Spermatogenesis and semen evaluation Flashcards
Describe the order of cells produced in spermatogenesis
Stem cells Spermatogonia Primary spermatocytes Secondary spermatocytes Spermatids Spermatozoa
What are the 3 aims of spermatogenesis?
Create genetic diversity
Produce spermatozoa capable of fertilisation
Replenish supply of primordial stem cells
What are the 3 phases of spermatogenesis?
Spermatocytogenesis (proliferation)
Spermatidogenesis (meiotic phase)
Spermiogenesis (differentiation)
What is the 1st phase of spermatogenesis and what happens?
Spermatocytogenesis - formation of primary spermatocytes from spermatogonia
What is the 2nd phase of spermatogenesis and what happens?
Spermatidogenesis - formation of spermatids from primary spermatocytes
(Create genetic diversity)
What is the 3rd phase of spermatogenesis and what happens?
Spermiogenesis - forming spherical shaped spermatids with enzymes and DNA
What is the blood testis barrier? What is its purpose?
Physical barrier between blood vessels and seminiferous tubules
Prevent sperm entering blood stream
What does the sperm-testis barrier do? Which stage of germ cells does it separate?
Separate basal and adlumenal compartments of seminiferous tubules
Separates spermatogonia and spermatocytes
What is the function of Leydig cells and Sertoli cells?
Leydig cells produce testosterone
Sertoli cells aid spermatogenesis
Which germ cell in the testes has the longest lifespan?
Primary spermatocyte
Are spermatids diploid or haploid? Are they genetically unique or identical?
Haploid
Genetically unique
What is the spermatogenic wave?
The differences at any given time across the seminiferous tubule
Each section of tubule contains different stage of sperm development
How long does spermatogenesis roughly take?
1-2 months
depending on species
Briefly describe the endocrinology leading to the production of FSH and LH
Hypothalamus produces GnRH
GnRH travels in blood to anterior pituitary
GnRH stimulates anterior pituitary gland to produce FSH and LH
Spermatazoa are produced in the testes. How long does it take for them to pass through the epididymis?
What happens to them throughout the epididymis?
1-2 weeks
Mature and develop motility in head and body of epididymis
Stored in the tail
The tail of the epididymis stores enough spermatozoa for multiple ejaculations. Does copulation frequency impact on time taken for spermatogenesis?
No
Increased copulation decreases spermatozoa density
Describe the structure of the head of a spermatozoa
Head has nucleus
Acrosome
Post nuclear cap
Varies between species
What does the acrosome contain?
Hydrolytic enzymes to penetrate zona pellucida
The tail is a self powered flagellum. What 3 pieces does it consist of?
Principle piece
Middle piece
Terminal piece
What is semen?
Fluid released at ejaculation
What are the 3 seminal fractions and describe their consistency?
Pre-spermatazoal fraction = watery
Spermatozoa rich fraction = creamy
Post-spermatozoal fraction = gelatinous
What contaminants may be found in a sperm sample?
Blood Bacteria Pus Urine Dirt
What should be evaluated when looking at a semen sample? How are they scored?
Volume Colour Appearance Live:dead ratio Mass motility/wave motion 1-5
What is the difference between an electroejaculation sample and a natural insemination sample?
EEJ sample are more dilute as more accessory gland secretion
What should mass/motility wave motion of semen resemble?
Clouds
A live:dead ratio can be calculated from a semen sample. Spermatozoa are very sensitive to timing, handling and staining. What can damage them?
Cold temperatures - keep all collecting equipment warm
Water
Bright light
Etc
What instrument is used to calculate spermatozoa density?
Haemocytometer
How can sperm defects be categorised?
Primary or secondary
Compensable or non-compensable
Head or tail
Give some examples of spermatozoa head abnormalities
Crater defect (vacuoles)
Tapered heads
Ruffled/knobbed acrosome
Give some examples of spermatozoa tail abnormalities?
Coiled/folded tail
Detached tail
Double midpiece
