this section covered the basic anatomy of the female reproductive system and follows the life of a oocyte from its creation until implantation in the uterus. the ovaries start with ~400,000 oocytes at puberty, out of which 400 are ovulated. the process begins in the ovaries, which are masses of mainly connective tissue, surrounded by a simple cuboidal germinal epithelium and tunica albuginea connective tissue layer. inside the ovaries are many "follicles" at varying stages of development. each follicle begins as a primordial follicle, which is an oocyte (~30um) surrounded by simple cuboidal follicular cells. the next stage is a primary follicle, where a slightly larger oocyte (50um) is surrounded by a cuboidal follicular layer that begins to stratify, and a light pink zona pelucida appears around the oocyte. the next stage is a secondary follicle, with a larger oocyte (~100um), the beginning of the development of an "antrum", which is a space in the follicle that is filled with follicular liquor, and the emergence of the theca, which is a double layered perimeter in the follicular layer that has two parts: the theca interna, which secretes estrogen, and the theca extra, which is made up of connective tissue and smooth muscle. the next and final phase is the tertiary, or graafian, or mature follicle, in which the larger oocyte is surrounded by a nest of follicular cells, the antrum makes up the bulk of the follicle and nearly pinches off the oocyte, and the entire follicular diameter approaches 10-12 mm.
at this point the tertiary follicle releases its oocyte from the ovaries (the released oocyte is now an ovum) and the ovum begins to travel down the oviduct. the oviduct contains many epithelial folds of ciliated simple columnar mucosa, with a muscularis composed of an inner circular layer and outer longitudinal layer, and an outer serosa layer. around the 2nd day after the release of the ovum, it can be fertilized in the upper 1/3 of the oviduct, called the ampula. it then travels down to the uterus for implantation, which generally occurs ~7 days later. the uterus has three layers: endometrium, myometrium, and perimetrium. the myometrium is made of smooth muscle and perimetrium is the serosa; neither of these layers change much during the menstrual cycle. contrast this with the endometrium, which undergoes dramatic growth and breakdown during the menstrual cycle, beginning with the menstrual phase, then the follicular / proliferative phase, then the progestational or secretory phase, then the gravis phase. the endometrium is broken down into two functional layers: the stratum basale, which stays the same during the cycle, and the stratum functionale, which is the layer that builds up and degenerates. while the follicle is developing in the ovaries the endometrium is building up a highly vascularized tissue in preparation for implantation. if implantation does not occur, then the stratum functionale breaks down during the "menstrual phase".
below the uterus is the cervix, which is the opening to the vagina. the transition from the cervix to the vagina happens dramatically, changing swiftly from the simple columnar epithelium in the cervix to the stratified squamous of the vagina. the vagina has 3 layers, the top layer being mostly parakeratinized stratified squamous, with a chaotically organized muscularis underneath, and an adventitia layer beyond.
one other note: the corpeus luteum is the remnant of the tertiary follicle after the ovum is released from the ovaries. if pregnancy does occur, the corpeus luteum continues to enlarge in the ovaries and secrete estrogen (which helps the development and growth of sex organs) and progesterone (which prepares the uterus for pregnancy and the mammary glands for lactation) for ~10 weeks or until the placenta takes over. if pregnancy does not occur, then the corpeus luteum breaks down in 12-14 days and forms a whitish mass called the corpeus albicans.
questions
1. how does oogenesis affect production of hormones?
2. describe the physical makeup of the ovary.
3. how many oocytes do the ovaries start with at puberty and about how many are ovulated in total?
4. describe the primordial follicle.
5. what is the development of the primordial follicle mediated by?
6. what are atretic follicles?
7. describe the primary follicle.
8. describe the secondary follicle.
9. what is follicular liquor and what does it develop into?
10. what is theca and what are the two layers?
11. describe the tertiary follicle.
12. what is the corpeus luteum and what does it do?
13. what is the name for the structure that the corpeus luteum degenerates into?
14. what are the physical characteristics of the oviduct?
15. what are the three layers of the uterus?
16. what are the physical characteristics of the endometrium?
17. what are the phases of the menstrual cycle?
18. describe the timing of fertilization and implantation after the ovum is released from the ovaries.
19. what is histologically unique about the transition from the cervix to the vagina?
20. what are the layers of the vagina?
answers
1. oogenesis produces estrogen to promote growth and development of sex organs, progesterone to prepare uterus for pregnancy and mammary glands for lactation.
2. mostly connective tissue with follicles in varying stages of development. covered by germinal epithelium (simple cuboidal) and the tunica albuginea (CT) layer.
3. 400,000 and 400
4. an oocyte enclosed in a squamous layer of follicular cells, about 30um
5. FSH (follicle stimulating hormone)
6. follicles in the ovaries that have degenerated
7. a larger oocyte (50um) surrounded by cuboidal follicular cells, with a pink zona pellucida developing around the oocyte.
8. an even larger oocyte (100um) surrounded by stratified cuboidal follicular cells, up to 1-2mm total diameter
9. the secretions from follicular cells in a secondary follicle that develop into an antrum.
10. theca is a double layered perimeter that appears in the secondary follicle. the theca interna has estrogen secreting cells and the theca externa is CT and smooth muscle.
11. the tertiary, or mature, or graafian follicle is up to 10mm in total diameter with a huge antrum and the oocyte surrounded by a nest of follicular cells.
12. the corpeus luteum is a temporary structure that is formed from the remains of the tertiary follicle which rapidly proliferates to secrete progesterone and estrogen. if pregnancy occurs, the corpeus luteum continues to enlarge and secretes estrogen and progesterone until the placenta takes over. if pregnancy does not occur, then the corpeus luteum degenerates in 12-14 days.
13. corpus albicans
14. has a mucosa, muscularis, and serosa layers. mucosa has many folds with simple columnar epithelium, with cilia, some secretory cells (to provide nutrients for ova) and lamina propria. muscularis has inner circular and outer longitudinal smooth muscle.
15. endometrium, myometrium (muscularis), perimetrium (serosa).
16. simple columnar epithelium, simple tubular uterine glands, stratum basalis/stratumfunctionalis.
17. the menstrual phase, the follicular or proliferative phase, the progestational or secretory phase, and the gravid phase.
18. fertilization occurs in the ampula (upper 1/3) of the oviduct ~2 days after the ovum is released from the ovaries, and implantation generally happens ~7 days later.
19. the transition from the cervix to the vagina occurs dramatically, changing from simple columnar to stratified squamous epithelium within a single layer of cells.
20. stratified squamous epithelium (mostly parakeratinized), lamina propria with elastic fibers, muscularis (poorly organized), adventitia.
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