Chapter 27- Human Development Flashcards
What is the process called when a blastocyst attaches to the uterine wall?
Implantation
What is pregnancy that occurs outside of the uterus?
Ectopic
What happens if an oocyte is fertilized by more than one sperm?
The zygote will be non-viable
How many germ layers are created by gastrulation?
3
When does the oocyte complete meiosis?
Upon contact with spermatozoa
What layer of the blastocyst will form the placenta?
Outer layer (trophoblast)
What do we call the first 9 weeks of development?
Embryonic stage
Which germ layer forms the skeletal system?
Both mesoderm and ectoderm
What are the three stages of development?
Pre-embryonic, embryonic and fetal
Where does fertilization of an oocyte occur?
In the uterine tube
What is the cortical reaction? What does it prevent?
It is a release of enzymes from cortical granules. Destroys sperm-binding receptors so that no more sperm may enter the oocyte
What causes completion of meiosis?
Fertilization
What is amphimixis?
Moment of conception
What is a zygote and how many chromosomes does it have?
Fertilized sex cell with 46 chromosomes
Which gamete provides organelles and cytoplasm to the zygote?
Oocytes
What is gestation?
Time spent in prenatal development
What happens during the first trimester?
Embryo development and rudimentary organs develop
What happens during the second trimester?
Development of organs and organ systems. Body shape and proportions change
What happens during the third trimester?
Rapid fetal growth, most organs are fully functional
Which stage is most critical during pregnancy?
First trimester
What happens during differentiation of blastocysts?
The new cells become specific tissues which are bound for specific function like bone, skin and heart muscle
Where does implantation occur?
Endometrium of uterus
Which part of the blastocyst becomes the embryo?
The inner cell mass
What is the basic process of gastrulation?
Rearrangement of cells of embryonic disc to form a trilaminar (or 3 layered) embryonic disc.
Creation of the 3rd (middle) germ layer
What are the three germ layers?
Ectoderm, mesoderm, endoderm
What is the umbilical cord and how is it formed?
Vessels that connect the growing fetus to the mother’s body. Early blood vessels in allantois become umbilical vessels.
Tissues around allantois become connecting stalk that forms the remainder of the cord
What tissues develop from the ectoderm?
Nervous system, epidermis, epithelium of nasal, oral and anal canals, eye muscles, ears, salivary glands, Arsenal medulla, pituitary and pineal glands
What tissues develop from the mesoderm?
Skeleton, cartilage and connective tissues. Skeletal, cardiac and smooth muscle. Blood/vessels and lymph, bone marrow, lymphatic tissue, kidneys and ureters. Gonads and genital ducts
What tissues develop from the endoderm?
Epithelium of digestive tract, respiratory tract, bladder let and urethra, accessory reproductive and digestive glands, thyroid and thymus
What are the hormones secreted by syncytial trophoblast?
Human chorionic gonadotropin, progesterone, human placental lactogen, placental prolactin, relaxin, estrogens
Prevents degeneration if corpus luteum
