Chap 15 (repro) Flashcards
(41 cards)
(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