Male Repro Physiology

What is the role of the male reproductive system?

production of gametes (sperm) and secretion of testosterone

What is the male gamete?

spermatozoa (sperm)

What forms the zygote?

sperm penetrates zona pellucida of the egg via acrosomal reaction

What is the primary male sex organ?

testes

What are the secondary male sex organs?

epididymis, vas deferens, seminal vesicles, ejaculatory ducts, prostate gland, bulbourethral glands

What makes up the male external genitalia?

penis and scrotum

What makes up the male internal genitalia?

testicles, epididymis, vas deferens, ejaculatory duct, prostate gland, seminal vesicles, bulbourethral glands

What are male secondary sex characteristics?

facial, pubic, and axillary hair growth

increase in size of larynx leads to lower voice

increased muscle mass and male pattern hair distribution

What is genetic sex?

XY for males and XX for females

What is the role of the SRY gene?

triggers testes development at week 7 in males

absence results in ovaries at week 9

What is gonadal sex?

defined by presence of testes or ovaries

What is made by male germ cells?

spermatogonia

What is phenotypic sex?

defined by physical characteristics of internal and external genitalia

At what point in development are male and female genitalia formed?

week 12

What is the anatomical destination of the pair of labioscrotal folds in males and female?

scrotum in males

labia majora and mons pubis in females

What is the anatomical destination of the pair of urogenital folds in males and female?

penis in males

labia minora in females

What is the anatomical destination of the genital tubercle in males and female?

gland of penis in males

clitoris in females

What are the male and female homologous structures?

glans of penis and clitoris

penis and labia minora

scrotum and labia majora and mons pubis

How do the internal ducts develop?

testes make testosterone —> testosterone triggers Wolffian duct growth and male external genitalia —> Wolffian ducts develop into male structures

What is the fate of Wolffian (Mesonephric) Ducts in males?

triggered by testosterone to become epididymis, vas deferens, seminal vesicles, and ejaculatory ducts

What is the fate of Mullerian (Paramesonephric) Ducts in males?

degenerate due to AMH released from Sertoli cells

What leads to external genitalia development in males?

dependent on conversion of testosterone to dihydrotestosterone and functional androgen receptors

How do male gonads descend?

testes migrate from abdominal cavity through inguinal canal into scrotum

guided by gubernaculum and requires testosterone

What is the most common site of hernias in males?

inguinal canal

What are the individual structures that pass into the scrotum with descent?

testes, testicular vessels, lymphatic vessels, nerves, and spermatic ducts

When in development do the testes descend?

starts at week 6, completes by month 7

What is cryptochordism?

undescended testes

What can result from uncorrected cryptochordism?

sterility or testicular cancer

What is adrenarche?

increased adrenal androgens starting at age 6-8, leads to pubarche

What hormones are involved in adrenarche?

DHEA, DHEAS, androstenedione

What is DHEA?

dehydroepiandrosterone

What is DHEAS?

dehydroepiandrosterone sulfate

What physical changes occur in gonadarche?

growth and maturation of genitals, secondary sex characteristic formation, growth spurt, spermarche

What is spermarche?

initiation of sperm production in testes

What hormones are involved in gonadarche?

increased FSH and LH release

How does GnRH change with puberty?

GnRH secretion is pulsatile, which causes pulsatile FSH and LH

GnRH receptors are unregulated and have increased sensitivity

How does the LH/FSH ratio change with puberty?

LH levels become higher than FSH during adult reproductive period

How does REM sleep impact puberty?

large pulses of LH is released

What is the relationship between FSH and LH in childhood?

FSH > LH

What is the relationship between FSH and LH in the adult reproductive period?

LH > FSH

What is the relationship between FSH and LH after the adult reproductive period ends?

FSH > LH

What pubic hair is seen in Tanner stage 1?

no pubic hair is present, only vellus hair

What pubic hair is seen in Tanner stage 2?

pubic hair is sparse, mainly at base of penis or along labia majora

What pubic hair is seen in Tanner stage 3?

pubic hair is darker, coarser, curlier, and spreads above the pubis

What pubic hair is seen in Tanner stage 4?

adult type, but covers an area smaller than in most adults

What pubic hair is seen in Tanner stage 5?

adult pattern

What male genital development is seen in Tanner stage 1?

penis, scrotum, and testes are the same size and relative to body size

What male genital development is seen in Tanner stage 2?

scrotum and testes are enlarged

What male genital development is seen in Tanner stage 3?

penis is enlarged, predominantly in length

scrotum and testes are further enlarged

What male genital development is seen in Tanner stage 4?

penis is further enlarged in length and diameter, scrotum and testes are further enlarged

What male genital development is seen in Tanner stage 5?

adult pattern

What female breast and genital development is seen in Tanner stage 1?

only papillae are elevated

What female breast and genital development is seen in Tanner stage 2?

breast buds begin to develop, breasts and papillae are both elevated, areolar diameter increases

What female breast and genital development is seen in Tanner stage 3?

breasts and areola further enlarge

vagina enlarges and begins producing a discharge, menstrual period may begin

What female breast and genital development is seen in Tanner stage 4?

areola and papillae project outward beyond level of breast tissue

menstruation and ovulation begin, likely to be irregular

What female breast and genital development is seen in Tanner stage 5?

further breast enlargement, areola on same level as the rest of the breast, only papillae project

adult pattern

What is the role of the scrotum?

maintains testes at optimal temperature of 2C lower than body temperature

How is temperature of the testes regulated?

facilitated by cremaster and dartos muscle

countercurrent heat exchange in testicular vessels

What is the role of the seminiferous tubules?

specific site of sperm production

What is the spermatic cord?

passes through the inguinal canal and contains testicular vessels, lymphatic vessels, nerves, and the vas deferens

What is the role of the epididymis?

site of sperm maturation and storage

What is the role of the vas deferens?

transports sperm from epididymis to urethra via ejaculatory duct in sexual arousal

What is the role of the ampulla of the vas deferens?

stores sperm and secretes citrate and fructose

What forms the ejaculatory duct?

union of vas deferens and duct of seminal vesicle

What is the role of the ejaculatory duct?

carries semen to the urethra

What is the role of the testes?

produce sperm in tubules and testosterone in Leydig cells

Where are Leydig cells located?

between seminiferous tubules

What is the role of Leydig cells?

produce testosterone in response to LH in the testes

What is the role of Sertoli cells?

act to phagocytose excess cytoplasm made in spermiogenesis

maintain environment for sperm

secrete fluid to aid in sperm transport

What is the Blood Testes Barrier?

formed by tight junctions between Sertoli cells to protect developing gametes from the immune system

What hormones are secreted by the Sertoli Cells?

androgen binding protein, inhibin, AMH, and estrogen

What is the role of inhibin in men?

inhibits FSH

What is the role of androgen binding protein?

concentrates testosterone in proximity of developing gametes

What is spermatogenesis?

process of sperm production in seminiferous tubules over 64-74 days

What are spermatogonia?

stem cells that divide via mitosis to form primary spermatocytes

What are primary spermatocytes?

undergo meiosis I to form spermatocytes

What are secondary spermatocytes?

undergo meiosis II to form haploid spermatids

What is spermiogenesis?

differentiation of spermatids into mature spermatozoa

What makes up semen?

fructose, citrate, prostaglandins, calcium, alkaline mucus, and enzymes

sperm

What triggers semen secretion?

sympathetic impulses during emission phase, causing prostate and seminal vesicles to contract

What is the role of the prostate gland?

secrete alkaline milky fluid to neutralize vaginal acidity

What is in the fluid secreted by the prostate?

fibrinolysin and prostate specific antigen

What is the role of fibrinolysin?

liquefy semen and increase motility

What is the role of prostate specific antigen?

used as cancer marker

What is the role of the seminal vesicles?

produce majority of seminal fluid

What is in seminal fluid from the seminal vesicle?

citrate and fructose, prostaglandins, and fibrinogen

What is the role of citrate and fructose in seminal fluid?

sperm nourishment

What is the role of prostaglandins in seminal fluid?

sperm motility and increases penetrability of cervical mucus

What is the role of fibrinogen in seminal fluid?

sperm clumping in vagina

What is the role of Bulbourethral (Cowper’s) Glands?

secrete alkaline mucus for lubrication and pH neutralization before ejaculation

What mediates erection?

pudendal nerve of parasympathetic nervous system

What mediates emission?

sympathetic nervous system via T12-L2

What triggers ejaculation?

sympathetic nervous system spinal reflex triggered by semen in urethra

What occurs in the erection phase?

increased mucus secretion from urethral and bulbourethral glands

nitric oxide or VIP is released —> cGMP forms

penile arteries relax and corpora cavernosa and corpus spongiosum engorge

What occurs in the emission phase?

contraction of vas deferens and accessory glands to move semen into urethra with seminal fluid

What occurs in the ejaculation phase?

rhythmic contractions of ischiocavernosus and bulbocavernous muscles expel the semen

What is capacitation in fertilization?

removal of inhibitory factors from seminal fluid

withdrawal of cholesterol from the sperm

redistribution of sperm surface proteins

What causes capacitation in fertilization?

acrosomal reaction between sperm and ova

What releases GnRH?

arcuate nuclei of hypothalamus

What is the role of GnRH in the HPG axis?

stimulates anterior pituitary to release LH and FSH