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Reproductive System

Males have testes(2)

  1. Produces sperm(small mobile cells)
  2. Produces millions of sperms per day
  3. Produces Testosterone(made by leydig cells)

Testes

  1. located inside the scrotum
  2. has seminiferous tubules
  3. has rate testis
  4. has sertoli cells
  5. has lumen(is a hole down the center of the hollowed tube)
  6. has spermatogonium(a germ cell from where sperm comes from)

Ovaries

Ovaries are 2 structures in a female reproductive system that produces eggs.

Ovarian Cycle

Overian Cycle lasts 28 days

Each month an egg goes through the maturation process called the ovarian cycle

. This cycle creates a secondary oocyte and that can be fertilized by sperm to result in a pregnancyPrimary oocytes that are destined to be ovulated will be develop in the ovaries

Completed Meiosis I – Before ovulation

and ejected(Day 14) out of the ovary as a secondary oocyte to be picked up by fimbriae and swept into the uterine tube to hope for fertilization

  1. Inside ovaries eggs develop in structure called (Day 15 to Day 28)Primordial follicles(Day 0) – One egg cell surrounded by granulosa cells
  2. Pre-antral Follicles
  3. Early antral Follicles
  4. Mature Follicle
  5. The one that gets ovulated is called dominant follicle.
  6. Atresia(Degenerate) – Other follicles degenerated and dies – Women loses 15 to 25 eggs per menstrual cycle to atresia, while only one gets ovulated.
  7. Antral refers to antrum
  8. Antrum is basically a fluid produced by the granulosa cells
  9. Theca cells have receptors for luteinizing hormone(LH) from the anterior pituitary. When LH binds theca cells, they produce a hormone called androstenedione. theca cells give this androstenedione to the ganulosa cells, who then convert it to estrogen and release it into the blood
  10. Follicles develop over the first 13 days
  11. Cumulus oophorus
  12. Granulosa cells develop and become more numerous as follicle matures
  13. Granulosa cells also secretes few hormones
    1. Estrogen
    2. a little Progesterone
    3. and some inhibin
  14. On day 14 you feel pelvic pain
  15. Sometimes 2 or more follicle pops out and thats how twins are developed
  16. The follicles after day 14 transforms into structure called the corpus luteum(CL)
  17. At 50 – 51 females undergo menopause. First frequency ovarian cycle decreases and then it eventually stops. Cessation of ovulation is called menopause

Ovaries loss the ability to respond to signalling hormones from the brain called gonadotropins

  1. Secrete the female sex hormones
    1. Estrogen – Prepare the inner lining of the uterus(Endometrium) for implantation
    2. Progesterone – means – Pro – For; Gest – gestation – erone – hormone –
      1. It mainly stimulates the uterine lining to prepare for implantation and gestation.
      2. It increases the blood flow to the endometrium by stimulating and development of special arteries in the endometrium called spiral arteries
      3. Spiral arteries allow the embryo to eventually have good access to nutrients from the mother’s blood stream.
      4. Increases uterine secretions from the special glands in the endometrium. These secretions are important for nourishment of embryo.
      5. Progesterone reduces the contractility of the muscles of the uterus to let the embryo not disturbed
      6. Suppress the production of FSH, LH in anterior pituitary by the process of negative feedback
    3. inhibin – Lowers the amount of FSH(Follicle Stimulating Hormone) that comes from anterior pituitary gland. Inhibin’s role is to inhibit FSH release from the anterior pituitary
      1. Inhibin A
      2. inhibin B

Women usually lose around 40 milli litres of blood per menstrual phase

Apoptosis

Thats the process that cells use to sort of self destruct and die

Zona Pellucida Separated the granulosa cells from the actual egg

Gap Junctions – Through gap juctions granulosa cells send through little chemical signals

Germs Cells – Oogonia. This homologous to spermatagonia in males.

Oogonia(2n – 2 copies of chromosome) goes through a ton of mitotic divisions to make more of themselves. At 7th month this production will stop. it will generate about 2 to 4 million i.e 1 to 2 Million per ovary. It will generate primary oocyte(2n)

oo in oocyte refers to egg

cyte refers to cell

Enzyme – is a protein that carries out specific taskPrimary oocyte —-> Meiosis is used to reduce our chromosome(DNA) copies. –> These primary oocytes are in meiotic arrest.

Spermatogonium

undergo mitosis and split into two spermatogonium.

  1. One spermatogonium splits into a primary spermatocyte
  2. primary spermatocyte divides and differentiates into 2 secondary spermatocytes(Meiosis)

Secondary oocyte

Meiotic Arrest for 12 to 13 Years and then after puberty

  1. primary oocyte tries to split into 2 secondary oocyte
    1. Polar Body(does not have cytoplasm)
    2. Secondary oocyte
  2. Secondary oocyte ovulated and meet the sperm cell and the sperm nucleus and the egg nucleus create a joint nucleus(meiosis 2)
  3. Not this creates 2
    1. Polar Body
    2. Ovum

It becomes zygote

Mitosis

Enlarge and split into two identical daughter cells that are genetically identical to the orginal cell

Primary spermatocytes are created from spermatogonium by mitosis

Meiosis I

Each of the daughter cells have half of the chromosomes

Primary spermatocyte undergo meiosis

  1. Prophase I
  2. Metaphase I
  3. Anaphase I
  4. telophase I
  5. cytokinesis

primary spermatocytes into 2 secondary spematocytes

2 spermatids per secondary spermatocyte are created

Primary Spermatocyte = 23 pairs of chromosomes

Each Chromosome = pair of sister chromotids

23 chromosomes each with their sister chromotids

Meiosis II

spermatid = 23 single copies of each chromosome

Sperm (1 copy of each(23) chromosome) ==> Egg (1 copy of each(23) chromosome)===> Nuclei Fuse = set of 23 pairs of chromosomes i.e, one set from father’s sperm, one set from mother’s egg.

Spermatids differentiate into spermatozoa1 spermatozaoa = 1 sepre

Seminiferous Tubules

Peristalsis

sertoli cells

are separated by

  1. basal compartment
  2. lumenal compartment

Coordinated movement pattern is called peristalsis

Primary Functions of testes

  1. Sperm developed between two sertoli cells

Testosterone

Testosterone

  1. We produce chemical signals in our body that allow one part of our body to communicate with the other parts of our body and these signals are called hormones
  2. Testosterone is produced by Leydig cells. Leydig cells are one of the cells in testes
  3. Blood vessels carry testosterone
  4. Males have 7x to 8x more than the female
  5. Testosterone binds to gene
  6. https://interestingengineering.com/the-baffling-biology-behind-olympic-games

Functions of Testosterone

  1. Make reproductive organs for male
  2. Signals sperm production to other parts of the body at the age of 12 or 13
  3. Responsible for secondary sex characteristics (Facial Hair, Armpit Hair, Pubic Hair, Hair on arms and legs, chests)
  4. Responsible for deepening of your voice(Testosterone induces growth of the voice box(larynx)(Adam Apple))
  5. Responsible for male pattern fat distribution around the central part of the body
  6. Responsible for anabolism. It stimulates anabolism to build muscles
  7. Responsible for Muscle and Bone Growth(makes bone bigger in diameter and longer, after complete growth stops from further growth)
  8. Increases sex drives and in turn causes aggression
  9. Increase number of red blood cells and it does that by stimulating our kidneys. This is done by producing a hormone called Erythroporetin(EPO).
  10. Erythroporetin cause more blood cell creation
  11. Prostate that has cells are that stimulated by DHT or dyhdryotestosterone. Thus increase the risk of prostate cancer

Male pattern baldness is actually promoted by the excess DHT in the blood

Anabolism

Taking smaller components in our body. ex. proteins and building them up to bigger components, or aggregate of those components like muscles

There are two possibilities

  1. Dihydrotestosterone (DHT)
    1. In Male 7% of testosterone is converted to DHT
  2. Estrogen

In Male less than 1% is converted to Estrogen

Feedback Loop of Hormones

  1. Feedback loop is method of self regulation(Thermostat)
  2. Hypothalamus acts similar to thermostat. It regulates most of our feedback loop
  3. Hypothalamus will sense the amount of testosterone that’s floating through your blood. If there are not enough testosterone, hypothalamus will send a signal to another gland in the brain called Anterior Pituitary sends more hormones to the tested that increases their testosterone production
  4. Negative Feedback Loop – Conversely if there is too much testosterone in the blood Hypothalamus will sense that and it will stop sending signals to the anterior pituitary and the anterior pituitary will stop sending signals to the testes. It will decrease the testosterone
  5. Negative feedback loop is used to control the amount of testosterone in the blood.(Testosterone Homeostasis)

Homeostatis meaning to remain constant

Our DNA is made of millions of Genes. Our genes are little segments of DNA

Spermatogenesis

  1. Creation of sperm

Temperature Controlling Muscles

  1. Cremaster Muscle
  2. Dartos Muscle

Helps to regulate the temperature of the testes to produce the sperm

Cremasteric Reflex

Epididymis

  1. Located on top of the testes on either side
  2. A place for sperm to develop. Sperms gain more mitochondria
  3. Develop long tales called flagela
  4. Sperms will be sent to Vas Deferens

Vas Deferens

  1. Drains the epididymis of sperm. Brings the sperm upwards behind the bladder and intro the urethra
  2. Runs within a bundle called spermatic cord
  3. Inside the spermatic cord
    1. we have an artery that serves the testes

We have a vein that serves the testes

Accessory Glands

  1. Provide sperms the necessary things that they need along their journey
    1. Seminal Vesicle (2) – Contribute lot of fluid(Alkaline =ph greater than 7; rich in fructose) to sperm .i.e, 60% semen volume. Mitochondria have sugar that they can use to produce ATP. ATP is what the sperm use for energy to complete the long journey
    2. Prostate Gland – Contribute Prostatic Fluid – Increases the mobility of the sperm, once it reaches inside the vagina

BulBourethral Gland(2) – Contribute Fluid – Thick Lubricant for bothe the urethra and the vagina

Transport of Sperm

Siggital View is the cutting an object and seeing it from the side.

Transvers view is cutting an object and seeing it from the front

Erection

  1. When no erection Blood Flows into the penis = Blood Flow out of the penis

Starts in a brain

  1. (NE) Norepinephrine(Sympathetic Nervous System) cause the arteriole in the penis to stay constricted(Flaccid State)
    1. Sent to epididymis
    2. vas deferens
    3. accessory glands
    4. ejaculatory duct(located inside the prostate gland)
  2. Nitric Oxide Parasympathetic Nervous System(Erected State)

Neuron is the cell of nervous system responsible for sending messages

Transform of state of penis from a state called Flaccidity(no blood) to the state that is filled with bloodIn flaccid state arteriole are constricted

Penis

  1. Has 3 cylindirical vascular compartments covered with tunica albuginea(Supportive Structural Tissue)
    1. Corpora cavernosae (2)
    2. corpus spongiosum
  2. Bulbospongiosum
  3. meatus
  4. Blood flow through via
    1. Dorsal Arteris
    2. cavernosal arteris
  5. Lacunar Spaces
  6. Blood flows out via
    1. Dorsal vein

Cavernous vein

Ejaculation

  1. 3 to 5 ml per ejaculation contains 300 million sperms

Expulsion of sperm out of the reproductive tract

Semen

  1. Sperm + Fluid

Travels through a tube called urethra

Testosterone

  1. Responsible for Body Hair
  2. Deepening of Voice
  3. Muscle Growth
  4. Levels of Aggressions

Females have ovaries(2)

  1. Produces eggs
  2. Releases only one egg per month
  3. Produces Estrogen and Progesterone

Estrogen, Progesterone

  1. Plays a major role in the timing of the egg release from the ovaries
  2. Development of feminine traits

Ovaries and testes are homologous

Uterus

  1. is an organ, very strong, muscular
  2. Amniotic Fluid – Baby is swimming in this fluid
  3. has uterine arteris
  4. has uterine veins

Baby

  1. Lungs are full of amniotic fluid

Placenta

  1. Baby is connected with the placenta through umbilical cord
  2. Basel Plate – Mom’s tissue
  3. Pool of blood cells has oxygen, nutrients,(This pool belongs to mom)
  4. Fetus cells – little cells in white – trophoblast
  5. Through diffusion oxygen, nutirents,  is going into fetus’ blood cells and carbon di oxide leaving
  6. – Chorionic Plate – end layer of umbilical cord (Belongs to the fetus)
  7. Umbilical cord consists of
  8. Wharton Jelly Consists of
    1. umbilical artery(2) – Going away from the heart

umbilical vein.(Oxygen) – Going to the heart

Reproductive Cycle – 28 Days

  1. 28/0 – 28th day and 0th day are same – No gap between
  2. Ovulation happens at day 14
  3. Reproductive Cycle has 2 phases
    1. Follicular Phase(First 14 days)
      1. Day 7 to 14 – Proliferative Phase
      2. Day 14 to 28 secretory phase

Luteal Phase

Luteal phase  

Development phase of the corpus luteum(yellow body in latin)

Corpus Luteum requires LH to stay alive

No Pregnancy

  1. Corpus Liteum Withers away
  2. Reproductive cycle continues to repeat itself

On Pregnancy

  1. Implanted embryo start to produce HCG which rescues Corpus Luteum from atrophying and endometrium is thus maintained
  2. No menstruation happens because you are not losing the endometrium and the reproductive cycle is put on hold for the duration of the pregnancy

Blastocyst

  1. At the stage implantation our embryo is actually called a blastocyst

Resulting embryo that developes from Blastocyst starts to produce a special hormone called Human chorionic gonadotropin(HCG)

Ovarian Cycle Graph

Reproductive Triggers

Hypothalamus

  1. Releases a Hormone called Gonadotropin releasing hormone (GNRH)
  2. GNRH effects another part of the brain AnteriorPituitary

AnteriorPituitary

  1. Anterior Pituitary in response to GNRH releases 2 hormones
    1. Lutenizing Hormone (LH)
    2. Follicle Stimulating Hormone (FSH)
  2. LH and FSH primarily effect the male and female sex organs

Zygote

Sperm successfully meets an egg and create a cell called Zygote. It implants itself in the wall of the uterus

Gestation(9 months)

Development of fetus into the baby

Labor(Parturition)

Giving birth

Basics of Egg(Oocytes) Development

Oogenesis

Ovaries initially creates egg during gestation – When a baby girl is in their mother’s womb the baby girl’s entire egg supply will be created but will remain in an inactive state

Ovulation

Pusing out of ovary

Estrogen

  2. Males also produce estrogen.
  3. Estrogen is produced in females primarily by the ovaries
  4. Placenta also produce some estrogen
  5. Little bit made by adrenal gland
  6. Anterior Pituitary Hormone called FSH(Follicle Stimulating Hormone) causes Follicles in the ovaries to develop.
  7. When the follicles of ovaries develop two group of cells within them team up and start to release estrogen into the blood stream.
    1. Theca Cells
    2. Granulosa cells
  8. In males estrogen has a role in maturation of sperms. It has to pair up with testosterone to incerease libido(sex drive)
  9. in females it is responsible for the growth and development of the female reproductive tract.
  10. It stimulated the growth of ovaries and follicles inside the ovaries.
  11. It causes the growth of smooth muscle components in female reproductive tract(Smooth muscle in the uterus, uterine tubes)
  12. It also stimulated the growth of the female’s extrernal genitalia and breats during puberty. The way it manages the breat growth by primarily increasing the fat that gets depoisted in the breasts
  13. Estrogen also responsible for female fat distribution pattern. i.e, Deposition of fat in the hips, breasts in contrast to the male fat distribution pattern i.e. Deposition in tummy

Cholestrol

  1. is a lipid molecule – Its kind of essential for life.
  2. We make lot of our hormones out of cholestrol
  3. Testosteron and estrogen are made from cholestrol.
  4. Type of molecules that carry cholestrol around
    1. HDL – High Density Lipoprotein
    2. LDL – Low Density Lipoprotein
  5. Density refers to the ratio of protein to cholestrol.
  6. HDL has lots of proteins and little bit of cholestrol

estrogen

  1. Estrogen actually reduces the bad cholestrol (LDL) and increases the good cholestrol(HDL).
  2. Preserves the strength of the bone in our skeletal system. Thoroughout our life bones are constantly undergoing renovation.- At a miscroscopic level they are constantly being broken down and built back up
  3. Estrogen slows down the cells that are involved with the breakdown portion of your bone renovations
  4. Estrogen gets lower when a female gets older she’s more at a risk of developing a bone condition, where the bones get brittle and weak and thats called osteroporosis
  5. Estrogen suppress production of FSH, LH
  6. Estrogen supports the growth of fetus lungs, liver
  7. Stimulates maternal tissue growth so the uterus enlarges to accomodate the growing fetus

Pregnancy

  1. Average pregnancy lasts about 38.5 weeks
  2. It consists of 3 phases(trimesters)
    1. 0 to 13 weeks
      1. Corpus Luteum and ovary produces most of the estrogen and progesterone that initially support the embryo and cause the development of the placenta
    2. 14 to 26 weeks
      1. Corpus Luteum degenerates and the placenta takes over as the primary hormone producer. New major endocrine organ(secretes hormones to regulate body functions) of the pregnancy
      2. Placenta generates estrogen throughout the pregnancy(38.5 weeks)
      3. Estrogen suppress FSH, LH release from the anterior pituitary by negative feedback
    3. 27 to 38.5 weeks
  3. Each trimester lasts about 13 weeks
  4. Hormones involved
    1. Estrogen
    2. Progesterone
    3. HCG – Human Chorionic Gonadotropin
  5. Anterior Pituitary Gland gets a little bigger during pregnancy and it starts to make more thyrotropin among other things
  6. Thyrotropin – Affects the thyroid gland and increases mom’s metabolic rate and that in turn increases her appetite and can cause hot flashes associated with pregnancy
  7. It takes lot of energy to support gestation and so its important that mom gets enough food to meet those increased energy needs
  8. In circulatory system – Blood volume has to increase by extra 1 to 2 litres of blood to make sure the fetus is nourished properly
  9. Mother’s blood pressure and pulse rise during pregnancy. And also as the uterus grows it will eventually compress the pelvic blood vessels underneath it and that will obstruct the venous return to the heart from the pelvis and legs.
  10. This can cause vericouse veins to develop
  11. Dermis(Skin) changes(Stretches)(Striae) will happen in abdomen, breasts, thighs, hips
  12. Lungs got to work 50% harder to provide oxygen to all the extra blood that mom’s got onboard for the fetus
  13. Growing uterus pushes up on mom’s diaphragm preventing her from taking in full breaths – She might develop a shortness of breat suring later trimesters
  14. Uterus put a pressure on the stomach as well and that can cause heart burn or gastric reflux in mom
  15. In the last few weeks of pregnancy the fetus sort of descends a bit in the pelvis and that reduces the upward pressure on the diaphragm so mom can breathe a bit better and the heart burn typically goes away
  16. The uterus drops a bit and put more pressure on the urinary bladder and it leads to needing to urinate a lot more frequently
  17. Weight Gain in Pregnancy
    1. Growing Fetus – 7 to 8 pounds
    2. Placenta + amniotic fluid = 6 pounds
    3. Extra Breast Tissue = 3 to 4 pounds
    4. Uterus growth – 4 pounds
    5. Extra blood volume = 4 pounds
    6. Fat = 3 to 10 pounds

Total = 25 to 35 pounds

Labor(Parturition) – Child Birth

  1. Typically occurs within about a week of mother’s due date (38 and a half week) + or – a week.
  2. Progesterone
    1. Levels drop off a bit by week 37
    2. Decrease in Progesterone causes contraction. False Labor Contractions or Braxton Hicks Contractions
    3. Estrogen levels continue to increase
  3. Posterior Pituitary
    1. Produces Oxytocin
      1. Stimulates Uterine Contractions

Parts involved in Parturition

  1. Uterus
  2. Placenta
  3. Amniotic sac
  4. Pelvis
  5. Cervix
  6. Femur
  7. Birth canal

Push on cervix(Fetus Drop on Uterus)

  1. Uterine Contraction
  2. Cervical Dilation
  3. Placenta start to secrets higher amount of other type of hormone called Relaxin
  4. Relaxin
    1. It loosens up some of the pelvic ligaments so that the pelvic bones can come apart a little bit to support the enlarging uterus
    2. It opens up the pelvic outlet by loosening the pubic symphysis joint between the left and right sides of the pelvis
    3. It also helps to dilute the cervix during labor
  5. Relaxations are done for
    1. to accomodate the growing fetus a bit better

to make it little easier for the baby to born through the pelvic outlet

Stages of labor

  1. Cervical Dilation
    1. Vaginal birth to take place the cervix needs to dilate fully typically to about 10 cms in diameter
    2. Very high doses of oxytosin being released from the posterior pituitary and that’s causing uterine contractions and these strong contractions cause membranes surrounding the fetus to release other hormones called
      1. prostaglandins – soften up the cervix and cause more uterine contraction.
    3. True Labor – Contractions continues to happen and produce prostaglandins
    4. Uterus side contract upward and pulls the cervix thinner and causes it to open up a bit
    5. Contractions also push the fetus against the cervix – This triggers that causes it to dilate even more
    6. Relaxin dilates the cervix even more
    7. As the cervix dilates the the mucus plug stuck at the opening of the cervix to seal it up during pregnancy comes out and gets discharged out of the vagina – This happens couple of days before a true labor to during labor – This is usually a sign that that labor is progressing
    8. Membranous sack that surrounds the fetus called the amniotic sac that will rupture during the labor and release its amniotic fluid
    9. Once the cervix dilates to about 4 cms moms body moves into a phase called active labor
    10. Cervic gets dilated to about 10 cms mom start to get the urge to push
  2. Expulsion of the baby
    1. Starts when the push signal is received and the fetal head enters the birth canal and ends with the birth of the new born
    2. Uterus continues to rhythmically contract to help push the mother’s baby out of the mother’s body
    3. Skull bones of the new born haven’t really fused together yet so they sort of slide to top of each other a bit and sort of compress the skull enough so that the baby can make it through the birth canal
    4. Once the baby head crowns or becomes visible to the healthcare professional assisting with the birth they will turn the baby to the side to make delivery of the rest of the baby’s body a little bit easier on both the mother and the baby
    5. Once the baby is out the umbilical cord that connected the baby’s belly button or umbilicus to the placenta gets cut and the baby gets cleaned up.
    6. The final step of labor is the delivery of the placenta and its associated membranes collectively called the after birth
    7. Vertex Presentation
      1. Most of the time baby’s head come out of the cervix first.
      2. less than 5% of births the baby’s oriented the other way around with its gluteal region or its legs set to come out  of the cervix first. This orientation is called the breech presentation
    8. Ceasarian Section
      1. Making incisions in the lower abdomen and uterus to deliver the baby that way directly through the anterior abdominopelvic wall
  3. Afterbirth
    1. Once the baby is delivered, Uterus continues to contract
    2. It causes the placenta to detach from the walls of the uterus and eject out of vagina
    3. Uterus continues to contract and return to its pregestation state
    4. Involution –
      1. Process uterus shrinkage

Also allows mom’s other abdominal organs to return to their normal locations after pregnancy

Labor can take anywhere between 7 to 20 hours

Breast anatomy and lactation

Lactation is a process where milk is made and ejected from the mammary glands inside the female breasts. Breast milk supplies all the nutrients that the baby require for the first 6 month of life.

Pectoralis Major Muscle

  1. Primary muscle of the chest

Mammary Glands

  1. Mammary Glands are modified sweat glands that are able to produce and eject milk
  2. Breasts of female and male has
  3. In women they develop around the time of puberty
  4. In men they actually wont get develop
  5. Expands in response to stimulating hormones such as estrogen and prolactin
  6. made up of cells called Myoepithelial cells

Myoepithelian Cells

are special cells in that not only are they lining the outside of the mammary glands but they also can contract and squeeze down on these glands to squeeze milk out of them. Milk is drained towards the nipple through ducts called lactiferous ducts and from there milk can be ejected out through the nipple through these tiny holes all over the nipple called nipple pores

Areolae – Dark circular area around the nipples

  1. They contain little bump called the areolar glands or Montgomery glands
  2. Areolar glands secrets a bit of oily substance called lipoid fluid
  3. Lipoid Fluid moisturizes the nipple so that it doesn’t get dry or cracked during breastfeeding. Lipoid Fluid in areolar glands has certain smell in it that attracts the baby
  4. Gives the infant a target

Fatty Tissue(Adipose Tissue)

Suspensory Ligaments(Cooper’s Ligaments) – help the breast anchroed to its chest wall.

Lactation Process

  1. Begins when the infant begin to suckle on mom’s breast
  2. Special receptors called mechanoreceptors in nipple gets activated and starts to send signals up the spinal cord and into mom’s brain to the hypothalamus
  3. Hypothalamus when it received these messages does 2 things
    1. Sends on signal to set of oxytocin neurons in the posterior pituitary gland telling them to make oxytocin
    2. Sends an off signal to  a special type of neuron(PIH neurons) in the anterior pituitary that releases a hormone called Prolactin Inhibiting Hormone. Prolactin in the anterior pituitary produces prolactin. Prolactin causes the mammary glands to start producing milk
  4. Ocytocin stimulated the myoepithelial cells that surround the mammary glands oxytocin stimulates them to eject the milk out of the nipple so the baby can be fed

Sound of baby’s cry can trigger this process by the hearing center to hypothalamus of a lactating woman

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