• Tuesday , 2 June 2020

What is hormone ? Function and type

hormone

 What is Hormone

  • A chemical substance secreted by an endocrine gland
  • It is mixed with the blood for transport to a local, distant target.
  • Target cells have specific receptors
  • Regulates cell reactions by affecting gene expression (often gene transcription factors)

Function of Hormone

  • Controlling the metabolism
  • Regulating growth, development, and reproduction
  • Name of endocrine glands
  • Hypothalamus
Pituitary (master)gland
  1. Anterior pituitary gland
  2. Posterior pituitary gland

Several Types of Gland

  • Thyroid gland
  • Parathyroid gland
  • Adrenal gland

Pancreas

  • Testes and ovary
  • Placenta during pregnancy
  • Female reproductive system
  • Layers of the uterus
  • Perimetrium- an outer layer
  • Myometrium –middle muscular layer

Endometrium- inner lining

Ovaries are female reproductive glands. They begin to function at puberty the functions of the ovary are controlled by hormones from the anterior pituitary. These hormones are called gonadotropins( follicle-stimulating hormone & luteinizing hormone) The menstrual cycle, under the control of the endocrine system, is necessary for reproduction. It is commonly divided into three phases, the follicular phase, ovulation, and luteal phase.

Follicular phase

This phase is also called the proliferative phase. Through the influence of a rise in follicle-stimulating hormone(FSH) during the first days of the cycle, a few ovarian follicles are stimulated . As they mature, the follicles increased the amount of estrogen. The estrogen initiates the formulation of a new layer of endometrium in the uterus, histologically identified as the proliferative endometrium the estrogen also stimulates cervix to produce fertile cervical mucus.

Ovulation

Ovulation is the phase of a female’s menstrual cycle in which a mature egg is released from the ovarian follicle into the oviduct. After ovulation, during the luteal phase, the egg will be available to be fertilized by sperm; concomitantly, the lining of the uterus ( the endometrium) is thickened to be able to receive a fertilized) egg. If no conception occurs, the uterine lining, as well as blood, will be shaded off during menstruation.

During the follicular phase,

estrogen suppresses the production of luteinizing hormone ( LH) from the anterior pituitary gland. When the egg has nearly matured, levels of estradiol reach a threshold above which this effect is reversed, and estrogen actually stimulates the production of a large amount of LH. This process, known as the LH surge, starts around day 12 of the average cycle and many last 48 hours. The release of LH matures the egg and weakens the wall of the follicle in the ovary, causing the fully developed follicle to release its secondary oocyte.

The secondary oocyte promptly matures into and ootid and then becomes a mature ovum. Which of the two ovaries –left or right-ovulates appears essentially random, no known left and right co-ordinations exists. Occasionally, both ovaries will release an egg. If both eggs are fertilized, the result is fraternal twins. After being released from the ovary, the egg is swept into the fallopian tube after about a day. An unfertilized egg will disintegrate of dissolve in the fallopian tube.

Luteal phase

The luteal phase is also called the secretory phase. An important role is played by the corpus luteum, the solid body formed in an ovary after the egg has been released from the ovary into the fallopian tube. This body continues to grow for some time after ovulation and produces a significant amount of hormones, particularly progesterone, progesterone plays a vital role.

In making the endometrium receptive to implantation of the blastocyst. Supportive of the early pregnancy, by increasing blood flow and uterine secretions Reducing the contractility of the smooth muscle in the uterus

 

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