Lifecycle histology and miscellaneous topics

1. Lifecycle histology and miscellaneous topics Mike Ori

2. Disclaimer • Faculty has not reviewed or vetted the information contained herein. • If you think this material is any way accurate, you are mistaken. • Celebrity voices are impersonated

3. Describe the structure of the ovary

4. Outer epithelial layer referred to as the germinal epithelium overlies a connective tissue capsule called the tunica albuginea. Underlying this is the parenchyma and stroma organized into a cortex and medulla.

5. Embryologically, where do the primordial germ cells originate?

6. In the yolk sac.

7. Whats the difference between an oogonia and an oocyte

8. Oogonia are the result of mitotic expansion of the primordial germ cells. When they enter meiosis, they become oocytes

9. How many oocytes does a female have in early fetal life, birth, puberty. How many are ovulated?

10. Fetal – 6 million • Neonatal – 2.5 million • Puberty – 400K • Ovulation – 450

11. Distinguish a primordial follicle and a primary follicle.

12. Primordial follicles are more or less the resting state of the female gamete. They contain a primary oocyte arrested at prophase I surrounded by a thin layer of squamous granulosa cells. • Primary follicles are entering the active state. The granulosa cells have plumped up to cuboidal/columnar and the zona pelucida has begun to form. As the primary follicle matures, the theca forms from adjacent stromal cells.

13. Distinguish antral from graafian follicles

14. Antral follicles have a multi-layer theca, multi-layer granulosa, and small fluid filled cavities called antral cavities. • Graafian follicles are larger than antral follicles and the fluid filled spaces have coalesced to form a lagoon in which the oocyte floats surrounded by a cloud of granulosa cells (cumulus oophorus). The cloud is a attached to the wall of the follicle by a stalk of granulosa cells

15. Name the regions of the uterine tube

16. (Fimbriae) – infundibulm – ampula – isthmus - intramural

17. What are the two epithelial cells of the uterine tubes

18. Ciliated cells – move the ovum toward the uterus • Peg cells – produce nutritive medium and enzymes necessary for capacitation

19. When and at what stages is the oocyte halted during meiosis and when does each continue.

20. Meiosis I • Entered in fetal life • Halted at prophase I • Completes at ovulation • Meiosis II • Entered at ovulation • Halted at metaphase II • Completes on fertilization

21. What is the second messenger system for FSH and LH

22. They are both Gs linked to cAMP.

23. Describe the the two cell theory of hormone synthesis in the ovary.

24. Two cells are required to synthesize estrogen. • Theca cells overlying the follicle respond to LH to synthesize androgen (androstenedione). The androgens diffuse across the basement membrane of the follicle and enter the adjacent granulosa cells. • Granulosa cells respond to FSH to convert androgen to estrogen.

25. What does LH do in both males and females

26. It induces the production of androgens • Androstenedione in females • Testosterone in males

27. Why is [FSH] generally lower than [LH]

28. Both FSH and LH are controlled by GnRH and both are inhibited by estrogen and progesterone but FSH is also inhibited by inhibin thus there are more inhibitory inputs in the FSH pathway.

29. Why does LH and FSH decrease in the luteal phase and pregnancy even though estrogen levels are high in pregnancy?

30. Progesterone is always inhibitory to GnRH thus the high levels of progesterone in the luteal phase and during pregnancy prevent FSH and LH release and subsequently ovulation. • NOTE: its not completely clear to me if the estrogen levels are such that inhibition or induction of GnRH/LH/FSH would occur without progesterone. I think they are inhibitory levels.

31. When does the menstrual cycle begin

32. By convention with the first day of menses.

33. What are the phases of the menstrual cycle

34. Menses (1-~5) • Follicular/proliferative (1-14) • Luteal/secretory (14-1)

35. What is the purpose of the cervical mucous glands

36. They secrete mucous of varying quality depending on the hormone milieu. Normally the mucous is thick and retards entry of both sperm and micro-organisms into the upper reproductive tract. When estrogen levels peak at mid-cycle, the mucous secretions thin and allow access.

37. Describe the epithelium of the cervix. What is the squamocolumnar junction and why is it important

38. In the endocervical canal, the cervical epithelium consists of simple columnar epithelium, whereas in the vagina the cervix is covered with a non-keratinized squamous epithelium. The squamocolumnar junction is the point where the transition is made from columnar to squamous epithelium. The area surrounding this junction is called the transformation zone. It is the site of squamous metaplasia caused by HPV infection and thus is the site of genesis for most cervical squamous cell carcinomas

39. Describe the glandular structure of the vagina

40. The vagina is non-glandular. Secretions from arousal are due to increased hydrostatic pressure from congestion of the venous plexus lining the organ.

41. Why do vaginal squamous epithelia synthesize glycogen? What controls glycogen synthesis and how would this impact the vaginal tract with age?

42. The glycogen synthesized in the vaginal mucosa is released into the lumen when the cells are sloughed. The glycogen is fermented to lactic acid by symbiotic bacterium, creating an low pH environment that is hostile to many pathogenic species. Synthesis is controlled by estrogen. • Thus as women age, the pH of the vagina should increase, leading to an increase in candida infections however, in reality (or up to date at least) this increase in candida infection does not occur…go figure

43. Mammary glands are glorified versions of what?

44. Apocrine sweat glands…put that way, what’s all the fuss about?

45. If sperm were vegetarian, what kind would they be?

46. Frutitarians as they consume fructose for fuel

47. Describe the structure of a seminiferous tubule

48. The seminiferous tubule is divided into a basal and adlumenal compartment. Spermatogonia lie within the basal comparment and give rise to the spermatocytes of the adlumenal compartment. Sertoli cells rest against the basement membrane of the tubule and extend through to the adlumenal compartment. Leydig cells lie outside the tubule in the testicular stroma.

49. What is the function of leydig and sertoli cells

50. Leydig cells respond to LH to produce testosterone. • Sertoli cells secrete androgen binding protein which effectively traps testosterone within the seminiferous tubule thus ensuring that high the levels of testosterone required to support spermatogenesis are maintained.