Biology XII Notes for Biology Notes

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Endocrine Glands and Exocrine Glands

The study of endocrine glands is called endocrinology. Thomas Addison is known as ‘The Father of Endocrinology’.

Endocrine Glands:

Endocrine glands are the ductless glands secreting hormones directly into the bloodstream and control long-term activity of target organ. They control, co-ordinate and influence various physiological activity of the body. The hormones are regulatory, metabolic and morphological in action. E.g. Pituitary gland, Thyroid gland, Parathyroid gland etc.

Chemical Composition of Hormones:

Hormones are of following chemical compositions:

a)Glycoprotein – Follical stimulating Hormone (FSH), Leutenizing Hormone (LH)

b)Proteinous – Insulin, Glucagon

c)Biogenic Amines (Containing NH2) – Thyroxin, Adrenaline

d)Steroids (containing fats) – testosterone, progesterone

Exocrine Glands:

Exocrine glands are the glands with ducts secreting enzymes. They secrete enzymes into the ducts and are present near to the site of action. The enzymes are exclusively proteinous. Their secretions may be released in or out (e.g., sweat) of the body. E.g. sweat gland, mammary gland, salivary gland etc.

Note: Glands like pancreas, testis and ovary are known as heterocrine glands because they act as exocrine as well as endocrine glands i.e. release hormones as well as enzymes, while the rest single- functioning glands are called holocrine glands.

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