Major differences between oogenesis and gametogenesis
| Oogenesis | Spermatogenesis | |
|---|---|---|
| Definition | Production of oocytes from oogonia | Production of spermatozoa from spermatogonia |
| Location of stages | 2 stages. Meiosis I in the Ova and Meiosis II completes in the fallopian tube | Meiosis I and Meiosis II all occur in the testes |
| Continuity | Early oogenesis occurs during the fetal period. The remaining stages occur from puberty to menopause | A continuous process from puberty to death |
| Length of growth phase | Prolonged | Shortened |
| Polar body | Produced after Meiosis I | No polar bodies are formed |
| Motility of the gametes | Produces non-motile gametes | Produces motile gametes |
Distinguish between mitosis and meiosis
| Mitosis | Meiosis | |
|---|---|---|
| Number of divisions | One | Two |
| Independent assortment | Does not occur | Occurs in metaphase I |
| Synapsis | Does not occur | Occurs forming bivalents |
| Crossing over | Does not occur | Occurs in prophase I |
| Outcome | Two daughter cells | Four daughter cells |
| Cell ploidy | Diploid cells | Haploid cells |
| Utility | Division of body cells | Formation of gametes |
| Genetics of daughter cells | Identical to parent cells | Variation exists |
Outline the stages/ phases of mitosis and state key events of each stage
- Prophase: Chromosomes condense, Spindle fibers form
- Metaphase: Chromosomes align at the equatorial or metaphase plate
- Anaphase: Sister chromatids are cleaved to form 2 identical daughter chromosomes
- Telophase: The nuclear envelope forms around the chromosomes
- Cytokinesis: The cell divides into 2 halves
Name the hormones involved in the regulation of the uterine and ovarian cycles and state their respective roles
- Gonadotropin-releasing hormone (GnRH): Released from the hypothalamus to stimulate the anterior pituitary to produce FSH and LH
- Follicle Stimulating Hormone (FSH): Stimulates the granulosa cells and recruits a group of maturing follicles in the ovary. Follicular cells produce estradiol and Inhibin B
- Luteinizing hormone (LH): Stimulates the theca cells to produce progesterone and androstenedione (androgen), Surge induces ovulation, Fall in LH after ovulation causes the corpus luteum to degenerate
- Estradiol: negative feedback to the pituitary gland to inhibit FSH release, Causes proliferation of the endometrium
- Inhibin B: Negative feedback to the pituitary gland to inhibit FSH release
- Progesterone: Causes differentiation of the endometrium in preparation for implantation
Distinguish between the following terms: Spermatocytogenesis, Spermiogenesis, Spermiation
- Spermatocytogenesis: Spermatogonia form into spermatozoa
- Spermiogenesis: Spermatids mature into spermatozoa
- Spermiation: The release of mature spermatids from Sertoli cells into the seminiferous tubules, prior to their passage into the epididymis
Describe the phases of the menstrual cycle, respective changes in the endometrium, and the underlying hormonal basis
- Phases in the ovarian cycle
- Follicular phase: FSH causes maturation of follicles
- Ovulation: LH surge causes ovulation
- Luteal phase: The remaining dormant follicle transforms into the corpus luteum under the influence of FSH and LH. The corpus luteum secretes progesterone
- Phases in the Uterine cycle
- Proliferative phase: Estrogen from granulosa cells of the mature follicle causes proliferation of the endometrium
- Secretory phase: Progesterone from the corpus luteum causes differentiation of the endometrium. Glycogen, lipids, and proteins are secreted into the uterus and the cervical mucus thickens:
- Menstrual phase: Falling Estrogen and progesterone levels and increased prostaglandin production cause shedding of the uterine mucosa
Regarding fertilization describe the following: Prerequisites of fertilization, Phases of fertilization, The immediate results of fertilization
- Prerequisites of fertilization: Capacitation, Acrosomal reaction, Zona reaction
- Phases of fertilization: Penetration of the corona radiata, Penetration of the zona pellucida, Fusion of the oocyte and sperm membrane
- Immediate results of fertilization: Restoration of diploid number of chromosomes, Sex determination, Initiation of cleavage (Mitosis), Metabolic activation of the cell
