Endocrine system

Endocrine system

There are two inside excreting specialised structures:

  • hemadens
  • the solitary endocrine cells
  • Hemadens: central, peripheric.
    • the pituitary body, an epiphysis, neurosecretory kernels of a hypothalamus concern the central
    • all concern the peripheric the others:
      • adenohypophysis dependent - a thyroid gland, a cortex of adrenals, sexual glands
      • adenohypophysis independent - epithelial bodies, the insular apparatus of pancreas, the solitary endocrine cells.

    There are true glands and glands of the admixed function (for example, pancreas simultaneously is iron choronomic and an incretion, sexual glands, a placenta, etc.)

  • the Solitary endocrine cells can be in various organs (in endocrine and not endocrine). These glands possess the raised functional activity, are called APUD - as system. Cells of this system absorb and decarboxylate precursors of amino acids and develop neuroamines (some authors consider as their neurotransmitters). These cells happen a various parentage:
    • the Neural parentage - educe from the excitatory crest (in a hypothalamus, a pituitary body, adrenals (marrow), thyroid glands, parathyroids.
    • not Neural parentage - cells of ovaries and spermaries educe from a source where are (GEP - system in a stomach, an intestine, pancreas, in nephroses, in heart.

Biological active materials developed by cells render aboriginal and distant actions. These actions by a vegetative nervous system are regulated.

All glands develop hormones. Hormones - the biological active materials possessing strictly specific and selective effect, capable to raise or lower level of vital activity of an organism.

Steroid hormones - are effected from cholesterol in a cortex of adrenals, in sexual glands.

Polypeptide hormones - albuminous hormones (insulin, Prolactinum, an adrenocorticotrophin, etc.)

Hormones derivatives of amino acids - adrenaline, Noradrenalinum, Dofaminum, etc.

Hormones derivatives of fat acids - Prostaglandinums.

On physiological action hormones are sectioned on:

  • Starting (hormones of a pituitary body, an epiphysis, a hypothalamus). Influence other hemadens
  • Executors - influence separate processes in tissues and organs

The organ reacting to the given hormone is an organ-target (effector). Cells of this organ are supplied by receptors. The mechanism of action of hormones is distinguished, rate of abjection of hormones varies within days as there is a day-night rhythm of abjection of hormones.

Means of delivery and efficacyy of action of hormones are various:

  • the Humoral path - on haemocapillars, such is by carried out distant effect
  • there Can be an abjection of hormones to surrounding intercellular lymph, the aboriginal paracrine effect is thus carried out.
  • the Neurohormonal path assumes hormone accumulation in the excitatory cells and their transportation on axons through axobasal synapses.

Regulation of entering of a hormone in blood descends, as a rule, on negative feedback mechanism. The superfluous maintenance of a hormone in blood leads to inhibition of their effecting and on the contrary.

The biological effect of hormones is reduced to homeostasis maintenance. Changes choronomic, an internal environment are accompanied by change of rate of development of hormones. All these endocrine systems are disseminated on an organism, but have a number of the general signs:

  • Absence of lead-out ducts as the developed materials arrive directly in blood.
  • Possess high degree of vascularization.
  • Hormones developed in cells are formed in small quantities and possess the raised biological potency
  • In endocrine cells the synthetic and secretory apparatus is intensively educed.

The endocrine system is distinguished by close morphofunctional communication with the excitatory system by means of neurosecretory cells. A generality of functions of endocrine system based on interrelation and strict submission (subordination).

Development sources

  • epithelial bodies, an adenohypophysis have the Ectodermal parentage thyroid.
  • the Endodermal parentage has the insular apparatus of pancreas.
  • mesodermal adrenals, sexual glands have a parentage.
  • the Neural parentage has a hypothalamus, a neurohypophysis, an epiphysis, marrow of adrenals.

Hypothalamus

The hypothalamus educes from a basal part of mediate cerebral bladder. Belongs to a CNS, and unites to the excitatory and endocrine system in neurosecretory system. Supervises all hemadens through a pituitary body. In grey matter of a hypothalamus there are neurones and neurosecretory cells organised in kernels. Excrete 32 pairs kernels. The hypothalamus control is carried out by means of a neurosecretion on 2 pathes:

  • Neural - on axons
  • Humoral - on pots

In a forward part of a hypothalamus there are 2 didymous cores:

  • supraoptic nucleus which excretes a vasopressin (antidiuretic hormone)
  • paraventricular nucleus which cosecretes Oxytocinum (reacts on a uterus myometrium, myoepithelial cells of a mammary gland)

These hormones on axons go to a back lobe of a pituitary body.

The average part of a hypothalamus is compounded by fine neurosecretory cells forming actuarial nucleus and ventromedial. Hormones arrive on axons in a primary haemocapillary network. These kernels excrete hormones capable to narrow and dilate pots. Their formation depends on the maintenance in blood of products of a metabolism of a cardiac muscle. Neurosecretory activity tests influence of the higher parts of a brain and an epiphysis.

Pituitary body

The pituitary body concerns the central endocrine organs. It is located under the brain establishment. Consists of 2 parts:

  • an adenohypophysis - a forward lobe and a mediate part
  • a neurohypophysis - a back lobe

The pituitary body educes from two germs on 4-5 week of embryonic development: from ectodermal and neural pouchs.

From an epithelium covering an oral cavity the pouch (Rathke's pouch) to the brain establishment evaginates. On 8 week this pouch is abjointed from an oral cavity. The back lobe - a diverticulum of mediate bladder starts to be formed. Then there is a differentiation of cells, and with 9 for 20 week synthesis of hormones begins

The forward lobe compounds 75 %. It is formed by epithelial bands between which are sinusoid haemocapillars which it is accompanied by a quaggy copulative tissue. Cells of a forward lobe are called adenocyteses. They happen depending on the attitude to a coloration chromophilic (45-45 %) and chromophobic (55-60 %)

Chromophobic adenocyteses share on:

  • undifferentiated cells
  • cells differentiations being at different stages
  • specialised cells
  • follicular cyst cells (carry out basic, phagocytizing functions)

The mediate part of a pituitary body at the human is educed weakly (compounds 2 % from pituitary body mass). Consists of haemocapillars and bands of epithelial cells with a basphilic cytoplasma. These cells are capable to develop a secret and it to accumulate. Their secret are melamine cyto tropine, a lipotropin.

The back lobe of a pituitary body (neurohypophysis) is formed ependimoglial by cells - pituriocytes. In a neurohypophysis it is a lot of fascicles of axons going of a forward hypothalamus. On axons from a hypothalamus the vasopressin and Oxytocinum is brought. In a back lobe these hormones collect and then are as required excreted in blood.

Epiphysis (pineal gland)

The epiphysis is pawned on 5-6 week in the form of a diverticulum of a roof of a diencephalon. On 7-8 week the copulative tissue grows into a germ of a mediate ventricle and the differentiation of cells begins. The epiphysis becomes covered by a connective tissue cover which divides it into lobes and compounds a gland stroma. Epiphysis secretory cells - pinealocytes (light, larger, and dark fineer). Supporting cells are called gliocytes. Glial cells are an astroglia. The greatest dawn an epiphysis passes in 5-6 years, then it involution thus descends some reduction of quantity of pinealocytes which will atrophy, and instead of them the copulative tissue is formed.

Epiphysis function: the epiphysis participates in regulation of processes proceeding in an organism cyclically, epiphysis activity bind to function of maintenance of a biorhythm (sleep and wakefulness change). Also it is considered that the epiphysis participates in acclimatisation of an organism to varying light exposure as was sensitivity of cells of an epiphysis to light is proved. The epiphysis participates in change of an orientation of synthesis of hormones - there is a serotonin development, at night melanin development (also regulates puberty) in the afternoon.

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