Endocrine & Exocrine Glands
Gland is a cell or organ in man and other animals that synthesizes chemical substances and secretes them for the body to use or eliminate, either through a duct (exocrine gland) or directly into the bloodstream (endocrine gland)
Endocrine Glands secrete their products (hormones) directly into the bloodstream (ductless glands) or release hormones (paracrines) that affect only target cells nearby the release site.
1. Hypothalamus:
The hypothalamus is a small but important part of the brain. It plays an important role in the nervous system as well as in the endocrine system. Hormones produced by the hypothalamus are stored in the pituitary gland.
Vasopressin (ADH, antidiuretic hormone):Vasopressin helps prevent the loss of water from the body by reducing urine output and helping the kidneys reabsorb water in the body. Vasopressin also raises blood pressure by constricting (narrowing) blood vessels.
Endocrine Glands secrete their products (hormones) directly into the bloodstream (ductless glands) or release hormones (paracrines) that affect only target cells nearby the release site.
The hypothalamus is a small but important part of the brain. It plays an important role in the nervous system as well as in the endocrine system. Hormones produced by the hypothalamus are stored in the pituitary gland.
It is a neuroendocrine gland, synthesizes and secretes neuro hormones, control and regulate the secretion of pituitary hormones.
Functions:
- controls the release of 8 major hormones by the pituitary gland
- controls body temperature
- control of food and water intake, hunger and thirst
- control of sexual behavior and reproduction
- control of daily cycles in physiological state and behaviour also known as circadian rhythm
- mediation of emotional responses
Vasopressin (ADH, antidiuretic hormone):Vasopressin helps prevent the loss of water from the body by reducing urine output and helping the kidneys reabsorb water in the body. Vasopressin also raises blood pressure by constricting (narrowing) blood vessels.
Diabetes insipidus, which is caused by a lack of Vasopressin in the body.
Oxytocin: used clinically to stimulate contractions of the uterus during labour, to control bleeding following delivery, and to stimulate the secretion of breast milk (Milk injecting hormone).
2. Pituitary Gland:
The pituitary is a small, bean-shaped gland located below the brain in the skull. It is often called the "master gland" since it controls the secretion of hormones.
Important Hormones:
Growth hormone(Somatotrophin) which regulates growth, metabolism and body composition.
Prolactin stimulates milk production from the breasts after childbirth to enable nursing. It also affects sex hormone levels from ovaries in women and from testes in men.
Adrenocorticotropic hormone which stimulates the adrenal glands to secrete steroid hormones, principally cortisol
Luteinising hormone and follicle stimulating hormone, also known as gonadotrophins. They act on the ovaries or testes to stimulate sex hormone production and egg and sperm maturity.
Thyroid stimulating hormone(TSH) which stimulates the thyroid gland to secrete thyroid hormones.
Vasopressin & Oxytocin are produced by the hypothalamus and then stored in the posterior pituitary gland prior to being released into the bloodstream.
4. Pineal Gland:
The pineal gland is a pine cone shaped gland of the endocrine system. It produces the serotonin derivative Melatonin, a hormone that affects the modulation of wake/sleep patterns and seasonal functions. Pineal gland is also called Biological Clock.
4. Thyroid Gland:
The thyroid hormones, triiodothyronine (T3) and thyroxine (T4), are primarily responsible for regulation of metabolism. Iodine is necessary for the production of T3 and T4. A deficiency of iodine leads to decreased production of T3 and T4, enlarges the thyroid tissue and will cause the disease known as goitre.
The thyroid gland also produces calcitonin from cells called C-cells. Calcitonin is understood to play a role in regulating calcium levels in the body.
Abnormal increase in production of thyroid hormone is known as thyrotoxicosis or hyperthyroidism and reduced thyroid function is known as myxoedema or hypothyroidism.
Your doctor may order blood tests to determine levels of certain hormones, including:
4. Parathyroid Gland:
The sole purpose of the parathyroid glands is to control calcium within the blood.
The parathyroid gland secretes the hormone parathormone or parathyroid hormone (PTH).
The function of PTH is to increase the concentration of calcium in the blood, whereas calcitonin (a hormone produced by the parafollicular cells (C cells) of the thyroid gland) acts to decrease calcium concentration.
A parathyroid hormone (PTH) blood test is used to help identify hyperparathyroidism or to find the cause of abnormal calcium levels. PTH controls calcium and phosphorus levels in the blood.
5. Thymus Gland:
The thymus is located in the upper part of the chest. The thymus is an important part of immune systems. It grows larger until puberty and then begins to shrink.
The gland produces thymosins, which are hormones that stimulate the development of antibodies.
The thymus also produces T-lymphocytes which are white blood cells that fight infections and destroy abnormal cells.
5. Adrenal Gland:
The adrenal glands sit on top of the kidneys. The right adrenal gland is triangular shaped, while the left is semilunar shaped.
It has an inner medulla and outer cortex. The inner medulla produces epinephrine (adrenaline) and norepinephrine( while the outer cortex produces cortisol.
Medula: • Epinephrine has many functions in the body, regulating heart rate, blood vessel and air passage diameters, and metabolic shifts; epinephrine release is a crucial component of the fight-or-flight response of the sympathetic nervous system.
Epinephrine (adrenaline) is used to treat cardiac arrest and/or cardiac dysrhythmias.
• Noradrenaline increasing blood pressure and heart rate, and by the endings of sympathetic nerves, when it acts as a neurotransmitter both centrally and peripherally. This enables the body to perform well in stressful situations.
Cortex: • Cortisol. The adrenal glands increase their production of cortisol in response to stress. Cortisol raises blood sugar and blood pressure levels and moderates immune function
• Aldosterone This hormone helps to keep salt and water balanced in the body.
Estrogen and testosterone are produced in small but significant amounts by the adrenals as well as by the ovaries and testicles.
Exocrine Glands are glands that secrete their products (excluding hormones and other chemical messengers) into ducts (duct glands) which lead directly into the external environment.
The pituitary is a small, bean-shaped gland located below the brain in the skull. It is often called the "master gland" since it controls the secretion of hormones.
Important Hormones:
Growth hormone(Somatotrophin) which regulates growth, metabolism and body composition.
Prolactin stimulates milk production from the breasts after childbirth to enable nursing. It also affects sex hormone levels from ovaries in women and from testes in men.
Adrenocorticotropic hormone which stimulates the adrenal glands to secrete steroid hormones, principally cortisol
Luteinising hormone and follicle stimulating hormone, also known as gonadotrophins. They act on the ovaries or testes to stimulate sex hormone production and egg and sperm maturity.
Thyroid stimulating hormone(TSH) which stimulates the thyroid gland to secrete thyroid hormones.
Vasopressin & Oxytocin are produced by the hypothalamus and then stored in the posterior pituitary gland prior to being released into the bloodstream.
4. Pineal Gland:
The pineal gland is a pine cone shaped gland of the endocrine system. It produces the serotonin derivative Melatonin, a hormone that affects the modulation of wake/sleep patterns and seasonal functions. Pineal gland is also called Biological Clock.
4. Thyroid Gland:
The thyroid hormones, triiodothyronine (T3) and thyroxine (T4), are primarily responsible for regulation of metabolism. Iodine is necessary for the production of T3 and T4. A deficiency of iodine leads to decreased production of T3 and T4, enlarges the thyroid tissue and will cause the disease known as goitre.The thyroid gland also produces calcitonin from cells called C-cells. Calcitonin is understood to play a role in regulating calcium levels in the body.
Abnormal increase in production of thyroid hormone is known as thyrotoxicosis or hyperthyroidism and reduced thyroid function is known as myxoedema or hypothyroidism.
Your doctor may order blood tests to determine levels of certain hormones, including:
- Thyroid stimulating hormone (The release of thyroid hormones from the thyroid gland is controlled by TSH from the hypothalamus )
- Triodothyronine (T3)
- Thyroxine (T4)
4. Parathyroid Gland:
The sole purpose of the parathyroid glands is to control calcium within the blood.
The parathyroid gland secretes the hormone parathormone or parathyroid hormone (PTH).
The function of PTH is to increase the concentration of calcium in the blood, whereas calcitonin (a hormone produced by the parafollicular cells (C cells) of the thyroid gland) acts to decrease calcium concentration.
A parathyroid hormone (PTH) blood test is used to help identify hyperparathyroidism or to find the cause of abnormal calcium levels. PTH controls calcium and phosphorus levels in the blood.
5. Thymus Gland:
The thymus is located in the upper part of the chest. The thymus is an important part of immune systems. It grows larger until puberty and then begins to shrink.
The gland produces thymosins, which are hormones that stimulate the development of antibodies.
The thymus also produces T-lymphocytes which are white blood cells that fight infections and destroy abnormal cells.
5. Adrenal Gland:
The adrenal glands sit on top of the kidneys. The right adrenal gland is triangular shaped, while the left is semilunar shaped.
It has an inner medulla and outer cortex. The inner medulla produces epinephrine (adrenaline) and norepinephrine( while the outer cortex produces cortisol.
Medula: • Epinephrine has many functions in the body, regulating heart rate, blood vessel and air passage diameters, and metabolic shifts; epinephrine release is a crucial component of the fight-or-flight response of the sympathetic nervous system.
Epinephrine (adrenaline) is used to treat cardiac arrest and/or cardiac dysrhythmias.
• Noradrenaline increasing blood pressure and heart rate, and by the endings of sympathetic nerves, when it acts as a neurotransmitter both centrally and peripherally. This enables the body to perform well in stressful situations.
Cortex: • Cortisol. The adrenal glands increase their production of cortisol in response to stress. Cortisol raises blood sugar and blood pressure levels and moderates immune function
• Aldosterone This hormone helps to keep salt and water balanced in the body.
Estrogen and testosterone are produced in small but significant amounts by the adrenals as well as by the ovaries and testicles.
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