Module 10: Reproduction and Development II Flashcards
What are the three components of the male reproductive system?
- Testis
- External genitalia
- Internal genitalia
What 2 structures comprise the external genitalia of the male reproductive system? Describe their components.
-
Penis
- Urethra: the hole
- Erectile tissue
- Corpus spongiosum: keeps urethra open
- Corpora cavernosa: erection
- Glans, prepuce (foreskin): removed for hygiene, cancer, STI, UTI, HIV
- Scrotum: the external sac testes migrate into
Why is the scrotum outside of the body? What happens if it isn’t?
Sperm development requires temp 2-3 o F lower than body temperature, so must be outside the body. Failure to descend is known as cryptorchidism (usually resolves itself in 1st year)
- Unable to produce sperm but do still produce androgens
- Moved to scrotum with testosterone treatment or surgically
- If the testes aren’t moved from inside the body, they will become infertile
What are the two key components of the male internal genitalia?
- Accessory glands
- Vas deferens
What are the 3 male accessory glands?
- Seminal vesicle: empty secretions into the urethra
- Prostate gland
- Bulbourethral gland: empty secretions into the urethra
Which hormone is involved in prostate development? What class of drugs can inhibit this and shrink the prostate if needed? What has clinical data shown about this treatment?
DHT. Administration of 5a-reductase inhibitor (finasteride) blocks DHT production, shrinks hypertrophied prostate. There was a 30% reduction in less malignant forms of prostate cancer.
What is androgenic alopecia? What is a side effect of finasteride treatment?
Androgenic alopecia: decreased hair growth due to the presence of androgens (DHT shrinks hair follicles).
There is increased hair growth as a result of taking finasteride, as it inhibits DHT production.
What are the 3 main structures in and around the testis? What are each of their roles?
- Seminiferous tubules: sites of sperm production
- Epididymis: carries sperm from the seminiferous tubule to the vas deferens
- Vas deferens: carries sperm to urethra
How many seminiferous tubules are there per testicle? What percent of the testicular mass are they? What is their length?
400-600. 80% of mass. 0.3-1 meter each.
How many compartments are there per testicle?
250-300.
What arrangement do spermatocytes within the seminiferous tubules adopt? What other cells lie between?
Developing spermatocytes stack in columns from outer edge to lumen with Sertoli cells between each column.
What are the 4 roles of the Sertoli cells?
- Contain tight junctions with adjacent Sertoli cells forming a blood-testis barrier between tubule lumen and interstitial space (heavily controlled)
- Regulate sperm development
- Provide sustenance or nourishment to spermatocytes and spermatogonium (termed “sustentacular cells”)
- Produce a variety of substances
What 4 substances do Sertoli cells provide?
- Hormones (activin & inhibin)
- Growth factors
- Enzymes
- Androgen binding protein (ABP)
What is the role of androgen binding protein? What would happen if it was not present?
Binds to testosterone to keep it in the tubule lumen (needed for spermatogenesis). Otherwise it would freely enter and exit the lumen.
Interstitial tissue with _____ and _____ (primary hormone producing cells) lie between seminiferous tubules
Blood vessels, Leydig cells
Germ cells (spermatogonium) reside just inside the _____ of seminiferous tubules. Some remain here undergoing mitosis to produce more germ cells, some enter meiosis to become _____
Basal lamina, primary spermatocytes
As spermatocytes differentiate to sperm, they move towards the _____
tubule lumen
_____ break and reform around the migrating spermatocytes as they move towards the lumen, differentiating into sperm.
Sertoli tight junctions
Once reaching the lumen, how many spermatids are formed from the initial spermatogonium?
4
As spermatids develop into sperm, where are they located as they complete the transformation? What 4 things does this transformation include?
They are embedded in the apical membrane of Sertoli cells while they complete transformation.
Transformation includes:
- Chromatin condensation
- Microtubule extension (flagellation)
- Acrosome, forms a cap over the nucleus (contains enzymes needed for fertilization)
- Mid piece: contains mitochondria for energy
The process of spermatogonium changing to free sperm is about _____ days with _____ produced/day.
- 200 million
Do the sperm mature fully in the Sertoli cells? What is the mechanism?
No. The cells are released from Sertoli cells before reaching maturity. They are pushed out of tubule lumen by other developing sperm and bulk flow of other fluids, and mature in the epididymis (epididymal cells secrete proteins) during 12 or so days of transit time.
Which two gonadotropins are required for spermatogenesis and what are their roles? What additional hormone is required and what is is produced by?
- Follicle stimulating hormone (FSH): binds to receptors on Sertoli cells causing them to generate paracrine molecules needed for spermatogonia mitosis and spermatogenesis
-
Lutenizing hormone (LH): targets the interstitial Leydig cells resulting in production of testosterone
- Actions appear to be through Sertoli cells but exact mechanism not completely understood
What hormone signals spermatogenesis? What 3 things inhibit this signal?
GnRH is released in a pulsatile manner and signals spermatogenesis.
- Excess FSH inhibit the neurons in the anterior pituitary that release them
- Excess LH inhibit the neurons in the anterior pituitary that release them
- Testosterone is the main GnRH inhibitor (acts on GnRH or kisspeptin neurons)
Sperm is joined by what when it enters the vas deferens? What is this mixture known as?
Sperm leaving via vas deferens are joined by the secretions of accessory glands (seminal vesicle, prostate and bulbourethral), the resulting mixture is known as semen, a liquid medium for delivering sperm (99% accessory). Also protect reproductive tract from pathogens ascending urethra (IG’s, lysozyme)
What are the 5 accessory gland secretions in semen?
- Nutrients
- Buffers for protection against acidic vaginal environment and residual acidic urine in urethra
- Chemicals to increase sperm motility
- Prostaglandins (motility and contraction of male and female reproductive tracts)
- Immunoglobulin’s, lysozyme and other antibacterial compounds (prevent infections)
What are primary sex characteristics? What are they influenced by?
Primary sex characteristics (structural differences between genetic males and females): internal sexual organs and external genitalia, which are differentiated to male during embryonic development by androgens and their growth after puberty is also due to androgens.
What are secondary sex characteristics? What influences them?
Secondary sex characteristics: body shape, facial and body hair growth, muscular development, thickening of vocal cords (lowering of voice) and behavioral effects i.e., sex drive (libido), maybe anger and aggression as well. Influenced by androgens.
Androgens are anabolic hormones and promote _____. What is the mechanism?
Protein synthesis. They act on DNA to promote transcription.
Female reproduction occurs in a _____ fashion.
Cyclical.
The female external genitalia is collectively referred to as what? What are the 4 parts?
It is collectively referred to as the vulva or pudendum.
- Clitoris: erectile and sensory tissue
- Labium minus and majus: protective function, similar to scrotum
- Vagina: leads to uterus (womb)
- Hymen: membrane that covers the vaginal opening
The _____ is where a fertilized egg implants and develops during pregnancy
Uterus
What is the opening to the uterus?
The cervix
What are the three layers of the uterus?
- Perimetrium: thin outer connective tissue layer
- Myometrium: thick layer of smooth muscle
- Endometrium: inner layer
_____ ensure eggs released from ovary enters fallopian tube. Why is it neccessary?
Fimbriae. The fallopian tube is not connected to the ovary.
What are the 4 stages of follicular development? Which enters the menstrual cycle? How long does the entire process last?
- Primordial follicle
- Primary follicle
- Secondary follicle
- Tertiary follicle (enters the menstrual cycle)
This entire process takes one year, with the tertiary to dominant (days 7-14) or atresia (days 1-7) step taking 14 days total
What does a secondary follicle develop to become tertiary? What is its role?
An antrum. The antrum functions as storage of enzymes, hormones, growth factors and regulatory factors needed for oocyte maturation, ovulation and fertilization.
What are the 3 phases of the ovarian cycle? What happens in each phase?
- Follicular phase: marked by follicular growth, most variable 10 days to 3 weeks
- Ovulation: once one or more follicles have ripened, the ovary releases oocyte(s) during ovulation
-
Luteal phase (post ovulatory phase): ruptured follicle transforms to corpus luteum (yellow), named for yellow pigment and lipid deposits.
- Secretes hormones, ceases to function after two weeks
Early to mid-follicular phase
The release of _____ causes several tertiary follicles to mature.
FSH.
Early to mid-follicular phase
What two cells are activated on the follicle? What are they activated by and what do they produce?
- Granulosa cells: activated by FSH, produces AMH and estrogens
- Thecal cells: activated by LH, produces androgens
Early to mid-follicular phase
Androgens produced by the thecal cells are converted to _____ in granulosa cells
Estrogens
Early to mid-follicular phase
Which hormone prevents additional follicle recruitment?
AMH
Early to mid-follicular phase
Estrogen is _____ feedback anterior pituitary, _____ on granulosa cells. What does this allow?
Negative, positive. This allows continued estrogen production even with slight suppression of GnRH and LH.
Late follicular phase and ovulation
Release of which hormone peaks from follicles?
Estrogen
Late follicular phase and ovulation
What happens to the follicles during this phase? What do the granulosa cells begin to release?
Some follicles undergo atresia, dominant follicle persists, and granulosa cells now begin to also release progesterone and inhibin
Late follicular phase and ovulation
Persistently high estrogen causes what to occur regarding the hypothalamus? What does this cause?
Persistently high estrogen flips to positive feedback on hypothalamus, causing LH to surge to a higher degree than FSH (inhibited by inhibin)
Early to mid-luteal phase
Both thecal and granular cells transform into which cells? Which hormone directs this change?
Luteal cells, directed by LH.
Early to mid-luteal phase
Inside the luteal cells, what two “energy sources” accumulate? Where do they accumulate in the cell? What does the luteal cell begin to secrete?
Lipid droplets and glycogen granules accumulate in cytoplasm and the luteal cell begins to secrete progesterone
_____ and _____ levels steadily rise during the early to mid luteal phase and provide _____ feedback to hypothalamus and anterior pituitary
Estrogen, progesterone, negative
Early to mid-luteal phase
_____ (dominant during luteal) continues to influence endometrium (secretory) in preparation for pregnancy
Progesterone.
What happens to the corpus luteum if pregnancy does not occur? What happens to the levels of estrogen, progesterone, LH and FSH? What does this cause in the body?
If pregnancy does not occur, spontaneous apoptosis, to become corpus albicans. Progesterone and estrogen fall, FSH and LH increases. Maintenance of endometrium depends on progesterone, when it decreases, vessels in surface contract causing surface cells to die. About 14 days after ovulation, 2 days after corpus luteum ceases function menstruation begins
