Basic Male reproductive physiology Flashcards
What are the male reproductive organs? (7)
- Penis
- Testes
- Scrotum
- Epididymis
- Vas deferens
- Prostate
- Seminal vesicles
Where is sperm produced?
Sperm is produced from the primordial germ cells present in the semineferous tubules within the testicles
Where is sperm stored?
In the Epididymis - sperm remains here for about 3 months and matures before travelling out
What is the Epididymis connected to?
The tail of the epididymis merges into the vas deferens
- These then pass through the inguinal region and curls back round the bladder
Which 2 structures create the semen fluid which is mixed with the sperm?
Seminal vesicle and prostate
The vas deferens join with the seminal vesicle to form what?
The ejaculatory duct which passes through the prostate and empties into the urethra.
Why do the testicles sit outside of the main body cavity?
Testicular temperature must be below that of the body temperature in order to facilitate sperm production properly.
The scrotum sit outside the abdominal cavity and allow about 1-2ºC lower temp than the abdominal cavity
Normal process of ejaculation: see diagram
What is the name given to the fibrous capsule that surrounds the testes?
Tunica albuginea
Features of the Tunica albuginea
It penetrates into the structure of the testes dividing it into several tubules - the semineferous tubules lie in between these
What are the 3 different types of cells within the semineferous tubules?
- Germ cells - immature sperm - become mature
- Sertoli/sustentacular cells - situated between germ cells and support sperm production
- Interstitial (Leydig) cells - produce testosterone
Describe the process of endocrine control of testicular function
- Gonadotrophin releasing hormone released from the hypothalamus
- GnRH acts on anterior pituitary to release FSH and LH (gonadotrophins)
- FSH acts on testicles - stimulating the Sertoli cells, which facilitate spermatogenesis.
- LH acts on testes - stimulating Leydig cells, to produce testosterone
Negative feedback loop in endocrine control of hormones
As testosterone production increases it creates a negative feedback loop – sends negative signal to the hypothalamus to reduce secretion of GnRH and subsequently decrease in release of gonadotrophins
Inhibin is produced by the fertilised cells and again it creates a negative feedback on the anterior pituitary
When does spermatogenesis start?
At puberty
How long is the average sperm cycle?
64 days from production to ejaculation - in which the germ cells pass through different developmental stages
What are the 2 distinct phases during spermatogenesis?
- Spermatocytogenesis - Clonal expansion (replicate and multiply) and maturation through mitotic and meiotic process
- Spermiogenesis - differentiation into mature sperm cells
Describe Spermatocytogenesis - 1st phase of spermatogenesis
- Involves 2 cell types:
- Spermatogonia A - used to replenish the pool of spermatogonia. This replenishment of spermatogonia means that males are fertile throughout adult life.
- Spermatogonia B will eventually form mature sperm.
- Type B spermatogonia replicate by mitosis several times to form identical diploid cells linked by cytoplasm bridges, these cells are now known as primary spermatocytes.
Primary spermatocytes then undergo meiosis.
- Meiosis I produces two haploid cells, known as secondary spermatocytes
- Meiosis II produces four haploid cells, known as spermatids
Spermiogenesis - 2nd phase of spermatogenesis
- The cytoplasmic bridges break down and the spermatids are released into the lumen of the seminiferous tubule – a process called spermiation.
- The spermatids mature into sperm as they travel along the seminiferous tubules until they reach the epididymis (here they are stored and undergo the final stages of maturation)
Chromosomal division during spermatogenesis
Diploid chromosomes (46) before and after mitosis in 1st phase of spermatocytogenesis
Then undergoes meiosis in 2nd phase of spermatocytogenesis - here 2 haploid cells are produced - chromosome number halves (23)
2nd meiotic division - 4 haploid cells with 23 chromosomes each
What factors affect spermatogenesis and as a result can affect male fertility?
- Pretesticular - Problem with the hormonal control
- Functional- excessive weight loss, gain, stress
- Intracranial tumours, cysts, bleed
- Prolactinoma
- Medications- opiates, external testosterone, steroids(body building)
- Genetic- Kallmann’s syndrome
- Testicular - Problem at the site of production
- Surgery- orchidectomy, orchidopexy
- STI – affect reproductive system
- Mumps orchitis
- Testicular trauma or torsion
- Radiotherapy or chemotherapy
- Genetic- Klinefelter’s (46 XXY), Y-chromosome microdeletion
What is Orchidoplexy?
Replacing a maldecended teste
Steps to reduce the impact of factors affecting fertility
- Improve lifestyle - normal BMI, stop smoking, alcohol in recommended limits, healthy diet, exercise, adjustments to occupational exposure
- Optimise underlying medical condition
- Stop medications or switch to alternative pregnancy compatible medications
- Reduce STI risk and treat promptly if diagnosed.
- Fertility preservation- sperm freezing prior to surgery or cancer treatment
