Histology of Female Reproductive System I Flashcards
What are the general functions of the ovary?
Ovary produces eggs (oocytes) and hormones (estrogen and progesterone)
What are the microscopic features of the ovary?
Germinal Epithelium - simple squamous or cuboidal epithelium
Tunica albuginea - dense irregular collagenous CT, must be thin enough for oocyte to rupture during ovulation
Cortical region - CT stroma with smooth muscle fibers and ovarian follicles
Medullary region - core of ovary, consists of CT stroma, blood vessels, lymph vessels, and nerves
Where do most ovarian cancers arise from?
Germinal Epithelium of ovary
Where do oocytes mature?
In cortical region of ovary
Describe the process of oogenesis
Total number of oocytes in ovaries is determined before birth
At birth, ovaries contain about 700,000 immature oocytes
Thousands degenerate and reduced to 200,000 by the time of menarche
Immature oocytes are stores in ovaries during reproductive years and one oocyte is released from ovary each month
What is haploid?
1n = 23 chromosomes
What is diploid?
2n = 46 chromosomes
How many chromosomes do sex cells and somatic cells contain?
Sex cells contain 23 chromosomes and are haploid
Somatic cells contain 46 chromosomes and are diploid
What is DNA content described as?
1d = amount of DNA in 23 single chromatid chromosomes
2d = amount of DNA in 23 double chromatid chromosomes or the amount of DNA n 46 single chromatid chromosomes
4d = amount of DNA in 46 double chromatid chromosomes
What is meiosis?
Genetic division (reduction) and crossing over (chromosomes from both parents are combined in offspring gametes) that happens only in gametes
During oogenesis 2 sequential meiotic cell divisions occur to produce a single mature ovum and 2 polar bodies
What is the process of meiosis prenatally?
Prior to Meiosis I, chromosomes in germ cells duplicates - 46 single chromatid chromosomes (2n, 2d) duplicate during S phase of interphase to form 46 double chromatid chromosomes (2n, 4d)
Meiosis I begins prenatally - at onset of Meiosis I, there are 2n, 4d chromosomes in germ cell
Meiosis I stops at Prophase and is suspended there until just before ovulation
What is a primordial germ cell called when it enter Meiosis I and what is it at Prophase I?
Referred to as a primary oocyte
At Prophase I, it is still 2n, 4d
What is the process of Meiosis at birth?
At birth, primary oocytes are only cells within follicle of ovarian cortex stuck in Prophase I
These cells remain dormant and only continue through meiosis when oocyte matures and is ovulated
What occurs in Meiosis post-puberty and pre-ovulation?
Oocyte progresses from Prophase I through Metaphase I, Anaphase I, Telophase I, and completing Meiosis I
During Anaphase I, the homologous, double chromatid chromosome pairs separate and each cell inherits half of the chromosomes (23 double chromatid chromosomes)
Cell becomes secondary oocyte 23 (1n, 2d)
Meiosis II begins right after Meiosis I and will stop and be suspended at Metaphase II in a mature (Graafian) follicle
What occurs at ovulation with the secondary oocyte?
Secondary oocyte is in Metaphase II and is released into the uterine tube hovering near the ovary
Unfertilized eggs DO NOT
Complete meiosis
What occurs at fertilization to the oocyte?
Meiosis II will complete and give rise to a mature ovum (1n, 1d) ONLY if secondary oocyte is fertilized by sperm
During Meiosis II, each of the 23 (double chromatid) chromosomes split and each resultant gamete inherits 23 (single chromatid) chromosomes
What are the chromosomes throughout oogenesis?
Prenatally: 46 (2n, 2d)
Duplicate during S-phase to become 46 (2n, 4d)
Suspended in Prophase I as 46 (2n, 4d)
Resumes prior to ovulation and post-puberty to Finish Meiosis I as 23 (1n, 2d) secondary oocyte
When fertilization occurs, goes through Meiosis II and becomes mature ovum 23 (1n, 1d)
When does follicle development occur?
Begins at puberty and continues throughout the reproductive years (puberty through menopause)
What do ovarian follicles consist of?
Ovarian follicles consist of an oocyte surrounded by layer or layers of epithelial follicular or granulosa cells
How do follicles undergo maturation?
Every month, several follicles undergo maturation in response to follicle stimulating hormone (FSH) released by the basophils (gonadotropes) in anterior lobe of the pituitary gland
Usually only one follicle becomes fully mature and the enclosed secondary oocyte is ovulated
What is the oocyte developmental stage for the primordial follicle, primary follicles, and secondary follicle?
Primary oocyte in prophase I
What is the oocyte developmental stage for the mature (Graafian) follicle?
Secondary oocyte in Metaphase II at ovulation
What is the order of development of the follicles?
Primordial Follicle
Unilaminar primary follicle
Multilaminar primary follicle
Secondary (antral) follicle
Mature (Graafian) follicle
What are the histological characteristics of the primordial follicle?
Contains a primary oocyte in prophase I
Forms prenatally
Present in ovary at birth until menopause
Dormant, most immature follicle in ovary
Simple squamous follicle cells with desmosomes
Basal lamina
What are the histological characteristics of the unilaminar primary follicle?
Primary oocyte in prophase I produces activin which stimulates stratification of the follicle cells
Zona pellucida - acellular gel-like membrane begins to forms, consists of GAGs and glycoproteins that are secreted by oocyte
Simple cuboidal follicle cells
Basal lamina
What are the histological characteristics of the multilaminar primary follicle?
Primary oocyte in Prophase I
Zona pellucida present
Mitosis - formation of stratified cuboidal granulosa cells (avascular) - follicular cells now called granulosa cells
Gap junctions between granulosa cells
Granulosa cells have filopodia, oocytes have microvilli - filopodia and microvilli perforate the zona pellucida
Basal lamina present
Theca folliculi encapsulate the follicle and theca interna begin to form
Theca interna are cellular steroid-secreting cells with SER, mitochondria, and lipid droplets. Richly vascularized
What cells have LH receptors?
Steroid secreting cells in the theca interna of multilaminar primary follicles
LH stimulates cells to produce androgens which is converted to estradiol by granulosa cells
What are the histological characteristics of the secondary (antral) follicle?
Primary oocyte in prophase I
Zona pellucida present
Stratified granulosa cells proliferate and secrete liquor folliculi
Fluid filled antral cavities form between granulosa cells
Cumulus oophorus - mound of granulosa cells contains the oocyte and the granulosa cells around the oocyte are the corona radiata
Basal lamina
Theca interna and theca externa (fibrous CT and smooth muscle)
What are the histological characteristics of the mature (Graafian) follicle?
Primary oocyte (prophase I) which progresses to secondary oocyte (Metaphase II) just prior to ovulation
Zona pellucida
Corona radiata
Membrane granulosa, cumulus oophorus, and corona radiata all have granulosa cells
Liquor folliculi
Antrum
Theca interna (LH stimulates cells here to release androgens which are converted to estrogens)
Theca externa
What is ovulation?
Release of secondary oocyte from a mature (Graafian) follicle
What is the process of ovulation?
- FSH and LH spike and released by basophils in anterior lobe of pituitary around day 14
- Mature follicle protrudes from ovarian surface
- Meiosis I resumes in response to LH surge
- Primary oocyte in prophase I completes meiosis I to become secondary oocyte
- Meiosis II starts and secondary oocyte remains in metaphase II
- Granulosa cells sourround the oocyte and it detaches from follicle
- Oocyte surrounded by zona pellucida and granulosa cells, float in liquor folliculi
- Proteases break down cortical stromal tissue covering the follicle
- Granulosa wall ruptures, releasing the oocyte and liquor folliculi
- Secondary oocyte in Metaphase II, covered by zona pellucida and granulosa cells is released into the hovering open end of fallopian tube
What occurs following ovulation?
Granulosa and thecal cells of the collapsed mature follicle left behind remain embedded within the ovarian cortex and are transformed into a temporary endocrine gland called the corpus luteum
CL maintained by FSH and LH
What do granulosa cells differentiate into?
Granulosa lutein cells
What do theca interna cells differentiate into?
Theca lutein cells
What do granulosa lutein cells and theca lutein cells produce?
Estrogens and PG
What do estrogens and PG stimulate?
Stimulate the maturation and glandular activity of the endometrum, preparing the uterine lining for possible implantation of the bastocyst
What is the corpus albicans?
Dense CT scar formed after the corpus luteum regresses following menstruation or pregnancy
What occurs if the ovulated oocyte is not fertilized or the patient is not pregnant?
If ovulated oocyte is not fertilized and implanted, pregnancy does not occur
Granulosa and thecal cells left in ovarian cortex are referred to as the CL of menstruation
CL continues to produce estrogen and PG for only about 14 days to maintain endometrial lining but degenerates to become a corpus albicans
Drop in estrogen and PG levels cause endometrium to shred and menstrual bleeding to occur
What occurs if the patient is pregnant and the ovulated oocyte is fertilized?
Granulosa and thecal cells remaining in ovarian cortex become the CL of pregnancy
During pregnancy, the CL is maintained by the hCG released by syncytiotrophoblast
CL of pregnancy continues to produce estrogen and PG to maintain the endometrium throughout pregnancy
What is PCOS?
Polycystic Ovarian Syndrome
Bilateral, both ovaries affected
Oocytes mature and ready for release like normal
Condition is exacerbated by thick tunica albuginea that prevents release of the oocyte from follicle and ovary
Result is many fluid-filled follicular cysts and atrophic secondary follicles that remain in ovary and oocytes eventually degenerate
What will PCOS present with?
Patient has anovulatory menstrual cycles - no ovulation results in infetility
No ovulation means the granulosa cells of the Graafian follicle do not transform into the CL to produce PG
Uterine endometrium still remains since it is stimulated by estrogen
How is PCOS treated?
Patient must be treated with hormone therapy to establish normal estrogen/progesterone ratio
Sometimes surgical treament
If patient as PCOS and oligomenorrhea (scanty menstruation), what is it?
Disease called Stein-Leventhal Syndrome
What is the possible cause of PCOS?
Not clear
May be flaw in regulation of androgen biosynthesis, resulting in excessive androgen production. These androgens are converted to estrogens
May be genetic basis for abnormally thick tunica albuginea
