Lecture 35- Male reproductive system 2

Question 1

Why does the scrotum house the testes away from the body?

Answer 1

• Formation of sperm happens best at temp of 34 degree

- Housing testes outside of body where core temp is 37 degrees allows this

Question 2

What is the scrotum lined with? What is the function of this?

Answer 2

Dartos muscle= Can contract to wrinkle the skin to increase the surface area for regulating temp

Question 3

What is a second muscle in the scrotum that works to regulate temp in the testes?

Answer 3

Cremaster muscle= contracts for heat

conservation as brings testes closer to warm body

Question 4

How many spermatic chords are there and where are they found?

Answer 4

• Two spermatic cords

- Runs between abdomen and testes

Question 5

What do the spermatic chords contain?

Answer 5

• Ductus deferens (initial part)
• Blood vessels - testicular arteries and veins
• Nerves
• Lymphatics

Question 6

What is the vascular plexus in the the spermatic chord important for?

Answer 6

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)

Question 7

What is the dual function of the penis?

Answer 7

• Urination

- Copulation (gets sperm into female reproductive tract)

Question 8

What are the three parts of the penis?

Answer 8

• Root (bulb-connects to body)
• Body (is the mobile part)
• Glans covered by prepuce/foreskin (part that is circumcised)

Question 9

Explain the anatomical naming of the penis…

Answer 9

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)

Question 10

What the three erectile tissues that the penis contains?

Answer 10

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

Question 11

What is the part of the corpora cavernosa that sits in the root called?

Answer 11

Crus

Question 12

What makes up semen and what is its function?

Answer 12

• 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

Question 13

What makes up semen and what is its function?

Answer 13

• 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

Question 14

What three accessory glands produce seminal fluid?

Answer 14

• Seminal vesicles
• Prostate gland
• Bulbourethral glands

Question 15

Describe the seminal vesicles…

Answer 15

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

Question 16

Describe the Prostate glands…

Answer 16

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

Question 17

Describe the bulbourethral glands…

Answer 17

• 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

Question 18

What percentage of semen is spermatozoa?

Answer 18

5%

Question 19

What is a vasectomy?

Answer 19

-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%)

Question 20

What is gametogenesis? How does the name differ in males as opposed to females?

Answer 20

Formation of the gametes (sex cells)

• Spermatogenesis in males
• Oogenesis in females

Question 21

What is gametogenesis controlled and how does it occur?

Answer 21

• Under hormonal control

- Occurs via mitosis and meiosis as cells need to be haploid (23 chromosomes)

Question 22

What is spermatogenesis? Where does it occur?

Answer 22

• Formation of the male gamete
• The process by which spermatogonia are transformed to mature spermatozoa (sperm)
• Occurs in the seminiferous tubules

Question 23

When in life does spermatogenesis occur for males?

Answer 23

From puberty onwards however, the efficiency does decline with age

Question 24

What happens in the first stage of spermatogenesis?

Answer 24

-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

Question 25

What happens in the second stage of spermatogenesis?

Answer 25

-The second spermatogonia (type B) differentiates into a primary spermatocyte
(diploid), which undergoes meiosis I
-Forms 2 secondary spermatocytes (haploid
=23 chromosomes)

Question 26

What happens in third stage of spermatogenesis?

Answer 26

-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

Question 26

What happens in third stage of spermatogenesis?

Answer 26

-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

Question 27

What physical changes occur in the progression from spermatid to spermatozoon (singular for Singular for spermatozoa)? How long do these changes take?

Answer 27

• 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

Question 28

What is a Gonadotropin?

Answer 28

Hormone that acts on the gonads

Question 29

What three hormones are invovled in reproduction (both male + female)?

Answer 29

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

Question 30

What two hormones are invovled in male reproduction only?

Answer 30

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

Question 31

How does hormone regulation work in the male reproductive system? (include the negative feedback that occurs)

Answer 31

• 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

Question 32

How many sperm are produced from one spermatocytes?

Answer 32

4, as goes through two divisions in meiosis