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Gastrulation Pattern
Bio 3 Lecture 4
| Question | Answer |
|---|---|
| What are the different stages involved in vertebrate development? | Fertilization, cleavage, gastrulation, neurulation, organogenesis |
| What is fertilization and what are the 3 events that happen? | The fusion of a male and female gametes. 3 events: (1) Sperm penetration and membrane fusion (2) Egg activation (3) Fusion of nuclei |
| [Fertilization stages] What happens during sperm penetration and membrane fusion? (see image to identidy the parts) | The passage of sperm through 2 protective egg layers: The corona radiata zone and the zona pellucida |
| [Fertilization stages] What does the acrosome of the sperm contain? | Digestive enzymes |
| [Fertilization- Sperm penetration] Where does the sperm nucleus enters? | The egg's cytoplasm |
| [Fertilization- Egg activation] What blocks the polyspermy? | The release of Ca 2+ which alters the egg's coat |
| [Fertilization- Egg activation] The chromosomes are stimulated to continue what? | the second meiotic division |
| [Fertilization- Egg activation] What happens during egg activation, part one of Release of Ca+ ? | Increase in protein synthesis and metabolic activity. Rotation of cytoplasm |
| [Fertilization- Fusion of nuclei] Where do the sperm and egg nuclei migrate to? What happens when they fuse? | They migrate towards each other and form the diploid zygote when they fuse. |
| [Cleavage] What does the embryo have (poles)? | Animal pole (external tissues) and vegetal pole (internal tissue) |
| How does the blastula happen? When does it happen? | The blastomeres pump Na+ into the intracellular spaces which draws water. This results in a hollow ball of cells, aka a blastula (with the blastocoel). Happens during cleavage. |
| What are cleavage pattern influenced by? | The amount of yolk in the egg |
| What do eggs with high amounts of yolk undergo? | Meroblastic (incomplete) cleavage |
| What is it called when the cytoplasm concentrates at one pole? What does it result in? | The blastodisc. It results in the embryo not being spherical |
| What do eggs with moderate to little amounts of yolk undergo? What's the shape of the embryo? Example. | Holoblastic (complete) cleavage. The embryo is spherical and mammals have holoblastic cleavage |
| What is gastrulation? | It's a serie of cell shape changes and cell movements in the blastula |
| Cells move during gastrulation using a variety of cell shape changes, what are they? (see slide 15) | (1) Invagination (2) Involution (3) Delamination |
| What do gastrulation patterns depend on? | The amount of yolk |
| What do gastrulation in sea urchins form? | They have yolk-poor eggs, so they form hollow symmetrical blastulas |
| From what does the embryo develop in mammals? | From the inner mass of cells |
| What happens when inner mass of cells flattens? | It delaminates into 2 layers and the primitive streak forms |
| The cell movement gives rise to what? See slide 17 to visualize! | The 3 primary germ layers (Ectoderm, mesoderm and endoderm) |
| What is organogenesis? | The formation of organs (which happens just after gastrulation) |
| How does organogenesis happen? | Occurs by interaction of cells within and between the three germ layers |
| What determines the cell's fate? How can a cell fate be established? | The location of the cell in the developping embryo. A cell's fate can be established by interactions with neighboring cells |
| Where does organogenesis begin and what structures develop? | Organogenesis in vertebrates begins with neurulation where the notochord, the neural tube develop and the neural crest. |
| What is the notochord, neural crest and the neural tube? | The notochord provides structural support and site of attachment of skeletal muscles. The neural tube will form the spinal cord. The neural crest forms the PNS (peripheral nerve system). |
| Identify the notochord, neural tube and neural crest | see slide 19 |
| How long does human development takes form fertilization to birth? How many trimesters? | 266 days, aka 9 months. 3 trimesters |
| [Extraembryonic membranes] What is the amnion? | It encloses the amniotic fluid |
| [Extraembryonic membranes] What is the chorion? | It contributes to the placenta in mammals |
| [Extraembryonic membranes] What is the yolk sac? | It's the food source in bird embryo (also found in mammals but not nutritive) |
| [Extraembryonic membranes] What is the allantois? | In birds, it forms a structure for gas exchange (replaces the placenta). In mammals, it contributes to blood vessels in the umbilical cord |
| [Extraembryonic membranes] Identidy the location of the amnion, the chorion, the yolk sac and the allantois | See slide 23 |
| [Month 1, Week 1-Trimester 1] What happens to the zygote? After 6-7 days? Where does the blastula travel to? | It undergoes its first cleavage about 30 hrs after fertilization. After 6-7 days, it has differentiated into a blastocyst. The blastula travels to the endometrium in the process known as implantation |
| What is implantation? | A process where the blastula travels to the endometrium |
| [Month 1, Week 2-Trimester 1] What develops during that time? What stage of development occurs? | The developing chorion and the mother's endometrium engage to form the placenta. Gastrulation occurs in week 2. |
| [Month 1, Week 2-Trimester 1] What happens to the moms and the babys blood? | They come into proximity but do not mix; gases are exchanged. |
| What week do neurulation and organogenesis happen? | Neurulation in week 3 and organogenesis in week 4 |
| [Month 2-Trimester 1] What is established? What is the size/weight of embryo? What does the embry become? | Organogenesis continues: miniatuare limbs and major organs in the body are established. Embryo is 25 mm and 1g. At week 9, the embryo becomes a fetus. |
| [Month 3-Trimester 1] What system develops and what moves? | The nervous system develops and limbs start to move |
| [Trimester 2] What develops? | The basic body develops and the bones enlarge in the 4th month. Rapid fetal heartbeat |
| [Trimester 3] What is this period? What happens to the weight of fetus? What is formed? | It's a period of growth and organ maturation. The weight doubles several times. The major verbe tracts in the brain are formed. |
| [Trimester 3] What continues to develop months after the birth? | The brain continues to develop and produce neurons |
| During the birth, what does the mother's uterus releases? What does it do? | Releases prostaglandins. They begin uterine contractions. |
| What does the sensory feedback from uterus stimulates? | It stimulates oxytocin release from posterior pituitary |
| What further stimulates uterine contractions? | Oxytocin and prostaglandins |
| What expels the fetus? | Strong contractions (aided by the mother's voluntary pushing) |
| What continues after birth? | Uterine contractions continue to expel the placenta and associated membranes |
| What are the birth stages? | (1) The cervix relaxes causing it to dilate and thin out (2) Uterine contractions increase in strength and the enfant is delivered (3) The placenta is expelled |
Created by:
Malayka
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