Use the drop-down menus to indicate which endocrine structure is being described in each case. this structure secretes adrenaline, noradrenaline, cortisol, and aldosterone. this structure regulates the sleep cycle and other biological rhythms. this structure is located at the throat and regulates metabolism. this structure secretes glucagon and insulin. this structure regulates the development and differentiation of t lymphocytes. this structure regulates blood calcium levels.

1 - This structure secretes adrenaline, noradrenaline, cortisol, and aldosterone --- ADRENAL GLAND.

2 - This structure regulates the sleep cycle and other biological rhythms --- PINEAL GLAND.

3 - This structure is located at the throat and regulates metabolism --- THYROID GLAND.  

4 - This structure secretes glucagon and insulin --- PANCREAS.

5 - This structure regulates the development and differentiation of T lymphocytes --- THYMUS GLAND.

6 - This structure regulates blood calcium levels --- PARATHYROID GLANDS.

1) The adrenal glands are organs in the body that in humans sit just above the kidneys. The adrenal glands are endocrine organs, producing a number of important hormones, including adrenaline and cortisol.

2) The pineal gland is an endocrine gland in the brain. It secretes, among other things, melatonin into the bloodstream, to determine the circadian rhythm.

3) The thyroid gland stimulates metabolism, burning, heart rate and respiration. In addition, it promotes normal body development and contributes to body growth, nervous system development and fertility.

4) The pancreas is a mixed gland with endocrine and exocrine function. The dual secretion or secretion function of this organ consists of external secretion for digestion and internal secretion for carbohydrate metabolism.

5) The thymus gland is a specialized organ of the immune system. Specifically, the thymus gland provides an inductive environment for the growth of T-lymphocytes from progenitor hematopoietic cells.

6) The parathyroid glands produce a hormone that increase the calcium level in the blood, partly by increasing the activity of osteoclasts. Also, calcium absorption in the kidney is increased.

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The answers are:

1. Adrenal gland:
This structure secretes adrenaline, noradrenaline, cortisol, and aldosterone.

The adrenal gland is located above each kidney. It has two parts:
Adrenal Cortex - secretes cortisol and aldosterone. 
Adrenal Medulla - secretes adrenaline and noradrenaline. 

2. Pineal gland/Pineal body: 
This structure regulates the sleep cycle and other biological rhythms.

The pineal gland is located in the middle of the brain. It secretes the hormone melatonin, which regulates the wake and sleep cycle. 

3. Thyroid gland: 
This structure is located at the throat and regulates metabolism. 

The thyroid gland is found in the neck. It produces thyroid hormones that regulate metabolism. It also helps maintain blood pressure, heart rate, digestion, muscle tone and other reproductive functions. 

4. Pancreas:
This structure secretes glucagon and insulin.

The pancreas is located in the abdominal cavity, behind the lower part of the stomach. It secretes glucagon and insulin to regulate the glucose level in the blood. 

5. Thymus gland
This structure regulates the development and differentiation of T lymphocytes.

The thymus gland can be found in the thoracic cavity, in the mediastinum to be exact. T-lymphocytes are produced in the bone marrow, but they develop in the thymus. 

6. Parathyroid glands
This structure regulates blood calcium levels.
They come in two pairs and are embedded on they thyroid gland. It releases parathyroid hormone. This hormone helps regulate the calcium levels in the blood. 

Organelle A is chloroplasts

Organelle B is the vacuole

Explanation:

I don’t exactly understand what it means on which one is correct, but I hope this helps you.