lesson 2: Embryonic development Flashcards
What is the first stage of embryonic development?
Blastocyst Formation ( week 1)
What occurs during fertilization?
Sperm meets egg
What are the two parts of the blastocyst?
- Embryoblast: becomes the embryo
- Trophoblast: will form placenta
What are the two layers formed from the embryoblast?
- Epiblast: becomes embryo and amniotic sac
- Hypoblast: forms extraembryonic structures (yolk sac)
What are the three germ layers formed from the two layers?
- Ectoderm
- Mesoderm
- Endoderm
What does the ectoderm form?
- outer layer
- Nervous system (brain, spinal cord, nerves)
- Skin, hair, nails
- Eyes, ears, nose lining
What does the mesoderm form?
- middle layer
- Muscles, bones, cartilage
- Blood, blood vessels, heart
- Kidneys and reproductive organs
What does the endoderm form?
- inner layer
- Digestive system (stomach, intestines)
- Respiratory system (lungs, trachea)
- Liver, pancreas, thyroid, bladder lining
What hormone does the embryo release after attachment to the uterus?
Chorionic gonadotropin (hCG)
What does hCG do in relation to menstruation?
Stops menstruation
What does a pregnancy test detect?
hCG
What are the four basic types of tissues in the human body?
- Epithelial
- Connective
- Muscle
- Nerve
What is the function of epithelial tissue?
Covers surfaces (skin, organ linings)
What is the function of connective tissue?
Supports & connects (bone, blood, fat, cartilage)
What is the function of muscle tissue?
Allows movement (heart, skeletal, smooth muscles)
What is the function of nerve tissue?
Transmits signals (brain, spinal cord, nerves)
what happens in the 1st week
Blastocyst Formation
* fertilization (sperm meets egg)
* cell division
* blastocyst formation (4-5 days after fertilization)
–> cell divides into blastomeres
–> blastomeres implants into the uterus
–> 2 parts: embryoblast, trophoblast
what happens in the 2nd week
Bilaminar Disc Formation
embryoblast transforms into 2 layers:
1. epiblast: becomes embryo and amniotic sac
2. hypoblast: forms extraembryonic structures (yolk sac)
what happens in 3rd week
Trilaminar Disc Formation
2 layers now form 3 germ layers
1. ectoderm (outer layer)
2. mesoderm (middle layer)
3. endoderm (inner)
