Which cells lining the air sacs produce surfactant?
Type II alveolar cells
✓
Type I alveolar cells
Alveolar macrophages
Goblet cells
Correct Answer
Type II alveolar cells
Type II alveolar cells are cuboidal cells scattered in the alveolar wall that secrete surfactant, which lowers surface tension and keeps alveoli from collapsing. Type I alveolar cells are thin squamous cells specialized for diffusion, not secretion. Alveolar macrophages engulf debris and pathogens. Goblet cells secrete mucus in the conducting airways.
Category: Alveoli and Membrane
Question 2
What tissue lines most of the trachea and bronchi?
Simple squamous epithelium
Pseudostratified ciliated columnar epithelium
✓
Stratified squamous epithelium
Transitional epithelium
Correct Answer
Pseudostratified ciliated columnar epithelium
Pseudostratified ciliated columnar epithelium with goblet cells lines most of the conducting airways, forming a mucus escalator that sweeps trapped particles toward the pharynx. Simple squamous epithelium forms the thin alveolar walls. Stratified squamous epithelium lines areas exposed to abrasion, such as the oropharynx. Transitional epithelium lines the urinary bladder.
Category: Conducting Zone
Question 3
Which structure folds over the laryngeal inlet during swallowing to keep food out of the airway?
Thyroid cartilage
Cricoid cartilage
Epiglottis
✓
Arytenoid cartilage
Correct Answer
Epiglottis
The epiglottis is a flexible flap of elastic cartilage that covers the opening of the larynx when the larynx rises during swallowing, directing food into the esophagus. Thyroid cartilage is the large shield-shaped cartilage that forms the laryngeal prominence. Cricoid cartilage is the complete ring at the base of the larynx. Arytenoid cartilage anchors the vocal folds and helps move them.
Category: Conducting Zone
Question 4
The open posterior ends of the C-shaped cartilage rings in the windpipe are bridged by which structure?
Cricoid cartilage
Carina
Vocal ligament
Trachealis muscle
✓
Correct Answer
Trachealis muscle
The trachealis muscle is smooth muscle that spans the open back of each tracheal ring, next to the esophagus, and can contract to narrow the trachea. Cricoid cartilage is part of the larynx, above the trachea. Carina is the ridge where the trachea splits into the main bronchi. Vocal ligament lies within the vocal folds of the larynx.
Category: Conducting Zone
Question 5
How many lobes make up the right lung?
Three
✓
Two
Four
Five
Correct Answer
Three
The right lung has three lobes (superior, middle and inferior), separated by the horizontal and oblique fissures. Two is the number of lobes in the left lung, which is smaller because of the heart. Four is not the lobe count of either lung. Five is the total for both lungs combined, not one lung.
Category: Lung Anatomy
Question 6
The indentation on the medial surface of the left lung that makes room for the heart is called the:
Hilum
Cardiac notch
✓
Oblique fissure
Carina
Correct Answer
Cardiac notch
The cardiac notch is a concavity on the left lung that accommodates the heart, which is why the left lung is smaller than the right. Hilum is the region where the bronchi, vessels and nerves enter the lung. Oblique fissure is a groove that separates lobes. Carina is the ridge at the tracheal bifurcation, not part of the lung.
Category: Lung Anatomy
Question 7
What is a primary function of the fluid in the pleural cavity?
Producing surfactant for the alveoli
Carrying oxygen to lung tissue
Reducing friction as the lungs move
✓
Trapping inhaled dust particles
Correct Answer
Reducing friction as the lungs move
Pleural fluid lubricates the visceral and parietal pleurae so they slide smoothly during breathing, and its surface tension helps hold the lungs against the thoracic wall. Producing surfactant for the alveoli is the job of type II alveolar cells. Carrying oxygen to lung tissue is done by blood in the bronchial circulation. Trapping inhaled dust particles is done by mucus in the airways.
Category: Lung Anatomy
Question 8
Which vessels deliver deoxygenated blood to the lungs for gas exchange?
Bronchial arteries
Pulmonary veins
Bronchial veins
Pulmonary arteries
✓
Correct Answer
Pulmonary arteries
The pulmonary arteries carry deoxygenated blood from the right ventricle to the lungs, where it picks up oxygen in the alveolar capillaries. Bronchial arteries supply oxygenated blood to the lung tissue itself. Pulmonary veins return oxygenated blood to the left atrium. Bronchial veins drain blood from the lung tissue rather than delivering blood for gas exchange.
Category: Lung Anatomy
Question 9
Which gas law explains why air flows into the lungs when thoracic volume increases?
Boyle's law
✓
Henry's law
Charles's law
Graham's law
Correct Answer
Boyle's law
Boyle's law states that the pressure of a gas in a closed container is inversely related to its volume, so expanding the thorax lowers intra-alveolar pressure and air flows in. Henry's law relates the amount of gas dissolving in a liquid to its partial pressure. Charles's law relates gas volume to temperature. Graham's law describes how fast gases diffuse based on their molecular mass.
Category: Mechanics of Breathing
Question 10
Which muscle contracts and flattens to provide most of the force for quiet inspiration?
External intercostals
Diaphragm
✓
Internal intercostals
Rectus abdominis
Correct Answer
Diaphragm
The diaphragm is a dome-shaped skeletal muscle that flattens when it contracts, enlarging the thoracic cavity vertically and drawing air into the lungs. External intercostals assist by raising the ribs but do not flatten. Internal intercostals help with forced expiration. Rectus abdominis compresses the abdomen during forced expiration.
Category: Mechanics of Breathing
Question 11
Quiet expiration at rest results mainly from which process?
Contraction of the external intercostals
Contraction of the scalene muscles
Elastic recoil of the lungs
✓
Contraction of the sternocleidomastoid
Correct Answer
Elastic recoil of the lungs
Quiet expiration is passive: when the inspiratory muscles relax, the elastic tissue of the lungs and chest wall recoils, shrinking thoracic volume and pushing air out. Contraction of the external intercostals raises the ribs during inspiration. Contraction of the scalene muscles is an accessory action for forced inspiration. Contraction of the sternocleidomastoid also lifts the rib cage during forced inspiration.
Category: Mechanics of Breathing
Question 12
Under normal conditions, how does intrapleural pressure compare with intra-alveolar pressure?
It is equal
It is higher
It swings above and below
It stays lower
✓
Correct Answer
It stays lower
Intrapleural pressure normally stays lower than intra-alveolar pressure, and this pressure difference keeps the lungs inflated against their tendency to recoil. It is equal only if the pleural cavity is opened, as in a pneumothorax, which lets the lung collapse. It is higher would push the lung inward and collapse it. It swings above and below does not describe healthy breathing, because the pleural pressure remains negative relative to the alveoli.
Category: Mechanics of Breathing
Question 13
Before birth, fetal breathing movements draw which liquid in and out of the developing lungs?
Amniotic fluid
✓
Cerebrospinal fluid
Pleural fluid
Synovial fluid
Correct Answer
Amniotic fluid
Fetal breathing movements move amniotic fluid, along with mucus and surfactant, in and out of the lungs and are thought to help the respiratory muscles and alveoli mature. Cerebrospinal fluid surrounds the brain and spinal cord. Pleural fluid lies between the pleural membranes outside the lungs. Synovial fluid lubricates freely movable joints.
Category: Development
Question 14
During external respiration, why does oxygen diffuse from the alveoli into the pulmonary capillaries?
Its partial pressure is higher in the blood
Its partial pressure is higher in the air sacs
✓
Membrane carrier proteins transport it actively
Exhaled carbon dioxide drags it along
Correct Answer
Its partial pressure is higher in the air sacs
Gases diffuse down their partial pressure gradients, and oxygen partial pressure is higher in alveolar air than in the deoxygenated blood arriving in the pulmonary capillaries. Its partial pressure is higher in the blood would move oxygen the opposite way. Membrane carrier proteins transport it actively is wrong because gas exchange is passive diffusion. Exhaled carbon dioxide drags it along is wrong because each gas follows its own gradient independently.
Category: Gas Exchange
Question 15
In what form is most carbon dioxide carried in the blood?
Dissolved in plasma
Bound to hemoglobin
As bicarbonate ions
✓
Attached to plasma albumin
Correct Answer
As bicarbonate ions
Most carbon dioxide is converted inside red blood cells to carbonic acid, which dissociates into hydrogen ions and bicarbonate ions that travel in the plasma. Dissolved in plasma accounts for only a small fraction. Bound to hemoglobin, as carbaminohemoglobin, carries a minority. Attached to plasma albumin is not a significant transport route for carbon dioxide.
Category: Gas Transport
Question 16
Which gas law states that the total pressure of a gas mixture equals the sum of the partial pressures of its gases?
Henry's law
Charles's law
Graham's law
Dalton's law
✓
Correct Answer
Dalton's law
Dalton's law says each gas in a mixture exerts its own partial pressure, and these add up to the total pressure, which is why oxygen and carbon dioxide can be tracked separately. Henry's law concerns how much gas dissolves in a liquid. Charles's law links gas volume and temperature. Graham's law concerns diffusion rate and molecular mass.
Category: Gas Exchange
Question 17
When bicarbonate ions move out of red blood cells into the plasma, which ion moves in to balance the charge?
Chloride
✓
Sodium
Potassium
Calcium
Correct Answer
Chloride
Chloride ions enter the red blood cell in exchange for bicarbonate, a swap called the chloride shift that keeps the cell electrically balanced. Sodium is the main extracellular cation and is not exchanged in this process. Potassium is the main intracellular cation but does not move in this exchange. Calcium plays no role in carbon dioxide transport.
Category: Gas Transport
Question 18
A decrease in blood pH, as occurs in active tissues, has what effect on hemoglobin?
It binds oxygen more tightly
It releases oxygen more readily
✓
It binds carbon monoxide instead
It stops carrying carbon dioxide
Correct Answer
It releases oxygen more readily
Lower pH reduces the affinity of hemoglobin for oxygen, shifting the dissociation curve to the right so more oxygen is unloaded where tissues are most active; this is the Bohr effect. It binds oxygen more tightly describes a left shift, which happens with higher pH. It binds carbon monoxide instead is unrelated to pH. It stops carrying carbon dioxide is wrong because acidic, active tissues add carbon dioxide to the blood.
Category: Gas Transport
Question 19
Central chemoreceptors in the brainstem respond most directly to changes in which factor?
Blood glucose level
Arterial blood pressure
Cerebrospinal fluid pH
✓
Body temperature
Correct Answer
Cerebrospinal fluid pH
Central chemoreceptors in the medulla oblongata sense the hydrogen ion concentration of cerebrospinal fluid, which rises when blood carbon dioxide diffuses into it, and they increase ventilation in response. Blood glucose level is monitored by the pancreas, not respiratory chemoreceptors. Arterial blood pressure is sensed by baroreceptors. Body temperature is regulated by the hypothalamus.
Category: Control and Modifications
Question 20
During acclimatization to high altitude, low tissue oxygen causes the kidneys to release which hormone?
Aldosterone
Renin
Calcitriol
Erythropoietin
✓
Correct Answer
Erythropoietin
Erythropoietin stimulates the red bone marrow to make more erythrocytes, raising the hemoglobin content of blood so it carries more total oxygen at altitude. Aldosterone is an adrenal hormone that promotes sodium retention. Renin is a kidney enzyme that starts the renin-angiotensin pathway to regulate blood pressure. Calcitriol is the active form of vitamin D that boosts calcium absorption.
Category: Control and Modifications