Digestive glands Questions in English

(N/A) Liver: The liver is the largest gland of the body,weighing about $1.2$ to $1.5 \ kg$ in an adult human. It is situated in the abdominal cavity,just below the diaphragm,and has two lobes. The hepatic lobules are the structural and functional units of the liver containing hepatic cells arranged in the form of cords. Each lobule is covered by a thin connective tissue sheath called the Glisson's capsule.
Gall Bladder: The bile secreted by the hepatic cells passes through the hepatic ducts and is stored and concentrated in a thin,muscular sac called the gall bladder. The duct of the gall bladder (cystic duct) along with the hepatic duct from the liver forms the common bile duct.
Pancreas: The pancreas is a compound (both exocrine and endocrine) elongated organ situated between the limbs of the $'U'$-shaped duodenum. The exocrine portion secretes an alkaline pancreatic juice containing enzymes,and the endocrine portion secretes hormones,such as insulin and glucagon.
Common Duct System: The bile duct and the pancreatic duct open together into the duodenum as the common hepato-pancreatic duct,which is guarded by a sphincter called the sphincter of Oddi.

(N/A) Pancreatic juice is a vital digestive secretion produced by the pancreas and released into the duodenum. It contains several inactive enzymes, active enzymes, and bicarbonate ions.
$1$. Inactive Enzymes (Zymogens): These include $Trypsinogen$, $Chymotrypsinogen$, and $Procarboxypeptidases$. $Trypsinogen$ is activated by $Enterokinase$ (secreted by the intestinal mucosa) into $Trypsin$, which subsequently activates the other zymogens.
$2$. Active Enzymes:
- $Pancreatic \text{ } Amylase$: Hydrolyzes polysaccharides (starch) into disaccharides.
- $Pancreatic \text{ } Lipase$: Acts on emulsified fats to break them down into diglycerides and monoglycerides.
- $Nucleases$: Break down nucleic acids ($DNA$ and $RNA$) into nucleotides and nucleosides.
$3$. Bicarbonate Ions: These provide an alkaline $pH$ (approximately $7.8 - 8.4$) to the chyme, which is necessary for the optimal activity of pancreatic enzymes and to neutralize the acidic chyme coming from the stomach.

(N/A) Bile juice is produced by the liver and stored in the gall bladder. It is released into the duodenum to aid in digestion.
The composition of bile juice includes:
$1$. Bile pigments: Bilirubin and biliverdin (breakdown products of hemoglobin).
$2$. Bile salts: Sodium glycocholate and sodium taurocholate,which are essential for the emulsification of fats.
$3$. Cholesterol: $A$ lipid component.
$4$. Phospholipids: Such as lecithin.
$5$. Water and electrolytes: Bile juice does not contain any digestive enzymes.
Function: Bile salts help in the emulsification of fats,which involves breaking down large fat globules into smaller micelles,thereby increasing the surface area for the action of the enzyme lipase.

(B) The liver is the largest accessory digestive gland in the human body.
Its primary functions include the secretion of bile,which is essential for the emulsification of fats.
It also plays a crucial role in detoxification,where it converts toxic waste products into less harmful substances for excretion.
Additionally,it is involved in the metabolism of carbohydrates,proteins,and fats,and the storage of glycogen,vitamins,and minerals.

(A) The mucosa of the stomach contains gastric glands. Gastric glands consist of three major types of cells:
$(1)$ Mucous neck cells: These cells secrete mucus,which protects the stomach lining from the acidic environment.
$(2)$ Peptic or Chief cells: These cells secrete the proenzyme pepsinogen,which is converted into active pepsin for protein digestion.
$(3)$ Parietal or Oxyntic cells: These cells secrete $HCl$ (hydrochloric acid) and the intrinsic factor,which is essential for the absorption of vitamin $B_{12}$.

(N/A)

Liver	Pancreas
$(1)$ It is the largest accessory digestive gland in the body.	$(1)$ It is a soft,light pink-colored gland that functions as both an endocrine and an exocrine gland.
$(2)$ It is located in the upper right portion of the abdominal cavity.	$(2)$ It is located in the loop of the $U$-shaped duodenum.
$(3)$ It secretes bile juice.	$(3)$ It secretes pancreatic juice.
$(4)$ Bile pigments,excretory substances,and organic-inorganic salts are present in its bile juice.	$(4)$ It secretes digestive enzymes and hormones (insulin and glucagon).
$(5)$ It does not contain digestive enzymes; bile helps in the emulsification of fats.	$(5)$ Enzymes take part in the digestion of carbohydrates,proteins,and fats. Hormones maintain blood glucose levels.

(N/A) $(1)$ The Islets of Langerhans located in the pancreas secrete hormones like Glucagon and Insulin. These hormones are transported by the blood to their target organs,making it a ductless endocrine gland. Simultaneously,the pancreas secretes pancreatic juice containing various digestive enzymes,which is transported to the duodenum via the pancreatic duct. Thus,it functions as an exocrine gland.
$(2)$ The liver secretes bile juice,which contains inorganic salts like $Na_{2}CO_{3}$ and $NaHCO_{3}$. These salts provide an alkaline medium in the duodenum,which is essential for the activation of pancreatic enzymes. Additionally,bile juice contains organic salts like sodium taurocholate and sodium glycocholate,which help in the emulsification and digestion of fats. Therefore,although the liver does not secrete digestive enzymes,it plays a crucial role in digestion,making it an important accessory digestive gland.

(A) The gall bladder is a small,sac-like structure located on the posterior surface of the right lobe of the liver.
Its primary function is to store and concentrate the bile juice secreted by the liver until it is needed for the digestion of fats in the small intestine.

(N/A) The pancreas is a compound (both exocrine and endocrine) elongated organ situated between the limbs of the '$C$'-shaped duodenum.
$1$. Exocrine function: The exocrine portion secretes an alkaline pancreatic juice containing enzymes.
$2$. Major secretions helpful in digestion include:
- Trypsinogen and Chymotrypsinogen: Inactive enzymes that are activated to digest proteins.
- Procarboxypeptidase: Activated to digest proteins.
- Pancreatic Amylase: Breaks down carbohydrates into disaccharides.
- Pancreatic Lipases: Break down fats into fatty acids and glycerol.
- Nucleases: Break down nucleic acids into nucleotides.

(N/A) The gall bladder is a small,sac-like structure connected to the liver that stores and concentrates bile secreted by the liver.
Its primary role is to release concentrated bile into the small intestine during digestion to emulsify fats.
If the gall bladder stops functioning or is removed (cholecystectomy),bile is no longer stored or concentrated; instead,it flows continuously into the intestine.
While the body gradually adapts to this continuous flow,the bile becomes less effective at emulsifying large amounts of fat.
Consequently,individuals who have had their gall bladder removed are advised to follow a low-fat diet to avoid digestive discomfort,as the efficiency of fat digestion is significantly reduced.

(A) Renin is a proteolytic enzyme found in the gastric juice of infants.
It helps in the digestion of milk proteins (casein) into paracasein.
As a person grows into an adult,the secretion of renin decreases significantly or stops,as the digestive system matures.

(B) The pancreatic juice and bile are released into the duodenum of the small intestine through the hepato-pancreatic duct. This duct is guarded by the sphincter of Oddi,which regulates the flow of these secretions.

(N/A) $(1)$ Goblet cells: Secrete mucus.
$(2)$ Peptic or chief cells (Zymogenic cells): Secrete proenzymes pepsinogen and prorenin.
$(3)$ Oxyntic or parietal cells: Secrete hydrochloric acid $(HCl)$ and Castle's intrinsic factor.

(A) $(1)$ The enzyme present in saliva is salivary amylase,also known as Ptyalin,which acts on starch to convert it into maltose. Steapsin is a lipase found in pancreatic juice.
$(2)$ Gastric glands contain Oxyntic cells (also called Parietal cells),which secrete $HCl$ and Castle's intrinsic factor. Peptic cells (also called Chief cells) secrete proenzymes like pepsinogen.

(N/A) The main salivary glands are of three types:
$(i)$ Parotid gland
$(ii)$ Submandibular gland
$(iii)$ Sublingual gland

(D) The correct answer is option $D$ because parietal or oxyntic cells secrete $HCl$ and intrinsic factor,which is essential for the absorption of vitamin $B_{12}$.
Peptic or chief cells secrete the proenzyme pepsinogen.
Goblet cells secrete mucus.
Hepatic cells secrete bile.

(A) Goblet cells are specialized glandular epithelial cells found in the lining of the respiratory and digestive tracts.
Their primary function is to synthesize and secrete mucus,which acts as a lubricant and protective barrier for the underlying tissues.

(D) In rabbits,there are four pairs of salivary glands present:
$1.$ Sublingual glands
$2.$ Infra-orbital glands
$3.$ Parotid glands
$4.$ Sub-maxillary glands
Therefore,the total number of types of salivary glands is four.

(D) Saliva contains the enzyme salivary amylase,which is also known as $Ptyalin$.
It is responsible for the initial breakdown of starch into maltose in the oral cavity.

(B) The secretion of salivary glands is called saliva.
The medium of saliva is slightly acidic.
The quantity of saliva produced in an adult is $1000-1500 \; mL$ per day.
Chemically,saliva is a mixture of water and electrolytes $(Na^+, K^+, Cl^-, HCO_3^-)$.
Additionally,enzymes like salivary amylase (ptyalin) and lysozyme (an anti-bacterial agent) are also found in saliva,along with mucus which helps in lubricating the food.

(A) The fluid secreted by the salivary glands is known as saliva.
Saliva is chemically a mixture of water,electrolytes (salts of sodium,potassium,chloride,and bicarbonates),salivary amylase (ptyalin),and lysozyme.
Lysozyme is an enzyme that functions as an antibacterial agent by breaking down the cell walls of bacteria,thereby preventing infections in the oral cavity.

(C) In humans,there are three pairs of salivary glands responsible for the secretion of saliva: the parotid glands,the sublingual glands,and the submaxillary (or submandibular) glands.
$Supra$ $optic$ refers to a region in the hypothalamus,which is involved in neuroendocrine functions and is not a salivary gland.
Therefore,the $Supra$ $optic$ region is not associated with the secretion of saliva.

(C) Oxyntic cells,also known as parietal cells,are present in the gastric glands of the stomach wall.
They are responsible for the secretion of hydrochloric acid $(HCl)$ and intrinsic factor.
$HCl$ maintains a low $pH$ (approximately $1.8$ to $2.0$) in the stomach,which is essential for the activation of proenzymes like pepsinogen into pepsin and prorennin into rennin.

(A) The human liver is anatomically divided into $2$ main lobes,the left and the right lobe. These lobes are further subdivided into $8$ segments,which are composed of thousands of hepatic lobules,the functional units of the liver.

(D) The liver secretes bile,which is stored in the gall bladder. Bile contains bile salts such as sodium glycocholate and sodium taurocholate. These salts help in the digestion of fats in the small intestine by bringing about the emulsification of fat,which is the conversion of large fat droplets into small ones.

(A) Saliva,the secretion of salivary glands in humans,consists of a mixture of water,salts,and electrolytes.
Its medium is slightly acidic with a $pH$ of $6.8$.
Saliva also contains an antibacterial agent known as lysozyme.

(A) Kupffer's cells are specialized macrophages located in the liver sinusoids.
They play a crucial role in the body's immune system by performing phagocytosis,which involves engulfing and destroying foreign particles,bacteria,and damaged red blood cells.
Therefore,they are classified as phagocytic cells.

(D) Glisson's capsule is a thin layer of connective tissue that surrounds the liver and ensheathes the hepatic artery,portal vein,and bile ducts within the liver.
It was named after the British physician and biologist Francis Glisson $(1597-1677)$.
Therefore,Glisson's capsules are a characteristic feature of the mammalian liver.

(B) Succus entericus,also known as intestinal juice,is the collective secretion of the intestinal glands.
These glands include the crypts of Lieberkühn,which are located between the bases of the villi in the small intestine.
The crypts of Lieberkühn secrete enzymes and mucus that facilitate the final stages of digestion.
Therefore,succus entericus is primarily considered the secretion of the crypts of Lieberkühn.

(B) To determine which secretion has the highest $pH$,we compare the typical $pH$ values of the digestive juices:

Digestive juice	$pH$ Range
Gastric juice	$1.5 - 3.5$
Bile	$7.6 - 8.6$
Pancreatic juice	$7.5 - 8.3$
Intestinal juice	$7.5 - 8.0$

Based on the physiological ranges,Bile typically exhibits the highest $pH$ value (often reaching up to $8.6$),making it the most alkaline among the options provided.

(C) The pancreas is a yellowish,leaf-like mixed gland located posterior to the stomach in the abdominal cavity.
It consists of two parts: an exocrine part and an endocrine part.
The exocrine part secretes a slightly alkaline fluid known as pancreatic juice.
Pancreatic juice contains sodium bicarbonate and three main proenzymes: $Trypsinogen$,$Chymotrypsinogen$,and $Procarboxypeptidase$.
These proenzymes are inactive precursors that are activated in the small intestine to aid in protein digestion.

(A) The correct match is: Pepsinogen - Zymogenic cells.
Detailed analysis of the options:
$1$. Pepsinogen is secreted by the Zymogenic (or Chief) cells of the stomach.
$2$. $HCl$ (Hydrochloric acid) is secreted by the Oxyntic (or Parietal) cells of the stomach.
$3$. Mucus is secreted by the Goblet cells.
$4$. Pancreatic juice is secreted by the Acinar cells of the pancreas,not by the salivary glands.
Therefore,option $A$ is the only correctly matched pair.

(B) All the given statements are scientifically correct.
$I.$ Bile salts (glycocholate and taurocholate) emulsify fats in the small intestine,increasing the surface area for lipase action.
$II.$ Bile salts are indeed the sodium and potassium salts of glycocholic and taurocholic acids.
$III.$ Hepatic bile is alkaline ($pH$ $8.6$),but as it is stored and concentrated in the gall bladder,its $pH$ drops to $7.6$ or $7.5$.
$IV.$ The pathway of bile is: Liver $\rightarrow$ Hepatic ducts $\rightarrow$ Common bile duct $\rightarrow$ Hepatopancreatic ampulla (Ampulla of Vater) $\rightarrow$ Duodenum (first part of small intestine).
$V.$ Certain animals like rats and horses lack a gall bladder; they secrete bile directly into the intestine.

(B) There are three pairs of salivary glands in humans:
$(1)$ Parotid glands $(1 \; \text{pair})$
$(2)$ Sub-maxillary or sub-mandibular glands $(1 \; \text{pair})$
$(3)$ Sub-lingual glands $(1 \; \text{pair})$
These glands are situated just outside the buccal cavity and secrete salivary juice into the buccal cavity.

(A) Glisson's capsule is a thin connective tissue sheath that covers the hepatic lobules of the liver. It is composed of dense irregular connective tissue and is essential for maintaining the structural integrity of the liver lobules.

(D) The gall bladder is a small,pear-shaped organ located under the liver.
It serves as a storage site for bile produced by the liver.
While stored in the gall bladder,bile is concentrated through the absorption of water and certain electrolytes from the fluid.

(A) The liver is the largest gland of the human body.
It is located in the upper right portion of the abdominal cavity.
In an adult human,it weighs approximately $1.2$ to $1.5 \;kg$.

(C) $Maltose$ is a disaccharide sugar.
$Salivary \text{ } amylase$ is an enzyme that helps in the digestion of carbohydrates.
$Lysozyme$ is an antibacterial enzyme present in saliva that prevents infections by breaking down the cell walls of bacteria.
$Pepsinogen$ is the inactive precursor of pepsin, which helps in the digestion of proteins in the stomach.

(A) The stomach lining contains various types of cells that perform specific secretory functions:
$1$. Oxyntic cells (also known as parietal cells): These cells are responsible for secreting $HCl$ (hydrochloric acid) and the intrinsic factor,which is essential for the absorption of vitamin $B_{12}$.
$2$. Peptic cells (also known as chief cells): These cells secrete the proenzyme pepsinogen.
$3$. Mucus neck cells: These cells secrete mucus,which protects the stomach lining from the corrosive action of $HCl$.

(C) Bile juice does not contain any digestive enzymes. It consists of bile pigments ($bilirubin$ and $biliverdin$),bile salts ($sodium$ $bicarbonate$,$sodium$ $glycocholate$,$sodium$ $taurocholate$),$cholesterol$,and phospholipids. Its primary function is the emulsification of fats.

(C) $Trypsinogen$ is an inactive zymogen (proenzyme) secreted by the pancreas. It is a key component of pancreatic juice. Once it reaches the small intestine,it is activated into $Trypsin$ by the enzyme $Enterokinase$,which is secreted by the intestinal mucosa.

(D) The correct matches are as follows:
$a.$ Parotid glands are located near the cheek.
$b.$ Sub-maxillary or sub-mandibular glands are located at the lower jaw.
$c.$ Sub-lingual glands are located below the tongue.
Therefore, the correct sequence is $a(iii), b(ii), c(i)$.

(C) Peptic cells or chief cells secrete pepsinogen.
Parietal cells or oxyntic cells secrete $HCl$ and intrinsic factor,which is essential for the absorption of Vitamin $B_{12}$.

(A) Pancreatic juice contains inactive enzymes like $Trypsinogen$,$Chymotrypsinogen$,and $Procarboxypeptidase$.
$Pepsinogen$ is an inactive enzyme secreted by the chief cells (or peptic cells) of the gastric glands located in the stomach,not by the pancreas.

(C) The correct answer is $C$. Rennin is a proteolytic enzyme found in the gastric juice of infants,not in the pancreatic juice. It is responsible for the digestion of milk protein (casein).

(C) Aptyalism is a condition characterized by the absence of saliva production.
Saliva contains lysozyme,which possesses anti-microbial properties and helps prevent dental caries.
Therefore,in the absence of saliva,the risk of dental caries increases significantly.
Thus,the Assertion is correct.
However,the Reason is incorrect because the parasympathetic nervous system actually stimulates salivary secretion,whereas aptyalism is typically caused by damage to salivary glands or other pathological conditions,not by the parasympathetic nervous system itself.

(C) The duct of Wirsung (main pancreatic duct) carries pancreatic juice (digestive enzymes) to the duodenum,which is an exocrine function.
Therefore,the assertion is correct as it describes the anatomical path of the pancreatic duct.
However,the reason is incorrect because the endocrine function of the pancreas (secretion of hormones like insulin and glucagon) occurs directly into the blood,not through the duct of Wirsung.
Blockage of the duct of Wirsung only affects the exocrine function (digestion),not the endocrine function.

(A) Trypsinogen is the inactive precursor (zymogen) of the enzyme trypsin.
Pancreatic enzymes are secreted in their inactive forms (zymogens) to prevent the digestion of the pancreatic tissue itself,a process known as autodigestion.
Therefore,the secretion of trypsin as trypsinogen is a protective mechanism for the pancreas.
Thus,both the Assertion and the Reason are correct,and the Reason is the correct explanation of the Assertion.

(A) The liver is the largest digestive gland in the human body. It plays a crucial role in digestion by producing bile,which helps in the emulsification of fats.

(B) The gall bladder is not involved in the production of bile.
Bile is synthesized and secreted by the hepatocytes (liver cells).
The gall bladder serves only to store and concentrate the bile until it is required for the digestion of fats in the small intestine.