Chap 15 (repro) Flashcards
(Embryonic development) Fertilization
1+1=1
Egg+sperm=zygote
•one succeeds sperm… depolarizes egg to shut off access for other sperms
•23 chromosomes pairs
- Cleavage and implantation
Egg is FERTILIZED
•moves through oviduct travelling towards uterus
-mitosis (cell division) up to 8 cells
•no enlargement of cells=cleavage
16 cells
• a morula
-reached uterus 3-5 days after fertilization and diffuses
2 different groups FORM of the BLASTOCYST
- -trophoblast
- Inner cell mass
-both part of blastocyst
Blastocyst
Spherical structure “germ pouch”
•hollow pouch for new cellular development
Group 1: tropoblast
•nourishment •outer layer of blastocyst -membrane develops into CHORION •chorion——placenta development -provides nutrient, 02 and waste removal
Group 2: inner cell mass
-inner layer of blastocyst
•develops into the embryo ITSELF
-positions against endometrium
5th-7th day will attach to endometrium and sink into wall
Implantation
Nestling of the BLASTOCYST into the endometrium
•complete at 10th to 14 th day
-woman is PREGNANT
Human chorionic gonadotrophin (hCG)
Same effects as LH
•maintains corpus luteum past degeneration time
•estrogen and progesterone secrete
-prevents menstruation
-placenta secretes sufficient nutrients but corpus is less important
Embryonic disk
Inner cell mass FLATTENS to form a disk shaped structure when amniotic fluid forms
•connects blastocyst to endometrium
-2-3 layes (ectoderm, endoderm, mesoderm)
3 germ layers
Ectoderm: outer layer (closest to amniotic cavity)
Endoderm: inner layer
Mesoderm: develops later between ectoderm and endoderm
Gastrulation
Process of FORMING these 3 layers
-SECOND WEEK
3 layers
Developing embryo: gastrula
-organs tissues and cell body derived
•to do with gastrulation
Morphogenesis
Gastrulation starts this process
•series of events that form distinct structures of an organism
•cells of embryo to become different cells like arms
Differentiation
Cellular process enables a cell to develop particular SHAPE and functions that are different from other cells
Neuralation
Process of forming the NEURAL tube marks start of organ formation
•spinal and brain formation
-heart begins to form
-18th day is heartbeat
4th week
Rapid growth differentiation
-blood vessels
-lungs kidneys lobe and face structure
Menstruation will be 2 weeks late
5th week
- head is large in comparison to rest
- eyes open
- 1,3 cm
- differentiation
7th-8th week
Human features
- organs formed
- nervous system
- skeleton is cartilage
- genetic sex determined
- nostrils
6th week
Brain grows
- limbs
- gonads produce hormone
8th week
Enlarged organs and growth
-is a FETUS
•paper clip size
Extra-embryonic membrane
-protection/nutrition/excretion/respiration
- alla tous
- amnion
- chorion
- yolk sac
All expelled after birth
Placenta
-chorion into placenta
•stringy projections extend from chorion into the uterine lining
•begin placenta development at 10 weeks
•disk shaped organ that is RICH in blood vessels
-attaches embryo to uterine wall for metabolic exchange
1) embryos actual tissue
2) mothers circulatory pools
Umbilical cord
A rope like structure •end of 8th week starts to form -enlarged amniotic sac •naval of fetus to centre of placenta •oxygen depleted blood-fetus to placenta •exigencies rich blood-blood to fetus
Diffusion
•umbilical cord
First Trimester •1-12 weeks
•body length growth accelerates
•head growth slows
•skeleton cartilage hardens and bones develop
_reproductive organs distinguishable
Second Trimester •13-24 weeks
•4th month -heart beat is strong -bones of skeleton form -brain grows rapidly/ nervous system functions -fewtus legs grow so MOVEMENT 5th month: -covered in layer of hair and oil 6th month: -little fat and pink skin from blood
Third Trimester•25-38 weeks
-final
-fetal brain cells develop quicker
-testis descend if male
-fat in skin
-digestive and respiratory systems
•NUTRITION important!!
40 weeks approx ready for birth
Teratogen
Agents that cause structural abnormalities due to exposure of substances in pregnancy
Ex) cigarettes, alcohol, drugs
•affect health of the fetus during pregnancy
-physically, mentally, developmental delays
Alcohol: FAS
Fasd: alcohol consumption during pregnancy that results in disorder of fetus
•physical and mental
•weight, he aight, face, memory, aggressive, learning
Nine months of pregnancy
1st: conception-3rd month
2nd: 4-5 months
3rd: 7th- birth
Parturition
•BIRTHING process (3stages) •events associated = labour -uterine contractions -15-20min and 20-30s become stronger •hormonal and neural components ~OXYTOCIN helps uterine stretching for contractions
Contractions
Push fetus DOWN the cervix and stretched until birth occurs
Breech
Feet first
•dangerous for mom and baby
•Caesarean section of unturnable
(Incision in abdomen)
Lactation
Hormones control onset lactation
•breast development like puberty due to estrogen and progesterone (milk prep)
-Prolactin : hormone for milk production
(Not secreted in pregnancy)
Prolactin
Hormone for milk production
•ANTERIOR pituitary
-colostrum is before milk (yellowish)
•oxytocin help out
Suckling
Secretion of oxytocin from posterior stimulates contraction of milk glands and ducts for lactation
Oxytocin
Produced in POSTERIOR
•causses weak contractions of smooth muscles within breasts to force milk into ducts
Dilation stage
Uterine contractions and oxytocin cause cervix to OPEN and dilate
•amniotic sac BREAKS -WATER BREAK and amniotic fluid is released through vagina
•lasts 2-20h
Expulsion stage
Forceful contractions push the baby through the cervix to the birth canal
•as bangs moved through= head rotated making it easier for body to pass through
~this stage usually lasts 2h
Placental stage
Placenta and umbilical cord are expelled from uterus
•expelled placenta -afterbirth
~lasts 10-15min afterwards
