lecture 35 - male reproductive system 2 Flashcards
What is the purpose of having the testes in the scrotum on the outside of the abdomen?
Maintains a lower temperature than the body - 34 degrees celsius - which is optimum for spermatozoa development
What is the optimum temperature for spermatozoa development?
~34 degrees celsius
What is the name of the muscle that lines the scrotum?
Dartos muscle
How does the dartos muscle minimise heat loss from the scrotum?
Wrinkles the skin of the scrotum to reduce surface area for heat loss
Where is the cremaster muscle located?
Covers the testes and spermatic cords of the scrotum.
What is the function of the cremaster muscle?
Contracts to draw the testes up towards the body to conserve heat in the testes
Where do the spermatic cords run between?
The abdomen and testes
What do the spermatic cords contain?
Ductus deferens, blood vessels (testicular arteries and veins), nerves, lymphatics
What is the function of the venous/pampiniform plexus of the spermatic cords?
Forms a network around the arteries supplying the testes and allows the transfer of heat from the arteries to the cooler retuning blood to cool it to testicular temperature, and to warm the returning blood
What are the 2 functions of the penis?
Urination, copulation
What is the shape of the penis?
‘Cylindrical’
What is the name for the base of the penis that adheres it to the body wall?
The root/bulb
What is the name for the main length of the penis?
The body
What is the name for the head of the penis?
The glans penis
What is the glans penis covered by?
Prepuce/foreskin
What are the 3 cylindrical erectile tissues of the penis?
2 corpora cavernosa, 1 corpus spongiosum.
What is the main erectile tissue of the penis?
The 2 corpora cavernosa
Where are the corpora cavernosa located?
On the dorsal aspect of the penis (when erect)
Where is the corpus spongiosum located?
On the ventral aspect of the penis (when erect)
What do the corpora cavernosa branch into?
They run adjacent until forking out in the crura (singular crus) or roots of the penis
What penis erectile tissue is the urethra contained within?
The corpus spongiosum
What are the bulb and glans of the penis formed from?
The corpus spongiosum erectile tissue
What is the key reason that the corpus spongiosum does not become as erect as the corpus cavernosum?
Corpus spongiosum contains that urethra, so excess erection would flatten the urethra inhibiting the passage of sperm
In what medium are spermatozoa carried to the female reproductive tract in?
In seminal fluid
What is the name for the combination of spermatozoa and seminal fluid?
Semen
What are the purposes of seminal fluid?
Provides fluid medium for efficient transport of spermatozoa, activates spermatozoa propulsion abilities and provides nutrients and energy, protects against an acidic environment in penis and particularly in the female vagina.
What protects spermatozoa from the acidic environment of the female vagina during intercourse?
Seminal fluid
Where is seminal fluid produced?
In 3 accessory glands - seminal vesicles, prostate gland, bulbourethral glands
What are the seminal vesicles?
Glands in males that secrete alkaline seminal fluid
How many seminal vesicles do males have?
2
Where are the seminal glands located?
posterior to the bladder, lateral to the ampulla
What is the physical nature of the secretion from the seminal vesicles?
Viscous
What proportion of semen is secreted by the seminal vesicles?
60%
What is the relative pH of seminal vesicles secretions, and why?
Alkaline - too protect spermatozoa from acidic environment in urethra and vagina
Where is the prostate gland located?
Inferior to the bladder and wrapped around the prostatic urethra
What proportion of semen is secreted by the prostate gland?
30%
What is the relative pH of secretions from the prostate?
slightly acidic
What is a distinctive component of seminal fluid from the prostate?
PSA - prostate-specific antigen
What is the function of PSA rich secretions from the prostate?
Contributes to sperm activation, viability and motility
How many bulbourethral glands do males have?
2
Where are the bulbourethral glands located?
In the urogenital diaphragm
Where do the bulbourethral glands open into?
The spongy/penile urethra
What proportion of semen is made by the bulbourethral glands?
5%
What is the function of bulbourethral glands secretions?
Lubrication and neutralise acidity in urethra prior to ejaculation
What proportion of semen is mace up of spermatozoa?
5%
What is a vasectomy?
Surgical method of male sterilisation where the ductus deferens are cut and then tied or cauterised.
What affect does a vasectomy have on the volume of semen?
No decrease in seminal fluid volume because glands unaffected. However, with no spermatozoa in semen, there is a 5% decrease in semen volume.
What is gametogenesis?
The formation of gametes/sex cells
What is the name for the process of gametogenesis in males?
Spermatogenesis
What is the name for the process of gametogenesis in females?
oogenesis
Are gametes diploid or haploid?
Haploid
What are the products of meiosis 1?
2 haploid cells are produced from 1 original diploid cell
What are the products of meiosis 2?
Each haploid cell produced from meiosis 1 divides to product 2 haploid cells with 23 chromosome.
What transformation occurs in spermatogenesis?
Spermatogonia are transformed to mature spermatozoa
What are the 2 types of spermatogonia after mitosis?
Type A and Type B
Where are spermatogonia/stem cells located before/during the first division?
The basement membrane of the seminiferous tubules
Where does the type A spermatogonium sit during spermatogenesis?
Stays at the basement membrane of the seminiferous tubule
Which spermatogonia (type A or B) will differentiate into a primary spermatocyte which will undergo meiosis 1?
Type B
What happens to primary spermatocytes in spermatogenesis?
They undergo meiosis 1 to form 2 secondary haploid spermatocytes
What happens to the 2 secondary spermatocytes formed from each cell in spermatogenesis?
Undergo meiosis 2 to form 4 total haploid round spermatic spermatids.
What is the shape of spermatids?
Round
What is the name of the process in which spermatids differentiate into spermatozoa?
Spermiogenesis
What is spermiogenesis?
The process of different ion of a round spermatid into spermatozoa with head, body and tail
Where are spermatozoa released after differentiation from spermatids?
The lumen of seminiferous tubules
What organelle is abundant in developing spermatozoa, and why?
Mitochondria - vital for motility
What is the general name for a hormone that acts on the gonads?
Gonadotropin
What does GnRH stand for?
Gonadotropin releasing hormone
Where is GnRH (gonadotropin releasing hormone) produced?
The hypothalamus
What hormones does GnRH stimulate the release of?
LH (luteinising hormone) and FSH (follicle stimulating hormone) from the anterior pituitary
What gonadotropins are released by the anterior pituitary?
LH (luteinising hormone) and FSH (follicle stimulating hormone)
Where is LH (luteinising hormone) produced?
The anterior pituitary gland
Where is FSH (follicle stimulating hormone) produced?
The anterior pituitary
What hormone is released from nurses/sertoli cells?
Inhibin
Where is inhibin produced in males?
Nurse cells in the testes
Where is testosterone produced?
Interstitial endocrine cells in the testes
What type of hormone is testosterone?
An androgen - type of steroid hormone
What is the function of androgens?
Responsible for male characteristics: maturation of sex organs, spermatogenesis, secondary sex characteristics, libido
What is the process of the negative feedback loop involved in male gonadotropin regulation?
GnRH released by hypothalamus, stimulates FSH (stimulates inhibin production) and LH (which stimulates testosterone production in testes), FSH and testosterone control spermatogenesis. Inhibin suppresses FSH production and testosterone suppresses LH and GnRH production, creating a negative feedback loop
