Respiratory System Anatomy Flashcards
What protects the lungs from the exterior?
The thoracic cage and surrounding musculature, including:
• Cervical musculature (superiorly)
• Respiratory diaphragm (inferiorly)
• Ribs, sternum, and intercostal muscles (anteriorly and laterally)
• Thoracic vertebrae (posteriorly)
What is the mediastinum, and what structures does it house?
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
What is the role of the pulmonary arteries in pulmonary circulation?
The pulmonary arteries carry deoxygenated blood from the right ventricle of the heart to the lungs for oxygenation.
What is the role of the pulmonary veins in pulmonary circulation?
The pulmonary veins carry oxygenated blood from the lungs to the left atrium of the heart.
How does systemic circulation function?
- Oxygenated blood is sent from the left ventricle to the aorta.
- The aorta pumps blood to the body’s arterial network to disperse oxygen and nutrients to tissues.
What is the role of the bronchial arteries in systemic circulation?
The bronchial arteries arise from the thoracic aorta and provide the lung tissues with nutrients and oxygen.
What is the primary function of the respiratory system?
The primary function of the respiratory system is gas exchange, which takes place in the respiratory airways at the alveolar level.
What is pulmonary respiration?
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.
How is carbon dioxide expelled from the body?
- Carbon dioxide diffuses out of the tissue into the bloodstream.
- It is delivered to the lungs.
- It diffuses into the alveoli and is then exhaled back into the environment.
How does oxygen travel from the alveoli to the body tissues?
- Oxygen drawn into the alveoli diffuses into the bloodstream.
- It travels via pulmonary circulation to the heart.
- The heart sends oxygenated blood to the body tissues through systemic circulation.
How is the respiratory system structurally classified?
The respiratory system is divided into two zones:
- Upper Respiratory Tract – structures above the level of the larynx:
• Nasal cavity
• Mouth
• Pharynx - Lower Respiratory Tract – structures below the level of the larynx:
• Larynx
• Trachea
• Bronchi
• Bronchioles
• Respiratory bronchioles
• Alveolar ducts
• Alveoli
How is the respiratory system functionally classified?
The respiratory system is divided into two zones:
- Conducting Zone – structures that serve as a physical passageway for air:
• Nasal passages
• Mouth
• Pharynx
• Larynx
• Trachea
• Bronchi
• Bronchioles - Respiratory Zone – where gas exchange occurs:
• Respiratory bronchioles
• Alveolar ducts
• Alveoli
What is the branching order of the conducting zone from most superficial to deep?
- The trachea bifurcates into the left and right primary bronchi at the level of T4.
- The left and right primary bronchi enter the lungs through openings called the hilus (hilum plural).
- The primary bronchi branch into secondary (lobar) bronchi inside the lung.
- The secondary bronchi divide into tertiary (segmental) bronchi.
- The tertiary bronchi branch into bronchioles.
- The bronchioles branch into terminal bronchioles, which are the last structure in the conducting zone before the respiratory zone begins.
How do cartilage and smooth muscle change from the trachea to the alveoli?
• Cartilage content decreases as airways branch deeper into the lungs.
• Smooth muscle content also decreases, allowing for greater tissue permeability at the alveolar level.
What structures form the respiratory zone?
• Respiratory bronchioles
• Alveolar ducts
• Alveolar sacs
What is an acinus, and how many are there per pulmonary lobule?
• An acinus is the functional unit of the alveoli and the corresponding terminal bronchiole.
• There are approximately 5-7 acini per pulmonary lobule.
What happens to cartilage and smooth muscle as the respiratory zone progresses?
• 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.
What is the primary function of the respiratory system?
The primary function of the respiratory system is gas exchange.
Where does gas exchange occur in the respiratory system?
Gas exchange takes place in the respiratory airways at the alveolar level.
What is pulmonary respiration?
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.
How does carbon dioxide leave the body?
Carbon dioxide diffuses out of the tissue into the bloodstream, travels to the lungs, diffuses into the alveoli, and is then exhaled.
How does oxygen travel from the alveoli to the body tissues?
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.
How is the respiratory system structurally classified?
The respiratory system is classified into two zones:
- Upper Respiratory Tract – Structures above the larynx (nasal cavity, mouth, pharynx).
- Lower Respiratory Tract – Structures below the larynx (larynx, trachea, bronchi, bronchioles, respiratory bronchioles, alveolar ducts, alveoli).
How is the respiratory system functionally classified?
The respiratory system is classified into two zones:
- Conducting Zone – The passageway for air into the body (nasal passages, mouth, pharynx, larynx, trachea, bronchi, bronchioles).
- Respiratory Zone – Where gas exchange takes place (respiratory bronchioles, alveolar ducts, alveoli).
What is the branching order of the trachea and bronchi?
The trachea branches in the following order:
- Trachea bifurcates into left and right primary bronchi at T4.
- Primary bronchi enter the lungs through the hilus.
- Primary bronchi branch into secondary (lobar) bronchi inside the lung.
- Secondary bronchi divide into tertiary (segmental) bronchi.
- Tertiary bronchi branch into bronchioles.
- Bronchioles lead to terminal bronchioles, marking the end of the conducting zone.
How do cartilage and smooth muscle content change along the conducting zone?
Cartilage content decreases while smooth muscle content increases as the airway progresses from the trachea to the alveoli.
What structures are part of the respiratory zone?
What structures are part of the respiratory zone?
What is an acinus?
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.
What happens to cartilage and smooth muscle in the respiratory zone?
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.
What are alveoli made of, and why?
Alveoli are made of simple squamous epithelium, supported by an elastic basement membrane, to allow for efficient gas diffusion.
What are the three types of alveolar cells and their functions?
- 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).
- Type 2 Alveolar Cells (Septal Cells) – Metabolically active cells that secrete surfactant to reduce surface tension and prevent alveolar collapse.
- Type 3 Alveolar Cells (Macrophages) – Large phagocytic cells that engulf foreign material.
How does air move in and out of the lungs?
Air moves through the conducting zone via inhalation and exhalation. No gas exchange occurs in the conducting zone.
What happens during inhalation?
- The diaphragm contracts concentrically, pulling the central tendon inferiorly.
- The diaphragm descends towards the abdomen, increasing thoracic volume and decreasing intra-thoracic pressure, creating a vacuum for air to enter.
- Intra-abdominal pressure increases, pushing the stomach outward.
- The diaphragm assists venous return by “pumping” the vena cava.
How does volume and pressure change during inhalation?
• Thoracic volume increases → Abdominal volume decreases
• Thoracic pressure decreases → Abdominal pressure increases
What happens during exhalation?
• The diaphragm relaxes and ascends to its resting position.
• Thoracic volume decreases, pulmonary pressure increases, and air is expelled.
How does volume and pressure change during exhalation?
• Thoracic volume decreases → Abdominal volume increases
• Thoracic pressure increases → Abdominal pressure decreases
What are the primary and accessory muscles of inhalation?
- Primary muscle: Diaphragm (descends to increase thoracic volume).
- External intercostals: Lift ribs, increasing thoracic volume.
- Accessory muscles:
• Scalenes – Lift upper 2 ribs.
• Sternocleidomastoid – Lifts sternum and clavicle.
• Pectoralis minor – Elevates ribs 3-5.
How does exhalation occur?
Exhalation is usually passive due to the elastic recoil of the lungs. The diaphragm relaxes and ascends, decreasing thoracic volume.
What happens to the pleura during exhalation?
The visceral pleura follows the lung tissue as it recoils, creating negative pressure, which pulls the parietal pleura inward, assisting in rib movement.
What muscles are involved in forced expiration?
• 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.
When are forced expiration muscles recruited?
During heavy exercise, coughing, sneezing, or other situations requiring increased air expulsion.
What is the pleura?
The pleura is a double-layered serous membrane encapsulating the lungs.
What is the function of the parietal pleura?
The parietal pleura lines the walls of the thoracic cavity and is pain-sensitive, with intercostal and phrenic nerve innervation.
What is the function of the visceral pleura?
The visceral pleura adheres to the surface of the lungs.
What is the pleural cavity?
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.
What role does negative pressure play in the pleural cavity?
Negative pressure within the pleural cavity assists with breathing and keeps the lungs inflated by counteracting the lung’s tendency to collapse.
Why is the pressure within the pleural cavity always negative?
Two opposing forces create the negative pressure:
- The visceral pleura pulls inward due to the lungs’ inherent tendency to collapse.
- The parietal pleura pulls outward with thoracic expansion.
What happens if the negative pressure in the pleural cavity is disrupted?
If the seal is broken, the lung will collapse.
Describe the process of inhalation.
• 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).
Describe the process of exhalation.
• 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).
What are non-respiratory air movements?
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).
What is the function of coughing?
Coughing clears the lower respiratory tract by forcefully expelling irritants.
What is required for an effective cough?
Coordination and adequate strength of respiratory and throat muscles.
Where are cough receptors located?
In the larynx and the carina (where the trachea bifurcates into the primary bronchi).
What is the difference between a productive and an effective cough?
What is the difference between a productive and an effective cough?
What is the function of sneezing?
What is the function of sneezing?
What triggers the sneezing reflex?
Mild irritation of nasal cavity receptors, carried via the trigeminal nerve (CN V).
Mild irritation of nasal cavity receptors, carried via the trigeminal nerve (CN V).
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.
What is dyspnea?
Shortness of breath. It is normal with heavy exertion but considered pathological in unexpected situations.
Shortness of breath. It is normal with heavy exertion but considered pathological in unexpected situations.
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)
When else can dyspnea occur?
When cellular respiration exceeds alveolar respiratory capacity, such as in oxygen debt.
What is the “Breathlessness Position,” and how does it help with dyspnea?
• 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.
What are the four main systems contributing to respiratory dysfunction?
- 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).
- Cardiovascular System:
Impaired perfusion/gas exchange (atherosclerosis, pulmonary embolism).
Low hemoglobin (Hb) or anemia.
- 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.
- Nervous System:
• CNS or PNS lesions leading to denervation of respiratory muscles.
