Subtopic: Nutrient Artery
Keywords & Definitions:
Nutrient artery: The main artery that enters the diaphysis of long bones through the nutrient foramen supplying the bone marrow and inner two-thirds of the cortex.
Metaphysis: The neck portion of a long bone between the epiphysis and diaphysis, rich in blood supply for bone growth.
Epiphysis: The rounded end of a long bone, initially separated from the diaphysis by the growth plate.
Diaphysis: The shaft or central part of a long bone.
Bone vasculature: The network of blood vessels supplying bones, critical for nutrition and repair.
Foramen: An opening or hole in bone for passage of vessels and nerves.
Clinical relevance: Knowledge of nutrient artery direction is vital during orthopedic surgeries to avoid ischemia.
Growth plate: Also called the epiphyseal plate, site of longitudinal bone growth.
Blood supply: Nutrient arteries supply inner compact bone and marrow, while periosteal arteries supply outer bone.
Long bones: Bones longer than they are wide, such as femur, tibia, humerus.
Lead Question - 2012:
Nutrient artery runs?
a) Towards metaphysis
b) Away from metaphysis
c) Away from epiphysis
d) None
Explanation & Answer:
The correct answer is b) Away from metaphysis. Nutrient arteries enter the diaphysis and typically run away from the metaphysis towards the epiphysis. This ensures the metaphysis, which has a rich blood supply from other sources, is not primarily dependent on the nutrient artery. This is crucial in fracture healing and orthopedic interventions.
Q2. Which part of the bone does the nutrient artery primarily supply?
a) Outer periosteum
b) Inner two-thirds of cortex and marrow
c) Epiphyseal cartilage
d) Articular cartilage
Explanation & Answer:
The nutrient artery mainly supplies the inner two-thirds of the cortex and the bone marrow (option b). The outer one-third of the cortex is supplied by periosteal arteries.
Q3. The nutrient foramen is usually located on which surface of long bones?
a) Posterior
b) Anterior
c) Lateral
d) Variable but often on the shaft's anterior surface
Explanation & Answer:
The nutrient foramen is variable but most commonly located on the anterior surface of the shaft (option d). Its position is important during surgical approaches to avoid damaging vessels.
Q4. Which artery supplements the blood supply to the epiphysis?
a) Nutrient artery
b) Metaphyseal artery
c) Periosteal artery
d) Epiphyseal artery
Explanation & Answer:
The epiphyseal artery (option d) supplies the epiphysis, which is separate from the nutrient artery that mainly supplies the diaphysis and medullary cavity.
Q5 (Clinical). Damage to the nutrient artery during fracture fixation can result in?
a) Delayed union or nonunion
b) Increased bone growth
c) Immediate bone healing
d) No clinical significance
Explanation & Answer:
Injury to the nutrient artery can cause delayed union or nonunion (option a) due to compromised blood supply essential for bone healing.
Q6. Which embryological layer forms the periosteum that carries periosteal arteries?
a) Endoderm
b) Mesoderm
c) Ectoderm
d) Neural crest
Explanation & Answer:
The periosteum, containing periosteal arteries, is derived from the mesoderm (option b), which also forms most skeletal components.
Q7. Which of the following is NOT a source of blood supply to long bones?
a) Nutrient artery
b) Periosteal arteries
c) Metaphyseal and epiphyseal arteries
d) Pulmonary arteries
Explanation & Answer:
Pulmonary arteries (option d) do not supply bones; they are part of the lung circulation. Bones receive blood from nutrient, periosteal, metaphyseal, and epiphyseal arteries.
Q8. The nutrient artery enters the bone via?
a) Epiphyseal plate
b) Nutrient foramen
c) Metaphyseal artery
d) Periosteum
Explanation & Answer:
The nutrient artery enters the bone through the nutrient foramen (option b), a small opening in the diaphyseal cortex.
Q9 (Clinical). Nutrient artery injury is most critical in which type of bone fracture?
a) Greenstick fracture
b) Comminuted fracture
c) Spiral fracture
d) Transverse fracture of diaphysis
Explanation & Answer:
Transverse diaphyseal fractures (option d) can disrupt the nutrient artery, risking compromised blood supply and delayed healing.
Q10. The nutrient artery usually arises from which blood vessel?
a) Periosteal arteries
b) Major systemic arteries near the bone
c) Venous system
d) Lymphatic vessels
Explanation & Answer:
The nutrient artery typically arises from major systemic arteries near the bone (option b), such as the femoral artery for the femur
Subtopic: Corpora Arenacea
Keywords & Definitions:
Corpora arenacea: Also called brain sand, these are calcified concretions found mainly in the pineal gland.
Pineal gland: A small endocrine gland in the brain involved in melatonin secretion and regulation of circadian rhythms.
Prostate: Male accessory sex gland producing seminal fluid, sometimes contains corpora amylacea, not arenacea.
Seminal vesicle: Gland producing seminal fluid, usually does not contain corpora arenacea.
Histology: The microscopic study of tissues and cells.
Calcification: Deposition of calcium salts in tissues, often pathological or age-related.
Endocrine gland: A gland that secretes hormones directly into the bloodstream.
Brain sand: Common name for corpora arenacea.
Clinical relevance: Calcifications can be seen on imaging and are sometimes diagnostic clues.
Microscopic anatomy: Study of tissue structure under the microscope.
Lead Question - 2012:
Corpora arenacea is seen in?
a) Prostate
b) Pineal
c) Seminal vesicle
d) Breast
Explanation & Answer:
The correct answer is b) Pineal. Corpora arenacea, or brain sand, are calcified concretions most commonly found in the pineal gland. These increase with age and can be detected on radiological imaging. They are unrelated to the prostate, seminal vesicles, or breast tissue.
Q2. Corpora arenacea are primarily composed of which mineral?
a) Calcium phosphate
b) Uric acid
c) Magnesium
d) Iron
Explanation & Answer:
Corpora arenacea are mainly composed of calcium phosphate (option a), which forms their characteristic calcified structure within the pineal gland.
Q3. At what age do corpora arenacea typically start to appear?
a) Neonatal period
b) Childhood
c) Adolescence and adulthood
d) Only in elderly
Explanation & Answer:
Corpora arenacea generally begin to appear in adolescence and increase with age during adulthood (option c), often becoming prominent in the elderly.
Q4. Which imaging modality best detects corpora arenacea?
a) Ultrasound
b) X-ray
c) MRI
d) CT scan
Explanation & Answer:
Computed tomography (CT) scans (option d) are most effective in detecting calcifications like corpora arenacea due to their high sensitivity to calcium deposits.
Q5 (Clinical). Calcifications of corpora arenacea are clinically significant because:
a) They cause hormonal imbalances
b) They may indicate pineal gland tumors
c) They can cause seizures
d) Usually incidental without clinical symptoms
Explanation & Answer:
Corpora arenacea calcifications are usually incidental findings (option d) without clinical symptoms, though their presence can sometimes help localize the pineal gland on imaging.
Q6. Which hormone is secreted by the pineal gland where corpora arenacea are found?
a) Melatonin
b) Cortisol
c) Insulin
d) Growth hormone
Explanation & Answer:
The pineal gland secretes melatonin (option a), a hormone involved in regulating circadian rhythms and sleep-wake cycles.
Q7. Corpora arenacea are sometimes called:
a) Prostatic concretions
b) Brain sand
c) Amyloid plaques
d) Calcium oxalate crystals
Explanation & Answer:
Corpora arenacea are commonly referred to as brain sand (option b) due to their sand-like appearance within the pineal gland.
Q8 (Clinical). Pineal gland calcifications can be mistaken for which pathology in radiological imaging?
a) Brain tumor
b) Hemorrhage
c) Aneurysm
d) Infections
Explanation & Answer:
Pineal calcifications (corpora arenacea) may be mistaken for tumors (option a) or other lesions; hence proper interpretation is crucial to avoid misdiagnosis.
Q9. Corpora arenacea form due to:
a) Degeneration of pinealocytes
b) Infection
c) Trauma
d) Immune reaction
Explanation & Answer:
Corpora arenacea result mainly from progressive calcification and mineral deposition on degenerating pinealocytes and glial tissue (option a) in the pineal gland.
Q10. Which is the primary function of the pineal gland?
a) Regulation of blood pressure
b) Secretion of digestive enzymes
c) Regulation of sleep-wake cycle
d) Production of sex hormones
Explanation & Answer:
The pineal gland primarily regulates the sleep-wake cycle (option c) through melatonin secretion, influenced by light-dark cycles.
Subtopic: Corpora Amylacea
Keywords & Definitions:
Corpora amylacea: Round, concentric, laminated bodies found in various organs, often associated with aging or pathology.
Thymus: Primary lymphoid organ involved in T-cell maturation.
Lymph node: Secondary lymphoid organ filtering lymph and housing immune cells.
Spleen: Organ involved in blood filtration, immune response, and red blood cell recycling.
Prostate: Male accessory sex gland producing seminal fluid.
Histology: The study of tissues at microscopic level.
Age-related changes: Structural alterations in tissues occurring with aging.
Laminated bodies: Structures with layered appearance.
Pathology: Study of diseases and abnormal tissue changes.
Microanatomy: Fine structure of tissues and cells.
Lead Question - 2012:
Corpora amylaciae is seen in -
a) Thymus
b) Lymph node
c) Spleen
d) Prostate
Explanation & Answer:
The correct answer is d) Prostate. Corpora amylacea are laminated, concentric bodies commonly found in the prostate gland, especially in older men. They represent accumulations of secretory material and cellular debris. Corpora amylacea can also be seen rarely in other tissues but are most characteristic of the prostate.
Q2. Corpora amylacea in the prostate are primarily composed of which substance?
a) Calcium phosphate
b) Glycoproteins and carbohydrates
c) Cholesterol
d) Lipids
Explanation & Answer:
Corpora amylacea consist mainly of glycoproteins and carbohydrate polymers (option b), giving them a PAS-positive staining pattern. They may also accumulate calcium salts secondarily.
Q3. Which staining technique is commonly used to identify corpora amylacea?
a) Hematoxylin and eosin
b) Periodic acid-Schiff (PAS)
c) Silver stain
d) Oil Red O
Explanation & Answer:
Periodic acid-Schiff (PAS) stain (option b) is commonly used to highlight corpora amylacea due to their carbohydrate-rich composition.
Q4. Corpora amylacea are more frequently observed in which age group?
a) Neonates
b) Children
c) Middle-aged adults
d) Elderly adults
Explanation & Answer:
Corpora amylacea increase with age and are predominantly seen in elderly adults (option d), reflecting accumulation of secretory material over time.
Q5 (Clinical). Presence of corpora amylacea in the prostate is associated with which clinical condition?
a) Prostatitis
b) Benign prostatic hyperplasia (BPH)
c) Prostate cancer
d) Prostate abscess
Explanation & Answer:
Corpora amylacea are commonly seen in benign prostatic hyperplasia (BPH) (option b), where enlarged glands produce excess secretions leading to formation of these structures.
Q6. Besides the prostate, corpora amylacea may occasionally be found in:
a) Lungs
b) Brain
c) Liver
d) Kidneys
Explanation & Answer:
Corpora amylacea are occasionally seen in the brain (option b), especially in aging or neurodegenerative diseases, but they are most prominent and clinically relevant in the prostate.
Q7. What is the typical shape of corpora amylacea under the microscope?
a) Irregular
b) Concentric laminated spheres
c) Rod-shaped
d) Star-shaped
Explanation & Answer:
Corpora amylacea have a characteristic concentric laminated spherical shape (option b), visible under light microscopy.
Q8 (Clinical). Which diagnostic technique can detect corpora amylacea in prostate tissue biopsies?
a) Ultrasound
b) MRI
c) Histopathological examination
d) PSA blood test
Explanation & Answer:
Histopathological examination (option c) of prostate biopsies with staining is the definitive method to detect corpora amylacea.
Q9. What is the clinical significance of corpora amylacea in prostate biopsies?
a) Indicator of malignancy
b) Indicator of inflammation
c) Usually incidental, not malignant
d) Diagnostic for prostate infection
Explanation & Answer:
Corpora amylacea are usually incidental findings (option c) and do not indicate malignancy or infection, though they are often found in benign conditions like BPH.
Q10. Corpora amylacea are believed to form by:
a) Degeneration of epithelial cells
b) Calcification of blood vessels
c) Accumulation of secretory products and debris
d) Infectious granuloma formation
Explanation & Answer:
Corpora amylacea form due to accumulation of secretory products and cellular debris (option c), which then organize into laminated bodies, often increasing with age or chronic glandular activity.
Subtopic: Classification of Glands by Secretion
Keywords & Definitions:
Eccrine gland: Sweat gland that secretes watery fluid directly onto skin surface by exocytosis (merocrine secretion).
Apocrine gland: Gland releasing secretion by pinching off part of the cytoplasm along with secretory product.
Holocrine gland: Gland where entire cell disintegrates to release secretion.
Paracrine secretion: Cell secretes signaling molecules that act on neighboring cells.
Sebaceous gland: Oil-producing gland usually associated with hair follicles.
Mode of secretion: The method by which glands release their secretory products.
Merocrine secretion: Secretion via exocytosis without loss of cellular material.
Secretory product: Substance produced and released by glands.
Skin appendages: Structures derived from skin, such as hair, nails, and glands.
Exocytosis: Process of vesicles fusing with the plasma membrane to release contents outside the cell.
Lead Question - 2012:
Glands are classified depending upon their mode of secretion. Sebaceous gland is an example of which of the following type of gland?
a) Eccrine
b) Apocrine
c) Holocrine
d) Paracrine
Explanation & Answer:
The correct answer is c) Holocrine. Sebaceous glands secrete sebum by holocrine secretion, meaning the entire cell disintegrates to release its oily content. This differs from eccrine glands, which use merocrine secretion, and apocrine glands, which release part of their cytoplasm. Paracrine is a form of cell signaling, not secretion.
Q2. Which gland secretes a watery fluid primarily for thermoregulation?
a) Sebaceous gland
b) Apocrine sweat gland
c) Eccrine sweat gland
d) Ceruminous gland
Explanation & Answer:
Eccrine sweat glands (option c) secrete a watery fluid primarily involved in thermoregulation by evaporation. Sebaceous glands secrete oily sebum; apocrine glands secrete thicker sweat; ceruminous glands produce earwax.
Q3. Apocrine glands are mainly found in which of the following areas?
a) Palms and soles
b) Scalp
c) Axilla and perineum
d) Face
Explanation & Answer:
Apocrine glands (option c) are localized primarily to the axilla and perineal regions, secreting a thicker sweat that becomes odorous after bacterial action.
Q4. Which secretion mode involves release of secretory vesicles without loss of cytoplasm?
a) Holocrine
b) Apocrine
c) Merocrine
d) Paracrine
Explanation & Answer:
Merocrine secretion (option c) involves exocytosis of secretory products without any loss of cytoplasm, typical of eccrine sweat glands.
Q5 (Clinical). Acne vulgaris primarily involves inflammation of which gland?
a) Apocrine glands
b) Eccrine glands
c) Sebaceous glands
d) Ceruminous glands
Explanation & Answer:
Acne vulgaris (option c) results from inflammation of sebaceous glands with blockage of hair follicles and bacterial colonization leading to pimples and cysts.
Q6. Ceruminous glands are specialized modified versions of which gland?
a) Sebaceous
b) Eccrine sweat glands
c) Apocrine sweat glands
d) Paracrine glands
Explanation & Answer:
Ceruminous glands (option c) are modified apocrine glands located in the external auditory canal, producing earwax (cerumen).
Q7. Which gland type is NOT associated with hair follicles?
a) Sebaceous gland
b) Apocrine sweat gland
c) Eccrine sweat gland
d) None of the above
Explanation & Answer:
Eccrine sweat glands (option c) are independent of hair follicles, unlike sebaceous and apocrine glands which are usually associated with hair follicles.
Q8. Which gland secretion contains lipids, cellular debris, and antibacterial substances?
a) Eccrine sweat
b) Sebaceous gland secretion
c) Apocrine sweat
d) Ceruminous gland secretion
Explanation & Answer:
Sebaceous gland secretion (option b) or sebum contains lipids, cellular debris, and has antibacterial properties to protect skin.
Q9 (Clinical). Which gland's dysfunction is implicated in hidradenitis suppurativa?
a) Eccrine sweat glands
b) Apocrine sweat glands
c) Sebaceous glands
d) Ceruminous glands
Explanation & Answer:
Hidradenitis suppurativa (option b) involves chronic inflammation and blockage of apocrine sweat glands, especially in axillary and groin areas.
Q10. Paracrine signaling involves:
a) Secretion into bloodstream
b) Cell signaling to neighboring cells
c) Self-stimulation of the secreting cell
d) Secretion by exocytosis only
Explanation & Answer:
Paracrine signaling (option b) refers to secretion of signaling molecules that affect nearby cells, unlike endocrine which involves bloodstream transport.
Subtopic: Types of Epiphyses
Keywords & Definitions:
Traction epiphysis: An epiphysis subjected to tensile forces by muscles or tendons rather than weight-bearing.
Pressure epiphysis: Epiphysis subjected to compressive forces and weight-bearing.
Epiphysis: The end part of a long bone, initially growing separately from the shaft.
Apophysis: A secondary ossification center that serves as a site of tendon or ligament attachment.
Ossification: The process of bone formation.
Growth plate (physis): Cartilaginous zone allowing longitudinal bone growth.
Trochanter: A large, blunt projection on a bone for muscle attachment.
Coracoid process: A hook-like bony projection from the scapula for muscle attachment.
Femur: The thigh bone, longest bone in the body.
Tibial condyles: Rounded prominences at the top of tibia involved in knee joint articulation.
Lead Question - 2012:
Which of the following is a traction epiphysis?
a) Tibial condyles
b) Trochanter of femur
c) Coracoid process of scapula
d) Head of femur
Explanation & Answer:
The correct answer is b) Trochanter of femur. Traction epiphyses are sites where tendons or muscles pull on bones, causing tensile stress; the trochanter of the femur is a classic example. Other options like tibial condyles and head of femur are pressure epiphyses subjected to compressive forces, and the coracoid process is an apophysis but not classically classified as traction epiphysis.
Q2. Pressure epiphysis primarily undergoes growth by?
a) Longitudinal growth at physis
b) Appositional growth only
c) Ossification of periosteum
d) Remodeling by osteoclasts
Explanation & Answer:
Pressure epiphyses grow primarily by longitudinal growth at the physis (growth plate), responding to compressive forces from weight-bearing.
Q3. Which of the following is NOT a traction epiphysis?
a) Tibial tuberosity
b) Greater trochanter
c) Calcaneal tuberosity
d) Femoral head
Explanation & Answer:
The femoral head (option d) is a pressure epiphysis, not a traction epiphysis, as it bears weight and articulates with the acetabulum.
Q4. The ossification center of a traction epiphysis is usually classified as?
a) Primary ossification center
b) Secondary ossification center
c) Apophysis
d) Sesamoid bone
Explanation & Answer:
Traction epiphyses typically correspond to apophyses (option c), which are secondary ossification centers at sites of tendon attachment.
Q5 (Clinical). Osgood-Schlatter disease affects which traction epiphysis?
a) Tibial tuberosity
b) Calcaneus
c) Trochanter
d) Coracoid process
Explanation & Answer:
Osgood-Schlatter disease (option a) is inflammation of the tibial tuberosity, a traction epiphysis where the patellar tendon attaches, common in adolescents during growth spurts.
Q6. Which bone feature is an example of a sesamoid bone rather than a traction epiphysis?
a) Patella
b) Greater trochanter
c) Coracoid process
d) Tibial tuberosity
Explanation & Answer:
The patella (option a) is a sesamoid bone embedded in the tendon of quadriceps muscle, different from traction epiphyses which are ossification centers at tendon insertions.
Q7. Which of the following statements about traction epiphyses is true?
a) They are sites of weight-bearing
b) They develop ossification centers due to tensile forces
c) They fuse early during childhood
d) They are involved in joint articulation
Explanation & Answer:
Traction epiphyses (option b) develop ossification centers where tendons exert pulling forces; they are not primarily weight-bearing or articular surfaces.
Q8. Which epiphysis typically fuses last during skeletal maturity?
a) Pressure epiphysis
b) Traction epiphysis
c) Apophysis
d) Primary ossification center
Explanation & Answer:
Traction epiphyses (option b) often fuse later than pressure epiphyses, as they correspond to sites under tensile forces and tendon attachments.
Q9 (Clinical). Avulsion fractures of traction epiphyses occur due to?
a) Excessive tensile forces
b) Compressive forces
c) Direct trauma only
d) Osteoporosis
Explanation & Answer:
Avulsion fractures (option a) of traction epiphyses happen when excessive tensile forces from muscle contraction pull the ossification center away from the bone.
Q10. Which of the following is a characteristic feature of traction epiphyses?
a) Subjected mainly to compressive stress
b) Serve as tendon attachment sites
c) Participate in joint surface formation
d) Do not undergo endochondral ossification
Explanation & Answer:
Traction epiphyses (option b) serve as attachment sites for tendons and muscles, experiencing tensile rather than compressive forces, and undergo endochondral ossification like other epiphyses.
Subtopic: Formation and Closure of Fossa Ovalis
Keywords & Definitions:
Fossa ovalis: A depression in the right atrium, remnant of the fetal foramen ovale.
Foramen ovale: A fetal opening in the interatrial septum allowing blood to bypass lungs.
Septum primum: The first interatrial septum, grows downward towards endocardial cushions.
Septum secundum: The second crescent-shaped septum overlapping foramen ovale.
Endocardial cushion: Tissue in the atrioventricular canal that contributes to septa and valves.
Interatrial septum: The wall separating left and right atria in the heart.
Fusion: Joining of embryonic structures to form a definitive anatomical part.
Patent foramen ovale: Failure of the foramen ovale to close after birth.
Left atrial pressure: Pressure that pushes septa to fuse after birth.
Embryonic heart development: The process by which cardiac chambers and septa form.
Lead Question - 2012:
Fossa ovalis closes because of the fusion of?
a) Septum primum + Endocardial cushion
b) Septum secundum + Endocardial cushion
c) Septum primum + Septum secundum
d) None
Explanation & Answer:
The correct answer is c) Septum primum + Septum secundum. After birth, increased left atrial pressure pushes the septum primum against the septum secundum, leading to their fusion which closes the foramen ovale functionally and forms the fossa ovalis. The endocardial cushions contribute to atrioventricular septation but not directly to this fusion. Failure to close leads to a patent foramen ovale.
Q2. The foramen ovale allows blood flow between which two chambers in fetal life?
a) Right atrium to left atrium
b) Left atrium to right atrium
c) Right ventricle to left ventricle
d) Left ventricle to right ventricle
Explanation & Answer:
The foramen ovale (option a) permits oxygenated blood to flow from the right atrium directly to the left atrium, bypassing the nonfunctional fetal lungs.
Q3. Which embryonic structure forms the muscular part of the interventricular septum?
a) Endocardial cushions
b) Bulbus cordis
c) Primitive ventricle
d) Truncus arteriosus
Explanation & Answer:
The muscular interventricular septum (option c) develops from the primitive ventricle, separating left and right ventricles during heart development.
Q4. Patent foramen ovale can lead to which clinical condition?
a) Cyanotic congenital heart disease
b) Paradoxical embolism
c) Aortic stenosis
d) Mitral valve prolapse
Explanation & Answer:
Patent foramen ovale (option b) can allow venous thrombi to bypass the lungs and enter systemic circulation, causing paradoxical embolism, stroke, or transient ischemic attacks.
Q5 (Clinical). A newborn with persistent right-to-left shunt through foramen ovale may present with?
a) Cyanosis
b) Tachycardia
c) Hypertension
d) Bradycardia
Explanation & Answer:
Persistent right-to-left shunting (option a) causes deoxygenated blood to bypass lungs, resulting in cyanosis and hypoxemia after birth.
Q6. The endocardial cushions contribute to the formation of?
a) Interventricular septum only
b) Atrioventricular septum and valves
c) Aortic arch
d) Pulmonary veins
Explanation & Answer:
Endocardial cushions (option b) are vital for forming atrioventricular septum and valves, separating atria and ventricles and forming mitral and tricuspid valves.
Q7. Which septum forms the initial partition in the primitive atrium?
a) Septum secundum
b) Septum primum
c) Endocardial cushion
d) Ventricular septum
Explanation & Answer:
The septum primum (option b) is the first structure to grow downward from the atrial roof, starting the separation of the primitive atrium into right and left atria.
Q8. The septum secundum forms a partial wall on which side of the heart?
a) Left atrium
b) Right atrium
c) Left ventricle
d) Right ventricle
Explanation & Answer:
The septum secundum (option b) grows on the right atrial side, overlapping the foramen ovale, allowing a flap valve mechanism to regulate fetal blood flow.
Q9 (Clinical). Atrial septal defect is most commonly due to failure of?
a) Fusion of septum primum and secundum
b) Closure of ductus arteriosus
c) Formation of endocardial cushions
d) Septation of ventricles
Explanation & Answer:
Atrial septal defect (option a) often results from incomplete fusion of septum primum and septum secundum, causing persistent interatrial communication and left-to-right shunt.
Q10. After birth, the functional closure of the foramen ovale is primarily due to?
a) Increase in right atrial pressure
b) Increase in left atrial pressure
c) Decrease in systemic vascular resistance
d) Constriction of ductus arteriosus
Explanation & Answer:
The increased left atrial pressure after birth (option b) pushes the septum primum against septum secundum, functionally closing the foramen ovale and preventing blood flow between atria.
Subtopic: Origin of Glial Cells
Keywords & Definitions:
Mesoderm: The middle germ layer giving rise to muscles, blood vessels, connective tissue, and microglia.
Ectoderm: The outer germ layer from which neurons and most glial cells (astrocytes, oligodendrocytes, ependymal cells) develop.
Microglial cells: CNS immune cells derived from mesodermal origin (yolk sac macrophages).
Astrocytes: Star-shaped glial cells providing structural and metabolic support, derived from neuroectoderm.
Oligodendrocytes: Myelin-forming cells in CNS, originating from neuroectoderm.
Ependymal cells: Line ventricles and central canal of spinal cord; derived from neuroectoderm.
Neuroglia: Supporting cells of nervous system including astrocytes, oligodendrocytes, microglia, and ependymal cells.
Yolk sac macrophages: Early embryonic mesodermal cells that migrate to CNS as microglia.
CNS immune surveillance: Microglia function as resident macrophages in brain and spinal cord.
Neuroectoderm: Specialized ectoderm that forms the nervous system structures.
Lead Question - 2012:
Mesodermal in origin?
a) Astrocytes
b) Oligodendrocytes
c) Ependymal cells
d) Microglial cells
Explanation & Answer:
The correct answer is d) Microglial cells. Microglia are the only glial cells derived from the mesoderm, specifically from yolk sac macrophages. All other glial cells such as astrocytes, oligodendrocytes, and ependymal cells originate from the neuroectoderm (ectodermal layer). Microglia act as the resident immune cells in the central nervous system, providing defense and cleanup.
Q2. Which glial cell is responsible for myelin formation in the CNS?
a) Microglia
b) Oligodendrocytes
c) Astrocytes
d) Ependymal cells
Explanation & Answer:
Oligodendrocytes (option b) produce myelin sheaths around axons in the CNS, increasing conduction velocity. Unlike Schwann cells in the peripheral nervous system, oligodendrocytes can myelinate multiple axons simultaneously.
Q3. Which cells line the ventricles of the brain?
a) Astrocytes
b) Oligodendrocytes
c) Ependymal cells
d) Microglia
Explanation & Answer:
Ependymal cells (option c) line the ventricular system and central canal of the spinal cord. They facilitate cerebrospinal fluid circulation and act as a barrier between CSF and nervous tissue.
Q4. Which glial cell provides structural and metabolic support to neurons?
a) Astrocytes
b) Microglia
c) Oligodendrocytes
d) Ependymal cells
Explanation & Answer:
Astrocytes (option a) support neurons structurally and metabolically by maintaining the blood-brain barrier, regulating ion balance, and supplying nutrients.
Q5 (Clinical). Microglial activation is primarily seen in which condition?
a) Multiple sclerosis
b) Alzheimer's disease
c) Meningitis
d) Parkinson’s disease
Explanation & Answer:
Microglial activation (option b) is a hallmark of Alzheimer’s disease, where these immune cells contribute to neuroinflammation and clearance of amyloid plaques.
Q6. Which cell type forms the blood-brain barrier?
a) Microglia
b) Astrocytes
c) Ependymal cells
d) Oligodendrocytes
Explanation & Answer:
Astrocyte end-feet (option b) contribute to the blood-brain barrier by surrounding endothelial cells and regulating molecule passage from blood to brain.
Q7. The primary immune defense cells in the CNS are:
a) Oligodendrocytes
b) Microglia
c) Astrocytes
d) Ependymal cells
Explanation & Answer:
Microglia (option b) serve as the resident macrophages of the CNS, performing immune surveillance, phagocytosis, and release of cytokines.
Q8. Which glial cells originate from the neuroectoderm?
a) Microglia only
b) Astrocytes, oligodendrocytes, ependymal cells
c) Microglia and astrocytes
d) All glial cells
Explanation & Answer:
Astrocytes, oligodendrocytes, and ependymal cells (option b) develop from the neuroectoderm, whereas microglia are mesoderm-derived.
Q9 (Clinical). Which glial cell dysfunction is implicated in demyelinating diseases?
a) Astrocytes
b) Oligodendrocytes
c) Microglia
d) Ependymal cells
Explanation & Answer:
Oligodendrocyte damage (option b) leads to demyelination in diseases like multiple sclerosis, impairing nerve conduction.
Q10. Which cells contribute to cerebrospinal fluid (CSF) production?
a) Microglia
b) Ependymal cells
c) Astrocytes
d) Oligodendrocytes
Explanation & Answer:
Ependymal cells (option b), especially specialized choroid plexus epithelium, secrete cerebrospinal fluid and line the ventricles.
Subtopic: Parathyroid Gland Development
Keywords & Definitions:
Pharyngeal arches: Embryonic structures that give rise to head and neck components.
Inferior parathyroid gland: Endocrine glands regulating calcium homeostasis, derived embryonically from the 3rd pharyngeal pouch.
Superior parathyroid gland: Derived from the 4th pharyngeal pouch.
Pharyngeal pouches: Internal endodermal outpouchings between pharyngeal arches.
Thymus: Develops from the 3rd pharyngeal pouch along with inferior parathyroids.
Branchial apparatus: Includes arches, pouches, clefts, and membranes involved in neck and facial development.
Calcium regulation: Parathyroid glands secrete parathyroid hormone (PTH) to maintain blood calcium levels.
Embryonic migration: Inferior parathyroids migrate downward with the thymus during development.
Developmental anomalies: Can lead to conditions like DiGeorge syndrome (3rd and 4th pouch defects).
Endoderm: The inner germ layer lining pharyngeal pouches, source of parathyroids and thymus.
Lead Question - 2012:
Inferior parathyroid develops from which arch?
a) 1st
b) 2nd
c) 3rd
d) 4th
Explanation & Answer:
The correct answer is c) 3rd arch (more precisely, the 3rd pharyngeal pouch). The inferior parathyroid glands arise embryologically from the endoderm of the 3rd pouch, along with the thymus. During development, they migrate caudally to their final position, which is lower than the superior parathyroids derived from the 4th pouch.
Q2. The superior parathyroid gland develops from which pharyngeal pouch?
a) 2nd
b) 3rd
c) 4th
d) 1st
Explanation & Answer:
The superior parathyroid gland develops from the 4th pharyngeal pouch (option c). It remains superior in position as compared to the inferior parathyroids which migrate downward.
Q3. Which structure develops from the 3rd pharyngeal pouch along with the inferior parathyroids?
a) Thymus
b) Thyroid
c) Parafollicular cells
d) Auditory tube
Explanation & Answer:
The thymus develops from the 3rd pharyngeal pouch along with the inferior parathyroid glands (option a). Both structures migrate caudally during embryogenesis.
Q4 (Clinical). DiGeorge syndrome is caused by developmental failure of which pharyngeal pouches?
a) 1st and 2nd
b) 3rd and 4th
c) 2nd and 3rd
d) 4th and 5th
Explanation & Answer:
DiGeorge syndrome results from failure of development of the 3rd and 4th pharyngeal pouches (option b), causing defects in the thymus and parathyroid glands leading to immunodeficiency and hypocalcemia.
Q5. Which germ layer forms the parathyroid glands?
a) Ectoderm
b) Mesoderm
c) Endoderm
d) Neural crest cells
Explanation & Answer:
The parathyroid glands develop from the endoderm (option c) lining the pharyngeal pouches. Neural crest cells contribute to other structures but not the parathyroids themselves.
Q6. During migration, the inferior parathyroid glands move alongside which organ?
a) Thyroid gland
b) Thymus
c) Parotid gland
d) Larynx
Explanation & Answer:
Inferior parathyroids migrate with the thymus (option b) from the 3rd pharyngeal pouch to their final lower position near the lower pole of the thyroid gland.
Q7. Which artery supplies the inferior parathyroid gland?
a) Superior thyroid artery
b) Inferior thyroid artery
c) Lingual artery
d) Facial artery
Explanation & Answer:
The inferior thyroid artery (option b) supplies the inferior parathyroid glands, which is important clinically during thyroid surgeries to avoid hypoparathyroidism.
Q8. Hypocalcemia in a newborn may result from failure of development of which structure?
a) Superior parathyroid
b) Inferior parathyroid
c) Both parathyroids
d) Adrenal medulla
Explanation & Answer:
Failure of development of either the inferior or superior parathyroids (option c) can lead to hypocalcemia due to decreased parathyroid hormone production.
Q9. The 1st pharyngeal pouch gives rise to?
a) Middle ear cavity and auditory tube
b) Thymus
c) Inferior parathyroid
d) Superior parathyroid
Explanation & Answer:
The 1st pharyngeal pouch (option a) forms the middle ear cavity and auditory (Eustachian) tube, not the parathyroid glands.
Q10 (Clinical). A patient with absent thymus and hypoparathyroidism may have a deletion of which chromosome region?
a) 22q11.2
b) 15q11
c) 7q31
d) 11p15
Explanation & Answer:
Deletion of chromosome 22q11.2 (option a) causes DiGeorge syndrome, characterized by absent thymus, hypoparathyroidism, and cardiac defects.
Subtopic: Blastocyst Formation and Differentiation
Keywords & Definitions:
Blastocyst: A structure formed in early embryogenesis, consisting of an outer layer and an inner cell mass.
Trophoblast: Outer layer of blastocyst that contributes to placenta formation.
Primitive streak: A structure that forms on the blastodisc and initiates gastrulation.
Yolk sac: An extraembryonic membrane involved in nutrient transfer in early development.
Embryo proper: The developing organism itself, arising from the inner cell mass.
Gastrulation: Process in which the three germ layers form from the epiblast.
Inner cell mass (ICM): Cluster of cells inside the blastocyst that gives rise to the embryo proper.
Placenta: Organ that develops from trophoblast and maternal tissue, facilitating nutrient exchange.
Extraembryonic membranes: Structures like yolk sac, amnion, and chorion that support the embryo.
Implantation: Process by which the blastocyst attaches to the uterine wall.
Lead Question - 2012:
The outer layer of the blastocyst forms ?
a) Primitive streak
b) Yolk sac
c) Embryo proper
d) Trophoblast
Explanation & Answer:
The correct answer is d) Trophoblast. The outer layer of the blastocyst is called the trophoblast, which plays a critical role in implantation and forms the fetal part of the placenta. The inner cell mass develops into the embryo proper, while the yolk sac and primitive streak arise later during development.
Q2. Which structure arises from the inner cell mass of the blastocyst?
a) Trophoblast
b) Primitive streak
c) Embryo proper
d) Chorion
Explanation & Answer:
The inner cell mass (ICM) of the blastocyst gives rise to the embryo proper (option c), which will develop into the fetus and some extraembryonic tissues. The trophoblast forms the outer layer, contributing to placenta formation.
Q3. The primitive streak appears during which embryonic stage?
a) Morula
b) Blastocyst
c) Gastrulation
d) Neurulation
Explanation & Answer:
The primitive streak forms during gastrulation (option c), marking the beginning of germ layer formation. It is not present at the morula or blastocyst stage and precedes neurulation.
Q4 (Clinical). Failure of proper trophoblast invasion can lead to which condition?
a) Ectopic pregnancy
b) Pre-eclampsia
c) Hydatidiform mole
d) Placenta previa
Explanation & Answer:
Insufficient trophoblast invasion into the uterine wall can cause pre-eclampsia (option b), a pregnancy complication characterized by hypertension and organ dysfunction.
Q5. The yolk sac in humans is primarily responsible for?
a) Formation of placenta
b) Early hematopoiesis
c) Neural tube development
d) Formation of amniotic fluid
Explanation & Answer:
The yolk sac (option b) acts as a site for early blood cell formation (hematopoiesis) and nutrient transfer during early embryonic life before the placenta fully develops.
Q6. During implantation, the trophoblast differentiates into?
a) Cytotrophoblast and syncytiotrophoblast
b) Epiblast and hypoblast
c) Amnion and yolk sac
d) Mesoderm and endoderm
Explanation & Answer:
The trophoblast differentiates into cytotrophoblast and syncytiotrophoblast (option a), which facilitate embryo implantation and invasion into the uterine lining.
Q7. Which layer eventually forms the amnion?
a) Inner cell mass
b) Trophoblast
c) Primitive streak
d) Hypoblast
Explanation & Answer:
The amnion develops from the epiblast, which is part of the inner cell mass (option a), forming a fluid-filled cavity that protects the embryo.
Q8. Which hormone is secreted by the trophoblast soon after implantation?
a) Estrogen
b) Progesterone
c) Human chorionic gonadotropin (hCG)
d) Luteinizing hormone (LH)
Explanation & Answer:
The syncytiotrophoblast secretes human chorionic gonadotropin (hCG) (option c), which maintains the corpus luteum and supports early pregnancy.
Q9. Primitive streak formation marks the beginning of which process?
a) Fertilization
b) Cleavage
c) Gastrulation
d) Organogenesis
Explanation & Answer:
The appearance of the primitive streak (option c) initiates gastrulation, during which the three germ layers—ectoderm, mesoderm, and endoderm—are formed.
Q10 (Clinical). Hydatidiform mole arises due to abnormal proliferation of which embryonic layer?
a) Inner cell mass
b) Trophoblast
c) Primitive streak
d) Hypoblast
Explanation & Answer:
Hydatidiform mole results from abnormal trophoblastic proliferation (option b), leading to a mass of swollen chorionic villi and pregnancy loss
Subtopic: Human Sex Chromosomes
Keywords & Definitions:
Y chromosome: One of the two human sex chromosomes, typically present in males.
Metacentric chromosome: Chromosome with centromere in the middle, arms roughly equal length.
Submetacentric chromosome: Chromosome with centromere slightly off-center, arms of unequal length.
Acrocentric chromosome: Chromosome with centromere near one end, producing a very short p arm.
Centromere: The constricted region of a chromosome where sister chromatids attach.
Chromosome morphology: The physical structure and shape of a chromosome.
Sex chromosomes: Chromosomes determining sex (X and Y in humans).
Chromosome arm: The segment of chromosome on either side of centromere (p - short arm, q - long arm).
Karyotype: The number and appearance of chromosomes in a cell.
Genetics: The study of genes and inheritance.
Lead Question - 2012:
Y chromosome is ?
a) Metacentric
b) Submetacentric
c) Acrocentric
d) None
Explanation & Answer:
The correct answer is c) Acrocentric. The human Y chromosome is acrocentric, meaning its centromere is located near one end, resulting in a very short p arm and a long q arm. This morphology differentiates it from metacentric and submetacentric chromosomes.
Q2. Which human chromosome pair is acrocentric besides the Y chromosome?
a) Chromosome 1
b) Chromosomes 13, 14, 15, 21, 22
c) Chromosome 16
d) Chromosome 18
Explanation & Answer:
Besides the Y chromosome, chromosomes 13, 14, 15, 21, and 22 are acrocentric. These have centromeres close to one end and carry satellite stalks important in ribosomal RNA gene clusters.
Q3. What is the typical shape of the X chromosome?
a) Metacentric
b) Submetacentric
c) Acrocentric
d) Telocentric
Explanation & Answer:
The X chromosome is typically submetacentric with the centromere off-center, giving unequal arm lengths, which contrasts with the acrocentric Y chromosome.
Q4 (Clinical). Turner syndrome is caused by which karyotype abnormality?
a) 45,X (monosomy X)
b) 47,XXY
c) 46,XY
d) 47,XYY
Explanation & Answer:
Turner syndrome results from monosomy X (45,X), where a female has only one X chromosome, leading to characteristic physical and reproductive abnormalities.
Q5. Which region on the Y chromosome is responsible for male sex determination?
a) SRY gene
b) SHOX gene
c) TDF gene
d) Both a and c
Explanation & Answer:
The SRY (Sex-determining Region Y) gene, also called TDF (Testis Determining Factor), is located on the Y chromosome and initiates male sex determination by triggering testis development.
Q6. What is the approximate size of the human Y chromosome?
a) 50 million base pairs
b) 20 million base pairs
c) 10 million base pairs
d) 100 million base pairs
Explanation & Answer:
The Y chromosome is small, approximately 57 million base pairs, roughly 2% of the total human genome, reflecting its limited gene content compared to autosomes and the X chromosome.
Q7. Which chromosome abnormality involves presence of an extra Y chromosome?
a) Klinefelter syndrome
b) XYY syndrome
c) Turner syndrome
d) Down syndrome
Explanation & Answer:
XYY syndrome results from an extra Y chromosome in males (47,XYY), often causing taller stature and sometimes behavioral issues, but usually normal fertility.
Q8. What type of chromosomal anomaly is a Robertsonian translocation?
a) Fusion of two acrocentric chromosomes
b) Duplication of chromosome segment
c) Deletion of chromosome arm
d) Inversion of chromosome segment
Explanation & Answer:
Robertsonian translocation is a chromosomal rearrangement where two acrocentric chromosomes fuse at their centromeres, reducing chromosome number but often maintaining genetic material.
Q9. The short arm of acrocentric chromosomes often contains which genes?
a) Ribosomal RNA (rRNA) genes
b) Hemoglobin genes
c) Immunoglobulin genes
d) Mitochondrial genes
Explanation & Answer:
The short arms of acrocentric chromosomes contain nucleolus organizer regions rich in ribosomal RNA genes essential for ribosome biogenesis.
Q10 (Clinical). Which syndrome is characterized by 47,XXY karyotype?
a) Klinefelter syndrome
b) Turner syndrome
c) Down syndrome
d) Edwards syndrome
Explanation & Answer:
Klinefelter syndrome is a male sex chromosome aneuploidy characterized by an extra X chromosome (47,XXY), causing hypogonadism, infertility, and tall stature.