Explain FSH action on developing ovarian follicles
Pituitary FSH → ovarian follicles → follicle development and oestrogen production. FSH is a blood-borne signal; the ovary is its target, not its source.
Extended only (Supplement); Biology 0610, 2026–2028. Use the stated specimen features and evidence. Diagrams are schematic. Written practice is self-checked
Before you begin
- Recall endocrine glands, blood-borne hormones, ovaries, testes, uterine lining, ovulation and implantation.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Where is FSH secreted?
What you will learn
- Trace pituitary FSH to its ovarian target
- Connect follicle development with oestrogen production
Original teaching model.
| Feature | Meaning |
|---|---|
| Source | Pituitary gland |
| Target | Ovarian follicles |
| Effects | Follicle development; oestrogen production |
| Distinct later trigger | LH surge and ovulation |
Trace pituitary FSH to its ovarian target
Follicle-stimulating hormone, abbreviated FSH, is secreted by the pituitary gland. It travels in the blood to the ovaries and stimulates development of ovarian follicles containing eggs. The source is therefore pituitary and the target is ovarian tissue. Do not name the follicle as the FSH source simply because the hormone acts there.
FSH also stimulates oestrogen production by the developing follicles. This connects the pituitary signal with a second endocrine signal from the ovary. Oestrogen can then act on uterine lining and feed back on the pituitary. A causal chain should keep the two sources distinct: pituitary FSH acts on the ovary, and ovarian oestrogen acts on other targets.
Connect follicle development with oestrogen production
FSH is important in follicle development, but the LH surge is the named trigger for ovulation in this pathway. Saying that every increase in FSH releases an egg immediately confuses development with the later release event. A developing follicle and a released egg represent different stages and require appropriately named hormonal roles.
The original route diagram uses solid arrows for stimulation and clearly labels source and target. It models the required relationship, not every endocrine regulator. If an exercise stipulates reduced FSH stimulation, predict less follicle development and oestrogen stimulation within that model; do not infer that every ovarian function has stopped or diagnose an individual condition.
Pause and explain
Which two effects belong to FSH in this pathway?
Worked example
Trace a pituitary signal that promotes follicle development.
Show the worked solution
- Name FSH from pituitary.
- Connect blood transport with ovarian follicle stimulation.
Answer Pituitary FSH travels in blood to ovaries, stimulating follicle development and oestrogen production.
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Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Give the FSH source, transport route, target and two effects.
Give me a hint
Use pituitary, blood and ovaries.
Compare my reasoning
- Name source and route.
- Name follicle development and oestrogen stimulation.
Pituitary → FSH in blood → ovarian follicles; FSH stimulates follicle development and oestrogen production.
Look for these in your work
- Include source and target
- Give both effects
Explain why ovarian oestrogen rising after FSH stimulation does not mean the pituitary produced that oestrogen.
Give me a hint
Separate two endocrine sources.
Compare my reasoning
- Place FSH secretion at pituitary.
- Place oestrogen production in ovarian follicles.
Pituitary FSH stimulates the ovarian follicle; the follicle produces oestrogen. A stimulus source and a responding hormone source are distinct.
Look for these in your work
- Name both sources
- Preserve the causal link
A stipulated model reduces FSH stimulation. Predict two affected responses without claiming all ovarian functions stop.
Give me a hint
Limit the conclusion to the FSH pathway.
Compare my reasoning
- Identify follicle-development stimulation.
- Identify oestrogen-production stimulation.
Reduced FSH stimulation would reduce stimulation of follicle development and oestrogen production in the model; it does not prove all ovarian functions cease.
Look for these in your work
- Name both affected responses
- Retain the model limit
Common mistakes
- FSH source and target are different.
- Follicle development is not immediate egg release.
What can you explain now?
Which two effects belong to FSH in this pathway?
Compare with the explanation
Follicle development and oestrogen production
Both occur through ovarian target responses.
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Make it stick
Explain trace pituitary fsh to its ovarian target and connect follicle development with oestrogen production. Follow the event arrows or graph labels before opening the solutions.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.