Histology - Lecture 25 - Female Reproductive System Flashcards
3 functions of the female reproduction system?
- Exocrine: produce ova (ovaries)2. Endocrine: produce female hormones responsible for the production of germ cells, for the maintenance of accessory organs, and for secondary sex characteristics (ovaries mainly)3. Nurture of infants
What are the 3 major anatomical components of the female reproductive system?
- Internal organs: 2 ovaries, 2 uterine tubes, the uterus and the vagina2. External genitalia: labia minora, labia majora, clitoris, vestibular glands3. Mammary glands
Why are mammary glands considered part of the reproductive system?
Because they are under endocrine control and further develop during pregnancy
What are the primary female sex organs?
Gonads = ovaries
2 other names for female germ cells?
Oocytes = gametes
What are the 3 age related changes in function of the female reproductive system?
- Menarche: first menses, initiation of pubertal development (~12-13 year old)2. Menstrual cycle: cyclic appearance of menses associated with fertility3. Menopause: cyclic nature of the tract becomes irregular and eventually disappears in favor of a tonic status (~50 year old)
List and describe the 4 layers of the ovary. What layer is the major site of ovarian cancer?
- *Outer layer: simple squamous/cuboidal/columnar germinal epithelium (misnomer)2. Tunica albuginea: dense connective tissue3. Cortex: containing the ovarian follicles in various stages of development4. Medulla: occupies the central region of the ovary and consists of blood vessels and connective tissue
List the 8 stages of follicular development in the cortex of the ovary.
- Primordial follicles2. Primary unilaminar follicles 3. Primary multilaminar follicles 4. Secondary follicles 5. Graffian follicles6. Corpus luteum7. Corpus albicans8. Atretic follicles
How many primordial follicles at birth?
2 M
Describe primordial follicles.
Primary oocyte arrested in meiotic prophase I, dictyotene stage, surrounded by a layer of flattened follicular cells, which are surrounded by stromal cells
Have primordial follicles responded to FSH?
NOPE
What happens to primordial follicles at puberty?
Secretion of FSH => stimulates groups of follicles to undergo development and produce estrogen and their follicular cells acquire more FSH receptors and become more columnar => now called granulosa cells
Where does meiosis of primary follicles start?
In utero
Where are LH and FSH secreted from?
Anterior pituitary: pars distalis and pars tuberalis
How many primordial follicles respond to FSH every 28 days?
Up to 20 primordial follicles
Describe primary unilaminar follicles.
Primary oocyte surrounded by one (unilaminar) layer of granulosa cells
During what follicular stage does the zona pellucida start forming?
Primary unilaminar follicle
Describe primary multilaminar follicles.
- Primary oocyte surrounded by more than one (multilaminar) layers of granulosa cells 2. Granulosa cells and the oocyte together deposit an extracellular coat, the zona pellucida onto the primary oocyte, which is traversed by delicate cytoplasmic processes from the granulosa cells (filopodia) and microvilli projecting from the oocyte3. Stromal cells differentiate to form the theca interna
Describe secondary follicles.
- Identified by the presence of an antrum (cavity) formed from accumulations of hyaluronic acid-rich fluid (follicular liquor)2. Theca further differentiates into a theca interna and a theca externa
Other name for secondary follicles.
Antral follicles
During what stage(s) of follicular development is the first meiotic division complete?
Around the time of the transition from primary multilaminar to secondary follicle
What does the follicular liquor of secondary follicles contain? Role?
Oocyte meiosis inhibitor (OMI) that maintains arrest of the oocyte in meiotic prophase II (dictyate stage)
What does the theca interna of secondary follicles consist of?
Cells are steroidogenic producing androstenedione/testosterone, which is an intermediary of steroidogenesis and diffuses into the follicle proper to be metabolized by the granulosa cells into estrogen+ they have capillaries to facilitate the diffusion of steroids throughout the body+ liquid droplets (typical of steroid producing cells)
What does the theca externa of secondary follicles consist of?
Consists mainly of connective tissue
Describe Graafian follicles.
- Contains a very large antrum filled with follicular liquor 2. Oocyte that is eccentrically located and connected to a layer of granulosa cells that line the inner aspect of the mature follicle by a pedicle of granulosa cells3. Corona radiata: inner most single layer of granulosa cells surrounding the oocyte that are more tightly packed together4. Cumulus oophorus: several more accumulations of granulosa cells outside of the corona radiata continuous with the pedicle
During what follicular stage is the occyte arrested in the dictyate stage?
Secondary follicle
During what meiotic stage does ovulation happen?
Metaphase II
How many secondary follicles become a Graafian follicle? What happens to the rest of the 20?
JUST ONECould stay arrested and develop later or could die (become atretic)
Other names for Graafian follicle?
Mature follicle = tertiary follicle
During what follicular stage does ovulation occur?
Graafian follicle
Describe ovulation of the Graffian follicle.
Dominant follicle bulges from the surface of the ovary => LH surge => follicle produces local progesterone that is sequestered inside the follicle => stimulation of proteolytic enzymes (e.g. collagenase) to weaken the follicular wall + movement of fluid into the follicle via prostaglanding secretion => LH overrides the action of OMI => resumption of meiosis from prophase II to metaphase II + follicle swelling and rupture dispersing OMI => ovulation occurs and ovum is expelled into the peritoneal cavity
What precisely causes the ovulation of the Graafian follicle?
Enzymatic dissolution of the connective tissue (not increase in pressure)
What happens to the corona radiata and cumulus oophorus upon ovulation?
Remains attached to the ovum following ovulation and even following fertilization
What DIRECTLY surrounds the oocyte following ovulation?
Zona pellucida
Other name for corpus luteum?
Yellow body
Describe atretic follicles.
Partially developed follicles become developmentally arrested and degenerate:- detachment of granulosa cells- death of the oocyte, which is no longer oval shape but wobbly instead- formation of pycnotic (dark) bodies- apoptosis
When does follicular atresia occur (development of atretic follicles)? What to note?
From the time of birth until menopauseNote: most prominent just after birth and during pregnancy
Why do some follicles become atretic?
Natural selection
Describe the corpus luteum.
Formed after ovulation from the remnants of the ruptured graffian follicle: 1. Follicular fluid is lost resulting in the collapse of the follicular wall forming a pleated corpus luteum 3. Granulosa lutein cells: under the influence of LH from the anterior pituitary, the granulosa cells of the former Graafian follicle become enlarged, occupy most of the space of the corpus luteum and secrete progesterone4. Theca lutein cells: former theca interna of the Graffian follicle become small darkly staining lutein cells and now produce estrogen
Role of theca and granulosa lutein?
Form a temporary endocrine gland whereby elevated progesterone and estrogen prevent development of any new follicles and prevent ovulation for the remainder of that cycle because cause continuous negative feedback to the hypothalamus-pituitary axis to inhibit LH/FSH secretion and surge, thus inhibiting ovulation
What is the basis of the contraceptive pill?
Progesterone and/or estrogen prevent development of any new follicles and prevent ovulation just like the corpus luteum after ovulation because cause continuous negative feedback to the hypothalamus-pituitary axis to inhibit LH/FSH secretion and surge, thus inhibiting ovulation
What happens to the corpus luteum if pregnancy does not occur 2 weeks post-ovulation?
Progesterone from the granulosa lutein cells negatively feeds back to the pituitary => reduced LH secretion => degeneration of the corpus luteum into a corpus albicans => degenerates by autolysis and phagocytosis by macrophages
What happens to the corpus luteum if pregnancy occurs within 2 weeks post-ovulation?
Corpus luteum is rescued from degeneration by chorionic gonadotrophin (hCG) produced by the placenta, which is homologous to LH and promotes estrogen and progesterone secretion
Consequence of phagocytosis of corpus albicans?
Residual scar of connective tissue that results from the absorptive process may take years to completely disappear
Other name for primary multilaminar follicle in development?
Pre-antral follicle
Purpose of zona pellucida?
Block to polyspermy
What separates the granulosa layer of the secondary follicle from the theca interna?
Basement membrane
Does ovulation of the ovary happen on the right or left side?
Alternates from month to month
What does the corpus albicans consist of?
Cytoskeletal elements, proteins, extracellular matrix components
What happens to the infundibulum around ovulation?
Its fimbriae move around in a manner to trap and draw the ovum into the opening of the infundibulum
Where does fertilization occur?
Ampulla of uterine tube
What can lead to multiple concurrent pregnancies?
LH injections because they can induce multiple ovulations
What does reduced ovulation mean?
Reduced fertility
List the 3 layers of the wall of the oviduct. Describe each.
- Mucosa with folds lined with simple cuboidal to low columnar epithelium with two cells types, secretory cells (non-ciliated) and ciliated cells, which are both estrogen dependent => ciliated cells help move the ovum through the oviduct, whereas the secretory cells secrete proteins to nurture a potential zygote + underlying lamina propria (connective tissue)2. Muscularis: inner circular and outer longitudinal layer3. Serosa of visceral peritoneum: connective tissue connected to the broad ligament of the uterus