prenatal development Flashcards
1
Q
1
A
- A figure of the tree of life, including major groups from the origins of life.
- Highlighted are the chordates, which include humans, as well as sea stars, fish, amphibians, mammals, birds, and reptiles.
- All living things have evolved from a common ancestor.
- Humans have spinal cords so that makes us part of a group of organisms called chordates, as they all share a feature of spinal cords.
- 97% of chordates have a bony sheath or a skeletal/spinal column.
2
Q
species biodiversity
A
- Shows that the number of chordate species is relatively very small compared to other taxonomic groups, such as beetles, fungi, bacteria, plants, and many others.
- Comprise only between about a tenth and a hundred of a percent of all living organisms.
- The processes of growth and embryological development share many similarities across species as diverse as humans, chickens, frogs and fish.
3
Q
2
A
A cladogram depicting the emergence of jaws, lungs, claws or nails, feathers, fur, and mammary glands different chordate taxa, from Hagfish to Chimpanzees.
4
Q
early scientific views on prenatal development
A
- Ca. 1590s - invention of the microscope, allowed us to see aspects of reality that was too small to see with the naked eye
- 1695 - Nicolaas Hartsoeker and the preformation theory of development - was looking at sperm and saw a tiny shape in it
- 19th century - improvements in optics had demonstrated that embryonic development did not involve simple processes of growth, but also substantial differentiation.
5
Q
Aristotle (384-322 B.C.)
A
- Scala naturae - great chain of being - species are fixed and arranged hierarchically.
- The idea that humans were at or near the top of an evolutionary ladder.
- This idea is widespread outside science, but not scientifically correct or accurate.
- Lower animals and higher animals
6
Q
recapitulation theory
A
- Haeckel reported substantial similarity in the forms of early embryos in a wide variety of species.
- However, in embryonic development different animals look quite different from one another.
7
Q
photographs vs drawings
A
- Comparison of photographs with drawings of various species’ embryos at the same stage of development, demonstrating that early embryos are very much more differentiated across species than previously believed.
- Bad news for the recapitulation hypothesis.
8
Q
stages of prenatal development
A
- The Germinal Period (from conception to implantation) - germinal period
- The period of the Embryo (implantation to - 2 months) - embryonic period - covers first trimester - covers tissue differentiation
3 . The period of the Fetus (2 months to birth) - fetal stage - covers growth
- The period of the Embryo (implantation to - 2 months) - embryonic period - covers first trimester - covers tissue differentiation
9
Q
germinal period
A
- Conception begins when a sperm cell fertilises the egg, which happens in the fallopian tube.
- The zygote (fertilised egg) moves down the fallopian tube and into the uterus.
- The first 4 days after conception, the zygote continues to multiply, forming this mass of cells known as a morally
10
Q
egg and ovary
A
- A drawing of the path of oocyte (egg) from the ovary through the fallopian tube to the uterus, where implantation takes place.
- Key events depicted include fertilisation, first cell division, formation of the blastocyst, terminating in the implantation of the zygote into the uterine wall on Day 8 or 9 post-conception.
11
Q
cell differentiation at 2 weeks
A
- Depicting the further division of the early embryo into three histologically distinct layers, the ectoderm, the mesoderm, and the endoderm.
- Implantation starts 10 days post conception, which lasts about 8 weeks.
- The blastisis differentiates into 3 distinct layers of different tissue types: ectoderm, mesoderm, endoderm.
- Each of these areas develop into different major organ systems:
- Ectoderm - nervous system, teeth, fingernails, toenails, and outer surface of the skin.
- Mesoderm - muscles, bones, circulatory system, inner surface of the skin
- Endoderm - gastrointestinal tracks, lungs, glands, organs concerned with digestion i.e., liver and pancreas
- Depicting the ultimate disposition of these three layers into the nervous system plus skin (ectoderm), the skeletal and circulatory systems (mesoderm), and the major organs of digestion and excretion (endoderm).
12
Q
period of the embryo at 3 weeks
A
- Post implantation, about a month after conception
- Eye is apparent, brain is beginning to bulge, heart and liver are forming, there are buds where the arms and legs will eventually be, the scaffolds for the individual vertebrae are apparent, but not yet bony and there is a rudimentary tail.
13
Q
period at the embryo at 7 weeks
A
- Have a much more developed embryo
- The fingers haven’t quite separated yet.
- Individual toes and fingers are now apparent, there is a developing bulge in the gut.
- Brain is growing rapidly
14
Q
period of the foetus at 2 months
A
- Limbs are now well-formed, with obvious digits, the brain has expanded substantially.
- Foetus will respond to stimulation
- This can be where the foetus becomes a psychological entity as it responds to stimulation.
15
Q
period of the foetus at 8 months
A
- Genitalia are now nearly fully formed and readily apparent.
- Their vestibular system is functioning
