Milk Ejection
Uterus
Ovaries
The suckling of a newborn on a mother's breast has four effects. Firstly, it stimulates the sensory nerves, which then carry the signal from the breast to the spinal cord, where these nerves then synapse at the dorsal horn with neurons that carry the signal to the brain. Secondly, in the arcuate nucleus, the sensory afferent input from the nipple inhibits neurons that release dopamine. Dopamine normally travels via the hypothalamic-portal system to the anterior pituitary lobe, where it inhibits prolactin release from lactotrophs. Therefore, inhibition of dopamine release leads to an increase in prolactin release. Thirdly, in the supraoptic and paraventricular nuclei, the sensory afferent input from the nipple triggers the production and release of oxytocin in the posterior pituitary lobe. Fourth, in the preoptic area and arcuate nucleus, the sensory afferent input from the nipple inhibits GnRH release. GnRH normally travels via the hypothalamic-portal system to the anterior pituitary lobe, where it stimulates the synthesis and subsequent release of FSH and LH. An important note: inhibiting GnRH release inhibits FSH and LH release and thereby inhibits the ovarian cycle.
The hypothalamic portal system allows hypothalamic hormones to be transported to the anterior pituitary without first entering the systemic circulation.
Oxytocin is originally produced and released from the paraventricular and supraoptic nuclei; however, it travels down through the hypothalamic-portal system and is finally "released" from the posterior lobe of the pituitary.
Duct Proliferation & Branching
Actions stimulated by prolactin binding at PRL receptor
Prolactin is produced in the anterior pituitary gland. More specifically, lactotroph cells produce prolactin in the anterior pituitary gland where it is stored and then released into the bloodstream.
Lactogenic Enzyme Synthesis
Mammary Gland Development
Breast Differentiation
Glandular Tissue Development
Milk Production
Hypothalmic-portal system
The hypothalamic portal system allows hypothalamic hormones to be transported to the anterior pituitary without first entering the systemic circulation.
Prolactin
Prolactin is produced in the anterior pituitary gland. More specifically, lactotroph cells produce prolactin in the anterior pituitary gland where it is stored and then released into the bloodstream.
Anterior Lobe of Pituitary
Prolactin-releasing lactotrophs
Gonadotrophs
Posterior Lobe of Pituitary
Oxytocin
Oxytocin is originally produced and released from the paraventricular and supraoptic nuclei; however, it travels down through the hypothalmic-portal system and is finally "released" from the posterior lobe of the pituitary.
HYPOTHALAMUS
Newborn baby's action of suckling begins signal transduction
Preoptic Area
Paraventricular Nucleus
Supraoptic Nucleus
Arcuate Nucleus
Spinal Cord
Lactating Mother
Breast
Hypothalamic Pituitary Axis-Prolactin
