Histology of Female Reproductive System I

Question 1

What are the general functions of the ovary?

Answer 1

Ovary produces eggs (oocytes) and hormones (estrogen and progesterone)

Question 2

What are the microscopic features of the ovary?

Answer 2

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

Question 3

Where do most ovarian cancers arise from?

Answer 3

Germinal Epithelium of ovary

Question 4

Where do oocytes mature?

Answer 4

In cortical region of ovary

Question 5

Describe the process of oogenesis

Answer 5

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

Question 6

What is haploid?

Answer 6

1n = 23 chromosomes

Question 7

What is diploid?

Answer 7

2n = 46 chromosomes

Question 8

How many chromosomes do sex cells and somatic cells contain?

Answer 8

Sex cells contain 23 chromosomes and are haploid

Somatic cells contain 46 chromosomes and are diploid

Question 9

What is DNA content described as?

Answer 9

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

Question 10

What is meiosis?

Answer 10

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

Question 11

What is the process of meiosis prenatally?

Answer 11

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

Question 12

What is a primordial germ cell called when it enter Meiosis I and what is it at Prophase I?

Answer 12

Referred to as a primary oocyte

At Prophase I, it is still 2n, 4d

Question 13

What is the process of Meiosis at birth?

Answer 13

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

Question 14

What occurs in Meiosis post-puberty and pre-ovulation?

Answer 14

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

Question 15

What occurs at ovulation with the secondary oocyte?

Answer 15

Secondary oocyte is in Metaphase II and is released into the uterine tube hovering near the ovary

Question 16

Unfertilized eggs DO NOT

Answer 16

Complete meiosis

Question 17

What occurs at fertilization to the oocyte?

Answer 17

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

Question 18

What are the chromosomes throughout oogenesis?

Answer 18

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)

Question 19

When does follicle development occur?

Answer 19

Begins at puberty and continues throughout the reproductive years (puberty through menopause)

Question 20

What do ovarian follicles consist of?

Answer 20

Ovarian follicles consist of an oocyte surrounded by layer or layers of epithelial follicular or granulosa cells

Question 21

How do follicles undergo maturation?

Answer 21

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

Question 22

What is the oocyte developmental stage for the primordial follicle, primary follicles, and secondary follicle?

Answer 22

Primary oocyte in prophase I

Question 23

What is the oocyte developmental stage for the mature (Graafian) follicle?

Answer 23

Secondary oocyte in Metaphase II at ovulation

Question 24

What is the order of development of the follicles?

Answer 24

Primordial Follicle

Unilaminar primary follicle

Multilaminar primary follicle

Secondary (antral) follicle

Mature (Graafian) follicle

Question 25

What are the histological characteristics of the primordial follicle?

Answer 25

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

Question 26

What are the histological characteristics of the unilaminar primary follicle?

Answer 26

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

Question 27

What are the histological characteristics of the multilaminar primary follicle?

Answer 27

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

Question 28

What cells have LH receptors?

Answer 28

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

Question 29

What are the histological characteristics of the secondary (antral) follicle?

Answer 29

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)

Question 30

What are the histological characteristics of the mature (Graafian) follicle?

Answer 30

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

Question 31

What is ovulation?

Answer 31

Release of secondary oocyte from a mature (Graafian) follicle

Question 32

What is the process of ovulation?

Answer 32

1. FSH and LH spike and released by basophils in anterior lobe of pituitary around day 14
2. Mature follicle protrudes from ovarian surface
3. Meiosis I resumes in response to LH surge
4. Primary oocyte in prophase I completes meiosis I to become secondary oocyte
5. Meiosis II starts and secondary oocyte remains in metaphase II
6. Granulosa cells sourround the oocyte and it detaches from follicle
7. Oocyte surrounded by zona pellucida and granulosa cells, float in liquor folliculi
8. Proteases break down cortical stromal tissue covering the follicle
9. Granulosa wall ruptures, releasing the oocyte and liquor folliculi
10. Secondary oocyte in Metaphase II, covered by zona pellucida and granulosa cells is released into the hovering open end of fallopian tube

Question 33

What occurs following ovulation?

Answer 33

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

Question 34

What do granulosa cells differentiate into?

Answer 34

Granulosa lutein cells

Question 35

What do theca interna cells differentiate into?

Answer 35

Theca lutein cells

Question 36

What do granulosa lutein cells and theca lutein cells produce?

Answer 36

Estrogens and PG

Question 37

What do estrogens and PG stimulate?

Answer 37

Stimulate the maturation and glandular activity of the endometrum, preparing the uterine lining for possible implantation of the bastocyst

Question 38

What is the corpus albicans?

Answer 38

Dense CT scar formed after the corpus luteum regresses following menstruation or pregnancy

Question 39

What occurs if the ovulated oocyte is not fertilized or the patient is not pregnant?

Answer 39

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

Question 40

What occurs if the patient is pregnant and the ovulated oocyte is fertilized?

Answer 40

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

Question 41

What is PCOS?

Answer 41

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

Question 42

What will PCOS present with?

Answer 42

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

Question 43

How is PCOS treated?

Answer 43

Patient must be treated with hormone therapy to establish normal estrogen/progesterone ratio

Sometimes surgical treament

Question 44

If patient as PCOS and oligomenorrhea (scanty menstruation), what is it?

Answer 44

Disease called Stein-Leventhal Syndrome

Question 45

What is the possible cause of PCOS?

Answer 45

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