The human endocrine system

Modern Endocrinology originated in the 20th century based on the work of French physiologist Claude Bernard who made an observation that our body has a constant internal environment and he called it Milieu intérieur. He said that multicellular organisms have the physiological capacity to ensure protective stability for tissues and organs. We call this homeostasis today.

The human body system is complex and in order to operate in an organized manner, it needs to have a control over the cells, tissues, organs and organ systems in order to make growth, development and reproduction possible. It is regulated mainly by three systems – the nervous system, the immune system, and the endocrine system. While the nervous system controls movements and coordinates our body functions, and immune system protects it.

The endocrine system controls many bodily functions like –

• Respiration
• Metabolism
• Reproduction
• Sensory perception
• Movement
• Sexual development
• Growth
• Homeostasis (the internal balance of body systems)

Hormones

How do you come to know when you are hungry? Hormones are chemical substances that act like messengers in the body. When your body requires food, the stomach sends a signal by releasing a hormone that tells your brain that you are hungry and then the brain guides you to ask your Mom to give you something to eat! Many other such signals in the body are triggered by organs known as glands of the endocrine system. Thus, hormones are regulatory substances secreted by endocrine glands that are transported in blood to stimulate specific cells and tissues into action. Put your knowledge to the test with this challenging 6th Grade Science Worksheet! Read each question carefully and choose the response that you feel is correct.

Endocrine glands

Many of the hormones that the endocrine system manufactures and secretes interact with the skeletal system. These hormones play a role in bone remodeling, bone maintenance, and bone growth control. The endocrine system comprises of a network of glands that are small but highly important organs that produce, store and secrete hormones. They are ductless and secrete the hormones directly into the blood stream. Below is the list of the main endocrine glands in a human body –

1. Hypothalamus

Location – Within the Brain

Function – Hormones secretes by the hypothalamus regulate heart rate, blood pressure, sleep, appetite, thirst and regulation of body water and temperature. They also influence the brain, the nervous system and other endocrine glands. Thus it is responsible for body’s internal balance which is known as homeostasis.

2. Pineal gland

Location – Deep in the center of the brain

Function – Its function isn’t fully understood and is believed to influence our internal body clock and sleep patterns by secreting a hormone called melatonin.

3. Pituitary gland

Location – Base of the Brain

Function – It is the master gland, the size of a pea that controls other endocrine glands and produces the hormones that trigger growth, development, metabolism and reproduction. The main hormones secreted by pituitary are the Human Growth Hormone (GH) that stimulates growth in all tissues including bones and muscles. A hormone called Thyroid-Stimulating Hormone (TSH) secreted by the pituitary activates the thyroid gland to release thyroid hormones crucial for metabolism. Other hormones secreted by the pituitary gland control reproduction, pleasure centers, pain reliefs, pigmentation and water balance in the body.

4. Thyroid gland

Location – Front and base of the neck, below the Adam’s apple

Function – Shaped like a butterfly, the thyroid produces several hormones like thyroxine or T4 that are associated with metabolism, growth and development of the human body. Alternately, it controls the body temperature, calorie burning and heart rate. At your age, it helps in brain development.

5. Parathyroid glands

Location – Four parathyroid glands located behind the thyroid gland

Function – Parathyroid hormone controls and regulates the amount of calcium and phosphorus in the body.

6. Thymus gland

Location – Behind the sternum and between the lungs

Function – It helps in the development of our immune system by releasing a hormone called thymosine. It stimulates the development of disease fighting cells in our body. The gland is only active until puberty.

7. Adrenal glands

Location – Two glands, one located on top of each kidney

Function – Adrenal glands produce hormone like adrenaline and cortisol. Adrenaline triggers the body’s fight or flight response. Cortisol mediates stress responses by regulating metabolism, inflammatory response and immune function. Other hormones secreted by adrenal glands maintain the levels of sodium, chloride and potassium levels in the body and thus maintain blood pressure and helps control kidney functions.

8. Pancreas

Location – Deep in the abdomen behind the stomach

Function –The pancreas is a component of the digestive system and endocrine systems. The hormones of the pancreas regulate blood sugar levels and also regulate the use and storage of nutrients like glucose, amino acids and triglycerides obtained from food. The most important hormone secreted by the pancreas is insulin. Pancreas also plays a role in digestion by secreting enzymes.

9. Ovaries (in females)

Location – Inside the lower abdomen

Function – The ovaries produce estrogen and progesterone. Estrogen regulates development of female sexual characteristics during puberty and aids reproductive functions. Progesterone helps fertilized egg to attach to the uterus and develop into an embryo.

10. Testes (in males)

Location – A set of two underneath the penis

Function – Testes produce hormones known as androgens including testosterone. Testosterone is responsible for development of male sexual characteristics during puberty. Androgens influence the growth of body tissues, including muscles.

So the endocrine system is a network of glands in our body that secrete hormones that enable cells to ‘talk’ to each other. Interestingly it has its own feedback system that helps in regulating their balance in the body. Exercise and a good balanced diet including vitamins and minerals in right quantities are necessary for a healthy endocrine system. Hormone imbalances can be caused by unhealthy lifestyle, inadequate nutrition, stress and environmental toxins. The most common endocrine disorders include Diabetes, Hypo and Hyperthyroidism, osteoporosis, and PCOD (polycystic ovary syndrome).Doubts? A 6th-grade science tutor can help.

Check point

1. The chemical messenger substances secreted by endocrine glands are known as ________.
2. The Thyroid Stimulating Hormone or TSH is secreted by the ________ gland.
3. Name a hormone secreted by the thyroid gland.
4. Which gland secretes the hormone Adrenaline?
5. Name two disorders related to the endocrine system.

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Picture credits

https://www.hormone.org/what-is-endocrinology/the-endocrine-system

https://www2.estrellamountain.edu/faculty/farabee/biobk/BioBookENDOCR.html

https://endocrinology.wustl.edu/patient-care/endocrine-system/