Spermatogenesis Flashcards
Where are sperm produced?
testes
Where does sperm get stored?
epididymis
What happens in ejaculation?
sperm moves out epididymis via vas deferens to enter prostatic urethra as ejaculatory duct
What is the ejaculatory duct?
area where vas deferens combine with seminal vesicle outflow
Where’s testosterone produced?
testes
Why do testes lie in a scrotum outside the body?
Optimum temperature for sperm production - 1.5 - 2.5 degree below body temperature
How spongy tissue in penis assists in ejaculation?
spongy, very vascular, engorges with blood to produce erection
suppresses urethra so urine can not flow well when there is an erection
Orchidometer
measure testes size
site of spermatogenesis?
seminiferous tubules
What is the rete testis?
An area where all the seminiferous tubules come together
What happens in the rete testis?
All the sperm concentrate in this area
Journey of a sperm
- Produced in seminiferous tubes in lobules
- Concentrated in rete testis
- Stored in epididymis from rete testis
- Leads to vas deferens
- Which links to prostate urethra
What are the walls of the seminiferous tubules made up of?
Sertoli cells
Describe the type of cell sertoli cells are
Tall, columnar endothelial cells
Female equivalent of sertoli cells?
granulosa cells
What’s on basement membrane, between sertoli cells?
Spermatogonia
What’s between the seminiferous tubules?
- Ledwig cells
- Interstitial fluid
- Blood and lymphatic vessels
Difference between cells closer to tubule + cells further away
Closer = more mature
Further = less mature.
Cells become more mature as they travel closer to tubules
Which cells undergo mitosis and why?
Spermatogonium (primordial germ cells) undergo mitosis to increase the number of spermatogonium
B-Spermatogonium
Differentiating progenitors which commit to meiosis - forming primary spermatocytes.
Where’s B-Spermatogonium?
Move towards seminiferous lumen, between sertoli cells.
Leydig cells
produce testosterone
Female equivalent of Leydig cells?
theca cells
How do the sertoli cells divide tubules?
- Interstitial space
- Luminal compartment - run through middle of cells
- Adluminal compartment - seperated by sertoli cells
Adluminal compartment
sertoli cells form tight junctions between each other keeping developing sperm in confined compartments in the walls of tubules
Why are tubules divided into different compartments?
keeps spermatogonia in specialised environment to pick up nourishment + secretions from sertoli cells
Blood-testis barrier
sertoli cells form between interstitial space + inside of tubule preventing immune system from invading or looking into testis
Why immune-related issues in vasectomy?
testis content can leak into circulation - immune bodies see sperm + produces antibodies against individual’s own sperm
A spermatogonia
germ cells - divides mitotically to replenish themselves forever
B spermatogonia
commit themselves to meiosis to produce spermatozoa
What are the changes that sperm undergo as they move towards the lumen?
- Meiosis occurs
- Become haploid
- Undergo morphological changes
Female gamete production
- Oogonia all laid down in foetus
- Oogonia undergo meiosis to become oocytes
- Oogonia can’t produce more oocytes by mitosis
- Limited supply of oocytes
Male gamete production
- Spermatogonia laid down in foetus
- Spermatogonia may either undergo meiosis to become spermatocytes OR undergo mitosis to replenish their supplies
- Limited supply of oocytes whilst lifetime supply of spermatogonia
stages of spermatogenesis
- Mitotic proliferation of spermatogonia
- Meiosis + development of spermatocytes (cell)
- Spermiogenesis - morphological changes of cell
What are the different types of spermatogonia?
3 different types:
- Ad - A dark
- Ap - A pale
- B
Morphological changes of maturing sperm?
- Elongation (tail)
- Loss of cytoplasm
- Movement of cellular content
Difference between HPG-Axis in males and females?
Females - cyclical - runs on a cycle
Males - Equilibriumone
FSH receptors
on Sertoli cells
convert testosterone into oestrogen via activation of Aromatase
No FSH?
sertoli cells die
No LH?
sertoli cells would not be able to maintain and regulate spermatogenesis
How are secondary sexual characteristics produced?
Androgens bind to “Androgen Binding Proteins” which get transported via circulation
Why do body builders who use steroids usually have low sperm count?
Steriods = include testosterone
Exogenous steroids = work on HPG-Axis to down regulate due to negative feedback.
Reduces LH/FSH release from pituitary leading to testicular atrophy = decreased sperm production
What is the corpus cavernosum?
Spongy tissue which is highly vascular.
What happens during an erection?
Blood flow to penis increases from dilation
Venous return restricted so penis is bloated
Which ANS component controls the erection?
Parasympathetic system - Point
Which ANS component controls movement of sperm in the epididymis, vas deferens and penile urethra?
(Emission)
Sympathetic system - Shoot
Which nervous component controls the expulsion of glandular secretions and evacuation of urethra?
(Ejaculation)
Somatic NS - Perineal branch of the pudendal nerve S2-S4
Which portion of the ejaculate is sperm rich?
The initial portion
Seminal fluid consists of secretions from:
- Seminal vesicles
- Prostate
- Bulbo-urethral gland
- Epididymal fluid
bulbo-urethral gland
produces pre-ejaculate: clear, viscous secretion high in salt
pre-ejaculate
- Lubricate urethra for spermatozoa to pass through at a high speed without damaging them
- Neutralise traces of acidic urine + getting rid of bacteria
What is seminal vesicle fluid made up of?
- Proteins
- Enzymes
- Fructose
- Mucus
- Vit C
- prostaglandins
What is the significance of fructose?
It is the energy source for sperm movement
What is the significance of prostaglandins?
It increases pH to help protect against acidic pH of vagina.
What does the prostate secrete?
A milky or white fluid
What is the prostatic fluid made up of?
<1% protein content:
- Including preoteolytoc enzymes
- Prostatic acid
- Phosphatase
- Prostate specific antigens which are involved in liquefaction
- High concentrations of Zinc
Why jelly-like ejaculate?
cascade - allows it to enter a single area + not leak out
What allows the sperm to get through the zona pellucida?
Has sac of acrosome at the tip - proteolytic enzymes which digest outer layer of egg
mitochondrial sheath
Machinery for energy production - fructose breakdown
Female equivalent of bulbo-urethral gland?
Bartholin’s
What is the significance of high zinc?
antibacterial
