Human Respiratory System Questions in English

(N/A) The lungs are a pair of cone-shaped organs located in the thoracic cavity. They are situated on either side of the heart and are protected by the rib cage. The diaphragm is located below the lungs,forming the floor of the thoracic cavity.

(B) The space between the two pleural membranes is filled with pleural fluid.
This fluid acts as a lubricant,which reduces friction on the lung surface during breathing movements.
Additionally,it protects the lungs against mechanical shocks.

(N/A) The lungs are covered by a double-layered membrane known as the pleura,with pleural fluid present between these two layers.
Its primary function is to reduce friction on the lung surface during breathing movements.

(B) The ciliated epithelium in the trachea consists of cells with hair-like projections called cilia. The coordinated rhythmic movements of these cilia help in trapping and moving dust particles,mucus,and other foreign substances inhaled with atmospheric air out of the respiratory tract,thereby keeping the airways clean.

(C) Columnar or cuboidal epithelial cells that bear cilia on their free surface are called ciliated epithelium.
The cilia remain in rhythmic motion and create a current to transport materials that come in contact with them.
In the respiratory tract,this movement helps in expelling mucus and trapped dust particles towards the outside.

(A) Sunflower is a dicot plant. In the guard cells of dicot plants,the outer wall (away from the stomatal pore) is thin and elastic,while the inner wall (towards the stomatal pore) is thick and inelastic. This structural difference allows the guard cells to bulge outwards when turgid,thereby opening the stomatal pore.

(D) The pharynx is a common passage for both food and air. The lower part of the pharynx leads to the esophagus (food pipe) posteriorly and the larynx (voice box) anteriorly.
The opening of the larynx is known as the glottis.
$A$ thin,leaf-like cartilaginous flap called the epiglottis is present at the opening of the glottis.
During the act of swallowing (deglutition),the epiglottis closes the glottis to prevent the entry of food particles into the windpipe,ensuring they pass into the esophagus.

(B) The pharynx is a muscular tube that acts as a common passage for both food and air. It is divided into three parts: the nasopharynx,the oropharynx,and the laryngopharynx. The oropharynx serves as a common pathway for both food and air,as it connects the oral cavity to the oesophagus and the larynx.

(B) The $Pharynx$ is a common passage for both food and air.
$Oesophagus$: It is the food pipe that carries food to the stomach.
$Trachea$: It is the windpipe that carries air to the lungs.
$Glottis$: It is the opening of the larynx,which remains covered by the epiglottis during swallowing to prevent food from entering the windpipe.

(D) The conducting part of the human respiratory system includes the external nostrils,nasal passage,pharynx,larynx,trachea,bronchi,and bronchioles. Its primary functions are to transport atmospheric air to the alveoli,clear it of foreign particles,humidify it,and bring it to body temperature. The exchange part consists of the alveoli and their ducts,which are the actual sites of $O_2$ and $CO_2$ diffusion between blood and atmospheric air. Since all the statements provided ($A$,$B$,and $C$) are scientifically correct,the false statement is none of the above.

(C) The $Larynx$,also known as the sound box,is a cartilaginous structure located in the neck.
It is positioned superiorly to the trachea and inferiorly to the pharynx (specifically,it is guarded by the epiglottis).
Therefore,the $Larynx$ is situated between the epiglottis and the trachea.

(A) Humans have two lungs,which are covered by a double membrane called the pleura,with pleural fluid present between them.
This pleural fluid acts as a lubricant and reduces the friction on the lung surface during breathing movements.
The outer pleural membrane is in close contact with the thoracic lining,whereas the inner pleural membrane is in contact with the lung surface.

(B) The lungs are situated in the thoracic chamber and are protected by a double-layered membrane known as the pleura. The outer pleural membrane is in close contact with the thoracic lining,while the inner pleural membrane is in contact with the lung surface. Between these two membranes lies the pleural fluid,which reduces friction on the lung surface.

(D) The air passage in humans follows a specific anatomical sequence:
$1$. External nostrils: Air enters through these openings.
$2$. Nasal passage: Leads from the nostrils to the internal nares.
$3$. Pharynx: The common passage for air and food.
$4$. Larynx: The voice box,which leads to the trachea.
$5$. Trachea: $A$ straight tube extending up to the mid-thoracic cavity.
$6$. Bronchi: The trachea divides into right and left primary bronchi.
$7$. Bronchioles: Bronchi undergo repeated divisions to form secondary,tertiary bronchi,and finally bronchioles.
$8$. Alveoli: The terminal bronchioles end in thin,irregular-walled,vascularized,bag-like structures called alveoli,where gas exchange occurs.
Therefore,the correct sequence is: External nostril $\rightarrow$ Nasal passage $\rightarrow$ Internal nostril $\rightarrow$ Pharynx $\rightarrow$ Larynx $\rightarrow$ Trachea $\rightarrow$ Bronchi $\rightarrow$ Bronchioles $\rightarrow$ Alveoli.

(A) The $Larynx$ is a cartilaginous box that helps in sound production and is therefore called the sound box.
Until puberty, there is little difference in the size of the $Larynx$ in males and females.
Thereafter, it grows larger and becomes prominent in males, which is why it is called $Adam's$ $apple$ in men.
It is the upper part of the respiratory tract located in the neck region.

(D) Humans have two lungs,which are covered by a double-layered pleura with pleural fluid between them.
Pleural fluid reduces the friction on the lung surface.
The outer pleural membrane is in close contact with the thoracic lining,whereas the inner pleural membrane is in contact with the lung surface.
Therefore,the structure described by all these features is the pleura.

(D) The human respiratory system follows a branching pattern that decreases in diameter as it progresses deeper into the lungs.
$1$. The $Trachea$ is the largest airway, which divides into the right and left primary bronchi.
$2$. The $Primary \text{ } bronchi$ further divide into secondary and tertiary bronchi, and then into bronchioles.
$3$. The $Respiratory \text{ } bronchiole$ is the final part of the conducting system before the alveolar ducts and alveoli, and it possesses the smallest diameter among the given options.
Therefore, the correct answer is $D$.

(C) The correct answer is $C$.
$Vocal$ $cords$ are two pairs of folds of mucous membrane that extend into the lumen from the sides of the larynx.
These cords vibrate when air passes through them,which is responsible for the production of sound during respiration.

(B) The larynx,also known as the sound box,is a cartilaginous structure located at the top of the trachea. It contains the vocal cords,which vibrate to produce sound as air passes through them during expiration.

(A) The trachea is a straight tube extending up to the mid-thoracic cavity.
It divides at the level of the $5th$ thoracic vertebra into the right and left primary bronchi.
Each bronchus undergoes repeated divisions to form secondary and tertiary bronchi,eventually ending in very thin terminal bronchioles.

(D) The trachea,also known as the windpipe,is a tube that connects the larynx to the bronchi. It is characterized by the presence of $16-20$ $C$-shaped rings of hyaline cartilage,which prevent the airway from collapsing. The inner lining of the trachea consists of ciliated,pseudostratified columnar epithelium,which helps in trapping and moving dust particles and mucus out of the respiratory tract. Therefore,the correct answer is Trachea.

(B) The nasal cavity is the first part of the respiratory system. It opens to the exterior through nostrils.
Small hairs present in the cavity help to filter dust particles and other foreign matter.
The air in the nasal cavity gets warmed because the nasal cavity has a very rich blood supply.
This process ensures that the air is warmed and moistened before it enters the lungs.

(C) Bronchioles are formed by the branching of tertiary bronchi.
Bronchioles further divide into terminal bronchioles and respiratory bronchioles.
Unlike bronchi,bronchioles are characterized by the absence of cartilaginous rings.

(A) Air entering the lungs is warm and filtered.
Nasal Cavity: It is the first part of the respiratory system. It opens to the exterior through nostrils. The small hairs present in the cavity help to filter the particles of dust and other foreign matter. The air in the nasal cavity gets warmed (because the nasal cavity has a very good blood supply) and moistened before it enters the lungs.

(C) The human respiratory system is designed to maximize the surface area for gas exchange.
While the bronchioles themselves are conducting airways,the question refers to the total respiratory surface area provided by the millions of alveoli in the lungs.
Scientific estimates place the total surface area of the human lungs at approximately $80$ to $100\; m^{2}$ when fully expanded.
Therefore,$100\; m^{2}$ is the most accurate approximation among the given options.

(C) The $Diaphragm$ is a characteristic feature of mammals.
It is a highly muscular and fibrous partition that is elevated towards the thorax in a dome-like shape.
Its primary function is to assist in the process of respiration by changing the volume of the thoracic cavity.
It acts as a physical barrier that separates the thoracic cavity from the abdominal cavity.
It is also known as the phrenic muscle.

(B) $1$. During swallowing,the glottis is covered by a thin,elastic,cartilaginous flap known as the epiglottis $(A)$ to prevent food from entering the larynx.
$2$. The trachea is a straight tube that extends up to the mid-thoracic $(B)$ cavity.
$3$. The trachea divides at the level of the $5^{th}$ thoracic vertebra into right and left primary bronchi $(C)$.

(A) The trachea is a straight tube extending up to the mid-thoracic cavity. It is supported by '$C$'-shaped rings of hyaline cartilage,which prevent the trachea from collapsing.
Option '$A$' is correct because the tracheal rings are indeed composed of hyaline cartilage.
Option '$B$' is incorrect because the dorsal side of the thoracic chamber is formed by the vertebral column,while the sternum forms the ventral side.
Option '$C$' is incorrect because expiration occurs when the intra-pulmonary pressure is higher than the atmospheric pressure.
Option '$D$' is incorrect because inspiration occurs when the intra-pulmonary pressure is less than the atmospheric pressure (negative pressure).

(A) The respiratory system is most well-developed in mammals among the given options.
Mammals possess a complex respiratory system consisting of a pair of lungs with a large surface area,facilitated by the presence of alveoli,which allows for efficient gas exchange to meet their high metabolic demands.
In contrast,invertebrates often rely on simple diffusion or tracheal systems,hemichordates use gills or body surfaces,and amphibians have less efficient lungs supplemented by cutaneous respiration.

(B) $(1)$ Mucus secreted by goblet cells and glands makes the surface sticky,which helps in trapping dust particles present in the inspired air.
$(2)$ Moisture from the epithelium adds humidity to the air.
$(3)$ The nasal chamber helps in bringing the temperature of the incoming air to the body temperature.

(C) The $Epiglottis$ is a thin,elastic,cartilaginous flap located at the entrance of the larynx.
During the act of swallowing,the $Epiglottis$ moves to cover the $Glottis$ (the opening of the windpipe),thereby preventing food particles from entering the respiratory tract and ensuring they pass into the esophagus.

(B) The trachea is a straight tube extending up to the mid-thoracic cavity.
It divides at the level of the $5^{\text{th}}$ thoracic vertebra into right and left primary bronchi.

(D) The trachea is a straight tube extending up to the mid-thoracic cavity,which divides at the level of the $5^{\text{th}}$ thoracic vertebra into a right and left primary bronchus.

(C) The lungs are enclosed in a double-layered membrane known as the $Pleura$.
$Pericardium$ is the protective membrane that covers the heart.
$Renal$ $capsule$ is the tough fibrous layer surrounding the kidney.
$Epineurium$ is the outermost layer of connective tissue that surrounds a peripheral nerve.
Therefore,the correct answer is $Pleura$.

(B) Humans possess a pair of lungs that are situated within an air-tight chamber known as the thoracic cavity or chest cavity.

(B) In humans,the respiratory system begins with a pair of external nostrils. These nostrils are located above the upper lips and serve as the entry point for air into the nasal cavity. Therefore,the correct option is $B$.

(A) The alveolar membrane is very thin,irregular,and richly supplied with blood vessels (highly vascularized).
This structure facilitates the rapid and efficient exchange of gases between the air in the alveoli and the blood in the capillaries.

(C) The thoracic chamber is an airtight chamber formed as follows:
$1$. Dorsally: By the vertebral column.
$2$. Ventrally: By the sternum.
$3$. Laterally: By the ribs.
$4$. On the lower side: By the dome-shaped diaphragm.
Therefore,ventrally it is formed by the sternum and laterally it is formed by the ribs.

(C) The thoracic cavity is closed at the bottom by the diaphragm.
It is a dome-shaped muscular structure that separates the thoracic cavity from the abdominal cavity,which contains most of the digestive organs.

(D) The Adam's apple refers to the laryngeal prominence formed by the thyroid cartilage of the larynx.
It is composed of hyaline cartilage.
It is typically more prominent in adult males due to the influence of testosterone during puberty,which causes the larynx to grow larger and the thyroid cartilage to tilt at a sharper angle.

(C) The $Cricoid$ cartilage has a signet ring-like structure that lies below the $Thyroid$ cartilage. It is composed of $hyaline$ cartilage and forms the lower part of the larynx.

(B) The human lungs contain a vast network of air sacs known as alveoli,which are the primary sites for gas exchange.
Scientific estimates indicate that there are approximately $300$ million alveoli in the human lungs,providing a massive surface area for the diffusion of oxygen and carbon dioxide.

(C) The human right lung is divided into three lobes (superior,middle,and inferior) by two fissures: the oblique fissure and the horizontal fissure. The human left lung is divided into two lobes (superior and inferior) by a single oblique fissure. Therefore,the oblique fissure is present in both lungs.

(B) In birds,the larynx does not possess vocal cords. The syrinx is the specialized organ that produces sound and is located at the bifurcation of the trachea and the bronchi.

(B) The $Pharynx$ is a muscular tube that serves as a common passage for both air and food.
It connects the nasal cavity and the oral cavity to the larynx and the oesophagus,respectively.
Therefore,it acts as a shared organ for both the digestive and respiratory systems.

(D) The abdominal cavity is the space that holds the majority of the digestive organs,including the stomach,small intestine,and large intestine.
The oesophagus is a muscular tube that connects the pharynx to the stomach.
It passes through the neck and the thoracic cavity (chest cavity) before entering the abdominal cavity through the diaphragm.
Therefore,the oesophagus is primarily located in the thoracic cavity,not the abdominal cavity.

(D) Mammals possess the most developed respiratory system among vertebrates.
They utilize a highly efficient diaphragm-driven ventilation mechanism,which allows for a large surface area for gas exchange within the lungs (alveoli).
While birds have a very efficient system with air sacs,mammals are generally considered to have the most complex and highly developed respiratory structures for maintaining high metabolic rates.

(A) In the standard diagram of the human respiratory system:
$P$ represents the $Larynx$ (voice box), which is located at the top of the trachea.
$Q$ represents the $Diaphragm$, which is a dome-shaped muscular partition separating the thorax from the abdomen and plays a crucial role in breathing.
Therefore, the correct identification is $P = \text{Larynx}$ and $Q = \text{Diaphragm}$.

(B) The correct pathway of air in the human respiratory system is as follows:
$1$. External nostrils (entry point).
$2$. Nasal cavity.
$3$. Internal nostrils (nasopharynx region).
$4$. Pharynx (common passage for food and air).
$5$. Larynx (sound box,which leads to the trachea).
$6$. Trachea (windpipe).
$7$. Primary bronchi.
$8$. Secondary bronchi.
$9$. Tertiary bronchi.
$10$. Terminal bronchiole.
$11$. Alveoli (site of gas exchange).
Therefore,the sequence in option $B$ is correct.

(D) The trachea (windpipe) is a straight tube extending up to the mid-thoracic cavity.
It divides at the level of the $5$th thoracic vertebra into a right and left primary bronchi.
Therefore,all the given statements are correct.