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Upper Endocrine System

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Submitted By dcouncilor10
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THE GLANDS
A gland is a group of cells or an organ that produces a secretion for use elsewhere in the body, or in a body cavity.
TWO KINDS OF GLANDS
EXOCRINE GLANDS
The secretion of the exocrine glands pass through a duct to the site where they take effect.
Examples
Salivary glands - Saliva
Sweat glands - Perspiration Mammary glands - Milk
ENDOCRINE GLANDS
The gland known as ductless or endocrine glands secrete their product directly into the bloodstream. The term ductless indicates that no duct cones out from the glands. Their secretion are called hormones, also known as chemical messengers. They regulate and integrate body functions.
ENDOCRINE SYSTEM
The endocrine system refers to the collection of glands of an organism that secrete hormones directly into the circulatory system to be carried towards distant target organs.
It is a system that controls body functions such as sleep, sexual behavior, digestion, metabolism, and physical development.
The endocrine system is an information signal system like the nervous system, yet its effects and mechanism are classifiably different.
The endocrine system's effects are slow to initiate, and prolonged in their response, lasting from a few hours up to weeks. In vertebrates, the hypothalamus is the neural control center for all endocrine systems.
The communication begins at the base of the forebrain with the hypothalamus.
The hypothalamus sends messages to the pituitary gland, which then secretes hormones into the bloodstream, affecting glands throughout the body.
HYPOTHALAMUS
The hypothalamus synthesizes and secretes certain neurohormones, often called releasing hormones or hypothalamic hormones, and these in turn stimulate or inhibit the secretion of pituitary hormones.
The hypothalamus controls body temperature, hunger, important aspects of parenting and attachment behaviors, thirst, fatigue, sleep, and circadian rhythms.
PITUITARY GLAND
The pituitary gland or hypophysis is an endocrine gland about the size of a pea and weighing 0.5 grams (0.018 oz) in humans and is also known as the master of the ductless glands. The pituitary gland secretes nine hormones that regulate homeostasis and the secretion of other hormones.
HORMONES SECRETED
ANTERIOR PITUITARY LOBE
Growth hormone * Stimulates growth and cell reproduction * Stimulates Insulin-like growth factor release from liver
Thyroid-stimulating hormone * Stimulates thyroxine (T4) and triiodothyronine (T3) synthesis and release from thyroid gland * Stimulates iodine absorption by thyroid gland
Adenocorticotropic hormone * Stimulates corticosteroid (glucocorticoid and mineralcorticoid) and androgen synthesis and release from adrenocortical cells
Beta-endorphin
* Inhibits perception of pain
Follicle-stimulating Hormone * In females: Stimulates maturation of ovarian follicles in ovary * In males: Stimulates maturation of seminiferous tubules * In males: Stimulates spermatogenesis * In males: Stimulates production of androgen-binding protein from Sertoli cells of the testes
Luteinizing Hormone * In females: Stimulates ovulation * In females: Stimulates formation of corpus luteum * In males: Stimulates testosterone synthesis from Leydig cells (interstitial cells)
Prolactin
* Stimulates milk synthesis and release from mammary glands * Mediates sexual gratification
Melanocyte-stimulating hormone * Stimulates melanin synthesis and release from skin/hair melanocytes
POSTERIOR PITUITARY LOBE
Oxytocin
* In females: uterine contraction during birthing, lactation (letdown reflex) when nursing
Antidiuretic Hormone * Increases water permeability in the distal convoluted tubule and collecting duct of nephrons, thus promoting water reabsorption and increasing blood volume
Thyroid GLAND
A soft, brownish-red H-shaped organ.
It is located beneath the larynx.
The thyroid gland controls how quickly the body uses energy, makes proteins, and controls the body's sensitivity to other hormones.
HORMONES SECRETED
Triiodothyronine
* More potent form of thyroid hormone * Stimulates body oxygen and energy consumption, thereby increasing the basal metabolic rate * Stimulates RNA polymerase I and II, thereby promoting protein synthesis
Thyroxine
* Less active form of thyroid hormone * (Acts as a prohormone to triiodothyronine) * Stimulates body oxygen and energy consumption, thereby increasing the basal metabolic rate * Stimulates RNA polymerase I and II, thereby promoting protein synthesis
Calcitonin
* Stimulates osteoblasts and thus bone construction * Inhibits Ca2+ release from bone, thereby reducing blood Ca2+
PARATHYROID GLAND
These are four small glandular bodies, each about the size of a small pea, attached to the back of the thyroid gland.

These glands regulate the calcium and phosphate balance in the blood plasma.
This is essential to a wide variety of body functions, particularly nerve and muscle excitability.
HORMONES SECRETED
Parathyroid Hormone * It takes calcium and phosphate ions from bones so that they will be available in the blood, the muscles, and nerves
THYMUS GLAND
The thymus gland is located at the upper part of the chest, below the neck. It consists of two lobes.
The thymus is quite prominent in early life, but degenerates when puberty sets in. It is replaced mostly by fibrous or fatty tissue.

The thymus gland perform a vital function in the early months of life. It manufactures white blood cells that make it possible for the body to develop immunity against infection.
HORMONES SECRETED
Promine
* Promotes growth
Retine
* Retards growth
PINEAL GLAND
A small endocrine gland in the vertebrate brain. It produces a hormone which affects the modulation of sleep patterns in both seasonal and circadian rhythms. The gland has been compared to the photoreceptive, so-called third parietal eye present in the epithalamus of some animal species, which is also called the pineal eye.
René Descartes believed the pineal gland to be the "principal seat of the soul" and viewed it as the third eye.
HORMONES SECRETED
Melatonin
* A serotonin derived hormone, which affects the modulation of sleep patterns in both seasonal and circadian rhythms.

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