The müllerian ducts __ in the male. The indifferent gonad migrates to the ___ to become the ___. The ___ is responsible for pulling the testis into the scrotum during development.
The müllerian ducts regress in the male. The indifferent gonad migrates to the urogenital ridge to become the testicle. The gubernaculum testis is responsible for pulling the testis into the scrotum during development.
In humans, interstitial tissue takes up __ of the total testicular volume.
20% to 30%
FSH and testosterone play the most important role in the regulation of Sertoli cell function. ABP is made by ___.
Sertoli cell function, sertoli cells
At least 65% to 70% of ejaculate volume is derived from the __, with the remainder from the__ (with__) and ___. __ may also contribute a small amount of fluid to the normal ejaculate.
VAS DEFERENS (with sperm)
The arterial supply to the human testis and epididymis is derived from three sources: .
INTERNAL SPERMATIC ARTERY
exogenous testosterone inhibits pituitary production of FSH and LH. Because of negative feedback inhibition that maintains homeostatic balance in the pituitarygonadal axis, exogenous testosterone of any type will cause anterior pituitary production of LH and FSH to fall. This results in azoospermia in most of men on anabolic steroids, but the effect will vary based on the dose, frequency, and duration of the steroid regimen
anterior pituitary production of LH and FSH
Sertoli-Sertoli tight junctions prevent the___ into the ___ from the testicular interstitium. These junctions between Sertoli cells also segregate ___ from meiotic and postmeiotic germ cells and are the structural basis for the ___
Sertoli-Sertoli tight junctions prevent the deep penetration of electron-opaque tracers into the seminiferous epithelium from the testicular interstitium. These junctions between Sertoli cells also segregate premeiotic germ cells (spermatogonia) from meiotic and postmeiotic germ cells and are the structural basis for the “blood-testis” barrier
testosterone produces ___ and activates negative feedback on FSH secretion. Prolactin in excess can ___ LH secretion.
testosterone produces Inhibin and activates negative feedback on FSH secretion. Prolactin in excess can downregulate LH secretion.
Anatomically, the epididymis is divided into three regions: (3)
On the basis of histologic criteria, each region can be subdivided into distinct zones separated by __
the caput or head, the corpus or body, and the cauda or tail of the epididymis.
____ and exchange of genetic material is the hallmark of chromosomal recombination during meiosis. This does not occur in mitosis. Two other unique characteristics of meiosis are that ___ during meiosis I, the first cell division, and chromosome numbers in daughter cells are half (haploid) that of mitotic cells.
Crossing over of sister chromatids
homologous chromosomes pair
A testosterone peak occurs at approximately __ of age. Another peak occurs earlier, during the __ of gestation and a third peak occurs later at __
Studies in men with congenital absence of the vas deferens or epididymal obstruction from vasectomy frequently report ___ in sperm aspirated from the ___epididymis, with ___ __ in the __
Studies in men with congenital absence of the vas deferens or epididymal obstruction from vasectomy frequently report poor motility in sperm aspirated from the distal epididymis, with optimal sperm quality and motility in the proximal epididymis.
Type A spermatogonia are the only true stem cell in the testis as they can either self renew or differentiate down the spermatogenic pathway.
TRUE STEM CELL
Sperm spend ___ developing in the testis and ___ in the epididymis. Depending on ejaculation frequency, they can also be stored in the ___ from for days to several weeks.
45 to 60 days
The ___ piece of the sperm is a highly organized segment consisting of helically arranged mitochondria surrounding a set of outer dense fibers and the characteristic ___
The middle piece
9 + 2 microtubular structure of the axoneme.
Testosterone is converted to DHT in target tissue by__ Testosterone is produced by the ___, exists mainly in bound forms in plasma, and is mainly regulated by __. Excess prolactin __.
decreases testosterone production.
Studies have shown that after sexual stimulation or ejaculation, the contents of the vas deferens are propelled back toward the __, because the ___ of the vas deferens contracts with greater amplitude, frequency, and duration than does the ___.
Studies have shown that after sexual stimulation or ejaculation, the contents of the vas deferens are propelled back toward the cauda epididymis, because the distal portion of the vas deferens contracts with greater amplitude, frequency, and duration than does the proximal portion.
Regulation of hypothalamic-pituitary-gonadal (HPG) axis hormones occurs primarily through __
The determination of maleness is derived from the __ on the Y chromosome. However, developmental genes such as ___ and __ are considered antitestis genes and can proactively induce female gonadal development.
WNT4 and DAX1
Changes to the HPG axis with paternal age include:
lower testosterone levels, blunted axis feedback, and irregular hormone pulsatility.
The testis contains ___ of seminiferous tubules and __ in the young adult.
700 M leydig tubules
__ there are increases in sperm structural chromosomal abnormalities, autosomal dominant mutations, and epigenetic alterations leading to disease in offspring.
With paternal age
The epididymis consists of __ with absorptive and secretory function, basal cells derived from macrophages, and contractile cells that __
The epididymis consists of principal cells with absorptive and secretory function, basal cells derived from macrophages, and contractile cells that facilitate sperm transport.
During __ , sperm mature by gaining progressive motility and the ability to bind to and penetrate the egg zona pellucida.
Epididymal function is temperature and androgen (mainly DHT) dependent, important considerations for __, __, and __ use.
Epididymal function is temperature and androgen (mainly DHT) dependent, important considerations for cryptorchidism, varicocele, and 5α-reductase use.
The vas deferens is of Wolffian (mesonephric) duct origin and serves to transport sperm from the ___ to the __
The vas deferens is of Wolffian (mesonephric) duct origin and serves to transport sperm from the cauda epididymis to the ejaculatory duct during seminal emission.
Sperm are ciliated cells that possess a ___ axonemal structure that allows motility.
It is estimated that ___ regulate sperm motility.
200 - 300 million
16. Sperm motility defects, termed __, are common and can be either correctable (nonspecific flagellar anomalies) or genetic (dysplasia of the fibrous sheath).
Human sperm mtDNA is a __ that encodes for respiratory-chain–complex proteins and is very susceptible to mutations.
circular, histone- and intron-free DNA ring