Lecture 21 - Sperm Production and Delivery

Question 1

Internal genitalia of a male

Answer 1

Testes (gonads) —> make sperm

Series of ducts and glands —> helps with maturation of the sperm or secrete fluids to help keep sperm viable. They support and move sperm to the external genitalia

Question 2

External genitalia of a male

Answer 2

Urethra and penis —> deliver sperm

Scrotum —> keeps the testes outside the abdominopelvic cavity for temperature regulation

Question 3

Function of male reproductive system

Answer 3

Manufacture sperm (gametes) and to deliver them to an ovum in viable form

Question 4

Function of urethra and penis in male reproductive system

Answer 4

Responsible for depositing sperm in female reproductive tract and ofc pleasurable sensations ;)

Question 5

What are the 3 parts that make up the scrotum? What is its function?

Answer 5

Skin, dartos muscle and superficial fascia

Used to support testes

Question 6

Where is sperm produced?

Answer 6

From germ cells within the seminiferous tubules of the testes

Question 7

What is spermatogenesis and what are its 4 cellular stages?

Answer 7

The process of generating sperm from spermatogonia. 4 cellular stages:

1. Spermatogonium
2. Spermatocyte
3. Spermatid
4. Sperm

Question 8

What does gametogenesis involve?

Answer 8

Gametogenesis (including spermatogenesis) involves meiosis as well as mitosis

Meiosis is when a dividing germ cell splits its paired chromosomes between its offspring, rather than duplicating them

Question 9

Total time needed to complete the stages of spermatogenesis

Answer 9

~2 months

Question 10

Time needed for each stage of spermatogenesis

Answer 10

Meiosis of a spermatogonium - 16 days
Meiosis I - 24 days
Meiosis II - hours
Spermatogenesis (physical maturation) - 24 days

Total ~64 days

Question 11

Describe the movement of spermatogenesis

Answer 11

As developing gametes progress from spermatogonium -> spermatocyte -> spermatid -> sperm, they move from the basal layer of the seminiferous tubule towards the lumen, while maintaining contact with the Sertoli cells

Question 12

Structure of a sperm

Answer 12

• Acrosome (tip): contains enzymes needed to penetrate an ovum during fertilization
• Head: contains haploid chromosomes
• Neck
• Middle piece: contains mitochondria which generate ATP to keep the tail moving
• Tail: flagellum; a motile organelle that moves the sperm

Question 13

True or False. An anatomically mature sperm is functionally (physiologically) mature.

Answer 13

False. When a sperm detaches from the Sertoli cells and enters the rete testes, it has all structures but it is still incapable of going through the process of fertilization

Question 14

What occurs in the epididymas and what do epididymal cells secrete? How does it affect the sperm maturation process? What is the transit time through the epididymis?

Answer 14

Physiological maturation of sperm. It secrets immobilin which keeps sperm immotile

It secrete factors which promote maturation process resulting in:
- Compaction of genetic material
- Alteration of sperm plasma membrane
- Maturation of the acrosome proteins

Transit time of sperm through the epididymis is 10-15 days

Question 15

Where do sperm travel through, where they can also be stored?

Answer 15

Transported from the epididymis to the vas deferens/ductus deferens

While sperm travel through the vas/ductus deferens they are inactivated and can be stored this way in the ampulla for several months

Question 16

Capacitation

Answer 16

The process by which sperm become motile and are capable of fertilization (ie. can penetrate the cell membrane of an ovum)

The first stage of capacitation (motility) occurs in the ejaculatory duct when sperm mix with seminal fluid that is secreted from seminal glands (vesicles)

Question 17

How do the autonomic and somatic nervous systems influence penile tissue?

Answer 17

Parasympathetic fibres - innervate the erectile tissue. During arousal, relaxes smooth muscle in this tissue, allowing increased blood flow that fills that vascular spaces, causing an erection

Sympathetic fibres - innervate the epididymis, vas deferens, and seminal vesicles. When activated, sperm and secretion are moved into the urethra

Lumbosacral somatic motor neurons - innervate the skeletal muscles at the base of the penis. During ejaculation, spinal reflex produces rhythmic contractions in these muscles (aka orgasms), which helps push semen out the urethra

Question 18

How does HPG axis regulation affect the male reproductive system

Answer 18

GnRH is secreted from the hypothalamus, creating pulses of increased LH and FSH secretion from the anterior pituitary

*if the rhythm of pulsatile GnRH secretion is disrupted, testicular functions are impaired

Question 19

How do gonadal hormones cooperate to regulate sperm production?

Answer 19

• Leydig cells: activation directs androgen synthesis and release
• Sertoli (nurse) cells: activation promotes spermatogenesis and also produce inhibin, a regulatory hormone

Sertoli cells also enhance sperm function in many ways:
- Maintain the blood-testis barrier
- Maintain spermatogonia numbers
- Direct spermatocytes to complete meiosis
- Promote adhesion and development of spermatids

Question 20

How do gonadal hormones provide negative feedback to the HPG axis?

Answer 20

Androgenic negative feedback mostly occurs at the hypothalamus

Inhibin has a major role in inhibiting the secretion of gonadotropes (FSH and LH) found in the anterior pituitary