Introduction to human endocrine system - class-XII

Hormones are secreted by the endocrine system. Endocrine glands do not have ducts. Their secretions (hormones) are secreted into the bloodstream. Discrete endocrine glands - these include the pituitary (hypophysis), thyroid, parathyroid, adrenal and pineal glands. Endocrine component of glands with both an endocrine and an exocrine function- these include the kidney, pancreas and gonads. 

Endocrine glands release hormones (chemical messengers) into the bloodstream to be transported to various organs and tissues throughout the body.

The gland is an endocrine gland as it released many hormones which travels to the target site cells through blood. Adrenal gland and thyroid gland are endocrine glands.

Endocrine glands are the glands of the endocrine system of our body that secretes their hormones, products, directly into the blood. Pineal gland, pituitary gland, pancreas, ovaries, testes, thyroid gland, parathyroid gland, hypothalamus and adrenal glands are the major endocrine glands. In contrast to these glands, some glands release their hormones with the help of a duct onto the epithelial surface and are called endocrine glands. Some of these are sweat gland, mammary gland, lacrimal gland, salivary gland, sebaceous gland, mucous gland etc. 

Hormones are used to communicate between organs and tissues to regulate physiological and behavioral activities, such as digestion, metabolism, respiration, tissue function, sensory perception, sleep, excretion, lactation, stress, growth and development, movement, reproduction, and mood.

A steroid hormone is a steroid that acts as a hormone. Steroid hormones can be grouped into two classes : Corticosteroids and sex steroids. Within those two classes are the five types according to the receptors to which they bind : glucocorticoid,  mineralocorticoids, androgens, estorgens and progesterone. 

Endocrine glands release hormones directly into the blood for transportation to the effector organ. The effector organ can also be called as a target organ. The major glands of the endocrine system include the pineal gland, pituitary gland, pancreas, ovaries, testes, thyroid gland, parathyroid gland, hypothalamus and adrenal glands.

Adenohypophysis is not under direct regulation of the hypothalamus. Neurohypophysis is under direct regulation of the hypothalamus.

(A) Goiter is the enlargement of the thyroid gland. A goiter is associated with the thyroid which is not functioning properly.

A. Role of epinephrine and non- epinephrine- They whip up metabolism for preparing the animal to face special conditions created by physical stress such as fall in BP or blood sugar, anger, fear etc..All these conditions require more energy which is provided by increasing heart rate, blood pressure, sugar level of blood.

Oxytocin- Milk ejection hormone
Glucagon- Increases blood sugar level
Adrenaline- Increases heart rate
Thyroxine- Increases BMR.

Endocrine glands are the part of an endocrine system that produces hormones and other secretions directly into the blood, They include pituitary gland, thyroid gland, ovaries, testis, hypothalamus, etc. Blood helps transport these hormones faster to the target organs, thereby helping in its action. So, the correct answer is option A.

1.       (B) The adrenal medulla secretes catecholamines which stimulate the breakdown of glycogen to increase the blood glucose concentration during emergency situations.

(D) The thyroid gland secretes thyroxine and triiodothyronine. Iodine is essential for the normal rate of hormone synthesis in the thyroid gland.

So, the correct answer is '(B) - (i) catecholamines, (ii) glycogen
(D) - (i) thyroxine, (ii) iodine'.

Endocrine glands lack ducts and pass their secretions into the surrounding blood for transport to the site of action. They are also called ductless glands. Their secretions are known as hormones.

The endocrine gland is called the ductless glands because there are no ducts in the glands. The products such as hormones are secreted and goes directly to the bloodstream. So there is no need for glands to collect and distribute the products, it just goes straight to the blood. Exocrine glands are the ones that do require ducts.

A. Pineal: It secretes a hormone named melatonin. It causes the concentration of pigment granules in the melanocytes, making the skin colour lighter in certain animals.

The function of endocrine glands in animals is to regulate chemical coordination. These glands secrete chemicals called hormones. 

Endocrine glands are glands of the endocrine system that secrete their products, hormones, directly into the blood rather than through a duct. So, they are called as ductless glands. 

Any of various glands producing hormonal secretions that pass directly into the bloodstream is called endocrine gland. The endocrine glands include the thyroid, parathyroids, anterior and posterior pituitary, pancreas, adrenals, pineal and gonads. They are also called as the ductless glands.

Thyroxine is secreted by the thyroid gland, and its deficiency due to lack of iodine leads to goitre. The other options contain incorrect pairings of glands, hormones, or functions.