AQA · GCSE · Biology
Course version: 8461 · Version from Sept 2018
The endocrine system is composed of glands which secrete chemicals called…
Full specification wording
Human endocrine system: The endocrine system is composed of glands which secrete chemicals called hormones directly into the bloodstream.
The endocrine system is a set of ductless glands that release hormones straight into the blood.
Checked against the AQA 8461 specification (opens in a new tab) on .
- Point 2 of 7
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
The endocrine system is a set of ductless glands that release hormones straight into the blood. Because hormones enter the bloodstream directly, they can be carried to every part of the body, but only target cells with matching receptors respond. Named glands include the pituitary, thyroid, adrenal, pancreas, ovaries and testes. For example, the pancreas secretes insulin into the blood, and the thyroid secretes thyroxine. This differs from exocrine glands, which release substances through ducts, such as salivary glands. When describing the system, state that glands are the source, hormones are the chemical messengers, and the bloodstream is the transport route.
What earns the marks
- Identify the endocrine system as a collection of glands, including named examples such as the pituitary, thyroid, adrenal, pancreas, ovaries and testes.
- State that endocrine glands are ductless and secrete hormones directly into the bloodstream.
- Define hormones as chemical messengers carried by the blood.
- Contrast endocrine glands with exocrine glands, which secrete through ducts.
- Explain that because hormones enter the blood, they can reach many organs, but only target cells respond.
Common mistakes and how to put them right
Saying hormones are released into ducts.
Put it right: Endocrine glands are ductless and secrete hormones directly into the blood.
Confusing hormones with enzymes.
Put it right: Hormones are chemical messengers carried in the blood, while enzymes are biological catalysts.
Naming only one gland as the endocrine system.
Put it right: The system includes several glands, such as the pituitary, thyroid, adrenal, pancreas, ovaries and testes.
Exam tips
- Use the phrase 'ductless glands secrete hormones directly into the bloodstream' when defining the endocrine system.
- Name at least two glands and their hormones to show breadth of knowledge.
- Distinguish endocrine from exocrine secretion if the question asks for a comparison.
Try the lesson
The start of the Human endocrine system: The endocrine system is composed of glands which secrete chemicals called hormones directly into the bloodstream. lesson, made from checked teaching notes for this specification point.
Have a go first
Where do endocrine glands secrete hormones?
Listen
The endocrine system is a set of ductless glands that release hormones straight into the blood. Because hormones enter the bloodstream directly, they can be carried to every part of the body, but only target cells with matching receptors respond. Named glands include the pituitary, thyroid, adrenal, pancreas, ovaries and testes. For example, the pancreas secretes insulin into the blood, and the thyroid secretes thyroxine. This differs from exocrine glands, which release substances through ducts, such as salivary glands. When describing the system, state that glands are the source, hormones are the chemical messengers, and the bloodstream is the transport route. A strong answer earns marks for these points. Identify the endocrine system as a collection of glands, including named examples such as the pituitary, thyroid, adrenal, pancreas, ovaries and testes. State that endocrine glands are ductless and secrete hormones directly into the bloodstream. Define hormones as chemical messengers carried by the blood. Contrast endocrine glands with exocrine glands, which secrete through ducts. A common slip: Saying hormones are released into ducts. Instead, endocrine glands are ductless and secrete hormones directly into the blood. Exam tip: Use the phrase 'ductless glands secrete hormones directly into the bloodstream' when defining the endocrine system.
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Key words
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Glands as endocrine organs
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Hormones as chemical messengers
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Direct secretion into the bloodstream
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Ductless versus ducted secretion
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See every definition
- Glands as endocrine organs
- The endocrine system is composed of glands which secrete chemicals called hormones directly into the bloodstream.
- Hormones as chemical messengers
- Hormones are chemical messengers carried by the blood.
- Direct secretion into the bloodstream
- Endocrine glands secrete hormones directly into the bloodstream, so they can be carried to every part of the body.
- Ductless versus ducted secretion
- Endocrine glands are ductless, whereas exocrine glands release substances through ducts, such as salivary glands.
Label the diagram
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1Box 1
2Box 2
3Box 3
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