Gametogenesis Flashcards
What is a follicle?
An Ovarian structure that enables the ovary to fulfill its dual function
What is folliculogenesis?
Formation of the graafian follicle
What is follicle turnover?
Frequent emergence of new follicles
What is ovulation?
Release of oocyte from the graafian follicle
What are the seven events during follicular growth?
- Recruitment of follicles
- Selection of dominant follicle(s) and atresia of the remaining
- Nuclear maturation of oocyte
- Cytoplasmic maturation of oocyte
- Steroid synthesis
- Stigma formation
- Release of egg
What happens during the Recruitment of follicles during follicle growth?
cohort of follicles are selected
What is the Recruitment of follicles during follicle growth dependent on? how does it get it?
FSH - Theca interna has FSH receptors
What happens during the Selection of dominant follicle phase of follicle growth?
- LH receptors are developed in the granulosa cells
- remaining follicles undergo atresia
- steroidogenesis of estradiol
What happens during the Nuclear Maturation phase of follicle growth?
- Meiotic arrest until an LH surge is reached (stopped in prophase 1)
- Meiotic resumption until metaphase 2 where it stops again
What happens during the Cytoplasmic Maturation phase of follicle growth?
- Granulosa cells around the oocyte begin to loosen
- mRNA, proteins, substrates, and nutrients that are required to achieve oocyte and embryonic development accumulate
What happens during prophase 1?
Chromosomes pair
What happens during metaphase 1?
Paired chromosomes migrate to center due to centrioles
What happens during anaphase 1?
Chromosome pairs are separated and pulled to opposite ends of the cell
What happens during telophase 1?
Cell divides
What happens during prophase 2?
Centrioles duplicate and cell gets ready for another division
What happens during metaphase 2?
Chromosomes line up in the middle of the cell
What happens during anaphase 2?
Chromosomes as pulled apart and pulled to opposide sides of the cell
What happens during telophase 2?
Cell divides and each becomes haploid
What does the zona pellucida which surrounds the ovum do?
Help protect the ovum from being bombarded by many sperm at once. (prevents sperm from reaching egg easily)
Which steroids are produced and where during the steroid synthesis of follicular growth?
- Cholesterol is transported to the ovarian follicle -> High density lipoproteins and low density lipoproteins
- Testosterone synthesis by theca interna (controlled by LH)
- Estradiol synthesis by granulosa cells (Controlled by FSH)
What happens during the stigma formation of follicular growth?
- The apical wall becomes thin (weaker)
- Becomes avascular (further weakens)
- Ruptures at ovulation
What happens during the release of egg or ovum during follicular growth?
- Cumulus-oophorus complex loosens
- Prostaglandin causes uterine contractions + vascular contractions
- Ovum is expelled and picked up by the oviduct
Which hormones are produced in great quantity during ovulation?
- GnRH and LH
What is the biochemical composition of Follicular fluid?
- Steroids and glycoproteins secreted by cells of the follicle wall and serum exudate.
- Enzymes, prostaglandins and gonadotropins
What substances are present in follicular fluid and when?
Estradiol - Estrus Progesterone - Near ovulation Androstenedione - Polycystic Oocyte maturation inhibitor (OMI) Inhibin
What are the functions of the follicular fluid? (11)
- Regulation of the functions of granulosa cells
- Initiation of follicular growth
- Steroidogenesis
- Oocyte maturation
- Ovulation
- Egg transport to the oviduct
- Preparation of the corpus luteum
- Regulation of the follicular cycle
- Sperm metabolism
- Capacitation
- Early embryonic development
What 3 major changes does the pre-ovulatory follicle undergo during the ovulatory process?
- Cytoplasmic and nuclear maturation of the oocyte
- Disruption of cumulus cell cohesivness among the cells of the granulosa layer
- Thinning and rupturing of the external follicular wall
What is the site of ovulation?
Anywhere on the ovary except in the hilus
What are the neuroendocrine and biochemical mechanisms of ovulation?
- GnRH and LH surge
- Transient progesterone increase
- Collagenase and later aromatase inhibition
- Synthesis of PGF2alpha and PGE2
- Neuromuscular thecal system stimulated by PGF
- Remodeling of follicle layers stimulated by PGE
What are seminiferous tubules?
Major structural unit for spermatogenesis
What is the function of a sertoli cell in relation to spermatogenesis?
Major support for the sperm cell (protection, nourishment etc.)
What is a spermatogonium?
Primary cell (diploid)
What is a function of the leydig cells?
Facillitate steroidogenesis
what is semen?
A liquid cellular suspension containing spermatozoa and accessory gland fluid
What is used to evaluate quality control in semen?
- Sperm concentration
- Sperm/ejaculate number
- Percentage of motile sperm
- Percentage of morphologically normal sperm
What are the stages that sperm go through during their production (Names) in order? Are they diploid or haploid? (2n vs. n)
Spermatogonium (2n) –> Primary Spermatocyte (2n) –> Secondary Spermatocyte (2n) –> Spermatid (n) –> Spermatozoa (n)
What is contained within the head of a sperm cell?
DNA with Protamines
- Nucleus
- Acrosome
- Hydrolytic enzymes
- Postacrosomal
What is the arrangement of the tail of a sperm and what is it used for?
9 + 2 arrangement
Motility
Which hormones have direct control over spermatogenesis?
FSH, LH and Testosterone
Where do the hormones act which control spermatogenesis?
LH –> Receptors in the Leydig cells
FSH –> Receptors in sertoli cells
Testosterone –> Receptors in sertoli cells and synthesized by leydig cells
What hormones are sertoli cells involved with or secrete during spermatogenesis?
FSH receptors
Testosterone receptors
Secretion of Antigen binding protein, inhibin, activin and reductase
