Lecture 22 Flashcards
What are the three germ layers formed by gastrulation?
Ectoderm, mesoderm, endoderm
What are the functions of the placenta?
- nutrient and oxygen exchange between foetal and maternal blood streams
- removal of CO2 and other wastes from foetal blood
- secretes hormones into both bloodstreams
What is the difference between the placenta and the umbilical cord?
The placenta is the interface between the foetus and pregnant person, and the umbilical cord is the connection between the placenta and the foetus
What are the three hormones secreted by placental tissues? When are their secretions elevated?
Estrogen (estriol) , progesterone
- the end of the first trimester
What is the definition of organogenesis?
When the embryo forms organs
What is the definition of teratogen?
Molecules/other biological factors that can adversely affect development, especially organogenesis
- roaccutane, thalidomide
When does fertilization happen?
Fusion between two haploid gametes to produce a zygote
What prevents sperm from entering the ovum?
Biochemical reactions in the zona pellucida
How does sperm break through the oocyte’s membrane?
Enzymes in the acrosome of the sperm break down the layers of the follicular cells in the corona radiata
How many sperm are needed to break through the membrane, and how many penetrate the oocyte?
Many, one
What happens after the sperm enters the ovum?
Two haploid pronuclei develop and mingle chromosomes, forming a zygote
What is a blastomere?
Daughter cells produced during cleavage
What is a morula?
Solid ball of cells
What does the morula create once it enters the uterus?
Sheds the zona pellucida and creates a blastocyst
How does implantation happen?
The blastocyst fuses to the endometrium
- trophoblast erodes the endometrial epithelium and lodges the blastocyst within the endometrium
What is the difference between cytotrophoblast and syncytiotrophoblast?
Cyto: individual cells with plasma membranes
Syncytio: many nuclei sharing one cytoplasm
What are the four extra-embryonic membranes?
- Amnion (cavity for embryo to develop in)
- Yolk sac (pouch for distributing nutrients)
- Chorion (separates blastocoele from the trophoblast)
- Allantois (forms the umbilical cord)
What is the function o the trophoblast?
Surround each villus and is responsible for hormone secretion of the placenta
What is the function of hCG and what releases it?
- Human chorionic gonadotropin, maintains production of progesterone, supports the function of the corpus luteum
- the embryo
