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Endocrine system

Endocrine system. The Endocrine system. The endocrine system is part of the regulatory system of the body and works in conjunction with the nervous system. The nervous system produces an immediate response while the endocrine system produces a slower but longer lasting effect.

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Endocrine system

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  1. Endocrine system

  2. The Endocrine system • The endocrine system is part of the regulatory system of the body and works in conjunction with the nervous system. The nervous system produces an immediate response while the endocrine system produces a slower but longer lasting effect. • Endocrine glands secrete hormones, which are carried by the blood to specific target organs. They are produced by ‘ductless glands’.

  3. Hormones are chemical messengers. They regulate the activity of the target organ, which responds to that particular hormone. • The endocrine glands are distributed throughout the body and often secrete more than one hormone.

  4. The glands are: • Pituitary (anterior and posterior) • Thyroid • Parathyroid • Pancreas • Adrenals • Ovaries • Testes

  5. Label the diagram

  6. Secretion of a hormone occurs in response to a specific stimulus which could be: • Nerve impulses eg adrenaline is released from the adrenal gland following stimulation by the sympathetic nervous system • A stimulating or releasing hormone eg TSH (Thyroid Stimulation Hormone) from the anterior pituitary activates the thyroid gland

  7. 3. Levels of certain chemicals in the blood eg increased blood glucose levels stimulate the pancreas to produce insulin 4. Feedback loops- they prevent over secretion/ reduce secretion once the desired effect has been achieved eg oestrogen from the ovarian follicles prevents further secretion of FSH from the anterior pituitary so preventing further development of the follicle

  8. Not all hormones are secreted by endocrine glands, some are produced from tissue in another organ eg gastrin which is produced by the wall of the stomach.

  9. Pituitary gland • This is a small gland which is found ventral to the hypothalamus in the forebrain. It is divided into 2 lobes (anterior and posterior), each acting as a separate gland. It’s often called the ‘master gland’ as its hormones control the secretions of many other of the endocrine glands

  10. Anterior pituitary

  11. Posterior pituitary

  12. Thyroid glands • These are found in the midline on the ventral aspect of the first few rings of the trachea. They are controlled by TSH from the anterior pituitary. • Under secretion of thyroid hormone is called hypothyroidism and is commonly seen in dogs. Over secretion of thyroid hormone is called hyperthyroidism and is commonly seen in cats.

  13. Thyroid gland

  14. Parathyroid glands • These lie on either side of the thyroid gland. Secretion of parathormone depends on levels of calcium in the blood.

  15. Parathyroid glands

  16. Pancreas • This organ lies next to the duodenum in the abdominal cavity. It produces both endocrine and exocrine secretions so is called a mixed gland. The exocrine secretions are digestive juices while the endocrine are secreted by the Islets of Langerhans

  17. Pancreas

  18. Adrenal glands • There are a pair of adrenal glands, one lying close to the cranial portion of each kidney. Each gland has an outer cortex and an inner medulla, these act as 2 separate glands.

  19. Adrenal glands

  20. Ovaries • Females have 2 ovaries, which lie on each side of the dorsal abdominal cavity caudal to the kidneys. The ovaries secret hormones when the animal reaches sexual maturity.

  21. Testes • Males have 2 testicles which lie outside the abdominal cavity in the scrotum. The testes secret hormones when the animal reaches sexual maturity.

  22. Ovaries and Testes

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