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Chemical Co-ordination in Animals

Updated on July 9, 2015

We get amazed when we see or hear of wonders like wonders of the world, facts of the universe, the cosmos etc. But do you know that our body is a major wonder? Millions of cells organised uniquely, function dynamically in co-ordination in our body. The glandular system is one of the systems, which secrete harmones, which are the chemical messengers, which co-ordinate different organs of the body. Lets look into the details of this system.
Let's see the wonders of glands in our body today and the hormonal facts. Millions of cells organized uniquely function dynamically in co-ordination in our body. The glandular system is one of the systems, which secret hormones and co-ordinate different organs of the body. Let's see the hormones and their function.
Co-ordination in animals is brought by two methods
(1) by hormones (2) by nerve impulses. Hormones are produced by endocrine glands
which are ductless and so called as ductless glands.
Hormones: These are the chemical messengers which carry out a wide variety of
Physiological Processes.

Functions of Hormones: They regulate growth and metabolism and sexual development.
Process of release: They are released directly into the blood stream.
Quantity of Production: They are produced in very small quantity.
Then they are transported to organs and tissues throughout the entire body.
The deficiency or over secretion may cause some diseases.

Pituitary Gland:

Animals contain the following Endocrine Glands:

1. Pituitary Gland: It was named by Vesalius. It is trilobed and Pea shaped located under the brain in the middle of the head by a stalk. It is called the master gland as it controls the other ductless glands by stimulating them to produce their own harmones and influences growth and metabolism by producing nearly 8 hormones which affect growth, Kidney Function, Development of Gonads etc. Each lobe of this gland produces different hormones.

Growth Hormone
Melanocyte Stimulating

Thyroid Gland

2. Thyroid Gland:

It is an endodermal alveolar, bilobed gland attached to the tracheal
tube in the neck beneath the Larynx, It consists of a number of thyroid follicles.
Each one is lined by Secretary cells.
It secretes thyroxin. Iodine is required for the production of thyroxin. The daily requirement of iodine is 100 to 150 Mgm


3. Parathyroid Glands: Two pairs of Parathyroids are present in association with thyroids. These are highly vascularised producing the hormone parathormone, which is concerned with the regulation of Mg, P and Ca ions in the blood. It increases the absorption of Ca ions in intestine and Kidneys and bones.
4. Adrenal Glands: A pair of adrenal glands are seen in asociation with Kidneys. Each one is like a Pyramid with an outer cortex and an inner medulla which release different hormones. The cortex secretes cortisol (regulates the metabolism of carbohydrates, proteins and fats) and Aldosterone (increase the reabsorption of Water and Sodium in the body). Medulla secrets Adrenaline (helps the body to face anger, injury, pain etc.)
5. Pancreas: It is both exocrine and endocrine in function, associated with Alimentary canal. Its secretions are concerned with sugar metabolism, hence called sweet bread. The cells of endocrine Pancreas are called islets of langerhans. They secrete two hormones.
(1) Insulin (Promotes the conversion of glucose to glycogen) (2) Glucagon (acts on liver and promots the conversion of glycogen to glucose)
6. Gonads: Apart from producing gamates, gonads (testis and ovary) secrete hormones. Testis secretes Testosterone and Ovary produces oestrogen and progesterone, which help in the development of secondary sexual characters in males (beard, moustache, low pitch male voice) and females (hair growth and high pitch voice). They also help in the development of sexual organs.

The following table gives a brief idea about the effects caused due to deficiency and over secretion of hormones:

Deficiency Disease
Effect due to over secretion
1. Pituitary
Growth Hormone
2. Pituitary
Diabetes Insipidus (Excess Urination)
Frequency of urination is reduced
3. Thyroid
Cretinism (low growth, mental retardation)
Exophthalmia,goitres (enlargement of neck)
4. Thyroid
Lack of Iodine
Simple goitre
5. Parathyroid
Loss of Phosphates and Calcium from bones
Tetany, Osteomalacia due to brittle bones
6. Pancreas
Diabetes Mllitus (increase of glucose in the blood)
7. Adrenal Cortex
Addison's disease
cushing's syndrome
8. Gonads Testis Ovary
Testosterone Oestrogen
Enuchism non formation Sec.Sexual Characters)
Early matruity of the gonads.


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