Human Anatomy and Physiology

11. The part of the human eye on which the image is formed is

The part of the human eye on which the image is formed is

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pupil
cornea
retina
iris
This question was previously asked in
UPSC NDA-2 – 2020
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Light enters the human eye through the cornea, passes through the pupil (regulated by the iris), the lens, and then is focused on the retina. The retina is the light-sensitive tissue located at the back of the eye containing photoreceptor cells (rods and cones), where the image is formed and converted into electrical signals that are sent to the brain via the optic nerve.
The retina is the screen at the back of the eye where the image is formed by the lens system.
The cornea and lens are responsible for refracting (bending) light to focus it on the retina. The iris controls the size of the pupil, regulating the amount of light entering the eye. The image formed on the retina is real and inverted.

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12. Cartilage is NOT found in

Cartilage is NOT found in

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larynx
nose
ear
urinary bladder
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UPSC NDA-2 – 2020
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Cartilage is a type of flexible connective tissue found in various parts of the body that require support and flexibility. The larynx (voice box), nose, and ear all contain cartilage as a major structural component. The urinary bladder is a hollow muscular organ that stores urine; its wall is primarily composed of smooth muscle tissue, not cartilage.
Cartilage is a structural component of the skeletal system and certain organs, providing support and flexibility. It is different from muscle tissue, which forms the walls of organs like the urinary bladder.
Examples of locations where cartilage is found include joints (articular cartilage), ribs, trachea, bronchi, intervertebral discs, and the structures mentioned in options A, B, and C. The urinary bladder wall consists of the detrusor muscle, a type of smooth muscle.

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13. Light enters the eye through a thin membrane called

Light enters the eye through a thin membrane called

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retina
cornea
pupil
iris
This question was previously asked in
UPSC NDA-2 – 2020
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The correct answer is (B) cornea. The cornea is the transparent outer layer at the front of the eye that covers the iris, pupil, and anterior chamber. It is the first surface that light encounters when entering the eye.
The cornea acts as the eye’s outermost lens, controlling and focusing the entry of light into the eye.
The retina is the light-sensitive tissue lining the back of the eye. The pupil is the opening in the center of the iris that allows light to enter the eye. The iris is the colored part of the eye that controls the size of the pupil.

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14. Blood is a type of

Blood is a type of

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Epithelial tissue
Muscular tissue
Nervous tissue
Connective tissue
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UPSC NDA-2 – 2019
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Animal tissues are broadly classified into four primary types: epithelial tissue, connective tissue, muscle tissue, and nervous tissue. Each type has distinct structures and functions.
A) Epithelial tissue forms linings and coverings of surfaces and cavities, and constitutes glands.
B) Muscular tissue is responsible for movement through contraction.
C) Nervous tissue transmits electrical and chemical signals throughout the body.
D) Connective tissue supports, connects, or separates different types of tissues and organs. Connective tissues are characterized by having cells dispersed within an extracellular matrix. Blood consists of various cell types (red blood cells, white blood cells, platelets) suspended in a liquid extracellular matrix called plasma. Plasma accounts for a significant portion of blood volume and its components are produced by cells. Due to its structure (cells in an extracellular matrix) and function (connecting different parts of the body through transport), blood is classified as a specialized type of connective tissue.
– There are four main types of animal tissue: epithelial, connective, muscle, and nervous.
– Connective tissue supports and connects other tissues and organs.
– Blood consists of cells suspended in plasma, an extracellular matrix.
– Blood fits the definition and characteristics of connective tissue.
Other examples of connective tissue include bone, cartilage, adipose tissue (fat), and loose connective tissue found under the skin. Blood is sometimes considered a “fluid connective tissue” due to its liquid matrix (plasma).

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15. Melanin is the natural pigment that gives colour to human skin, hair a

Melanin is the natural pigment that gives colour to human skin, hair and the iris. It provides protection against

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Ultraviolet radiation
Infrared radiation
X-ray radiation
Short wave radio radiation
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UPSC NDA-2 – 2017
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The correct answer is A) Ultraviolet radiation.
Melanin is a pigment produced by melanocytes in the skin, hair, and eyes. Its primary function is to absorb harmful ultraviolet (UV) radiation from sunlight, thereby protecting the cells from DNA damage and reducing the risk of skin cancer.
The amount and type of melanin produced influence skin, hair, and eye color. More melanin provides greater protection against UV radiation. While skin provides some protection against other forms of radiation, melanin’s specific role as a pigment is most directly linked to absorption of UV radiation.

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16. Fluoride toothpaste is sometimes recommended because fluoride

Fluoride toothpaste is sometimes recommended because fluoride

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prevents plaque formation
hardens the enamel of the tooth
kills pathogenic bacteria
prevents tooth ache
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UPSC NDA-2 – 2016
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Fluoride toothpaste is sometimes recommended because fluoride hardens the enamel of the tooth.
Fluoride works by strengthening the tooth enamel through a process called remineralization. When fluoride is present in the mouth, it is incorporated into the crystalline structure of the enamel, forming fluorapatite. Fluorapatite is more resistant to acid dissolution than hydroxyapatite, the original mineral in enamel. This increased resistance helps protect teeth from decay caused by acids produced by bacteria in plaque, effectively hardening the enamel and making it more resilient to cavities.
While fluoride can have some antibacterial effects at higher concentrations, its primary mechanism for preventing cavities in toothpaste is by enhancing enamel remineralization and increasing its acid resistance. Brushing action and other ingredients help remove plaque, but fluoride itself doesn’t primarily prevent plaque formation. It helps prevent tooth decay, which is a common cause of toothache, but it is not a direct pain reliever.

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17. Which one among the following cells produces antibodies against a fore

Which one among the following cells produces antibodies against a foreign antigen ?

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Lymphocytes
Erythrocytes
Eosinophils
Platelets
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UPSC NDA-1 – 2024
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Lymphocytes produce antibodies against a foreign antigen.
Lymphocytes are a type of white blood cell crucial to the immune system. Specifically, B lymphocytes (B cells) are responsible for producing antibodies. Upon encountering an antigen, B cells differentiate into plasma cells, which are highly specialized in synthesizing and secreting large quantities of specific antibodies to target and neutralize the antigen.
Erythrocytes (red blood cells) transport oxygen. Eosinophils are granulocytes involved in defense against parasites and in allergic reactions. Platelets are involved in blood clotting. None of these cell types produce antibodies.

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18. Squamous epithelial cells are found in the inner lining of

Squamous epithelial cells are found in the inner lining of

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Oesophagus.
Small intestine.
Ducts of salivary gland.
Kidney.
This question was previously asked in
UPSC NDA-1 – 2021
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The correct answer is A) Oesophagus. The inner lining (mucosa) of the oesophagus in mammals is composed of non-keratinized stratified squamous epithelium.
– Squamous epithelium is characterized by flattened cells.
– Stratified squamous epithelium consists of multiple layers of squamous cells and is found in locations requiring protection against abrasion.
– The oesophagus is a tube that transports food from the mouth to the stomach, and its lining is subject to friction from food passage, making stratified squamous epithelium suitable.
– The small intestine is lined with simple columnar epithelium with microvilli, adapted for absorption.
– Ducts of salivary glands are typically lined with cuboidal or columnar epithelium.
– The kidney contains various epithelial types; Bowman’s capsule has simple squamous epithelium, while kidney tubules are lined with cuboidal epithelium. The oesophagus is a classic example of a lumen’s inner lining being primarily composed of stratified squamous epithelium.

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19. Colour vision in human eyes is the function of photoreceptor cells

Colour vision in human eyes is the function of photoreceptor cells named

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Rods
Cones
Blind spot
Fovea
This question was previously asked in
UPSC NDA-1 – 2017
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Colour vision in human eyes is the function of photoreceptor cells named Cones. The retina contains two main types of photoreceptor cells: rods and cones.
Rods are highly sensitive to light intensity and are responsible for vision in dim light conditions (scotopic vision). They are monochromatic, meaning they do not contribute to color perception. Cones are less sensitive to light but are responsible for detailed vision and color perception in bright light conditions (photopic vision). Humans typically have three types of cones, each sensitive to different ranges of wavelengths of light (corresponding roughly to red, green, and blue colors).
The blind spot is an area on the retina where the optic nerve leaves the eye; it contains no photoreceptors and thus causes a blind spot in vision. The fovea is a small central pit in the retina, densely packed with cones, and is responsible for sharp, central vision and high-resolution color vision. While important for color vision, the fovea is a region containing photoreceptors, not the photoreceptor type itself.

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20. Tissue is formed from cells in which:

Tissue is formed from cells in which:

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most cells are similar in structure and function.
all cells perform different functions.
all cells are different in structure.
all cells are different in both structure and function.
This question was previously asked in
UPSC Geoscientist – 2021
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A tissue is defined as a group of similar cells (and their extracellular matrix) that are organized together to perform a specific function. While tissues may contain more than one cell type, the predominant cells are typically similar in structure and specialized for the tissue’s function.
Tissues are formed by cells with similar structure and function working together.
Options B, C, and D describe scenarios where cells are primarily different in structure and function, which would not typically form a cohesive tissue performing a specialized role. Organs are made up of different types of tissues working together.

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