Directions : In the following questions, a statement of assertion is followed by a statement of reason. Mark the correct choice as :
(a) If both assertion and reason are true and reason is the correct explanation of assertion.
(b) If both assertion and reason are true but reason is not the correct explanation of assertion.
(c) If assertion is true but reason is false.
(d) If assertion is false but reason is true.
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Assertion: Stomach and intestine of our body are lined by simple columnar epithelium.
Reason: Columnar epithelium helps in secretion and absorption.
(a) The columnar epithelium is composed of a single layer of tall and slender cells. Their nuclei are located at the base. Free surface may have microvilli. They are found in the lining of stomach and intestine and help in secretion and absorption.
Assertion: Cell junctions are present in the epithelium and other tissues.
Reason: Among cell junctions, adhering junctions help to stop substances from leaking across a tissue.
(c) All cells in epithelium are held together with little intercellular material. In nearly all animal tissues, specialised junctions provide both structural and functional links between its individual cells. Three types of cell junctions are found in the epithelium and other tissues. These are called as tight, adhering and gap junctions. Adhering junctions perform cementing function to keep neighbouring cells together.
Assertion: Connective tissues are the most abundant and widely distributed in the body of complex animals.
Reason: Connective tissues link and support other tissues or organs of the body.
(b) Connective tissue is the most abundant and widely distributed tissue of the body. It connects different tissues or organs and provides support to various structures of animal body. The connective tissue consists of living cells and extracellular matrix. It includes soft connective tissues and specialised tissues like cartilage, bone, adipose and blood.
Assertion: The cells of connective tissues except blood secrete fibres.
Reason: Fibres provide strength, elasticity and flexibility to the tissue.
(b) All cells of connective tissue except blood secrete fibres. Fibroblasts are the main cells of connective tissue, which secrete various types of fibres. There are three types of fibres secreted by connective tissue cells and each type is formed by proteins. These are collagen fibres (made up of collagen protein), elastic fibres (formed of elastin) and reticular fibres (made up of reticulin). All provide strength, elasticity and flexibility to the connective tissue.
Assertion: Ligament is made of white fibrous tissue.
Reason: Ligaments attach one bone to another bone.
(d) Tendon is made up of white fibrous tissue. Tendon connects a skeletal muscle to bone. It is tough and inelastic. Ligament is strong and elastic and made up of yellow elastic tissue with some collagen fibres. Ligament connects a bone to another bone.
Assertion: Smooth muscles are involuntary in nature.
Reason: Action of smooth muscles are controlled by autonomic nervous system.
(a) Smooth muscles are found in the posterior part of oesophagus, stomach, intestine, blood vessels, iris of eye, dermis of skin, etc. Action of these muscles is controlled by autonomic nervous system and hence they are not under the control of animal’s will.
Assertion: Neurons protect and support the neuroglial cells.
Reason: Neuroglial cells make up fifty percent of all brain cells.
(d) Neuroglia or neuroglial cells are specialised cells found in the brain and spinal cord supporting the neurons and their fibres. About 50 percent of all brain cells are neuroglial cells.
Assertion: The alimentary canal of the frog is short.
Reason: Frogs are carnivores.
(a) The digestive system of frog consists of alimentary canal and digestive gland. The alimentary canal of frog is short, It is because frog is carnivore. Carnivores have shorter digestive tracts as meat is easier to digest than plant material.
Assertion: There is hepatic portal system in frogs.
Reason: Hepatic portal system is venous connection between liver and intestine in frog.
(b) In frog, venous system has hepatic portal system. This system carries blood from the alimentary canal and its associated glands to the liver. It consists of a large hepatic portal vein that receives a number of tributaries from many organs.
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