GHM lecture 10 male endocrine Flashcards
What is meiosis
It is a type of cell division formed by gametes in sexually reproducing organisms. Meiosis results in cells with a haploid chromosome as a opposed to diploid(2 sets of chromosomes)
Hypothalmic-pituitary gonadal axis
GnRH is released by the preoptic nuclei in the hypothalamus. This stimulates the anterior pituitary to release LH and FSH. This stimulates the testis and ovaries to secrete sex androgen, estrogen and progestins. Feedback is negative so if estrogen progestin formed then less GnRH is relaesed from the preoptic nuclei. Some stages in menstrual cycle have positive feedback leading to hormone surge.
embryonic gonad cells
These are all identical. They are somatic cell precursors. They are germ cells giving rise to gametes
Sex differentiation in females
Gonadal cells can go down two pathways. Testicular and ovarian pathway. In females supporting cells differentiate into granulosa cells which enclose oocytes to form follicles in the ovary.
Sex differentiation of embryonic gonad cells in males
Supporting cells in embryonic gonad differentiate into sertoli cells. Enclose germ cells. They form testicular chords. sterdioidogenic cells become theca cells in female and leydig cells in male
3 types of cells in embryonic gonad
Supporting cells, Germ cells, Sterdiogenic cells
What are Sterdiogenic cells
Sterdiogenic cells found in embryonic gonads which differentiate into theca cells in females and leydig in males
Gonodal development in the male embryo
in 6 Week of pregnancy there is a migration of undifferentiated germ cells.
For 2 weeks precursor gametes are formed by mitosis. The activation of SRY locus on Y chromosome determines its sex as male.
Primodial germ cells differentiate into spermatogonia. Supporting sex cells become sertoli cells.
What are the male and female internal genetalia duct systems
male is wolffian duct
female is mullerian duct
what is mullerian inhibiting hormone
mullerian inhibiting hormone is released by SRY
Supporting cells release SRY.
Wolffian duct is triggered by testosterone to form epidiymys, vas deferens and seminal vesicles.
prostate gland develops
male genetallia differentiation due to dihydrotestosterone
External genatalia require DHT to differentiate. DHT causes prostate to grow. Genital folds fuse to form penis around urethea. Labioscrotal swelling forms scrotum. DHT causes testicle descent. hCG from placenta stimulates testosterone production in foetus.
hCG from placenta stimulates testicular testosterone production in fetus. Descent of testes requires fetal gonadatropin. Any foetus exposed exposed to DHT after week 5 will develop a male phenotype (ALS)
Describe the male reproductive anatomy
organs
gonads- produce gametes and secrete hormones
ducts- transport and store gametes
accessory sex glands support the gametes
Penis function- ejaculation, erection, urination
scrotum- support the testes, temperature regulation, contains cremaster muscle which is skeletal muscle contributing to support and temp regulation of testes
Describe the testes
The testes lie within the tunica vaginalis. The testes are the site of spermatogenesis and androgen production
Describe the ducts
urethra
spermatic cord (blood + autonomic nerves + lymph vessels, vas deferens)
Epididymis(where spermatozoa complete maturation takes 2 weeks)
Vas deferens, fuses with tail of epididymis, stores mature sperm.
Rete testes- carries sperm from the seminiferous tubules(where sperm is produced) to the epididermis
spermatogenesis
conversion of diploid spermatogenia into haploid spermatozoa
spermiogenesis
conversion of haploid spermatid into haploid spermatozoa
sertorli cells
sustentacular cells (nurse cells), activated by FSH, bound by tight junction which form blood testis barrier. Cells secrete AMH, inhibin to regulate FSH, androgen binding protein, oestrodiol (to direct spermatogenesis)
