Male Repro Physiology Flashcards
What is a spermatogonium?
An undifferentiated male germ cell
Describe the role(s) of Sertoli cells
Located in the seminiferous tubules of the testes
Nourish and protect the developing spermatocytes
For blood-testes barrier
Produce inhibin-B hormone
Describe the role(s) of Leydig cells
Located in the interstitium between seminiferous tubules in the testes
Produce testosterone
Describe the role(s) of Myoid cells
Surround the basement membrane of the seminiferous tubules in the testes (interstitial cells)
Squamous contractile cells; generate peristalsis
Describe the roles of tight junctions between Sertoli cells
Hold Sertoli cells together
Separate the basal compartment from the luminal compartment of the seminiferous tubule
Protect spermatogonia from the conditions in the luminal compartment
Allow primary spermatocyte to pass through; reforms quickly behind it to minimise communication between the two compartments
Describe the first phase of spermatogenesis
Spermatogonium undergoes mitosis, forming two identical spermatogonia. One of these cells differentiates into a primary spermatocyte, while the other remains as a stem cell.
Describe the process of meiosis in the development of sperm cells
Primary spermatocyte undergoes the first phase of meiosis to produce two secondary spermatocytes
Each secondary spermatocyte undergoes the second phase of meiosis to produce four spermatids (two per secondary spermatocyte).
Describe the genetic content of spermatids
Spermatids are haploid cells; they contain 23 single chromatids
Each is genetically unique
At what temperature must the testes be in order to optimise spermatogenesis?
2° C below body temperature
Give seven factors which affect spermatogenesis
Testes temperature
Endocrine factors e.g. low gonadotrophins/androgens
Loss of blood-testis barrier due to physical damage
Infection e.g. mumps, viruses
Autoimmune reactions
Environmental factors e.g. occupation, pesticides, radiation, smoking, alcohol
Medications e.g. some antihypertensives, antidepressants, chemotherapy
Which part of the nervous system is responsible for causing an erection? Describe this process.
Parasympathetic nervous system
- nerves release acetylcholine
- Ach stimulates release of nitrous oxide from endothelial cells of trabecular arteries
- NO is a vasodilator; acts on smooth muscle of trabecular arteries and penis
- arteries vasodilate; corpora cavernosa fill with blood
- ischiocavernosis and bulbospongiosus contract to maintain the erection
Which part of the nervous system is responsible for causing ejaculation? Which neurotransmitter is involved?
Sympathetic nervous system
- Spinal reflex via the pudendal nerve (S2-S4)
- Noradrenaline
Describe the processes which help to maintain an erection
Compression of veins of the corpora cavernosa by:
- contraction of ischiocavernosus and bulbospongiosus
- engorged erectile tissue also compresses veins
Describe the processes that lead to ejaculation
- Smooth muscle of the vas deferens contracts (peristalsis) to squeeze sperm towards penis
- prostate gland releases prostatic fluid
- seminal vesicles release semindal fluid - Muscles at the root of penis contract to expel the semen from the penis
- bulbospongiosus and pubococcugeus
What makes up the greatest volume of semen?
Seminal fluid; makes up 70-80% of semen
What are the main constituents of prostatic fluid
Alkaline fluid
Proteolytic enzymes
Electrolytes
What hormone is released from the hypothalamus and acts on the pituitary?
Gonadotrophin-releasing hormone (GnRH)
What is the function of Gonadotrophin-releasing hormone (GnRH)?
GnRH stimulates release of FSH and LH from the anterior pituitary gland
Describe the role of luteinising hormone (LH) in males
LH acts on Leydig cells in the testes, stimulating them to produce testosterone
Describe the role of follicle-stimulating hormone (FSH) in males
FSH acts on Sertoli cells in the testes, stimulating them to produce androgen-binding protein (ABP), and Inhibin-B
Describe the functions of testosterone in males
Maintainance of accessory sex glands (e.g. prostate)
Maintains libido
Stimulates bone and muscle growth
Maintainance of male secondary sex characteristics
Acts on Sertoli cells, stimulating them to produce ABP and Inhibin-B
Stimulates spermatogenesis when bound to ABP
Negative feedback on pituitary; inhibits production of LH
Describe the function of ABP
Androgen-binding protein: binds testosterone, forming a complex which stimulates spermatogenesis
Describe the function of Inhibin-B in males
Negative feedback on the pituitary; inhibits production of FSH
