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Glands are of two types:
- Exocrine glands
- Endocrine glands
Exocrine glands are those which pour their secretions into a duct. For example, sweat glands, tear glands, etc.
Endocrine glands are those which are richly supplied with blood vessels and pour their secretions directly into the blood vessels. The secretions reach their target through blood. These glands are called the ductless glands as they do not have ducts. For example, thyroid, adrenal, etc.
The control and coordination of the different bodily functions is also done with the help of the endocrine system. This system exerts chemical control over the activities. These chemicals are secreted from organs called endocrine glands.
The secretions of the endocrine glands are called hormones. Hormones have the following characteristics:
- they may be proteinaceous or non-proteinaceous (amino acids or steroids)
- they are secreted as per need and not stored, only excreted
- their secretion may be regulated by nerves or by feedback effect
- they are transported by blood
- they mostly cause long-term effects like growth, change in behaviour, etc.
- they do not catalyse any reactions
- they function by stimulating or inhibiting the target organs.
Hormones can be defined as secretions that are poured into blood in order to reach a specifc target organ.
The human endocrine system consists of the following glands:
- Hypothalamus
- Pineal
- Thyroid
- Parathyroid
- Pituitary
- Thymus
- Adrenal
- Pancreas
- Ovary in female
- Testes in male
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