Male Reproductive System

Question 1

Function

Answer 1

Production of androgens
Production, nourishment, storage of male gametes
Introduction of male gametes into female reproductive tract

Question 2

Components

Answer 2

Testes
Scrotum
Ducts:
- epididymal
- vas deferens
- urethra
Glands:
- seminal vesicles
- prostate
- bulbourethral
Penis

Question 3

Testes & scrotum

Answer 3

4cm long, 2.5cm diameter
Enclosed in sac = scrotum
Scrotal septum seperates scrotum in 2 parts
Each testes is suspended from spermatic chord
Passes through inguinal canal to/from abdominal cavity
–> Testes:
Contains.. Vas deferens, testicular artery, cremasteric artery, testicular venous plexus, lymph vessels, nerves

Question 4

What are the 2 tissue layers covering the testes?

Answer 4

Tunica vaginalis
- thin serous outer layer
Tunica albuginae
- white coat
- tough fibrous inner layer (divides testes into testicular lobules)

Question 5

Testicular lobules

Answer 5

Each testes is divided into 300 by each tunica albuginea
Each lobule contains 1-4 seminiferous tubules
Site of spermatogenesis

Question 6

What are seminiferous tubules?

Answer 6

Walls formed of sertoli cells
Sertoli cells secrete nutrients for developing spermatozoa
Spermatogenic cells are in the walls(most immature by basement membrane)
At maturity, sperm released into the lumen

Question 7

What is mitosis?

Answer 7

Division of parent cell into 2 daughter cells that are genetically identical
Diploid (2n)

Question 8

What is meiosis?

Answer 8

Division of parent cells into 4 daughter cells with half the number of chromosomes
Haploid (n)
Forms gametes

Question 9

Spermatogenesis

Answer 9

1. Diploid spermatogenia duplicte –> diploid primary spermatocytes
2. Primary spermatocytes divide into 2 haploid daughter cells –> secondary spermatocytes
3. Secondary spermatocytes divide into 4 haploid daughter cells = spermatids
4. Development of spermatids into mature spermatozoa

Question 10

Structure of sperm

Answer 10

Head —- acrosome (outer) nucleus (inner)
Neck
Middle piece —- spiral mitochondria, axoneme
Tail (flagellum)

Question 11

What are the 2 cells in seminiferous tubules called?

Answer 11

Sertoli cells - required for maturation of spermatozoa
- form 10% of cells in testes
- necessary for spermatogenesis 
- support and nourishment 
- more developing sperm towards lumen
- produce fluid for transport
- forms blood-testes barrier
- prevents immune response
- secrete testicular fluid:
> inhibin 
> androgen-binding protein
> Mullerian-inhibiting substance
Leydig cells - secrete androgenic steroids near capillaries

Question 12

How does the endocrine system control the male reproductive system?

Answer 12

1. release of GnRH from anterior pituitary gland
2. Stimulates release of FSH and LH
3. FSH travels to the seminiferous tubules and sustentacular cells, which cause the secretion of inhibin, synthesis of androgen-binding protein and stimulation of spermatogenesis
4. LH travels to the interstitial cells, causing the secretion of testosterone, causing the stimulation of sustentacular cells to release inhibin, ABP and spermatogenesis
5. the release of testosterone also has affects on the CNS, causes stimulation of bone and muscle growth, establishes and maintains male secondary sex characteristics, and maintenance of accessory glands and organs

Question 13

What happens if sperm count is too high?

Answer 13

Inhibin release is increased, negative feedback on FSH and GnRH by hypothalamus

Question 14

What happens if sperm count is decreased below 20 million?

Answer 14

Inhibin release is decreased

Question 15

Temperature control of testes

Answer 15

Testes kept just below body temperature at 35c
Testes are drawn closer to the body by the cremaster muscle in response to cold
Dartos muscle decreases SA and assists cremaster
Testes cooled by heat exchange at pampiniform plexus

Question 16

Describe the duct system

Answer 16

Straight seminiferous tubules
Rete testis 
Efferent ductules
Epididymal duct
Vas deferens
Ejaculatory duct
Urethra

Question 17

Epididymis

Answer 17

Attached to posterior surface of testes
Spermatozoa are matured and stored in the tail
Continuous with bas deferens

Question 18

Vas deferens

Answer 18

45cm long fibromuscular tube-
narrow lumen surrounded by thick smooth muscle layer
Ascends posterior to testis along spermatic chord
Enters abdominal cavity through inguinal canal
Dilated terminal portion (ampulla) joins the ejaculatory duct
Stores and conveys spermatozoa (expelled by peristalsis)
VASECTOMY = sperm still produced but deteriorates and are phagocytosed, success of reversal depends on patient eg age

Question 19

What are the accessory glands and what do they do

Answer 19

Seminal vesicles
Prostate gland
Bulbourethral gland
These glands produce the majority of semen (sperm + accessory gland secretions)

Question 20

Seminal vesicles

Answer 20

Convoluted muscular glands 5-7cm long
Posterior to bladder
Joins vas deferens to form ejaculatory duct when sperm and seminal fluid mix
Yellowish viscous alkaline fluid containing fructose, ascorbic acid, prostaglandins, coagulating enzymes
- 60% semen volume

Question 21

Prostate gland

Answer 21

Lies inferior to bladder
Surrounds prostatic urethra
Milky, slightly acid fluid containing citrate and enzymes, and prostate-specific antigen
Role in activating sperm
- 30% semen volume
Has tubular-alveolar glands
Main prostatic glands in outermost ring

Question 22

Problems with prostate gland

Answer 22

Often enlarged in older males: benign prostatic hyperplasia
- lower urinary tract symptoms:
- increased frequency, nocturia, weak stream
Treatment:
- alpha adrenergic blockers eg. tamsulosin - reduce smooth muscle tone
- 5-alpha reductase inhibitors eg. finasteride - blocks conversion of testosterone to dihydrotesterone
Prostatitis:
- acute or chronic
- pain when urinating and ejaculating, general discomfort in pelvic area
Treatment:
- acute = antibiotics and painkillers
- chronic = antibiotics, analgesics

Question 23

Prostate cancer

Answer 23

To do with levels of prostate-specific antigen

• during coughing and sneezing prostatic blood may enter vertebral veins
• lower vertebral and pelvic metastases

Question 24

Bulbourethral glands

Answer 24

Pea-sized glands inferior to the prostate gland
Lined by mucus-secreting epithelium
Mucus-like secretion enters urethra during sexual arousal
Drains into spongy part of urethra
Neutralised urine residue

Question 25

Urethra

Answer 25

Common path for urine and semen
Approx. 20cm long in males
> Prostatic part
> Membranous part: passes through urogenital diaphragm
> spongy part: passes through penis

Question 26

Penis

Answer 26

Divided into 3 regions:

• root: bulb in midline attached to inferior surface of urogenital membrane (become corporus spongiosum), crura attach the root of penis to pubic arch (becomes corpora cavernosa)
• shaft (body): spongy urethra + 3 cylindrical bodies of erectile tissues - corpora cavernosa (paired) and corporus spongiosum, dense network of connective tissue, smooth muscle and blood vessels, bound by tunica albuginea
• glans penis: tip of corporus spongiosum expanded to form glans penis

Question 27

Histology of the penis

Answer 27

Vascular spaces in erectile tissue
Lined with endothelium
Spongy urethra lined with pseudo-stratified columnar epithelium

Question 28

Erection

Answer 28

1. Arteries dilate (parasympathetic impulses: endothelial cells produce nitric oxide and relax smooth muscles)
2. Corpora cavernosa and corpus spongiosum become distended
3. Compression of veins reduces outward blood flow

Question 29

Emission and ejaculation

Answer 29

Sympathetic control

1. Contraction in smooth muscles of epididymal duct, vas deferens, prostate and seminal vesicles
2. Bladder sphincter muscle constricts
3. Emission: the release of a small volume of seminal fluid before ejaculation
4. Ejaculation: contraction of bulbospongiousus muscle

Question 30

Describe the functions and constituents of semen

Answer 30

2-5ml per ejaculation
Functions:
- transport medium
- nutrient provision
- has chemicals which protect and activate the sperm
Constituents:
- 20-150 million sperm per ml
- seminal fluid (secretions of seminal vesicles, prostate and bulbourethral glands)
> fructose, prostaglandins, relaxin, enzymes, seminal plasmin, fibrinogen, fibrinolysin

Question 31

What is oligospermia?

Answer 31

Less than 15 million sperm per ml = conception may be difficult

Question 32

If man has inability to ejaculate, low sperm count, poor motility etc what can he do to increase chances of pregnancy?

Answer 32

• intracytoplasmic sperm injection
• intrauterine insemination
• donor insemination
• gamete intra-fallopian transfer