Reproductive Flashcards
What is the role of the human male ?
The male human has two major roles with respect to the physiology of reproduction
- manufacturing of sperm (spermatogenesis)
- depositing of Sperm(ejaculation)
Summarize the effects 9f gonadotropin releasing hormone(GRH)?
GRH- a hypothalamic hormone stimulates pituitary hormone lutenizing hormone or FSH
LH targets gonads for androgen production
FSH- targets gonads for follicle maturation, spermatogenesis)
What does dopamine do as a Anterior pituitary hormone?
Dopamine( release inhibitor)
Pitutary target cell hormone: lactotrope
Pituitary hormone: prolactin
Target organ (effects): mammary glands (milk production and letdown)
When is the gonadotrophic axis active?
Before birth and becomes quiescent after parturition, it remains so until puberty
What are the functions of GnRH?
Pulsatile allows for normal reproductive activity. Continued release desensitizes gonadotrope receptors—> decrease FSH & LH
What is the function of FSH?
Develops follicles in the ovaries and regulates spermatogenesis in the testis
What is the function of LH?
Causes ovulation and litenization of ovulated follicle in the ovary of the female and stimulates production of estrogen and progesterone by the ovary. In the male LH stimulates the cells of the testis to produce and secrete testosterone
Where are leydig cells located?
In the testis vascular interstitium produce testosterone
When are leydig cells first active?
In the fetus when testosterone is needed for development of male characteristics, then become inactive until puberty with resumption of lutenizing hormone
What is the effect of DHT and testosterone in the fetus?
Develops male sexual organs
Testosterone -differentiation internal male genital tract (epidydimys, vas deferens, seminal vesicles);
DHT- (testosterone activated to dihydrotestpsterone (DHT) by 5a-reductase in some tissues)- differentiation external male genitalia (penis, scrotum and prostate gland)
-promotes descent of Testes
In most target tissues testosterone is converted to the biologically active derivatives I) DHT by 5 a-reductase and II) estradiol by aromatase
DHT high binding affinity for androgen receptors and is - 2-3 times more potent than testosterone
Describe testosterone
Secreted from leydig cells, it exerts negative feedback on both the hypothalamus to decrease GnRH and the anterior pituitary to decrease both LH and FSH. There is even some evidence to suggest that there may be additional feedback to higher brain centers that can affect axis control
Testosterone also stimulates Sertoli cells to release inhibin
Describe inhibin
Inhibin B provides negative feedback to the anterior pituitary in males, where it decreases secretion of FSH. Sertoli cells also produce activin and follistatin that regulate the secretion of FSH
What is the effect of testosterone on bone?
Increased growth of bone and connective tissue
What is the effect of testosterone on muscle ?
Increased growth of muscle and connective tissue
What is the effect of testosterone on reproductive organs?
Increased growth and development by Testes, prostate, seminal vesicles, and penis
Increased growth of facial, axillary, and pubic hair
Increased growth of larynx
Increased spermatogenesis
What is the effect of testosterone on skin ?
Increased sebaceous gland size and secretions
Summarize the process of spermatogenesis
- mtitotic divisions of spermatogonia (stem cells) which generate the spermatocytes —> ultimately become mature sperm
- two meiotic divisions of spermatocytes - which decrease the chromosome number—> haploid spermatids(N=23). Each primary spermatocyte yields 4 sperm
- Spermiogenesis in which spermatids differentiate into spermatozoa, they lose cytoplasm and develop flagella and are transformed to mature sperm
What is the function of seminiferous tubules?
Produce sperm in avascular tubules of the Testes
As spermatogonia move from the outer edge to the lumen of the tubule as they are converted into spermatozoa
The process takes approximately 64 days
What are the types of cells in seminiferous tubules?
Two types of cells: spermatogonia, Sertoli cells
Sertoli cells between columns of spermatocytes (extend from basal lamina to lumen)
Adjacent Sertoli cells linked by ‘tight junctions’ (blood testis barrier)
Explain Sertoli cells
Sertoli cells are connected by tight junctions, which divide the intracellular space into a basal compartment and an adluminal compartment
- Spermatogonia are in the basal compartment and maturing sperm in the adluminal compartment
- Spermatocytes are formed from the spermatogonia and cross the tight junctions into the adluminal compartment, they mature into spermatozoa
- Sertoli cells- nourishment for the sperm, fluid to transport sperm, forms tight junctions with each other creating blood-testis barrier, synthesize and secrete androgen binding proteins and inhibin B
What are the actions of LH on leydig cells?
Stimulates leydig cells to secrete testosterone by stimulating the enzyme cholesterol desolate (first step in steroid organic pathway)
What are the actions of FSH on Sertoli cells ?
FSH binds to receptors on the Sertoli cells and stimulates spermatogenesis and Sertoli functions
FSH causes the Sertoli cells to secrete inhibin which has a negative feedback on the anterior pituitary for FSH
Summarize testosterone and DHT for adulthood
Throughout adulthood
Testosterone- maintains reproductive organs and spermatogenesis
DHT- male pattern baldness, male hair pattern
What is hypogonadism?
Decreased testosterone release from testicles(primary) or as a result of altered release of hormone from the hypothalamus/pituitary (secondary). Can occur at any age
Increased exogenous testosterone: Abdrogen (anabolic steroids) abuse leads to decreased LH and increased aggression