Male Repro Flashcards
What does the Male reproductive system consist of
Consists of :
A pair of testes
A pair of excretory genital ducts (rete testis, efferent ductules, epididymis, ductus deferens, and ejaculatory duct)
A penis
Accessory sex glands (prostate, seminal vesicles, bulbourethral, and ampulla)
The Function of Testes
Produce sperm and testosterone
Development of Testes
Develop in the abdominal cavity,
but migrate before birth (ruminants and pigs) or soon after birth (dog and horse) in the scrotum, where their position differs depending upon the species
The different positions of the testes based on species
Vertical in the bull,
Oblique in the dog,
Longitudinal in the horse.
Why is scrotal migration essential
The scrotal migration is essential because sperm production requires temperature slightly lower than the body temperature (34C versus 39C).
How is the lower temperature of the scrotum mentained
The lower temperature is maintained by :
1. countercurrent heat exchange between arterial and venous blood
2. rich sweat glands in the scrotum,
3. contraction or relaxation of the tunica dartos.
Clin sig for Testes
Animals with bilateral cryptorchid testes are infertile, although they may have libido; unilateral or bilateral cryptorchid animals should not be used for breeding since this trait can be genetically transferred to offspring.
What are the two layers covering the testes
tunica vaginalis (corresponding to the visceral layer of the peritoneum)
and tunica albuginea containing dense fibroelastic connective tissue and a few smooth muscles cells.
The Tunica Albuginea of the testis
The tunica albuginea extends into the testis and divides into lobules;
Each lobule is made of two to four highly convoluted seminiferous tubules,
interstitial tissue containing blood vessels and interstitial cells also called Leydig cells.
What are the components of Seminiferous Tubules (ST)
Each ST is 30-70 cm long, and has a long-convoluted part and a short straight part at both ends; both straight parts of a ST open into the rete testis.
The Convoluted part of the Seminiferous tubule is surrounded by
Is surrounded by smooth muscle cells (myoid cells)
and a basement membrane.
What two types of cells are in the stratified epithelium of the basement membrane of the seminiferous tubules
Germ cells:
(spermatogonia, primary spermatocytes, secondary spermatocytes, spermatids, and spermatozoa) and
somatic cells: (Sertoli cells).
What is Spermatogenesis
Spermatogenesis is the process by which sperm are produced and includes three consecutive stages: proliferation, maturation, and metamorphosis
It is worth noting that spermatogenesis is a continuous process in all species that begins with puberty and continues until death.
Proliferation stage of Spermatogenesis
Cells of this stage are spermatogonia, which are stem cells and mitotically divide at a regular interval
hence, the loss of spermatogonia, for example, by radiation, can cause permanent loss of sperm production; likewise, the transplantation of spermatogonia can restore sperm production
Maturation Stage of Spermatogenesis,***break this up
Cells of this stage are primary and secondary spermatocytes. Primary spermatocytes are diploid cells with 4CDNA content, undergo the first meiotic division (reductional division) to form secondary spermatocytes. The latter are haploid cells with 2CDNA, undergo quickly second meiotic division, without DNA duplication, and differentiate into spermatids (1CDNA).
Metamorphosis stage of Spermatogenesis
Also called spermiogenesis
Cells of this stage are spermatids, which are located near the lumen of the ST, do not divide, but instead, undergo morphological changes that include formation of the acrosome from the Golgi body, development of the tail (flagellum) from the centriole, condensation of the nuclear chromatin, modeling of the round nucleus into an elongated nucleus, removal of most of the cytoplasm as residual body, and realignment of mitochondria in the middle piece of the tail.
The length of the the Spermatogenesis cycle
The length of the spermatogenesis cycle, as well as that of each stage, is fixed for each species, but varies between species
Spermatogenesis cycle for Cattle
the cycle is 52 days long:
Proliferation stage is completed in 13 days
Maturation stage is 19 days,
Metamorphosis stage is 20 days
Also, remember that sperm after leaving the testis take another 10-12 days to pass through the epididymis. This means that any physical, chemical, or biological injury to spermatogonia will take at least 60-65 days before it becomes visible in the ejaculate. Therefore, a bull with a questionable fertility in the first examination should be retested after an interval of at least 60 days.
What are Sertoli Cells
Large pyramidal cells that extend from the basal lamina to the lumen;
characterized by oval, pale (euchromatic) nucleus with prominent nucleolus and deep invagination of the nuclear membrane;
and cytoplasm contains organelles associated with protein synthesis and digestion of phagocytosed materials.
What is the blood-testis barrier
The lateral borders of two adjacent cells near the basal area of the epithelium form tight junctions often called blood-testis barrier, which divides the seminiferous epithelium into two compartments
What are the two compartments of the seminiferous epithelium
Basal and adluminal.
The basal compartment of the seminiferous epithelium contains:
The basal compartment contains spermatogonia and basal part of Sertoli cells.
The adluminal compartment of the seminiferous epithelium contains:
The adluminal compartment contains all other germ cells and apical part of the Sertoli cells.
How does the basal compartment of the seminiferous epithelium get their nutrients
Because of the blood testis barrier, Cells in the basal compartment can get their nutrients by diffusion from the blood vessels lying in contact with the basal lamina
How does the adluminal compartment of the seminiferous epithelium get their nutrients
Cells in the adluminal compartment cannot do so and thus are dependent upon Sertoli cells for their nutrition.
What does the blood-testis barrier do for the cells in the adluminal compartment
Also, cells in the adluminal compartment are considered foreign because they are absent at birth and thus the blood-testis barrier ensures their differentiation free from an autoimmune response.
Function of Sertoli cells:
Functions of the Sertoli cells include: 1) support, protection, and nutrition of germ cells;
2) exocrine secretion of androgen binding protein and testicular fluid;
3) endocrine secretion of estrogen, anti-Mullerian hormone (AMH, causes regression of Mullerian ducts in the embryo) and inhibin (inhibin negatively regulates FSH secretion; more inhibin, less FSH, and vice versa);
4) regulate number of sperm produced (more Sertoli cells, more sperm; note, Sertoli cells do not divide after puberty);
5) release of sperm (process occurs by a flushing effect of testicular fluid and is called spermiation); and 6) phagocytosis of residual bodies (left over spermatids’ cytoplasm).
Regulation of Sertoli cells
Hypothalamus-pituitary-Sertoli axis: GnRH to FSH to inhibin. Sertoli cell tumor is a testicular cancer and results in increased inhibin level and decreased FSH level in the blood (negative feed-back). Besides FSH receptors, Sertoli cell has receptors for testosterone, which regulates its overall activity.
Where are Leydig Cells
interspersed between Seminiferous tubules
How many Leydig cells are there
Numbers vary among species, few in ruminants and man, abundant in carnivores, numerous in horses, more so in pigs.
Components of Leydig cells
Leydig cells occur singly or in groups, cytoplasm is eosinophilic and vacuolated, (what is the reason for eosinophilia and vacuolation?), and nucleus is round and slightly heterochromatic.
Function of Leydig Cells
Leydig cells secrete a steroid hormone, testosterone, under the influence of LH.
What does testosterone secretion depend on
Leydig Cells,
The amount of testosterone secretion is related to the number of Leydig cells
The effect of testosterone
The higher the testosterone level, the larger the size of accessory glands, and the greater the volume of semen,
which is about 1 ml in sheep and goats,
3-5 ml in bulls,
8-15 ml in dogs,
50-150 ml in horses,
200-300 ml in pigs.
Regulation of Leydig Cells
GnRH to LH to testosterone. Leydig cell tumor is another testicular cancers and results in higher testosterone level and lower LH level in the blood (negative feed-back).
How many Leydig cells are there
Numbers vary among species, few in ruminants and man, abundant in carnivores, numerous in horses, more so in pigs.
Function of testosterone
1.Testosterone is a metabolic hormone used by all body cells for metabolism.
Why is testosterone essential
It is essential for development of male sex ducts
In the absence of testosterone, male ducts do not develop and, therefore, the embryo is phenotypically, not genetically, a female-like (female pseudo-hermaphrodite)
Why is testosterone essential for spermatogenesis
It is essential for spermatogenesis, sperm maturation, and libido
–>one of the main reasons for the loss of libido with age
For spermatogenesis to occur, testosterone level surrounding germ cells should be 50 to 100 times higher than the plasma testosterone level (for example, 2-3 ng/ml vs 100-300 ng). Otherwise, sperm production stops.
Using the above background information, explain why do athletes using steroids at an early age can become permanently infertile and their testes reduced to the size of a walnut? Why can a testosterone implant or repeated testosterone injections render animals infertile without adversely affecting libido? Why are animals with bilateral cryptorchidism infertile but have libido?
The Function of excretory genital ducts (rete testis, efferent ductules, epididymis, ductus deferens, and ejaculatory duct)
Where testicular fluid is absorbed, sperm mature (acquire the ability to move in a forward direction and fertilize ova)
and then are stored until ejaculated (storage occurs in the tail of the epididymis)
What is the Rete testis
An excretory genital duct.
Anastomosing channels embedded in the mediastinum, lined with simple cuboidal to columnar epithelium, drain into efferent ductules at the dorsal extremity of the testis.
What are the Efferent Ductules
numbers vary from 15-20 in domestic species;
Drain sperm individually into one long tube called epididymis (this means that a blockage of few efferent ductules will not cause an immediate stoppage of sperm flow; while a blockage of the epididymis at any point along its length will).
What lines the Efferent Ductules
Lined by pseudostratified columnar epithelium with both non-ciliated and ciliated cells
while cilia help in the movement of sperm toward the epididymis, microvilli of non-ciliated cells absorb almost 90% of testicular fluid, with the remaining 10% absorbed in the epididymi
The different length of the Epididymis in animals
Almost 80 meters in the horse,
40-50 m in the bull and ram,
and 5-8 m in the dog;
What is the Epididymis
a long, highly convoluted duct, which is grossly divided into head (caput), body (corpus), and cauda (tail) regions.
Functions: testicular fluid absorption, sperm maturation, sperm transport, and sperm storage.
What is the epithelium of the three regions in the epididymis ( head, podu, tail)
All three regions have pseudostratified columnar epithelium with stereocilia;
What does the epithelium of the epididymis do
Columnar epithelial cells have both absorptive (testicular fluid) and protein synthesizing functions.
The proteins produced are believed to be associated with the maturation of sperm (motility and fertility) as they pass along the length of the epididymis.
Ductus (vas) Deferens
Straight, thick-walled duct, lined by pseudostratified columnar cells with stereocilia.
Epithelium is surrounded by many layers of smooth muscle arranged in different directions, tunica adventitia or serosa surrounds the muscular layer.
Function is to propel sperm from the tail of the epididymis to the urethra at the time of ejaculation.
Ejaculatory Duct
Terminal part of the ductus deferens with a relatively thinner wall, it empties into the urethra at the colliculus seminalis, also the site for seminal vesicle secretion.
Accessory sex glands (prostate, seminal vesicles, bulbourethral, and ampulla) function
whose secretions form a part of the semen.
What is the Ampulla
Pre-terminal dilation of the ductus deferens;
Ampulla also serves as an additional storage depot for sperm;
And that is the reason that abstinence is recommended for 6-8 weeks after vasectomy.
What is the epithelium of the ampulla and how is it arranged
Pseudostratified epithelium is folded and is modified to form compound tubular glands
What is the importance of the compound tubular glands of the ampula
Its secretion at the time of ejaculation forms a part of the seminal plasma
Seminal Vesicles
Paired gland, present in all species except carnivores
What is the epithelium of the seminal vesicles
Branched tubulo-alveolar gland lined by simple or pseudostratified epithelium that is surrounded by smooth muscle cells
What do seminal vesicles secrete
The secretion is yellow viscous that contains fructose, which is the energy source for sperm motility.
What is the Prostate
Present in all species (most developed in the dog, followed by man, the horse and then the pig) and is intimately associated with the urethra;
Branched tubulo-alveolar gland lined by simple cuboidal to columnar epithelium
What is the epithelium of the prostate
Branched tubulo-alveolar gland lined by simple cuboidal to columnar epithelium
What does the prostate secrete
Secretion is thin, whitish fluid containing proteolytic enzymes, citric acid, lipids, and phosphatase.
What is the Bulbourethral
Paired (small in the horse and bull, very large in the pig, present in the cat but absent in the dog), localized at the end of the pelvic urethra, covered with skeletal muscles, whose contractions at the time of ejaculation help in releasing bulbourethral secretions.
Androgen Control
The development and secretory activity of accessory glands is dependent upon the supply of testosterone
DHT, 5-alpha reductase reduces testosterone,
And controls derivatives of urogenital sinus, including prostate and external genitalia
What is used to treat prostate hypertrophy
5-alpha reductase inhibitor (Finasteride or Proscar)
Because castration causes atrophy
Function of the Penis
The copulatory organ, common outlet for urine and semen
What are the 3 main parts of the Penis
Consists of root, body, and glans.
The body of the penis consists of
The body consists of a thick capsule covering two erectile bodies: corpora cavernosa penis and corpus spongiosus.
What does the corpora cavernosa penis cover
The corpora cavernosa covers the dorsal-lateral part of the urethra
What does the corpora cavernosa penis contain
Contains numerous venous sinuses lined by endothelium and surrounded by smooth muscle cells and elastic fibers.
How are the venous sinuses of the corpora cavernosa penis fed
Venous sinuses are fed directly by helical arteries (coiled arteries that have additional smooth muscle cells in the tunica intima).
What does the corpus spongiosum surround
The corpus spongiosus surrounds the urethra and is structurally like the corpus cavernosa, except venous sinuses are less developed.
What is the glans penis
The glans penis is an extension of the corpus spongiosus, contains bone (os penis) in carnivores and rodents.
The difference in penises based on species: Vascular Penis
Horse and man
Venous sinuses are much more developed
The difference in penises based on species: Fibroelastic
Ruminant, venous sinuses are mainly developed in the proximal segment
The difference in penises based on species: Intermediate
Carnivore, os penis gives additional rigidity.
What are the two simulations for erections
Parasympathetic
Sympathetic
What does the parasympathetic stimulation do during erection
Parasympathetic stimulation relaxes smooth muscles in the helical artery as well as those surrounding venous sinuses, which results in increased blood to the penis and thus its enlargement;
Contraction of the ischiocavernosus muscle during erection results in occlusion of venous outflow, which brings rigidity to the penis.
What does the Sympathetic stimulation
Results in contraction of the ductus deferens that propels sperm from the tail of the epididymis to the urethra, and it also causes contraction of the accessory sex glands, whose secretion is also released into the urethra. The release of sperm and accessory secretions in the urethra is called emission.
This is followed by forceful contractions of bulbospongiosus, levator ani and ischiocavernosus muscles, which then propel the ejaculate (sperm plus accessory secretions) out of the urethra, the process called ejaculation.
What is Sperm
Spermatozoon (singular) or spermatozoa (plural)
Functions: Nucleus: source of paternal genetic material; acrosome: source of enzymes that aid sperm penetration in the ovum; tail: responsible for motility; mitochondrial sheath: source of ATP
What is the shape of sperm for Domestic animals
Disc-like in domestic animals
What is the shape of sperm for rodents
Sac-like in rodents
What is the shape of sperm for birds
Whip-like in birds
What are the three parts of the Sperm
Head, Neck, and Tail
Head of Sperm
Consists of the nucleus containing condensed haploid chromatin; the acrosome cap covers one-half of the nucleus and contains lysosomal enzymes (hyaluronidase, acrosin) that are necessary for penetration of the ovum.
Neck of Sperm
Neck contains the centriole and connects the head with the tail.
Tail of Sperm
Tail is divided into three segments: mid piece, principal piece, and end piece.
The tail consists of an axoneme (throughout the length, 2 central tubules and 9 peripheral doublets),
9 coarse fibers (in mid piece and principal piece), and a mitochondrial sheath (in mid piece),
and a fibrous sheath (principal piece).
Factors responsible for sperm transport along the length of the excurrent ducts
Remember, testicular sperm are neither motile nor fertile, but they acquire both properties while passing through the excurrent ducts.
Sperm become motile and fertile by the time they reach the tail of the epididymis. Although sperm have the potential to move in a forward direction in the tail of the epididymis, they remain immotile within the tail (crowding effect).
How long does it take for the sperm to go from the testis to the epididymis
This passage that takes about 10-12 days from the testis to the tail of the epididymis, where sperm are stored until ejaculated.
Transport of Sperm
From the testis to the rete testis to the ductuli efferentes: testicular fluid.
From the ductuli efferentes to the head of the epididymis: ciliary movement and smooth muscle contraction;
From the head of the epididymis to the tail of the epididymis: smooth muscle contraction.
Sperm Morphologically during transport in the excurrent duct
Migration of protoplasmic droplet from the neck region
Sperm with proximal Droplet in the neck region
Sperm with distal Droplet in the distal midpiece
Sperm without Droplet
Where is the sperm when it has proximal droplet
In the testis
Efferent ductules
Head of the epididymis
Where is the sperm when it has distal droplet
Body of the epididymis
Where is the sperm when it has no droplet
Tail of the epididymis
Ductus
Ductus deferens
Urethra
Ejaculate
Sperm Functionally during transport in the excurrent duct
Testicular sperm are both infertile and immotile when they leave the testis, but they acquire the ability to move in a forward direction and to fertilize ova by the time they reach the tail of the epididymis (note, testicular sperm cannot fertilize ova in a dish;
However, sperm from the epididymis tail can).
Sperm Biochemically during transport in the excurrent duct
Acquisition of mucopolysaccharides and glycoproteins by the acrosome
(the process of acquiring these molecules is called decapacitation because these molecules are removed in the female genital tract, the process of removal is called capacitation, which is essential for sperm binding with the ovum; in other words, un-capacitated sperm do not bind with the ovum).
Where is 5 alpha reductase present
5 alpha reductase enzyme is present in the epididymis, accessory sex glands, and external genitalia.
Function of 5 alpha reductase
5 alpha reductase converts testosterone into dihydrotestosterone (DHT)
5 alpha reductase inhibitor clin sig
5 alpha reductase inhibitors reduce DHT level and are clinically used to treat prostate hypertrophy in humans.
Dihydrotestosterone (DHT)
DHT is five to ten times more potent than testosterone and is required for the development of accessory sex glands and the external genitalia (penis, scrotum).
Where is Aromatase
Aromatase enzyme is present in Sertoli cells in males, granulosa cells in females, and fat cells in both males and females.
Function of Aromatase
Aromatase converts testosterone to estrogen.
What can Aromatase inhibitors do
Aromatase inhibitors can be used to increase height because estrogen accelerates growth plate fusion.
clinsig for aromatase
Aromatase inhibitors used to treat breast cancer in postmenopausal women.
Loss of Spermatogonia causes
