| A | B |
|---|
| XX | Female |
| XY | Male |
| Pituitary | Secretes hormones that affect all other endocrine glands. |
| Adrenal | Secretes adrenaline. |
| Pineal | May regulate the onset of puberty. |
| Thyroid | Secretes thyroxine which regulates metabolism. |
| Pancreas | Releases insulin to decrease blood sugar levels; releases glucagon to increase blood sugar levels. |
| Thymus | Helps establish immune system in juveniles. |
| Ovulation | The release of an egg from a follicle. |
| Menstruation | The breakdown and release of the endometrial lining. |
| Fertilization | Occurs when one sperm penetrates one egg. |
| Embryo | Eight weeks after fertilization. |
| Identical twins | Formed from one fertilized egg that splits into two. |
| Fraternal Twins | Formed from two separate eggs being fertilized by different sperm. |
