Human Anatomy and Physiology

21. Cells of which one of the following tissues in animals undergo contrac

Cells of which one of the following tissues in animals undergo contraction and relaxation?

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Muscular tissue
Connective tissue
Epithelial tissue
Nervous tissue
This question was previously asked in
UPSC Geoscientist – 2020
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Muscular tissue is the tissue in animals that undergoes contraction and relaxation.
Muscle cells ( myocytes or muscle fibers) contain specialized proteins, primarily actin and myosin, that interact to cause the cell to shorten (contract) and then return to its original length (relax). This ability is fundamental to movement in animals.
There are three types of muscular tissue: skeletal muscle, smooth muscle, and cardiac muscle. Skeletal muscle is responsible for voluntary movements, smooth muscle for involuntary movements in internal organs (like digestion and blood flow), and cardiac muscle is responsible for the pumping action of the heart. Connective tissue provides support, binds tissues together, and transports substances. Epithelial tissue covers body surfaces and lines cavities. Nervous tissue transmits electrical and chemical signals.

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22. Squamous epithelial cells are NOT found in:

Squamous epithelial cells are NOT found in:

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lining of the mouth.
oesophagus.
skin.
kidney tubules.
This question was previously asked in
UPSC Geoscientist – 2020
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Squamous epithelial cells are NOT typically found as the primary lining in kidney tubules.
Squamous epithelium consists of flattened, thin cells, often forming smooth, protective, or permeable linings. While stratified squamous epithelium forms protective layers in the mouth, oesophagus, and skin, kidney tubules are primarily lined by cuboidal or columnar epithelium, which are more involved in secretion and absorption. A portion of the loop of Henle in the kidney is lined by thin squamous cells, but the general lining of the tubules is not squamous.
Simple squamous epithelium is found in the lining of blood vessels (endothelium), air sacs of lungs (alveoli), and lining of body cavities (mesothelium). Stratified squamous epithelium provides protection against abrasion and is found in the epidermis of the skin, lining of the mouth cavity, oesophagus, and vagina. Cuboidal epithelium is found in kidney tubules, ducts of glands, etc., and columnar epithelium is found in the lining of the stomach and intestines.

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23. Which of the following statements for persons suffering from presbyopi

Which of the following statements for persons suffering from presbyopia is/are correct ?

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  • 1. They cannot distinguish colours.
  • 2. It usually develops with ageing.
  • 3. They wear either bi-focal lenses consisting of both concave and convex lenses or progressive lenses.

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1 only
2 only
1 and 3
2 and 3
This question was previously asked in
UPSC CDS-2 – 2024
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Statement 1 is incorrect, while statements 2 and 3 are correct.
– Presbyopia is a condition that affects the eye’s ability to focus, especially on near objects. It is a natural process that occurs with ageing, typically starting around the age of 40. The eye’s lens becomes less flexible, making it harder to adjust focus. Thus, statement 2 is correct.
– Difficulty distinguishing colours is associated with colour blindness (daltonism), which is a different condition and not typically related to presbyopia. Thus, statement 1 is incorrect.
– People with presbyopia often need corrective lenses to see clearly up close. Bifocal lenses have two distinct optical powers (for distance and near vision), while progressive lenses provide a smooth transition between multiple focal lengths. These are common solutions for correcting presbyopia, often combined with other refractive errors like myopia or hyperopia. Thus, statement 3 is correct.
Presbyopia is derived from the Greek word “presbys” meaning “old man” and “ops” meaning “eye”. It is a universal physiological change. Contact lenses and refractive surgery can also be options for correcting presbyopia in some cases.

24. A person can see near objects clearly through his eyes but cannot see

A person can see near objects clearly through his eyes but cannot see distant objects clearly. The possible reason(s) for this defect could be :

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  • 1. Excessive curvature of the eye lens.
  • 2. The eye-ball has become too small.
  • 3. The focal length of the eye lens is too large.
  • 4. Elongation of the eye-ball.

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1 only
2 and 4 only
1 and 4 only
1 and 3 only
This question was previously asked in
UPSC CDS-2 – 2023
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The correct answer is C) 1 and 4 only.
The condition described, seeing near objects clearly but not distant objects clearly, is known as Myopia or short-sightedness. Myopia occurs when the image of distant objects is focused in front of the retina instead of directly on it. This can be caused by:
1. Excessive curvature of the eye lens: This increases the refractive power of the lens, causing light rays to converge too strongly.
2. Elongation of the eye-ball: If the eyeball is too long from front to back, the retina is located behind the point where the image is focused by a lens of normal power.
Options 2 (eye-ball too small) and 3 (focal length of the eye lens is too large – which implies weaker power) would typically lead to Hypermetropia (far-sightedness), where the image is focused behind the retina.
Myopia is corrected by using a concave lens (diverging lens) which diverges the light rays before they enter the eye, causing them to focus further back, onto the retina. Hypermetropia is corrected using a convex lens (converging lens). Presbyopia, another common vision defect, is the loss of the eye’s ability to focus actively on nearby objects due to the hardening of the lens, usually occurring with age.

25. Fat in human body is stored in

Fat in human body is stored in

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Adipose tissue
Red blood cells
Muscle tissue
Epithelial tissue
This question was previously asked in
UPSC CDS-2 – 2022
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Fat in the human body is primarily stored in adipose tissue.
– Adipose tissue is a specialized connective tissue composed of adipocytes (fat cells).
– These cells store energy in the form of triglycerides (fat).
– Adipose tissue also provides insulation, protection for organs, and produces hormones.
– Red blood cells are involved in oxygen transport.
– Muscle tissue is primarily for movement.
– Epithelial tissue forms linings and coverings.
– While other tissues contain some lipids, adipose tissue is the body’s main storage site for large quantities of fat.

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26. Which one of the following is the special type of milk produced by a l

Which one of the following is the special type of milk produced by a lactating mother, essential for the development of immune response of newborn baby in human?

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Breast milk produced after a month of childbirth
Transitional milk
Colostrum
Mineralized milk
This question was previously asked in
UPSC CDS-2 – 2018
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Colostrum is the special type of milk produced immediately after childbirth that is essential for the development of the immune response of the newborn baby in human.
Colostrum is the first milk produced by the mother, typically in the first few days after birth. It is often described as “liquid gold” due to its yellowish color and immense nutritional and immunological value. It is significantly different from mature breast milk. Colostrum is particularly rich in immunoglobulins (antibodies), especially IgA, which provides passive immunity to the newborn, protecting them against various infections. It also contains leukocytes (white blood cells), growth factors, and nutrients highly suited for the newborn’s initial needs.
After colostrum, the composition of breast milk changes over approximately two weeks, becoming transitional milk, and then settles into mature milk. While mature milk continues to provide antibodies and nutritional support, colostrum has the highest concentration of immune components, making it uniquely crucial for establishing the newborn’s early immune defenses and gut health.

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27. The elemental composition of an adult human body by mass is

The elemental composition of an adult human body by mass is

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”C
”O
”N
”N
This question was previously asked in
UPSC CDS-2 – 2016
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The elemental composition of an adult human body by mass is dominated by Oxygen, followed by Carbon, Hydrogen, and Nitrogen.
Oxygen is the most abundant element by mass (approx. 65%), largely due to its presence in water (H₂O). Carbon (approx. 18.5%) forms the backbone of organic molecules. Hydrogen (approx. 9.5%) is also abundant in water and organic compounds. Nitrogen (approx. 3.2%) is a key component of proteins and nucleic acids.
These four elements constitute about 96-97% of the human body’s mass. Calcium and Phosphorus are the next most abundant elements, primarily found in bones and teeth.

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28. ‘Altitude sickness’ is caused at high altitude due to

‘Altitude sickness’ is caused at high altitude due to

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high partial pressure of oxygen
low partial pressure of oxygen
low level of haemoglobin
high partial pressure of carbon dioxide
This question was previously asked in
UPSC CDS-2 – 2016
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Altitude sickness is caused by exposure to low partial pressure of oxygen at high altitudes.
At higher altitudes, the atmospheric pressure is lower. This results in a lower partial pressure of oxygen, which reduces the amount of oxygen that can be taken up by the lungs and delivered to the body’s tissues, leading to hypoxia.
Symptoms of altitude sickness, also known as acute mountain sickness (AMS), can include headache, nausea, dizziness, fatigue, and shortness of breath. Severe forms include High Altitude Pulmonary Edema (HAPE) and High Altitude Cerebral Edema (HACE). Acclimatization is the process by which the body adjusts to the lower oxygen availability.

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29. Methanol is toxic because

Methanol is toxic because

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methanol coagulates the protoplasm
methanol gets oxidised to methanal in liver which coagulates the protoplasm
methanol gets oxidised to acetic acid in liver which coagulates the protoplasm
methanol gets oxidised to CO in liver which coagulates the protoplasm
This question was previously asked in
UPSC CDS-1 – 2024
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Methanol is toxic because it is metabolized into highly toxic substances in the body.
In the liver, methanol is oxidized by the enzyme alcohol dehydrogenase primarily into formaldehyde, which is also known as methanal. Formaldehyde is a potent toxin that can damage tissues, including causing the denaturation and coagulation of proteins, which is akin to coagulating protoplasm. Formaldehyde is further oxidized to formic acid, which contributes to metabolic acidosis.
The accumulation of formaldehyde and formic acid leads to the severe symptoms of methanol poisoning, including visual impairment (blindness), neurological damage, and potentially death.

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30. An antibacterial enzyme present in saliva and tears is called

An antibacterial enzyme present in saliva and tears is called

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ribozyme
lipase
lysozyme
isomerase
This question was previously asked in
UPSC CDS-1 – 2024
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Lysozyme is an enzyme that damages bacterial cell walls by catalyzing the hydrolysis of peptidoglycans, which are major components of bacterial cell walls. It is found in various bodily secretions, including saliva, tears, mucus, and egg white, and serves as part of the innate immune system.
Lysozyme is an enzyme found in saliva and tears that breaks down bacterial cell walls, providing antibacterial protection.
Ribozymes are RNA molecules with catalytic activity. Lipase is an enzyme that digests fats. Isomerase is an enzyme that catalyzes the rearrangement of atoms within a molecule. While lipase is present in saliva (lingual lipase), lysozyme is primarily known for its antibacterial action in saliva and tears.

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