Lecture Wednesday September 12: Female Reproductive Histology

A. Follicular Development in the Ovary
- Stimulated by FSH (follicle stimulating hormone) from the pituitary.

1. Primordial Follicle: primary oocyte (arrested in prophase of Meiosis I) and a single layer of squamous follicular cells.

2. Unilaminar Primary Follicle: primary oocyte (arrested in prophase of Meiosis I) and a single layer of cuboidal follicular cells.

3. Multilaminar Primary Follicle: primary oocyte (arrested in prophase of Meiosis I) surrounded by multiple layers of cuboidal follicular cells now termed Granulosa cells and a layer of spindle-shaped Thecal cells.

4. Secondary/antral follicle: primary oocyte (arrested in prophase of Meiosis I) surrounded by Granulosa cells that begin to form small antral spaces between the cells through the secretion of follicular fluid. Thecal cells form two layers, theca interna and externa.

5. Mature/Graffian follicle: Antral spaces coalesce into a single large antral cavity. Secondary oocyte (arrested in metaphase of Meiosis II) surrounded by a layer of Granulosa cells called Corona Radiata.

Theca interna > secrete androstenedione > taken up by Granulosa cells > aromatase enzyme converts to estradiol > circulates systemically > development of the endometrium of the uterus and other effects.




*BE ABLE TO IDENTIFY THESE DIFFERENT STAGES OF FOLLICLE DEVELOPMENT IN A HISTOLOGICAL SECTION OF THE OVARY*

B. Ovulation
- Stimulated by a surge in LH (leutinizing hormone) by the pituitary gland (due to rising estrogen levels).

1. Primary oocyte completes Meiosis I and begins Meiosis II (arrests in metaphase of Meiosis II). Now referred to as a Secondary Oocyte (haploid).

2. If fertilization occurs, secondary Oocyte completes Meiosis II.

3. Following ovulation the remaining granulosa cells and theca interna of Graffian follicle reorganize to form Corpus Luteum. Two cell types;
- Granulosa Lutein cells secrete estrogen
- Theca Lutein cells secrete androstenedione and progesterone.

4. Corpus Luteum secretes progesterone for 10-12 days. Without further LH or a pregnancy the corpus luteum regresses and forms the corpus albicans and the uterine endometrium is shed.

5. If pregnancy occurs > HCG produced by placenta > maintains corpus Luteum for 4-5 months. Placenta eventually produces progesterone and estrogen to maintain the uterine mucosa.




C. Uterus
- Endometrium: a mucosa lined by simple columnar epithelium (functional layer and basal layer)
- Myometrium: a thick highly vascularized layer of smooth muscle

Structural changes occurring during the Menstrual cycle:
1. Proliferation phase: proliferation of basal layer to replace functional layer lost during menstruation.

2. Secretory phase: progesterone stimulates growth and secretion of the uterine glands, edema of stroma.

3. Menstrual phase: contraction of spiral arteries, tissue ischemia, shedding of functional layer.

D. Cervix
- Transformation zone: location in the ectocervix where the epithelium changes from simple columnar typical of the uterus to stratified squamous typical of the vagina.

* This is the site particularly susceptible to infection by papilloma virus and the development of cervical cancers.












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