Embryos - Male Reproductive System Flashcards
Lateral view of male reproductive system
What does the dartos muscle constitute
The subcutaneous muscle layer of the scrotum - continues internally to make up the scrotal septum (the wall dividing the scrotum into 2 compartments for the testes)
Where do the 2 cremaster muscles descend from
What do the dartos and cremaster muscles do together
descend from internal oblique muscle
2 cremaster muscles cover each testis like a muscular net
By contracting simultaneously, the dartos and cremaster muscles can elevate the testes in cold weather (or water), moving the testes closer to the body and decreasing the surface area of the scrotum to retain heat
What are the raphae
Raised medial thickening on the surface
Describe the outer tunica vaginalis of the scrotum
A serous membrane that has both a parietal and a thin visceral layer
What lies deep to the tunica vaginalis
Tunica albuginea - a tough, white dense CT layer covering the testis itself
Name the 2nd function of the tunica albuginea (other than covering the outside of the testis)
It also invaginates to form septa that divide the testis into 300-400 structures called lobules, and sperm develop in SEMINIFEROUS TUBULES within the lobules
When does the testes descend into the scrotal cavity
During the 7th month of the development period of a male foetus
What is cryptorchidism
When 1 or both of the testes fail to descend into the scrotum prior to birth
Sagittal view of the testis
Where does sperm travel to, after it has been produced at the seminiferous tubules
Transferred to epididymis to mature
Leave the epididymis during an ejaculation via the ductus deferens
What are seminiferous tubules composed of
Developing sperm cells surrounding a lumen, the hollow centre of the tubule, where formed sperm are released into the duct system of the testis
Where does sperm go once it leaves the lumen of the STs
From the lumen of the STs, sperm move into the straight tubules (tubuli recti) and from there into a fine meshwork of tubules - rete testes
Sperm leaves the rete testes and the testis itself through the 15-20 efferent ductules that cross the tunica albuginea
What do sustentacular cells do
Support the testis
Name the group of developing germ cells
Germ cells
How does the development of germ cells progress within the tubule
From the basement membrane (at the perimeter of the tubule) towards the lumen
Name the group of developing cells in the STs
Germ cells
What do sertoli cells do
Where are they found
These elongate, branching cells are sustentacular cells that secrete signaling molecules that promote sperm production and can control whether germ cells live or die
They are found in epithelial tissue, and extend physically around the germ cells from the peripheral basement membrane of the seminiferous tubules to the lumen
How is the blood-testis barrier created
What is its function
- Tight junctions between these sustentacular cells create the blood–testis barrier
- this keeps bloodborne substances from reaching the germ cells and, at the same time, keeps surface antigens on developing germ cells from escaping into the bloodstream and prompting an autoimmune response
What are the least mature cells called
Spermatogonia
Where are spermatogonia found
Can they differentiate
They line the basement membrane inside the tubule
Spermatogonia are the stem cells of the testis, which means that they are still able to differentiate into a variety of different cell types throughout adulthood
What is spermatogenesis
The process that begins with spermatogonia, which then divide to produce primary and secondary spermatocytes, then spermatids and concludes with sperm produced
(Occurs in STs)
How long does it take for a cycle of spermatogenesis to take place
64 days
How often does a new cycle of spermatogenesis start
Every 16 days but it can vary - not synchronous across the STs
Cross section of a ST
Overview of spermatogenesis
Describe the appearance of the haploid spermatid
Look similar to earlier stages of spermatogenesis - round shape, central nucleus and a large amount of cytoplasm
Define spermiogenesis
Transforms these early spermatids, reducing the cytoplasm, and beginning the formation of the parts of a true sperm, and a spermatozoa is produced
Structure of formed sperm
Smaller than most cells in the body
Verry little cytoplasm in the head
How is the axial filament (central strand of flagellum) formed
From one centriole inside the maturing sperm cell during the final stages of spermatogenesis
What is the role of the epididymis
How long does it take for sperm to move through it
Maturation of sperm occurs here
12 days
How is sperm moved through the epididymis
Sperm enters the head of the epididymis and are moved along by the contraction of SM lining the epididymal tubes
Where are mature sperm stored in the epididymis
Stored in the tail until ejaculation occurs and then pushed by SM contraction to the ductus deferens
Where can the vas deferens be found
In the spermatic cord
Where does the vas deferens extend to superiorly
Into the abdominal cavity through the inguinal canal, continues posteriorly to the pelvic cavity, ending posterior to the bladder where it dilates in a region called the ampulla
How much of semen is made up of sperm
5%
What accessory glands produce semen
Seminal vesicles
Prostate
Bulbourethral glands
How much of the semen volume do seminal vesicles contribute
60%
What does seminal vesicle fluid contain
Large amounts of fructose, which is used by the sperm mitochondria to generate ATP to allow movement through the female reproductive tract
What structure of the ductus deferens is the seminal vesicle associated with
The ampulla
Now containing seminal vesicle secretions, where does the fluid move to next
The associated ejaculatory duct - a structure formed from the ampulla of the ductus deferens and the duct of the seminal vesicle
Where is the prostate gland located
Anterior to rectum at the base of the bladder surrounded by its prostatic urethra (the portion of the urethra that runs within the prostate)
What sort of tissues is the prostate made from
Muscular and glandular tissues
What does the prostate release
Excrete an alkaline, milky fluid to the passing seminal fluid (now called semen) that is critical to first coagulate and then decoagulate the semen following ejaculation
How does the temporary thickening of semen help in fertilisation
Helps retain it within the female reproductive tract, providing time for sperm to utilise the fructose provided by seminal vesicle secretion
When the semen regains its fluid state, sperm can then pass farther into the female reproductive tract
Change in size of the prostate over a lifetime
Normally doubles in size during puberty
At 25 it begins to enlarge again
What is BPH - Benign Prostatic Hyperplasia
abnormal growth of the prostate
Causes constriction of the urethra as it passes through the middle of the prostate gland, leading to a number of lower UT symptoms
(40% of men have some degree @ 60)
What do the bulbourethral glands release
What is its purpose
When is it released
A thick, salty fluid that lubricates the end of the urethra and vagina and helps to clean urine residues from the penile urethra
Fluid is released after the male becomes sexually aroused, and shortly before the release of semen => pre-ejaculate
Cross Sectional view of the penis
What is the end of the penis called
Glans penis and has a high conc of nerve endings, resulting in very sensitive skin that influences the likelihood of ejaculation
What does the foreskin/prepuce contain
A dense conc of nerve endings, and both lubricate and protect the sensitive skin of the glans penis
How does erection occur
How does erection occur
- Nitric oxide (NO) is released from nerve endings near blood vessels within the corpora cavernosa and spongiosum
- Release of NO activates a signaling pathway that results in relaxation of the smooth muscles that surround the penile arteries, causing them to dilate
- This dilation increases the amount of blood that can enter the penis and induces the endothelial cells in the penile arterial walls to also secrete NO and perpetuate the vasodilation
- The rapid increase in blood volume fills the erectile chambers, and the increased pressure of the filled chambers compresses the thin- walled penile venules, preventing venous drainage of the penis
What enzyme degrades a key component of the NO signalling pathway in the penis
PDE5
What cells produce testosterone (steroid androgen hormone)
Leydig cells
Where are leydig cells located
Between the STs in the testes (hence sometimes called interstitial cells)
When is testosterone secreted in development
By the 7th week of development, with peak concentrations reached in the 2nd trimester
- results in anatomical differentiation of the male sexual organs
How much testosterone do leydig cells produce per day
6-7mg
What does testicular steroidogenesis result in
Testosterone concentrations that are 100 times higher in the testes than in the circulation
Maintaining these normal concentrations of testosterone promotes spermatogenesis
Other than the testes, where else is testosterone secreted
By the adrenal glands in both sexes
By the ovaries, although most is converted to estradiol
Regulation of testosterone production
Name the 3 parts of the male urethra
Prostatic - most dilatable, opening of ejaculatory duct
Membranous - urogenital diaphragm, sphincter urethrae, bulbourethral glands (fixed and narrow)
Penile/Spongy - longest, lacunae openings of urethral glands, commonly infected in venereal disease
How much does each gland contribute to content of semen
Testes - 2%
Prostate - 30%
Seminal vesicles - 65%
Bulbourethral/urethral gland - 1%
What do the secretions of the seminal vesicles contribute
Fructose
Prostaglandins
Fibrinogen
What do the secretions of the prostate contain
Proteolytic enzymes
Prostatic acid phosphatase
Prostate-specific antigen
Contents of secretions of bulbourethral glands
Secrete alkaline mucus with lubricating properties
What is hypospadia
The urethra fails to completely close
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