Chapter Nine The Endocrine System
The Endocrine System consists of endocrine glands that secrete specific chemicals called hormones into the
blood/tissue fluid.
The Endocrine System is one of the body’s communication systems and uses these hormones as messengers
to help to regulate cellular activity by providing a constant internal environment, i.e. homeostasis.
A hormone is a chemical substance that is generated in one organ and carried by the blood to a target organ
where it excites activity.
The Endocrine System works very closely with the nervous system to help control the body.
Endocrine glands are ductless and secrete their hormones directly into the bloodstream.
The Endocrine Glands in the body are: (Hypothalamus); Pituitary; Pineal; Thyroid; Parathyroids; Adrenals;
Pancreas - Islets of Langerhans; Thymus; Ovaries; Testes.
The Hypothalamus and Pituitary Gland act as a unit to regulate activity of each other:
Pituitary has 2 lobes - anterior lobe and posterior lobe
The Pituitary is attached to the Hypothalamus of the brain by a stalk
This stalk brings blood from the hypothalamus rich in 02, nutrients, releasing and inhibiting hormones
(RH; IH) to the anterior lobe to influence its secretions: ‘Pituitary Portal System’
The stalk brings nerves from the hypothalamus to the posterior lobe
The Pituitary is often referred to as the ‘Master Gland’ because it produces several hormones or
releasing factors that influence the secretion of hormones of other endocrine glands.
www.goldeneggholistic.com Anatomy, Physiology and Pathology notes 65
, Anterior Pituitary Function Target
Growth Hormone Stimulate growth of skeletal muscle, organs + connective Many tissues
(GH) tissue e.g. bone
Thyroid Stimulating Stimulates growth & activity of the thyroid gland Thyroid
Hormone (TSH)
Adrenocorticotrop Stimulates & controls the growth and hormonal output of Adrenal Cortex
hin (ACTH) the adrenal cortex
Prolactin Stimulates lactation Breast
Release is stimulated by suckling
Follicle Stimulating FSH: stimulates the development and ripening of ovarian / Ovaries/testes
Hormone or graafian follicle that secretes oestrogen (female)
Stimulates testes to produce sperm (male)
Luteinising LH: stimulates final maturation of ovarian follicle and
Hormone ovulation
Promotes formation of Corpus luteum that secretes
Progesterone (female)
Stimulates testes to produce testosterone (male)
Melanocyte Stimulates the production of melanin in the basal cell layer Skin
Stimulating of the epidermis
Hormone (MSH)
Posterior
Pituitary
Oxytocin Promotes uterine contraction and expression of milk Uterus & Breast
Vasopressin/ Contraction of smooth muscle (blood vessels) = increase BP Blood vessels
antidiuretic Increase permeability of kidneys to water = more water
Hormone (ADH) absorbed Kidney tubules
‘Pituitary Portal System’ The anterior secretions of the pituitary are dependent on stimulation from the
hypothalamus and are involved in ‘Negative feedback mechanism’.
‘Negative Feedback Mechanism’: If a hormone blood level is low - stimulation of the hypothalamus to
produce its stimulating hormone - stimulate pituitary to release hormone - increase blood hormone
level - signal hypothalamus to release its inhibiting hormone - goes to pituitary - amount of hormone
released is decreased.
The Pineal Gland
Pea-sized mass of nerve tissue deep in the brain
It secretes the hormone melatonin (made from serotonin
More melatonin is released in the darkness and can promote sleepiness
It functions to co-ordinate circadian rhythms / day & night rhythms / biological clock
Overproduction of melatonin during winter months can cause Seasonal Affected Disorder (SAD) as
daylight hours are shortened. It is also thought to be associated with Jet Lag
www.goldeneggholistic.com Anatomy, Physiology and Pathology notes 66
The Endocrine System consists of endocrine glands that secrete specific chemicals called hormones into the
blood/tissue fluid.
The Endocrine System is one of the body’s communication systems and uses these hormones as messengers
to help to regulate cellular activity by providing a constant internal environment, i.e. homeostasis.
A hormone is a chemical substance that is generated in one organ and carried by the blood to a target organ
where it excites activity.
The Endocrine System works very closely with the nervous system to help control the body.
Endocrine glands are ductless and secrete their hormones directly into the bloodstream.
The Endocrine Glands in the body are: (Hypothalamus); Pituitary; Pineal; Thyroid; Parathyroids; Adrenals;
Pancreas - Islets of Langerhans; Thymus; Ovaries; Testes.
The Hypothalamus and Pituitary Gland act as a unit to regulate activity of each other:
Pituitary has 2 lobes - anterior lobe and posterior lobe
The Pituitary is attached to the Hypothalamus of the brain by a stalk
This stalk brings blood from the hypothalamus rich in 02, nutrients, releasing and inhibiting hormones
(RH; IH) to the anterior lobe to influence its secretions: ‘Pituitary Portal System’
The stalk brings nerves from the hypothalamus to the posterior lobe
The Pituitary is often referred to as the ‘Master Gland’ because it produces several hormones or
releasing factors that influence the secretion of hormones of other endocrine glands.
www.goldeneggholistic.com Anatomy, Physiology and Pathology notes 65
, Anterior Pituitary Function Target
Growth Hormone Stimulate growth of skeletal muscle, organs + connective Many tissues
(GH) tissue e.g. bone
Thyroid Stimulating Stimulates growth & activity of the thyroid gland Thyroid
Hormone (TSH)
Adrenocorticotrop Stimulates & controls the growth and hormonal output of Adrenal Cortex
hin (ACTH) the adrenal cortex
Prolactin Stimulates lactation Breast
Release is stimulated by suckling
Follicle Stimulating FSH: stimulates the development and ripening of ovarian / Ovaries/testes
Hormone or graafian follicle that secretes oestrogen (female)
Stimulates testes to produce sperm (male)
Luteinising LH: stimulates final maturation of ovarian follicle and
Hormone ovulation
Promotes formation of Corpus luteum that secretes
Progesterone (female)
Stimulates testes to produce testosterone (male)
Melanocyte Stimulates the production of melanin in the basal cell layer Skin
Stimulating of the epidermis
Hormone (MSH)
Posterior
Pituitary
Oxytocin Promotes uterine contraction and expression of milk Uterus & Breast
Vasopressin/ Contraction of smooth muscle (blood vessels) = increase BP Blood vessels
antidiuretic Increase permeability of kidneys to water = more water
Hormone (ADH) absorbed Kidney tubules
‘Pituitary Portal System’ The anterior secretions of the pituitary are dependent on stimulation from the
hypothalamus and are involved in ‘Negative feedback mechanism’.
‘Negative Feedback Mechanism’: If a hormone blood level is low - stimulation of the hypothalamus to
produce its stimulating hormone - stimulate pituitary to release hormone - increase blood hormone
level - signal hypothalamus to release its inhibiting hormone - goes to pituitary - amount of hormone
released is decreased.
The Pineal Gland
Pea-sized mass of nerve tissue deep in the brain
It secretes the hormone melatonin (made from serotonin
More melatonin is released in the darkness and can promote sleepiness
It functions to co-ordinate circadian rhythms / day & night rhythms / biological clock
Overproduction of melatonin during winter months can cause Seasonal Affected Disorder (SAD) as
daylight hours are shortened. It is also thought to be associated with Jet Lag
www.goldeneggholistic.com Anatomy, Physiology and Pathology notes 66
