ANATOMY AND PHISIOLOGY 2

THE ENDOCRINE SYSTEM

ENDOCRINOLOGY - science of the structure and function of the endocrine glands and diagnosis and treatment of the disorders of the endocrine system.

2 types of glands:

1. Exocrine Gland - secretes their products into ducts that carry the secretion into body cavities, into the lumen of an organ or to the surface of the body.
2. Endocrine Gland - secretes their products to the interstitial fluid surrounding the secretory cells; secretion then diffuses into capillaries and is carried away by the blood.

Endocrine Glands: Pituitary, Thyroid, Parathyroid, Adrenals, Pineal gland

Endocrine organs: Organs that secrete hormones but are not endocrine glands exclusively.

Hormone Activity

Hormones influence their target cells by binding to a specific receptor.

DOWN REGULATION - when a hormone is present in excess, the number of target cells may ¯ .

• Decreases the responsiveness of target cells to the hormone.

UP REGULATION - when a hormone or neurotransmitter is deficient, the number of receptors may ­ .

• Makes a target tissue more sensitive to a hormone.

Types of hormones according to ativity:

1. CIRCULATING HORMONES OR ENDOCRINES

- Hormones pass into blood and act on distant target cells

2. LOCAL HORMONES - acts locally without first entering the bloodstream.

1. PARACRINES - acts on neighboring cells.
2. AUTOCRINES - acts on the same cell that secreted them.

NEGATIVE FEEDBACK MECHANISMS - chief means of regulating blood levels of hormones.

• In this system, hormone secretion is triggered by some internal or external stimulus then the rising hormone levels inhibit further hormone release.

Disorders

HYPOSECRETION

HYPERSECRETION

THE MAJOR ENDOCRINE ORGANS:

1. PITUITARY GLAND

• Approximately the size of a grape; hangs by a stalk from the inferior surface of the hypothalamus.
• Two Functional Lobes a. Anterior Pituitary (glandular tissue)

b. Posterior Pituitary (Nervous Tissue)

Hormones of the Anterior Pituitary

Those that exert their effects on nonendocrine organs:

• Growth Hormone
• Prolactin

Tropic Hormones: Stimulate their target organs, which are also endocrine organs, to secrete their hormones, which in turn exert their effect on other organs or tissues.

• Thyrotropic Hormone
• Adrenocorticotropic Hormone
• 2 Gonadotropic Hormones

Growth Hormone: General Metabolic Hormone:

• Major effects are directed to the growth of skeletal muscles and long bones of the body.
• Stimulates most target cells to grow in size.
• Causes fats to be broken down and used for energy

PITUITARY DWARFISM:

GIGANTISM:

ACROMEGALY:

PROLACTIN: similar to growth hormone

ACTH: regulates the endocrine activity of the adrenal cortex.

TSH or Thyrotropic Hormone: Influences growth and activity of the thyroid gland.

GONADOTROPIC HORMONES: regulates the activity of the gonads.

Hormones of the Posterior Pituitary Gland:

• Not an endocrine gland in the strict sense because it only acts as a storage area for hormones.

OXYTOCIN: Stimulates powerful contractions of the uterine muscles.

ADH: sometimes called vasopressin

• causes constriction of arterioles

DIABETES INSIPIDUS -

THYROID GLAND

• Located at the base of the throat, inferior to the Adam's Apple
• Consist of 2 lobes joined by the isthmus
• Makes 2 hormones: a Thyroid Hormone b. Calcitonin

1. THYROID HORMONE - body's major metabolic hormone

• Controls the rate at which glucose is "burned" and converted to heat and chemical energy.
• Important in normal tissue growth and development especially reproductive and nervous systems.

GOITER -

HYPOTHYROIDISM:

1. Cretinism: occurs in children
2. Myxedema: occurs in adults

HYPERTHYROIDISM:

GRAVE'S DISEASE:

CALCITONIN: Hypocalcemic hormone

• Decreases the blood calcium levels by depositing calcium in the bone.
• Antagonist to parathormone.

PARATHYROID HORMONES:

• Secretes parathormone (PTH)
• Decreased blood calcium levels causes the release of PTH, which stimulates bone destruction by the osteoclasts to break down bone matrix and release the calcium in the blood to increase blood calcium levels.
• Hypercalcemic hormone

ADRENAL GLANDS:

Adrenal Cortex: Produces corticosteroids

a.1. Mineralocorticoids: Aldosterone

a.2. Glucocorticoids: Cortisone and Cortisol

a.3. Sex Hormones

** HYPOSECRETION -

ADDISON'S DISEASE

** HYPERSECRETION - Condition depends on the cortical layer involved.

Outer Cortical Layer:

HYPERALDOSTERONISM - excess sodium and water retention.

Middle Cortical Layer:

CUSHING'S SYNDROME:

Innermost Layer: MUSCULINIZING SYNDROME

_____________________

Adrenal Medulla: Secretes catecholamines ( E and Nor - E)

PANCREAS

PANCREATIC ISLETS: aka: Islets of Langerhans

• Produces primarily insulin and glucagon

DIABETES MELLITUS:

PINEAL GLAND:

• small cone shaped gland found on the roof of the third ventricle.
• Secretes MELATONIN

THYMUS GLAND:

• Secretes THYMOSIN for the maturation of T Lymphocytes.

Page Updated: February 18, 2007

To my students: This is only a general outline. There is much that will be discussed and presented in lecture that is not included in this outline. All material discussed in lecture is test-material whether or not it is included in this outline. Mr. D.K. Mangusan Jr., PTRP

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