Session 1 Flashcards
What are the components of the male internal genitalia?
Testes Duct system (vas deferens, epididymis) Seminal vesicles Prostate gland Bulbs-urethral glands
What are the components of the female internal genitalia?
Ovaries Duct system (Fallopian tube, uterus, cervix, vagina)
What are the components of the male external genitalia?
Penis
Scrotum
What are the components of the female external genitalia?
Vagina Vestibule Labia minora Labia majora Clitoris
Give examples of secondary sex characteristics in males.
Increased body size (rel to ♀) Body composition & fat distribution Hair & skin Facial hair Male pattern baldness Central nervous effects Smell
Give examples of secondary sex characteristics in females.
Smaller body size (rel to ♁) Subcutaneous fat distribution Hair & skin Breast development Central nervous effects
What tissues give rise to the indifferent gonads?
Intermediate mesoderm
Primordial germ cells (extragonadal)
Where do the primordial germ cells arise?
Yolk sac (they migrate into the retroperitoneum along the dorsal mesentery)
Why are the primordial germ cells separated from the somatic cell line so early in development?
To prevent them from differentiating
Which gene is responsible for the development of the male and where is it found?
SRY gene found on the Y chromosome
Absence of a Y chromosomes drives the development of the female
What is the name given to the thick outer covering of the male gonad, that is not present in the female?
Tunica albuginea
What are the mesonephric and paramesonephric ducts also known as?
MND: Wolffian duct
PMND: Müllerian duct
During development, what is the name of the structure that marks the end of the urinary, reproductive and gastrointestinal tracts?
Cloaca
Which germ layers contribute to the formation of the vagina?
Upper 1/3: intermediate mesoderm
Lower 2/3: Endoderm
In an XY embryo, what supports the development of the mesonephric (Wolffian) duct?
Androgen secreted by the testes
In an XY embryo, what causes the degeneration of the paramesonephric (Müllerian) duct?
Müllerian inhibitory substance secreted by the testes
Explain the effects of gonadal hormones on the XX embryo.
Ovaries develop
No androgen produced, hence the Wolffian ducts degenerate
No Müllerian inhibitory substance produced, hence the Müllerian ducts develop
What are the basic components of the external genitalia during the indifferent stage?
Genital tubercle
Genital folds
Genital swellings
What drives the masculinisation of the external genitalia?
Testis-derived androgen (dihydrotestosterone)
Approximately how many gametes will a female produce in her lifetime?
400
Approximately how many gametes will a male produce per day?
200 million
After meiosis 1 and 2, how many mature oocytes are present?
1 (the other three daughter cells become polar bodies)
In what three ways can genetic variation occur?
Crossing-over
Random segregation of chromosomes among four gametes
Independent assortment
What important role does the blood-testis barrier (Sertoli cell barrier) perform?
Prevents an autoimmune response against sperm (which all possess different DNA)
What are spermatogonia?
Male germ cells (the raw material for spermatogenesis)
When a spermatogonium undergoes mitosis, what two daughter cells are produced?
Ad spermatogonium (for maintaining stock) Ap spermatogonium (gives rise to primary spermatocytes)
What is the name given to the release of spermatids into the lumen of the seminiferous tubules?
Spermiation
Through which structures does the remodelling of the spermatids occur?
Seminiferous tubule
Rete testis
Ductili efferentes
Epididymis (at this point fully-formed spermatozoa are present)
Before reaching the epididymis the spermatids are non-motile. How are they transported along the lumen?
Transport via Sertoli cell secretions assisted by peristaltic contractions
What are the main constituents of semen?
Seminal vesicle secretions (AAs, citrate, fructose, prostaglandins)
Prostate secretions (Proteolytic enzymes, zinc)
Sperm (via the vas deferens, ~200-500 million per ejaculate)
Bulbourethral gland secretions (Mucoproteins for lubrication and to neutralise acidic urine in distal urethra)
When sperm is subjected to conditions in the female genital tract, sperm capacitation occurs. What does this involve?
Removal of glycoproteins and cholesterol from the sperm membrane
Activation of sperm signalling pathways
This allows the sperm to bind to the zone pellucida of the oocyte
What is the relevance of sperm capacitation in IVF?
Sperm must first be incubated in capacitation media in order for it to become fertile, as it is not exposed to the condition of the female genital tract.
While the majority of oogonia continue to divide by mitosis, some will enter meiosis, at the end of the third month of gestation. At what meiosis stage will the process arrest and what are these cells now called?
Prophase of meiosis I (these cells are the primary oocytes)
What is the name of the process by which many oogonia and primary oocytes degenerate?
Atresia
What is the name given to a primary oocyte and its surrounding layer of follicular cells?
Primordial follicle
What are the three stages of oocyte maturation that occur from the onset of puberty?
- Preantral
- Antral
- Preovulatory
What changes occur during the preantral stage of maturation?
Follicle cells surrounding the oocyte become cuboidal (from flat) and proliferate to form a stratified epithelium of granulosa cells.
The granulosa cells secrete a glycoprotein layer around the oocyte to form the zona pellucida
What is the antrum that forms during the natural stage of maturation?
The coalescence of fluid-filled spaced that form around the granulosa cells.
What are the names of the cells that surround the oocyte?
Cumulus oophorus
What are the two layers that surround the newly-formed secondary follicle during the antral stage?
Inner secretory layer (theca interna)
Outer fibrous layer (theca externa)
A surge in which hormone induces the preovulatory growth phase, and where is the hormone released from?
LH
Anterior pituitary gland
When meiosis I is completed during the preovulatory phase, why are the two haploid cells of unequal size?
One cell receives most of the cytoplasm while the other receives almost none (becoming the first polar body).
At what stage of meiosis II is division halted during the preovulatory phase?
Metaphase (~3 hours before ovulation)
When is meiosis II completed in the oocyte and why does this not always take place?
Meiosis II is only completed if the oocyte is fertilised. If fertilisation does not take place the oocyte will not complete meiosis II and will degenerate ~24 hours after ovulation.
Which two hormones are responsible for the rapid growth of the follicle several days before ovulation?
FSH
LH
What is the name given to a mature follicle?
Graafian follicle
Other than stimulating the growth of the follicle, what other function does LH provide during ovulation?
Increases collagenase activity aiding the extrusion of the follicle from the ovary.
How does the corpus luteum form?
Granulosa cells and the theca interna become vascularised.
A yellowish pigment is produced and the cells become lutein cells.
What is released by the corpus luteum?
Oestrogen
Progesterone
What effect does oestrogen and progesterone have on the uterine mucosa?
Stimulates uterine mucosa to enter secretory stage in preparation for embryo implantation.
If no fertilisation occurs, after how long will the corpus luteum die?
~14 days
How is the oocyte transported from the ovary?
Carried into the Fallopian tube by sweeping movements of fimbriae and motion of cilia on the epithelial surface.
Subsequently propelled by peristaltic muscular contraction of the tube.
If fertilisation has not occurred and the corpus luteum degenerates, what is the name of the mass of fibrous scar tissue it forms?
Corpus albicans
After fertilisation has taken place, what is released by the embryo that prevents the degeneration of the corpus luteum?
Human chorionic gonadotropin
At what stage of gestation is the placenta able to provide adequate progesterone, overtaking the corpus luteum?
~4 months
