← Combined Technical (NG)
Past Questions — 2025
Souring & gassiness of milk is caused by _______ group, which indicates the contamination of milk and its products.
A)
Lactic acid
B)
Bacillus lactis
C)
Coliform
D)
Streptococcus
Souring and gassiness in milk are characteristic signs of contamination by Coliform bacteria. Coliforms (such as Escherichia coli and Enterobacter) are facultative anaerobes that ferment lactose in milk, producing both lactic acid (which causes souring) and carbon dioxide/hydrogen gas (which causes gassiness or 'blowing' of the product). In dairy science, the presence of coliforms is used as a primary indicator of poor hygiene, fecal contamination, or inadequate pasteurization.
Why other options are incorrect:
- a. Lactic acid: This is a chemical byproduct of fermentation, not a 'group' of organisms that causes the contamination.
- b. Bacillus lactis: While some Bacillus species can cause spoilage (like sweet curdling), they are not the primary indicator group associated with simultaneous gassiness and souring in the context of contamination indicators.
- d. Streptococcus: While Streptococci are involved in the acidification of milk (especially in starter cultures for cheese/yogurt), they typically do not produce the significant amount of gas associated with 'gassiness' in contaminated milk.
The transmission of FMD virus may be completed through:
A)
Aerosol, milk, semen
B)
Aerosol and fomites
C)
Aerosol, feed and water
D)
All of the above
Foot-and-Mouth Disease (FMD) is caused by an Aphthovirus (family Picornaviridae) and is highly contagious. The virus is transmitted through several routes: 1. Aerosol: The virus can be spread through the air over significant distances, especially in crowded conditions. 2. Direct Contact and Fomites: Transmission occurs via contact with infected animals or contaminated objects (fomites) such as clothing, boots, and equipment. 3. Biological Fluids: The virus is shed in high concentrations in milk, semen, saliva, and nasal secretions. 4. Environmental Sources: Contaminated feed and water can serve as vehicles for the virus to enter a healthy herd. Since options a, b, and c all list valid transmission routes, the correct answer is 'All of the above'.
The stain generally used for identifying fungus is:
A)
Giemsa’s stain
B)
Lactophonol
C)
Lactophenol cotton blue
D)
Zeihl-Nelson stain
The correct stain for identifying fungi is Lactophenol Cotton Blue (LPCB).
1. **Lactophenol Cotton Blue (LPCB)**: This is the gold standard stain used in mycology. It consists of three main components:
- **Phenol**: Kills the fungus and prevents it from growing further.
- **Lactic Acid**: Preserves the fungal structures.
- **Cotton Blue**: An aniline dye that stains the chitin in the fungal cell walls, making the hyphae and spores appear deep blue against a light background, which allows for clear morphological identification.
2. **Why other options are incorrect**:
- **Giemsa’s stain**: Primarily used for staining blood smears to detect parasites (like Malaria) or for histological staining of cells.
- **Lactophonol**: This is likely a misspelling or an incomplete term; the active staining agent is the 'Cotton Blue' part of the LPCB mixture.
- **Zeihl-Neelsen stain**: This is an acid-fast stain specifically used to identify Mycobacterium species (like M. tuberculosis) and some other acid-fast bacteria, not general fungi.
The choice of disinfectant during the outbreak of CSF are:
A)
Sodium hypochloride, Caustic Soda, Potassium Permanganate
B)
Sodium hypochloride and Caustic Soda
C)
Sodium hydroxide and Potassium Permanganate
D)
Sodium hypochloride and Potassium Permanganate
Classical Swine Fever (CSF) is caused by a Pestivirus (family Flaviviridae). The virus is relatively resistant in the environment but is highly susceptible to alkaline substances and oxidizing agents.
1. **Sodium Hypochlorite (Bleach):** This is a powerful oxidizing agent and is widely recommended by the OIE (World Organisation for Animal Health) and other veterinary authorities for the disinfection of premises during CSF outbreaks because it effectively inactivates the virus.
2. **Caustic Soda (Sodium Hydroxide):** CSF virus is sensitive to high pH levels. Strong alkaline solutions like caustic soda are highly effective at denaturing the viral proteins and lipids, making it a standard choice for deep cleaning and disinfection of contaminated areas.
Regarding other options: Potassium Permanganate is generally not the primary choice for CSF disinfection compared to the potency of hypochlorites and strong alkalis. Therefore, the combination of Sodium Hypochlorite and Caustic Soda (Option b) represents the most effective and standard disinfectant protocol for managing a CSF outbreak.
The causative agent of greasy pig disease is:
A)
Erysipelothrix rhusiopathiae
B)
Staphylococcus hyicus
C)
Streptococcus suis
D)
Clostridium perfingens
Greasy Pig Disease, also known as Exudative Epidermitis, is a common skin infection in piglets caused by the bacterium Staphylococcus hyicus. This pathogen produces exfoliative toxins that cause the epidermis to separate, leading to the characteristic greasy, moist, and crusty skin lesions.
Analysis of other options:
- a. Erysipelothrix rhusiopathiae: Causes Erysipelas (diamond skin disease) in pigs, characterized by raised diamond-shaped skin lesions.
- c. Streptococcus suis: Primarily causes meningitis, arthritis, and lameness in pigs.
- d. Clostridium perfringens: Causes enterotoxemia and necrotic enteritis in various livestock, including pigs, but not greasy pig disease.
Koch’s postulate is not applicable to which of the following:
A)
Ebola
B)
Mastitis
C)
Collibacillosis
D)
Salmonellosis
Koch's postulates are a set of four criteria designed to establish a causative relationship between a microbe and a disease. The postulates require that: 1) The microorganism must be found in abundance in all organisms suffering from the disease but should not be found in healthy organisms. 2) The microorganism must be isolated from a diseased organism and grown in pure culture. 3) The cultured microorganism should cause disease when introduced into a healthy organism. 4) The microorganism must be re-isolated from the inoculated, diseased experimental host.
Option (a) Ebola is caused by the Ebola virus. Viruses are obligate intracellular parasites, meaning they cannot be grown in 'pure culture' on artificial agar media (a requirement of the second postulate); they require living host cells to replicate. Therefore, Koch's postulates in their original form are not applicable to viral diseases like Ebola.
Options (b), (c), and (d) refer to diseases typically caused by bacteria: Mastitis (often Staphylococcus aureus or Streptococcus), Collibacillosis (Escherichia coli), and Salmonellosis (Salmonella species). These bacteria can be isolated and grown in pure culture on synthetic media, making them compatible with Koch's postulates.
Enlist Eimeria of chicken, write the pathogenesis of hemorrhagic and non-hemorrhagic coccidiosis in chicken, their clinical manifestation, post-mortem lesions and their control strategies.
Deamination is the_______of amino group from/to amino acid which occurs in _______.
A)
release, kidney
B)
release, liver
C)
uptake, liver
D)
uptake, kidney
Step-by-step reasoning:
1. **Definition of Deamination**: In biochemistry, deamination is the process by which an amino group (-NH2) is removed (released) from an amino acid. This process typically converts the amino acid into a keto acid and ammonia.
2. **Chemical Process**: The most common form is oxidative deamination, where the enzyme glutamate dehydrogenase removes the amino group from glutamate, releasing free ammonia (NH3).
3. **Location of Occurrence**: While some deamination can occur in various tissues, the primary site for the bulk of amino acid catabolism and the subsequent conversion of toxic ammonia into urea (via the Urea Cycle) is the liver. The liver possesses the high concentrations of enzymes required to handle the nitrogenous waste produced during this process.
4. **Evaluating Options**:
- Option (a): Incorrect. While the kidney handles excretion, the primary site of deamination is the liver.
- Option (b): Correct. It identifies the 'release' of the amino group and the 'liver' as the primary site.
- Option (c): Incorrect. 'Uptake' refers to amination or transamination, not deamination.
- Option (d): Incorrect. Both 'uptake' and 'kidney' are incorrect in this context.
The animal species which is most susceptible for tetanus is _______.
A)
dog
B)
horse
C)
cattle
D)
sheep
Tetanus is caused by the neurotoxin tetanospasmin produced by the bacterium Clostridium tetani. Susceptibility to tetanus varies significantly among animal species due to differences in the binding affinity of the toxin to the receptors in the central nervous system. Horses are recognized as the most susceptible species because they possess a high density of receptors for the tetanospasmin toxin, leading to severe clinical signs even with small amounts of the toxin. In contrast, cattle and sheep are moderately susceptible, and dogs are generally less susceptible than horses. This high sensitivity in horses is why they are frequently used in the production of tetanus antitoxin (hyperimmune serum), as they mount a strong response to the toxoid.
Hypoglycemia in piglets is due to:
A)
Inefficient glycolysis
B)
Inefficient TCA cycle
C)
Insufficient colostrum and milk intake
D)
Inefficient gluconeogenesis
Piglets are born with very low glycogen stores in the liver and muscles. Unlike adult animals, neonate piglets have a limited capacity for gluconeogenesis (the metabolic pathway that generates glucose from non-carbohydrate sources like amino acids and glycerol) during the first few days of life. Because they cannot synthesize glucose efficiently on their own, they are highly dependent on the external intake of lactose from colostrum and milk to maintain blood glucose levels. While insufficient milk intake (option c) can lead to hypoglycemia, the underlying physiological 'cause' or vulnerability in the piglet's system is the inefficient gluconeogenic capacity. Therefore, in a physiology context, the metabolic deficiency is inefficient gluconeogenesis.
What is rabies? What is the etiology, transmission pattern, pathogenesis, clinical manifestation in man and in animals and control strategies of rabies?
Reproductive problems is the most obvious clinical signs in the infection of pigs among the disease listed below:
A)
CSF
B)
ASF
C)
PRRS
D)
Swine Influenza
Step-by-step reasoning: 1. Analysis of PRRS (Porcine Reproductive and Respiratory Syndrome): PRRS is characterized by a dual impact on the reproductive and respiratory systems. In sows, the virus causes severe reproductive failure, including abortions, stillbirths, mummified fetuses, and reduced litter sizes. This makes reproductive problems the most 'obvious' and hallmark clinical sign of the disease. 2. Analysis of CSF (Classical Swine Fever): While CSF can cause abortions, it is primarily a systemic hemorrhagic fever characterized by high fever, skin discoloration (cyanosis), and high mortality across all ages. 3. Analysis of ASF (African Swine Fever): ASF is a highly contagious hemorrhagic disease. While it can cause fetal death in pregnant sows, the primary clinical signs are high fever, anorexia, and severe systemic hemorrhage leading to rapid death. 4. Analysis of Swine Influenza: This is primarily a respiratory disease causing coughing, sneezing, and fever; it does not typically present with primary reproductive failure. Conclusion: Among the listed options, PRRS is the only disease where reproductive failure is a defining, primary clinical characteristic of the syndrome.
Mycobacterium bovis is:
A)
Gram positive, contains high lipid layer in the cell wall, spore forming
B)
Gram positive, contains high lipid layer in the cell wall, non-spore forming
C)
Gram negative, contains low lipid layer in the cell wall, spore forming
D)
Gram positive, contains low lipid layer in the cell wall, non-spore forming
Step-by-step analysis of Mycobacterium bovis characteristics:
1. **Gram Stain Status**: Mycobacterium species are phylogenetically related to Gram-positive bacteria. Although they often stain weakly or irregularly with the Gram stain due to their unique cell wall, they are classified as Gram-positive.
2. **Cell Wall Composition**: The hallmark of the genus Mycobacterium is a cell wall exceptionally rich in lipids, specifically mycolic acids (long-chain fatty acids). This high lipid content makes them 'acid-fast,' meaning they resist decolorization by acid-alcohol after staining with carbol fuchsin.
3. **Spore Formation**: Mycobacteria are non-spore forming bacteria. Endospore formation is a characteristic primarily associated with the genera Bacillus and Clostridium, not Mycobacterium.
Comparing these facts to the options:
- Option (a) is incorrect because it claims the organism is spore-forming.
- Option (b) is correct: Gram-positive, high lipid layer (mycolic acids), and non-spore forming.
- Option (c) is incorrect because it claims the organism is Gram-negative and spore-forming.
- Option (d) is incorrect because it claims the organism has a low lipid layer.
In nature pH level ranges from:
A)
0-14
B)
1-12
C)
1-10
D)
2-10
The pH scale is a logarithmic scale used to specify the acidity or basicity of an aqueous solution. It is defined as the negative logarithm (base 10) of the molar concentration of hydrogen ions ([H+]) in a solution: pH = -log10[H+].
1. The standard pH scale typically ranges from 0 to 14.
2. A pH of 7 is considered neutral (like pure water at 25°C).
3. A pH value less than 7 indicates an acidic solution (0 to 6.9).
4. A pH value greater than 7 indicates a basic or alkaline solution (7.1 to 14).
While it is theoretically possible to have pH values slightly outside this range in extremely concentrated acids or bases, for all standard educational, biological, and natural chemistry contexts, the range is defined as 0-14. Options b, c, and d are incorrect as they arbitrarily restrict the known range of the pH scale.
The final product of oxidative phosphorylation is:
A)
NADH
B)
ATP
C)
FADH2
D)
All of the above
Oxidative phosphorylation is the final stage of cellular respiration, occurring in the inner mitochondrial membrane. It consists of two closely linked components: the Electron Transport Chain (ETC) and Chemiosmosis.
1. The process begins with the oxidation of NADH and FADH2 (which are inputs/substrates, not final products), releasing electrons that move through the ETC.
2. As electrons move, protons (H+) are pumped into the intermembrane space, creating an electrochemical gradient.
3. This gradient drives protons back into the mitochondrial matrix through the enzyme ATP synthase.
4. The energy from this proton flow is used to phosphorylate ADP into ATP (Adenosine Triphosphate).
Therefore, ATP is the final energy-carrying product of this process. NADH and FADH2 are consumed during the process, making them reactants rather than final products.
One among the listed is true for Listeria.
A)
Gram positive, can grow in 4°C
B)
Gram positive, cannot grow in 4°C
C)
Gram negative, can grow in 4°C
D)
Gram positive, cannot grow in 4°C
Listeria monocytogenes is a Gram-positive, non-spore-forming, facultative anaerobic bacterium. One of its most distinguishing characteristics in food microbiology is its psychrotrophic nature, meaning it has the ability to grow at refrigeration temperatures (typically around 4°C). This characteristic makes it a significant concern for food safety, as it can multiply in chilled, ready-to-eat foods where other pathogens are inhibited.
Analysis of options:
- Option (a) is correct because Listeria is Gram-positive and psychrotrophic (can grow at 4°C).
- Option (b) is incorrect because it claims Listeria cannot grow at 4°C.
- Option (c) is incorrect because Listeria is Gram-positive, not Gram-negative.
- Option (d) is a duplicate of (b) and is incorrect for the same reason.
Example of algal zoonosis:
A)
Scrub typhus
B)
Actinomycosis
C)
Fascioliasis
D)
Protothecosis
Step-by-step reasoning:
1. Analysis of the term 'Algal Zoonosis': This refers to a disease caused by an alga that can be transmitted from animals to humans.
2. Evaluating Option (d) Protothecosis: This disease is caused by Prototheca species, which are achlorophyllous (non-photosynthetic) algae. It is a zoonotic infection often transmitted from livestock (especially cattle) to humans, typically manifesting as cutaneous or systemic infections. This fits the definition of an algal zoonosis.
3. Evaluating Option (a) Scrub typhus: This is caused by the bacterium Orientia tsutsugamushi and transmitted by larval mites. It is a bacterial zoonosis, not algal.
4. Evaluating Option (b) Actinomycosis: This is caused by Actinomyces bacteria (filamentous bacteria). While it can be zoonotic (e.g., 'lumpy jaw' in cattle), it is a bacterial infection, not algal.
5. Evaluating Option (c) Fascioliasis: This is caused by liver flukes (trematodes) such as Fasciola hepatica. It is a parasitic zoonosis, not algal.
Conclusion: Protothecosis is the only option caused by an algal organism.
_______ is the type of vaccination that is practiced both within and around the region where an outbreak had occurred.
A)
Ring vaccination
B)
Strategic vaccination
C)
Barrier vaccination
D)
Suppressive vaccination
Ring vaccination is an epidemiological strategy used to contain an outbreak of an infectious disease. It involves vaccinating a 'ring' of people (or animals) around a confirmed case. This includes: 1) The immediate contacts of the infected individual, and 2) The contacts of those contacts (the surrounding region). By creating a buffer of immune individuals, the chain of transmission is broken, effectively isolating the outbreak and preventing it from spreading further.
Why other options are incorrect:
- Strategic vaccination: This is a general term for planning vaccination based on risk assessment but does not specifically describe the 'ring' pattern around an outbreak.
- Barrier vaccination: While similar in concept (creating a wall of immunity), barrier vaccination is typically used to protect a specific healthy population from an encroaching disease front (like a geographic line), rather than encircling a specific outbreak point.
- Suppressive vaccination: This refers to the mass vaccination of a population to reduce the prevalence of a disease or lower the number of susceptible individuals in a general population, rather than targeting a specific outbreak ring.
During urine analysis, the level of bilirubin is quantified for:
A)
Acidity
B)
Kidney stone
C)
Liver disease
D)
UTI
Bilirubin is a byproduct of the breakdown of hemoglobin in red blood cells. Normally, the liver conjugates bilirubin and excretes it into the bile, which then enters the intestines. In a healthy individual, bilirubin is not found in the urine because conjugated bilirubin is the only form that can be filtered by the kidneys, and it is typically processed by the liver and gallbladder. However, when there is liver disease (such as hepatitis or cirrhosis) or a blockage in the bile duct (obstructive jaundice), conjugated bilirubin builds up in the bloodstream and is excreted by the kidneys into the urine (bilirubinuria).
Why other options are incorrect:
- a. Acidity: Urine acidity is measured by pH levels, not bilirubin.
- b. Kidney stone: Kidney stones are typically detected via imaging (ultrasound/CT) or by looking for hematuria (blood in urine) and crystals, not bilirubin.
- d. UTI (Urinary Tract Infection): UTIs are diagnosed by detecting leukocytes (white blood cells), nitrites, or bacteria in the urine, not bilirubin.
Clonorchiosis is an example of :
A)
Metazoonosis subtype II
B)
Metazoonosis subtype III
C)
Metazoonosis subtype IV
D)
Cyclozoonosis
Clonorchiosis is caused by the liver fluke Clonorchis sinensis. To determine the correct classification, we must look at the definition of Metazoonoses (zoonoses requiring an invertebrate vector or intermediate host for completion of the life cycle).
1. Metazoonosis Subtype I: Transmission occurs via biological vectors (e.g., plague).
2. Metazoonosis Subtype II: Transmission occurs via biological vectors, but the parasite is not transmitted by the vector (e.g., certain filarial worms).
3. Metazoonosis Subtype III: Transmission occurs via an intermediate host where the parasite undergoes development, and the human is infected by consuming the intermediate host (e.g., Clonorchiosis, where humans eat undercooked fish containing metacercariae).
4. Metazoonosis Subtype IV: Transmission occurs via an intermediate host, but the human is infected by a vector (e.g., certain types of malaria/leishmaniasis).
Cyclozoonosis refers to zoonoses that require more than one vertebrate host to complete the life cycle. Since Clonorchis sinensis requires a snail (mollusk) and a fish (vertebrate) but is categorized specifically under the metazoonosis framework due to the essential role of the invertebrate intermediate host (snail) and the specific mode of transmission via the second intermediate host (fish), it fits the definition of Metazoonosis Subtype III.
Arrange the following in the chronological order:
A)
Adult, sporocyst, miracidium, redia, cercaria, metacercaria
B)
Adult, miracidium, redia, sporocyst, cercaria, metacercaria
C)
Adult, miracidium, sporocyst, redia, cercaria, metacercaria
D)
Adult, redia, sporocyst, miracidium, cercaria, metacercaria
The question asks for the chronological order of the life cycle stages of a typical digenean trematode (fluke). The standard life cycle proceeds as follows: 1. Adult: The mature worm resides in the definitive host and produces eggs. 2. Miracidium: The ciliated larva that hatches from the egg and swims to find the first intermediate host (usually a snail). 3. Sporocyst: Once inside the snail, the miracidium transforms into a sporocyst. 4. Redia: The sporocyst produces rediae through asexual reproduction. 5. Cercaria: Rediae produce cercariae, which are the free-swimming larval stages that leave the snail. 6. Metacercaria: The cercariae encyst in a second intermediate host or on vegetation to become metacercariae, which are then ingested by the definitive host. Comparing this sequence to the options: Option (c) matches this biological progression exactly.
Select the most correlating pathogens and the disease they cause:
A)
Brooders pneumonia (Aspergillus), Ephemeral fever (Rhabdoviridae), Infectious coryza (Haemophilus), PRRS (Arterivirus)
B)
Brooders pneumonia (Histoplasma), Ephemeral fever (Rhabdoviridae), Infectious coryza (Haemophilus), PRRS (Adenovirus)
C)
Brooders pneumonia (Aspergillus) Ephemeral fever (Rhabdoviridae), Infectious coryza (Birnavirus), PRRS (Arterivirus)
D)
Brooders pneumonia (Aspergillus), Ephemeral fever (Flavivirus), Infectious coryza (Retrovirus), PRRS (Parvovirus)
To determine the correct option, we must verify the causative agents for each of the four listed diseases:
1. **Brooder Pneumonia**: This is caused by the fungus *Aspergillus fumigatus*. It typically affects young chicks in brooding houses due to contaminated litter.
2. **Ephemeral Fever (Three-Day Sickness)**: This is caused by the Ephemeral Fever Virus (EFV), which belongs to the family *Rhabdoviridae* (genus *Rhabdovirus*).
3. **Infectious Coryza**: This is a respiratory disease of poultry caused by the bacterium *Avibacterium paragallinarum* (formerly known as *Haemophilus paragallinarum*). In many textbooks and exam contexts, it is still referred to under the *Haemophilus* genus.
4. **PRRS (Porcine Reproductive and Respiratory Syndrome)**: This is caused by the PRRS virus, which is a member of the genus *Arterivirus* within the family *Arteriviridae*.
Comparing this to the options:
- **Option a**: Matches all four (Aspergillus, Rhabdoviridae, Haemophilus, Arterivirus).
- **Option b**: Incorrect. Brooder pneumonia is not caused by *Histoplasma*, and PRRS is not caused by an *Adenovirus*.
- **Option c**: Incorrect. Infectious coryza is bacterial, not caused by a *Birnavirus*.
- **Option d**: Incorrect. Ephemeral fever is not a *Flavivirus*, Coryza is not a *Retrovirus*, and PRRS is not a *Parvovirus*.
In the blood, oxygen binds to hemoglobin of the red blood cells (RBCs) to form _______ and is carried to the body’s tissues.
A)
2-Haemoxyglobin
B)
Oxyhaemoglobin
C)
Beta-haemoxyglobin
D)
Oxyglobinogen
Step-by-step reasoning: 1. Hemoglobin is a complex protein found in red blood cells (RBCs) that contains iron atoms capable of binding to oxygen molecules. 2. When oxygen binds to the heme groups of hemoglobin in the lungs (where oxygen concentration is high), it forms a reversible chemical complex. 3. This oxygenated form of hemoglobin is scientifically termed 'Oxyhaemoglobin' (or Oxyhemoglobin). 4. This complex then travels through the bloodstream to the body's tissues, where the oxygen is released due to lower partial pressure of oxygen in the tissues. Analysis of options: Option (a) '2-Haemoxyglobin' and (c) 'Beta-haemoxyglobin' are non-standard, fabricated terms. Option (d) 'Oxyglobinogen' is incorrect as 'globinogen' is not a recognized term for the oxygen-carrying complex of hemoglobin.
McLean County system is applicable only in Ascaris suum infection among the ascarid worm due to:
A)
Absence of somatic migration of the larvae
B)
Presence of somatic migration
C)
The large size stage two larva
D)
Thick albuminous covering of the egg
The McLean County system is a diagnostic method used to estimate the worm burden (the number of adult worms) in a host based on the fecal egg count (FEC). For this system to be applicable, there must be a predictable and stable relationship between the number of eggs shed in the feces and the number of adult worms present in the intestine. In Ascaris suum (the pig roundworm), the larvae undergo a complex 'somatic migration' (hepato-tracheal migration) where they travel through the liver and lungs before reaching the small intestine. This migration process is critical because it ensures that only a certain percentage of ingested larvae survive to become adults, and the timing of this migration creates a specific pattern of egg shedding. The presence of this somatic migration phase is a defining characteristic of the Ascaris life cycle that allows for the mathematical modeling used in the McLean County system to correlate egg output with the adult population. Options a, c, and d are incorrect because the absence of migration would change the population dynamics, and the size of the larva or the thickness of the eggshell are physical characteristics that do not dictate the mathematical applicability of the worm-burden estimation system.
The release of egg from ovary during oestrus/menstrual is stimulated by_______.
A)
Surge of LH level
B)
Dip in the LH level
C)
Surge in the FSH
D)
Dip in the FSH
The release of a mature egg from the ovary (ovulation) is triggered by a sharp increase in the levels of Luteinizing Hormone (LH), known as the 'LH surge'.
Step-by-step reasoning:
1. During the follicular phase, Follicle Stimulating Hormone (FSH) promotes the growth of ovarian follicles.
2. As the follicle matures, it secretes increasing amounts of estrogen.
3. Once estrogen levels reach a high threshold, they switch from providing negative feedback to positive feedback on the pituitary gland.
4. This positive feedback triggers a massive release of LH (the LH surge).
5. The LH surge induces the final maturation of the oocyte and causes the rupture of the follicle wall, resulting in the release of the egg (ovulation).
Why other options are incorrect:
- Option b: A dip in LH would prevent ovulation from occurring.
- Option c: While FSH also peaks slightly during ovulation, it is the LH surge that is the primary and essential trigger for the rupture of the follicle.
- Option d: A dip in FSH does not stimulate the release of the egg.