Term
| What is the female germ or sex cells are produced in the ovaries? When mature, these are also called? |
|
Definition
-Oocyte
-secondary oocyte; mature oocyte |
|
|
Term
| What refers to the male germ cell produced in the testes (testicles)? Numerous of these (spermatozoa) are expelled from the male urethra during ejaculation. |
|
Definition
|
|
Term
| What cell results from the union of an oocyte and a sperm during fertilization? This or the embryo is the beginning of a new human being. |
|
Definition
|
|
Term
| What is difficult to determine exactly when fertilization (conception) occurs because the process cannot be observed in vivo (within the living body)? Physicians calculate the age of the embryo or fetus from the presumed first day of the last normal menstrual period. This is the gestational age, which is approximately 2 weeks longer than the fertilization age because the oocyte is not fertilized until approximately 2 weeks after the preceding menstruation. |
|
Definition
|
|
Term
| What is the series of mitotic cell divisions of the zygote that result in the formation of early embryonic cells, blastomeres? The size of the cleaving zygote remains unchanged because at each succeeding cleavage division, the blastomeres become smaller. |
|
Definition
|
|
Term
| What is the solid mass of 12 to approximately 32 blastomeres is formed by cleavage of a zygote? The blastomeres change their shape and tightly align themselves against each other to form a compact ball of cells. This phenomenon, compaction, is probably mediated by cell surface adhesion glycoproteins. This stage occurs 3 to 4 days after fertilization, just as the early embryo enters the uterus. |
|
Definition
|
|
Term
| What forms after 2 to 3 days, the morula enters the uterus from the uterine tube (fallopian tube)? Soon a fluid-filled cavity, the blastocystic cavity, develops inside it. This change converts the morula into a _________. Its centrally located cells, the inner cell mass or embryoblast, is the embryonic part of the embryo. |
|
Definition
|
|
Term
| What process during which the blastocyst attaches to the endometrium, the mucous membrane or lining of uterus, and subsequently embeds in it. The preimplantation period of embryonic development is the time between fertilization and the beginning of ____________, a period of approximately 6 days? |
|
Definition
|
|
Term
| What is a three-layered or trilaminar embryonic disc forms (third week). The three germ layers of this (ectoderm, mesoderm, and endoderm) subsequently differentiate into the tissues and organs of the embryo. |
|
Definition
|
|
Term
| What is the early embryo during the third and fourth weeks when the neural tube is developing from the neural plate? It is the first appearance of the nervous system and the next stage after the gastrula. |
|
Definition
|
|
Term
| What is the developing human during its early stages of development? The embryonic period extends to the end of the eighth week (56 days), by which time the beginnings of all major structures are present. The size of this is given as crown-rump length, which is measured from the vertex of the cranium (crown of head) to the rump (buttocks). |
|
Definition
|
|
Term
| What are these called...Early embryonic development is described in stages because of the variable period it takes for embryos to develop certain morphologic characteristics. Stage 1 begins at fertilization and embryonic development ends at stage 23, which occurs on day 56. The fetal period begins on day 57 and ends when the fetus is completely outside the mother. |
|
Definition
| Stages of Prenatal Development |
|
|
Term
| What is the embryo and its adnexa (L., appendages or adjunct parts) or associated membranes (i.e., the products of conception). This includes all structures that develop from the zygote, both embryonic and extraembryonic. Hence, it includes the embryo as well as the embryonic part of the placenta and its associated membranes: amnion, chorionic (gestational) sac, and umbilical vesicle or yolk sac. |
|
Definition
|
|
Term
| What is the beginning or first discernible indication of an organ or structure? The terms anlage and rudiment have similar meanings. This of the upper limb appears as a bud on day 26. |
|
Definition
|
|
Term
| What is called...After the embryonic period (8 weeks) and until birth, the developing human is called a _____. During the fetal period (ninth week to birth), differentiation and growth of the tissues and organs formed during the embryonic period occur. These developmental changes are not dramatic. |
|
Definition
|
|
