contain any digestive enzymes. It helps in the emulsification of fats.
$(2)$ The Caecum is a vestigial organ in humans,often associated with the vermiform appendix,which is a narrow finger-like tubular projection arising from it.

(A) The human stomach is anatomically divided into three major parts:
$(i)$ Cardiac portion: Into which the oesophagus opens.
$(ii)$ Fundic region: Which is the upper,dome-shaped portion.
$(iii)$ Pyloric portion: Which opens into the first part of the small intestine (duodenum).

(B) The large intestine is distributed into three parts: $caecum$, $colon$, and $rectum$.

(N/A) $(i)$ Chyme: In the stomach,food is mixed thoroughly with the acidic gastric juice (containing $HCl$ and enzymes). This partially digested,acidic,semi-solid food mass is known as chyme.
$(ii)$ Lymph: Lymph is a colourless fluid containing specialized lymphocytes,which are responsible for the immune responses of the body. It is essentially a filtered blood plasma that lacks red blood cells and large protein molecules.

(C) Goblet cells are specialized unicellular glands found in the epithelial lining of the alimentary canal. These cells are modified from columnar epithelial cells. They are responsible for the secretion of mucus,which helps in the lubrication and protection of the intestinal lining.

(D) The correct statement is that the ileum is a highly coiled part of the small intestine.
- The vermiform appendix arises from the caecum,not the duodenum.
- The ileum opens into the large intestine,specifically the caecum,not the small intestine.
- The serosa is the outermost layer of the alimentary canal,not the innermost (the innermost is the mucosa).

(B) The wall of the alimentary canal is made up of $4$ layers: mucosa,submucosa,muscularis,and serosa. The mucosa is the innermost layer of the alimentary canal. Therefore,option $B$ is correct.
- The ileum is the final part of the small intestine itself,so it does not open into the small intestine.
- While the ileum is a coiled part,it opens into the caecum of the large intestine.
- The vermiform appendix arises from the caecum,not the duodenum.

(A) Vitamin $B_{12}$,also known as cobalamin,was first isolated from the liver. It is a water-soluble vitamin that plays a crucial role in the functioning of the brain and nervous system,and in the formation of red blood cells. While it is now produced industrially using specific bacteria,its initial discovery and isolation were achieved from animal liver tissue.

(C) In the given figure:
$A$ represents the caecum,which is a small blind sac that hosts some symbiotic microorganisms.
$B$ is the vermiform appendix,a narrow finger-like tubular projection arising from the caecum.
$C$ is the ascending colon,which is the first part of the colon moving upwards.
$D$ is the transverse colon,which runs across the abdomen.
$E$ is the descending colon,which moves downwards.
$F$ is the sigmoid colon,which is the $S$-shaped part leading to the rectum.
Therefore,the correct identification is $A$ - Caecum,$B$ - Vermiform appendix,$C$ - Ascending colon,$D$ - Transverse colon,$E$ - Descending colon,$F$ - Sigmoid colon.

(A) Goblet cells are specialized simple columnar epithelial cells that are responsible for the production and secretion of mucus.
These cells are named 'goblet' cells because their shape resembles a goblet or a wine cup,which is caused by the accumulation of mucin granules in the apical portion of the cell during the secretion process.
Mucus acts as a lubricant and protects the lining of various organs,such as the digestive and respiratory tracts.

(C) The $Ileo-caecal$ valve is a sphincter muscle situated at the junction of the small intestine (ileum) and the large intestine (caecum).
Its primary function is to allow the passage of digested food (chyme) from the ileum into the caecum.
Crucially,it prevents the backflow of faecal matter from the large intestine into the small intestine,thereby maintaining the unidirectional flow of the digestive process.

(C) Cud chewing animals are called ruminants. These animals swallow their grazed food into the rumen,which is a specialized chamber of the stomach. In the rumen,the food is mixed with mucus and undergoes partial anaerobic digestion of cellulose by symbiotic bacteria.

(C) The small intestine is divisible into three regions: a $C$-shaped duodenum,a long coiled middle portion jejunum,and a highly coiled ileum.
The ileum is the distal part of the small intestine.
It opens into the large intestine,specifically into the first part known as the caecum.

(A) Crypts of Lieberkühn,also known as intestinal glands,are found in the mucosa of the small intestine between the bases of the villi.
These glands are responsible for the secretion of $succus$ $entericus$,which is the intestinal juice containing various enzymes for digestion.
Therefore,the correct location is the small intestine.

(C) In rabbits (as in other mammals), the reverse flow of food from the stomach back into the esophagus is prevented by the $Cardiac$ $\text{sphincter}$.
This sphincter acts as a valve at the junction of the esophagus and the stomach.
The $Pyloric$ $\text{sphincter}$ is located at the junction of the stomach and the small intestine, which regulates the passage of chyme into the intestine.

(B) Vitamin-$B_{12}$ is not found in plants. While some sources suggest Spirulina (an alga) may contain $B_{12}$,it is primarily synthesized by microorganisms. In ruminant mammals,the rumen (a specialized stomach compartment) contains a dense population of symbiotic bacteria that synthesize large quantities of Vitamin-$B_{12}$,which the animal then absorbs.

(C) The gastro-oesophageal sphincter is also known as the cardiac sphincter.
It is located at the junction of the oesophagus and the cardiac part of the stomach.
It is named 'cardiac' because it is situated near the heart.
It functions as a sphincter to prevent the backflow of gastric contents into the oesophagus.

(B) The oral cavity consists of a number of teeth and a muscular tongue.
Teeth are embedded in a socket of the jaw bone; this type of attachment is called $thecodont$.
Most mammals have two sets of teeth during their life,which is known as $diphyodont$.
Temporary or deciduous teeth ($20$ in number) are replaced by permanent teeth.
An adult human has $32$ teeth,i.e.,$16$ in each jaw.
These are of four different types $(heterodont)$,namely incisors $(I)$,canines $(C)$,premolars $(PM)$,and molars $(M)$.
Therefore,the dentition in human beings is $diphyodont$,$heterodont$,and $thecodont$.

(A) The dental formula represents the number of teeth in one half of the upper jaw divided by the teeth in one half of the lower jaw.
For an adult human,the arrangement of teeth is $2$ incisors,$1$ canine,$2$ premolars,and $3$ molars in each half of both jaws.
Therefore,the human dental formula is $I \frac{2}{2} C \frac{1}{1} PM \frac{2}{2} M \frac{3}{3}$.

(A) Diastema is the gap in the teeth along the jawbone.
In herbivores,the diastema separates the incisors from the premolars,resulting in an elongation of the jaw and aiding in feeding.

(B) Enamel is the hardest substance in the human body. It covers the dentine in the crown of the tooth.
There are two primary types of cells involved in tooth formation:
$1$. $Odontoblasts$: These cells are responsible for the formation of dentine.
$2$. $Ameloblasts$: These cells are responsible for the secretion and formation of enamel.

(B) The common bile duct and the pancreatic duct open together into the duodenum as the common hepato-pancreatic duct.
This duct is guarded by a sphincter called the Sphincter of Oddi.
However,the specific opening of the common bile duct (ductus choledochus) before it joins the pancreatic duct is guarded by the Sphincter of Boyden.
In many standard contexts,the Sphincter of Oddi is the primary answer for the hepato-pancreatic opening,but based on the provided diagram,the sphincter guarding the bile duct specifically is the Sphincter of Boyden.

(B) There are three pairs of salivary glands in human beings,namely,parotid glands,sublingual glands,and submaxillary (submandibular) glands.
All three pairs of glands secrete saliva into the buccal cavity through their respective ducts.
Therefore,the statement that there are four pairs of salivary glands is incorrect.
An adult person secretes about $1000-1500 \; mL$ $(1-1.5 \; L)$ of saliva per day.

(A) The human digestive system consists of the alimentary canal and associated digestive glands. The sequence of the alimentary canal is: Mouth $\rightarrow$ Buccal cavity $\rightarrow$ Pharynx $\rightarrow$ Oesophagus $\rightarrow$ Stomach $\rightarrow$ Small intestine (Duodenum $\rightarrow$ Jejunum $\rightarrow$ Ileum) $\rightarrow$ Large intestine (Caecum $\rightarrow$ Colon $\rightarrow$ Rectum). The large intestine terminates into a $2-3 \; cm$ long anal canal,which opens to the exterior through the anus. Therefore,the sequence Descending part of colon $\rightarrow$ Rectum $\rightarrow$ Anus is the correct order.

(B) In the wall of the small intestine,specifically in the distal portion known as the ileum,there are aggregates of lymphoid tissue called Peyer's patches.
These patches are groups of lymph nodules that play a crucial role in the immune system by producing lymphocytes.
Rugae are prominent folds found in the lining of an empty stomach.
Villi are finger-like projections of the mucosa in the small intestine that increase the surface area for absorption.
Choroid plexus is a network of blood vessels in the ventricles of the brain that produces cerebrospinal fluid.

(A) Enamel is the hardest substance in the human body and covers the crown of the tooth. It provides the necessary hardness and durability required for the mastication (chewing) of food. The bulk of the tooth is composed of a hard substance called dentine,which is secreted by odontoblast cells. Since enamel is the specific outer layer that directly contacts and grinds food,it is the primary part involved in mastication.

(B) tooth consists of three regions,i.e.,crown,neck,and root.
The exposed part,the crown,is covered by the hardest material of the human body.
This hardest material is enamel,which is the secretion of $ameloblast$ cells.

(D) Brunner's glands are simple,branched tubular glands present in the submucosal layer of the duodenum.
These glands open into the crypts of Lieberkühn.
The goblet cells of Brunner's glands secrete mucus,which helps in lubricating the food and protecting the intestinal wall from acidic chyme.

(B) By observing the provided diagram of the human digestive system:
$A$ points to the Parotid gland,which is a major salivary gland.
$B$ points to the Gall bladder,which stores bile.
$C$ points to the Pharynx,the common passage for food and air.
$D$ points to the Pancreas,a glandular organ.
$E$ points to the Transverse colon,a part of the large intestine.
$F$ points to the Caecum,the blind sac at the beginning of the large intestine.
Therefore,the correct sequence is $A$-Parotid gland,$B$-Gall bladder,$C$-Pharynx,$D$-Pancreas,$E$-Transverse colon,$F$-Caecum.

(A) The symbiotic bacteria present in the colon of the human large intestine play a vital role in synthesizing certain vitamins.
Specifically,these bacteria produce Vitamin $B_{12}$ (Cyanocobalamin) and Vitamin $K$ (naphthoquinone).
Among the given options,Cyanocobalamin is the correct product synthesized by these bacteria.