Endocrine system
From Wikipedia, the free encyclopedia
The endocrine system is an integrated system of small organs that involve the release of extracellular signaling molecules known as hormones. The endocrine system is instrumental in regulating metabolism, growth, development and puberty, tissue function, and also plays a part in determining mood.[1] The field of medicine that deals with disorders of endocrine glands is endocrinology, a branch of the wider field of internal medicine.
Contents
[edit] Function
The Endocrine system is an information signal system much like the nervous system. However, the nervous system uses nerves to conduct information, whereas the endocrine system mainly uses blood vessels as information channels. Glands located in many regions of the body release into the bloodstream specific chemical messengers called hormones. Hormones regulate the many and varied functions of an organism, e.g., mood, growth and development, tissue function, and metabolism, as well as sending messages and acting on them.
[edit] Types of signaling
The typical mode of cell signaling in the endocrine system is endocrine signaling. However, there are also other modes, i.e., paracrine, autocrine, and neuroendocrine signaling.[2] Purely neurocrine signaling between neurons, on the other hand, belongs completely to the nervous system.
[edit] Endocrine
A number of glands that signal each other in sequence is usually referred to as an axis, for example the Hypothalamic-pituitary-adrenal axis.
Typical endocrine glands are the pituitary, thyroid, and adrenal glands. Features of endocrine glands are, in general, their ductless nature, their vascularity, and usually the presence of intracellular vacuoles or granules storing their hormones. In contrast exocrine glands such as salivary glands, sweat glands, and glands within the gastrointestinal tract tend to be much less vascular and have ducts or a hollow lumen.
[edit] Autocrine
Other signaling can target the same cell.
[edit] Paracrine
Paracrine signaling is where the target cell is nearby.
[edit] Juxtacrine
Juxtacrine signals are transmitted along cell membranes via protein or lipid components integral to the membrane and are capable of affecting either the emitting cell or cells immediately adjacent.
[edit] Role in disease
Diseases of the endocrine system are common,[3] including diseases such as diabetes mellitus, thyroid disease, and obesity. Endocrine disease is characterised by dysregulated hormone release (a productive Pituitary adenoma), inappropriate response to signalling (Hypothyroidism), lack or destruction of a gland (Diabetes mellitus type 1, diminished erythropoiesis in Chronic renal failure), or structural enlargement in a critical site such as the neck (Toxic multinodular goitre). Hypofunction of endocrine glands can occur as result of loss of reserve, hyposecretion, agenesis, atrophy, or active destruction. Hyperfunction can occur as result of hypersecretion, loss of suppression, hyperplastic, or neoplastic change, or hyperstimulation.
Endocrinopathies are classified as primary, secondary, or tertiary. Primary endocrine disease inhibits the action of downstream glands. Tertiary endocrine disease is associated with dysfunction of the hypothalamus and its releasing hormones.
Cancer can occur in endocrine glands, such as the thyroid, and hormones have been implicated in signalling distant tissues to proliferate, for example the Estrogen receptor has been shown to be involved in certain breast cancers. Endocrine, Paracrine, and autocrine signalling have all been implicated in proliferation, one of the required steps of oncogenesis.[4]
[edit] Table of endocrine glands and secreted hormones
This is a table of the glands of the endocrine system, and their secreted hormones
[edit] Hypothalamus
Stimulate prolactin release from anterior pituitary.
Involved in orgasm, trust between people.[5] and circadian homeostasis (body temperature, activity level, wakefulness).[6] release breast milk
[edit] Pineal body (epiphysis)
[edit] Pituitary gland (hypophysis)
[edit] Anterior pituitary lobe (adenohypophysis)
Release Insulin-like growth factor 1 from liver
In male: spermatogenesis, enhances production of androgen-binding protein by the Sertoli cells of the testes
In male: stimulates Leydig cell production of testosterone
[edit] Posterior pituitary lobe (neurohypophysis)
Involved in orgasm, trust between people.[7] and circadian homeostasis (body temperature, activity level, wakefulness).[8] release breast milk
moderate vasoconstriction
Oxytocin and Anti-Diuretic Hormone are not secreted in the posterior lobe, merely stored.
[edit] Intermediate pituitary lobe (pars intermedia)
[edit] Thyroid
affect protein synthesis
affect protein synthesis, often functions as a prohormone
[edit] Parathyroid
(Slightly) decrease blood phosphate:
[edit] Heart
reducing systemic vascular resistance, reducing blood water, sodium and fats
reducing systemic vascular resistance, reducing blood water, sodium and fats
[edit] Striated muscle
[edit] Skin
[edit] Adipose tissue
[edit] Stomach
Enhances effects of cholecystokinin Stops production of gastric juice
Lowers rate of gastric emptying Reduces smooth muscle contractions and blood flow within the intestine[11]
[edit] Duodenum
Release of bile from gallbladder hunger suppressant
[edit] Liver
regulate cell growth and development
release of aldosterone from adrenal cortex dipsogen.
[edit] Pancreas
intake of lipids and synthesis of triglycerides in adipocytes Other anabolic effects
increases blood glucose level
Inhibit release of glucagon[13] Suppress the exocrine secretory action of pancreas.
[edit] Kidney
Increase absorption of calcium and phosphate from gastrointestinal tract and kidneys inhibit release of PTH
[edit] Adrenal glands
[edit] Adrenal cortex
Inhibition of glucose uptake in muscle and adipose tissue Mobilization of amino acids from extrahepatic tissues Stimulation of fat breakdown in adipose tissue anti-inflammatory and immunosuppressive
[edit] Adrenal medulla
[edit] Testes
Virilizing: maturation of sex organs, formation of scrotum, deepening of voice, growth of beard and axillary hair.
[edit] Ovary
These originate either from the ovarian follicle or the corpus luteum.
Other:
Protein synthesis:
Fluid balance:
Gastrointestinal tract:
Melanin:
Cancer:
Lung function:
[edit] Placenta (when pregnant)
Other effects on mother similar to ovarian follicle-progesterone
Inhibit immune response, towards the human embryo.
increase insulin resistance and carbohydrate intolerance