GENERAL ANATOMY Flashcards

Question

What is the most commonly fractured facial bone? A. Nasal bone B. Zygomatic process C. Ethmoid bone D. Orbital bone

Answer 1

A. Nasal bone Explanation: The nasal bone is the most commonly fractured facial bone because: - It is prominent and protrudes from the face, making it more vulnerable to trauma. - It is thin and fragile, making it more prone to fractures from direct impact. - It is frequently injured in sports, falls, fights, and car accidents. Why Not the Other Options? ❌ B. Zygomatic process → The zygoma (cheekbone) is commonly fractured but less often than the nasal bone. ❌ C. Ethmoid bone → This is a deeply positioned bone inside the skull, making it less likely to fracture from external trauma. ❌ D. Orbital bone → Orbital fractures occur, but they are less common than nasal fractures.

Answer 2

C. Foramen ovale allows blood to pass primarily from the right atrium to the left atrium Explanation: The fetal circulatory system is unique because the fetus does not use its lungs for oxygen exchange. Instead, oxygenated blood is received from the placenta via the umbilical vein. Three major fetal shunts help bypass the lungs and liver: 1. Foramen ovale → Allows blood to pass from the right atrium to the left atrium, bypassing the non-functional fetal lungs. 2. Ductus arteriosus → Connects the pulmonary artery to the aorta, diverting blood away from the lungs. 3. Ductus venosus → Carries oxygenated blood from the umbilical vein to the inferior vena cava, bypassing the liver. Why Not the Other Options? ❌ A. Ductus venosus carries unoxygenated blood → Incorrect, because the ductus venosus carries oxygenated blood from the placenta to the fetal heart. ❌ B. Ductus arteriosus carries fully oxygenated blood → Incorrect, because the ductus arteriosus carries mixed blood (partially oxygenated). ❌ D. NOTA (None of the Above) → Incorrect, because option C is correct.

Answer 3

D. II, III, IV Explanation: After birth, certain fetal structures close and become ligaments due to the cessation of placental circulation. These ligamentous remnants include: 1. Ligamentum venosum → Remnant of the ductus venosus, which previously bypassed the liver. 2. Ligamentum arteriosum → Remnant of the ductus arteriosus, which connected the pulmonary artery to the aorta. 3. Ligamentum teres of the liver → Remnant of the umbilical vein, which carried oxygenated blood from the placenta. Why Not the Other Options? ❌ I. Ligamentum nuchae → Incorrect, because it is not a fetal remnant but rather a ligament in the neck that provides support. ❌ V. Ligamentum teres of the uterus → Incorrect, because this is not related to fetal circulation but instead a structure in female anatomy that supports the uterus.

Answer 4

C. Veins Explanation: One-way valves in the circulatory system are primarily found in veins. These valves prevent the backflow of blood and ensure that blood flows toward the heart, especially in the lower extremities, where blood must travel against gravity. Why Not the Other Options? ❌ A. Arteries → Incorrect, because arteries do not have valves (except for the aortic and pulmonary valves at the heart). The high pressure in arteries ensures blood flows in one direction. ❌ B. Arterioles → Incorrect, because arterioles regulate blood pressure and flow into capillaries but do not contain valves. ❌ D. Capillaries → Incorrect, because capillaries are tiny blood vessels that allow exchange of oxygen, nutrients, and waste but do not require valves.

Answer 5

C. AB Explanation: Blood type is determined by the ABO blood group system, which is based on the presence of antigens on the surface of red blood cells. - Type A → Has A antigen on red blood cells and anti-B antibodies in plasma. - Type B → Has B antigen on red blood cells and anti-A antibodies in plasma. - Type AB → Has both A and B antigens on red blood cells and no antibodies in plasma. - Type O → Has no A or B antigens on red blood cells but has both anti-A and anti-B antibodies in plasma.

Answer 6

A. VW factor Explanation: - Von Willebrand Factor (vWF) plays a crucial role in platelet adhesion to the exposed subendothelium of damaged blood vessels. - It also stabilizes Factor VIII, which is essential for the clotting cascade. Why not the other options? B. Hageman Factor (Factor XII) → Involved in the intrinsic pathway of coagulation but does not directly mediate platelet aggregation. C. Factor V → Acts as a cofactor in the coagulation cascade, mainly in the conversion of prothrombin to thrombin, but does not play a direct role in platelet aggregation. D. Christmas Factor (Factor IX) → A component of the intrinsic pathway but not directly responsible for platelet adhesion.

Answer 7

D. Calcium Explanation: - Calcium (Ca²⁺) is essential for blood coagulation and is also known as Factor IV in the clotting cascade. - It plays a crucial role in activating various clotting factors and helps in the conversion of prothrombin to thrombin. - It also facilitates platelet aggregation and stabilization of the fibrin clot. Why not the other options? A. Magnesium (Mg²⁺) → Involved in enzymatic reactions but not a clotting factor. B. Sodium (Na⁺) → Important for nerve function and osmotic balance but not involved in coagulation. C. Potassium (K⁺) → Crucial for muscle function and maintaining membrane potential but not a clotting factor.

Answer 8

C. Transport oxygen Explanation: - The most numerous cell in the human body is the red blood cell (RBC), also called an erythrocyte. - Its primary function is to transport oxygen from the lungs to the body's tissues and carry carbon dioxide back to the lungs for exhalation. - This is achieved through hemoglobin, an iron-containing protein that binds to oxygen. Why not the other options? A. Fight infections → This is the function of white blood cells (WBCs), not RBCs. B. Trigger an Ag-Ab complex → This refers to the immune response involving antibodies and antigens, which is a function of B-lymphocytes (a type of WBC). D. Protection from UV rays → Melanocytes in the skin produce melanin, which protects from UV radiation, not RBCs.

Answer 9

A. Lesser palatine artery Explanation: - Epistaxis (nosebleed) commonly results from damage to blood vessels supplying the nasal mucosa, particularly Kiesselbach's plexus (Little's area), which is a vascular network in the anterior part of the nasal septum. The major arteries contributing to epistaxis include: 1. Sphenopalatine artery (branch of maxillary artery) → Main artery supplying the nasal cavity 2. Superior labial artery (branch of facial artery) → Supplies the anterior nasal septum 3. Anterior ethmoidal artery (branch of ophthalmic artery from internal carotid) → Supplies the upper nasal cavity Why is the Lesser Palatine Artery the Exception? - The Lesser Palatine Artery supplies the soft palate and the palatine tonsils, not the nasal mucosa. - Therefore, it is not typically involved in epistaxis.

Answer 10

B. Tunica adventitia Explanation: - Veins have a different wall structure compared to arteries. While arteries have a thicker tunica media (muscular layer) to handle high pressure, veins have a thicker tunica adventitia to provide structural support. - Tunica adventitia (externa) is the outermost layer composed mainly of collagen and elastic fibers, which help prevent overdistension of veins as they carry blood back to the heart under low pressure. - Tunica media is much thinner in veins than in arteries because veins do not need strong muscular walls to regulate blood pressure as arteries do.

Answer 11

C. Albumin Explanation: - Albumin is the most abundant plasma protein, making up about 55-60% of total plasma proteins. It is produced in the liver and plays a crucial role in: - Maintaining oncotic (colloid osmotic) pressure, which helps regulate fluid balance between blood vessels and tissues. - Transporting hormones, fatty acids, and drugs throughout the body. - Acting as a pH buffer to help maintain blood pH levels. Other Plasma Proteins: - Globulins (35-40%) – Involved in immune function (e.g., antibodies). - Fibrinogen (4%) – Essential for blood clotting. - Transport proteins – Includes proteins like transferrin, but they are not as abundant as albumin.

Answer 12

D. The first statement is true, second one is false. Explanation: First Statement: TRUE ✅ - The AV (Atrioventricular) node is a specialized area of conductive tissue located between the atria and ventricles in the heart. - It plays a crucial role in delaying electrical impulses before they pass to the ventricles, ensuring proper timing of heart contractions. Second Statement: FALSE ❌ - The SA (Sinoatrial) node, not the AV node, is the natural pacemaker of the heart. - The SA node initiates the heartbeat and sets the heart rate by generating electrical impulses. - The AV node acts as a relay station, slowing down the impulse before it reaches the ventricles.

Answer 13

D. All of the above Explanation: Sinusoids are specialized, discontinuous capillaries with large lumens and fenestrations, allowing for the passage of blood cells and macromolecules. They are commonly found in: 1. Liver – Sinusoids in the liver facilitate exchange of nutrients, waste, and proteins between the blood and hepatocytes. 2. Spleen – The spleen's sinusoids help in filtering old/damaged red blood cells and play a role in the immune response. 3. Bone marrow – Sinusoids allow newly formed blood cells to enter circulation.

Answer 14

C. Vasa vasorum Explanation: - Vasa vasorum (Latin for "vessels of vessels") are small blood vessels that supply oxygen and nutrients to the walls of large arteries and veins (e.g., aorta, vena cava). - They are necessary because the walls of large vessels are too thick for diffusion alone to provide sufficient oxygen and nutrients. - Vasa vasorum are mainly found in the tunica adventitia of large blood vessels.

Answer 15

A. Epicardium Explanation: - The epicardium is the outermost layer of the heart, also known as the visceral layer of the pericardium. - It contains fat deposits, blood vessels, and nerves that supply the heart. - Fat accumulation in the heart usually occurs in the epicardium, particularly in obese individuals or in conditions like coronary artery disease. - Excessive epicardial fat is associated with an increased risk of cardiovascular diseases.

Answer 16

D. Atrial natriuretic peptide Explanation: - Atrial natriuretic peptide (ANP) is a hormone secreted by the atria of the heart in response to increased blood volume and pressure. It lowers blood pressure by: - Vasodilation (relaxing blood vessels). - Increasing sodium (Na⁺) and water excretion by the kidneys (natriuresis & diuresis). - Inhibiting renin and aldosterone secretion, which helps reduce blood volume. Why the other options are incorrect? A. Renin – Increases blood pressure by activating the renin-angiotensin-aldosterone system (RAAS). B. Angiotensin – Constricts blood vessels, raising blood pressure. C. Serotonin – Functions as a neurotransmitter and vasoconstrictor, but not primarily involved in lowering BP.

Answer 17

C. Lenticulo striae Explanation: - The lenticulostriate arteries are small perforating branches of the middle cerebral artery (MCA). - These arteries supply deep brain structures, including the basal ganglia, internal capsule, and thalamus. - They are particularly prone to damage from hypertension, leading to lacunar infarcts, a common type of stroke in chronic hypertensive patients. - Occlusion or rupture of these vessels can result in lacunar strokes or hypertensive hemorrhages. Why is MCA (Middle Cerebral Artery) also relevant? The MCA is the most common artery involved in ischemic strokes overall, but the lenticulostriate arteries are more specifically affected in small vessel disease and lacunar strokes.

Answer 18

C. 10 days Explanation: - Platelets (Thrombocytes) are anucleate cell fragments derived from megakaryocytes in the bone marrow. - Their primary function is to aid in blood clotting and wound healing. - The normal lifespan of platelets is about 8–10 days in circulation before they are removed by macrophages in the spleen and liver.

Answer 19

A. A group of cell bodies in the CNS Explanation: - In the central nervous system (CNS), a nucleus (plural: nuclei) refers to a cluster of neuronal cell bodies that function together. - In contrast, in the peripheral nervous system (PNS), ganglia are the equivalent structures (a group of cell bodies). - Tracts refer to groups of axons in the CNS, while nerves refer to groups of axons in the PNS.

Answer 20

C. Axonotmesis Explanation: - Axonotmesis is a type of nerve injury where the axon is damaged, but the connective tissue sheaths (endoneurium, perineurium, epineurium) remain intact. This allows for potential regeneration of the nerve. - Neuropraxia (A) – The mildest form of nerve injury where conduction is blocked, but there is no structural damage to the axon. Recovery is complete. - Neurotmesis (B) – The most severe form, where both the axon and connective tissue sheaths are disrupted, leading to irreversible damage unless surgically repaired. - Myelinetmesis (D) – This term is not a recognized classification of nerve injury.

Answer 21

D. Contralateral paralysis Explanation: - The frontal lobe contains the primary motor cortex (precentral gyrus), which controls voluntary movements of the body. - The motor pathways from the brain to the body decussate (cross over) at the medulla, meaning that damage to the right frontal lobe will affect motor function on the left (contralateral) side of the body. - This results in contralateral paralysis (paralysis on the opposite side of the body). Other Options Explained: A. Abnormal pain sensations → Pain perception is processed in the parietal lobe (somatosensory cortex), not the frontal lobe. B. Paresthesia → Paresthesia (tingling, numbness) is due to sensory pathway disruption, which involves the parietal lobe or peripheral nerves. C. Ipsilateral paralysis → This would only happen if the damage were below the level of decussation (e.g., in the spinal cord).

Answer 22

B. Lateral spinothalamic tract Explanation: - The lateral spinothalamic tract is responsible for pain and temperature sensation. - This tract is part of the anterolateral system (ALS) and carries sensory information from the peripheral nervous system to the brain. Pathway of the Lateral Spinothalamic Tract: 1. First-order neurons: Sensory receptors detect pain and temperature and send signals via the dorsal root ganglion (DRG) to the spinal cord. 2. Second-order neurons: Axons decussate (cross over) in the spinal cord at the anterior white commissure and ascend in the contralateral lateral spinothalamic tract to the thalamus. 3. Third-order neurons: The thalamus relays the information to the somatosensory cortex in the parietal lobe for perception. Other Options Explained: A. Tyrosine & D. Phenylalanine → These are amino acids, unrelated to pain and temperature pathways. C. Corticospinal tract → This controls voluntary motor movements, not sensory perception.

Answer 23

D. CN VII Explanation: - The muscle responsible for eye closure is the Orbicularis Oculi. - This muscle is innervated by the Facial Nerve (Cranial Nerve VII). Breakdown of the Options: A. CN VI (Abducens Nerve) → Controls the Lateral Rectus muscle, which moves the eye laterally. B. CN IV (Trochlear Nerve) → Controls the Superior Oblique muscle, which moves the eye down and inward. C. CN III (Oculomotor Nerve) → Controls most of the extraocular muscles for eye movement and eyelid opening (via Levator Palpebrae Superioris) but not eye closure. D. CN VII (Facial Nerve) → Controls Orbicularis Oculi, which is responsible for closing the eyelids.

Answer 24

C. Hypothalamus Explanation: - The hypothalamus is the body's thermoregulatory center. - It maintains body temperature by regulating heat production and heat loss mechanisms. - Antipyretics (like acetaminophen, ibuprofen, and aspirin) lower fever by acting on the hypothalamus to reset the body's temperature set point. Breakdown of the Options: A. Primary Sensory Cortex → Processes sensory information but does not regulate temperature. B. Precentral Gyrus → Contains the primary motor cortex, responsible for voluntary movements. C. Hypothalamus → Regulates body temperature, making it the correct answer. D. Thalamus → Acts as a sensory relay station, but does not control thermoregulation.

Answer 25

A. Loss of taste in anterior two-thirds of the tongue Explanation: The chorda tympani is a branch of the facial nerve (CN VII) that carries special sensory fibers for taste from the anterior two-thirds of the tongue and parasympathetic fibers to the submandibular and sublingual glands. If the chorda tympani is severed, it results in: - Loss of taste in the anterior two-thirds of the tongue (since it carries taste fibers). - Reduced salivation from the submandibular and sublingual glands (due to disruption of parasympathetic innervation). Breakdown of the Other Options: B. Loss of touch sense and taste on the posterior two-thirds of the tongue → Incorrect The glossopharyngeal nerve (CN IX), not the chorda tympani, is responsible for sensation and taste in the posterior two-thirds of the tongue. C. Paralysis of muscles of expression on the same side → Incorrect The facial nerve (CN VII) controls facial expression, but the chorda tympani does not innervate facial muscles. D. Paralysis of muscles of expression on the contralateral side → Incorrect The facial nerve affects the same side (ipsilateral) of the face, but again, the chorda tympani is unrelated to motor function.

Answer 26

B. Inner nerve loop Explanation: - The posterior superior alveolar nerve (PSAN), middle superior alveolar nerve (MSAN), and anterior superior alveolar nerve (ASAN) are branches of the maxillary nerve (V2), a division of the trigeminal nerve (CN V). - These nerves form an interconnected network within the infraorbital and posterior maxillary regions, which is collectively called the Inner Nerve Loop. This network provides sensory innervation to the maxillary sinus, teeth, and gingiva. Breakdown of the Other Options: A. Outer nerve loop → Incorrect This term is not commonly used in anatomy for these nerves. C. Bochdalek ganglion → Incorrect The Bochdalek ganglion is not related to the maxillary nerve; it refers to a sympathetic ganglion near the adrenal glands. D. Valentin ganglion → Incorrect No such ganglion is associated with the maxillary nerve.

Answer 27

A. CN IX and X Explanation: The gag reflex (also called the pharyngeal reflex) is a protective reflex that prevents choking. It involves: - Afferent limb (sensory): Glossopharyngeal nerve (CN IX) detects the stimulus (e.g., touching the posterior pharynx, soft palate, or tonsils). - Efferent limb (motor): Vagus nerve (CN X) triggers the muscular contraction of the pharynx and soft palate to elicit the gag reflex. Thus, both CN IX and CN X are responsible for this reflex.

Answer 28

C. Sarcomere Explanation: A sarcomere is the functional unit of a skeletal muscle fiber, and it extends from one Z disk to the next Z disk. It is the structural and contractile unit responsible for muscle contraction. Here's how the other options relate: A. Sarcolemma – The plasma membrane of a muscle fiber, surrounding the entire cell. B. I band – The light band containing only thin filaments (actin), spanning part of two adjacent sarcomeres. D. A band – The dark band where thick filaments (myosin) are found, including areas where myosin and actin overlap.

Answer 29

B. Mylohyoid muscle Explanation: The mylohyoid muscle acts as a muscular diaphragm that separates the sublingual gland (above it) from the submandibular gland (below it). - The sublingual gland is located superior to the mylohyoid muscle, in the floor of the mouth. - The submandibular gland is positioned inferior to the mylohyoid muscle, in the submandibular triangle. Why not the other options? A. Tongue – Lies above the sublingual gland, but does not separate it from the submandibular gland. C. Inferior border of the mandible – Defines the submandibular triangle but does not physically separate the glands. D. Mental symphysis – The midline junction of the mandible, unrelated to gland separation.

Answer 30

D. Anterior belly of the digastric muscle Explanation: 1. Primary muscle for mouth opening → Lateral Pterygoid - This muscle pulls the mandibular condyle forward and downward, helping in depression of the mandible (mouth opening). - It is the only muscle of mastication that actively opens the mouth. 2. Supporting role → Anterior Belly of the Digastric (D) - The digastric muscle (anterior belly) helps in depressing the mandible (opening the mouth) but is assisted by gravity and the lateral pterygoid. - It is not the primary muscle but works along with the suprahyoid muscles (mylohyoid, geniohyoid) to assist in mouth opening. Why not the other options? Temporalis (B) → Mainly closes the mouth by elevating the mandible. Omohyoid (C) → A neck muscle, not involved in jaw movement.

Answer 31

B. Contralateral movement of the jaw Explanation: - The lateral (external) pterygoid muscle is responsible for protrusion and side-to-side movements of the jaw. - Unilateral contraction (only one side contracts) causes the mandible to move to the opposite (contralateral) side because it pulls the condyle forward and medially on that side. - This is important for grinding movements during chewing. Why not the other options? A. Ipsilateral movement of the jaw → Incorrect, because the contraction pulls the jaw to the opposite side. C. Oblique movement of the jaw → While some oblique motion occurs, the main effect is contralateral movement. D. Protrusion of the jaw → Bilateral contraction (both sides) causes protrusion, but unilateral contraction mainly causes contralateral movement.

Answer 32

A. Triceps brachii Explanation: - The triceps brachii is the primary extensor of the forearm at the elbow joint. - It has three heads (long, lateral, and medial) and is innervated by the radial nerve. - Its main function is to extend the forearm, especially during forceful movements like pushing. Why not the other options? B. Biceps brachii → Incorrect, because it is a flexor, not an extensor. C. Brachialis → Also incorrect, as it is a strong flexor of the forearm. D. Latissimus dorsi → Incorrect, as it mainly functions in shoulder extension, adduction, and medial rotation, not forearm extension.

Answer 33

D. Palatoglossus Explanation: All intrinsic and extrinsic muscles of the tongue are innervated by the hypoglossal nerve (CN XII) except the palatoglossus, which is innervated by the vagus nerve (CN X) via the pharyngeal plexus. Why not the other options? A. Genioglossus → Innervated by CN XII, helps in tongue protrusion. B. Inferior longitudinal → Innervated by CN XII, helps shorten and curl the tongue. C. Superior longitudinal → Innervated by CN XII, helps curl the tongue upward. Mnemonic to remember: "Palatoglossus is special, so it's ruled by the vagus (CN X)!"

Answer 34

A. Parotid gland Explanation: The pterygomandibular space is an important region in dental anesthesia (especially for inferior alveolar nerve blocks). Boundaries of the Pterygomandibular Space: - Anterior → Buccinator muscle - Posterior → Parotid gland (which contains the facial nerve) - Medial → Medial pterygoid muscle - Lateral → Ramus of the mandible - Superior → Lateral pterygoid muscle - Inferior → Attachment of the medial pterygoid to the mandible Why not the other options? B. Buccinator → Forms the anterior boundary of the space. C. Condyle of the mandible → Not a boundary of this space; it is superior to it. D. Lingula → Located on the medial surface of the mandible, near the mandibular foramen, but not a posterior boundary. Clinical Relevance: - The inferior alveolar nerve and lingual nerve pass through this space. - Infection spread (e.g., abscesses from lower molars) can occur here. - Inferior alveolar nerve block is administered in this region.

Answer 35

C. Buccinator Explanation: The pterygomandibular raphe is a fibrous band that connects the buccinator muscle (anteriorly) and the superior pharyngeal constrictor muscle (posteriorly). Anatomy of the Pterygomandibular Raphe - Anterior attachment → Buccinator muscle - Posterior attachment → Superior pharyngeal constrictor muscle - Superior attachment → Pterygoid hamulus of the medial pterygoid plate - Inferior attachment → Retromolar region of the mandible Why is "Buccinator" the correct answer? - The anterolateral portion of the pterygomandibular raphe is where the buccinator muscle originates. - The superior pharyngeal constrictor muscle attaches posteriorly. - The inferior pharyngeal constrictor does not attach to the raphe. - The temporalis muscle is not related to the raphe at all. Clinical Relevance: - The pterygomandibular raphe is an important landmark for the inferior alveolar nerve block in dental anesthesia. - Infections from the buccinator region can spread to the pharyngeal space via this raphe.

Answer 36

D. Lateral - medial Explanation: The masseteric space (submasseteric space) is located between: - The lateral aspect of the mandible - The medial aspect of the masseter muscle This space is important because infections, particularly from mandibular third molars or trauma, can spread here, leading to trismus (difficulty opening the mouth) due to involvement of the masseter muscle.

Answer 37

D. Medial surface of lateral pterygoid plate of sphenoid bone Explanation: The internal pterygoid muscle (also called the medial pterygoid muscle) has its origin from: - Medial surface of the lateral pterygoid plate of the sphenoid bone - Pyramidal process of the palatine bone Function: - Elevates the mandible (helps in closing the mouth) - Protrudes the mandible - Works with the masseter muscle to provide a powerful bite force

Answer 38

C. Vertical Explanation: The intrinsic muscles of the tongue are responsible for changing the shape of the tongue (not its position). These include: 1. Superior longitudinal – curls the tongue upward 2. Inferior longitudinal – curls the tongue downward 3. Transverse – narrows and elongates the tongue 4. Vertical – flattens and broadens the tongue Why the other options are incorrect? A. Genioglossus → Extrinsic muscle (helps protrude the tongue) B. Oblique → No intrinsic tongue muscle named "Oblique" D. Uvula → Not a tongue muscle (part of the soft palate)

Answer 39

D. Sternopharyngeus Explanation: Strap muscles (also called infrahyoid muscles) are a group of muscles in the anterior neck that help depress the hyoid bone and larynx during swallowing and speech. The four strap muscles are: 1. Sternohyoid 2. Omohyoid 3. Sternothyroid 4. Thyrohyoid Why is "Sternopharyngeus" incorrect? There is no muscle named "Sternopharyngeus." The correct name might be referring to the Stylopharyngeus, which is a longitudinal pharyngeal muscle and not a strap muscle.

Answer 40

D. Hyoglossus Explanation: The Hyoglossus muscle is an extrinsic muscle of the tongue that originates from the hyoid bone and inserts into the side of the tongue. Its primary function is to: ✅ Depress (lower) the tongue ✅ Retract the tongue Functions of the Other Muscles: - Genioglossus (A): Protrudes the tongue and depresses the center. - Styloglossus (B): Elevates and retracts the tongue. - Palatoglossus (C): Elevates the back of the tongue and helps in swallowing. So, Hyoglossus is the muscle responsible for inferior movement (depression) of the tongue!

Answer 41

B. Branches of the cervical plexus Explanation: The infrahyoid muscles (also called strap muscles) are: 1. Sternohyoid 2. Omohyoid 3. Sternothyroid 4. Thyrohyoid These muscles primarily function to depress the hyoid bone and larynx during swallowing and speech. 🔹 Motor Innervation: - The ansa cervicalis (a loop from C1-C3 of the cervical plexus) innervates sternohyoid, omohyoid, and sternothyroid. - The thyrohyoid muscle is innervated by C1 fibers traveling with the hypoglossal nerve (CN XII). Why Not the Other Options? ❌ A. Pharyngeal plexus → This mainly innervates the muscles of the pharynx and soft palate, not the infrahyoid muscles. ❌ C. Vagus nerve (CN X) → Vagus nerve controls muscles of the pharynx, larynx, and soft palate, not the infrahyoid muscles. ❌ D. Supraclavicular nerves → These are sensory nerves from C3-C4 that supply the skin over the clavicle, not motor control for muscles.

Answer 42

B. Masticatory mucosa Explanation: The masticatory mucosa lines the areas of the oral cavity that are subject to high friction and mechanical stress, such as: - Gingiva (gums) - Hard palate 🔹 Characteristics of Masticatory Mucosa: - Keratinized or Parakeratinized epithelium (provides resistance to mechanical forces) - Firmly attached to underlying bone - Resistant to abrasion from chewing (mastication) Why Not the Other Options? ❌ A. Lining mucosa → Found in areas with less friction, like the buccal mucosa, lips, soft palate, and ventral tongue. It is non-keratinized and more flexible. ❌ C. Specialized mucosa → Found only on the dorsum (top) of the tongue, containing taste buds. ❌ D. Advanced mucosa → This is not a recognized classification of oral mucosa.

Answer 43

D. Circumvallate Explanation: Circumvallate papillae are responsible for detecting bitter taste and are located at the posterior (back) part of the tongue near the sulcus terminalis. Why Not Fungiform (B)? ❌ Fungiform papillae are located on the tip and sides of the tongue and are responsible for detecting sweet and salty tastes, not bitter. Summary of Taste and Papillae: Filiform → No taste buds, responsible for texture sensation Fungiform → Sweet & salty (tip and sides of the tongue) Foliate → Sour (lateral sides of the tongue) Circumvallate → Bitter (back of the tongue, near sulcus terminalis)

Answer 44

D. Circumvallate Explanation: Circumvallate papillae are: ✔️ The largest papillae on the tongue ✔️ The least numerous (only about 8-12 in number) ✔️ Contain many taste buds, primarily for bitter taste ✔️ Associated with Von Ebner’s glands, which secrete a serous fluid that helps in taste perception and keeps the area clean Why Not the Others? ❌ Foliate (A) → Located on the lateral edges of the tongue, have taste buds, but are not the largest ❌ Filiform (B) → Most numerous but do not have taste buds (used for texture and friction) ❌ Fungiform (C) → Smaller, scattered across the tongue, and responsible for sweet and salty taste

Answer 45

B. Fauces Explanation: The fauces is the passageway that connects the oral cavity to the oropharynx. It is bounded by: ✔️ Palatoglossal arch (anterior pillar) ✔️ Palatopharyngeal arch (posterior pillar) ✔️ The tonsillar fossa, which contains the palatine tonsils Why Not the Others? ❌ Tonsils (A) → These are lymphoid tissues, not a passageway ❌ Oropharynx (C) → This is the region behind the oral cavity but not the passageway itself ❌ Nasopharynx (D) → Located above the soft palate, part of the respiratory tract

Answer 46

A. Palatoglossus and Palatopharyngeus Explanation: The isthmus of the fauces is the opening between the oral cavity and the oropharynx. It is bounded laterally by two muscular arches: 1. Palatoglossal arch (Anterior pillar) → Formed by the Palatoglossus muscle 2. Palatopharyngeal arch (Posterior pillar) → Formed by the Palatopharyngeus muscle These muscles create the lateral boundaries of the isthmus of the fauces. Why Not the Others? ❌ B. Palatoglossus & Tensor Veli Palatini → Tensor Veli Palatini is involved in soft palate movement, not in the fauces. ❌ C. Palatoglossus & Levator Veli Palatini → Levator Veli Palatini elevates the soft palate, but it does not form the lateral boundary. ❌ D. Palatopharyngeus & Medial Pterygoid → Medial Pterygoid is a muscle of mastication, not related to the fauces.

Answer 47

A. Waldeyers Explanation: The Waldeyer's Ring is a ring of lymphoid tissue in the pharynx that forms the first line of defense against airborne and ingested pathogens. It consists of: - Palatine tonsils (on both sides of the oropharynx) - Pharyngeal tonsil (adenoids, located in the nasopharynx) - Tubal tonsils (near the openings of the Eustachian tubes) - Lingual tonsil (on the posterior part of the tongue) - Intervening lymphoid tissue Why Not the Others? ❌ B. Pharyngeal → Refers only to the pharyngeal tonsil (adenoids), not the whole lymphatic ring. ❌ C. Fauces → This is the passageway between the oral cavity and oropharynx, not related to lymphoid tissue. ❌ D. Isthmus → Refers to the isthmus of the fauces, which is the opening between the oral cavity and oropharynx.

Answer 48

C. Parotid Explanation: Mumps is a viral infection (caused by the mumps virus, a paramyxovirus) that primarily affects the parotid glands, leading to parotitis (painful swelling of the parotid glands). Why Not the Others? ❌ A. Submandibular → Less commonly affected by mumps, though theoretically possible. ❌ B. Sublingual → Rarely, if ever, affected in mumps. ❌ D. Von Ebner’s → These are minor salivary glands associated with the circumvallate papillae, not major glands affected by mumps.

Answer 49

D. Parotid gland Explanation: Demilunes of Giannuzzi are crescent-shaped serous cell caps found in mixed salivary glands (glands with both serous and mucous acini). They are mainly present in: - Submandibular gland (A) - Submaxillary gland (B) (alternative name for submandibular) - Sublingual gland (C) However, the parotid gland (D) is a purely serous gland and does not contain demilunes.

Answer 50

C. IgA Explanation: IgA (Immunoglobulin A) is the principal antibody found in exocrine secretions, including: - Saliva - Tears - Mucus (respiratory, gastrointestinal, and urogenital tracts) - Breast milk It plays a crucial role in mucosal immunity, preventing pathogens from attaching to and penetrating epithelial cells. Other Options: IgG (A) – Most abundant in blood; provides long-term immunity. IgE (B) – Involved in allergic reactions. IgD (D) – Role in B cell activation.

Answer 51

B. Caruncle Explanation: The sublingual caruncle is the oral landmark that marks the opening of the submandibular duct (Wharton's duct). It is located on either side of the lingual frenulum on the floor of the mouth. Other Options: - Wharton’s duct (A) – The actual duct of the submandibular gland, but the landmark marking its opening is the caruncle. - Stensen’s duct (C) – The duct of the parotid gland, which opens near the maxillary second molar. - Bartholin’s duct (D) – A minor duct of the sublingual gland, which opens near the submandibular duct.

Answer 52

B. Jejunum Explanation: The jejunum has the most villi and microvilli of all the segments of the small intestine. This adaptation maximizes surface area for nutrient absorption. Other Options: - Duodenum (A): Primarily responsible for digestion and receives secretions from the pancreas and liver, but has fewer villi than the jejunum. - Ilium (C) / Ileum (D): Involved in absorption of bile salts and vitamin B12, but has fewer villi compared to the jejunum.

Answer 53

D. Ileum Explanation: Cyanocobalamin (Vitamin B12) is absorbed in the ileum, but only when bound to intrinsic factor (a glycoprotein secreted by the parietal cells of the stomach). Other Options: - Duodenum (A): Mainly responsible for digesting food and absorbing iron, calcium, and some vitamins. - Jejunum (B): Primary site for nutrient absorption, but not for B12. - Ilium (C) (Incorrect spelling; should be "Ileum"): Likely a misspelling of D. Ileum, which is the correct answer.

Answer 54

B. Duodenum Explanation: Brunner's glands are submucosal glands found exclusively in the duodenum. Their main function is to secrete an alkaline mucus that helps: 1. Neutralize acidic chyme coming from the stomach. 2. Protect the duodenal lining from gastric acid. 3. Provide an optimal pH for digestive enzymes in the small intestine. Why Not the Others? - Stomach (A): Lacks Brunner’s glands; instead, it has gastric glands that produce acid and enzymes. - Jejunum (C): Primarily responsible for nutrient absorption and does not contain Brunner’s glands. - Ileum (D): Mainly involved in B12 and bile salt absorption, without Brunner’s glands.

Answer 55

A. Superior mesenteric vein and the splenic Explanation: The hepatic portal vein is responsible for transporting nutrient-rich blood from the gastrointestinal (GI) tract, pancreas, and spleen to the liver for processing. It is typically formed by the union of: 1. Superior mesenteric vein (SMV) – Drains blood from the small intestine, cecum, ascending colon, and transverse colon. 2. Splenic vein – Drains blood from the spleen, pancreas, and parts of the stomach. 🔹 The inferior mesenteric vein (IMV) usually drains into the splenic vein, rather than directly contributing to the formation of the hepatic portal vein. Why Not the Others? B. Left renal and inferior mesenteric vein: Incorrect—The left renal vein drains the kidney, not the GI tract. C. Inferior vena cava and superior mesenteric vein: Incorrect—The hepatic portal vein drains into the liver, not directly into the inferior vena cava. D. Superior mesenteric vein and inferior mesenteric vein: Incorrect—The inferior mesenteric vein drains into the splenic vein, not directly forming the hepatic portal vein.

Answer 56

A. Endocrine gland Explanation: Endocrine glands are ductless glands that secrete their hormones directly into the bloodstream, where they travel to target organs or tissues. Examples of endocrine glands include: - Pituitary gland (growth hormone, oxytocin) - Thyroid gland (thyroxine) - Adrenal glands (adrenaline, cortisol) - Pancreas (endocrine portion) (insulin, glucagon) Why Not the Others? B. Multicellular gland: This term refers to the structure of a gland, but it does not specify whether it is endocrine or exocrine. C. Exocrine gland: Exocrine glands use ducts to secrete their products (e.g., sweat, saliva, digestive enzymes) onto an epithelial surface rather than into the bloodstream. Examples include the salivary glands, sweat glands, and pancreas (exocrine portion). D. All of the above: Incorrect because only endocrine glands secrete directly into the bloodstream.

Answer 57

A. Pancreas Explanation: The pancreas is the only organ in the body that has both exocrine and endocrine functions. Endocrine Function: 🔹 The Islets of Langerhans secrete hormones directly into the bloodstream: - Insulin (β cells) → Lowers blood sugar - Glucagon (α cells) → Raises blood sugar - Somatostatin (δ cells) → Regulates insulin & glucagon Exocrine Function: 🔹 The pancreatic acini secrete digestive enzymes via ducts into the small intestine (duodenum): - Amylase → Digests carbohydrates - Lipase → Digests fats - Proteases (Trypsin, Chymotrypsin) → Digest proteins Why Not the Others? B. Thyroid → Only endocrine (produces thyroid hormones: T3 & T4) C. Spleen → Not a gland; involved in blood filtration & immune response D. Adrenal gland → Only endocrine (produces cortisol, adrenaline, etc.)

Answer 58

A. Alpha cells Explanation: When blood glucose levels are low, the α (alpha) cells of the pancreas secrete glucagon, which raises blood sugar by stimulating: 🔹 Glycogenolysis – Breakdown of glycogen into glucose (in the liver) 🔹 Gluconeogenesis – Formation of glucose from non-carbohydrate sources 🔹 Lipolysis – Breakdown of fats for energy Why Not the Others? B. Beta cells → Secrete insulin, which lowers blood sugar C. Delta cells → Secrete somatostatin, which regulates α & β cells D. F cells → Secrete pancreatic polypeptide, involved in digestion

Answer 59

D. Adrenalin (also known as epinephrine) Explanation: The adrenal cortex secretes: ✔ Cortisol (a glucocorticoid) → Regulates metabolism & stress response ✔ Aldosterone (a mineralocorticoid) → Regulates sodium & potassium balance ✔ Sex hormones (androgens) → Minor contribution to sex hormone levels However, Adrenalin (epinephrine) is secreted by the adrenal medulla, not the adrenal cortex. The medulla produces catecholamines like epinephrine and norepinephrine, which are involved in the fight-or-flight response.

Answer 60

B. Zona Fasciculata Explanation: The primary stress hormone of the body is cortisol, which is produced by the zona fasciculata of the adrenal cortex. The adrenal cortex has three zones, each producing different hormones: ✔ Zona Glomerulosa → Aldosterone (regulates sodium & potassium balance) ✔ Zona Fasciculata → Cortisol (primary stress hormone, regulates metabolism & immune response) ✔ Zona Reticularis → Androgens (sex hormones) (minor role in male & female sex traits) The adrenal medulla (option D) secretes epinephrine & norepinephrine, which are involved in the fight-or-flight response but NOT the primary stress hormone.

Answer 61

D. Parathyroid Explanation: Oxyphil cells are found in the parathyroid gland. They appear after puberty and increase in number with age. Their exact function is unclear, but they may have a minor role in parathyroid hormone (PTH) secretion. Why not the other options? ❌ A. Pineal body → Contains pinealocytes and glial cells, but no oxyphil cells. ❌ B. Exocrine portion of pancreas → Contains acinar cells, responsible for enzyme secretion, not oxyphil cells. ❌ C. Adrenal medulla → Contains chromaffin cells, which produce epinephrine and norepinephrine, but no oxyphil cells.

Answer 62

C. Squamous Explanation: The urinary bladder is lined by transitional epithelium (urothelium), which is highly stretchable and changes shape depending on the bladder's fullness. - When the bladder is empty → The epithelial cells appear cuboidal. - When the bladder is full → The epithelial cells stretch and appear squamous-like to accommodate the increased volume. Why not the other options? ❌ A. Cuboidal → Found in an empty bladder, not a full one. ❌ B. Columnar → Not found in the bladder; mostly in the intestines and respiratory tract. ❌ D. Smooth → Refers to muscle type, not epithelial lining. Why not A. Cuboidal? - Cuboidal epithelium is seen when the bladder is empty. - When the bladder is full, the cells flatten to squamous-like.

Answer 63

B. Minor calyx Explanation: The renal papilla is the tip of the renal pyramid where urine is discharged from the collecting ducts into the minor calyx. Urine Flow Pathway in the Kidney: 1. Renal papilla → 2. Minor calyx → 3. Major calyx → 4. Renal pelvis → 5. Ureter → 6. Bladder Why not the other options? A. Ureter → The renal papilla does not project directly into the ureter; urine must first pass through the calyces and renal pelvis. C. Major calyx → The minor calyces drain into the major calyces, not directly into the renal papilla. D. Renal pelvis → The major calyces drain into the renal pelvis, but the renal papilla does not directly connect to it.

Answer 64

D. Macula Densa Explanation: The macula densa is a specialized group of epithelial cells located in the distal convoluted tubule (DCT) near the glomerulus. These cells monitor sodium (Na⁺) concentration in the filtrate and help regulate glomerular filtration rate (GFR) through the tubuloglomerular feedback mechanism. How It Works: If Na⁺ levels are high, macula densa cells signal the afferent arteriole to constrict, reducing GFR. If Na⁺ levels are low, they stimulate juxtaglomerular cells to release renin, leading to angiotensin II formation, which increases blood pressure and sodium reabsorption. Other Options Explained: ❌ A. Juxtaglomerular cells – These secrete renin, but they don’t directly detect sodium concentration. ❌ B. Renin – This is an enzyme, not a cell, and it regulates blood pressure but doesn't sense Na⁺. ❌ C. Goblet cells – These are mucus-secreting cells found in the respiratory and gastrointestinal tracts, not the kidneys.

Answer 65

B. Henle's loop Explanation: The highest osmolality (most concentrated filtrate) occurs at the bottom of the loop of Henle because: 1. Descending limb: Permeable to water but impermeable to solutes, causing water to exit into the hypertonic medullary interstitium. This increases osmolality. 2. Ascending limb: Impermeable to water but actively pumps out Na⁺, K⁺, and Cl⁻, making the fluid more dilute as it moves up. Why Not the Distal Tubules? - The distal tubule has the lowest osmolality (~100 mOsm/L) because it actively reabsorbs NaCl but is impermeable to water in its early segment. - If ADH is present, water permeability increases in the late distal tubule and collecting ducts, but osmolality still won’t reach the peak seen at the bottom of the loop of Henle. Other Options Explained: ❌ A. Bowman's capsule – The osmolality of filtrate here is similar to plasma (~300 mOsm/L), as no concentration changes have occurred yet. ❌ C. Proximal tubule – While ~65% of filtrate is reabsorbed here, osmolality remains isotonic (~300 mOsm/L) because water follows solute reabsorption. ❌ D. Distal tubules – Fluid here is hypotonic (~100 mOsm/L) due to active Na⁺ reabsorption and impermeability to water in the early distal tubule.

Answer 66

C. Membranous urethra Explanation: The membranous urethra is the shortest and least distensible (least flexible) portion of the male urethra because: 1. It passes through the urogenital diaphragm, which contains the external urethral sphincter (a voluntary muscle). 2. It is surrounded by dense connective tissue, making it less flexible compared to the spongy (penile) urethra. Other Urethral Segments: - Prostatic urethra: The widest part, located inside the prostate gland. - Membranous urethra: Shortest and least distensible, passes through the urogenital diaphragm. - Spongy (penile) urethra: Longest and most flexible, runs through the corpus spongiosum in the penis.

Answer 67

B. Epididymis Explanation: The epididymis is the storage site for mature sperm cells before they are transported through the vas deferens during ejaculation. Functions of the Epididymis: 1. Sperm maturation: Sperm gain motility and fertilization ability. 2. Storage of mature sperm: Until ejaculation occurs. 3. Transport: Moves sperm to the vas deferens. Mature sperm cells are stored in the epididymis, a coiled tube located at the back of each testicle. The epididymis plays a crucial role in sperm maturation, storage, and transport before ejaculation. Why Not the Other Options? A. Seminal vesicles → ❌ Incorrect They produce seminal fluid that nourishes sperm but do not store sperm. C. Testes → ❌ Incorrect The testes produce sperm but do not store mature sperm. D. Scrotum → ❌ Incorrect The scrotum is a protective sac that holds the testes but does not store sperm.

Answer 68

B. Acrosome Explanation: The acrosome is a specialized cap-like structure at the head of the sperm. It contains enzymes (such as hyaluronidase and acrosin) that help the sperm penetrate the zona pellucida, the protective outer layer of the egg. This process is called the acrosome reaction, allowing fertilization to occur. Why Not the Other Options? A. Midpiece of the tail → ❌ Incorrect The midpiece contains mitochondria that produce energy (ATP) for sperm motility but does not help in egg penetration. C. Chemotactor → ❌ Incorrect No such structure exists. However, chemotaxis is a process where sperm moves toward the egg due to chemical signals. D. Flagella → ❌ Incorrect The flagella (tail) provides movement to the sperm but does not help in egg penetration.

Answer 69

A. Prostate gland Explanation: The prostate gland is located at the neck of the urinary bladder in males. It surrounds the prostatic urethra and secretes a milky fluid that contributes to semen. Why Not the Other Options? B. Cowper’s gland (Bulbourethral gland) → ❌ Incorrect Located below the prostate, near the membranous urethra, and secretes pre-ejaculatory fluid for lubrication. C. Cervical gland → ❌ Incorrect Found in the cervix of the uterus (female reproductive system), not related to the urinary bladder. D. Corpora cavernosa → ❌ Incorrect These are erectile tissues in the penis, not glands.

Answer 70

B. Cochlea Explanation: The cochlea is the spiral-shaped structure of the inner ear responsible for hearing. It contains two key membranes: 1. Vestibular membrane (Reissner’s membrane) → Separates the scala vestibuli from the scala media. 2. Basilar membrane → Supports the Organ of Corti, which contains hair cells that detect sound vibrations and convert them into nerve impulses. Why Not the Other Options? A. Semicircular canals → ❌ Incorrect Responsible for balance and detecting head movements, not hearing. C. Auditory tube (Eustachian tube) → ❌ Incorrect Connects the middle ear to the throat to equalize pressure, but does not play a direct role in hearing. D. Vestibule → ❌ Incorrect Contains the utricle and saccule, which are responsible for static equilibrium and detecting gravity, not hearing.

Answer 71

C. Iris Explanation: The iris is the colored part of the eye that controls the size of the pupil. It contains smooth muscles that adjust pupil size in response to light intensity: - In bright light → The circular muscles contract, making the pupil smaller (miosis). - In dim light → The radial muscles contract, making the pupil larger (mydriasis). Why Not the Other Options? A. Cornea → ❌ Incorrect The cornea is the transparent outer layer of the eye that helps focus light, but it does not control pupil size. B. Sclera → ❌ Incorrect The sclera is the white part of the eye that provides structural support but has no role in pupil control. D. Retina → ❌ Incorrect The retina contains photoreceptors (rods & cones) that detect light and send signals to the brain, but it does not control the pupil.

Answer 72

D. Optic disc Explanation: The optic disc (also called the blind spot) is the part of the retina where the optic nerve exits the eye. It contains no photoreceptors (no rods or cones), which means that no visual information is processed in this area. Why Not the Other Options? A. Fovea centralis → Has the highest concentration of cones, providing sharp central vision. B. Macula lutea → Contains both rods and cones, responsible for detailed and color vision. C. Ishihara's area → Not an actual anatomical part of the eye; Ishihara refers to a color vision test.

Answer 73

D. Coopers ligament Explanation: Cooper's ligaments (also called the suspensory ligaments of the breast) are fibrous connective tissue bands that extend from the skin to the deep fascia overlying the pectoral muscles. These ligaments provide structural support to the breast and help maintain its shape, preventing sagging (ptosis) over time. Why Not the Other Options? A. Broad ligament → Supports the uterus, fallopian tubes, and ovaries in females. ❌ B. Mammalian ligament → Not a recognized anatomical term. ❌ C. Mesovarium → Part of the broad ligament that supports the ovary. ❌

Answer 74

C. Isthmus Explanation: The isthmus is the narrowest portion of the oviduct (fallopian tube). It is a short, thick-walled segment that connects the ampulla to the uterus. Why Not the Other Options? A. Ampulla of oviduct → The widest and longest part of the fallopian tube, where fertilization usually occurs. ❌ B. Infundibulum → The funnel-shaped distal part with fimbriae that captures the ovulated egg. ❌ D. Ciliated → This is not a structural part but refers to the ciliated epithelium that helps move the egg toward the uterus. ❌

Answer 75

A. Parotid lymph node Explanation: The parotid lymph nodes (also called preauricular lymph nodes) receive lymph drainage from: - A strip above the parotid salivary gland - The anterior wall of the external auditory meatus - Lateral parts of the eyelids These nodes are located near the parotid gland and help filter lymph from surrounding structures. Why Not the Other Options? B. Submandibular lymph node → Drains lymph from the face, floor of the mouth, tongue, and submandibular gland. Does not primarily receive drainage from the external auditory meatus or eyelids. ❌ C. Submental lymph node → Drains the chin, tip of the tongue, and lower lip. Not related to the auditory meatus or eyelids. ❌ D. Supramental lymph node → This is not a recognized anatomical term for a lymph node. ❌

Answer 76

D. Terminal bronchioles Explanation: - Terminal bronchioles are the last portion of the conducting zone in the respiratory system. - They lead to the respiratory bronchioles, which are the first part of the respiratory zone where gas exchange begins. Why Not the Other Options? A. Respiratory bronchioles → These belong to the respiratory zone, not the conducting zone. ❌ B. Bronchi → Larger airways that branch into bronchioles, but not the last part of the conducting pathway. ❌ C. Primary bronchioles → There is no such specific term; the correct term would be primary bronchi or just bronchioles. ❌