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The endocrine glands, or ductless glands, discharge their secretions (hormones) directly into the blood; they include the adrenal, pituitary, thyroid, and parathyroid glands, the islands of Langerhans in the pancreas, the gonads, the thymus, and the pineal body. The exocrine glands discharge through ducts opening on an external or internal surface of the body; they include the salivary, sebaceous, and sweat glands, the liver, the gastric glands, the pancreas, the intestinal, mammary, and lacrimal glands, and the prostate. The lymph nodes are sometimes called lymph glands but are not glands in the usual sense.
Synonym(s): glandula (1) .
gland(gland) [L. glans, acorn]
acinar glandAlveolar gland.
acinous glandAlveolar gland.
Each adrenal gland is a two-part organ composed of an outer cortex and an inner medulla. The cortex arises in the embryo from a region of the mesoderm that also gives rise to the gonads. The medulla arises from ectoderm, which also gives rise to the sympathetic nervous system.
The entire gland is enclosed in a tough connective tissue capsule from which trabeculae extend into the cortex. The cortex consists of cells arranged into three zones: the outer zona glomerulosa, the middle zona fasciculata, and the inner zona reticularis. The cells are arranged in cords. The medulla consists of chromaffin cells arranged in groups or in anastomosing cords. The two adrenal glands are retroperitoneal, each embedded in perirenal fat above its respective kidney. In an adult, the average weight of an adrenal gland is 5 g (range: 4 to 14 g).
The adrenal medulla synthesizes and stores three catecholamines: dopamine, norepinephrine, and epinephrine. The chief effects of dopamine are the dilation of systemic arteries, increased cardiac output, and increased flow of blood to the kidneys. The primary action of norepinephrine is constriction of the arterioles and venules, resulting in increased resistance to blood flow, elevated blood pressure, and slowing of the heart. Epinephrine constricts vessels in the skin and viscera, dilates vessels in skeletal muscle, increases heart rate, dilates the bronchi by relaxing bronchial smooth muscle, increases the conversion of glycogen to glucose in the liver to increase the blood glucose level, and diminishes activity of the gastrointestinal system. The three catecholamines are also produced in other parts of the body.
The adrenal medulla is controlled by the sympathetic nervous system and functions in conjunction with it. It is intimately related to adjustments of the body in response to stress and emotional changes. Anticipatory states tend to bring about the release of norepinephrine. More intense emotional reactions, esp. those in response to extreme stress, tend to increase the secretion of both norepinephrine and epinephrine; epinephrine is important in mobilizing the physiological changes that occur in the “fight or flight” response to emergency situations.
The cortex synthesizes three groups of steroid hormones from cholesterol. These are 1) glucocorticoids (cortisol, corticosterone), which regulate the metabolism of organic nutrients and have an anti-inflammatory effect; 2) mineralocorticoids (aldosterone, dehydroepiandrosterone), which affect metabolism of the electrolytes sodium and potassium; and 3) androgens and estrogens (estradiol), which contribute to body changes at puberty. See: aldosterone; cortisol; steroid
Hypersecretion of adrenal cortical hormones results in Cushing syndrome. Hypersecretion of aldosterone results in a surgically correctable form of hypertension (aldosteronism). Adrenocortical insufficiency may be acute or chronic; acute insufficiency of adrenal hormones produces circulatory shock, while chronic insufficiency results in Addison disease. See: Addison disease; aldosteronism; Cushing syndrome; pheochromocytoma
apocrine sweat gland
Bartholin glandSee: Bartholin, Caspar (the younger)
Blandin glandsSee: Blandin glands
Bowman glandsSee: Bowman, Sir William
Bruch glandSee: Bruch, Karl
Brunner glandsSee: Brunner glands
bulbourethral glandCowper gland.
circumanal glandAnal gland.
coccygeal glandSee: Luschka, Hubert von
compound tubular gland
Cowper glandSee: Cowper gland
duodenal glandSee: Brunner glands
Ebner glandsSee: Ebner glands
eccrine sweat gland
The hormones produced by endocrine cells regulate the body's salt, water, mineral, and glucose levels; they adjust the body's metabolic balances, growth rates, and reproductive cycles; and they maintain the body's stress responses. Like exocrine and paracrine cells, endocrine cells are stimulated and inhibited by autonomic axons; the activities of endocrine cells are also modulated by circulating hormones, especially pituitary hormones. Both the neural and the hormonal signals to the endocrine system are ultimately regulated by the hypothalamus of the brain, which is the integration center for the body's visceral homeostasis. See: hormone
Endocrine health disorders usually result from the production of either too much or too little of a hormone.
|Adrenal cortex||Outer portion of gland on top of each kidney||Cortisol regulates carbohydrate and fat metabolism; aldosterone regulates salt and water balance||Hypofunction: Addison disease|
|Hyperfunction: Adrenogenital syndrome; Cushing syndrome|
|Adrenal medulla||Inner portion of adrenal gland; surrounded by adrenal cortex||Effects of epinephrine and norepinephrine mimic those of sympathetic nervous system; increases carbohydrate use for energy||Hypofunction: Almost unknown|
|Pancreas (endocrine portion)||Abdominal cavity; head adjacent to duodenum; tail close to spleen and kidney||Secretes insulin and glucagon, which regulate carbohydrate metabolism||Hypofunction: Diabetes mellitus|
|Hyperfunction: If a tumor produces excess insulin, hypoglycemia|
|Parathyroid||Four or more small glands on back of thyroid||Parathyroid hormone regulates calcium and phosphorus metabolism; indirectly affects muscular irritability||Hypofunction: Hypocalcemia; tetany|
|Hyperfunction: Hypercalcemia; resorption of bone; kidney stones; nausea; vomiting; altered mental status|
|Pituitary, anterior||Front portion of small gland below hypothalamus||Influences growth, sexual development, skin pigmentation, thyroid function, adrenocortical function through effects on other endocrine glands (except for growth hormone, which acts directly on cells)||Hypofunction: Dwarfism in child; decrease in all other endocrine gland functions except parathyroids|
|Hyperfunction: Acromegaly in adult; giantism in child|
|Pituitary, posterior||Back portion of small gland below hypothalamus||Oxytocin increases uterine contraction||Hypofunction: Diabetes insipidus|
|Antidiuretic hormone increases absorption of water by kidney tubule||Hyperfunction: Unknown|
|Testes and ovaries||Testes—in the scrotum||Testosterone and estrogen regulate sexual maturation and development of secondary sex characteristics; some effects on growth||Hypofunction: Lack of sex development or regression in adult|
|Ovaries—in the pelvic cavity||Hyperfunction: Abnormal sex development|
|Thyroid||Two lobes in anterior portion of neck||Thyroxine and T3 increase metabolic rate; influence growth and maturation; calcitonin regulates calcium and phosphorus metabolism||Hypofunction: Cretinism in young; myxedema in adult; goiter|
|Hyperfunction: Goiter; thyrotoxicosis|
genal glandBuccal gland.
haversian glandSynovial gland.
hemal glandHemal node.
interscapular glandBrown fat.
interstitial glandLeydig cell.
intestinal glandLieberkühn crypt.
glands of KrauseSee: Krause, Karl
lactiferous glandMammary gland.
Lieberkühn glandLieberkühn crypt.
Littré glandSee: Littré gland
Luschka glandSee: Luschka, Hubert von
major salivary gland
minor salivary gland
Montgomery glandSee: Montgomery gland
Morgagni glandSee: Littré gland
palpebral glandTarsal gland.
An excess of parathormone results in hyperparathyroidism; a deficiency, in hypoparathyroidism, with neuromuscular hyperexcitability manifested by carpopedal spasm, wheezing, muscle cramps, urinary frequency, mood changes, and lassitude. Blood calcium falls and blood phosphorus rises. Other symptoms include blurring of vision caused by cataracts, poorly formed teeth if onset was in childhood, maldevelopment of hair and nails, and dry and scaly skin. Hyperparathyroidism or hypersecretion results in a rise in blood calcium and fall in blood phosphorus. Calcium is removed from bones, resulting in increased fragility. Muscular weakness, reduced muscular tone, and general neuromuscular hypoexcitability occur. Osteitis fibrosa cystica is associated with hyperplasia and resulting hypersecretion of the parathyroids.
paraurethral glandSee: Skene gland
peptic glandGastric gland.
The pituitary is an endocrine gland secreting a number of hormones that regulate many bodily processes including growth, reproduction, and other metabolic activities. It is often referred to as the “master gland of the body.”
Hormones are secreted in the following lobes: Intermediate lobe: In cold-blooded animals, intermedin is secreted, influencing the activity of pigment cells (chromatophores) of fishes, amphibians, and reptiles. In warm-blooded animals, no effects are known.
Anterior lobe: Secretions here are the somatotropic, or growth hormone (STH or GH), which regulates cell division and protein synthesis for growth; adrenocorticotropic hormone (ACTH), which regulates functional activity of the adrenal cortex; thyrotropic hormone (TTH or TSH), which regulates functional activity of the thyroid gland; and prolactin, also called lactogenic hormone, which induces secretion of milk in the adult female. The gonadotropic hormones are as follows: in women, follicle-stimulating hormone (FSH) stimulates development of ovarian follicles and their secretion of estrogen; in men, it stimulates spermatogenesis in the testes. In women, luteinizing hormone (LH) stimulates ovulation and formation of the corpus luteum and its secretion of estrogen and progesterone. In men, LH also called interstitial cell-stimulation hormone (ICSH), stimulates testosterone secretion.
Posterior lobe: Hormones are secreted by the neurosecretory cells of the hypothalamus and pass through fibers of the supraopticohypophyseal tracts in the infundibular stalk to the neurohypophysis, where they are stored. Secretions here are oxytocin, which acts specifically on smooth muscle of the uterus, increasing tone and contractility, and antidiuretic hormone (ADH), which increases reabsorption of water by the kidney tubules. In large amounts, ADH also causes vasoconstriction, and is also called vasopressin.
Hypersecretion of anterior lobe causes gigantism, acromegaly, and pituitary basophilism (Cushing disease). Hyposecretion of anterior lobe causes dwarfism, pituitary cachexia (Simmonds disease), Sheehan syndrome, acromicria, eunuchoidism, or hypogonadism. Posterior lobe deficiency or hypothalamic lesion causes diabetes insipidus. Anterior and posterior lobe deficiency and hypothalamic lesion cause Fröhlich syndrome (adiposogenital dystrophy) and pituitary obesity.
racemose glandAcinar gland.
Rivinus glandSee: Rivinus, August Quirinus
Salivary secretion is under nervous control, reflexly initiated by mechanical, chemical, or radiant stimuli acting on taste buds in the mouth, olfactory receptors, or the eyes. Secretion may also be due to conditioned reflexes as when one thinks about food or hears a dinner bell. The nerve supply of the salivary glands is from the facial and glossopharyngeal nerves, which increase secretion, and from the sympathetic nerves, which decrease secretion. The blood supply is from branches of the external carotid artery.
Skene glandSee: Skene, Alexander
stomach glandGastric gland.
suprarenal glandAdrenal gland.
tarsal glandMeibomian gland.
thymus glandSee: thymus
Tyson glandPreputial gland.
urethral glandLittré gland.
von Ebner gland
vulvovaginal glandSee: Bartholin gland Bartholin, Caspar (the younger)
Waldeyer glandSee: Waldeyer-Hartz
Weber glandSee: Weber, Moritz I.
glands of Zeis
glandA cell or organized collection of cells capable of abstracting substances from the blood, synthesizing new substances, and secreting or excreting them into the blood (endocrine glands), into other bodily structures or on to surfaces, including the skin (exocrine glands). The simplest glands are single mucus-secreting goblet cells. Glands also produce digestive enzymes, hormones, tears, sweat, milk and sebum. LYMPH NODES are often miscalled ‘glands’.
glandan organ producing substances which are then secreted to the outside of the gland, sometimes by means of a duct, as in the exocrine glands, for example, the salivary mammary, lachrymal glands, but also in the case of ENDOCRINE GLANDS directly into the blood or lymphatic systems. Occasionally individual cells act as glands, for example, gland cells of Hydra producing digestive enzymes.
accessory lacrimal gland's They are the glands of Krause and Wolfring. These glands are histologically identical to the main lacrimal gland, but are located within the eyelids. These glands are responsible for basal (not reflex) tear secretion and appear to be under sympathetic neural control.
gland's of Ciaccio See glands of Wolfring.
ciliary sebaceous gland's See glands of Zeis.
ciliary sweat gland's See glands of Moll.
conjunctival gland Any gland that secretes a substance into the conjunctiva, such as the lacrimal, meibomian, Krause and Wolfring glands or a goblet cell.
gland's of Henle These are not really glands. They are folds in the mucous membrane of the palpebral conjunctiva, situated between the tarsal plates and the fornices, in which there are goblet cells (Fig. G2). Syn. crypts of Henle (strictly speaking this term refers only to the pit-like depressions).
gland's of Krause Accessory lacrimal glands of the conjunctiva having the same structure as the main lacrimal gland. They are located in the subconjunctival connective tissue of the fornix, especially the superior fornix (Fig. G2).
lacrimal gland A compound gland situated above and to the outer side of the globe of the eye. It consists of two portions: (1) a large orbital or superior portion; and (2) a small palpebral or inferior portion. It secretes the middle aqueous layer of the tears through about a dozen fine ducts into the conjunctival sac at the upper fornix although one or two may also open into the outer part of the lower fornix (Fig. G2). See dacryoadenitis; dacryops; fossa for the lacrimal gland; zygomatic nerve; tear duct.
gland's of Manz Tiny glands located near the limbus. They secrete mucin. The existence of these glands in man is not established.
meibomian gland's Sebaceous glands located in the tarsal plates of the eyelids whose ducts empty into the eyelid margin. They are arranged parallel with each other, perpendicular to the lid margin, about 25 for the upper lid and 20 for the lower. They secrete sebum. This sebaceous material provides the outermost oily (or lipid) layer of the precorneal tear film. It prevents the lacrimal fluid from overflowing onto the outer surface of the eyelid. It also makes for an airtight closure of the lids and prevents the tears from macerating the skin. The meibomian glands can be seen showing through the conjunctiva of fair-skinned people as yellow streaks (Fig. G2). Meibomian gland dysfunction (MGD) may be induced by blepharitis, chalazion, contact lens wear (particularly soft lenses) and ageing. The most common sign is a cloudy or absent secretion upon expression with symptoms of a mild dry eye. Hot compresses and lid massage will cure more than half of the patients; oral tetracycline will help in many of the others. Syn. palpebral follicles; tarsal glands. See posterior blepharitis; chalazion; precorneal film; internal hordeolum; keratoconjunctivitis sicca; meibomianitis; tarsus; Tearscope plus.
gland's of Moll Sweat glands of the eyelids. They are situated in the region of the eyelashes (Fig. G2). Syn. ciliary sweat glands.
tarsal gland's See meibomian glands.
gland's of Wolfring Accessory lacrimal glands of the upper eyelid situated in the region of the upper border of the tarsus (Fig. G2). Syn. glands of Ciaccio.
gland's of Zeis Sebaceous glands of the eyelids which are attached directly to the follicles of the eyelashes. Their secretion contributes to the oily layer of the precorneal film (Fig. G2). Syn. ciliary sebaceous glands. See marginal blepharitis; hordeolum.
Patient discussion about gland
Q. Anyone know if there is a connection between Fibromyalgia and your Thyroid gland? I have Fibromyalgia and I read that if your diagnosed with this you can have Thyroid problems also. If anyone knows out there please inform me. Many thanks.
Q. my friend ate a bar of chocolate and now her left neck gland is swollen any ideas why? no other symptoms
if it is an infection, you can usually find such other infection symptoms like : fever, pain in that swollen area, increased white blood cells (in blood work test), etc.
if it is an allergy, usually it will fade away itself in couple of days, or you can just try to consume anti-allergic drugs, such as : loratadine and maybe combined with dexamethasone.
Good luck, and stay healthy always..