L10 Flashcards
Give an example of a nerve that folds w the development of the embryo
Phrenic nerve supplies the diaphragm starting the in the neck.
During development the embryo folds and stretches, the nerve must do the same.
What is spina bifida
Something doesn’t fuse and stays open to the environment - specifically vertebrae
What is the cleft lip
part of the bone fails to fuse
Explain the process of fertilization day 1
Day 1: Sperm/ovum meet in uterine tube 12-24 hours post ovulation.
Sperm Penetrates corona radiate and zona pellucida
Fusion of ovum and sperm cell nucleus occurs
Acrosome reaction makes ovum impermeable to other sperm the zona pellucida is now impenetrable
Zygote is formed
Explain the process of fertilization days 2-3
BLASTOMERE PHASE
Cleavage is rapid division of cells, still has zona pellucida around the outside.
First mitotic divison 30 hours post fertilization
Division layer cells get smaller/tighter as zona pellucida remains same size. This allow for formation of gap junctions so the cell can communicate.
Each cell AKA blastomere
The solid sphere AKA morula.
Explain the process of fertilization day 4-5
BLASTOCYST PHASE
Morula develops a cavity AKA blastocyst now.
Outer layer cells become thinner and suck fluid in becoming TROPHOBLAST.
Inner cell mass forms EMBRYOBLAST creating the EMBRYONIC POLE which the entire embryo is derived.
Blastocyst reaches uterine lumen ready for implantation
Describe the process of fertilization day 6-7
Bilaminar disc - embryo implants forms 2 layers.
Inner cell membrane differentiates to 2 layers in contact.
EPIBLAST: forms the embryo as develops a cavity which allows to split and divide.
The AMNIOTIC CAVITY develops within the epiblast mass.
HYPOBLAST: forms extraembryonic membranes to support the cell.
TROPHOBLAST surrounding the inner cell mass
Describe the process of fertilization days 7-8.
PRIMARY YOLK SAC DAY
The hypoblast develops a sac AKA YOLK SAC. This contains nutrients to supply the embryo before the placenta functions. (Extraembryonic hypoblast/membrane/ exocoelomic membrane)
Yolk sac goes down into blastocyst cavity and is filled w contents.
Yolk sac is engulfed when embryo folds, what left forms gut tube.
Describe the process of fertilisation for week 2.
Blastocyst reached uterine cavity, o2 nutrients and waste removal req.
Corpus luteum produces progesterone maintaining the endometrium
4 stages of implantation occur:
1- Shredding of zona pellucida restricting its growth
2- Apposition ensuring embryonic pole is in contact
3- Adhesion via molecular communication
4- Invasion
This initiates decidual reaction, maternal cells contribute to the placenta.
What do the outer layers of the blastocyst become?
Trophoblasts which differentiate into
CYTOROPHOBLASTS (single layer of inner cells) and SYNCTIOTROPHOBLASTS (Outer layer secretes HCG)
Describe the process of fertilisation week 3
Bilaminar disc develop to 3 distinct germ layers aka process of GASTRULATION. Initiated by the PRIMITIVE STREAK.
2 Layers formed (epiblast and hypoblast) already.
Hypoblast degenerates, and the epiblast gives rise to all 3 germ layers.
Epiblast become ECTODERM (top layer)
Hypoblast replaced by epiblast cells becoming ENDODERM (bottom layer)
Epiblast give rise to 3rd layer MESODERM (middle layer)
Describe the process of fertilisation for week 4 +
Flat disc fold into 2 directions
Longitudinal cephalocaudal begins and the head/tail are brought closer together.
Lateral transverse brings amniotic cavity down, creating the future gut tube inside the peritoneal cavity.
KEY HERE IS:
Need to know 2 types of folding happen, not what they do.
Name the terms: Epi Hypo Endo Ecto Meso
Epi - Above Hypo - below Endo - internal Ecto - outside (external) Meso - middle
What is the: Nervous system Muscular system Cardiovascular system GI system derived from?
Nervous: Ectoderm
Muscular: Mesoderm
Cardio: Meso/Endo
GI: Endo
