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FERTILIZATION & DEVELOPMENT

FINAL Rb3 Bio- Fertilization and Development

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Dumo, Gallardo, Kabigting, Lames, Lim, Lumauig, Palomique, Panis, RavaloFINAL version -- 30 slides. Good luck, friends! :))

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Page 1: FINAL Rb3  Bio- Fertilization and Development

FERTILIZATION & DEVELOPMENT

Page 2: FINAL Rb3  Bio- Fertilization and Development

FERTILIZATIONInitiation of biological reproduction (through insemination or pollination) Main Functions:

1. Combine haploid sets of chromosomes from male and female zygote

2. Activate egg cell (Sperm + Egg contact = metabolic reactions)

Page 3: FINAL Rb3  Bio- Fertilization and Development

ACROSOMAL REACTION Release of hydrolytic

enzymes to break down coating of the egg Lock and Key Recognition (importance of specificity) Leads to fusion of sperm + egg membranes and entry of a single sperm Present in sea urchins

Page 4: FINAL Rb3  Bio- Fertilization and Development

SEA URCHIN FERTILIZATION

Page 5: FINAL Rb3  Bio- Fertilization and Development

MAMMALIAN FERTILIZATION

Page 6: FINAL Rb3  Bio- Fertilization and Development

FUSION OF MEMBRANESEffect #1: Fast Block to Polyspermy (1/10th sec) 1. Triggering of electrical response in egg membrane2. Ion channel gates open3. Na+ changes membrane potential (depolarization)

Page 7: FINAL Rb3  Bio- Fertilization and Development

Effect #2: Cortical Reaction (changes in egg cytoplasm)1.Production of IP32.Increase of Ca2+

3.Fusion of cortical granules with membrane4.Creation of osmotic gradient (water drawn in)5.Swelling (pushes outer layer away from membrane)

FUSION OF MEMBRANES

… and then the outer layer will serve as the FERTILIZATION MEMBRANE.

(prevents multiple fertilization)

… and then the outer layer will serve as the FERTILIZATION MEMBRANE.

(prevents multiple fertilization)

Page 8: FINAL Rb3  Bio- Fertilization and Development

CORTICAL REACTIONCauses granules from cortex to be released via exocytosis Enzymes released during this reaction hardens the fertilization membrane (zona pellucida for humans) Slow Block to Polyspermy

Page 9: FINAL Rb3  Bio- Fertilization and Development

SUMMARY OF FERTILIZATION1. Contact of sperm and egg

2. Acrosomal reaction3. Fusion of egg and sperm

membranes (Entry of only 1 sperm)4. Fast Block to Polyspermy5. Cortical Reaction 6. Slow Block to Polyspermy

Page 10: FINAL Rb3  Bio- Fertilization and Development

PREGNANCY/GESTATION

the condition of carrying one or more embryos in the uterus preceded by fertilization/conception duration is correlated to size(mice/rats – 21 days;elephants – 600 days)

Page 11: FINAL Rb3  Bio- Fertilization and Development

PREGNANCY/GESTATION

divided into trimesters (“3 months”) 1st Trimester: conception - Week 14 2nd Trimester: Week 14 – Week 28 3rd Trimester: Week 28 – Delivery/Labor/Week 40

Page 12: FINAL Rb3  Bio- Fertilization and Development

PREGNANCY/GESTATION

FIRST TRIMESTER Most profound development/rapid period of growth Fetus is most susceptible to damage (disease, alcohol, etc.)1. Fertilization2. Cleavage - succession of rapid cell divisions3. Zygote Blastomere Morula Blastocyst 4. Implantation – attachment of blastocyst to endometrium5. Start of Differentiation

Page 13: FINAL Rb3  Bio- Fertilization and Development

6. Embedding of blastocyst in endometrium7. Embryo directly gets nutrients from endometrium 8. Forming of placenta from tissues that grow out of

embryo9. Organogenesis

Ectoderm- nervous system + epidermis Endoderm – digestive tract and lining Mesoderm – other organs and tissues

10. Secretion of hormones to signal presence and control mother’s reproductive system (ex. HCG)

FIRST TRIMESTER

Human Chroionic Gonadotropin (HCG) – peptide hormone produced by embryo which keeps progesterone levels up to make uterus lining thick

Human Chroionic Gonadotropin (HCG) – peptide hormone produced by embryo which keeps progesterone levels up to make uterus lining thick

Page 14: FINAL Rb3  Bio- Fertilization and Development

FIRST TRIMESTER High levels of Progesterone causes…

- mucus in cervix (as protective plug)- growth of maternal part of placenta- size of uterus- cessation / stopping of ovulation and menstruation due to negative feedback on hypothalamus and pituitary gland

Breasts engorge

Page 15: FINAL Rb3  Bio- Fertilization and Development

SECOND TRIMESTER1. Growth up to 30cm; Activity

may be visible through abdominal wall

2. Hormone levels stabilize as HCG declines.

3. Corpus Luteum / uterine wall deteriorates.

4. Placenta secretes own progesterone to maintain pregnancy.

5. Uterus grows large enough to make pregnancy obvious.

Page 16: FINAL Rb3  Bio- Fertilization and Development

THIRD TRIMESTER1. Growth up to 3.5kg in

weight and 50cm in length

2. Fetal activity decreases3. Uterus expansion4. Displacement of

mother’s abdominal organs

* Hormones to induce and regulate labor

Page 17: FINAL Rb3  Bio- Fertilization and Development

HORMONES TO INDUCE AND REGULATE LABOR

1. Highest level of estrogen formation of oxytocin2. Oxytocin

- stimulates powerful contractions through smooth muscles of the uterus- stimulates placenta to secrete prostaglandins to enhance contraction

3. Positive Feedback: Physical and emotional stress associated with contractions stimulate release of more oxytocin and prostaglandins

Page 18: FINAL Rb3  Bio- Fertilization and Development

MOMMY & BABY WHY DOESN’T THE MOM’S BODY REJECT THE BABY?Recall: Immune System-Self and non-self recognition-The baby is considered non-self because it contains half a different set of chromosomes.

THE PLACENTAPhysical barrier (trophoplast)Allows red blood cells & nutrients to pass, but not lymphocytesT cells are restricted

Page 19: FINAL Rb3  Bio- Fertilization and Development

MOMMY & BABY WHY DOESN’T THE MOM’S BODY REJECT THE BABY?

FETUSlymphocytic suppressor cells that inhibit response to interleukin-2 masks fetus from interleukin-2’s detection of foreign objects

*Local dampening of immune system

Page 20: FINAL Rb3  Bio- Fertilization and Development

PARTURITION

Birth of fetus from uterus Labor = rhythmic uterine contractions 4 stages:

1. Dilation2. Fetal Exposure3. Umbilical Cord

Closure4. Placental Exposure/Delivery of Placenta

Page 21: FINAL Rb3  Bio- Fertilization and Development

DILATION• Thinned cervix opens up to around 3cm•Cervix is integrated in lower part of the uterus and on top of baby’s head• Full Dilation: 10 cm• Duration varies(4-8 hours)

Page 22: FINAL Rb3  Bio- Fertilization and Development

FETAL EXPOSURE• pressure on cervix, uterine contraction

• head must pass through narrowest part of pelvis, pubic arch and itroitus = PUSHING• burning sensation in labia• after birth of fetal head:

1. delivery by extension2. head points to side3. rotation to expose

shoulders

Page 23: FINAL Rb3  Bio- Fertilization and Development

UMBILICAL CORD CLOSURE• After fetal exposure

• Umbilical cord is cut and would close normally if not clamped

Page 24: FINAL Rb3  Bio- Fertilization and Development

PLACENTAL EXPOSURE• physiological separation done 15 – 30 mins after delivery • done with or without assistance (intramuscular injection of oxytocin followed by contraction)

Page 25: FINAL Rb3  Bio- Fertilization and Development

HORMONES INVOLVEDIN PARTURITION

a) To make cervix ready: - relaxin, prostaglandin,

estrogenb) For uterine contraction:

- prostaglandin, progesterone, oxytocin, specific positive feedback in oxytocin

Page 26: FINAL Rb3  Bio- Fertilization and Development

LACTATIONSecretion/formation of milk by the mammary glandsAspect of postnatal careDuring pregnancy…

– breast size due to the action of estrogen, adrenal steroids, and growth hormones which make ducts and alveoli in breast grow

– prolactin, progesterone also involved

Page 27: FINAL Rb3  Bio- Fertilization and Development

START OF SECRETORY ACTIVITY• in Milk producing unit / alveoli• caused by prolactin when estrogen and

progesterone are withdrawn from the blood

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• Colostrum: – also known as the ‘first milk’

of the mother– Recall: good for baby’s health – expected at pregnancy or

childbirth– milk secretion increases

after, usually 3rd or 4th day after birth

– breasts are engorged, tense, tender, feel warm

START OF SECRETORY ACTIVITY

Page 29: FINAL Rb3  Bio- Fertilization and Development

• Depends on baby’s suction• Contractile mechanism

– moves milk fr. alveoli to ducts

• During suckling..– pressure in mother’s breasts– nerve impulse fr. sucking of baby– path of impulse : sensory neurons in nipples

hypothalamus in the brain pituitary gland– Pituitary gland secretes oxytocin (for contraction of

myoepithelial cells of alveoli and ducts containing milk)

EJECTION OF MILK

Page 30: FINAL Rb3  Bio- Fertilization and Development

EJECTION OF MILK

• Maintenance of Breastmilk Production– What is needed?

• Prolactin• Sucking – for removal of

milk, release of prolactin• Milk pressure, hence

periodic breast feeding• Continuous unless there is

congestion, emotional disturbance