Spermatogenesis Flashcards
Where are sperm made and stored?
β In the testes
β stored in the epididymis
What contracts during ejaculation?
β The vas deferens
Where do the sperm travel to after the vas deferens?
β Seminal vesicle which contribute seminal fluid
β move to the prostate which also contribute secretions
Where does the vas deferens meet the urethra?
β In the prostatic gland
What is responsible for erections?
β Hydrostatic pressure
Where are the testes located?
β in the scrotum outside the body cavity
Why are the testes located outside the body?
β Optimum temperature for sperm production
β overheating reduces sperm count
What is the normal volume of the testes and how is this measured?
β 15-25ml
β orchidometer
What do the tubules lead to?
β Rete on one side
What does the rete lead to?
β Epididymis and vas deferens
What is 90% of the testis made up of?
β seminiferous tubules
Where is the site of spermatogenesis?
β Seminiferous tubules
How long does it take for sperm to go from the basal side to the lumen?
β 74 days
What are sertoli cells held together by?
β Tight junctions
What are tight junctions for?
β preventing an immune response against sperm cells
Describe the formation of spermatozoa
β The sperm start as spermatogonia which are diploid
β they replicate by mitosis and form 2 types of cell
β type A and type B
β type A is used as the template and replicates again
β type B moves into the adluminal compartment and becomes a primary spermatocyte
β the primary spermatocyte undergoes meiosis I and become secondary spermatocyted
β 2ndary spermatocytes divide to form 4 daughter cells (meiosis II)
β these are spermatids
What are the walls of the seminiferous tubules made from?
β Tall columnar endothelial cells which are Sertoli cells
What are spaces between the seminiferous tubules filled with?
β blood
β lymphatic vessels
β Leydig cells
How long does the cycle of spermatogenesis take?
β 74 days
How often do new cycles of spermatogenesis occur?
β every 16 days
Summarise spermatogenesis in 3 steps?
β mitotic proliferation of spermatogonia
β Meiosis and development of spermatocytes
β spermiogenesis , elongation, loss of cytoplasm and movement of cellular content
What do spermatids remain connected by and why?
β A cytoplasmic bridge
β they form a syncytium allowing synchronous development
What are the 2 differences between oogonia and spermatogonia?
β Cannot make more oocytes by mitosis
β sperm can divide mitotically
β limited supply of eggs
What do Leydig cells do?
β LH binds
β Convert cholesterol into testosterone
What receptors do Sertoli cells have?
β FSH
What is the function of Leydig and Sertoli cells?
β Leydig cells make testosterone
β Sertoli cells make ABP which makes testosterone more soluble so it can be concentrated in the lumen
What happens if you take anabolic steroids?
β Decrease in LH and FSH
β Testicular atrophy occurs
What happens during an erection?
β Vasodilation of the corpus cavernosum
β Partial constriction of the venous return
What does the autonomic nervous system do during an erection?
β Coordinated smooth muscle contraction of the vas deferens, glands and urethra
What does the parasympathetic system do during an erection?
β controls erections
What does the sympathetic system do during an erection?
β Controls the movment of sperm into the epididymis, vas deferens and penile urethra
What does the somatic nervous system do during an erection?
β Expulsion of glandular secretions and evacuation of the urethra
How many sperm are produced per day?
β 300 million
What is the normal ejaculate volume?
β 1.5-6mL
What does seminal fluid consist of?
β Secretions from seminal vesicles
β prostate
β bulbo-urethral gland and epidydimal fluid
What is is the function of the bulbo urethral gland?
β produces a clear viscous secretion high in salt
β pre-ejaculate
What is the function of pre-ejaculate?
β The fluid lubricates the urethra for the spermatozoa to pass through which neutralizes traces of acidic urine
What do seminal vesicle secretions contain?
β Proteins β enzymes β fructose β mucus β vitamin C β prostaglandins
What is the function of the seminal vesicle secretions?
β provide an energy source
β high pH protects again acidic environment in the vagina
What is the function of the prostate?
β Secretes white fluid roughly 30% of seminal fluid
What is the function of the prostatic secretions?
β High zinc concentration which is anti bacterial
β prostatic acid, phosphatase and prostate specific antigen which are involved in liquefaction
What should the normal morpholoy % be?
β more than 4% normal
What does a spermatozoaβs head contain?
β Acrosome
What is the acrosome reaction?
β THe head βexplodesβ and enzymes are released which make the sperm bury into the zona pellucida of the egg
What do sperm need to undergo for them to be functional?
β Capacitation
When does capacitation need to occur?
β 4-18 hours of being released
What is the mitochondrial sheath for?
β Swimming
What does the axoneme consist of and where is it ?
β 9 pairs of tubules with a pair down the center
β tail
