Comparative Muscular System — MCQs
Derivative of the first pharyngeal arch is
What is the anatomical arrangement of fibers in the masseter muscle that contributes to its strength?
After an accident, a patient is unable to close her mouth completely due to certain facial injuries. Which muscle is paralyzed most commonly?
Which type of glial cell is derived from mesodermal origin?
Match the following: A) Glossopharyngeal nerve B) Spinal accessory nerve C) Facial nerve D) Mandibular nerve 1) Shrugging of shoulder 2) Touch sensation from the posterior one-third of the tongue 3) Chewing 4) Taste from the anterior two-thirds of the tongue
The facial nerve supplies motor fibers to which of the following muscles?
Which muscle originates from 1st pharyngeal arch?
Which one of the following tests should be applied to compare mean haemoglobin level of two groups of antenatal mothers?
Malleus and incus are derived from?
Action of the right superior oblique muscle is:
Comparative Muscular System Indian Medical PG Practice Questions and MCQs
Question 1: Derivative of the first pharyngeal arch is
- A. Hyoid
- B. Stapes
- C. Maxilla (Correct Answer)
- D. Laryngeal Cartilage
Explanation: ***Maxilla*** - The **maxilla** is a major component of the upper jaw and midface, and its development is primarily derived from the **first pharyngeal arch** (also known as the mandibular arch). - This arch also gives rise to the mandible, zygomatic bone, and muscles of mastication. *Hyoid* - The **hyoid bone** develops from the **second and third pharyngeal arches**. - Specifically, the lesser horns and superior body of the hyoid are derived from the second arch, while the greater horns and inferior body come from the third arch. *Stapes* - The **stapes**, one of the ossicles of the middle ear, is primarily derived from the **second pharyngeal arch** (hyoid arch). - The malleus and incus, the other two ossicles, are derived from the first pharyngeal arch. *Laryngeal Cartilage* - The cartilages of the larynx (e.g., thyroid, cricoid, arytenoid) are derived from the **fourth and sixth pharyngeal arches**. - These arches also contribute to the development of intrinsic laryngeal muscles and nerves.
Question 2: What is the anatomical arrangement of fibers in the masseter muscle that contributes to its strength?
- A. Bipennate arrangement of fibers
- B. Parallel arrangement with oblique fibers (Correct Answer)
- C. Random arrangement of fibers
- D. Circumpennate arrangement of fibers
Explanation: The original text cannot be accurately cited with the provided references because they do not contain specific information regarding the masseter muscle's anatomical fiber arrangement. ***Parallel arrangement with oblique fibers*** - The **masseter muscle** has a complex arrangement with **parallel fibers running in oblique directions**, which is the key to its strength and power. - The **superficial part** has fibers running **obliquely downward and backward**, while the **deep part** has fibers running more **vertically**. - This arrangement allows the muscle to generate **powerful biting force** by combining multiple fiber orientations, maximizing cross-sectional area and force production. - The masseter is sometimes classified as **multipennate** due to this complex architecture, but the fundamental arrangement is **parallel fibers with oblique orientation**. *Bipennate arrangement of fibers* - A **bipennate arrangement** (like the rectus femoris) has fibers approaching a central tendon from two sides like a feather. - While the masseter is powerful, its fiber arrangement is better described as **oblique parallel** or **multipennate** rather than strictly bipennate. - The masseter's two heads (superficial and deep) have different fiber orientations, which is not characteristic of a simple bipennate muscle. *Random arrangement of fibers* - Skeletal muscles require an **organized fiber arrangement** for effective force transmission. - A **random arrangement** would result in inefficient force generation and poor coordination of muscle contraction. *Circumpennate arrangement of fibers* - **Circumpennate** (or multipennate) arrangement has fibers converging from multiple directions to central tendons, as seen in the **deltoid muscle**. - While some sources describe the masseter as multipennate due to its complex architecture, the more precise anatomical description emphasizes its **parallel fibers with oblique orientation** in distinct superficial and deep parts.
Question 3: After an accident, a patient is unable to close her mouth completely due to certain facial injuries. Which muscle is paralyzed most commonly?
- A. Orbicularis oris (Correct Answer)
- B. Zygomaticus major
- C. Levator anguli oris
- D. Buccinators
Explanation: ***Orbicularis oris*** - The **orbicularis oris** muscle forms a ring around the mouth and is primarily responsible for **closing and protruding the lips**, as well as other facial expressions involving the mouth. - Injury leading to paralysis of this muscle would directly impair the ability to **close the mouth completely** and **seal the lips**. *Zygomaticus major* - The **zygomaticus major** muscle acts to pull the corners of the mouth **upward and laterally**, contributing to smiling. - Its paralysis would affect the ability to smile effectively, but not directly impede the ability to close the mouth. *Levator anguli oris* - The **levator anguli oris** muscle elevates the corner of the mouth (angle of the mouth). - Its dysfunction would impair the ability to raise the corner of the mouth, not the ability to completely close the mouth. *Buccinators* - The **buccinator** muscle is involved in pressing the cheek against the teeth, which helps in chewing, whistling, and sucking. - Paralysis of the buccinator would primarily affect these actions, potentially causing food to pocket in the cheeks, but would not directly prevent mouth closure.
Question 4: Which type of glial cell is derived from mesodermal origin?
- A. Macroglial cells
- B. Microglial cells (Correct Answer)
- C. Oligodendrocytes
- D. Ependymal cells
Explanation: ***Microglial cells*** - **Microglial cells** are unique among glial cells as they originate from **mesoderm**, specifically from **monocyte/macrophage precursors** in the bone marrow [1]. - They function as the **immune cells of the central nervous system (CNS)**, scavenging for plaques, damaged neurons, and infectious agents [1]. *Macroglial cells* - This is a broad category that includes **astrocytes, oligodendrocytes, and ependymal cells**, all of which are derived from **neuroectoderm**, not mesoderm [1]. - They perform various supportive roles but are distinct in origin from microglial cells [1]. *Oligodendrocytes* - **Oligodendrocytes** are derived from **neuroectoderm** and are responsible for forming the **myelin sheath** around axons in the CNS [2]. - Myelination is crucial for rapid and efficient nerve impulse conduction. *Ependymal cells* - **Ependymal cells** are derived from **neuroectoderm** and line the **ventricles of the brain** and the **central canal of the spinal cord**. - They play a role in the production and circulation of **cerebrospinal fluid (CSF)**.
Question 5: Match the following: A) Glossopharyngeal nerve B) Spinal accessory nerve C) Facial nerve D) Mandibular nerve 1) Shrugging of shoulder 2) Touch sensation from the posterior one-third of the tongue 3) Chewing 4) Taste from the anterior two-thirds of the tongue
- A. A-3 , B-1 , C-4 , D-2
- B. A-2 , B-3 , C-4 , D-1
- C. A-4 , B-1 , C-2 , D-3
- D. A-2 , B-1 , C-4 , D-3 (Correct Answer)
Explanation: ***A-2 , B-1 , C-4 , D-3*** - **A) Glossopharyngeal nerve (CN IX)** is responsible for **general sensation and taste from the posterior one-third of the tongue** [1]. (2). - **B) Spinal Accessory nerve (CN XI)** innervates the **sternocleidomastoid** and **trapezius muscles**, which are involved in shrugging the shoulders (1). - **C) Facial nerve (CN VII)** carries **taste sensation from the anterior two-thirds of the tongue** [1] (4) via the chorda tympani. - **D) Mandibular nerve (V3)**, a branch of the trigeminal nerve, innervates the muscles of mastication, enabling **chewing** (3). *A-3 , B-1 , C-4 , D-2* - This option incorrectly associates the **glossopharyngeal nerve** with chewing, which is a function of the mandibular nerve (V3). - It also incorrectly associates the **mandibular nerve** with touch sensation from the posterior one-third of the tongue, which is a function of the glossopharyngeal nerve [1]. *A-2 , B-3 , C-4 , D-1* - This option incorrectly links the **spinal accessory nerve** with chewing; this nerve primarily controls shoulder and neck movements. - It also incorrectly assigns shrugging of the shoulder to the **mandibular nerve** instead of the spinal accessory nerve. *A-4 , B-1 , C-2 , D-3* - This choice incorrectly attributes **taste from the anterior two-thirds of the tongue** to the glossopharyngeal nerve, which supplies the posterior one-third [1]. - It also incorrectly links **touch sensation from the posterior one-third of the tongue** to the facial nerve, which is involved in taste from the anterior two-thirds [1].
Question 6: The facial nerve supplies motor fibers to which of the following muscles?
- A. Stapedius (Correct Answer)
- B. Mylohyoid
- C. Anterior belly of the digastric
- D. Geniohyoid
Explanation: ***Stapedius*** - The **facial nerve (CN VII)** provides motor innervation to the **stapedius muscle**, which plays a role in dampening loud sounds by pulling the stapes away from the oval window. - Dysfunction of this innervation can lead to **hyperacusis** (increased sensitivity to sound). *Mylohyoid* - The **mylohyoid muscle** is innervated by the **nerve to mylohyoid**, which is a branch of the **inferior alveolar nerve** (a branch of the mandibular division of the trigeminal nerve, CN V3). - It forms the floor of the mouth and elevates the **hyoid bone** and tongue during swallowing and speaking. *Anterior belly of the digastric* - The **anterior belly of the digastric muscle** is innervated by the **nerve to mylohyoid**, a branch of the **inferior alveolar nerve** (CN V3). - This muscle helps in depressing the mandible and elevating the hyoid bone. *Geniohyoid* - The **geniohyoid muscle** is innervated by fibers from the **C1 spinal nerve** that travel briefly with the **hypoglossal nerve (CN XII)**. - It elevates and protracts the hyoid bone, aiding in swallowing.
Question 7: Which muscle originates from 1st pharyngeal arch?
- A. Posterior belly of digastric
- B. Buccinator
- C. Masseter (Correct Answer)
- D. Stylopharyngeus
Explanation: ***Masseter*** - The **masseter muscle** is a strong muscle of mastication that originates from the **first pharyngeal arch**. - Muscles derived from the first pharyngeal arch are innervated by the **trigeminal nerve (CN V)**, which also innervates the masseter. *Posterior belly of digastric* - The **posterior belly of the digastric muscle** originates from the **second pharyngeal arch**. - It is innervated by the **facial nerve (CN VII)**, which is associated with the second pharyngeal arch. *Buccinator* - The **buccinator muscle** is a muscle of facial expression that also originates from the **second pharyngeal arch**. - Like other muscles of facial expression, it is innervated by the **facial nerve (CN VII)**. *Stylopharyngeus* - The **stylopharyngeus muscle** originates from the **third pharyngeal arch**. - It is innervated by the **glossopharyngeal nerve (CN IX)**, which is associated with the third pharyngeal arch.
Question 8: Which one of the following tests should be applied to compare mean haemoglobin level of two groups of antenatal mothers?
- A. Analysis of variance
- B. Chi-square test
- C. Unpaired t-test (Correct Answer)
- D. Paired t-test
Explanation: ***Unpaired t-Test*** - The **unpaired t-test** is used to compare the means of **two independent groups** on a continuous variable, such as hemoglobin levels. - Antenatal mothers in two distinct groups are independent, and **hemoglobin level is a continuous variable**, making this the appropriate choice. *Analysis of variance* - **ANOVA** (Analysis of Variance) is used to compare the means of **three or more independent groups**. - Since there are only **two groups** being compared, ANOVA is not the most efficient or appropriate test. *Chi-square test* - The **Chi-square test** is used to analyze the association between **two categorical variables**. - Hemoglobin level is a **continuous variable**, not categorical, so this test is not suitable for comparing means. *Paired t-test* - The **paired t-test** is used to compare the means of **two related groups** or the same group measured at two different times (e.g., before and after an intervention). - The two groups of antenatal mothers are **independent**, not paired or related.
Question 9: Malleus and incus are derived from?
- A. 3rd Arch
- B. 4th Arch
- C. 1st Arch (Correct Answer)
- D. 2nd Arch
Explanation: ***1st Arch*** - The **malleus** and **incus** are ossicles of the middle ear that develop from the **cartilage of the first pharyngeal arch** (Meckel's cartilage). - This arch also contributes to the development of the **mandible** and muscles of mastication. *2nd Arch* - The **second pharyngeal arch** (Reichert's cartilage) gives rise to the **stapes**, a different ossicle of the middle ear. - It also forms the **styloid process**, **lesser cornu of the hyoid**, and muscles of facial expression. *3rd Arch* - The **third pharyngeal arch** contributes to the development of the **greater cornu of the hyoid bone** and the **stylopharyngeus muscle**. - It plays no direct role in the formation of the malleus or incus. *4th Arch* - The **fourth pharyngeal arch** contributes to the formation of the **thyroid cartilage**, **cricoid cartilage**, and muscles of the pharynx and larynx. - It is not involved in the development of the ear ossicles.
Question 10: Action of the right superior oblique muscle is:
- A. Laevoelevation
- B. Laevodepression
- C. Dextroelevation
- D. Dextrodepression (Correct Answer)
Explanation: ***Dextrodepression*** - The **right superior oblique muscle** has three primary actions: **depression** (downward movement), **abduction** (outward/lateral movement), and **intorsion** (internal rotation) [1]. - In the context of conjugate gaze movements, the right superior oblique contributes to **dextrodepression** (downward and rightward gaze) by depressing and abducting the right eye. - When the eye is **adducted** (looking nasally toward the nose), the superior oblique acts as the **primary depressor**, making its depressive action most evident [1]. - The combination of **depression + abduction** of the right eye aligns with the dextrodepression movement pattern [1]. *Laevoelevation* - This refers to upward and leftward gaze movement, which involves **elevation** (not depression). - The right superior oblique is a **depressor**, not an elevator, so it does not contribute to laevoelevation. - This movement is primarily mediated by elevators like the **left inferior oblique** and other elevating muscles [1]. *Laevodepression* - This refers to downward and leftward gaze movement. - While the right superior oblique is a depressor, it causes **abduction** (lateral movement) of the right eye, moving it **rightward/temporally**, not leftward [1]. - Laevodepression is primarily controlled by the **left superior oblique** and other muscles that depress while moving the eyes leftward. *Dextroelevation* - This refers to upward and rightward gaze movement, involving **elevation**. - The right superior oblique is a **depressor**, not an elevator, so it cannot contribute to elevation movements. - This movement is mainly caused by elevating muscles like the **right inferior oblique** [1].
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