Human Reproduction continued

The Pituitary Gland 

• The Posterior Pituitary gland does not synthesise hormones but stores and then secretes, amongst other hormones, the reproductive hormone Oxytocin.
• The cells of the hypothalamus manufacture hormones for the Posterior pituitary gland – these are neurosecretions and pass along the neural pathway to the posterior lobe.
• The hormones manufactured in the hypothalamus and stored in the posterior pituitary are secreted into the interstitial fluid and then into the circulatory system as usual
• The Anterior Pituitary gland does synthesise hormones.
• The anterior lobe synthesises hormones in response to stimulating hormones synthesised and released from the hypothalamus
• These stimulating hormones are called ‘releasing’ hormones or, ‘release-inhibiting’ hormones – part of the overall homeostatic processes of the body
• Reproductive hormones Prolactin and gonadotrophins are synthesised in the anterior lobe

Image

The Pituitary Gland in more detail. Neurones are shown leading from the hypothalamus. The longest neurones carry neurosecretions (hormones) into the posterior lobe of the pituitary. One of these hormones is Oxytocin. The shorter neurones also lie in the hypothalamus. These neurones stimulate the release of special hormones that will stimulate the synthesis of hormones in the Anterior pituitary. Follow the directional arrows and see the pathway of hormones then associate the correct reproductive hormones to each lobe.

So, you can see that the pituitary gland is complex; one lobe receives hormones only whilst the other lobe actually manufactures them when stimulated to do so.

• Check back to see that you can recall which are the gonadotrophins
• Processes, Words & Terms you need to learn.
  • Meiosis – cell division for production of sex cells (gametes)
  • Crossing over – of genetic material i.e., genes & significance of
  • Independent Assortment – at Meiosis II
  • Chiasma
  • Spindle
  • Haploid – half compliment of chromosomes (23 = n)
  • Diploid – full compliment of chromosomes (46 = 2n)
  • Reduction division – chromosome number halved
  • Oogenesis
  • Spermatogenesis - sperm formation
  • Placenta – function in transferring nutrients and harmful substances
  • Colostrum – function
  • Milk production (lactation) – role of oxytocin, positive feedback mechanism, neural stimulation
  • Menstrual cycle – sequence, hormones