BIOL 204 602 2026SP Anatomy and Physiology II Exam 3 Respiratory System…
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Free BIOL 204 602 2026SP Anatomy and Physiology II Exam 3 Respiratory System… Questions
According to the oxygen-hemoglobin (Hb) dissociation curve, PO₂ in the lungs of 100 mm Hg results in Hb being 98% saturated. At high altitude, there is less O₂. At a PO₂ in the lungs of 80 mm Hg, Hb would be ________ saturated.
- 100%
- 98%
- 95%
- less than 50%
Explanation
Explanation
Correct Answer: C) 95%
The oxygen-hemoglobin dissociation curve is sigmoidal, meaning that hemoglobin remains highly saturated even with moderate decreases in PO₂. At a PO₂ of 80 mm Hg, hemoglobin saturation is still around 95%, only slightly lower than at 100 mm Hg. This plateau portion of the curve ensures adequate oxygen loading in the lungs even at lower oxygen levels, such as at high altitude.
Which structure is lined with simple squamous epithelium?
- trachea
- alveolus
- oropharynx
- nasopharynx
Explanation
Explanation
Correct Answer: B) alveolus
Alveoli are lined with simple squamous epithelium to allow for efficient gas exchange. The thin, flat cells minimize diffusion distance, enabling oxygen and carbon dioxide to move easily between air and blood.
The trachea and nasopharynx are lined with pseudostratified ciliated columnar epithelium, while the oropharynx is lined with stratified squamous epithelium.
The most powerful respiratory stimulus for breathing in a healthy person is ________
- increase of carbon dioxide
- loss of oxygen in tissues
- acidosis
- alkalosis
Explanation
Explanation
Correct Answer: A) increase of carbon dioxide
In healthy individuals, the primary stimulus for breathing is an increase in carbon dioxide levels in the blood. Elevated CO₂ leads to increased hydrogen ion concentration, which stimulates central chemoreceptors in the brain to increase the rate and depth of breathing.
Although low oxygen levels can stimulate breathing, this occurs mainly when oxygen levels drop significantly. Acidosis contributes to stimulation but is largely driven by increased CO₂, while alkalosis suppresses respiration.
Respiratory control centers are located in the ________
- pons and midbrain
- upper spinal cord and medulla
- medulla and pons
- midbrain and medulla
Explanation
Explanation
Correct Answer: C) medulla and pons
The respiratory control centers are located in the medulla oblongata and the pons of the brainstem. The medulla contains the primary centers that control the rhythm of breathing, while the pons helps regulate the rate and depth of respiration.
The midbrain and spinal cord are not the primary centers for respiratory control.
Which of the following is NOT part of the respiratory membrane of the lungs?
- basement membrane
- alveolar epithelium
- single layer of smooth muscle cells
- capillary endothelium
Explanation
Explanation
Correct Answer: C) single layer of smooth muscle cells
The respiratory membrane is the thin structure where gas exchange occurs between the alveoli and the blood. It consists of the alveolar epithelium, the basement membrane, and the capillary endothelium. These layers are extremely thin to allow efficient diffusion of oxygen and carbon dioxide.
Smooth muscle cells are not part of the respiratory membrane. They are found in the walls of airways such as bronchi and bronchioles and are involved in regulating airway diameter, not gas exchange.
Air movement into the lungs and the drop in intrapulmonary pressure occur after the initial mechanical expansion of the thoracic cavity. Thoracic volume does not decrease during inspiration; it increases.
Intrapulmonary pressure is the ________
- difference between atmospheric pressure and respiratory pressure
- negative pressure in the intrapleural space
- pressure within the pleural cavity
- pressure within the alveoli of the lungs
Explanation
Explanation
Correct Answer: D) pressure within the alveoli of the lungs
Intrapulmonary pressure, also known as alveolar pressure, refers to the pressure of air within the alveoli of the lungs. This pressure changes during breathing to allow air to move in and out of the lungs. During inspiration, intrapulmonary pressure decreases below atmospheric pressure, allowing air to flow into the lungs. During expiration, it increases above atmospheric pressure, pushing air out.
The other options describe different pressures or incorrect concepts. Intrapleural pressure refers to pressure within the pleural cavity and is normally negative. The difference between atmospheric and intrapulmonary pressure drives airflow but is not the definition of intrapulmonary pressure itself.
The walls of the alveoli are composed of two types of cells, type I and type II alveolar cells. The function of type II alveolar cells is to ________
- protect the lungs from bacterial invasion
- secrete surfactant
- replace mucus in the alveoli
- trap dust and other debris
Explanation
Explanation
Correct Answer: B) secrete surfactant
Type II alveolar cells are responsible for producing and secreting pulmonary surfactant, a substance that reduces surface tension within the alveoli. This prevents alveolar collapse during exhalation and allows the lungs to expand more easily during inhalation. Surfactant is essential for efficient gas exchange and maintaining alveolar stability.
Protection and debris removal are functions of alveolar macrophages, not type II cells, and mucus is not a primary component within alveoli.
Which of the choices below determines the direction of respiratory gas movement?
- molecular weight and size of the gas molecule
- the temperature
- partial pressure gradient
- solubility in water
Explanation
Explanation
Correct Answer: C) partial pressure gradient
The direction of respiratory gas movement is determined by the partial pressure gradient. Gases move from areas of higher partial pressure to areas of lower partial pressure. This principle governs the exchange of oxygen and carbon dioxide between the alveoli and the blood, as well as between the blood and body tissues.
Molecular size, temperature, and solubility can influence the rate of diffusion, but they do not determine the direction of movement.
The Haldane Effect refers to the effect of ________ loading onto or unloading off of hemoglobin and hemoglobin’s ability to bind ________ in an RBC.
- O₂, H⁺
- O₂, CO₂
- CO₂, O₂
- H⁺, O₂
Explanation
Explanation
Correct Answer: C) CO₂, O₂
The Haldane effect describes how the binding and release of carbon dioxide by hemoglobin are influenced by oxygen levels. When oxygen binds to hemoglobin, it reduces hemoglobin’s ability to carry carbon dioxide, promoting CO₂ release in the lungs. Conversely, when oxygen is unloaded in tissues, hemoglobin can carry more CO₂.
Which statement about CO₂ is FALSE?
- Its accumulation in the blood is associated with a decrease in pH
- Its concentration in the blood is decreased by hyperventilatio
- More CO₂ dissolves in the blood plasma than is carried in the RBCs
- CO₂ concentrations are greater in venous blood than arterial blood
Explanation
Explanation
Correct Answer: C) More CO₂ dissolves in the blood plasma than is carried in the RBCs
Most carbon dioxide is transported in the blood as bicarbonate ions formed within red blood cells, not simply dissolved in plasma. Only a small portion of CO₂ is dissolved directly in plasma. Therefore, stating that more CO₂ dissolves in plasma than is carried in RBCs is incorrect.
CO₂ accumulation lowers pH, hyperventilation reduces CO₂ levels, and venous blood contains more CO₂ than arterial blood.
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