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Control and Coordination — BIOLOGY STD 8 — Question

ICSE BoardEnglish MediumSTD 8BIOLOGYControl and Coordination4 Marks
Question
What are endocrine glands ?
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Answer

The specialised tissues that release, chemical substances that is hormones in trace amounts are called endocrine glands.$-$ The endocrine glands do not have ducts, so they are called ductless glands. These glands put their secrefrous directly into the blood. Hormones are the chemical messengers which help to control and
coordinate various activities in the body. The various endocrine glands are.
$(a)$ Pituitary gland : It is called the master gland as it secretes many hormones and some of these hormones control other endocrine glands. It is present at the base of the brain. It releases the growth hormone which controls the growth of the body.
$(b)$ Thyroid gland : It is present in the throat region. It produces thyroxine hormone which controls the speed of cellular metabolism especially, the rate at which oxygen is consumed and. energy is produced.
$(c)$ Parathyroid glands : Parathyroid glands are four small glands attached to the thyroid gland. It releases parathyroxine or parathormone. This hormone controls the amount of calcium and phosphorus in the body, which plays an important role in muscle contraction.
$(d)$ Pancreas : Pancreas is both exocrine as well as endocrine gland. It has a duct w’hich secretes pancreatic juice which helps in digestion. Pancreas also contains an endocrine tissue called Islets of Langerhans which produce insulin. Insulin controls the amount of glucose in the blood.
$(e)$ Adrenal glands : One adrenal gland is present above each of the two kidneys. Adrenal glands produce the hormone adrenalin. Adrenalin is released when person is under stress or involved in intensive exercise. It makes the heart beat faster, increases the flow of blood to the brain and helps to cope with stress.
$(f)$ Ovaries and testes : Ovaries produces female hormones progesterones and oestrogen. Testes produces male hormone testosterone. These hormones control growth, development and reproductive behaviour. These hormones are related to appearance of secondary sexual- character in both males and females.
Gland Location Main Hormone secreted by it Functions
pituitary at the base
of the brain		 growth
hormone		 regulates growth
thyroid throat region thyroxine regulates rate of growth and metabolism
parathyroid throat region parathormone Regulates calcium and phosphorus level
pancreas abdomen
$($near the small intenstine$)$		 insulin in
blood		 regulates amount of glucose in blood
adrenal above kidneys Adrenalin helps a person to cope with an emergency
Ovaries $($females$)$ lower
abdomen		 Oestrogen.
progesterone		 Control reproductive
growth and development, and reproductive behavior.
Testes $($males$)$ scrotum testosterone Controls reproductive growth and
development, and reproductive
behaviour

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