Male Reproduction Flashcards
What cells do sperm arise from?
Spermatogonial stem cells
Where does mitotic division occur in sperm production?
Basal layer of sertoli cells in the seminiferous tubules in the testis
How many chromosomes to spermatogonia have?
46
What happens to the residual body of a sperm?
It is phagocytosed by the sertoli cells
What do the seminiferous tubules run into?
The rete testis
What is an orchidectomy?
Removal of a testis
What occurs if the testes do not descend to the scrotum?
Cryptorchidism
What does the rete testis run into?
The epididymis
What does the epididymis run into?
The vas deferens
What occurs in the epididymis?
Sperm acquire the ability to be motile and fertilise.
Excess fluid is also reabsorbed making the sperm 100x more concentrated
How long to sperm spend in the epididymis?
10-14 days
What is the ampulla?
Wider region of vas deferens which contains very concentrated sperm storage
How long can sperm be stored in the vas deferns?
Several months
What is the function of the seminiferous tubules?
Produce sperm
Where are the seminiferous tubules located?
The testes
What is the name of the cell in which a sperm first starts to be made?
Sertoli cell
What is found outside of the seminiferous tubules?
Leydig cells
At what stage in life does spermatogenesis begin?
After puberty
How much does the average testis weigh?
18g
How many sperm does the average male produce per second?
300-600 sperm per gram of testis tissue per second
What are the 3 stages of spermatogenesis?
Mitosis, Meiosis, Cytodifferentiation
What occurs during stage 1 of spermatogenesis?
Stage 1: Mitosis. A spermatogonial stem cell (2n) divides to produce 1 daughter cell (2n) and 1 spermatogonial stem cell. The daughter cell then migrates through the tight junctions of Sertoli cells into the adluminal compartment of the seminiferous tubule, where is is called a primary spermatocyte
What occurs during stage 2 of spermatogenesis?
Stage 2: Meiosis. The primary spermatocyte’s DNA content doubles (still 2n), and Meiosis 1 occurs, resulting in 2 secondary spermatocytes (n). Meiosis 2 occurs, producing 4 spermatids (n)
What happens in stage 3 of spermatogenesis?
Stage 3: spermiogenesis/cytodifferentiation. Round spermatids form a tail, midpiece, and head. Spermatozoa are found in the lumen of the seminiferous tubules
What are the names of the cells as they progress through spermiogenesis?
Spermatogonium -> primary spermatocyte -> secondary spermatocyte -> spermatids -> spermatozoa
What is the name of the sack on a sperms head and what is its function?
Acrosome, contains enzymes to help sperm penetrate oocyte
In males, what does LH act on and what is its effect?
LH acts on Leydig cells in the testes and causes testosterone to be produced.
What is the effect of testosterone released from leydig cells?
Testosterone travels through the blood and can become dihydrotestosterone, which result in secondary sexual characteristics. Testosterone also acts on sertoli cells to produce sperm
What are some of the common secondary sexual characteristics in males?
Aggressiveness
Libido
Hair growth
Baldness
Enlarged testicles
What is the effect of FSH on Sertoli cells?
Causes Sertoli cells to produce ABP (androgen binding protein) which allows testosterone (released from the leydig cells) to travel around the body
How is testosterone production controlled?
Testosterone travels to the hypothalamus to downregulate the production of GnRH. It can also turn of the production of FSH and LH in the anterior pituitary. (Negative feedback loop).
What does kisspeptin do?
Stimulates the hypothalamus to release GnRH
How is ABP production regulated?
Sertoli cells produce inhibin which regulates FSH production in the anterior pituitary
What is the name of the protein that stimulates the hypothalamus to release GnRH?
Kisspeptin
What is the incidence of male infertility?
1 in 6 men
What are the 2 treatments for male infertility?
IVF and ICSI
What is reduced sperm count known as?
Oligospermia
What is a common feature of male infertility?
Reduced sperm count - <20 million/ml
What is no sperm in ejaculate known as?
Azoospermia
How many sperm are required for IVF?
50,000 motile sperm
What does IVF stand for?
In vitro fertilisation
What does ICSI stand for?
Intracytoplasmic sperm injection
Where are the testes located?
The scrotum
What is the removal of a testi
called?
Orchidectomy
At what stage in life do the testes move from the pelvis to the scrotum?
During pregnancy
What is the incidence of cryptorchidism?
3%
What is it called if the testes do not descend into the scrotum?
Cryptorchidism
What is the result of cryptorchism?
Infertility and prone to testicular cancer
Describe the path of sperm from the seminiferous tubule
Seminiferous tubule -> rete testis -> epididymis -> vas deferens -> ejaculatory duct
How many seminiferous tubules are found in each testis?
~80
What are the 4 main ducts apart of the male reproductive tract?
Epididymis
Vas deferens
Ejaculatory duct
Urethra
How long is the urethra?
20cm
How long is the vas deferens?
45cm
What structures join into the ejaculatory duct?
Vas deferens, bladder, seminal vesicles
What are the 2 accessory glands of the male reproductive tract?
Seminal vesicles & prostate
Describe the substance produced by the seminal vesicles
Mucoid, sticky, alkaline, contains fructose, prostaglandins and clotting proteins
What do the seminal vesicles do?
Secrete a substance into the ejaculatory duct which washes the sperm down the urethra
What do the clotting proteins in seminal fluid do?
Allow the sperm to ‘stick’ inside the female so it is not removed during intercourse.
What shape and size is the prostate?
Donut shaped, golf ball sized
What does the prostate secrete, and when?
Prostatic fluid, before of sperm during ejaculation
What does prostatic fluid do?
Breaks down the coagulum in the female so the sperm isn’t stuck forever and can swim to the oocyte
What is the pH of semen?
7.5
Describe prostate fluid
Slightly acidic (6.5), milky coloured, contains citrate, phosphate, calcium and prostate-specific antigen (PSA)
How many sperm does normal human ejaculate contain per ml?
20 million
Describe the makeup of semen (in order of it’s exit from the penis)- including approximate percentages
30% prostatic fluid
10% sperm
60% seminal vesicle fluid
What percentage of men’s cancer mortalities does prostate cancer contribute?
29%
What does BPH stand for, and what is it?
Benign prostate hyperplasia - overgrowth of the prostate tissue
What are the 2 5-alpha reductase inhibitors, and what are their half-lives?
Finasteride - 5-7 hours
Dutasteride - 5 weeks
What occurs as a result of BPH?
Weakening of the bladder as urethra is occluded
Urinary infections
Kidney problems
What is the approximate volume of human ejaculate?
2-5mls
What is the incidence of BPH?
90% of men over 85yrs
What are the 2 treatments for BPH?
- Surgery
- Selective 5-alpha-reductase inhibitors - stops prostate from enlarging by stopping testosterone from converting to dihydrotestosterone
What do prostate screening tests detect?
Prostate-specific antigen (PSA)
What are the 3 major structures of the penis?
Corpora cavernosa (x2)
Corpus spongiosum
Penile urethra
What are the 4 treatment methods for prostate cancer?
Watchful waiting (detect and monitor closely)
Androgen depletion (5 alpha reductase inhibitors, castration, inhibitors of androgen synthesis)
Inhibition of testosterone action (block androgen receptor)
Surgery - prostatectomy
What are the corpora cavernosa?
The main erectile tissue which fills with blood
Describe the corpus spongiosum?
Surrounds the penile urethra and prevents it’s occlusion during an erection. Also fills with blood during an erection.
Does the corpora cavernosa lie dorsal or ventral to the corpus spongiosum?
Ventral
Release: what 2 things cause smooth muscle relaxation in the corpora cavernose?
NO and prostaglandin E1
How much more blood does an erect penis contain compared with a flaccid penis?
8x more
What is the name of the secondary messenger that contributes to the relaxation of the smooth muscle in the corpora cavernosa, and what does it do?
Guanosine monophosphate (cGMP) - reduces intracellular calcium
What is the name of the enzyme that breaks down GMP? What does the breakdown of GMP lead to?
Phosphodiesterase - leads to less relaxation so no erection.
What does Viagra do (at the molecular level)?
Inhibits phosphodiesterase (type 5) so that GMP is not broken down and arteries in the corpora cavernosa remain relaxed, allowing an erection to occur.
What enzyme converts testosterone to 5 alpha dihydrotestosterone?
5 alpha reductase
During which decade of life will the incidence of Benign prostatic hyperplasia (BPH) be approximately 35%?
70-79
During which decade of life will the incidence of Benign prostatic hyperplasia (BPH) be rare?
Under 40
During which decade of life will the incidence of Benign prostatic hyperplasia (BPH) be approximately 27%?
60-69
During which decade of life will the incidence of Benign prostatic hyperplasia (BPH) be approximately 17%?
50-59
What is the incidence of BPH at ages 50-59?
17%
What is the incidence of BPH at ages 60-69?
27%
What is the incidence of BPH at ages 70-79?
35%
What branch of the autonomic nervous initiates and maintains an erection?
Parasympathetic
What is one enzyme that the acrosome of a sperm cell contains?
Hyaluronidase
