| 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 |
| embyro | 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 |
