[UHS-2024]
Bone forming cells are:
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept:The life cycle and function of bone cells.
Formula:N/A (Conceptual)
Solution:- Bone remodeling relies on a balance of building and destroying tissue.
- The specialized cells tasked strictly with synthesizing and secreting the new unmineralized bone matrix (osteoid) are the Osteoblasts (remember: B for Builder).
Why other options are incorrect:Osteoclasts (
C for Consumer/Crusher) break down bone. Osteocytes are mature, resting cells. Osteons are the massive structural cylindrical units of compact bone, not individual cells.
[KMU-2024]
The cells contained in the lacunae of the bone are called:
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Anatomy of the Haversian system.
Formula:N/A (Conceptual)
Solution:- Once active osteoblasts secrete enough matrix to completely surround and trap themselves, the matrix calcifies and hardens.
- The trapped cells mature into Osteocytes, which permanently reside inside these tiny bony chambers known as lacunae. They maintain local bone metabolism.
Why other options are incorrect:Chondrocytes reside in the lacunae of
cartilage, not bone. Osteoblasts and osteoclasts operate directly on the outer surfaces of the bone tissue, not inside trapped internal lacunae.
[UHS-2024]
Which feature is possessed by smooth muscles?
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Histological characteristics of smooth muscle.
Formula:N/A (Conceptual)
Solution:- Smooth muscle cells line internal organs (like the gut and blood vessels) and act entirely involuntarily.
- Under a microscope, they appear as isolated, non-striated, spindle-shaped cells. Unlike fused skeletal fibers, each individual smooth muscle cell possesses exactly one central nucleus, making them definitively Uni-nucleate.
Why other options are incorrect:They are strictly involuntary (not voluntary). They are spindle-shaped (not branched like cardiac cells). They lack sarcomeres entirely, meaning they have no striated appearance.
[KMU-2024]
Which of the following does NOT relate to smooth muscles?
A
Controlled by the autonomic nervous system
B
Have spindle shaped cells
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Anatomical placement of muscle tissue types.
Formula:N/A (Conceptual)
Solution:- Smooth muscles are spindle-shaped, unstriated, and involuntarily controlled by the autonomic nervous system.
- However, smooth muscle does NOT line the walls of the heart. The muscular layer of the heart (the myocardium) is composed exclusively of specialized cardiac muscle tissue, which is structurally distinct and highly adapted for relentless, autonomous rhythmic pumping.
Why other options are incorrect:Options A, B, and D are perfectly accurate, defining physiological characteristics of smooth muscle.
[KMU-2024]
The ____ surrounds the muscle fibre of the skeletal muscle.
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:Outer boundary terminology of muscle cells.
Formula:N/A (Conceptual)
Solution:- A skeletal muscle fiber is simply a single, massive, elongated muscle cell.
- Like all cells, it requires an outer plasma membrane to separate its interior from the extracellular environment and to conduct electrical impulses.
- In muscle biology, this specialized surrounding membrane is universally termed the Sarcolemma.
Why other options are incorrect:Myofibrils are the internal contractile rods. Cytoplasm (sarcoplasm) is the fluid inside. Lacunae are the bone/cartilage cavities.
[UHS-2024]
Thick filaments in skeletal muscles are composed of:
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Protein composition of sarcomere filaments.
Formula:N/A (Conceptual)
Solution:- The sarcomere relies on the interaction between two primary filament types to contract: thin and thick.
- The thick filaments are extremely dense and are constructed entirely from hundreds of individual Myosin molecules, bound together with their globular heads protruding outward to grab the thin filaments.
Why other options are incorrect:Actin is the primary structural protein of the
thin filaments. Tropomyosin and Troponin are regulatory proteins intimately wrapped around the thin actin filaments, not the thick ones.
[UHS-2024]
The accumulation of 'lactic acid' in the muscles results in:
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept:Metabolic consequences of anaerobic respiration.
Formula:N/A (Conceptual)
Solution:- When strenuous exercise outpaces oxygen delivery, muscle cells resort to anaerobic glycolysis to generate emergency ATP.
- This process rapidly produces a highly acidic byproduct: lactic acid.
- The buildup of lactic acid violently drops the intracellular pH, directly interfering with enzyme activity and calcium binding, forcing the muscle to lose its ability to contract efficiently. This state is known as Extreme fatigue.
Why other options are incorrect:Lactic acid inherently
hinders further muscle contraction; it does not cause it. It causes severe burning and exhaustion, but not total neurological paralysis or systemic convulsions.
[UHS-2024]
Sarcomere is part of myofibril between:
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:Anatomical boundaries of the contractile unit.
Formula:N/A (Conceptual)
Solution:- The skeletal muscle myofibril is a long chain of repeating structural units called sarcomeres.
- By strict biological definition, exactly one single functional sarcomere is the highly organized region extending exactly from one Z line (or Z disc) to the very next adjacent Z line.
Why other options are incorrect:The M-line marks the exact center, not the boundary. A-bands and I-bands represent thick filament length and thin filament isolation, respectively, but do not serve as structural dividing borders.
[KMU-2024]
What happens to calcium when skeletal muscles recover from contraction?
A
Released from the sarcoplasmic reticulum
B
Released from the myosin head
C
Pumped into the sarcoplasmic reticulum
D
Exchanged for sodium ions
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Termination of the excitation-contraction coupling.
Formula:N/A (Conceptual)
Solution:- For a contracted muscle to safely relax and recover, the internal signal to contract (high cytosolic Calcium) must be rapidly removed.
- To achieve this, high-affinity, ATP-driven Calcium pumps immediately engage, aggressively vacuuming the \(Ca^{2+}\) off the troponin molecules and actively pumping it back into the sarcoplasmic reticulum for safe storage until the next nerve impulse arrives.
Why other options are incorrect:Releasing calcium
from the SR
causes contraction. Calcium never binds to the myosin head (it binds troponin). Exchanging it for sodium is part of cardiac regulation, not the primary skeletal muscle relaxation mechanism.
[NUMS-2024]
Choose the correct, for muscle in relaxed position:
A
Exposed binding sites on actin
B
Broad H-zone in sarcomere
C
Formation of cross bridges
D
\(Ca^{2+}\) released in cytosol
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Sarcomere state prior to nervous stimulation.
Formula:N/A (Conceptual)
Solution:- In a completely relaxed muscle, no calcium is present in the cytosol, and tropomyosin is actively blocking the actin binding sites, meaning zero cross-bridges can form.
- Because the thin filaments have slid back out and are resting far apart from the center line, the central gap containing only thick filaments (the H-zone) is extremely wide and broad.
Why other options are incorrect:Options A, C, and D are all definitive physiological markers of a muscle that is actively
contracting, not relaxing.
[UHS-2024]
Which of the following skeletal disorder is an example of autoimmune disorder?
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Etiology of skeletal pathologies.
Formula:N/A (Conceptual)
Solution:- An autoimmune disorder occurs when the body's own white blood cells tragically misidentify healthy host tissue as a foreign invader and attack it.
- Rheumatoid arthritis is a classic systemic autoimmune disease where the immune system violently attacks the synovial membranes of joints, leading to massive inflammation, pain, and eventual joint destruction.
Why other options are incorrect:Sciatica is mechanical nerve compression. Spondylosis is age-related wear-and-tear degeneration of the spine. Rickets is a severe nutritional deficiency (Vitamin D/Calcium) in children.
[UHS-2024]
Which of the following is NOT a bone of upper limb?
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Appendicular skeleton layout.
Formula:N/A (Conceptual)
Solution:- The upper limb consists of the arm and forearm, containing bones perfectly adapted for high dexterity and reach.
- These include the humerus (upper arm) and the radius/ulna pair (forearm).
- The Femur, however, is the massive, heavy thigh bone. It is strictly part of the lower limb, designed for immense weight-bearing and locomotion.
Why other options are incorrect:Options A, B, and D all correctly identify major long bones situated within the human arm.
[NUMS-2024]
You must have often heard about the hamstring injury of players. Which of the following is correct about hamstring muscles?
A
It is an extensive muscle
B
Its insertion is on tibia
C
Originate from pelvic girdle and top of femur
D
Originate from ilium and femur
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Anatomy and attachments of the posterior thigh compartment.
Formula:N/A (Conceptual)
Solution:- The hamstrings are a massive, powerful group of three muscles (semimembranosus, semitendinosus, and biceps femoris) located on the back of the thigh.
- They originate high up on the ischial tuberosity of the pelvis.
- To fulfill their primary function of forcefully bending the knee during running, their long tendons must cross the knee joint and firmly anchor downward. Their insertion is primarily on the tibia (with biceps femoris inserting on the adjacent fibula).
Why other options are incorrect:They do not originate from the ilium or the top of the femur. 'Extensive muscle' is vague and non-anatomical. The specific, biomechanically defining feature listed is their tibial insertion point across the knee.
[UHS-2023]
Cartilage is a type of which tissue?
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept:Basic tissue classifications.
Formula:N/A (Conceptual)
Solution:- Tissues are grouped into four main categories.
- Because cartilage consists of widely spaced cells (chondrocytes) suspended within a dense, structural extracellular matrix (collagen and proteoglycans), it perfectly fits the definition of a connective tissue.
Why other options are incorrect:Epithelial tissue lines surfaces. Muscular tissue is contractile. Nervous tissue conducts electrical impulses. None of these describe a structural, matrix-heavy support tissue.
[ETEA-2023]
Which of the following connective tissues consists of cells known as chondrocytes:
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Cell nomenclature based on tissue type.
Formula:N/A (Conceptual)
Solution:- The biological prefix chondro- universally refers to cartilage.
- Therefore, chondrocytes are specifically the mature, maintaining cells embedded in the lacunae of cartilage tissue.
Why other options are incorrect:Bone cells are called osteocytes/osteoblasts. Myocardium cells are cardiomyocytes. The periosteum is a fibrous membrane.
#16 of 63
ETEA-2023 Retake
[ETEA-2023 Retake]
Hip joint and shoulder joint are example of:
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:Functional classifications of highly mobile synovial joints.
Formula:N/A (Conceptual)
Solution:- The hip and shoulder require extreme mobility, allowing for flexion, extension, abduction, adduction, and full circumduction.
- This 360-degree, multi-axial freedom is strictly facilitated by a spherical bone head fitting into a cup-like depression, mechanically defining a ball and socket joint.
Why other options are incorrect:While they
are technically synovial joints, 'ball and socket' is the highly specific and exact answer required for this joint class. Hinge joints (elbow) restrict movement to one plane.
[NUMS-2023]
Cartilage is more difficult to heal than bone because cartilage:
B
Lacks minerals deposits in matrix
C
Has less number of cells deep down
D
Lacks protein in matrix
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept:Tissue regeneration dependencies.
Formula:N/A (Conceptual)
Solution:- Tissue healing relies strictly on the rapid delivery of immune cells, oxygen, and nutrients to the site of damage.
- Unlike highly vascularized bone, cartilage is essentially avascular (lacks direct blood vessels).
- Consequently, repair materials must slowly percolate through the dense matrix via diffusion, making cartilage healing notoriously sluggish or completely ineffective.
Why other options are incorrect:Cartilage contains abundant proteins (collagen/elastin). While it lacks mineral deposits (calcium), that factor contributes to its flexibility, not its inability to heal.
#18 of 63
ETEA-2023 Retake
[ETEA-2023 Retake]
Which cartilage is found at the end of long bones?
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:Anatomical distribution of cartilage types.
Formula:N/A (Conceptual)
Solution:- To prevent bone-on-bone friction at movable joints, the articulating surfaces of long bones are capped with a glassy, smooth, friction-reducing layer.
- This specific layer is composed entirely of hyaline cartilage, earning it the alternative name 'articular cartilage'.
Why other options are incorrect:Elastic cartilage is in the ear. Fibrous cartilage is found in high-compression areas like intervertebral discs. Calcified cartilage is an intermediate stage in bone formation.
[SZABMU-2023]
Mature bone cells are called:
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Bone cell life cycle nomenclature.
Formula:N/A (Conceptual)
Solution:- The prefix osteo- signifies bone.
- Osteoblasts actively secrete new matrix. Once they become permanently trapped within the hardened lacunae of their own making, they mature into resting osteocytes, which simply maintain the surrounding matrix.
Why other options are incorrect:Osteoclasts are massive, multi-nucleated macrophage derivatives that dissolve bone. Chondrocytes are cartilage cells.
[UHS-2023]
Irregular striations and involuntary control is related to?
B
Fibroelastic cartilage cell
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept:Identifying muscle types by their microscopic appearance and nervous control.
Formula:N/A (Conceptual)
Solution:- We must satisfy two constraints: It must be striated, and it must be involuntary.
- Skeletal muscle is striated but completely voluntary. Smooth muscle is involuntary but entirely lacks striations.
- Cardiac muscle perfectly fits both criteria: it possesses irregular branching striations and operates autonomously via involuntary autonomic control.
Why other options are incorrect:Smooth muscle lacks striations entirely. Skeletal muscle is voluntary. Cartilage is not a contractile muscle tissue.
[SZABMU-2023]
Which feature is possessed by smooth muscles?
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Histological features of smooth muscle.
Formula:N/A (Conceptual)
Solution:- Unlike skeletal muscles which form massive syncytia, smooth muscle cells exist as distinct, individual, spindle-shaped units.
- Each of these individual cells contains strictly one central nucleus, making them uninucleate.
Why other options are incorrect:Smooth muscles uniquely lack highly organized sarcomeres, hence they do not possess a striated appearance. They are never multinucleate.
[NUMS-2023]
Which feature is absent in cardiac muscles?
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Differentiating cardiac vs. skeletal muscle.
Formula:N/A (Conceptual)
Solution:- Cardiac muscles are highly specialized, branching cells linked by intercalated discs. They contain sarcomeres resulting in light and dark bands (striations).
- However, unlike skeletal muscles which fuse into massive fibers with hundreds of nuclei, cardiac muscle cells are almost always distinctly uninucleate (or occasionally binucleate). Thus, the classic multinucleated state is considered absent.
Why other options are incorrect:Intercalated discs, sarcomeres, and distinct banding patterns are all hallmark, highly visible features of cardiac tissue.
[UHS-2023]
The cell membrane of muscle cell is:
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Muscle cell anatomy and prefixes.
Formula:N/A (Conceptual)
Solution:- In muscle histology, the prefix sarco- (flesh) replaces standard cell prefixes.
- The suffix -lemma means husk or sheath. Therefore, the specialized excitable plasma membrane wrapping the muscle cell is universally known as the sarcolemma.
Why other options are incorrect:Sarcoplasm is the interior cytoplasm. A sarcomere is the internal contractile unit. Myofibrils are the long protein cords inside the cell.
[SZABMU-2023]
What do we call the cell surface membrane of a muscle fibre?
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept:Specific muscle terminology.
Formula:N/A (Conceptual)
Solution:- While it functions fundamentally as a phospholipid bilayer plasma membrane, the strict anatomical term dedicated to muscle fibers is the sarcolemma.
- It is highly specialized to plunge into the cell via T-tubules to quickly conduct electrical action potentials.
Why other options are incorrect:Sarcoplasm refers to the fluid interior. 'Plasma membrane' is a generic term lacking the required muscle-specific specificity.
[ETEA-2023]
A sarcomere is the region of a myofibril between two successive:
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Anatomical boundaries of the contractile unit.
Formula:N/A (Conceptual)
Solution:- A myofibril consists of repeating sub-units called sarcomeres.
- The distinct, zig-zag structural proteins that physically anchor the thin actin filaments mark the outer boundaries of these units.
- The space situated strictly between two adjacent Z-lines (or Z-discs) defines exactly one functional sarcomere.
Why other options are incorrect:M-lines anchor myosin in the exact center of the sarcomere. A-bands and I-bands represent wide regions of overlapping or isolated proteins, not boundary lines.
#26 of 63
ETEA-2023 Retake
[ETEA-2023 Retake]
How many actin filaments surround the myosin at each end?
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Cross-sectional lattice geometry of the sarcomere.
Formula:N/A (Conceptual)
Solution:- To maximize contraction force, thick and thin filaments are tightly packed into a crystalline lattice.
- In vertebrate skeletal muscle, taking a slice through the zone of overlap reveals a hexagonal arrangement.
- Exactly 6 thin actin filaments geometrically surround every single thick myosin filament.
Why other options are incorrect:The geometry strictly dictates a hexagon (6). Any other number would result in inefficient structural gaps or impossible protein binding angles.
[UHS-2023]
During sliding of actin filaments, ATP is used for?
D
Shortening of filaments
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:The role of ATP in the cross-bridge cycle.
Formula:N/A (Conceptual)
Solution:- Counterintuitively, myosin physically binds to actin spontaneously when calcium exposes the binding sites; this initial attachment does not require new ATP.
- The 'power stroke' (dragging) is powered by the release of stored ADP and Phosphate.
- However, for the myosin head to physically detach and let go of the actin filament, a fresh molecule of ATP must physically bind to it. Thus, ATP is strictly required for cross bridge breaking.
Why other options are incorrect:Without ATP, cross bridges lock permanently (causing Rigor Mortis). Filaments themselves never shorten; they only slide.
[ETEA-2023]
According to sliding filament hypothesis, the release of ____ ions from the sarcoplasmic reticulum causes the reorientation of certain components in thin filament, permitting them to bind with extensions from the thick myosin filaments:
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Excitation-contraction chemical triggers.
Formula:N/A (Conceptual)
Solution:- The sarcoplasmic reticulum is a specialized organelle designed to aggressively pump and store large quantities of Calcium ions (Ca\(^{2+}\)).
- When an action potential arrives, gated channels open, flooding the sarcoplasm with Calcium.
- This Calcium physically binds to troponin, causing a massive structural shift that moves tropomyosin out of the way, exposing actin to myosin.
Why other options are incorrect:Sodium and Potassium are strictly responsible for conducting the electrical action potential along the membrane, but they do not interact directly with the internal contractile proteins.
#29 of 63
ETEA-2023 Retake
[ETEA-2023 Retake]
Muscle fatigue results due to deficiency of ____ and excess accumulation of ____.
A
Adenosine triphosphate, lactic acid
B
Adenosine triphosphate, ionic imbalance
D
Glucose, ionic imbalance
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept:Metabolic basis of muscle fatigue.
Formula:N/A (Conceptual)
Solution:- During extreme exertion, oxygen delivery falls behind demand, forcing the muscle to rely entirely on anaerobic glycolysis.
- This highly inefficient pathway inevitably results in a severe deficit of the energetic currency, Adenosine triphosphate (ATP).
- Simultaneously, the anaerobic breakdown of glucose forces the production and rapid, painful accumulation of the toxic byproduct lactic acid, which drops tissue pH and inhibits enzyme function.
Why other options are incorrect:While glucose depletion contributes to general exhaustion, the direct physiological cause of acute mechanical fatigue is the lack of ATP coupled with lactic acid poisoning.
[NUMS-2023]
Pubic symphysis and intervertebral disc are example of:
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Joint classification by tissue structure.
Formula:N/A (Conceptual)
Solution:- Joints that allow slight, highly restricted movement to absorb shock are typically united by massive pads of tough fibrocartilage.
- Both the pubic symphysis (connecting the pelvic halves) and the intervertebral discs (stacking the spine) fit this description perfectly, classifying them strictly as Cartilaginous joints.
Why other options are incorrect:Synovial joints contain fluid and are freely movable. Fibrous joints (like skull sutures) are completely immobile.
[SZABMU-2023]
A condition in which a joint becomes swollen painful and immoveable is called:
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Pathologies of the articulation system.
Formula:N/A (Conceptual)
Solution:- The universal medical term for the acute or chronic inflammation of a joint—resulting in severe swelling, deep pain, and eventual loss of mobility—is Arthritis.
- This includes various sub-forms like osteoarthritis, rheumatoid arthritis, and gouty arthritis.
Why other options are incorrect:Spondylosis is spinal degeneration. Sciatica is the compression/inflammation of the sciatic nerve. Rickets is a bone-softening disease caused by extreme Vitamin D deficiency in children.
[ETEA-2023]
The joint present between wrist bones is:
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Structural classification of wrist joints.
Formula:N/A (Conceptual)
Solution:- The wrist joint (radiocarpal joint) and the articulations between the individual carpal bones themselves are highly mobile.
- To facilitate this friction-free movement in multiple planes, they are enclosed in a fluid-filled articular capsule, definitively classifying them as Synovial joints.
- Note: While structurally synovial, functionally the main wrist joint acts as a condyloid joint, allowing limited rotation and movement in two planes.
Why other options are incorrect:Fibrous joints are completely immovable (like skull sutures). Cartilaginous joints have very limited mobility (like intervertebral discs). Ball and socket joints strictly require a spherical bone head, which carpals lack.
[UHS-2022]
What is false about cartilage?
A
There are many blood vessels in cartilage
B
It is a form of connective tissue
C
It covers ends of the bone at joints
D
It is much softer than bone
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept:Structural properties of cartilage connective tissue.
Formula:N/A (Conceptual)
Solution:- Cartilage is an avascular structure of the endoskeleton. It is not supplied with blood vessels.
- Because it lacks a direct blood supply, nutrients must diffuse through the extracellular matrix to reach the chondrocytes, which makes it heal very slowly compared to bone.
- Therefore, the statement 'There are many blood vessels in cartilage' is entirely false.
Why other options are incorrect:Options B, C, and D are true biological facts about cartilage. It is a flexible connective tissue that caps the ends of articulating bones to reduce friction.
[NUMS-2022]
Which of the following type of cartilage is most abundant in human body?
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Types of cartilage and their distribution in the human body.
Formula:N/A (Conceptual)
Solution:- Hyaline cartilage is the most abundant type of cartilage in the human body.
- It provides strong, flexible support and is found in the respiratory tract (trachea, bronchi), lines the articular joints, and caps the ends of long bones.
Why other options are incorrect:Fibrous cartilage (found in intervertebral discs) and Elastic cartilage (found in the ear pinna and epiglottis) are much less widely distributed than Hyaline cartilage. 'Flexible' is a property, not a distinct biological class of cartilage.
[BUMHS-2022]
Which of the following is a connective tissue?
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept:Primary tissue types in human anatomy.
Formula:N/A (Conceptual)
Solution:- The human body is composed of four primary tissue types: Epithelial, Connective, Muscular, and Nervous tissue.
- Cartilage, along with bone and blood, is a specialized form of connective tissue that provides structural framework and support.
Why other options are incorrect:Epithelium (lining tissue), Muscle (contractile tissue), and Nerve (conductive tissue) represent the other three distinct primary tissue categories.
[UHS-2022]
Hinge joint is present between which of the following bones?
B
Femur and pectoral girdle
D
Humerus and pectoral girdle
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept:Classification of synovial joints based on movement.
Formula:N/A (Conceptual)
Solution:- A hinge joint allows movement in only one plane (flexion and extension), similar to the hinge of a door.
- The joint between the humerus (upper arm) and the radio-ulna (forearm) forms the elbow joint, which is a classic example of a hinge joint.
Why other options are incorrect:Femur and acetabulum (hip joint) and Humerus and pectoral girdle (shoulder joint) are both examples of ball-and-socket joints, which allow multi-directional movement.
[NUMS-2022]
Which of the following is an example of joint called 'suture'?
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Fibrous joints and their locations.
Formula:N/A (Conceptual)
Solution:- Sutures are incredibly strong, immovable fibrous joints.
- They are specifically found connecting the various flat skull bones together, protecting the brain.
Why other options are incorrect:Intervertebral discs, costal cartilage, and the pubic symphysis are all examples of cartilaginous joints, which allow limited flexibility and movement.
[SZABMU-2022]
A joint in which ends of bones are covered with hyaline cartilage and held together by surrounding tube like capsule of dense fibrous tissue:
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Structural anatomy of synovial joints.
Formula:N/A (Conceptual)
Solution:- A synovial joint is uniquely characterized by the presence of an articular capsule surrounding a fluid-filled joint cavity.
- The ends of the articulating bones are covered in hyaline (articular) cartilage, and the entire structure is enclosed by a dense fibrous capsule that secretes lubricating synovial fluid.
Why other options are incorrect:Fibrous joints lack a capsule and are firmly bound by collagen. Cartilaginous joints are connected entirely by cartilage without a fluid-filled cavity.
[ETEA-2022]
Those joints in which the articulating bones are separated by a fluid-containing joint cavity are called:
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Defining features of synovial joints.
Formula:N/A (Conceptual)
Solution:- The defining hallmark of a synovial joint is the fluid-filled joint cavity separating the articulating bones.
- This synovial fluid acts as a heavily viscous lubricant to dramatically reduce friction during movement.
Why other options are incorrect:Fibrous and cartilaginous joints do not possess any joint cavity. Therefore, they do not contain synovial fluid.
[ETEA-2022]
The joints present in the elbow and knee are the example of which type of joint:
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Movement axes of synovial joints.
Formula:N/A (Conceptual)
Solution:- The elbow and knee allow movement strictly in two directions along a single plane (flexion and extension).
- Because their articulating surfaces are molded to permit motion in only one axis, they are classified as hinge joints.
Why other options are incorrect:Ball and socket joints (like the hip) allow multi-directional, rotational movement. Immovable and slightly movable joints do not allow the wide range of motion seen in the knee and elbow.
[BUMHS-2022]
What is the study of joints:
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Biological terminology.
Formula:N/A (Conceptual)
Solution:- The root word arthro- means 'joint', and the suffix -logy means 'the study of'.
- Therefore, Arthrology is the scientific study of joints and articulations.
Why other options are incorrect:Arthralgia refers strictly to joint pain. Mycology is the study of fungi. Cytology is the study of cells.
[SZABMU-2022]
____ is the inflammation of joints.
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept:Pathologies of the skeletal system.
Formula:N/A (Conceptual)
Solution:- The suffix -itis denotes inflammation. Arthritis broadly means joint inflammation.
- Osteoarthritis is a specific, progressive degenerative disease where articular cartilage softens and disintegrates, leading to severe joint inflammation.
Why other options are incorrect:Osteoporosis is a loss of bone density due to calcium/estrogen depletion. Arteriosclerosis affects blood vessels (hardening of arteries). Osteosclerosis is abnormal hardening of bone tissue.
[ETEA-2022]
Which one of the following is not related to arthritis?
C
The leading cause of disability in patients over the age of 65
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:Characteristics of Arthritis.
Formula:N/A (Conceptual)
Solution:- Arthritis strictly refers to pathological conditions affecting the joints.
- It encompasses joint inflammation (Option A), autoimmune conditions like Rheumatoid arthritis (Option B), and is a primary driver of disability in the elderly (Option C).
- Inflammation of a nerve is called neuritis, which is completely unrelated to the direct definition of arthritis.
Why other options are incorrect:Options A, B, and C are all highly accurate medical descriptors and consequences associated with various forms of arthritis.
[NUMS-2022]
Smooth muscles are long and spindle shaped with ____ nucleus per cell.
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept:Histological structure of smooth muscle cells.
Formula:N/A (Conceptual)
Solution:- Smooth muscle cells are involuntary, non-striated, and characteristically spindle-shaped.
- Unlike skeletal muscle, each individual smooth muscle cell contains only a single, centrally located nucleus (they are uninucleate).
Why other options are incorrect:Skeletal muscle cells form from the fusion of many myoblasts, resulting in long, multinucleated syncytia. Smooth muscles do not undergo this fusion.
[UHS-2022]
Which of the following is not found in skeletal muscle fibers in human?
C
Large amount of myoglobin
D
Large amount of hemoglobin
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:Cellular contents of skeletal muscle.
Formula:N/A (Conceptual)
Solution:- Skeletal muscle fibers are highly metabolically active syncytia. They naturally contain multiple nuclei, dense arrays of mitochondria (for ATP production), and myoglobin, a local oxygen-storing protein.
- Hemoglobin, however, is strictly confined within Red Blood Cells circulating in the vascular system. It is not found inside the actual cytoplasm of skeletal muscle cells.
Why other options are incorrect:Options A, B, and C describe structures specifically adapted to and found within human skeletal muscle tissue.
[ETEA-2022]
The hollow elongated tube formed when muscle fiber penetrates deep into the cell is known as:
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Excitation-contraction coupling anatomy.
Formula:N/A (Conceptual)
Solution:- For a muscle to contract simultaneously throughout its entire thickness, the nerve impulse must be delivered deep inside the cell instantly.
- This is achieved by inward invaginations of the sarcolemma that plunge deep into the interior sarcoplasm. These transverse structures are called T-tubules (Transverse tubules).
Why other options are incorrect:A, M, and Z refer to specific protein bands and lines within the sarcomere structure, not hollow membrane invaginations.
[DUHS-2022]
Each myosin is surrounded by:
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Geometric lattice arrangement of myofilaments in skeletal muscle.
Formula:N/A (Conceptual)
Solution:- When viewed in cross-section within the zone of overlap, the myofibril displays a highly ordered, precise hexagonal lattice.
- In this lattice, each thick myosin filament is symmetrically surrounded by exactly six thin actin filaments, maximizing cross-bridge binding opportunities.
Why other options are incorrect:While a thin actin filament is surrounded by 3 myosin filaments, the reverse (myosin surrounded by actin) is always a 6-to-1 hexagonal ratio.
[UHS-2022]
Which of the following is a muscle component that acts as store for energy?
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Phosphagen energy systems in skeletal muscle.
Formula:$$ADP + Phosphocreatine \rightleftharpoons ATP + Creatine$$
Solution:- Muscles contain very little stored, readily available ATP (only enough for a few seconds of intense contraction).
- To rapidly replenish ATP, resting muscles synthesize and store high-energy phosphate bonds in a backup molecule called Creatine Phosphate (Creatine-PO\(_4\)).
- During sudden bursts of activity, the phosphate is instantly donated back to ADP to regenerate ATP.
Why other options are incorrect:ATP is an immediate currency, not a long-term 'store'. Creatinine is a metabolic waste product filtered by the kidneys, not an energy molecule.
[NUMS-2022]
Which event does not occur during muscle contraction?
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:The Sliding Filament Theory constraints.
Formula:N/A (Conceptual)
Solution:- During contraction, actin filaments are dragged inward, causing the overall sarcomere (Z to Z) to shorten.
- Consequently, the I-band shortens and the central H-zone shrinks and disappears.
- However, the A-band represents the physical length of the thick myosin filaments themselves. Since protein polymers do not magically shrink, the A-band's length remains absolutely constant.
Why other options are incorrect:Options A, C, and D are all classic defining events that
do occur during sliding filament contraction.
[SZABMU-2022]
The muscle contraction involves the breakdown of cross bridges of actin and myosin filaments due to the following process:
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:The cross-bridge cycle and ATP utilization.
Formula:$$ATP + H_2O \rightarrow ADP + P_i + Energy$$
Solution:- In the cross-bridge cycle, the physical binding of a new ATP molecule to the myosin head causes it to detach (break) from actin.
- Immediately following detachment, the myosin head acts as an enzyme, hydrolyzing the ATP into ADP and inorganic phosphate (\(P_i\)).
- This hydrolysis reaction releases the energy required to cock the myosin head back into its high-energy, ready-to-fire position.
Why other options are incorrect:ATP is not fundamentally oxidized or reduced in this mechanical step; it strictly undergoes enzymatic hydrolysis (cleaving a phosphate bond with water).
[SZABMU-2022]
What is the function of myoglobin?
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept:Oxygen handling inside muscle cells.
Formula:N/A (Conceptual)
Solution:- Myoglobin is a monomeric, iron-containing heme protein highly concentrated directly within the sarcoplasm of muscle fibers.
- Unlike hemoglobin, which transports oxygen systemically through the blood, myoglobin's extremely high affinity for oxygen allows it to effectively extract and store oxygen locally within the muscle tissue until it is desperately needed for aerobic respiration.
Why other options are incorrect:Hemoglobin is responsible for long-distance
transport. Myoglobin does not bind or store CO\(_2\) effectively.
[PMC-2020]
Which one of the following muscles are considered as 'voluntary muscles'?
View Answer & Propolis Autopsy
Correct Key: Option B
Diagnostic Explanation
Concept:Muscle tissue classification by control mechanism.
Formula:N/A (Conceptual)
Solution:- Voluntary muscles are those that can be consciously controlled by the somatic nervous system.
- Skeletal muscles are attached to the skeleton and are responsible for all conscious movements (walking, lifting, etc.), making them strictly voluntary.
Why other options are incorrect:Cardiac muscle (heart) and Smooth muscle (digestive tract, blood vessels) are controlled by the autonomic nervous system and are entirely involuntary.
[PMC-2020]
Which one of the following are 'myogenic' type of muscles?
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Myogenic vs. Neurogenic muscle contraction.
Formula:N/A (Conceptual)
Solution:- Myogenic means the contraction signal originates directly from within the muscle tissue itself, rather than requiring an external nerve impulse.
- Cardiac muscles contain specialized pacemaker cells (the SA node) that spontaneously generate their own action potentials, allowing the heart to beat autonomously. Thus, they are highly myogenic.
Why other options are incorrect:Skeletal muscles are neurogenic; they will not contract without a direct signal from a motor neuron.
[PMC-2020]
What do we call the cell surface membrane of a muscle fiber?
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept:Muscle cell nomenclature.
Formula:N/A (Conceptual)
Solution:- While it is technically a specialized type of plasma membrane, biological convention uses strict specific terminology for muscle cells.
- The distinct outer boundary and excitable cell membrane of a skeletal muscle fiber is exclusively termed the sarcolemma.
Why other options are incorrect:Sarcoplasm is the cytoplasm inside the cell. Myofibrils are the internal contractile threads. Plasma membrane is biologically accurate but generically broad; 'sarcolemma' is the specific, correct answer.
[MDCAT-2019]
Thin filaments of muscles contain ____ chains of actin molecules.
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:Molecular composition of the thin myofilament.
Formula:N/A (Conceptual)
Solution:- The core of the thin filament is composed of the protein F-actin (filamentous actin).
- F-actin is formed by the polymerization of globular G-actin monomers into exactly two long strands that twist around each other in a double-helical configuration.
Why other options are incorrect:While thin filaments also contain tropomyosin and the 3-subunit troponin complex, the foundational actin core strictly consists of only two intertwined chains.
[MDCAT-2019]
The thick filaments in a myofibril of muscles are made up of ____.
View Answer & Propolis Autopsy
Correct Key: Option D
Diagnostic Explanation
Concept:Protein composition of muscle filaments.
Formula:N/A (Conceptual)
Solution:- Myofibrils contain two main types of filaments: thick and thin.
- The thick filaments are composed entirely of hundreds of intertwined molecules of the motor protein myosin, which features heavy tail regions and specialized globular heads with ATPase activity.
Why other options are incorrect:Actin forms the thin filaments. Haemoglobin and myoglobin are entirely separate globular oxygen-binding proteins, completely unrelated to the physical filament structure.
[MDCAT-2019]
The function of calcium ions in muscle contraction is to:
A
Bind to troponin molecule and cause them to move
C
Aid in the transmission of nerve impulse
D
Bind to tropomyosin molecule and cause them to form cross bridges
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept:Role of Calcium in cross-bridge cycling.
Formula:N/A (Conceptual)
Solution:- In a resting muscle, tropomyosin actively blocks the myosin-binding sites on actin.
- When an action potential arrives, Ca\(^{2+}\) is released from the sarcoplasmic reticulum. The Ca\(^{2+}\) physically binds to specific subunits on the troponin complex.
- This binding induces a massive conformational change in troponin, forcing it to drag tropomyosin out of the way, thereby exposing the active sites for cross-bridge formation.
Why other options are incorrect:Calcium binds strictly to troponin (TnC), not directly to tropomyosin. While muscles have anisotropic properties under polarized light, Ca\(^{2+}\) is a chemical trigger, not a light polarizer.
[MDCAT-2017]
Over lapping of thick filament occurs in:
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept:Banding patterns in the sliding filament model.
Formula:N/A (Conceptual)
Solution:- The A-Band represents the entire length of the thick myosin filaments.
- In the peripheral edges of the A-Band, these thick filaments physically overlap with the interdigitating thin actin filaments, creating a very dense, dark appearance under a microscope.
Why other options are incorrect:The I-Band contains strictly thin filaments. The H-zone (center of A-band) contains only thick filaments (no overlap). The Z-line anchors thin filaments.
[ETEA-2017]
Sarcolemma is the membrane around?
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Cellular wrappers in musculoskeletal anatomy.
Formula:N/A (Conceptual)
Solution:- The prefix sarco- translates to 'flesh' or 'muscle'.
- The sarcolemma is explicitly the specialized lipid bilayer plasma membrane that directly surrounds an individual muscle fiber (muscle cell).
Why other options are incorrect:Bones are covered by the periosteum. Joints are enclosed by synovial capsules. 'Heat' is a form of energy, not a biological structure.
#60 of 63
MDCAT-2016, 2017
[MDCAT-2016, 2017]
Each muscle fiber is surrounded by a modified cell membrane called:
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept:Anatomy of a muscle cell.
Formula:N/A (Conceptual)
Solution:- A muscle fiber is a single muscle cell.
- Its highly specialized outer plasma membrane, which is uniquely capable of conducting action potentials deep into the cell via T-tubules, is called the sarcolemma.
Why other options are incorrect:Myofilaments (actin/myosin) and sarcomeres are internal contractile structures. They are surrounded by the sarcoplasm and eventually bounded by the sarcolemma.
[MDCAT-2015]
A sarcomere is the region of a myofibril between two successive:
View Answer & Propolis Autopsy
Correct Key: Option C
Diagnostic Explanation
Concept:Boundaries of the sarcomere.
Formula:N/A (Conceptual)
Solution:- The basic functional unit of muscle contraction is the sarcomere.
- By standard histological definition, a single sarcomere spans the exact distance between two successive Z-lines (or Z-discs), which anchor the thin actin filaments.
Why other options are incorrect:The M-line is the center of the sarcomere. The I-band spans across the Z-line into two adjacent sarcomeres. T-tubules are membrane invaginations, not filament boundaries.
[MDCAT-2015]
According to sliding filament theory, when muscle fibers are stimulated by nervous system, which of the following changes occurs?
B
Z-lines move further apart
C
H-zone becomes more visible
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept:Changes in sarcomere banding during contraction.
Formula:N/A (Conceptual)
Solution:- According to the sliding filament theory, myofilaments themselves do not change length; rather, the thin filaments slide deeply into the A-band.
- As the Z-lines are pulled closer together, the region containing only thin filaments (the I-band) noticeably shortens.
Why other options are incorrect:Z-lines move closer together, not further apart. The H-zone (center gap) narrows and disappears, rather than becoming more visible. The A-band remains completely unchanged in length because the thick filaments do not shrink.
[MDCAT-2014]
The repeated protein pattern of myofibrils is called:
View Answer & Propolis Autopsy
Correct Key: Option A
Diagnostic Explanation
Concept:Ultrastructure of striated muscle fibers.
Formula:N/A (Conceptual)
Solution:- A myofibril is composed of highly organized repeating units of actin and myosin filaments.
- This repeating functional pattern, stretching from one Z-line to the next, is strictly defined as a sarcomere. It is the fundamental contractile unit of striated muscle.
Why other options are incorrect:The sarcolemma is the cell membrane. Cross bridges are the physical attachments between myosin heads and actin. 'Zyomere' is an incorrect/typographical distractor for Z-line.
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