Male Reproductive Anatomy & Physiology Flashcards
For a male mammal to reproduce, they must?
(4 points)
- Reach sexual maturity
- Produce viable sperm in sufficient quantity
- Accomplish mating successfully
- Provide parental care (in some species)
Name the 4 main general features of the male reproductive system
- Gonads (testes) for gamete (spermatozoa)
- Tubes to carry sperm (vas deferens)
- Accessory glands to provide semen, nutrients & protection for sperm
- Penis ( & baculum in somespecies) for copulation
What are the 2 functions of the testes?
- Produce gametes (sperm through spermatogenesis
- Secrete hormones (testosterone)
What does the spermatic cord contain?
- Vas deferens
- Blood vessels
- Nerves supplying testes
What is the structure of the testes?
- Septa divide testes into 250 - 300 lobules
- Each lobule contains 1-3 coiled seminiferous tubules with surrounding connective tissue
What is the function of Sertoli cells?
Where are they located?
- Stimulate cells that form the sperm
- Produce androgen binding protein
- Produce hormones - inhibin & oestadiol
- Located within tubules
What do Sertoli cells produce?
• Androgen binding protein – concentrates
testosterone & dihydrotestosterone (DHT)
that stimulate spermatogenesis
• Inhibin – inhibits FSH production
• Oestradiol – negative feedback on
hypothalamic GnRH production
What are Leydig cells & where are they located?
- Interstitial cells
- Secrete testosterone in presence of LH
- Located in tissue between tubules
What is the epididymis?
Highly convoluted duct on outer surface of testes
Where do sperm mature & where are they stored?
Epididymis & vas deferens
What is the vas deferens?
- Pained ducts that connect epididymis to urethra
- Also connects to a short duct within seminal vesicle (forms ejaculatory ducts)
What is the urethra used for?
- Sperm & seminal fluid
- Urine
What 3 chambers of tissue can be found in the body of the penis?
- Pair of corpora cavernosa on dorsal side
- Corpus spongiosum on ventral side
What does urethra pass through?
The corpus spongiosum to its opening (the meatus) at the tip of the glans penis
What is an erection controlled by?
A reflex arc that is mediated in the sacral spinal cord
What does nitric oxide & cGMP do?
- Nitric oxide - dilates arteries
- cGMP - causes relaxation of smooth muscle in corpus cavernosum
- Results in high blood flow into penis
What is a baculum?
- Penis bone
- Helps maintain stiffness during intercourse
What are seminal vesicles?
Paired glands of base of vas deferens
produce about 60% of the total seminal fluid
What is the function of seminal fluid?
Acts as a lubricant, pH buffer, & contains nutrients
What nutrients does the seminal fluid contain?
- Fructose (energy source)
- Vitamin C
- Prostaglandins (stimulate muscular contraction)
What is semenogelin?
A protein involved in formation of gel matrix that encases ejaculated sperm, preventing capacitation
What is the function of the prostate gland?
(4 points)
- Produces 30 % of semen
- Helps neutralise acidity of vaginal tract to aid sperm motility
- Produces clotting enzymes to keep sperm in f reproductive tract
- Produces prostate - specific antigens to break down semen ‘clot’ to release sperm
What does the bulbourethral gland produce?
- Drops of seminal fluid as pre-ejaculate
- Lubricates urethra for sperm
What are ampullary glands?
Small glands located where vas deferens opens into urethra
What is the purpose of the scrotum?
- Keeps testes ~2°C lower than body temp (35C)
- Sperm development is impaired at higher/lower temps
What muscles contract when it is cold and relax when it is warm?
- Cremaster muscle
- Dartos muscle
- Draws testes closer to body to provide warmth
Give 2 examples of animals that have internal testes
- Elephants
- Rhinos
What are intestinal testes also referred to?
Abdominal testes
Why do marine mammals not have external testes?
Would affect streamlined shapes & create drag
What type of testes do marine mammals have?
- Internal
- Use an elaborate vascular countercurrent heat exchanger to keep temp below body temp for optimum function
What are the several hypotheses for internal testes?
- Early primitive mammals had lower temperatures & their testes worked efficiently within their body
- Ancestor of eutherian mammals was a small mammal that required large testes form sperm competition (had to be placed outside body)
- Enzymes in spermatogenesis evolved an optimum temp slightly less than core temp, when animals became larger, they were stuck with enzymes that operated best at cooler temps
- Protects testes from abdominal cavity pressure changes caused by jumping/galloping
What is sperm competition?
Where more than 1 m mates with a f, sperm from 2 or more males must compete to fertilise ova within a f reproductive tract
What is the term for undescended testes?
Cryptorchidism
What is cryptorchidism?
Undescended testes
How is cryptorchidism resolved?
- Often by itself
- If not, an orchidopexy is performed before 1y/o
What causes testicular torsion?
Twisting of spermatic cord (usually affects 1 testis)
What is phimosis?
The opening of the tip of the foreskin is too narrow, so it cannot be retracted over head of penis
What are the issues with phimosis + how can it be resolved?
- Weak urinary flow & painful erection
- Circumcision
What is hypospadias?
- A congenital condition
- Opening of urethra is on underside of penis
- Corrected by surgery
What can erectile dysfunction be treated with?
Sildenafil (Viagra)
How does viagra work?
- By inhibiting phosphodiesterase 5
- In turn, inhibits hydrolysis of cGMP to GMP
- Enhances effect of NO
- Penile vasodilation is sustained
Where in the testes are the sperm produced?
Epithelial lining of seminiferous tubules
Why do marsupials have a bifurcated penis?
Female’s vagina has 2 lateral branches of vagina leading to 2 separate uteri
List the main 3 male accessory glands
- Prostate gland
- Seminal vesicles
- Bulbourethral gland
What is the main role of semen?
Provides protective, buffering medium for spermatoazoa
What is the role of prostaglandins in semen?
Stimulate contractions of female uterus + aid sperm movement
What is semenogelin & what does it do?
Protein involved in formation of a gel matrix that encases ejaculated sperm, preventing capacity ion
