Human Respiratory System Questions in English

(A) During the process of swallowing (deglutition),a cartilaginous flap called the $epiglottis$ prevents the entry of food into the $glottis$ (the opening of the windpipe or trachea).
When food is swallowed,the larynx moves upward,causing the $epiglottis$ to fold down and cover the $glottis$ like a lid.
This mechanism ensures that the food bolus is directed into the esophagus instead of the respiratory tract.

(B) The deoxygenated blood is pumped from the $Right$ ventricle into the pulmonary artery.
This artery then divides into two branches that carry the deoxygenated blood to the lungs for oxygenation.

(A) Turbinal bones,also known as nasal conchae,are thin,scroll-like bony elements located within the nasal cavity (nasal passage). Their primary function is to increase the surface area of the nasal cavity,which helps in warming,humidifying,and filtering the inhaled air before it reaches the lungs.

(A) The nasal cavity and the buccal cavity (oral cavity) are separated by a structure called the palate. The anterior portion of the palate is bony and is known as the hard palate,which is formed by the maxilla and palatine bones. The posterior portion is the soft palate,which is muscular. Since the question specifically asks for the bone that separates these cavities,the hard palate (part of the palate complex) is the correct anatomical answer.

(C) The $Larynx$ (voice box) is a cartilaginous structure located in the neck.
It consists of several cartilages,including the thyroid,cricoid,epiglottis,and a pair of arytenoid cartilages.
The arytenoid cartilages are small,pyramid-shaped structures that play a crucial role in the movement of the vocal cords.

(B) . Intercostal muscles are located between the ribs in the thoracic cavity.
They play a crucial role in the process of respiration.
These muscles move the sternum and ribs inwards and outwards,which changes the volume and pressure within the thoracic cavity,facilitating the movement of air into and out of the lungs.

(B) The $Phrenic$ nerve is a motor nerve that originates from the cervical spinal nerves $(C3, C4, C5)$ and provides the primary motor supply to the diaphragm,which is the principal muscle of respiration.
It is essential for the contraction of the diaphragm during the process of breathing.

(B) The nasal cavity is lined with a respiratory mucosa that contains a large number of ciliated cells and goblet cells.
Ciliated cells are responsible for moving mucus and trapped particles toward the pharynx to be swallowed or expectorated.
Goblet cells secrete mucus,which traps dust,pathogens,and other foreign particles entering through the air.
Among the given options,ciliated cells are a primary structural feature of the nasal epithelium that facilitates the cleaning of inhaled air.

(B) The oral cavity and the nasal cavity are separated by a bony and muscular structure known as the $Palate$.
The $Palate$ forms the roof of the oral cavity and the floor of the nasal cavity,allowing for simultaneous breathing and chewing.

(A) The $Pharynx$ is a muscular tube that acts as a common passage for both food and air.
It is divided into three parts: $Nasopharynx$,$Oropharynx$,and $Laryngopharynx$.
Food enters the $Oesophagus$ from the $Pharynx$,while air enters the $Larynx$ (voice box) from the $Pharynx$.
Therefore,the $Pharynx$ is the shared pathway for the digestive and respiratory systems.

(C) The $Epiglottis$ is a thin,cartilaginous flap located at the entrance of the larynx.
During the process of swallowing (deglutition),the $Epiglottis$ moves to cover the glottis (the opening of the windpipe or trachea).
This action prevents the food bolus from entering the respiratory tract and ensures it passes into the esophagus instead.

(D) In cockroaches,spiracles are small openings on the lateral side of the body that allow air to enter the tracheal system for respiration.
In humans,nostrils (external nares) are the external openings that allow air to enter the respiratory tract.
Therefore,nostrils are the functional equivalent (analogous) to the spiracles of a cockroach as they serve as the entry point for air.

(B) The trachea,primary,secondary,and tertiary bronchi,and initial bronchioles are supported by incomplete cartilaginous rings. These rings prevent the airways from collapsing when the air pressure inside them decreases,ensuring that the respiratory passage remains open for the exchange of gases.

(D) The human respiratory system is divided into two parts: the conducting part and the respiratory or exchange part.
$1$. The conducting part includes the external nostrils,nasal passage,pharynx,larynx,trachea,bronchi,and bronchioles.
$2$. The primary functions of the conducting part are to transport atmospheric air to the alveoli,clear it of foreign particles,humidify it,and bring the air to body temperature.
$3$. Therefore,all the given options are correct functions of the conducting part.

(D) The pulmonary alveoli are the primary sites of gaseous exchange in the lungs.
To facilitate efficient diffusion of gases ($O_2$ and $CO_2$),the wall of the alveoli must be extremely thin.
Squamous epithelium consists of a single layer of flattened cells with irregular boundaries.
This tissue is commonly found in the walls of blood vessels and air sacs (alveoli) of lungs,where it forms a delicate lining for diffusion.

(A) The trachea is supported by $C$-shaped cartilaginous rings. These rings are incomplete at the dorsal surface,which is the side facing the esophagus. This structural arrangement allows the esophagus to expand during the passage of food.

(C) The pathway of air during respiration in the human respiratory system is as follows:
$1$. External nostrils: Air enters through the nostrils.
$2$. Pharynx: The common passage for air and food.
$3$. Larynx: The sound box.
$4$. Trachea: The windpipe.
$5$. Bronchi: The primary tubes entering the lungs.
$6$. Bronchioles: The smaller branches of the bronchi.
$7$. Alveoli: The site of gaseous exchange.
Therefore,the correct sequence is: External nostrils $\rightarrow$ Pharynx $\rightarrow$ Larynx $\rightarrow$ Trachea $\rightarrow$ Bronchi $\rightarrow$ Bronchioles $\rightarrow$ Alveoli.

(A) The respiratory tract is lined with ciliated epithelium. The cilia perform a rhythmic beating motion that helps in moving the mucus,along with trapped dust particles and pathogens,towards the pharynx (throat) so that it can be swallowed or coughed out. This process is essential for keeping the airways clean and preventing infections.

(C) The lungs are protected by a double-layered membrane called the $Pleural$ $membrane$ (or $Pleura$).
$1$. The outer pleural membrane is in close contact with the thoracic lining.
$2$. The inner pleural membrane is in contact with the lung surface.
$3$. The space between these two membranes is called the $Pleural$ $cavity$, which is filled with $Pleural$ $fluid$ to reduce friction during breathing.
$4$. $Peritoneum$ covers the abdominal organs, $Pericardium$ covers the heart, and $Glisson's$ $capsule$ covers the liver.

(B) In humans,the $Larynx$ (also known as the sound box) is a cartilaginous structure located at the top of the trachea. It contains vocal cords that vibrate when air passes through them,thereby producing sound. Therefore,the correct option is $B$.

(D) The $Epiglottis$ is a thin, leaf-shaped cartilaginous flap located at the entrance of the larynx. During the act of swallowing, the $Epiglottis$ folds down to cover the $Glottis$ (the opening of the windpipe), thereby preventing food and liquid from entering the respiratory tract and directing them into the esophagus.

(A) In the human respiratory system,air enters through the nostrils and travels through the trachea,bronchi,and bronchioles to reach the alveoli. The alveoli are the primary sites of gaseous exchange where oxygen enters the blood and carbon dioxide is removed. Therefore,oxygen finally reaches the alveoli.

(A) The respiratory system consists of a branching network of tubes.
$1$. The $Trachea$ (windpipe) divides into two primary $Bronchi$.
$2$. These $Bronchi$ further divide into smaller $Bronchioles$.
$3$. The $Bronchioles$ are the smallest,narrowest,and most delicate conducting tubes within the lungs,which eventually lead to the $Alveoli$ (air sacs) where gas exchange occurs.
$4$. Therefore,among the given options,$Bronchioles$ are the narrowest and most delicate tubes.

(B) The larynx,also known as the voice box,is a cartilaginous structure located at the top of the trachea. During embryonic development,it is derived from the upper part of the respiratory tract,specifically as a modification of the anterior portion of the trachea. It serves as a passage for air between the pharynx and the trachea.

(A) The human trachea (windpipe) is a straight tube extending up to the mid-thoracic cavity.
It is supported by $16$ to $20$ incomplete $C$-shaped cartilaginous rings.
These rings prevent the trachea from collapsing during inhalation and ensure that the airway remains open for the passage of air.

(B) In birds,the organ responsible for sound production is the $Syrinx$.
It is a specialized vocal organ located at the base of the trachea,where it branches into the bronchi.
Unlike mammals,which use the $Larynx$ for sound production,birds utilize the $Syrinx$ to produce their characteristic songs and calls.

(D) Mucus is a viscous secretion produced by the goblet cells of the mucosal epithelium.
It acts as a physical barrier in the innate immune system by trapping pathogens and preventing them from entering the body tissues.
Mucus is found lining the respiratory tract,the gastrointestinal tract $(GIT)$,and the urogenital tract.
Therefore,all the given options are correct sites where mucus is present.

(C) The vocal cords (vocal folds) are located within the larynx.
They are attached anteriorly to the thyroid cartilage and posteriorly to the arytenoid cartilages.
These attachments allow the vocal cords to be stretched,relaxed,and moved to produce sound during respiration and phonation.

(B) The respiratory system of a rabbit consists of the nasal cavity,pharynx,larynx,trachea,bronchi,bronchioles,and lungs.
The $Oesophagus$ (food pipe) is a part of the digestive system,not the respiratory system.
It is responsible for transporting food from the pharynx to the stomach.

(C) The $Pharynx$ is a muscular tube that serves as a common passage for both food and air.
It is located behind the oral and nasal cavities and leads to both the $Oesophagus$ (for food) and the $Trachea$ (for air).
During swallowing, the $Epiglottis$ covers the $Glottis$ to prevent food from entering the respiratory tract.

(B) The lungs are situated in the thoracic cavity and are protected by a double-layered membrane known as the $Pleural$ $\text{membrane}$.
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 layers, a fluid called $Pleural$ $\text{fluid}$ is present, which reduces friction on the lung surface during breathing.

(D) The trachea (windpipe) in mammals,including rabbits,is a tube supported by cartilaginous rings.
These rings are $C$-shaped or incomplete dorsally to allow the esophagus to expand during the passage of food.
Therefore,the trachea of a rabbit possesses incomplete cartilaginous rings.

(B) The larynx (voice box) contains several cartilages. The arytenoid cartilages are paired,pyramid-shaped cartilages located at the posterior aspect of the larynx. Histologically,the arytenoid cartilages are composed of $hyaline$ cartilage. While the epiglottis is made of elastic cartilage,the arytenoid,thyroid,and cricoid cartilages are primarily hyaline in nature.

(B) The lungs are enclosed in a double-layered membrane called the pleura.
$1$. The outer layer,which is in contact with the thoracic wall,is called the parietal pleura.
$2$. The inner layer,which is in direct contact with the lung surface,is called the visceral pleura.
Therefore,the correct answer is the visceral pleura.

(C) The arytenoid cartilages are a pair of small,pyramid-shaped cartilages that are essential for the movement of the vocal cords. They are located in the $Larynx$ (voice box),specifically on the superior border of the cricoid cartilage. Therefore,the correct option is $C$.

(C) The human respiratory system includes a pair of lungs. Inside the lungs,the bronchioles terminate into thin-walled,vascularized bag-like structures called alveoli. These alveoli are the primary sites for the exchange of gases ($O_2$ and $CO_2$). In a healthy adult human,the total number of alveoli in both lungs is estimated to be approximately $300$ to $400$ million. Therefore,option $C$ is the correct answer.

(C) The $Adam's \text{ } apple$ is a prominent feature in the human throat, particularly visible in adult males.
It is formed by the anterior projection of the $thyroid \text{ } cartilage$, which is the largest cartilage of the $larynx$ (voice box).
Therefore, the correct option is $C$.

(B) The thyroid cartilage is the largest cartilage of the larynx. It is shaped like a shield and is composed of two plates (laminae) that fuse anteriorly in the midline to form the laryngeal prominence,commonly known as the Adam's apple. Therefore,the thyroid cartilage is closed anteriorly (ventrally) and open posteriorly (dorsally).

(C) The trachea (windpipe) is a straight tube extending up to the mid-thoracic cavity. It is supported by $C$-shaped cartilaginous rings. These rings prevent the trachea from collapsing when there is a decrease in air pressure inside the airway,ensuring that the passage remains open for the continuous flow of air.

(A) The correct matching is as follows:
$a$. Larynx is known as the sound box $(r)$.
$b$. Trachea is the air passage tube $(s)$.
$c$. Alveolus is the site of gas exchange, also known as the air sac $(q)$.
$d$. Epiglottis is the cartilaginous flap that covers the glottis during swallowing to prevent food from entering the larynx $(p)$.
Therefore, the correct sequence is $a-r, b-s, c-q, d-p$.

(D) The lungs are protected by the thoracic cage,which is a bony structure.
This cage is formed by the ribs,the vertebral column (at the back),and the sternum (at the front).
Therefore,all these structures collectively play a role in protecting the lungs.

(A) The larynx is composed of several cartilages. The $Cricoid$ cartilage is a single,ring-shaped cartilage located at the base of the larynx. It is often described as being shaped like a signet ring,with the broad portion facing posteriorly and the narrow portion facing anteriorly.

(B) The respiratory system,including the lungs,trachea,and bronchi,is primarily derived from the endoderm.
Specifically,the epithelial lining of the respiratory tract originates from the endoderm,while the associated connective tissues,cartilage,and smooth muscles are derived from the mesoderm.
However,in the context of standard biological classification for the origin of the respiratory system's primary functional lining,it is considered to be of endodermal origin.

(B) The cartilage of Santorini,also known as the corniculate cartilage,is a small,conical nodule of elastic cartilage. It is located at the apex of each arytenoid cartilage. Therefore,it is a band or structure associated with the arytenoid cartilage.

(C) The trachea in mammals,including rabbits,is supported by $C$-shaped cartilaginous rings. These rings are incomplete on the dorsal side,where the trachea comes into contact with the esophagus. This structural arrangement allows the esophagus to expand during the passage of food and prevents the trachea from collapsing,ensuring a continuous airway.

(D) The respiratory tract,including the bronchioles,is lined by a specialized epithelium.
As the bronchioles branch into smaller structures,the epithelium changes from pseudostratified ciliated columnar epithelium (found in larger airways) to a simpler form.
Specifically,the bronchioles are characterized by the presence of cuboidal and columnar epithelial cells,which facilitate the exchange of gases and provide structural support.

(C) The bronchial arteries are systemic arteries that supply blood to the lungs and the visceral pleura. They provide oxygenated blood to the lung tissues (bronchi and bronchioles) to support their metabolic needs,distinct from the pulmonary circulation which is involved in gas exchange.

(C) The human respiratory system consists of a network of tubes. The trachea (windpipe) divides into two primary bronchi,which further divide into secondary and tertiary bronchi and bronchioles. The bronchioles are the narrow,terminal tubes that lead to the alveoli. Therefore,the large number of narrow tubes in the lungs are the bronchioles.

(D) The lungs are protected by a double-layered membrane known as the $Pleura$.
$1$. The outer pleural membrane is in close contact with the thoracic lining.
$2$. The inner pleural membrane is in contact with the lung surface.
$3$. The space between these two membranes is called the pleural cavity,which is filled with pleural fluid to reduce friction during breathing.

(B) The alveolar walls in the lungs are composed of a thin layer of simple squamous epithelium.
This tissue is specialized for the diffusion of gases ($O_2$ and $CO_2$) between the air in the alveoli and the blood in the surrounding capillaries.
Since the primary function is diffusion,the cells are thin and flat (squamous) and lack cilia (non-ciliated) to minimize the diffusion distance.