Pineal Gland

*Endocrine GlandsHypothalamusPituitaryAnterior lobePosterior lobeThyroid glandParathyroid glandsAdrenal GlandsCortexMedullaIslets of LangerhansGonadsOvariesTestesPineal glandThymusothers

*othersStomach, small intestineHeart ANPKidneys erythropoietin Adipose tissue leptinSkin cholecalciferol (vit. D precursor) Placenta progesterone

WHAT I EXPECT YOU TO KNOW ABOUT EVERY ENDOCRINE STRUCTURE

What is it?

What is its location (where is it)?

What is its embryological derivation?

What is its innervation?

What is its arterial supply?

What is its venous drainage? (This is particularly important, as hormones must be placed into the circulatory system.)

What is its function? (In other words, what do its hormones do?)

Endocrine-Glands.ppt

The Pineal GlandIs a small pine cone-shaped endocrine gland (pea-size) located near the center of the brain and attached to the posterior end of the roof of the third ventricle in the brain. It is stimulated by nerves from the eyes.


Melatonin: Hormone produced by the Pineal Gland Amine Hormone; derived from tryptophan

Regulates human sleep-wake cycles

Stimulated by darkness, inhibited by light

Suspected to affect reproductive functions

Linked to onset of puberty


SAD (Season Affective Disorder)Caused when too much melatonin is produced, especially during the long nights of winter, causing profound depression, oversleeping, weight gain, tiredness, or sadness. Treatment consists of exposure to bright lights for several hours each day to inhibit melatonin production.


Melatonin supplements can be taken to help combat:

Jet Lag Insomnia of the elderly Various Sleep Disordersand moreSteady exposure to light can disrupt the natural production of melatonin and disrupt the bodys biological clock and cause sleeping problems.


Where is melatonin produced? -the pineal gland

What stimulates the Pineal Gland? darkness/night

What type of hormone is Melatonin? amine hormone

What does Melatonin regulate? -the sleep-wake cycle/ biological clock

What disorder is caused by too much melatonin? -seasonal affective disorder

Quiz


Pineal glandSuspended in third ventricle from diencephalonMelatonin? Inhibits early puberty? Day/night cyclesTiming of sleep, body temperature, appetite

Anatomy of the Pineal GlandThe pineal gland is a small organ shaped like a ______ (hence its name). It is located on the midline, attached to the posterior end of the roof of the third ventricle in the brain. The pineal varies in size among species; in humans it is roughly 1 cm in length, whereas in dogs it is only 1 mm long. To observe the pineal, reflect the cerebral hemispheres laterally and look for a small grayish bump in front of the cerebellum. The images below shows the pineal gland of a horse in relation to the brain.


PINEAL GLAND

Location and Development: outgrowth of the roof of the diencephalon. Found near the posterior margin of the corpus callosum, slightly cranial and superior to cerebellum.

Innervation: (Already) Part of brain.

Arterial Supply: circulosus artriosus cerebri

Venous Drainage: cavernous venous sinus

Function: MELATONIN amino acid derivative thought to have connection with regulating sleep cycle.


Pineal Gland: Physical Characteristics

Small, pine-cone-shaped gland (hence its name)Reddish-gray in colorIt is larger in children, but shrinks with the onset of pubertyIn adults, it weighs (about 180mg). and is about 0.8 cm longSituated between 2 cerebral hemispheres ; Attached to the posterior wall of the 3rd cerebral ventricle

Suspended in a cavity of cerebrospinal fluid , it Lacks a blood-brain barrier, therefore, receives blood, oxygen, & nutrients through a rich vascular network.

Contains a large supply of adrenergic nerve fibers

Composed of pinealocytes (endocrine cells with extensions that interact with the extensions of nearby cells) and supporting cells that resemble astrocytes.

Pineal Gland:

CharacteristicsIt is developed from epithelial tissueThe soft tissue of the adult pineal gland contains more fluoride than any other soft tissue in the body - a level of fluoride capable of inhibiting enzymes.The pineal gland also contains hard tissue(hyroxyapatite crystals), which accumulates more fluoride than any other hard tissue in the body (ex. teeth and bone)Studies show that fluoride reduces the levels of melatonin in the blood

Functions of the Pineal GlandThe major function of the pineal gland is producing melatonin, a hormone that has several important effects on the body.Melatonin regulates daily body rhythms, most importantly circadian rhythm, the wake/sleep cycle. We feel sleepy at night because darkness stimulates the pineal gland to produce melatonin and we feel alert during the day because light inhibits the pineal gland from producing melatonin. Since the activity of the pineal gland depends on the amount of available energy, it is a photosensitive organ.

The abundant levels of melatonin in children inhibit the secretion of gonadotropins, hormones that regulate normal growth, sexual development, and reproductive functions, before puberty. Therefore, they prevent the onset of puberty before the appropriate age.

Melatonin levels are low in children with autism, and as a result, about 70% of them suffer from sleeping problems.

Studies show that low doses of melatonin can help children with autism sleep better without giving them any noticeable side effects. Studies show that melatonin levels may be related to the risk of certain types of cancer.

Melatonin levels tend to be lower in women with breast cancer than in those without the disease. Laboratory experiments show that low levels of melatonin stimulate the growth of certain types of breast cancer cells. However, adding melatonin to these cells slows their growth.

New research also suggests that melatonin may strengthen the effects of some chemotherapy drugs used to treat breast cancer. In one study, several women with breast cancer were given melatonin 7 days before beginning chemotherapy. The melatonin prevented the lowering of platelets in the blood, a common complication that can cause bleeding.

In another study, several women with breast cancer were taking tamoxifen, but were not improving. However, once melatonin was added, the tumors in over 28% of the women modestly shrank.

Studies also show that melatonin levels are lower in men with prostate cancer than in those without the disease. In test tube studies, melatonin blocks the growth of prostate cancer cells.

In one small-scale study, melatonin, along with improved regular medical treatment, improved survival rates in 9 out of 14 men with metastatic prostate cancer. Melatonin has been found to be able to slow the aging process.It is a powerful antioxidant that can easily pass through cell membranes and the blood-brain barrier.

It is a highly effective and direct scavenger of the very reactive and toxic free radicals.Unlike other antioxidants, melatonin does not undergo redox cycling. Once it is oxidized it can never be reduced to its former state. Therefore, it never promotes free radical formation.

By terminally disarming the free radicals, melatonin protects the cells DNA from oxidation damage.

It is a powerful antioxidant that can easily pass through cell membranes and the blood-brain barrier.

It is a highly effective and direct scavenger of the very reactive and toxic free radicals.Unlike other antioxidants, melatonin does not undergo redox cycling. Once it is oxidized it can never be reduced to its former state. Therefore, it never promotes free radical formation.

By terminally disarming the free radicals, melatonin protects the cells DNA from oxidation damage.

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Pineal Gland: Interactions with Other Organs

Secretion of melatonin by the pineal gland inhibits the secretion of the Gonadotropin-releasing hormone (GnRH) by the hypothalaus.

Secretion of melatonin also indirectly inhibits the pituitary from secreting gonadotropins, Leutenizing Hormone (LH) and Follicle Stimulating Hormone (FSH), because the secretion of GnRH is necessary for this to occur.

Because its secretion reduces the levels of LH in the blood, melatonin may inhibit ovulation in women and can decrease sperm mobility and sex drive in men.

The pineal gland also interacts with the hypothalamus in regulating the circadian rhythm.

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Pineal Gland

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