Respiratory System: Overview and Practice Questions (2024)

The respiratory system is a complex network of organs and structures responsible for the exchange of gases essential for sustaining life.

From the inhalation of oxygen to the removal of carbon dioxide, this system plays a vital role in maintaining the body’s homeostasis.

This article provides an overview of the respiratory system, exploring its structure, function, and significance in maintaining overall health.

What is the Respiratory System?

The respiratory system consists of specific organs and structures, including the lungs, trachea, bronchi, and diaphragm. Its primary function is to facilitate gas exchange, allowing oxygen to enter the blood and carbon dioxide to be expelled. This process is essential for maintaining cellular metabolism and overall homeostasis.

Respiratory System Structures

The respiratory system is composed of various structures that work together to facilitate breathing and gas exchange.

These structures include:

• Lungs
• Trachea
• Upper airway
• Lower airway
• Alveoli
• Blood vessels
• Chest wall
• Diaphragm
• Accessory muscles
• Pleural membranes

Watch this video or keep reading to learn more about the structures of the respiratory system.

Lungs

The lungs are spongy, air-filled organs located on either side of the chest (thorax). Their primary function is to facilitate gas exchange.

This occurs by taking in oxygen from the air we breathe and expelling carbon dioxide during exhalation.

The right lung is typically larger and consists of three lobes, while the left lung has two lobes. The lungs’ interior surfaces are lined with millions of microscopic sacs called alveoli, where the actual gas exchange occurs.

These organs are protected by the rib cage and are closely associated with the respiratory tract, which helps direct air in and out.

Trachea

The trachea, commonly known as the windpipe, is a vital component of the respiratory system, serving as the main airway that connects the larynx to the bronchi of the lungs.

It is a cylindrical tube about 4-6 inches long and 1 inch in diameter, located in the front part of the neck.

The trachea’s walls are reinforced with C-shaped rings of cartilage, which provide structural support and prevent the trachea from collapsing during inhalation.

The trachea is lined with a mucous membrane that filters, moistens, and warms the air as it passes into the lungs.

Upper Airway

The upper airway forms the first part of the respiratory tract through which air passes before reaching the lungs. It includes the nasal cavity, mouth, pharynx, and larynx.

The primary role of the upper airway is to warm, moisten, and filter the air we breathe. The nasal cavity, specifically, is lined with mucous membranes and tiny hairs called cilia that trap dust and pathogens.

The pharynx serves as a pathway for both air and food, while the larynx contains the vocal cords and is a critical checkpoint that prevents food and other foreign objects from entering the trachea.

Lower Airway

The lower airway consists of the trachea, bronchi, bronchioles, and alveoli. After air passes through the trachea, it enters the bronchi—two tubes that branch off into each lung.

The bronchi further divide into smaller bronchioles, spreading throughout each lung. The bronchioles eventually lead to the alveoli, the tiny sacs where gas exchange occurs.

The lower airway plays a crucial role in conveying air efficiently to the alveoli, with its mucous lining and cilia continuing to filter and cleanse the air along the way.

Alveoli

Alveoli are tiny, balloon-like structures that are the final branches of the respiratory tree and the primary sites of gas exchange in the lungs.

Each lung contains millions of alveoli, forming clusters known as alveolar sacs. These sacs are surrounded by a network of capillaries where the exchange of oxygen and carbon dioxide takes place.

The walls of the alveoli are extremely thin to facilitate this exchange, allowing oxygen to pass into the blood and carbon dioxide to be expelled from the bloodstream into the alveoli, where it is expelled.

Blood Vessels

The blood vessels in the respiratory system include arteries, veins, and capillaries that play a critical role in transporting gases to and from the alveoli.

Pulmonary arteries carry oxygen-poor, carbon dioxide-rich blood from the heart to the lungs, where it releases carbon dioxide and absorbs oxygen.

The oxygen-rich blood then travels back to the heart through the pulmonary veins.

This close association between the alveoli and the blood vessels ensures efficient gas exchange, vital for maintaining healthy respiratory function.

Chest Wall

The chest wall, also known as the thoracic wall, is a structural framework that includes the rib cage, muscles, and skin. It protects the lungs and other vital organs within the thorax.

It plays a crucial role in respiration by supporting and maintaining the necessary pressure gradients that facilitate breathing.

The ribs, interconnected by intercostal muscles, expand and contract to alter the volume of the chest cavity during normal breathing, aiding in the inhalation and exhalation of air.

This mechanical movement is essential for the lungs to draw in air and expel carbon dioxide.

Diaphragm

The diaphragm is a large, dome-shaped muscle that separates the thoracic cavity from the abdominal cavity.

It serves as the primary muscle of respiration, contracting and flattening during inhalation to increase the volume of the thoracic cavity, thereby reducing internal pressure and drawing air into the lungs.

Upon relaxation, the diaphragm resumes its dome shape, decreasing thoracic volume and increasing pressure, which expels air from the lungs.

Its rhythmic contractions are crucial for the ventilation of the lungs and are involuntary and controlled by the respiratory center in the brain.

Accessory Muscles

Accessory muscles of respiration include various muscles in the neck, chest, and abdomen that assist in the breathing process, particularly during strenuous activity or respiratory distress.

Common accessory muscles include the sternocleidomastoid and scalene muscles in the neck, which help elevate the sternum and rib cage, thereby increasing the volume of the thoracic cavity during forceful inhalation.

Similarly, muscles such as the pectoralis minor and the abdominal muscles assist in forceful exhalation by pulling the rib cage down and compressing the abdominal cavity, respectively, which pushes air out of the lungs more vigorously.

Pleural Membranes

The pleural membranes are two thin layers of tissue that envelop each lung. The parietal pleura is the outer layer that lines the inner surface of the chest wall. The visceral pleura is the inner layer that covers the lungs themselves.

Between these two layers is a small space known as the pleural cavity, which contains a lubricating fluid that reduces friction as the lungs expand and contract during breathing.

This fluid also helps create a pressure gradient that keeps the lungs inflated. The pleural membranes are essential for the smooth and efficient movement of the lungs during respiration.

Respiratory System Practice Questions

1. What are the passageways between the ambient environment and gas exchange units of the lungs known as?
Conducting airways

2. The conducting airways are divided into what?
Upper and lower airways

3. What does the upper airway consist of?
Nose, oral cavity, pharynx, and larynx.

4. What are the functions of the upper airway?
To act as a conductor of air, to humidify cool and warm inspired air, to prevent foreign materials from entering the tracheobronchial tree, and to serve as an important area in speech and smell.

5. What are the functions of the nose?
To filter, humidify, and condition warm or cool air.

6. What does the outer portion of the nose consist of?
Bone and cartilage

7. Does gas exchange occur in conducting airways?
No, it does not.

8. Posteriorly, the nasal septum is formed by what?
Perpendicular plate and the ethmoid bone.

9. What forms the roof of the nasal cavity?
Nasal bones, frontal process of the maxilla, and cribriform plate of the ethmoid bone.

10. What forms the posterior section of the nasal cavity?
It consists of a flexible mass of densely packed collagen fibers and the soft palate.

11. What is nasal flaring?
The widening of the nostrils during periods of respiratory distress.

12. Where is stratified squamous epithelium found?
The anterior portion of the nasal cavity, oral cavity, oropharynx, and laryngopharynx.

13. What is the major muscle of ventilation?
The diaphragm

14. What does simple cuboidal epithelium do in the respiratory system?
Forms the walls of the alveoli.

15. What are the three bony protrusions on the lateral walls of the nasal cavity?
Superior, middle, and inferior nasal turbinates or conchae.

16. What are turbinates?
They play a major role in humidification and the warming of inspired air.

17. What are the two nasal passageways between the nares and the nasopharynx?
Choanae

18. What is sinusitis?
Inflammation or swelling of the sinuses.

19. What patient problems can be seen regarding the soft palate and uvula?
Patients will have difficulty swallowing, sucking, blowing, and making speech sounds.

20. What elevates the soft palate?
Levator veli palatine

21. What is the oral cavity lined with?
Nonciliated stratified squamous epithelium

22. What are the divisions of the pharynx?
Nasopharynx, oropharynx, and laryngopharynx

23. What is the nasopharynx lined with?
Pseudostratified ciliated columnar epithelium

24. What is another name for the pharyngeal tonsil?
Adenoid

25. What happens if the pharyngeal tonsil is inflamed?
It may block the passage of air between the nose and throat.

26. What is another name for the pharynx?
Throat

27. What supplies motor innervation of each hemidiaphragm?
The phrenic and glossopharyngeal nerves.

28. What is the vallecula epiglottica?
It is an important landmark during the insertion of the endotracheal tube into the trachea.

29. Where is the vallecula epiglottica located?
It is located between the glossoepiglottic folds on each side of the posterior oropharynx.

30. What is another name for the larynx?
Voicebox

31. Where is the larynx located?
Between the base of the tongue and the upper end of the trachea.

32. What is the function of the larynx?
It acts as a passageway of air between the pharynx and the trachea. It also serves as a protective mechanism against the aspiration of liquids and foods and also helps generate speech.

33. What types of cartilage does the larynx consist of?
Thyroid cartilage, cricoid cartilage, and epiglottis.

34. What is the interior of the larynx composed of?
It is lined with a mucus membrane.

35. What is another name for thyroid cartilage?
Adam’s apple

36. What is the epiglottis?
It is a broad, spoon-shaped fibrocartilaginous structure that prevents the aspiration of foods and liquids by covering the opening of the larynx during swallowing.

37. What is the narrowest point of the larynx?
Glottis

38. What can happen in the glottis of infants and young children?
Glottic and subglottic swelling (edema) secondary to viral or bacterial infection, which is known as croup syndrome.

39. What is acute epiglottis?
It’s a life-threatening condition characterized by supraglottic airway obstruction that results from inflammation of the epiglottis, aryepiglottic folds, and false vocal folds.

40. What is another important function of the larynx?
It performs closure during exhalation, which is known as the Valsalva maneuver.

41. What is the tracheobronchial tree composed of?
It is made up of cartilaginous and non-cartilaginous airways.

42. What are cartilaginous airways?
They serve only to conduct air between the external environment and the sites of gas exchange.

43. What are non-cartilaginous airways?
They serve as both conductors of air and sites of gas exchange.

44. What are the layers of the tracheobronchial tree composed of?
Epithelial lining, lamina propria, and cartilaginous layer.

45. What is epithelial lining?
Pseudostratified ciliated columnar epithelium with numerous mucus glands separated from the lamina propria.

46. Where does the pseudostratified ciliated epithelium extend from?
It extends from the trachea to the respiratory bronchioles.

47. What composes the mucus lining of the tracheobronchial tree?
The mucus lining of the tracheobronchial tree is called the “mucus blanket.” It is composed of 95% water and 5% glycoproteins, carbohydrates, lipids, DNA, and some cellular debris.

48. What cells produce mucus?
Goblet cells

49. What glands produce the most mucus?
Submucosal glands

50. What cells are increased in asthmatic airways?
Both goblet cells and submucosal glands are increased.

51. What are gel and sol layers?
The sol layer is thin and adjacent to the epithelial lining, while the gel layer is thicker (vicious) and adjacent to the inner luminal surface.

52. What is the mucociliary escalator?
It is an important part of the cleansing mechanism of the tracheobronchial tree.

53. What is the lamina propria?
The submucosal layer of the tracheobronchial tree.

54. What surrounds the lamina propria?
Peribronchial sheath

55. What cells play a role in the immune response?
Mast cells

56. What chemicals, when released, increase vascular permeability, smooth muscle contraction, increased mucus secretions, and vasodilation with edema?
Histamine, heparin, platelet-activating factor (PAF), eosinophil chemotactic factor of anaphylaxis (ECF-A), and leukotrienes.

57. What is atelectasis?
Alveolar collapse

58. What is the normal production of IgE?
200 ng/mL

59. The cartilaginous airways consist of what?
Trachea, main stem bronchi, lobar bronchi, segmental bronchi, and subsegmental bronchi.

60. What is the bifurcation of the trachea?
The carina

61. How many c-shaped cartilages support the trachea?
15-20

62. What is the right mainstem bronchus?
It branches from the trachea at a 25-degree angle and is wider, shorter, and more vertical than the left mainstem bronchus.

63. How does the left mainstem bronchus branch from the trachea?
It branches from the trachea at a 40-60 degree angle.

64. What structure lies posterior to the trachea?
The esophagus

65. What is the thorax?
It protects the organs of the cardiopulmonary system.

66. What does the thorax consist of?
Manubrium sterni, body of the sternum, and xiphoid process.

67. What are the non-cartilaginous airways?
Bronchioles and the terminal bronchioles

68. Where are the canals of Lambert located?
They are located in the terminal bronchioles.

69. Where are clara cells located?
They are located in the terminal bronchioles.

70. What nourishes the tracheobronchial tree?
Bronchial arteries

71. How much of a patient’s cardiac output feeds the tracheobronchial tree?
The normal bronchial arterial blood flow is 1% of the cardiac output.

72. What structure of the heart directs blood flow to the lungs?
Pulmonary arteries

73. What is venous admixture?
The mixing of venous blood and freshly oxygenated blood.

74. What are the sites of gas exchange?
Respiratory bronchioles, alveolar ducts, and alveolar sacs.

75. Approximately how many alveoli are there in the average adult male?
300 million

76. How much surface area is provided by the alveoli?
70 square meters, which is about the size of a tennis court.

77. What are type 1 cells?
Squamous pneumocytes

78. What are type 2 cells?
Granular pneumocytes

79. What are the pores of Kohn?
They are small holes in the walls of the interalveolar septa that permit gas to move between adjacent alveoli.

80. What is the role of alveolar macrophages?
They play a major role in removing bacteria and other foreign particles from the respiratory tract.

81. What is the pulmonary vascular system?
It delivers blood to and from the lungs for gas exchange and provides nutritional substances distal to the terminal bronchioles.

82. What does the pulmonary vascular system consist of?
Arteries, arterioles, capillaries, venules, and veins.

83. What are arteries?
They are blood vessels that transport oxygenated blood throughout the body.

84. What are arterioles?
They supply nutrients to the respiratory bronchioles, alveolar ducts, and alveoli. They play an important role in the distribution and regulation of blood and are known as resistance vessels.

85. What are capillaries?
The smallest blood vessels in the body that form a connection between arterioles and venules. They allow the exchange of blood, nutrients, and waste.

86. What are veins and venules?
Venules empty blood into veins, which carry nonoxygenated blood back to the heart.

87. What is the mediastinum composed of?
The trachea, heart, major blood vessels (great vessels), thymus gland, and lymph nodes.

88. Pseudostratified ciliated columnar epithelium lines what?
It lines the trachea and nasopharynx.

89. How does the horizontal fissure extend?
It extends horizontally from the oblique fissure to about the level of the 4th costal cartilage and separates the middle from the upper lobe.

90. Where are the canals of Lambert found?
Terminal bronchioles

91. What is the joint between the manubrium and the body of the sternum called?
The manubriosternal joint; also referred to as the sternal angle or angle of Louis.

92. What are the first 7 ribs?
True ribs; because they are attached directly to the sternum.

93. What are ribs 8-10?
False ribs; because they are attached to cartilage that connects to the sternum.

94. What are ribs 11-12?
Floating ribs; because they are not attached to the sternum or cartilage.

95. What are the accessory muscles of inspiration?
External intercostal, scalenus, sternocleidomastoid, pectoralis, and trapezius.

96. What are the accessory muscles of expiration?
Rectus abdominis, external abdominis obliques, internal abdominis obliques, transverse abdominis, and internal intercostals.

97. What does an increased AP diameter represent?
Air trapping in the lungs, which is commonly seen in patients with COPD.

98. What is the normal AP diameter?
1:2 in healthy adults

99. What is the hilum?
It is part of the lung where the mainstem bronchi vessels and nerves enter.

100. What are the three layers of tissues in an arterial vessel?
The inner layer (tunica intima), middle layer (tunica media), and outer layer (tunica adventitia)

101. What is the importance of the capillary beds of the lungs?
They are essential for gas and fluid exchange, and they also play an important biochemical role in the production and destruction of a broad range of biologically active substances.

102. What is the wall thickness of a pulmonary capillary?
The walls of the pulmonary capillaries are less than 0.1 nanometers thick, and the external diameter of each vessel is 10 nanometers.

103. What are the resistance vessels?
Arterioles because they play an important role in the distribution and regulation of blood

104. Why are veins referred to as capacitance vessels?
Because they are capable of collecting a large amount of blood with very little pressure change

105. How is the right lung different from the left?
The right lung is larger and heavier than the left. It is divided into upper, middle, and lower lobes by oblique and horizontal fissures.

Final Thoughts

The respiratory system plays a critical role in sustaining life by managing the gases essential for the body’s metabolic processes.

From the larger airways that conduct air to the delicate alveoli where gas exchange occurs, each component plays a critical role.

Understanding its structure and function is essential for appreciating the intricate mechanisms that support breathing and overall health.