Lecture 42 Flashcards
Which statement regarding ovarian follicles is FALSE?
A. Primordial follicles are stimulated by FSH to undergo maturation.
B. A secondary follicle contains a primary oocyte.
C. ThezonapellucidaformsinGraafianfollicles.
D. Granulosa cells convert androgens to estradiol.
E. Atreticfolliclesfailtodevelop.
C
zona pellucida is secreted by oocyte and forms right at the unilaminar
primary follicle stage
oocyte is released from ovary when it is at metaphase of meiosis II.
oocyte enters ep lined tube that is not directly connected to ovary.
The oocyte gets fertilized within Fallopian tube. then enters uterus
as a blastula (embryo)
travelling through oviduct
Following ovulation, the ovum (arrested at metaphase of meiosis II) travels through the oviduct and completes meiosis II upon sperm entry. Cleavage of the zygote commences in the oviduct.
oviduct lengths
Fallopian tube aka oviduct aka uterine tube is divided into several parts: Ampulla 7-8 cm long Isthmus 4 cm long Intramural segment (wall of uterus) 0.6 cm thick
Ovary does not directly connect with fallopian tube
Fallopian tube has funnel shape extension called infundibulum that contains motile branches called fimbriae. Hormonal regulation during ovulation increases activity of fimbriae and they sweep over surface of ovary to capture any oocytes that are released.
If oocyte doesn’t enter lumen of the oviduct, it causes ectopic pregnancy, which is when the oocyte implants somewhere else in the body cavity. Placenta can develop and embryo can form, but likely won’t survive long. Can have bad consequences to both mom and baby.
Order: ovary to infundibulum to ampulla of Fallopian tube to isthmus of Fallopian tube to the wall of the uterus called intramural segment.
Ampulla of oviduct
Mucosa is highly branched and ep lines the lumen of the oviduct.
Cellular lamina propria (loose CT) underlies a simple columnar ciliated ep with peg cell. Ciliated cells present and there are basal
bodies; interspersed by non-ciliated cells aka peg cells.
ovum is in intimate contact with the epithelium. Non-ciliated peg cells have microvilli and secrete nutrient-rich fluid to bathe the travelling ovum. Ciliated cells generate a flow toward the uterus; sweeping motion of cilia makes a flow of fluid from the infundibulum of the oviduct towards the uterus, so passively, the ovum travels
spermatozoa cannot attach to any oocyte when they leave male reproductive tract bc they have decapacitation factor (proteins that
cover the sperm receptors and docking sites). Decapacitation factor is removed by enzymes within the peg cell fluid, which activates the spermatozoa.
Somewhere within the oviduct, spermatozoa and oocyte meet up, and zygote is formed
Uterus - general
Oviduct to uterus (endometrium surrounded by myometrium) body to cervix to vagina
Ovary is attached to uterus by a ligament or CT strand. There is also broad ligament below ovary that brings in blood
vessels.
Uterus is a pear shaped organ that has broad upper extension called body of uterus. Then it has narrow part continuous with uterus called cervix.
Uterus is hollow with lumen. The lumen within cervix is called cervical canal. This opens up into vagina.
The uterus at low mag can be divided into a thick muscular part (myometrium, smooth muscle), then ep part that stains more blue/ purple called endometrium. Endometrium is ep lining of uterus, myometrium is smooth muscle component of wall of uterus
Uterus - endometrium and myometrium
Endometrium:
• Changes in response to estrogen and progesterone in preparation for implantation
• 2 layers: Functional layer to facilitate implantation and is lost during menstruation. Basal
layer that regenerates the endometrium every month
• Endometrial ep glands reach from surface to myometrium; the cells forming the glands secrete proteins needed for embryo implantation
Myometrium:
• 3 Smooth Muscle Layers
• Hypertrophy (each individual cell gets bigger, cell size) and Hyperplasia (increasing in cell number) during pregnancy
• Contracts during parturition aka birth via Oxytocin. Oxytocin is made in hypothalamus and is released in posterior pituitary
• Smooth muscle cell nuclei: Longitudinal orientation and transverse orientation in H and E
Endometrium
Endometrial epithelial glands made up of Simple columnar epithelium
- there are tubular glands that grow in from the surface and are formed by the simple columnar ep. these cells have secretory activity that changes in response to hormonal regulation.
Lamina propria underneath ep: Highly cellular loose connective tissue
Arteries in uterus
Endometrium
a. Stratum functionale
- capillary
- lacunae
- uterine gland aka endometrial gland (continues into stratum basale)
b. Stratum basale
- uterine gland aka endometrial gland (continuation from stratum functionale)
- spiral artery
- straight artery
Myometrium
- radial branch
- arcuate artery
Blood supply in endometrium comes from myometrium. Arcuate arteries of myometrium (at border of myometrium and endometrium) send straight arteries into stratum
basale. In stratum basale, the arteries coil to become spiral artery, which then supply the functional layer of endometrium with capillary networks called lacunae
At one point during menstrual cycle, the spiral arteries contract. Just before menstruation, arteries contract, and functionale layer is deprived of oxygen and nutrients. Then the cells die and blood vessels start leaking, causing menstrual bleeding. The functionale layer is lost during menstruation
Basale layer is supplied by straight arteries that do not continue into functional layer. They form their own capillary network along the bases of the glands. The bases of the glands will be left behind after menstruation to regenerate the surface of the endometrium. So the height of the endometrium changes a lot after menstruation
Premenstrual endometrium
Contraction of spiral arteries: The functional layer suffers hypoxia (Ischemic phase: blood flow and oxygen is restricted) just before menstruation (contraction of spiral arteries) and before loss of functionale layer
Menstrual endometrium
The basal layer is preserved during menstruation and regenerates the endometrium
The functional layer is lost during menstruation, which is after the ischemic phase (lack of oxygen and blood flow)
Ovarian cycle
Ovarian cycle: Follicular phase (estrogen secreted by growing follicles) and Luteal phase (estrogen and progesterone secreted by corpus luteum)
- Follicular phase occurs via FSH and LH that causes increased estrogen. Follicular phase is when follicles grow before ovulation
- Half way through menstrual cycle, there is LH surge that results in ovulation and formation of corpus luteum. This is progestational phase
bc corpus luteum makes lots of progesterone.
After menstrual phase (day 0-5) and under the influence of estrogen (from follicular phase), the glands will grow and form straight glands to restore the functionale layer.
- At ovulation (day 14), when progesterone is secreted, the glands become secretory (during luteal phase, also called secretory phase)
- So, first the glands grow, then under influence of progesterone, the glands increase in size
At day 28, there is ischemic phase.
- If no implantation, corpus luteum stops making progesterone. the decline of progesterone is the signal for spiral arteries to contract to cause menstruation
- If implantation occurs, the corpus luteum continues to make progesterone to support endometrium and placenta.
The endometrial (menstrual) cycle
- menstrual phase (day 0-5)
- During menstruation, has lots of bleeding in tissues, cells are falling apart, lots of pyknotic nuclei. functional layer is being
sloughed off - proliferative phase (day 5-14)
- ep cells reform the surface and form long endometrial glands that are straight and surrounded by highly cellular loose CT lamina propria. - secretory phase (day 14-28)
- under influence of progesterone, after ovulation, the glands become cork screw arrangement. so they are sacculated. the glands are filling up with secretions to anticipate the arrival of fertilized ovum
Proliferative endometrium estrogenic phase (9 days)
Endometrial surface ep, Developing Endometrial Gland, Highly cellular Lamina Propria
After birth of baby, the sucking or breast feeding makes lots of prolactin, which inhibits the development of follicles.
Glands are first solid cords before they become hollow. They develop from the proliferation of surface ep, then the cells invade the highly cellular lamina propria. This lasts for 9 days during the estrogenic aka follicular phase of ovarian cycle.
Secretory endometrium progestational phase (13 days)
after ovulation, there is secretory endometrium
glands now fill up with secretions. they have sacculated appearance. the cells bulge out into lumen
Pre menstrual endometrial ischemia (1 day)
- Blood accumulates in stroma and in endometrial glands
- Desquamating epithelial cells
- disintegrating blood vessels
As progesterone levels decrease, spiral arteries contract and there is lots of RBC in lamina propria (lots of bleeding). Nuclei of cell become pyknotic. Blood vessels disintegrate. The ep cells are sloughing off and become part of the menstrual flow.
Changes in endometrial glands during phases of the menstrual cycle
Day 5-14: Proliferative Phase
Day 15-21: Early Secretory Phase
Day 21-28: Late Secretory Phase
Proliferative phase:
• Straight glands
• No secretory activity
• cells divide and elongate the glands. columnar ep cells at bottom
Early secretory phase:
• Coiling glands
• Accumulation of glycogen
• No secretory activity
Late secretory phase:
• Highly coiled glands
• Secretory activity
Cervix
Has: stratified squamous Non-keratinized Epithelium, Simple columnar mucus-secreting epithelium, Nabothian cyst, cervical glands
Cervical canal has lots of ep glands that open up into canal to secrete cervical mucus
- in cross sec, the cervical glands look coiled
- vagina does not have any secretory components. Any fluid and mucus that fills the vagina comes from cervical glands of cervix
Consistency of cervical mucus changes in response to estrogen and progesterone.
- depending on the stage of menstrual cycle, the mucus is either thick or liquid.
- this has functional implication. Important for spermatozoa to have nice free flowing environment as it goes from vagina through cervix into Fallopian tube.
- during first half of menstrual cycle, and close to ovulation, the fluid is liquidy
- after ovulation, or towards end of menstrual cycle, when fertilization occurs, the mucus becomes thicker under influence of progesterone to prevent further impregnation of the female
Cervical glands make mucus and sometimes, if the mucus is thick, the glands get plugged. This forms a Nabothian cyst (cyst filled with mucus, not disease inducing)
- region where cervix protrudes into vagina is called ectocervix; this location has lots of Nabothian cysts.
Ep that lines the ectrocervix is the same as ep of the vagina, but it still covers part of the cervix that protrudes into vagina
- ep changes from stratified squamous non keratinized ep in vagina to simple columnar ep in cervix
- bc there is a change, there is danger of metaplasia (the differentiation state of cell can be confusing to the cell).
- There is chance of mutations occurring and cervical cancer developing, so doctors will take Pap smear (sample of cervical lining at ectocervical ep) and look at cell to assess it. This is pre diagnostic tool to look for cervical cancer, that often is also mediated by HPV
Vagina
Stratified squamous non-keratinized epithelium
- fibromuscular CT underneath the lamina propria
- this type of ep also in esophagus
- ep cells in vagina store glycogen, but esophagus ep does not. This makes the layers of ep cells of vagina look empty inside due to glycogen in cell cytoplasm
- The ep cells of vagina are filled with glycogen. As ep are sloughed off, it provides food for bacteria.
- So there is useful fauna and flora of organisms that live in vagina to prevent invasion of harmful bacteria. Vagina makes food for invaders for protection
Ovarian cycle
- hormonal regulation of ovary comes from pituitary gland (FSH and LH), which then causes growth of follicles that then make estrogen. - LH surge causes ovulation. ovulation triggers production of corpus luteum and high levels of progesterone.
- the changes in estrogen and progesterone levels in blood affect the endometrium.
proliferative phase (aka part of follicular phase after menstrual phase) under control of estrogen.
secretory phase (aka luteal phase) under control of progesterone
