11.10 Histology of the Female Reproductive System Flashcards
What are the major functions of the ovaries?
- Produces gametes
- Produces hormones (it is an endocrine organ)
- Responsive to circulating hormones
Describe the location of the ovaries
They are 2 bilaterally placed on either side of the superior aspect of the uterus/fallopian tubes.
They are attached to the posterior face of the broad ligament.
They are anchored by an ovarian ligament (to uterus) and suspensory ligament (to pelvic wall)
Are the ovaries physically attached (in direct contact) with the fallopian tubes?
No.
The ovaries are in very close proximity to the fallopian tube (fimbrae)
Describe the structure of the ovary
Divided (hard to see) into…
- Inner medulla
- highly cellular loose connective tissue
- highly vascularised vessels
- scattered smooth muscle cells
- Outer cortex
- less blood vessels,
- location of ovarian follicles – oocytes of varying maturities
Is the surface of the ovary smooth or roughened?
Why is this so?
The surface is irregular.
Scarring from release of oocytes from the surface
Describe the outer surface of the ovary
70% of ovarian tumours are from this epithelium
Surface is a simple epithelium (squamous or cuboidal) continuous with mesothelium.
The mesothelium surrounding the ovary is also shared with the broad ligament and the others covering the structures of the cavity
What layer is underneath the surface epithelium of the ovary?
What does this layer contain?
Tunica albuginea
- All of the oocytes
- Dense connective tissue
- Smooth muscle cells
What is the change in oocyte numbers in the ovaries from foetal life through to death?
- 5 million per ovary in embryo
- 0.5 million by birth
- Most degenerate over life
- A few thousand go through most of a maturation cycle and around 500 are released into the fallopian tube
- These run out at the point of menstruation
Describe the lifecycle of one oocyte through the maturation stages
- Oogonium
- Primordial oocyte (present in the foetus)
- Primary oocyte (arrested in first meiosis)
- Secondary follicle
- Graafian follicle (mature follicle)
- Secondary oocyte
- Mature ovum (upon fertilisation)
Describe the primordial oocyte
- What are formed in the embryo
- Smallest oocytes
- On outside they are surrounded by squamous follicle cells.
- The follicle cells provide the microenvironment required
- These cells are surrounded by a common basal lamina that holds it all together
- Oocyte is arrested in prophase of meiosis 1 (incomplete meiotic division)
Describe the primary oocyte
- Oocyte now surrounded by zona pellucida (within follicle cell layer)
- Oocyte enlarges, follicular cells become cuboidal and multilayered granulosa cells (form stratum granulosum)
- Surrounding stromal cells start to form theca interna and externa (surround stratum granulosum)
Describe the seconday follicle
Is this the same as the secondary oocyte?
- The stratum granulosum thickens (proliferation)
- Fluid filled cavity (antrum) appears
- The oocyte is suspended on a stalk of granulosa cells (cumulus oophorus)
- A small number of granulosa cells directly surround the oocyte (corona radiata)
This is not a secondary oocyte. Just the primary oocyte that has had the environment directly around it changing.
What is the mature follicle called? How big is it?
Graafian follicle (10 mm diam.)
What happens to the Graafian follicle in ovulation
Eventually the antral cavity ruptures and this rupture extends to the external surface of the overy such that the oocyte is released from the antrum and the ovary.
The oocyte still has the surrounding of the remains of the granulosa called the corona radiata
High levels of oestrogen stimulate an LH and FSH surge. What does this signal?
Under LH surge, oocyte completes first meiotic division (started years before) = secondary oocyte (within the Graafian follicle)
Then ovulation occurs = the follicle ruptures
The Oocyte is released into body cavity and can enter fallopian tube – lasts 24 h if not fertilised
What happens to the remainder of the Graafian follicle once the oocyte has been released?
Once follicle loses oocyte, it forms corpus luteum
Stromal, granulosa and thecal cells invade and fill it up so it becomes a solid mass: causing a differentiatiation into luteal cells
The corpus luteum matures to become high vascularised and contain high amounts of lipid (yellow appareance).
What is the significance of the lipid content?
Lipid (cholesterol) forms the basis of the steroidogenic nature of the corpus luteum. It uses lipid content to produce steroid hormones: progesterone and estrogen to prepare endometrium
The corpus luteum lasts until the placenta is able to take over.
How long does the corpus luteum last for if there is no pregnancy?
Lasts 14 days, if no fertilisation becomes corpus albicans and involutes with time
What is the fallopian tube?
What are the major functions?
(Uterine tubes)
- Unite sperm and egg
- Provide environment for fertilisation and initial development
- The opening (fimbrae) collects released oocytes
What aids the fallopian tube’s ability to collect the egg from the pelvic cavity once the ovary has expelled it? [3]
- Finger like structures on the infundibular opening (fimbraie)
- Cilia lining the tube helps to beat the ooctye along
- A gentle flow of fluid flows into the fallopian tube in the direction of the uterus