Lecture 28 3/22/24 Flashcards
What are the endocrine requirements that must be met for sperm production?
-adequate secretion of GnRH from hypothalamus
-FSH and LH secretion from anterior pituitary
-secretion of testosterone and estrogen
Which cells produce testosterone?
Leydig cells
What is the role of Sertoli cells?
convert testosterone to estradiol
How do testosterone and estradiol act on the hypothalmus?
negative feedback on the hypothalamus leads to reduced GnRH production, which reduces LH and FSH production
Which type of center is present in the hypothalamus in males, and which is not?
-tonic center IS present
-surge center IS NOT present
Why is it important that LH is released in pulses in the male?
-high conc. of testosterone is needed in the seminiferous tubules for spermatogenesis
-Leydig cells can become refractory/reduce secretion of testosterone when exposed to sustained high levels of LH
What is puberty in the male?
ability of the male to produce and ejaculate at least 50 mil. sperm with at least 10% motility
What are the endocrine hallmarks of male puberty?
-sharp increase in testosterone
-secretion of GnRH, FSH, and LH
What pathway do sperm follow from the testis out of the body?
-rete tubules
-efferent ducts
-epididymis
-ductus deferens
-urethra
What happens to sperm in the head and body of the epididymis?
changes that allow the sperm to become fertile
What is the function of the tail of the epididymis?
storage organ for sperm prior to ejaculation
What is seminal plasma?
mixture of spermatozoa with fluids from the accessory sex glands
How does a normal testis appear on ultrasound?
hypoechoic homogenous oval structure
What are the phases of spermatogenesis?
-proliferation
-meiotic phase
-differentiation
What is the proliferation phase?
phase in which the spermatogonia undergo mitotic divisions
What is the meiotic phase?
phase in which the spermatogonia undergo meiotic division to form spermatocytes/spermatids
What is the differentiation phase/spermiogenesis?
-no divisions occur
-spermatid undergoes transformation to become a fully differentiated and specialized sperm cell
What phases occur within the differentiation phase?
-Golgi phase
-cap phase
-acrosomal phase
-maturation phase
What happens during the Golgi phase?
highly-developed Golgi apparatus gives rise to the acrosome
What happens during the cap phase?
-acrosome forms a distinct cap over anterior portion of nucleus
-primitive flagellum forms
What happens during the acrosomal phase?
-acrosome continues to spread and cover more of anterior nucleus
-nucleus begins to elongate and shift to one aspect of cell
-spermatids become deeply embedded in Sertoli cells
What happens during the maturation phase?
-final assembly to form spermatozoon
-mitochondria cluster around flagellum in a spiral fashion
What is spermiation?
process by which mature spermatids are released from the Sertoli cells into the lumen of the seminiferous tubules
Which features are seen in mature sperm?
-head with acrosome and nucleus
-neck that joins head to mid-piece filled with mitochondria
-tail containing flagellum
What are the components of the testis parenchyma?
-seminiferous tubules
-interstitial space containing vessels, connective tissue, lymphatics, nerves, and Leydig cells
What are the two major regions of the seminiferous tubules?
-basal compartment
-adluminal compartment
What occurs in the basal compartment of the seminiferous tubules?
spermatogonium divide to form other spermatogonia and primary spermatocytes
What occurs in the deep adluminal compartment of the seminiferous tubules?
primary spermatocytes divide into secondary spermatocytes and spherical spermatids
What type of sperm are in the peripheral adluminal compartment of the seminiferous tubules?
sperm cells that are near complete maturation but still in contact with Sertoli cells
Why is it important that there is a counter current between the testicular artery and vein?
allows for some testosterone to be recycled in order to maintain high local concentrations in the testes
Which hormones are produced by Sertoli cells?
-estradiol (converted testosterone)
-inhibin
What determines the number of sperm cells that a testis can produce?
-number of Sertoli cells
-size of the testis
What is the blood-testis barrier?
tight junction of Sertoli cells with the basement membrane that prevents immune attack of the sperm cells
How do sperm motility and fertility change throughout the epididymis?
-sperm are non-motile when in the head
-sperm have some motility and fertility in the body
-sperm are motile and fertile once they reach the tail
What are the characteristics of the ampulla?
-enlargement of ductus deferens
-serves as sperm reservoir
What is the main characteristic of the seminal vesicle/vesicular gland?
produces the majority of the ejaculate
What is produced by the bulbourethral gland?
gel fraction of the ejaculate
What is produced by the prostate gland?
sugars and proteolytic enzymes
What are the functions of the seminal plasma?
-vehicle, protection, and energy for sperm
-capacitation
-effects on female repro tract
What are the characteristics of the spermatic cord?
-suspends testis in scrotum
-provides pathway to and from the body for testicular vasculature/lymphatics/nerves
-houses ductus deferens, cremaster muscle, and pampiniform plexus
What is the function of the pampiniform plexus?
transfer heat from the arterial blood into he venous blood so that the blood reaching the testes is optimal temp.
What is the tunica dartos?
smooth muscle in the scrotum that responds to temp. changes to move the testes closer to or away from the body
Why is it important that the scrotum is heavily populated with sweat glands?
allows for thermoregulation and cooling of the testes via evaporative heat transfer
What is evaluated in a sperm analysis?
-sperm producing ability of the testis
-number of morphological normal sperm
-number of motile sperm
-viability of sperm
Why is an artificial vagina used to collect sperm?
provides appropriate temp. and pressure stimuli
What are the main parameters evaluated in semen collection?
-total vol. in mLs
-conc. of sperm/mL
-total number of sperm
How is sperm motility assessed?
% of sperm that move in forward direction; count out of 50 sperm and estimate
What percent of sperm must be morphologically abnormal to cause reduced fertility?
20% or greater
How is the number of insemination doses per ejaculate determined?
number of morphologically normal and progressively motile sperm/number of sperm wanted per dose
