final rb3 bio- fertilization and development
DESCRIPTION
Dumo, Gallardo, Kabigting, Lames, Lim, Lumauig, Palomique, Panis, RavaloFINAL version -- 30 slides. Good luck, friends! :))TRANSCRIPT
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FERTILIZATION & DEVELOPMENT
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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)
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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
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SEA URCHIN FERTILIZATION
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MAMMALIAN FERTILIZATION
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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)
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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)
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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
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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
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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)
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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
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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
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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
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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
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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.
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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
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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
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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
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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
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PARTURITION
Birth of fetus from uterus Labor = rhythmic uterine contractions 4 stages:
1. Dilation2. Fetal Exposure3. Umbilical Cord
Closure4. Placental Exposure/Delivery of Placenta
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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)
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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
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UMBILICAL CORD CLOSURE• After fetal exposure
• Umbilical cord is cut and would close normally if not clamped
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PLACENTAL EXPOSURE• physiological separation done 15 – 30 mins after delivery • done with or without assistance (intramuscular injection of oxytocin followed by contraction)
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HORMONES INVOLVEDIN PARTURITION
a) To make cervix ready: - relaxin, prostaglandin,
estrogenb) For uterine contraction:
- prostaglandin, progesterone, oxytocin, specific positive feedback in oxytocin
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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
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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
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• 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
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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