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OEBC Written Exam study materials
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OEBC Written Exam practice questions

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Question 1Osteopathic Principles and Philosophy

Which concept from A.T. Still's writings holds that structure and function are reciprocally interrelated within the living body?

  1. The doctrine of humoral balance
  2. The principle of specific etiology
  3. The law of Laplace
  4. The unity of structure and function Correct answer.

Explanation

Still emphasized that anatomy and physiology are inseparable, so alteration in structure produces alteration in function and vice versa. This reciprocal relationship is the foundation for manipulative treatment rationale in osteopathy.

Question 2Osteopathic Principles and Philosophy

The osteopathic principle that the body possesses self-regulatory and self-healing mechanisms best supports which clinical approach?

  1. Withholding all treatment until symptoms resolve spontaneously
  2. Relying solely on surgical correction of somatic dysfunction
  3. Prescribing antibiotics for every inflammatory presentation
  4. Supporting inherent homeostatic capacity while removing obstacles to recovery Correct answer.

Explanation

Osteopathic philosophy holds that the body has intrinsic capacity for self-regulation and healing. The physician's role is to remove impediments and support that capacity rather than override it.

Question 3Osteopathic Principles and Philosophy

According to the osteopathic concept of the somatic component, which finding most directly represents it?

  1. Reduced visual acuity on screening
  2. Restricted motion of a thoracic segment with associated tenderness and tissue texture change Correct answer.
  3. Elevated serum creatinine on laboratory testing
  4. A family history of type 2 diabetes

Explanation

The somatic component is a musculoskeletal expression of dysfunction comprising asymmetry, range-of-motion restriction, tissue texture abnormality, and tenderness. These findings are palpable and regional rather than laboratory-based.

Question 4Osteopathic Principles and Philosophy

Which statement best describes the osteopathic principle of the artery rule as originally framed?

  1. Venous return is irrelevant to somatic dysfunction
  2. Blood flow is essential to health, and impediments to circulation impair tissue function Correct answer.
  3. Arterial pulse rate determines the appropriate treatment frequency
  4. Lymphatic flow is independent of musculoskeletal motion

Explanation

The artery rule holds that adequate circulation is necessary for tissue health and that obstruction to flow contributes to disease. Osteopathic treatment aims to remove mechanical impediments to circulation.

Question 5Osteopathic Principles and Philosophy

In osteopathic philosophy, the term 'holism' most accurately refers to which idea?

  1. The person is an integrated whole whose systems cannot be understood in isolation Correct answer.
  2. Disease is always the result of a single genetic mutation
  3. Only psychological factors determine health outcomes
  4. Each organ system should be treated by a separate specialist without coordination

Explanation

Holism asserts that the body is an integrated unit in which mind, body, and environment interact. Clinical reasoning therefore considers the whole person rather than isolated organ systems.

Question 6Osteopathic Principles and Philosophy

Which historical figure is credited with founding the osteopathic profession and articulating its core tenets?

  1. John Harvey Kellogg
  2. Andrew Taylor Still Correct answer.
  3. William Osler
  4. Daniel David Palmer

Explanation

A.T. Still founded osteopathy in the late nineteenth century and set out its philosophical tenets in his writings. His principles remain the basis of osteopathic professional identity.

Question 7Osteopathic Principles and Philosophy

A patient with chronic low back pain has restricted lumbar motion, paraspinal hypertonicity, and pain that worsens with prolonged sitting. Which element of the osteopathic clinical framework is most directly illustrated?

  1. A purely psychological pain disorder
  2. A systemic infection requiring antibiotics
  3. A somatic component contributing to the patient's pain experience Correct answer.
  4. An irreversible structural deformity requiring surgery

Explanation

Palpable motion restriction and tissue texture change with associated pain constitute the somatic component of the patient's presentation. Osteopathic reasoning links this regional dysfunction to the broader clinical picture.

Question 8Osteopathic Principles and Philosophy

A patient recovers from pneumonia with supportive care and osteopathic manipulative treatment aimed at improving thoracic mobility and secretion clearance. Which tenet is most clearly being supported?

  1. The principle of therapeutic nihilism
  2. The body's self-regulatory and self-healing capacity Correct answer.
  3. The concept of fixed organ pathology
  4. The doctrine of specific etiology

Explanation

Treatment that improves mechanics and drainage while the body clears infection supports intrinsic self-healing mechanisms. The physician facilitates rather than replaces homeostatic function.

Question 9Osteopathic Principles and Philosophy

During examination, a physician notes a tissue texture change in the paraspinal muscles at T6 that feels boggy and warmer than adjacent segments. Which component of somatic dysfunction does this finding best represent?

  1. Tissue texture abnormality Correct answer.
  2. Asymmetry of bony landmarks
  3. Restriction of motion
  4. Tenderness elicited on palpation

Explanation

Tissue texture abnormality describes changes in the feel of soft tissues, such as boggy, ropy, or edematous quality, often with temperature change. It is one of the four diagnostic criteria of somatic dysfunction.

Question 10Osteopathic Principles and Philosophy

A physician explains that treating a restricted rib may improve respiratory mechanics and venous return. Which osteopathic principle most directly justifies this reasoning?

  1. The principle of single-cause etiology
  2. The doctrine of organ specificity
  3. The concept of spontaneous generation
  4. Reciprocal relationship between structure and function Correct answer.

Explanation

The structure-function principle predicts that correcting mechanical restriction can improve physiologic function such as ventilation and circulation. This is the rationale for treating somatic dysfunction to benefit related systems.

Question 11Osteopathic Principles and Philosophy

A patient with asthma has restricted upper thoracic and rib motion. The physician treats these restrictions and also reviews inhaler technique and environmental triggers. This management best reflects which combination?

  1. Somatic treatment integrated with holistic patient care Correct answer.
  2. Exclusive reliance on manipulative treatment
  3. A reductionist organ-specific approach
  4. Exclusive reliance on pharmacologic management

Explanation

Combining somatic treatment with attention to medication use and environmental factors reflects holistic, integrated care. Osteopathic management addresses both mechanical and broader contextual contributors.

Question 12Osteopathic Principles and Philosophy

Which observation best illustrates the osteopathic concept that the body tends toward homeostasis through interconnected regulatory systems?

  1. Compensatory vasoconstriction and tachycardia maintain blood pressure after hemorrhage Correct answer.
  2. Blood pressure remains fixed regardless of volume status
  3. A fractured bone heals only after surgical fixation in all cases
  4. Immune responses are independent of nervous and endocrine signaling

Explanation

Baroreceptor-mediated vasoconstriction and tachycardia demonstrate integrated regulatory responses that defend homeostasis. Osteopathic philosophy views such compensation as evidence of the body's self-regulating unity.

Question 13Osteopathic Principles and Philosophy

A physician uses a muscle energy technique to correct a restricted sacroiliac joint. Which philosophic rationale best explains why this approach aligns with osteopathic tenets?

  1. It permanently immobilizes the segment to prevent recurrence
  2. It relies on pharmacological relaxation of the joint capsule
  3. It imposes a passive force that overrides protective reflexes
  4. It uses the patient's own neuromuscular activity to restore motion, engaging self-regulatory capacity Correct answer.

Explanation

Muscle energy technique recruits the patient's voluntary muscle contraction against a counterforce to improve motion, engaging inherent neuromuscular function. This respects the principle of supporting the body's self-regulating capacity.

Question 14Osteopathic Principles and Philosophy

Which statement most accurately reflects the osteopathic understanding of the relationship between the somatic and visceral systems?

  1. Only visceral pathology can affect somatic tissues
  2. Somatic dysfunction is always the primary cause of visceral disease
  3. Visceral dysfunction can produce reflex somatic changes, and somatic dysfunction can influence visceral function Correct answer.
  4. The two systems operate independently with no reflex interaction

Explanation

Osteopathic theory holds that viscerosomatic and somatovisceral reflexes operate in both directions. This bidirectional influence supports treating somatic dysfunction as part of comprehensive care.

Question 15Osteopathic Principles and Philosophy

A patient with a long-standing ankle restriction develops compensatory altered gait and ipsilateral knee pain. Which principle best explains this cascade?

  1. Pain is always referred from a single dermatome without mechanical compensation
  2. Compensation occurs only in the upper extremities
  3. Joint restrictions remain localized without distant effects
  4. The body compensates as an integrated unit, so dysfunction in one region alters function elsewhere Correct answer.

Explanation

Osteopathic reasoning holds that the body functions as an integrated unit, so a restriction in one region produces compensatory alterations elsewhere. This explains the development of gait change and knee pain.

Question 16Osteopathic Principles and Philosophy

Which finding on palpation would most specifically support a diagnosis of somatic dysfunction rather than simple muscle fatigue after exercise?

  1. Diffuse symmetric soreness in multiple muscle groups after a new workout
  2. Localized asymmetry with restricted motion in a defined plane and palpable tissue texture change Correct answer.
  3. Bilateral tenderness without motion restriction
  4. Generalized fatigue without focal findings

Explanation

Somatic dysfunction requires identifiable asymmetry, range-of-motion restriction, tissue texture abnormality, or tenderness in a regional pattern. Focal asymmetry plus motion restriction is more specific than diffuse post-exercise soreness.

Question 17Osteopathic Principles and Philosophy

A physician argues that treating a patient's restricted thoracic spine will improve lymphatic return and immune surveillance. Which chain of reasoning is most consistent with osteopathic principles?

  1. Lymphatic flow is driven solely by cardiac contraction and is unaffected by motion
  2. Thoracic motion has no relationship to circulation
  3. Improved musculoskeletal motion supports venous and lymphatic flow, which supports tissue health and immune function Correct answer.
  4. Immune surveillance depends only on genetic factors

Explanation

Osteopathic theory links musculoskeletal motion to venous and lymphatic return, which in turn supports tissue health and immune function. This reasoning connects structure, circulation, and host defense within an integrated model.

Question 18Osteopathic Principles and Philosophy

A patient reports recurrent headaches with associated upper cervical motion restriction and paraspinal tenderness. The physician treats the cervical dysfunction and the headaches improve. Which osteopathic concept is best illustrated?

  1. Somatic dysfunction may contribute to regional symptoms through shared neurologic and mechanical mechanisms Correct answer.
  2. Cervical motion restriction is unrelated to headache
  3. Tenderness on palpation confirms a diagnosis of migraine
  4. Headaches are always intracranial in origin

Explanation

Improvement of headache after correction of cervical somatic dysfunction supports a somatic contribution through shared neurologic and mechanical pathways. Osteopathic reasoning considers regional musculoskeletal findings as potential contributors to symptoms.

Question 19Osteopathic Principles and Philosophy

A clinician weighs whether to treat a patient's somatic dysfunction before or after addressing an acute infection. Which reasoning best reflects osteopathic philosophy?

  1. Treat only the somatic dysfunction and defer medical management
  2. Address the urgent medical condition while using osteopathic care to support host defenses and comfort as appropriate Correct answer.
  3. Avoid any consideration of the patient's whole clinical context
  4. Withhold all osteopathic care until the infection has fully resolved

Explanation

Osteopathic philosophy supports integrating manipulative care with appropriate medical management rather than choosing one exclusively. The whole patient's acute needs guide sequencing and the supportive role of treatment.

Question 20Osteopathic Principles and Philosophy

Which statement best captures the osteopathic view of disease as described in its foundational tenets?

  1. Disease reflects an imbalance of interacting structural, physiologic, and environmental factors rather than a single isolated cause Correct answer.
  2. Disease results only from inherited genetic defects
  3. Disease is unrelated to circulation and tissue mechanics
  4. Disease is caused exclusively by misalignment of the spine

Explanation

Osteopathic philosophy frames disease as the product of interacting factors affecting the whole person, including structure, physiology, and environment. This contrasts with strictly reductionist single-cause models.

Question 21Anatomy

Which cranial nerve supplies motor innervation to the muscles of mastication?

  1. Hypoglossal nerve (CN XII)
  2. Trigeminal nerve (CN V), mandibular division Correct answer.
  3. Glossopharyngeal nerve (CN IX)
  4. Facial nerve (CN VII)

Explanation

The mandibular division of the trigeminal nerve carries the motor fibers for the masseter, temporalis, and both pterygoid muscles, which together move the mandible during chewing. The trigeminal nerve is therefore the principal motor nerve of mastication, while its other divisions are predominantly sensory.

Question 22Anatomy

Which muscle of the tongue is responsible for protruding the tongue and is innervated by the hypoglossal nerve?

  1. Palatoglossus
  2. Styloglossus
  3. Genioglossus Correct answer.
  4. Superior longitudinal muscle

Explanation

The genioglossus arises from the genial tubercle of the mandible and fans into the tongue; its posterior fibers pull the tongue forward and depress the central portion. It is innervated by the hypoglossal nerve and is the main protrusive muscle of the tongue.

Question 23Anatomy

The parotid duct (Stensen duct) opens into the oral cavity at which location?

  1. The posterior tonsillar pillar
  2. The floor of the mouth beside the lingual frenum
  3. The papilla in the sublingual caruncle
  4. The buccal mucosa opposite the maxillary second molar Correct answer.

Explanation

Stensen duct travels anteriorly across the masseter and pierces the buccinator to open on the inner surface of the cheek opposite the crown of the maxillary second molar. This landmark is clinically important because stones or obstruction produce swelling in that region.

Question 24Anatomy

Which artery is the principal blood supply to the maxillary teeth?

  1. Inferior alveolar artery Correct answer.
  2. Lingual artery
  3. Facial artery
  4. Greater palatine artery

Explanation

The inferior alveolar artery, a branch of the maxillary artery, descends through the mandibular canal and gives off dental branches to the mandibular teeth, continuing as the mental and incisive arteries. The maxillary teeth are supplied mainly by the superior alveolar branches of the maxillary artery, so the inferior alveolar artery is the correct answer for the mandibular arch.

Question 25Anatomy

Which structure separates the maxillary sinus from the roots of the maxillary posterior teeth?

  1. The pterygoid plates
  2. The nasal septum
  3. The zygomatic process of the maxilla
  4. The thin bony floor of the sinus (alveolar recess) Correct answer.

Explanation

The maxillary sinus sits above the roots of the maxillary molars and premolars, separated only by a thin plate of bone called the alveolar recess or sinus floor. This intimate relationship explains why periapical infection or extraction of these teeth can create an oroantral communication.

Question 26Anatomy

The temporomandibular joint is best described as which type of joint?

  1. A pure hinge joint
  2. A fibrous synarthrosis
  3. A primary cartilaginous joint
  4. A synovial joint with an articular disc, allowing both rotation and translation Correct answer.

Explanation

The temporomandibular joint is a synovial joint divided into upper and lower compartments by a fibrocartilaginous disc. The lower compartment permits rotation, while the upper compartment allows the condyle and disc to translate forward during opening.

Question 27Anatomy

Which muscle depresses the mandible and is also a retractor of the mandible?

  1. Medial pterygoid
  2. Lateral pterygoid Correct answer.
  3. Masseter
  4. Temporalis

Explanation

The lateral pterygoid, particularly its inferior head, pulls the condyle forward and downward, assisting opening and protrusion; its superior head contributes to retrusion and closing. The other masticatory muscles act mainly to elevate the mandible.

Question 28Anatomy

Which nerve provides sensation to the anterior two-thirds of the tongue?

  1. Glossopharyngeal nerve
  2. Lingual branch of the mandibular nerve Correct answer.
  3. Hypoglossal nerve
  4. Chorda tympani branch of the facial nerve

Explanation

General sensation from the anterior two-thirds of the tongue travels via the lingual nerve, a branch of the mandibular division of the trigeminal nerve. Taste from the same region is carried by the chorda tympani, which travels with the lingual nerve but serves a different function.

Question 29Anatomy

The pterygomandibular space, a common site for inferior alveolar nerve block, lies between which two structures?

  1. The lateral pterygoid and the maxillary tuberosity
  2. The medial pterygoid muscle and the ramus of the mandible Correct answer.
  3. The stylohyoid ligament and the hyoid bone
  4. The masseter and the buccinator

Explanation

The pterygomandibular space is bounded laterally by the medial surface of the ramus and medially by the medial pterygoid muscle. The inferior alveolar and lingual nerves pass through this space, which is why it is targeted for local anesthesia.

Question 30Anatomy

Which bone forms the anterior part of the hard palate?

  1. The vomer
  2. The palatine bone
  3. The sphenoid bone
  4. The maxilla Correct answer.

Explanation

The hard palate is formed by the palatine processes of the maxillae anteriorly and the horizontal plates of the palatine bones posteriorly. The maxilla therefore contributes the larger anterior portion.

Question 31Anatomy

Which ligament limits opening of the mandible and prevents excessive forward translation of the condyle?

  1. Stylomandibular ligament
  2. Pterygomandibular raphe
  3. Sphenomandibular ligament
  4. Temporomandibular ligament (lateral ligament) Correct answer.

Explanation

The temporomandibular (lateral) ligament reinforces the lateral capsule and resists excessive forward and downward movement of the condyle during opening. The accessory ligaments play lesser roles in limiting motion.

Question 32Anatomy

Which muscle forms the anterior pillar of the fauces?

  1. Palatopharyngeus
  2. Palatoglossus Correct answer.
  3. Levator veli palatini
  4. Tensor veli palatini

Explanation

The palatoglossus muscle runs from the soft palate into the tongue and forms the palatoglossal fold, which is the anterior pillar of the fauces. The palatopharyngeus forms the posterior pillar.

Question 33Anatomy

The submandibular ganglion is functionally associated with which nerve?

  1. The mylohyoid nerve
  2. The buccal nerve
  3. The inferior alveolar nerve
  4. The lingual nerve Correct answer.

Explanation

The submandibular ganglion is suspended from the lingual nerve, and its postganglionic parasympathetic fibers travel with it to the submandibular and sublingual glands. This connection explains why the lingual nerve serves as a landmark in the submandibular triangle.

Question 34Anatomy

Which paranasal sinus is largest and is most commonly involved in sinusitis?

  1. Frontal sinus
  2. Sphenoid sinus
  3. Maxillary sinus Correct answer.
  4. Ethmoid sinus

Explanation

The maxillary sinus is the largest of the paranasal sinuses and drains through a relatively high ostium, which impairs gravitational drainage. This anatomy makes it the sinus most frequently affected by infection and fluid accumulation.

Question 35Anatomy

Which nerve is at risk of injury during surgical removal of a mandibular third molar in the region of the lingual plate?

  1. The lingual nerve Correct answer.
  2. The long buccal branch of the facial nerve
  3. The buccal nerve
  4. The mylohyoid nerve

Explanation

The lingual nerve runs close to the lingual cortex of the posterior mandible, often just beneath the mucosa, and can be stretched or sectioned during third molar surgery. Injury produces altered sensation and taste on the anterior tongue.

Question 36Anatomy

Which structure passes through the foramen ovale?

  1. The maxillary division of the trigeminal nerve
  2. The mandibular division of the trigeminal nerve Correct answer.
  3. The internal carotid artery
  4. The middle meningeal artery

Explanation

The foramen ovale transmits the mandibular division of the trigeminal nerve along with the lesser petrosal nerve and accessory meningeal artery. The maxillary division instead passes through the foramen rotundum.

Question 37Anatomy

Which muscle of the soft palate opens the pharyngotympanic tube during swallowing?

  1. Levator veli palatini
  2. Musculus uvulae
  3. Tensor veli palatini Correct answer.
  4. Palatopharyngeus

Explanation

The tensor veli palatini, supplied by the mandibular division of the trigeminal nerve, contracts to open the pharyngotympanic tube and equalize middle ear pressure. The levator elevates the palate rather than opening the tube.

Question 38Anatomy

The mental foramen is located in which region of the mandible?

  1. The posterior border of the ramus
  2. The coronoid process
  3. The mandibular notch
  4. The anterior surface of the body, near the premolars Correct answer.

Explanation

The mental foramen opens on the anterior surface of the mandibular body, typically near the apices of the premolars, and transmits the mental nerve and vessels. It marks the end of the mandibular canal and is a key landmark for local anesthesia.

Question 39Anatomy

Which salivary gland is predominantly innervated by parasympathetic fibers from the glossopharyngeal nerve?

  1. The sublingual gland
  2. The submandibular gland
  3. The minor palatal glands
  4. The parotid gland Correct answer.

Explanation

Secretomotor fibers to the parotid gland arise from the inferior salivatory nucleus, travel with the glossopharyngeal nerve, and synapse in the otic ganglion before reaching the gland via the auriculotemporal nerve. The other major glands receive parasympathetic supply mainly from the facial nerve.

Question 40Anatomy

Which muscle forms the floor of the mouth and elevates the hyoid bone?

  1. Mylohyoid Correct answer.
  2. Digastric anterior belly
  3. Geniohyoid
  4. Stylohyoid

Explanation

The mylohyoid arises from the mylohyoid line of the mandible and inserts into the hyoid, forming a sling that supports the floor of the mouth. Its contraction elevates the hyoid and floor of the mouth during swallowing and tongue movement.

Question 41Anatomy

The greater palatine foramen transmits which structure?

  1. The nasopalatine nerve
  2. The greater palatine nerve and vessels Correct answer.
  3. The infraorbital nerve
  4. The lesser palatine nerve only

Explanation

The greater palatine foramen lies at the posterior lateral corner of the hard palate and transmits the greater palatine nerve and accompanying vessels. These structures supply the palatal mucosa and gingiva anteriorly.

Question 42Anatomy

Which cranial nerve provides motor innervation to the levator veli palatini?

  1. Glossopharyngeal nerve
  2. Vagus nerve via the pharyngeal plexus Correct answer.
  3. Facial nerve
  4. Trigeminal nerve

Explanation

The levator veli palatini is innervated by the vagus nerve through the pharyngeal plexus, unlike the tensor veli palatini, which is supplied by the trigeminal nerve. This distinction is clinically relevant when assessing palatal function after nerve injury.

Question 43Anatomy

Which of the following best describes the location of the pterygomandibular raphe?

  1. Between the buccinator and superior constrictor muscles Correct answer.
  2. Between the masseter and medial pterygoid muscles
  3. Between the lateral pterygoid and temporalis muscles
  4. Between the digastric and mylohyoid muscles

Explanation

The pterygomandibular raphe is a tendinous band extending from the pterygoid hamulus to the posterior end of the mylohyoid line, where the buccinator and superior constrictor attach. It is an important landmark for the lingual and inferior alveolar nerve blocks.

Question 44Anatomy

Which structure lies immediately deep to the parotid gland and is at risk during parotid surgery?

  1. The inferior alveolar nerve
  2. The facial nerve Correct answer.
  3. The accessory nerve
  4. The hypoglossal nerve

Explanation

The facial nerve courses through the parotid gland, dividing into its temporal, zygomatic, buccal, marginal mandibular, and cervical branches. Because of this intimate relationship, parotid surgery carries a risk of facial palsy.

Question 45Physiology and Pathophysiology

Which structure primarily determines the resting membrane potential of a typical neuron?

  1. Ligand-gated chloride channels at the dendrites
  2. The sodium-potassium pump and potassium leak channels Correct answer.
  3. Voltage-gated calcium channels in the axon terminal
  4. The myelin sheath wrapping the axon

Explanation

Resting membrane potential is set mainly by the concentration gradients maintained by the sodium-potassium ATPase together with the high permeability of potassium leak channels, which makes the membrane potential sit near the potassium equilibrium potential.

Question 46Physiology and Pathophysiology

During the absolute refractory period of a neuron, why can no new action potential be generated?

  1. Sodium channels are inactivated while potassium conductance remains high Correct answer.
  2. Neurotransmitter stores in the terminal are completely depleted
  3. Potassium channels are fully closed and cannot reopen
  4. The membrane is hyperpolarized below threshold by chloride influx

Explanation

The absolute refractory period reflects inactivation of voltage-gated sodium channels after opening, combined with a still-elevated potassium conductance, so no stimulus of any strength can trigger a second spike until channels recover.

Question 47Physiology and Pathophysiology

A patient has a lesion destroying the dorsal columns of the spinal cord on one side. Which sensory finding is most expected?

  1. Loss of fine touch and vibration sense on the same side below the lesion Correct answer.
  2. Loss of pain and temperature sense on the opposite side below the lesion
  3. Loss of pain and temperature sense on the same side below the lesion
  4. Loss of fine touch and vibration sense on the opposite side below the lesion

Explanation

Dorsal column fibers ascend ipsilaterally and cross in the medulla, so a unilateral cord lesion impairs discriminative touch, vibration, and proprioception on the same side below the level of damage.

Question 48Physiology and Pathophysiology

Which change best explains the increased cardiac output during early exercise?

  1. A fall in systemic vascular resistance reducing afterload to near zero
  2. Reduced circulating catecholamines lowering heart rate
  3. Increased parasympathetic outflow to the sinoatrial node
  4. Increased venous return raising stroke volume with sympathetic tachycardia Correct answer.

Explanation

Exercise increases sympathetic activity and venous return through the muscle pump, so heart rate rises and greater preload raises stroke volume, together elevating cardiac output.

Question 49Physiology and Pathophysiology

Which factor most directly increases oxygen unloading from hemoglobin in exercising muscle?

  1. A decrease in local hydrogen ion concentration
  2. A fall in 2,3-diphosphoglycerate within erythrocytes
  3. A rise in local carbon dioxide and temperature shifting the curve right Correct answer.
  4. A rise in blood pH shifting the curve left

Explanation

Active muscle produces carbon dioxide and heat and becomes more acidic, all of which shift the oxyhemoglobin dissociation curve to the right, lowering affinity and enhancing oxygen delivery to tissue.

Question 50Physiology and Pathophysiology

Which renal segment is the primary site of regulated water reabsorption under the influence of antidiuretic hormone?

  1. Bowman capsule
  2. Thick ascending limb of the loop of Henle
  3. Proximal convoluted tubule
  4. Collecting duct Correct answer.

Explanation

Antidiuretic hormone inserts aquaporin-2 channels in the collecting duct, allowing water reabsorption driven by the medullary osmotic gradient and concentrating the urine.