Stages of development: During the fetal stage, the brain develops and the body adds size and weight, until the fetus reaches full-term development. Throughout the fetal stage the brain continues to grow and develop, nearly doubling in size from weeks 16 to 28.
How long is the fetal stage?
The embryonic period (A) lasts 8 weeks and the fetal period (B) from the 9th week to the birth, i.e., 30 weeks. In obstetrics the pregnancy weeks (PW) are normally reckoned from the date of the Last Menstrual Period (LMP). This is a point in time that many women can easily remember.
What is the fetal stage characterized by?
The fetus is characterized by fused eyelids and distinct human somatic characteristics. The fetal period covers gestational weeks 11 to 26. During the fetal period, the total body weight (TBW) increases from approximately 5 to 500 g. Fetal period precedes embryonal period, during which a viable fetus is delivered.
What are the 3 stages of pregnancy?
Pregnancy the three trimesters
- First Trimester (0 to 13 Weeks) The first trimester is the most crucial to your baby’s development. …
- Second Trimester (14 to 26 Weeks) …
- Third Trimester (27 to 40 Weeks)
What are the 4 stages of embryonic development?
The Stages of Embryo Development
- Fertilization. Fertilization is the union of the female gamete (egg) and the male gamete (spermatozoa). …
- Blastocyst Development. …
- Blastocyst Implantation. …
- Embryo Development. …
- Fetal Development.
What are the 5 stages of conception?
The Journey from Egg to Embryo
- Conception: From Egg to Embryo. …
- Ovulation. …
- Moving Into the Fallopian Tube. …
- The Sperm’s Long Journey. …
- Fertilization: Sperm Penetrates Egg. …
- The Cells Start to Divide. …
- Implantation. …
- Pregnancy Hormones.
What is the pre-embryonic stage?
The first 2 weeks of prenatal development are referred to as the pre-embryonic stage. A developing human is referred to as an embryo during weeks 3–8, and a fetus from the ninth week of gestation until birth.
Where is Chorion located?
The chorion is the outermost fetal membrane around the embryo in mammals, birds and reptiles (amniotes). It develops from an outer fold on the surface of the yolk sac, which lies outside the zona pellucida (in mammals), known as the vitelline membrane in other animals.
What does teratogen mean?
A teratogen is any agent that causes an abnormality following fetal exposure during pregnancy. Teratogens are usually discovered after an increased prevalence of a particular birth defect. For example, in the early 1960’s, a drug known as thalidomide was used to treat morning sickness.
What is the embryo?
embryo, the early developmental stage of an animal while it is in the egg or within the uterus of the mother. In humans the term is applied to the unborn child until the end of the seventh week following conception; from the eighth week the unborn child is called a fetus.
What do you mean by Foetus?
A fetus or foetus (/ˈfiːtəs/; plural fetuses, feti, foetuses, or foeti) is the unborn offspring of an animal that develops from an embryo. … In human prenatal development, fetal development begins from the ninth week after fertilisation (or eleventh week gestational age) and continues until birth.
What is the embryo stage?
An embryo is the early stage of human development in which organs are critical body structures are formed. An embryo is termed a fetus beginning in the 11th week of pregnancy, which is the 9th week of development after fertilization of the egg. A zygote is a single-celled organism resulting from a fertilized egg.
What are the developmental stages?
There are three broad stages of development: early childhood, middle childhood, and adolescence.
What is fetal development?
Fetal development is the term used when talking about the procession of events that starts when sperm and egg meet and unfolds in an orderly progression to form a baby. For something that “simply happens” once a woman gets pregnant, it is amazingly complex—and a lot of fun to think about.
What is the correct sequence of prenatal stages of development?
There are three stages of prenatal development: germinal, embryonic, and fetal.
What is secondary yolk sac?
The secondary yolk sac is the definitive yolk sac. It gives rise to the first blood cells of the embryo and is highly vascularised. The secondary yolk sac ensures nutritional supply for the early embryo before the chorion is sufficiently developed to perform this function.
What is Embryology Anatomy?
Embryology is a branch of science that is related to the formation, growth, and development of embryo. It deals with the prenatal stage of development beginning from formation of gametes, fertilization, formation of zygote, development of embryo and fetus to the birth of a new individual.
What are the stages of pregnancy called?
Pregnancy is divided into three trimesters: First trimester – conception to 12 weeks. Second trimester – 12 to 24 weeks. Third trimester – 24 to 40 weeks.
How a woman gets pregnant by a man?
For a woman to become pregnant, a man’s sperm need to be placed into her vagina. This usually happens when a man’s erect penis is inserted into a woman’s vagina during sex and a fluid called semen is ejaculated from the man’s penis into her vagina. Sperm usually passes through the womb to reach the fallopian tube.
What is the order of conception?
To become pregnant, the following steps must occur: Sperm transport — The sperm must be deposited and transported to the site of fertilization. Egg transport — Ovulation must occur and the egg must be “picked up” by the tube. Fertilization and embryo development — Union between the sperm and egg must result.
What are the 6 stages of embryonic development in order?
The early stages of embryonic development, such as fertilization, cleavage, blastula formation, gastrulation, and neurulation, are crucial for ensuring the fitness of the organism. Fertilization is the process in which gametes (an egg and sperm) fuse to form a zygote.
How many stages are there in human development?
There are five significant phases in human growth and development, Infancy (neonate and up to one year age) Toddler ( one to five years of age) Childhood (three to eleven years old) – early childhood is from three to eight years old, and middle childhood is from nine to eleven years old.
What is the blastula stage of embryonic development?
An early stage of embryonic development in animals. It is produced by cleavage of a fertilized ovum and consists of a spherical layer of around 128 cells surrounding a central fluid-filled cavity called the blastocoel. The blastula follows the morula and precedes the gastrula in the developmental sequence.