Flashcards in Endo-Repro L12 Male 1 Deck (32)
Containing Sertoli cells and germ cells.
Encircled by myoid cells
Somatic cell lining tubule. Nurse cell required for spermatogenesis
Regulated by FSH
Move sperm along tube by peristalsis
Containing Leydig cells, Lymph vessels and macrophages.
Produces testosterone under control of LH
Spematagonia lie on
The BM → as they mature they move towards the lumen.
Testosterone binds to androgen binding protein mad eby the cell and provides:
1. Physical support
2. Metabolic support (controls migration)
3. Secretes testicular fluid and maintains it
Blood testis barrier
Meiosis occurring and so is protective
Spermatids to spermatozoon.
Leydig cells, macrophages
Sertoli cells and germ cells below the level of the blood-testis barrier (tubule itself)
Sertoli cells and germ cells above the level of the blood-testis barrier (post meiotic cells and more mature.
Purpose of Blood-Testis Barrier: (2)
1. Maintains differences in fluid composition between fluid within tubule and outside tubule.
a. Spermatogeneisis requires particular environment
2. Protects developing sperm from auto-immune attack.
Attacks bottom of head
1. Milieu for developing germ cells and vehicle for sperm transport
2. First produced at sexual maturation ie puberty
3. Blood-testis barrier must be present
4. Fluid is secreted and maintained by Sertoli cells
a. Regulate passage of ions, selective flow of water, steroids and carbohydrates into tubular lumen
Testicular Steroid Production:
Testicular Androgen Synthesis:
1. LH binds to the leydig cell which converts cholesterol to
a. Progesterone → delta 4 pathway leading to testosterone production
b. Androstenediol → delta 5 pathway leading to testosterone production
2. Testosterone can either go:
a. To blood and lymph (male repro tract and accessory organs)
b. Sertoli cell
i. Testosterone converted to DHT via 5 alpha reductase.
i. Testosterone converted to DHT via
5 alpha reductase.
Testicular Oestrogen Synthesis:
• LH initiates testosterone production, which is moved to the sertoli cell
• Aromatase converts testosterone to oestradiol 17beta and the transported into blood and lymph
Other Hormones produced by the testis:
1. Produced by conversion of testosterone via AROMATASE.
2. Produced locally and by peripheral conversion of androgen.
3. Actions unclear but essential for male fertility and spermatogenesis.
4. Important role in fluid reabsorption by the proximal epididymis.
5. Important for development and maturation of male reproductive tract.
Functions of Testosterone: (9)
1. Sex differentiation, growth and development of male genitalia
2. Induce secondary sex characteristics (deep voice, beard, body form, penile growth etc)
3. Support spermatogenesis
4. Induce and maintain accessory sex glands
5. Growth and fusion of long bones
6. Muscle development
7. Metabolic and cardiovascular effects
8. Libido and behavioural effects (males and females)
9. Regulate secretion of LH
Hypothalamic control of gonadotrophin release
1. Pituitary produces luteinising hormone (LH) and follicle stimulating hormone (FSH)
2. Control is by GnRH (pulsatile release 1-3 pulses.h)
3. LH targets Leydig cells
4. Testosterone feedback at pituitary and hypothalalmus (only on LH). Oestrdiol?
5. Levels of LH and testosterone oscillate hour by hour.
6. Changes in LH or FSH output by
a. Alteration of GnRH release
b. Alteration in GnRH sensitivity of gonadotrophs
Testosterone often acts through →
conversion to DHT by 5 alpha reductase enzyme.
Factors affecting LH and testosterone levels:
2. Androgen administration
3. Diurnal rhythm (small effect)
4. Illness or stress
5. Sexual activity
7. Endocrine disorders
Congenital enzyme deficiency: inherited 5-alpha reductase deficiency
1. Wolffian duct differentiation
2. Virilisation of external genitalia