The respiratory system is responsible for gas exchange between the body and the external environment.
Classification
The respiratory system is often divided into the:
Conducting zone - From the nose to the terminal bronchioles. Its main function is to direct the air.
Respiratory zone - Respiratory bronchioles and alveoli. Its function is to perform gas exchange.
Read on for some thoughts on why this can be a difficult topic for teachers and students alike, five suggestions to help improve such outcomes, and thoughts on why a virtual lab could be rewarding.
There are three reasons in particular why the anatomy of the respiratory System can be difficult, even for the most diligent of students.
The anatomy of the respiratory system is a large part of the human body. Not being able to visualize processes in living things can reduce enthusiasm for learning and make it difficult for students to stay motivated.
The respiratory tract is also classified into the
There’s a lot of information to take in, like:
Upper respiratory tract
Lower respiratory tract.
The upper respiratory tract consists of :
1. Nose and nasal cavity:
Figure 3: The structures of the nasal cavity, the oral cavity, and the tongue.
This area serves to direct the air when breathing.
The nose is a facial feature that is supported by the skull and hyaline cartilage. Hyaline cartilage forms the nasal septum, which separates the nose into the right and left sides.
The outer opening of the nose is the external nares. They direct the air into the nasal vestibule and out again. The vestibule of the nose contains hairs that act as filters, preventing unwanted dust, insects, and other debris from entering the airways.
The nasal vestibule opens into the nasal cavity.
The side walls of the nasal cavity have three ridged elevations known as the nasal conchae which create turbulence in the air that allows air to reach the olfactory receptors and warms and humidifies the incoming air.
Figure 4: An anterior view and lateral cross-section showing the paranasal sinuses.
The paranasal sinuses are a collection of cavities that connect to the nasal cavity. They include:
Frontal Sinus
Ethmoidal Sinus
Maxillary Sinuses(Right and Left)
Sphenoidal Sinus
The primary functions of the paranasal sinuses include:
-Reduce skull weight
-Influences sound by acting as a resonance chamber.
Pharynx:
The pharynx is a muscular cavity that connects the nasal cavity, oral cavity, and larynx. The pharynx is divided into three regions, as shown:
Figure 5: A lateral view showing the key structures of the pharynx.
Nasopharynx: is a single chamber behind the nasal cavity. It contains the tonsils or adenoids, large lymph nodes, that house white blood cells that protect the body from pathogens. In the nasopharynx, there is also a hole that maintains air pressure in the middle ear.
Oropharynx(the throat): This region is located posterior to the oral cavity and inferior to the nasopharynx. It is considered a part of the respiratory and digestive systems as it transports air and ingested food and beverages. The oropharynx is continuous with the laryngopharynx below.
Laryngopharynx: This is the lowest part of the pharynx. It branches into the esophagus posteriorly and the trachea anteriorly. In the laryngopharynx, all food and fluids are expected to pass from the laryngopharynx into the esophagus, while air passes through the larynx and into the trachea on its way to the lungs.
The primary functions of the pharynx include:
Airway
Transport of food and drinks
Protection against pathogens
Balances air pressure in the middle ear
Larynx:
Figure 6: The key structures of the larynx.
This is a hollow structure inferior to the pharynx and superior to the trachea. As it houses the vocal cords, it is commonly known as the voice box. It is made of cartilage and ligaments. Three large pieces of cartilage (along with nine smaller pieces) make up the structural framework of the larynx:
Epiglottis - is the most superior part of the larynx composed of an elongated and flexible piece of elastic cartilage. During breathing and speaking, it is in a vertical position that permits movement of air but during swallowing, it closes over the opening to the larynx to prevent the entry of food and fluid into the airway.
Thyroid cartilage- is a large, butterfly-shaped piece of hyaline cartilage. It is known as the “Adam’s apple” as increased testosterone levels during male puberty can cause it to grow to become visible on the anterior surface of the neck. It supports and protects the vocal cords which lie posterior to the cartilage.
Cricoid cartilage - forms the inferior portion of the larynx. It is a complete ring of hyaline cartilage.
The hollow inside of the larynx is lined with a mucous membrane with two pairs of ligaments, known as the vocal folds, found on the lateral walls of the larynx. The inferior pair is known as the true vocal folds, or vocal cords, which are elastic and can produce sound when air is moved across them during exhalation. The upper pair are known as the vestibular folds or false vocal cords. They don’t produce sound but prevent choking by closing off the opening into the larynx during swallowing.
The primary functions of the larynx include:
Conduction of air into the trachea
Protection of the airways from the entry of food and fluid
Production of sound
With those points in mind, here are five things you can incorporate into your cellular respiration class to make it more engaging, accessible, and fun for you and your students.
People love stories. One way to build a story revolves around a true story of how a particular scientist struggled to get to the information students were studying.
Herophilus (ca. 325 BC) distinguished between arteries and veins, arguing with Aristotle that they contained air. Erasistratos (304-250 BC), better known as the father of philosophy, was the first to use scientific principles to explain breathing. According to him, air is drawn into the lungs and sent to the heart through the pulmonary arteries. In the heart, the air is converted into "spirit of life" which is distributed through the arteries to all parts of the body, while the brain further converts the spirit of life into "spirit of animals" which travels through the vena cava to activate the muscles. Erasistratus seemed to have understood that the heart valves only allowed flow in one direction, but he was unable to apply this knowledge to clarify the transport of the spirit of life or blood throughout the body. After Erasistratos, the interests of the Greeks shifted from medicine to philosophy and science, and the development of physiological knowledge stopped for about 400 years.
The Lower Respiratory Tract:
The lower respiratory tract conducts air from the trachea through the bronchial tree of the lungs to the alveoli. The tree and its associated parts allow for gas exchange.
Figure 7: The lower respiratory tract and the diaphragm.
A.The trachea( the windpipe):
Figure 8: The trachea. Transverse cross-section of the trachea and esophagus.
It is a hollow tube made of hyaline cartilage, ligaments, and smooth muscle. The length of the trachea consists of about 16-20 pieces of incomplete or “C” shaped rings of hyaline cartilage (tracheal cartilage) which keep the trachea open at all times. The inferior portion bifurcates into the right and left main bronchi.
The epithelium that lines the lumen produces mucus and contains cilia. The mucus traps foreign particles and pathogens, while the cilia sweep mucus toward the pharynx where it can be swallowed or expelled. This is known as mucociliary clearance.
The primary functions of the trachea include:
Conducting air and holding the airway open
Cleans air to protect the lungs from pathogens and foreign particles.
B. The Bronchial Tree: This conveys air from the trachea to the smallest passageways leading to the air sacs, or alveoli, where gas exchange takes place. It is composed of the:
Bronchi
Bronchioles
Alveoli
a.Bronchi: These are larger airways that conduct air from the trachea into each lung. All bronchi are held open by hyaline cartilage, although the amount of hyaline cartilage gradually decreases as the distance from the trachea increases.
Figure 9: The bronchi and a cross-section of a bronchus.
Bronchi are categorized into 3 types:
Main bronchi starts from the inferior trachea to divide into the right and left main, or primary, bronchi which penetrate the medial surface of the lung (Hilum).
Lobar bronchi(secondary bronchi) branch from the main bronchi and penetrate the lobes of each lung. Three lobar bronchi on the right penetrate the three lobes of the right lung. Two lobar bronchi on the left penetrate the two lobes of the left lung.
Segmental bronchi(tertiary bronchi) branch from the lobar bronchi and penetrate individual segments of the lung lobes.
Bronchioles are small airways that branch multiple times from the segmental bronchi to the alveoli, or air sacs, of the lungs. They lack hyaline cartilage.
Figure 10: The bronchioles and a cross-section of a bronchiole.
They are sub-categorized as:
Terminal bronchioles: the final portion of the conducting zone.
Respiratory bronchioles: the smallest bronchioles where gaseous exchange occurs. They turn into alveolar ducts culminating in alveolar sacs.
Alveoli are the air sacs of the lungs. Each alveolus is composed of a single, thin layer of epithelium arranged in a hollow pouch-shaped structure. Each alveolus is surrounded by a capillary bed, elastic fibers, and smooth muscle cells and neighboring alveoli are connected by alveolar pores, permitting air movement between alveoli. The alveoli perform gas exchange.
Figure 11: Key structures of the alveoli.
The lungs are large, air-filled, vital organs. They are encased by membranes called pleurae. The wide inferior border of the lungs is in contact with the diaphragm and is called the base. The narrow, pointed superior portion of the lungs is called the apex.
The region between the right and left lungs is the mediastinum. This is where the heart, thymus, and great blood vessels are located. Blood vessels, the main bronchi, nerves, and lymphatic vessels enter the lung in the hilum and then branch extensively throughout the lung. Each lung is divided into anatomically distinct lobes by fissures, with each lobe containing a portion of the bronchial tree leading into the alveoli. The right lung has 3 lobes while the left lung has 2 lobes.
Figure 12: The lobular structure of the lungs.
The pleurae are serous membranes that surround the lungs in a double layer. The lungs are directly encased by the visceral layer while the parietal layer covers the rib cage. The two layers meet at the hilum and are separated by the pleural space with some serous fluid which reduces friction.
Figure 13: The pleurae of the lungs.
Visualization can be very helpful in understanding the anatomy of the respiratory tract, there are several mnemonics such as "LONe" to represent the three regions of the pharynx without regard to lowercase letters, ie.
namely
L - Laryngopharynx
O - Oropharynx(the throat)
N - Nasopharynx
A unique way to teach the anatomy of the respiratory system is through a virtual laboratory simulation. At Labster, we’re dedicated to delivering fully interactive advanced laboratory simulations that utilize gamification elements like storytelling and scoring systems, inside an immersive and engaging 3D universe.
Check out the Labster anatomy of the respiratory system simulation that allows students to learn about the anatomy of the respiratory through active, inquiry-based learning. In the simulation, students will be introduced to the respiratory tract and pleura and get to assemble the lobes of the lungs and bronchial tree on our live anatomy model.
Learn more about the anatomy of the respiratory system simulation here or get in touch to find out how you can start using virtual labs with your students.
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