Lecture 17: The male reproductive tract

Question 1

What are the testicles:

- what is the plural and and singular form of the testicles. - where are located and where do they form

Answer 1

Humans have 2 testis (singular) that are called Testes or testicles.
They are located in the scrotum, but form in the abdominal cavity and prior to birth descend through the inguinal canal to the scrotum

Question 2

What is the term for a male whos testes do not descend. What does this cause them

Answer 2

Cryptorchidism. This causes them to be infertile and prone to testicular cancer

Question 3

What is the greek root for testes

Answer 3

Orkhis

Question 4

Describe the course of sperm as it traverses the male reproductive tract

Answer 4

Mature sperm produced in the seminiferous tubules fall off into the liquid produced by the seminiferous tubules, moving down into the Rete Testis. These drain into a single duct at the tail of the epididymis. Sperm then go to Vas Deferens which runs from the caudal end of the epididymis through the inguinal canal, looped back up and over the bladder and joins to the ejaculatory duct. Then sperm travel down the ejaculatory duct through the prostate to the urethra to tip of penis

Question 5

What is the Rete testis

Answer 5

Centrally placed duct system in the testes that connects the seminiferous tubules to the epididyis.

Question 6

What does the seminiferous tubules in the testes look like

Answer 6

There are ~80 convoluted tubes in testes

Question 7

What is the epididymis structure location

Answer 7

It runs around the outside of the testicle from the top to the bottom containing the ductus epididymis where sperm keep maturing.

Question 8

What happens to the sperm when it enters the epididymis and how long are they there for

Answer 8

Sperm spend 10-14 days passing through the epididymis to acquire the ability to be motile and to fertilise. The epididymis also reasbsorbs liquid produced from the seminiferous tubules from around the sperm, increasing the concentration of the sperm.

Question 9

What is the structure and function of vas deferens

Answer 9

The Vas deferens are 45cm long they run from the epididymis up through the inguinal canal then up and around the bladder (going behind) then, approaching the prostate gland from behind join back down to the ejaculatory duct. They are the major site of sperm storage where sperm can be stored for months.

Question 10

What is the ampulla of ductus vas deferens

Answer 10

It is the widening of the duct just before it opens to the ejaculatory duct. At this site there is much more concentrated sperm storage.

Question 11

Compare the structure and function of the ejaculatory duct with the Urethra

Answer 11

Long tube that runs from the end of the vas deferens, through the prostate gland to the urethra.
The Urethra is a 20cm long tube that runs from the bladder, through the prostate and to the end of the penis.
Both ducts cross at a T junction in the prostate gland.

Question 12

What is the structure and function of the seminal vesicles

Answer 12

They are secretory glands that secrete a mucoid substance which is emptied into the ejaculatory duct directly after sperm is ejected from the vas deferens, which washes it down.

Question 13

What is the characteristics of the secretion of the seminal vesicles

Answer 13

A sticky substance that is:
Alkaline, containing fructose as an energy source for sperm, containing prostaglandins which may induce contractions in the female reproductive tract and contains clotting proteins which helps sperm to stick to the female reproductive tract and not be removed by intercourse

Question 14

What is order of components of the ejaculate

Answer 14

1. Seminal fluid 2. Sperm. 3. Prostatic fluid (technically sperm first)

Question 15

Describe structure and function of the prostate gland

Answer 15

A doughnut shaped organ, that is golf ball sized. It secretes prostatic fluid into the urethra ahead of sperm during ejaculation

Question 16

What is the characteristics of the secretion of the Prostate

Answer 16

• Slightly acidic.
• Contains Citrate (for ATP)
• Milky colour bc it
• Contains phosphate + calcium
• Prostate specific antigen and other enzymes to break down the coagulum

Question 17

How does the two secretions make a good pH for the sperm (7.5)

Answer 17

The seminal vesicle secretion is slightly alkaline, while the prostatic secretion is slightly acidic (6.5) and these neutralise each other, forming a buffer

Question 18

What is the volume % of components of semen. what is the range of volume for ejaculate

Answer 18

Total volume: 1.5-5 mL 
10% Sperm
60% Seminal vesicle fluid
30% Prostatic fluid
Other secretions have small amounts.

Question 19

Describe how Benign prostatic hyperplasia happens

Answer 19

There is excess growth of the prostatic tissue, but as it is encapsulated it cannot expand that much outwards. This causes some occluding of the urethra

Question 20

What is the consequences of benign prostatic hyperplasia

Answer 20

There is difficulty in voiding the bladder. This eventually causes weakening of the bladder and can lead to urinary infections ascending the tract, leading to infection in the kidneys

Question 21

What is the incidence of Benign Prostatic Hyperplasia

Answer 21

It is rare in men <40, but from 50 onwards it increases from 17% to 35% and in men over 85 there is 90%.

Question 22

How is Benign Prostatic hyperplasia treated

Answer 22

-Surgery on the prostate gland,
- Selective 5alpha reductase inhibitors such as Finasteride and dutasteride which stop the prostate enlarging or shrink it as they stop testosterone being converted to DHT
- Prostatic urethral lift
(where metal wire with hook introduced in the urethra hold the gland to the side to make the urethra bigger.

Question 23

Describe the incidence of Prostate cancer and how it is detected

Answer 23

It is the most common cause of cancer deaths worldwide, but only 29% of all cases of cancer. It affects older men. It is detected for looking for Prostate specific antigen in blood.

Question 24

Why does better detection of prostate cancer doesn’t lead to more survivals

Answer 24

There is some over diagnosis, most of the time prostatic cancer isn’t bothering the patient and there is a lot of false positives of the screening too. As a result of prostatectomy, there is some side effects: erectile dysfunction, 1 death, urinary incontinence

Question 25

What are some treatments for prostate cancer

Answer 25

Watchful waiting

• Androgen depletion by 5a reductase inhibitors, castration or inhibitors of androgen synthesis
• Inhibition of testosterone action- (blocking the receptors)
• Surgery: prostatectomy (removal of the prostate gland)

Question 26

what are the 3 major structures of the penis and their function

Answer 26

1. Corpora cavernosa x 2 which are the main erectile tissues
2. Corpus spongiosum which surround the penile urethra and prevents occlusion during erection
3. Penile urethra which conducts semen (and urine)

Question 27

What are the events that cause erection

Answer 27

Following sexual stimulation

• release of NO and Prostaglandin E1 causes the smooth muscle of the corpora cavernosa to relax
• Blood fills the cavernous spaces of the corpora cavernosa (8x more than flaccid)
• Engorgement of the corpora occludes the venous draining, which keeps it engorged

Question 28

How does Viagra work

Answer 28

It inhibits the enzyme #5phosphodiesterase which breaks down GMP ( a 2nd messenger that helps smooth muscle relax by reducing intracellular Ca2+). This leads to increase GMP and therefore relaxation of arteries that supply the corpora cavernosa and erection