Lecture 35 - Male reproductive system II

Question 1

Flow of sperm

Answer 1

Production of sperm in the testes which are transported via the rete testis and efferent ductless into the head of the epididymis and then the tail of the epididymis which is continuous with the ductus deferns, passing through the inguinal canal posterior to the bladder where it widens to form an ampulla then there is a short ejaculatory duct which goes on to form the urethra which is separated into 3 parts called the prostatic, membranous and spongy/penile urethra

Question 2

The scrotum contains

Answer 2

Two testes (singular is testis) - the two testes are separated by a fibrous septum 
Two epididymides (singular is epididymis) - each one is associated with the posterior border of the testes 
Two spermatic cords (with part of the ductus deferens) - run from the testis up through the inguinal canal which passes up to the abdominal cavity 

The scrotum is the sack of skin that encloses the testes and it is quite thin skin which is lined with a superficial fascia

Question 3

Inguinal canal

Answer 3

The inguinal canal is a short passage that extends inferiorly and medially through the inferior part of the abdominal wall. The canal serves as a pathway by which structures can pass from the abdominal wall to the external genitalia.

Question 4

Why is the scrotum outside of the body?

Answer 4

The scrotum hoses the testes away from the body to maintain temperature at 34 degrees
Optimum temperature for spermatogenesis is 34 degrees which is several degrees lower than the normal body temperature
By housing the testes outside within the scrotum, it gives the body a mechanism by which it can control differences in temperature

Question 5

3 mechanism for heat transfer - the scrotum

Answer 5

Scrotum is lined by the dartos muscle - lines the skin of the scrotum and what happens when this muscle contracts is that it wrinkles the skin which changes the surface area available for heat exchange so when it is all wrinkled up, less heat exchange occurs, helps to maintain and keep temperature (the opposite can occur too)

Cremaster muscle that contracts for heat conservation - Muscle that encloses the testis and spermatic cord, when this muscle contracts it draws the testis up closer to the body which allows the warming up of the testis if this is required. Contracts for heat conservation and it also contraction during arousal which brings the testes closer to the body which offers protection during sexual intercourse

Venous plexus or pampiniform plexus - veins form a net structure around the artery known as a venous plexus which provides an increased surface area to allow heat transfer between the warmer blood coming down from the body in the artery and the cooler blood being returned from the testes back up towards the body

Question 6

Dartos muscle

Answer 6

Scrotum is lined by the dartos muscle - lines the skin of the scrotum and what happens when this muscle contracts is that it wrinkles the skin which changes the surface area available for heat exchange so when it is all wrinkled up, less heat exchange occurs, helps to maintain and keep temperature (the opposite can occur too)

Question 7

Cremaster muscle

Answer 7

Cremaster muscle that contracts for heat conservation - Muscle that encloses the testis and spermatic cord, when this muscle contracts it draws the testis up closer to the body which allows the warming up of the testis if this is required. Contracts for heat conservation and it also contraction during arousal which brings the testes closer to the body which offers protection during sexual intercourse

Question 8

Venous plexus

Answer 8

Venous plexus or pampiniform plexus - veins form a net structure around the artery known as a venous plexus which provides an increased surface area to allow heat transfer between the warmer blood coming down from the body in the artery and the cooler blood being returned from the testes back up towards the body

Question 9

The spermatic cord

Answer 9

Two spermatic cords
Within the scrotum
Runs between the abdomen and testes (run between the superior part of the testes and up into the inguinal canal)
Contains the ductus deferns, blood vessels - testicular arteries and veins, nerves and lymphatics

Question 10

The penis

Answer 10

Dual function of urination and copulation (sexual intercourse)

Cylindrical organ
Root (bulb) (this is the part that adheres to the body wall)
Body (mobile part)
Glans covered by prepuce/foreskin (removed if a male is circumcised)

Question 11

Three cylindrical erectile tissues in the penis

Answer 11

Two corpora cavernosa (singlar = corpus cavernosum)
This is the main erectile tissue and it is located on the Doral aspect

One corpus spongiosum
Contains the urethra, forms the bulb and the glans (starts at the root, goes through the body and also widens and expands to form the glans penis)
Ventral aspect of the penis

Question 12

Corpora cavernosa (corpus cavernosum)

Answer 12

Two corpora cavernosa (singlar = corpus cavernosum)

This is the main erectile tissue and it is located on the Dorsal aspect

Question 13

Corpus spongiosum

Answer 13

One corpus spongiosum
Contains the urethra, forms the bulb and the glans (starts at the root, goes through the body and also widens and expands to form the glans penis)
Ventral aspect of the penis

Question 14

Dorsal aspect of the penis

Answer 14

When erect, the dorsal side lies on the body

Dorsal vasculature - arteries, veins and nerves coming into the penis

Question 15

Ventral aspect of the penis

Answer 15

When erect, the ventral side lies outwards. The ventral side lies on the scrotum

Question 16

Optimum temperature for the scrotum

Answer 16

34 degrees

Question 17

What vessels supply the testes?

Answer 17

Testicular artery
Venous plexus
Lymphatic vessels
And nerves supply the testes

Question 18

Three accessory glands

Answer 18

Seminal vesicles
Prostate gland
Bulbourethral glands

Question 19

Seminal fluid

Answer 19

Spermatozoa are carried to the female reproductive tract in the seminal fluid (together called semen)

Seminal fluid has some very important functions in terms of when it is ejaculated into the female reproductive tract, things the seminal fluid is responsible for is providing a transport medium for the sperm, provide a nutrient and energy source for the sperm, provide protection (specifically to the acidity of the male urethra but also within the vagina of the female) and they also help to activate the spermatozoa which gets the flagella to start beating so that the sperm can become motile

Question 20

Seminal vesicles

Answer 20

Two glands that are located posterior to the bladder, and lateral to the ampulla of the ductus deferens
Produce viscous secretion which makes up 60% of semen, alkaline pH which protects the sperm against the acidic environment in the urethra and vagina

Question 21

Prostate gland

Answer 21

Located inferior to the bladder, wraps around the prostatic urethra
Procduces secretion - 30% of semen, it is slightly acidic and milky fluid, contains PSA which is prostate specific antigen, contributes to sperm activation, viability and motility

Question 22

Bulbourethral glands

Answer 22

Two glands located in the urogenital diaphragm
Open into the spongy/penile urethra
Contributes 5% of semen volume - released first, about lubricating the urethra and neutralises/removing residual urine and therefore any residual acidity that was left
Secretions lubricate and neutralise the acidity in the urethra prior to ejaculation

Question 23

Components of semen

Answer 23

60% from the seminal vesicles
30% from the prostate
5% from the bulbourethral glands
Last 5% is made up of sperm which is what is being transported from the testes to the epididymis

Question 24

Vasectomy

Answer 24

Surgical method of sterilisation in males
Cut the ductus deferens - ends are tied or cauterised
If you have a vasectomy you are not going to get the transport of sperm up from the testes up into the ampulla so that 5% that makes up the semen is no longer to be there so it is a minor reduction

Question 25

Gametogenesis

Answer 25

Formation of the gametes (sex cells)
Spermatogenesis in males, oogenesis in females
Under hormonal control
Occurs via mitosis (somatic cell division) and meiosis (cell division that produces daughter cells that are haploid) - cells need to be haploid i.e. contain 23 chromosomes

Question 26

Brief overview of meiosis

Answer 26

Same basic process for males and females
Original cell has 46 chromosomes (diploid = 2n)
Two cycles of cell division to produce gametes (23 chromosomes which is haploid = n)

Meiosis 1 - 2 haploid cells produced from 1 original diploid cell
Meiosis 2 - Each cell produced from meiosis 1 dives to produce two haploid cells with 23 chromosome cells

Question 27

Meiosis 1

Answer 27

Meiosis 1 - 2 haploid cells produced from 1 original diploid cell

Question 28

Meiosis 2

Answer 28

Meiosis 2 - Each cell produced from meiosis 1 dives to produce two haploid cells with 23 chromosome cells

Question 29

Spermatogenesis

Answer 29

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

Question 30

Spermatogenesis process

Answer 30

Works from the basement membrane and then works outwards to form spermatozoa in the lumen

Part 1 
Spermatogonia divide by mitosis into 2 daughter cells (diploid = 46 chromosomes) 
One spermatogonium (type A) stays at the basement membrane of the seminiferous tubule - in order to allow the process to keep on repeating and to initiate the next round of mitosis 

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

Part 3
These undergo meiosis II to form spermatids (haploid)
Spermatids differentiate into spermatozoa with a head, body and tail via spermiogenesis
Spermatozoa are released into the lumen

Question 31

Mature sperm features

Answer 31

Head, neck, mid piece and tail

The head encloses a very condensed nucleus
Acrosome is a sac of enzymes that lies over the nucleus within the head of the spermatozoa - these enzymes are important in penetrating the oocyte during fertilisation
Get rid of excess cytoplasm in order to become streamline
When the spermatozoa are ejaculated up into the female vagina they have to be able to make their way into the uterine tube which requires energy and therefore need mitochondria which are found concentrated in the mid piece of the spermatozoa

Question 32

Name the reproductive hormones

Answer 32

GnRH = gonadotropin releasing hormone produced by the hypothalamus (note - gonadotropin = hormone that acts on the gonads) 
LH = Lutenizing hormone (a gonadotropin) produced by the anterior pituitary
FSH = Follicle stimulating hormone (a gonadotropin) produced by the anterior pituitary

Question 33

Gonadotropin

Answer 33

gonadotropin = hormone that acts on the gonads

Question 34

GnRH

Answer 34

GnRH = gonadotropin releasing hormone produced by the hypothalamus

Question 35

LH

Answer 35

LH = Lutenizing hormone (a gonadotropin) produced by the anterior pituitary

Question 36

FSH

Answer 36

FSH = Follicle stimulating hormone (a gonadotropin) produced by the anterior pituitary

Question 37

Hormones in males

Answer 37

Inhibin

Testosterone

Question 38

Inhibin

Answer 38

Important role is negative feedback regulating spermatogenesis
From the nurse (Sertoli) cells

Question 39

Testosterone

Answer 39

Produced by interstitial endocrine (Leydig) cells

Type of androgen - a group of steroid hormones, group of hormones that have effects on stimulating male reproductive mechanisms, responsible for male characteristics (such as maturation of sex organs, spermatogenesis, secondary sec characteristics that include hair growth and deepening of the voice, libido (sex drive)), synthetic androgens (steroids) have therapeutic purposes and they are also abused for sporting purposes

Question 40

Negative feedback loop with FSH and LH and testosterone

Answer 40

LH stimulates production of testosterone (intersitial endocrine (Leydig) cells)
FSH and testosterone control spermatogenesis
FSH stimulates inhibin production (nurse (sertoli) cells) - Inhibin is released into the circulation and provides negative feedback back up to the anterior pituitary regulating the production of specifically FSH

Negative feedback:
Inhibin suppresses FSH
Testosterone surpasses LH and GnRH

General process ….

• Hypothalamus produces GnRH
• Release of GnRH stimulates the release of LH and FSH from the anterior pituitary gland
• LH acts on the interstitial endocrine cells and stimulates the production of testosterone and testosterone acts locally within the semifernous tubules and other ducts within the male reproductive system but it also is released into the circulation where it can have its effects all around the body and one of these effects is to take messages back up to the hypothalamus and anterior pituitary as negative feedback so lots of restoring going back up which reduces the amount of testosterone which decreases the of production of LH and FSH

Question 41

______ spermatozoa are produced from _____ primary spermatocyte

Answer 41

Four

One

Question 42

Spermatogenesis

Answer 42

Maturation of spermatid into spermatozoa (head, midpiece, tail)

Question 43

Sperm formation - names flow chart

Answer 43

Spermatozoa to spermatozoon (plural of this is spermatozoa) (round spermatic cells to structurally mature spermatozoon)