Comparative Cardiovascular System — MCQs
The largest component of the total peripheral resistance is due to:
Ductus dependent blood flow is required for all of these congenital heart diseases except:
Which of the following statements is true about the 3rd ventricle?
Sinus venosus receives blood from all EXCEPT:
Arch of Aorta develops from which aortic arch artery?
The right coronary artery supplies all except:
A patient is admitted with a stab wound in the left anterior chest wall in the parasternal line. Which cardiac chamber is most likely to be injured?
Which of the following develops from the part shown as X in the development of heart?
The right coronary artery supplies blood to all of the following structures, except?
Evaluating a neonate with multiple congenital anomalies including cervical fistula draining mucus, thymic hypoplasia, and cardiac outflow tract defects, which phylogenetic developmental process has most likely been disrupted?
Comparative Cardiovascular System Indian Medical PG Practice Questions and MCQs
Question 1: The largest component of the total peripheral resistance is due to:
- A. Venules
- B. Arterioles (Correct Answer)
- C. Capillaries
- D. Precapillary sphincters
Explanation: ***Arterioles*** - **Arterioles** are the primary site of **resistance** in the cardiovascular system due to their relatively small diameter and the significant ability of their **smooth muscle** walls to constrict or dilate. - This resistance plays a crucial role in regulating **blood flow** to various organs and contributes to **mean arterial pressure**. *Venules* - **Venules** are primarily involved in collecting blood from capillaries and have relatively low resistance compared to arteries and arterioles. - While they contribute to capacitance, their impact on **total peripheral resistance** is minimal. *Capillaries* - Although **capillaries** have very small diameters, their sheer number in parallel reduces the overall resistance of the capillary bed. - The primary function of capillaries is **exchange** of nutrients and waste, not primarily resistance. *Precapillary sphincters* - **Precapillary sphincters** control blood flow *into* capillaries from arterioles, acting as gates. - While they regulate flow to specific capillary beds, they are not the largest *component* of total systemic resistance; the **arterioles themselves** are.
Question 2: Ductus dependent blood flow is required for all of these congenital heart diseases except:
- A. Pulmonary stenosis
- B. Persistent truncus arteriosus (Correct Answer)
- C. Hypoplastic left heart syndrome
- D. TGA with intact ventricular septum
Explanation: ***Persistent truncus arteriosus*** - In **persistent truncus arteriosus**, there is a single great artery overriding a ventricular septal defect, supplying both systemic and pulmonary circulation. **Ductus arteriosus** closure does not critically compromise blood flow to either system. - Pulmonary blood flow is often increased in truncus arteriosus, so a patent ductus is not necessary for pulmonary circulation, nor is it essential for systemic circulation as the single trunk directly supplies the aorta. *Pulmonary stenosis* - Severe **pulmonary stenosis** in neonates can restrict blood flow to the lungs, making a **patent ductus arteriosus** essential for pulmonary blood flow via a right-to-left shunt if the stenosis is critical. - Without the **ductus arteriosus**, severe hypoxemia and acidosis can develop due to insufficient oxygenation. *Hypoplastic left heart syndrome* - In **hypoplastic left heart syndrome**, the left ventricle and aorta are underdeveloped, making the **ductus arteriosus** crucial for systemic blood flow from the right ventricle. - Its closure would severely impair blood supply to the body, leading to circulatory collapse and death. *TGA with intact ventricular septum* - With **transposition of the great arteries (TGA)** and an **intact ventricular septum**, systemic and pulmonary circulations are parallel rather than in series. - A **patent ductus arteriosus** is necessary to allow mixing of oxygenated and deoxygenated blood to sustain life.
Question 3: Which of the following statements is true about the 3rd ventricle?
- A. Cavity of the rhombencephalon
- B. Communicates with the 4th ventricle via the aqueduct of Sylvius (Correct Answer)
- C. Communicates exclusively with the lateral ventricles via the foramen of Monro
- D. Interthalamic adhesions connect the lateral walls of the 3rd ventricle
Explanation: ***Communicates with the 4th ventricle via the aqueduct of Sylvius*** - The **aqueduct of Sylvius** (cerebral aqueduct) is the primary channel connecting the third ventricle to the fourth ventricle, allowing for the flow of **cerebrospinal fluid (CSF)** [3]. - This communication is crucial for the continuous circulation of CSF throughout the ventricular system [1]. *Cavity of the rhombencephalon* - The **rhombencephalon** (hindbrain) develops into the pons, cerebellum, and medulla oblongata, and its cavity forms the **fourth ventricle**, not the third. - The **third ventricle** is derived from the **diencephalon**, a part of the prosencephalon (forebrain). *Communicates exclusively with the lateral ventricles via the foramen of Monro* - The **third ventricle** communicates with the **lateral ventricles** via the **foramina of Monro** (interventricular foramina), but this statement is incorrect because it also communicates with the fourth ventricle [2]. - The term "exclusively" makes this option false, as CSF flows from the lateral ventricles, through the third, and then into the fourth ventricle [1]. *Interthalamic adhesions connect the lateral walls of the 3rd ventricle* - The **interthalamic adhesion** (massa intermedia) is a bridge of gray matter that passes through the **third ventricle**, connecting the medial surfaces of the two thalami. - It does not connect the lateral walls, but rather crosses the cavity itself, and its absence does not typically cause neurological deficits.
Question 4: Sinus venosus receives blood from all EXCEPT:
- A. Vitelline vein
- B. Umbilical vein
- C. Common cardinal vein
- D. Subcardinal vein (Correct Answer)
Explanation: Sinus venosus receives blood from all EXCEPT: ***Subcardinal vein*** - The **subcardinal vein** is primarily involved in draining the developing **kidneys** and gonads during embryonic development. - While it contributes to the formation of the **inferior vena cava**, it does not directly empty into the sinus venosus. - The subcardinal veins are part of a different venous drainage system that develops independently from the sinus venosus tributaries. *Vitelline vein* - The **vitelline veins** drain blood from the **yolk sac**, which is the primary site of early hematopoiesis. - These veins directly empty into the **sinus venosus** in the early embryo. - They eventually give rise to the **hepatic portal system** and hepatic sinusoids. *Umbilical vein* - The **umbilical vein** carries **oxygenated and nutrient-rich blood** from the placenta to the fetus [1]. - In the early embryo, the umbilical veins drain directly into the **sinus venosus**. - Later in development, the left umbilical vein bypasses the liver via the **ductus venosus** to enter the inferior vena cava [1], [2]. *Common cardinal vein* - The **common cardinal veins** collect blood from the entire embryo, draining both the anterior (from the cephalic region) and posterior (from the trunk and lower limbs) parts. - These veins represent the main drainage system of the developing embryo and directly empty into the sinus venosus. - They are the primary tributaries of the sinus venosus during early cardiac development.
Question 5: Arch of Aorta develops from which aortic arch artery?
- A. Right 3rd
- B. Left 4th (Correct Answer)
- C. Left 3rd
- D. Right Truncus arteriosus
Explanation: ***Left 4th*** - The **arch of the aorta** develops from the **fourth left aortic arch artery**. [1] - This artery connects the **aortic sac** to the **dorsal aorta** on the left side during embryonic development. *Right Truncus arteriosus* - The **truncus arteriosus** gives rise to the **ascending aorta** and the **pulmonary artery**, not the arch of the aorta. - The term "right truncus arteriosus" is not standard in describing normal aortic arch development. *Right 3rd* - The **third aortic arch arteries** primarily contribute to the development of the **common carotid arteries** and the proximal part of the **internal carotid arteries**. - The right third aortic arch forms the proximal part of the right common carotid artery. *Left 3rd* - The **left third aortic arch artery** forms the proximal part of the **left common carotid artery** and the proximal part of the left internal carotid artery. - It does not directly form the arch of the aorta itself.
Question 6: The right coronary artery supplies all except:
- A. Posterior part of interventricular septum
- B. SA node
- C. Anterior interventricular groove (Correct Answer)
- D. Right atrium
Explanation: ***Anterior interventricular groove*** - The **anterior interventricular groove** contains the **anterior interventricular artery** (also known as the **left anterior descending artery**), which is a branch of the **left coronary artery**. [1] - Therefore, the **right coronary artery does NOT supply** structures located in the anterior interventricular groove. - This is the correct answer for this "except" question. *Posterior part of interventricular septum* - In most individuals (around **85%**), the **right coronary artery** gives rise to the **posterior descending artery (PDA)**. - The PDA supplies the **posterior one-third of the interventricular septum** and the inferior wall of both ventricles. - The RCA **does supply** this structure. *SA node* - The **sinoatrial (SA) node**, the natural pacemaker of the heart, is supplied by the **right coronary artery** in about **60%** of individuals. - In the remaining 40%, it is supplied by the left circumflex artery, but the RCA is the predominant supplier. - The RCA **does supply** this structure in most cases. *Right atrium* - The **right coronary artery (RCA)** gives off branches that supply the **right atrium**. - This is a direct supply that helps maintain the function of the right heart chamber. - The RCA **does supply** this structure.
Question 7: A patient is admitted with a stab wound in the left anterior chest wall in the parasternal line. Which cardiac chamber is most likely to be injured?
- A. Right ventricle (Correct Answer)
- B. Aorta
- C. Left ventricle
- D. Right atrium
Explanation: Right ventricle - The **right ventricle** lies most anteriorly in the chest, directly behind the sternum and ribs, making it the most vulnerable chamber to direct anterior stab wounds [1]. - Its position makes it more susceptible to injury from penetrating trauma to the **parasternal region** [1]. *Aorta* - The **aorta** is located more posteriorly and to the left in the mediastinum, making it less likely to be injured by an anterior stab wound unless the penetrating object is very long and deep. - Injury to the aorta would typically present with more severe and immediate **hemorrhage** and hemodynamic collapse. *Left ventricle* - The **left ventricle** is located more posteriorly and to the left, and is largely covered by the right ventricle, making it less exposed to direct anterior penetrating trauma. - A stab wound would need to be more lateral or deeper to reach the left ventricle directly. *Right atrium* - The **right atrium** is located to the right and superior to the right ventricle, but also somewhat posterior to the most anterior aspect of the right ventricle. - While it can be injured, the right ventricle typically presents the largest surface area directly behind the parasternal area.
Question 8: Which of the following develops from the part shown as X in the development of heart?
- A. Truncus arteriosus (Correct Answer)
- B. Ductus arteriosus
- C. Crista terminalis
- D. Cavo-tricuspid isthmus
Explanation: ***Truncus arteriosus*** - The image shows the primitive heart tube, and **X represents the truncus arteriosus**, which is the **most cranial (superior) part** of the developing heart tube - The truncus arteriosus is a single large arterial trunk that undergoes septation to form the **ascending aorta** and the **pulmonary trunk (pulmonary artery)** - During development, **spiral aorticopulmonary septum** divides the truncus arteriosus into the two great vessels - This occurs during weeks 5-8 of embryonic development *Ductus arteriosus* - The ductus arteriosus is a **fetal blood vessel** that connects the pulmonary artery to the descending aorta, allowing blood to bypass the non-functional fetal lungs - It is **not a segment of the primitive heart tube** but develops separately as part of the 6th pharyngeal arch artery system - It forms after the truncus arteriosus has already divided into the aorta and pulmonary trunk *Crista terminalis* - The crista terminalis is a **ridge in the adult right atrium** that separates the smooth-walled sinus venarum posteriorly from the rough-walled pectinate muscles anteriorly - It is a **morphological feature of the mature heart** that develops from the junction between the sinus venosus and primitive atrium - It does not correspond to the cranial portion of the primitive heart tube (which is the truncus arteriosus) *Cavo-tricuspid isthmus* - The cavo-tricuspid isthmus is a region of the **adult right atrium** located between the inferior vena cava orifice and the tricuspid valve annulus - It is an important **anatomical landmark in cardiac electrophysiology** (target for cavotricuspid isthmus-dependent atrial flutter ablation) - It is a feature of the developed heart and does not represent any segment of the early primitive heart tube
Question 9: The right coronary artery supplies blood to all of the following structures, except?
- A. Posterior wall of left ventricle
- B. SA node
- C. Anterior 2/3 of ventricular septum (Correct Answer)
- D. AV node
Explanation: ***Anterior 2/3 of ventricular septum*** - The **anterior two-thirds of the interventricular septum** is primarily supplied by the **septal branches of the left anterior descending artery** (LAD) [1], a branch of the left coronary artery. - Therefore, the right coronary artery does not typically supply this region. *SA node* - The **SA node** (sinoatrial node) is the heart's natural pacemaker and receives its blood supply from the **right coronary artery** in about 60% of individuals. - Occlusion of the RCA can lead to symptomatic **bradycardia** or **SA node dysfunction**. *AV node* - The **AV node** (atrioventricular node), crucial for coordinating ventricular contraction, is supplied by the **right coronary artery** in approximately 90% of individuals [1]. - Infarcts in the RCA territory can manifest as various degrees of **heart block**. *Posterior wall of left ventricle* - The **posterior wall of the left ventricle** is predominantly supplied by the **posterior descending artery (PDA)**, which in about 80% of people, is a terminal branch of the **right coronary artery** [1]. - This supply is vital for the contractile function of the left ventricle's posterior aspect.
Question 10: Evaluating a neonate with multiple congenital anomalies including cervical fistula draining mucus, thymic hypoplasia, and cardiac outflow tract defects, which phylogenetic developmental process has most likely been disrupted?
- A. Transformation of pharyngeal pouches and neural crest cell migration (Correct Answer)
- B. Rotation and fixation of midgut loop
- C. Fusion of lateral palatine processes with nasal septum
- D. Canalization of the dorsal aorta and vitelline vessels
Explanation: ***Transformation of pharyngeal pouches and neural crest cell migration*** - The clinical presentation of **thymic hypoplasia** and **cardiac outflow tract defects** is characteristic of **DiGeorge syndrome**, which involves failure of the **3rd and 4th pharyngeal pouches** to differentiate. - **Neural crest cells** are essential for the formation of the **conotruncal septum** of the heart; their defective migration leads to both cardiac anomalies and pharyngeal apparatus malformations like **cervical fistulas**. *Rotation and fixation of midgut loop* - This developmental process occurs in the abdomen and is responsible for the proper positioning of the **intestines** and **mesentery**. - Disruption leads to **malrotation** or **volvulus**, but it does not account for thymic, cardiac, or cervical defects. *Fusion of lateral palatine processes with nasal septum* - This process is specific to the formation of the **secondary palate** during the 7th to 12th weeks of gestation. - Failure of this fusion results in **cleft palate**, which, while possibly part of some syndromes, does not explain **thymic hypoplasia** or **outflow tract defects**. *Canalization of the dorsal aorta and vitelline vessels* - This refers to the early formation of the **embryonic circulatory system** and vessels supplying the **yolk sac**. - While vital for vascular development, it is unrelated to the differentiation of **pharyngeal pouch derivatives** or the specific migration of cervical **neural crest cells**.
Want unlimited practice?
Get full access to all questions, explanations, and performance tracking.
Start For Free