Lecture 35- Male reproductive system 2 Flashcards
Why does the scrotum house the testes away from the body?
- Formation of sperm happens best at temp of 34 degree
- Housing testes outside of body where core temp is 37 degrees allows this
What is the scrotum lined with? What is the function of this?
Dartos muscle= Can contract to wrinkle the skin to increase the surface area for regulating temp
What is a second muscle in the scrotum that works to regulate temp in the testes?
Cremaster muscle= contracts for heat
conservation as brings testes closer to warm body
How many spermatic chords are there and where are they found?
- Two spermatic cords
- Runs between abdomen and testes
What do the spermatic chords contain?
- Ductus deferens (initial part)
- Blood vessels - testicular arteries and veins
- Nerves
- Lymphatics
What is the vascular plexus in the the spermatic chord important for?
Plexus increases surface area allowing for heat exchange between the warm blood coming into the testes and cooler blood returning from the testes (temp regulation)
What is the dual function of the penis?
- Urination
- Copulation (gets sperm into female reproductive tract)
What are the three parts of the penis?
- Root (bulb-connects to body)
- Body (is the mobile part)
- Glans covered by prepuce/foreskin (part that is circumcised)
Explain the anatomical naming of the penis…
When flaccid ventral penis lies adjacent to scrotum while visible one is dorsal- where purple layers of erectile tissue is (labelled as if it was erect)
What the three erectile tissues that the penis contains?
Two corpora cavernosa (corpus cavernosum):
- Main erectile tissue
- Runs each side
- Dorsal aspect
One corpus spongiosum:
- Contains urethra (therefore not main erectile tissue as don’t want urethra to be blocked when contracts)
- Forms bulb and glans
- Ventral aspect
What is the part of the corpora cavernosa that sits in the root called?
Crus
What makes up semen and what is its function?
- Semen= spermatozoa +seminal fluid
- Function is to provide medium for transport into female reproductive tract. Also nourishes, energy source, protects from acidity and activates (become mobile) spermatozoa
What makes up semen and what is its function?
- Semen= spermatozoa +seminal fluid
- Function is to provide medium for transport into female reproductive tract. Also nourishes, energy source, protects from acidity and activates (become mobile) spermatozoa
What three accessory glands produce seminal fluid?
- Seminal vesicles
- Prostate gland
- Bulbourethral glands
Describe the seminal vesicles…
Two glands located:
- posterior to bladder
- lateral to ampulla
Produce viscous secretion:
- Makes up 60% of semen
- Alkaline pH protects sperm against acidic environment in urethra and vagina
Describe the Prostate glands…
Location:
- Inferior to bladder
- Wraps around prostatic urethra
Produces secretion:
- 30% of semen
- Slightly acidic, milky fluid
- Contains PSA: prostate-specific antigen
- Contributes to sperm activation, viability and motility
Describe the bulbourethral glands…
- Two glands located in the urogenital diaphragm
- Open into spongy/penile urethra
- Contribute 5% of semen volume
- Secretions lubricate and neutralize acidity in urethra prior to ejaculation
What percentage of semen is spermatozoa?
5%
What is a vasectomy?
-Surgical method of sterilization in males
-Cut the ductus deferens (cut ends tied or
cauterized)
-Does not effect the volume of seminal fluid as the glands that produce this are after the cut but will effect the volume of semen as spermatozoa will not be released (make up 5%)
What is gametogenesis? How does the name differ in males as opposed to females?
Formation of the gametes (sex cells)
- Spermatogenesis in males
- Oogenesis in females
What is gametogenesis controlled and how does it occur?
- Under hormonal control
- Occurs via mitosis and meiosis as cells need to be haploid (23 chromosomes)
What is spermatogenesis? Where does it occur?
- Formation of the male gamete
- The process by which spermatogonia are transformed to mature spermatozoa (sperm)
- Occurs in the seminiferous tubules
When in life does spermatogenesis occur for males?
From puberty onwards however, the efficiency does decline with age
What happens in the first stage of spermatogenesis?
-Spermatogonia (sperm stem cells) divide
by mitosis into 2 daughter cells (diploid - 46
chromosomes)
-One spermatogonium (type A) stays at the
basement membrane of the seminiferous
tubule
What happens in the second stage of spermatogenesis?
-The second spermatogonia (type B) differentiates into a primary spermatocyte
(diploid), which undergoes meiosis I
-Forms 2 secondary spermatocytes (haploid
=23 chromosomes)
What happens in third stage of spermatogenesis?
-These undergo meiosis II to form spermatids
(haploid)
-Spermatids differentiate into spermatozoa with a head, body and tail via spermiogenesis
-Spermatozoa released into lumen of seminiferous tubules
What happens in third stage of spermatogenesis?
-These undergo meiosis II to form spermatids
(haploid)
-Spermatids differentiate into spermatozoa with a head, body and tail via spermiogenesis
-Spermatozoa released into lumen of seminiferous tubules
What physical changes occur in the progression from spermatid to spermatozoon (singular for Singular for spermatozoa)? How long do these changes take?
- Develop acrosome= Membrane bound vesicle contains enzymes (important for fertilization)
- Develop midpiece= has mitochondria (energy needed to drive movement via flagella)
- Develop a more defined head= get rid of excess cytoplasm as this makes spermatocyte slower
Takes approx. 24 days
What is a Gonadotropin?
Hormone that acts on the gonads
What three hormones are invovled in reproduction (both male + female)?
GnRH
-gonadotropin releasing hormone produced by the hypothalamus
LH
-Luteinizing hormone (a gonadotropin) produced by the anterior pituitary
FSH
-Follicle stimulating hormone (a gonadotropin) produced by the anterior pituitary
What two hormones are invovled in male reproduction only?
Inhibin
-from nurse (Sertoli) cells
Testosterone
-Produced by interstitial endocrine (Leydig) cells
-Type of androgen
-Group of steroid hormones
-Responsible for male characteristics
(maturation of sex organs, spermatogenesis,
secondary sex characteristics, libido)
-Synthetic androgens (steroids) have therapeutic purposes and are often abused
How does hormone regulation work in the male reproductive system? (include the negative feedback that occurs)
- GnRh released by the hypothalamus stimulates release of LH and FSH from the anterior pituitary
- LH stimulates production of testosterone (interstitial endocrine cells)
- FSH stimulates Inhibin production (nurse cells)
- Therefore together FSH and testosterone control spermatogenesis
Negative feedback…
- Inhibin suppresses FSH
- Testosterone suppresses LH & GnRH
How many sperm are produced from one spermatocytes?
4, as goes through two divisions in meiosis
