Development Flashcards
Define zygote
A fertilized egg. A diploid cell resulting from the fertilization of haploid gametes from the male and female lines
Define gestation
In human development, the period required for embryonic and fetal development in utero; pregnancy
What is the difference between the gestational calendar and gestation
the gestational calendar is usually 40 weeks. it begins on the first day of the mothers last menstrual period
Gestation only lasts 38 weeks, 2 weeks after ovulation occurs
Explain the timing of the embryonic period
Embryonic period is the first 8 weeks following fertilization
Explain the timing of fetal periods
Fetal period extends from the end of the embryonic period to birth
Describe fertilization
Fertilization is when a sperm combines with an oocyte
Where does fertilization occur?
Fertilization occurs in the ampulla of the uterine (fallopian) tube and fuse to form a single cell called a zygote
What is a haploid cell?
A haploid has half of the usual genetic material. ex: sperm or oocyte
What is a diploid cell?
A diploid has a complete set of chromosomes. Half from the mother and half from the father
How many days can sperm survive in the uterine tube?
Sperm can survive in the fallopian tube for up to 5 days
Describe capacitation
Priming of the sperm.
The process that occurs in the female reproductive tract where sperm are prepared for fertilization.
What does capacitation lead to?
Capacitation leads to increased motility of the sperm and changes in their outer membrane that improve their ability to release enzymes capable of digesting an oocyte’s outer layers
Describe the basics of sperm and egg fusion
After capacitation, the sperm releases enzymes allowing the sperm to penetrate the egg’s protective layers and fuse with the egg’s membrane. The sperm’s pronucleus then enters the egg, and the haploid nuclei of both fuse, completing fertilization. The result is a diploid zygote
Explain fraternal twins
If two eggs are released during ovulation and both are fertilized it leads to two separate zygotes
Explain identical twins
If after fertilization of a single egg, a cell can split away from the developing embryo, this leads to 2 separate but genetically identical monozygotic or identical twins
Describe the basics of in vitro fertilization
- Eggs are collected after ovulation or directly from the follicles. Sperm are collected and concentrated
- The eggs and sperm are mixed in a Petri dish, allowing for fertilization
- The fertilized zygote is then removed from the Petri dish for implantation
- The zygote is then surgically implanted into the endometrium of the uterus.
After successful implantation, the zygote should develop normally, as if it had been fertilized in the females oviducts
Describe morula
The solid ball of cells that continues to move through the fallopian tube
5 days after fertilization, the morula reaches the uterus and begins to form a hollow space at its center
Describe blastocyst
After the morula reaches the uterus the conceptus is called a blastocyst
The cells of the blastocyst can be divided into the cells that form the ball trophoblast cells
Define gastrulation
The cells of the epiblast become the ectoderm. This process of forming a three layered disc is referred to as gastrulation and is technically the beginning of the embryonic period and the beginning of organogenesis
Define organogenesis
The process where the 3 germ layers (endoderm, mesoderm, ectoderm) in a developing embryo differentiate and develop into the internal organs and tissues of an organism
State the function of the placenta
Provides nutrients and oxygen, while eliminating wastes for the fetus
Describe hCG
- Human Chorionic Gonadotropin
- Secreted by the trophoblast causes the corpus luteum to survive and continue producing progesterone and estrogens
-hCG also stimulates the male fetal gonads to secrete testosterone for the development of the male reproductive system
Describe the positive feedback loop of childbirth
As labor nears, oxytocin releases which begins to stimulate contractions
This causes the baby to push down, stretching the cervix.
The stretching of the cervix signals the release of more oxytocin which triggers more powerful contraction, and the cycle continues until birth
List the 3 stages of childbirth
- cervical dilation
- expulsion of the newborn
- afterbirth
Describe the milk let-down reflex
In response to the oxytocin secretion in birth, the alveoli and ducts contract causing milk to drain into the mammary ducts which is suckled by the infant. Another example of a positive feedback loop
Do male or female provide the chromosome that determines the genetic sex of the baby?
The male has XY chromosomes
Females have XX chromosomes.
The female will always pass on the X and the male will determine the second chromosome (X or Y) determining the sex
Describe a Punnett square
A diagram used to illustrate the possible combinations of genes in an offspring if we know the genotype of the parents
Describe autosomal dominant
Pattern of dominant inheritance that corresponds to a gene on one of the 22 autosomal chromosomes
Describe autosomal recessive
Pattern of recessive inheritance that corresponds to a gene on one of the 22 autosomal chromosomes
An autosomal recessive trait will only be expressed if 2 recessive alleles are inherited
Define genotype
The complete genetic makeup of an individual
Define phenotype
Physical or biochemical manifestation of the genotype; expression of the alleles
