Respiratory System Anatomy

Question 1

What protects the lungs from the exterior?

Answer 1

The thoracic cage and surrounding musculature, including:

• Cervical musculature (superiorly)
• Respiratory diaphragm (inferiorly)
• Ribs, sternum, and intercostal muscles (anteriorly and laterally)
• Thoracic vertebrae (posteriorly)

Question 2

What is the mediastinum, and what structures does it house?

Answer 2

The mediastinum is the space between the lungs that separates the right lung from the left lung. It houses:

• The heart
• Great blood vessels
• Esophagus
• Thymus
• Lymph nodes
• Vagus nerve
• Phrenic nerve

Question 3

What is the role of the pulmonary arteries in pulmonary circulation?

Answer 3

The pulmonary arteries carry deoxygenated blood from the right ventricle of the heart to the lungs for oxygenation.

Question 4

What is the role of the pulmonary veins in pulmonary circulation?

Answer 4

The pulmonary veins carry oxygenated blood from the lungs to the left atrium of the heart.

Question 5

How does systemic circulation function?

Answer 5

1. Oxygenated blood is sent from the left ventricle to the aorta.
2. The aorta pumps blood to the body’s arterial network to disperse oxygen and nutrients to tissues.

Question 6

What is the role of the bronchial arteries in systemic circulation?

Answer 6

The bronchial arteries arise from the thoracic aorta and provide the lung tissues with nutrients and oxygen.

Question 8

What is the primary function of the respiratory system?

Answer 8

The primary function of the respiratory system is gas exchange, which takes place in the respiratory airways at the alveolar level.

Question 9

What is pulmonary respiration?

Answer 9

Pulmonary respiration involves the exchange of gases across the respiratory membrane:

• Oxygen enters systemic circulation and the body’s tissues, where it is used to form ATP at the cellular level.
• Carbon dioxide is produced as a byproduct and expelled.

Question 10

How is carbon dioxide expelled from the body?

Answer 10

1. Carbon dioxide diffuses out of the tissue into the bloodstream.
2. It is delivered to the lungs.
3. It diffuses into the alveoli and is then exhaled back into the environment.

Question 11

How does oxygen travel from the alveoli to the body tissues?

Answer 11

1. Oxygen drawn into the alveoli diffuses into the bloodstream.
2. It travels via pulmonary circulation to the heart.
3. The heart sends oxygenated blood to the body tissues through systemic circulation.

Question 12

How is the respiratory system structurally classified?

Answer 12

The respiratory system is divided into two zones:

1. Upper Respiratory Tract – structures above the level of the larynx:
   • Nasal cavity
   • Mouth
   • Pharynx
2. Lower Respiratory Tract – structures below the level of the larynx:
   • Larynx
   • Trachea
   • Bronchi
   • Bronchioles
   • Respiratory bronchioles
   • Alveolar ducts
   • Alveoli

Question 14

How is the respiratory system functionally classified?

Answer 14

The respiratory system is divided into two zones:

1. Conducting Zone – structures that serve as a physical passageway for air:
   • Nasal passages
   • Mouth
   • Pharynx
   • Larynx
   • Trachea
   • Bronchi
   • Bronchioles
2. Respiratory Zone – where gas exchange occurs:
   • Respiratory bronchioles
   • Alveolar ducts
   • Alveoli

Question 15

What is the branching order of the conducting zone from most superficial to deep?

Answer 15

1. The trachea bifurcates into the left and right primary bronchi at the level of T4.
2. The left and right primary bronchi enter the lungs through openings called the hilus (hilum plural).
3. The primary bronchi branch into secondary (lobar) bronchi inside the lung.
4. The secondary bronchi divide into tertiary (segmental) bronchi.
5. The tertiary bronchi branch into bronchioles.
6. The bronchioles branch into terminal bronchioles, which are the last structure in the conducting zone before the respiratory zone begins.

Question 16

How do cartilage and smooth muscle change from the trachea to the alveoli?

Answer 16

• Cartilage content decreases as airways branch deeper into the lungs.
• Smooth muscle content also decreases, allowing for greater tissue permeability at the alveolar level.

Question 17

What structures form the respiratory zone?

Answer 17

• Respiratory bronchioles
• Alveolar ducts
• Alveolar sacs

Question 18

What is an acinus, and how many are there per pulmonary lobule?

Answer 18

• An acinus is the functional unit of the alveoli and the corresponding terminal bronchiole.
• There are approximately 5-7 acini per pulmonary lobule.

Question 19

What happens to cartilage and smooth muscle as the respiratory zone progresses?

Answer 19

• Cartilage decreases from the trachea until it disappears at the bronchioles.
• Bronchioles are encircled by spiraling layers of smooth muscle tissue, which gradually decreases toward the alveoli to allow for greater tissue permeability.

Question 20

What is the primary function of the respiratory system?

Answer 20

The primary function of the respiratory system is gas exchange.

Question 21

Where does gas exchange occur in the respiratory system?

Answer 21

Gas exchange takes place in the respiratory airways at the alveolar level.

Question 22

What is pulmonary respiration?

Answer 22

Pulmonary respiration involves the exchange of gases across the respiratory membrane. Oxygen enters systemic circulation and the body’s tissues, where it is used to form ATP. Carbon dioxide, a byproduct, is expelled.

Question 23

How does carbon dioxide leave the body?

Answer 23

Carbon dioxide diffuses out of the tissue into the bloodstream, travels to the lungs, diffuses into the alveoli, and is then exhaled.

Question 24

How does oxygen travel from the alveoli to the body tissues?

Answer 24

Oxygen diffuses from the alveoli into the bloodstream, travels via pulmonary circulation to the heart, and is then sent to body tissues via systemic circulation.

Question 25

How is the respiratory system structurally classified?

Answer 25

The respiratory system is classified into two zones: 1. Upper Respiratory Tract – Structures above the larynx (nasal cavity, mouth, pharynx). 2. Lower Respiratory Tract – Structures below the larynx (larynx, trachea, bronchi, bronchioles, respiratory bronchioles, alveolar ducts, alveoli).

Question 26

How is the respiratory system functionally classified?

Answer 26

The respiratory system is classified into two zones: 1. Conducting Zone – The passageway for air into the body (nasal passages, mouth, pharynx, larynx, trachea, bronchi, bronchioles). 2. Respiratory Zone – Where gas exchange takes place (respiratory bronchioles, alveolar ducts, alveoli).

Question 27

What is the branching order of the trachea and bronchi?

Answer 27

The trachea branches in the following order: 1. Trachea bifurcates into left and right primary bronchi at T4. 2. Primary bronchi enter the lungs through the hilus. 3. Primary bronchi branch into secondary (lobar) bronchi inside the lung. 4. Secondary bronchi divide into tertiary (segmental) bronchi. 5. Tertiary bronchi branch into bronchioles. 6. Bronchioles lead to terminal bronchioles, marking the end of the conducting zone.

Question 28

How do cartilage and smooth muscle content change along the conducting zone?

Answer 28

Cartilage content decreases while smooth muscle content increases as the airway progresses from the trachea to the alveoli.

Question 29

What structures are part of the respiratory zone?

Answer 29

What structures are part of the respiratory zone?

Question 30

What is an acinus?

Answer 30

An acinus is the functional unit of the lung, consisting of alveoli and the corresponding terminal bronchiole. There are about 5-7 acini per pulmonary lobule.

Question 31

What happens to cartilage and smooth muscle in the respiratory zone?

Answer 31

Cartilage disappears at the level of the bronchioles. Bronchioles are surrounded by a spiraling layer of smooth muscle, which decreases at the level of the alveoli to allow greater tissue permeability.

Question 32

What are alveoli made of, and why?

Answer 32

Alveoli are made of simple squamous epithelium, supported by an elastic basement membrane, to allow for efficient gas diffusion.

Question 33

What are the three types of alveolar cells and their functions?

Answer 33

1. Type 1 Alveolar Cells – Simple squamous epithelium with fibroblasts that produce elastic reticular fibers. These cells provide an efficient gas exchange surface (~160m² surface area). 2. Type 2 Alveolar Cells (Septal Cells) – Metabolically active cells that secrete surfactant to reduce surface tension and prevent alveolar collapse. 3. Type 3 Alveolar Cells (Macrophages) – Large phagocytic cells that engulf foreign material.

Question 34

How does air move in and out of the lungs?

Answer 34

Air moves through the conducting zone via inhalation and exhalation. No gas exchange occurs in the conducting zone.

Question 35

What happens during inhalation?

Answer 35

1. The diaphragm contracts concentrically, pulling the central tendon inferiorly. 2. The diaphragm descends towards the abdomen, increasing thoracic volume and decreasing intra-thoracic pressure, creating a vacuum for air to enter. 3. Intra-abdominal pressure increases, pushing the stomach outward. 4. The diaphragm assists venous return by "pumping" the vena cava.

Question 36

How does volume and pressure change during inhalation?

Answer 36

• Thoracic volume increases → Abdominal volume decreases • Thoracic pressure decreases → Abdominal pressure increases

Question 37

What happens during exhalation?

Answer 37

• The diaphragm relaxes and ascends to its resting position. • Thoracic volume decreases, pulmonary pressure increases, and air is expelled.

Question 38

How does volume and pressure change during exhalation?

Answer 38

• Thoracic volume decreases → Abdominal volume increases • Thoracic pressure increases → Abdominal pressure decreases

Question 39

What are the primary and accessory muscles of inhalation?

Answer 39

1. Primary muscle: Diaphragm (descends to increase thoracic volume). 2. External intercostals: Lift ribs, increasing thoracic volume. 3. Accessory muscles: • Scalenes – Lift upper 2 ribs. • Sternocleidomastoid – Lifts sternum and clavicle. • Pectoralis minor – Elevates ribs 3-5.

Question 40

How does exhalation occur?

Answer 40

Exhalation is usually passive due to the elastic recoil of the lungs. The diaphragm relaxes and ascends, decreasing thoracic volume.

Question 41

What happens to the pleura during exhalation?

Answer 41

The visceral pleura follows the lung tissue as it recoils, creating negative pressure, which pulls the parietal pleura inward, assisting in rib movement.

Question 42

What muscles are involved in forced expiration?

Answer 42

• Internal intercostals – Bring ribs together, decreasing thoracic volume and increasing thoracic pressure. • Quadratus lumborum (QL) • Serratus posterior inferior • Abdominal muscles – Increase intra-abdominal pressure, forcing the diaphragm upward and expelling air.

Question 43

When are forced expiration muscles recruited?

Answer 43

During heavy exercise, coughing, sneezing, or other situations requiring increased air expulsion.

Question 44

What is the pleura?

Answer 44

The pleura is a double-layered serous membrane encapsulating the lungs.

Question 45

What is the function of the parietal pleura?

Answer 45

The parietal pleura lines the walls of the thoracic cavity and is pain-sensitive, with intercostal and phrenic nerve innervation.

Question 46

What is the function of the visceral pleura?

Answer 46

The visceral pleura adheres to the surface of the lungs.

Question 47

What is the pleural cavity?

Answer 47

The pleural cavity is the "potential" space between the two pleural layers, containing fluid secreted by the pleura to decrease friction and allow smooth lung movement.

Question 48

What role does negative pressure play in the pleural cavity?

Answer 48

Negative pressure within the pleural cavity assists with breathing and keeps the lungs inflated by counteracting the lung's tendency to collapse.

Question 49

Why is the pressure within the pleural cavity always negative?

Answer 49

Two opposing forces create the negative pressure: 1. The visceral pleura pulls inward due to the lungs’ inherent tendency to collapse. 2. The parietal pleura pulls outward with thoracic expansion.

Question 50

What happens if the negative pressure in the pleural cavity is disrupted?

Answer 50

If the seal is broken, the lung will collapse.

Question 51

Describe the process of inhalation.

Answer 51

• The diaphragm contracts and descends. • The chest expands, pulling the lungs outward. • Alveolar pressure decreases, drawing air into the lungs. • Air moves from high pressure (outside the lungs) to low pressure (inside alveoli).

Question 52

Describe the process of exhalation.

Answer 52

• The diaphragm relaxes and ascends. • The chest and lungs recoil inward. • Alveolar pressure increases, forcing air out of the lungs. • Air moves from high pressure (inside alveoli) to low pressure (outside the lungs).

Question 53

What are non-respiratory air movements?

Answer 53

Movements that do not aid in respiration but serve other functions, such as: • Clearing air passages (coughing, sneezing). • Expressing emotions (laughing, crying). • Reflex-driven actions (yawning, sneezing, coughing).

Question 54

What is the function of coughing?

Answer 54

Coughing clears the lower respiratory tract by forcefully expelling irritants.

Question 55

What is required for an effective cough?

Answer 55

Coordination and adequate strength of respiratory and throat muscles.

Question 56

Where are cough receptors located?

Answer 56

In the larynx and the carina (where the trachea bifurcates into the primary bronchi).

Question 57

What is the difference between a productive and an effective cough?

Answer 57

What is the difference between a productive and an effective cough?

Question 58

What is the function of sneezing?

Answer 58

What is the function of sneezing?

Question 59

What triggers the sneezing reflex?

Answer 59

Mild irritation of nasal cavity receptors, carried via the trigeminal nerve (CN V).

Question 60

Mild irritation of nasal cavity receptors, carried via the trigeminal nerve (CN V).

Answer 60

Air is forced up through the glottis and directed into the nasal passages by depressing the uvula, closing the opening between the pharynx and oral cavity.

Question 61

What is dyspnea?

Answer 61

Shortness of breath. It is normal with heavy exertion but considered pathological in unexpected situations.

Question 62

Shortness of breath. It is normal with heavy exertion but considered pathological in unexpected situations.

Answer 62

In 85% of cases, dyspnea is due to: • Asthma • Pneumonia • Cardiac ischemia • Interstitial lung disease • Congestive heart failure (CHF) • Chronic obstructive pulmonary disease (COPD) • Psychogenic causes (panic disorder, anxiety)

Question 63

When else can dyspnea occur?

Answer 63

When cellular respiration exceeds alveolar respiratory capacity, such as in oxygen debt.

Question 64

What is the “Breathlessness Position,” and how does it help with dyspnea?

Answer 64

• The patient sits forward, elbows on knees or a table, allowing the abdomen to drop forward. • Gravity assists in diaphragmatic excursion, making breathing easier. • This is less efficient than standing and bending over (as a track athlete would), but more achievable for people with respiratory conditions.

Question 65

What are the four main systems contributing to respiratory dysfunction?

Answer 65

1. Pulmonary System: • Obstructed airways (foreign bodies, tumors, thick mucus). • Bronchi constriction. • Lung tissue pathology (fibrosis, scarring). Loss of functional units (disease, surgery, cancer). • Compromised intra-pleural pressure (pneumothorax). 2. Cardiovascular System: Impaired perfusion/gas exchange (atherosclerosis, pulmonary embolism). Low hemoglobin (Hb) or anemia. 3. Musculoskeletal System: • Fatigue, pain, or restriction of respiratory muscles. • Obesity or late-trimester pregnancy limiting inspiration (especially in supine/prone positions). • Neuromuscular disorders (e.g., myasthenia gravis, muscular dystrophy) affecting respiratory muscles. 4. Nervous System: • CNS or PNS lesions leading to denervation of respiratory muscles.