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A control system of the body By way of hormones (chemical messengers)

that are released directly into the blood Hormones control and/or assist processes

like: Reproduction Growth and development Mobilization of body defenses Homeostasis Metabolism

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Pituitary gland Hypothalamus Thyroid gland Parathyroid glands Adrenal glands Pancreas Pineal gland Thymus gland Gonads (ovaries and testes)

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Pineal glandHypothalamusPituitary gland

Thyroid gland

Parathyroid glands

Thymus

Adrenal glands

Pancreas

Ovary (female)

Testis (male)

Some are purely endocrine glands (ductless) Hormones are secreted directly into the blood

Anterior pituitary, thyroid, adrenals, parathyroids

Other glands are mixed glands, with both endocrine and exocrine functions Exocrine glands dump into ducts

pancreas, gonads

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Referred to as the “master endocrine gland” About the size of a pea

Hangs from the hypothalamus in the brain Has two functional lobes

Anterior pituitary—glandular tissue Produces hormones

Posterior pituitary—nervous tissue releases hormones after neural stimulation

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produces releasing and inhibiting hormones These influence pituitary action Such hormones are released into

circulation that connects the hypothalamus to the anterior pituitary

Synthesizes two hormones: oxytocin and antidiuretic hormone Stored in posterior pituitary

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Opticchiasma

Axonterminals

Anterior lobeof the pituitary

Venous drainage

Capillary bed

Posterior lobe of pituitary

Arterial blood supply

Hypothalamus

Hypothalamicneurosecretorycells

ADH Oxytocin

Kidney tubules Mammary glandsUterine muscles

Hormones produced by the hypothalamus are released into blood by nerve impulses

The posterior pituitary stores hormones synthesized by the hypothalamus

Oxytocin Stimulates uterine contractions Causes milk ejection in a breastfeeding

woman

Antidiuretic hormone (ADH) Inhibits urine production (diuresis)

promotes water reabsorption by the kidneys

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Six anterior pituitary hormones endocrine targets (tropic hormones):

1. Thyroid-stimulating hormone (thyrotropic hormone)

2. Adrenocorticotropic hormone3. Follicle-stimulating hormone4. Luteinizing hormone

nonendocrine targets:1. Growth hormone2. Prolactin

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Characteristics of all anterior pituitary hormones They are proteins Use a second-messenger systems Regulated by hormonal stimuli Regulated by feedback inhibition (most

often negative)

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Posterior pituitary

Adrenocorticotropichormone (ACTH)

Adrenal cortexThyrotropichormone (TH)

Thyroid

Follicle-stimulatinghormone (FSH)and luteinizinghormone (LH)

Testes or ovaries

Mammaryglands

Prolactin (PRL)Bones and muscles

Growth hormone (GH)

Anterior pituitary

Releasing hormonessecreted into portalcirculation

Hypothalamus

Growth hormone (GH) growth of skeletal muscles and long bones

Prolactin (PRL) Stimulates/maintains breast milk production

Adrenocorticotropic hormone (ACTH) Regulates endocrine activity of the adrenal cortex

Thyrotropic hormone (TH), A.K.A. thyroid-stimulating hormone (TSH) Influences growth and activity of the thyroid

gland

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Gonadotropic hormones Regulate hormonal activity of the gonads

Follicle-stimulating hormone (FSH) Stimulates follicle development in ovaries Stimulates sperm development in testes

Luteinizing hormone (LH) Triggers ovulation of an egg in females Stimulates testosterone production in males

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