BioScience Dictionary

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Ot.

Found Ovum 32 times.

Displaying results 1 to 10.

1. Acrosin
An enzyme found in sperm cells which is thought to help the sperm penetrate the tough outer surface of the ovum .

2. Beta human chorionic gonadotropin (beta hCG)
This is a glycoprotein composed of two subunits and secreted by the placenta. It is detectable 1 day after implantation of the a fertilized ovum and peaks at 60 to 90 days of gestation. Normal level is less than 5 mIU/mL; 20-100 IU/L 1 to 2 weeks after conception and 50,000 IU/L about 65 days after pregnancy then declines. In molar pregnancy, it can be extremely high initially, (over 100,000 IU/L) but declines with time. Normal Ranges: (in IU/L): non-pregnant: 0 - 5, possibly pregnant: 5 - 25 During Gestation: 0 - 1 wk: 5 - 50, 1 - 2 wks: 50 - 500, 2 - 3 wks: 100 - 1,000, 3 - 4 wks: 500 - 6,000, 1 - 3 months: 5,000 - 200,000, 2nd trimester: 3,000 - 50,000, 3 rd trimester: 1,000 - 50,000 * In the first three weeks of a normal pregnancy, the serum beta hCG approximately doubles every two days. The doubling time of hCG is considered a more reliable method of evaluating an early pregnancy than a single result.

3. Blastocyst
The developmental stage of the fertilized ovum by the time it is ready to implant; formed from the morula and consists of an inner cell mass, an internal cavity, and an outer layer of cells (the trophoblast ).

4. Corpus luteum (yellow body)
A temporary endocrine gland which forms from the remains of the ovarian follicle after an ovum (egg) has been released, rupturing the follicle in the process. The gland can secrete both progesterone and estrogen , two female hormone s which play a role during pregnancy. The gland disappears if pregnancy does not occur.

5. Decidua
The decidua is the changed endometrium (the lining of the uterus) after the blastocyst (fertilized ovum after 4 - 9 days of development) is implanted onto the endometrium. At this stage, there are 3 regions of decidua: decidua basalis: between the blastocyst and the uterine muscular wall, decidua capsularis: covers the blastocyst; decidua parietalis: the rest of the lining of the uterus.

6. Egg coat
A layer of glycoprotein s and other stuff which surrounds an egg (ovum) , just outside of the egg's cell membrane . The coat protects the egg, and for organisms which practice external fertilization (fertilization outside of the parents' bodies) it can help prevent the sperm of other species from entering the egg. For the eggs of mammals, the egg coat is called the zona pellucida and for sea urchins (a popular study organism for developmental biologist s) it is called the vitelline layer.

7. Egg donation
Donation of an ovum by one woman to another who attempts to become pregnant by in vitro fertilization.

8. Embryology
The study of the embryo and its development from a one-celled zygote (fertilized ovum ) to the establishment of form and shape (at which point, if it is an animal, it becomes a fetus ). A subfield of developmental biology .

9. Fallopian tubes
Ducts that pick up the ovum (egg) from the ovary ; fertilization normally occurs in one or both of these ducts.

10. Fertilization
The fusion of two gametes (sperm and ovum) to produce a zygote that develops into a new individual with a genetic heritage derived from both parents. Strictly speaking, fertilization can be divided into the fusion of the cells (plasmogamy) and the fusion of nuclei (karyogamy).

View web definitions »

Learn more about Ovum »