Lecture 5: Male tract and endocrine 1 Flashcards
Glandular functions of the testis?
Exocrine: secretory product - spermatozoa
Endocrine: secretory product - mainly testosterone (+other hormones)
Main cell types in testes?
Gonocytes: Primary germ cells that become spermatagonia
Spermatogonia: germ cells - pre-sperm cells that undergo mitosis
Sertoli cells: epithelial cells - in the lumen of tubule helping development, increase in number during minipuberty (male granulosa cells)
Leydig cells: interstitial cells - produce androgen
myoid cells: contractile cells
Germ cell origin?
NB: We date from the LMP -last menstrual period but embryologist use US or other methods and date from ovulation or conception
PGC - Primordial germ cells can be seen around 3-4 weeks post conception, first in the yolk sac of the extraembryonic tissues and migrate to the gonadal ridges via the hindgut.
Driven by SCF- Stem cell factor and follow enteric nerves. In the absence of SCF they die so if they ‘wander’ too far off the path they will die.
However, sometimes they can be found in the pancreas (where they always form oocytes regardless of the sex) Ectopic germ cells may be the cause of germ cells tumours around the body.
Minipuberty? importance?
A post natal process that changes gonocytes to spermatogonia at 3-9months.
There is a time limited surge of testosterone by leydig cells
- masculinisation of the neonatal brain
- Promoting sertoli cell proliferation (sets up ability to produce the correct large amounts of sperm)
- promotes defferentiation of gonocytes
- may have implications for the timing of orchidopexy
Germ cell tumours?
- These are thought to arise from PGCs
- 93% of GCT are found in the testis
- only 4% are in the ovaries
- and 3% are ectopic (most common in the CNS)
Leydig cells? Fetal and adult differences?
Androgen producting cells - In adults and fetuses = Testosterone
Initial production by embryonic leydig cells is not dependent on stimulation.
Approx 14 weeks gestation production of testosterone becomes LH(pituitary) and hCG(placenta) dependent.
Embryonic legdig cells are derived from different progenitors than adult leydig cells. The adult leydig cells come from stem cells at puberty and require LH stimulation.
Sertoli cells, features and role?
- Line the inside of seminiferous tubules
- nourish spermatogonia
- resorb excess cytoplasm -the residual body
- produce seminiferous tubule fluid - v. important
- maintain the spermatogonial stem cell niche (stem cells will die in the absence of sertoli cells)
The sperm production is proportional to sertoli cell number and does not increase after puberty has finished…
Blood-testis barrier?
There are no BV in the seminiferous tubules and the sertoli cells form TJ that only allow spermatogonia to pass though. They also have some unknow method of stopping an immune reaction on top of their barrier function.
Central tolerance to our own antigens occurs during fetal life and so this barrier is vital to stop anti-spem anitbodies.
Moving testes?
Two phases:
- Transabdominal (10-15 weeks)
- The inguino-scrotal (25-35weeks)
As the embryo grows the gubernaculum does not elongate and under the influence of testosterone the caudal ligament regresses.
Androgen is important for the second phase where they descent through the inguinal canal
Cryptorchidism?
Failure of the testis to descend
- Unilateral or bilateral
- complete of incomplete
Incomplete
- Maldescent - to ant. abdo walll, perineum, or thigh = ectopic)
- 1-9% at full term and 30% of premature
- incidence varies massively
- most self-correct in 3 months or surgery needed
Importance of cryptorchidism? Ethnicity differences?
- Can lead to infertility due to excess temperature
- Is a known risk factor for testicular cancer (3-4 fold increase)
- breast-feeding infants are less likely to remain cryptorchid
Maori boys have a 20% higher chance than european and NZ pacific and asain boys have a lower risk. These trends mirror those of testicular cancer.
