Sperm and Fertility L17 Flashcards
What are the 2x main classes of cells inside seminiferous tubules?
- Spermatogenic cells
-which are the precursor cells to sperm cells -are different sizes - Sertoli Cells
-support spermatogenesis
-run longitudinally around cells
Seminiferous Tubules look different closer to the lumen, due to being mainly the tails of sperm
What sort of barrier is within the seminiferous tubules?
Blood-Testis barrier
-Tight junction
Hols sertoli cells together
Where does spermatogenesis occur?
In the seminiferous tubules of the testes in male gonads
- each testical is about 20g
- therefore each male has 40g of testis tissue
What is the average amount of testicular tissue per male?
Each testical is about 20g
therefore each male has 40g of testis tissue
What is the difference between the timing of Spermatogenesis and Oogenesis?
Oogenesis occurs 6 months prior to gestation
Spermatogenesis begins at the initiation of puberty
When does oogenesis occur?
6 months prior to gestation
When does Spermatogenesis occur?
Begins at puberty
Constant production of sperm
What is the rate of sperm production in a mature male?
300-600 sperm, per gram of testis tissue, per second
20 million sperm per second per male
What are the shapes of the products within the process of spermatogenesis?
Earlier steps are all round
Products become progressively smaller
Final mature sperm/spermatozoa form mature elongated, hydrodynamic cells which are capable of movmement
How many days does spermatogenesis take altogether?
65-75 days
What are the 3x phases of spermatogenesis?
- Mitotic division - basal compartment
- Meiotic division I and II - adluminal compartment
- Cytodifferentiation /spermiogenesis
What is spermiogenesis?
cytodifferentiation
What are the 3x compartments of the seminiferous tubule?
- Basal
- Adluminal
- Lumen
What are the 5x classes of sperm during spermatogenesis, in order?
1. Spermatogonium/Spermatogonial step cells spermatogonia 2. Primary spermatocytes 3. Secondary spermatocytes 4. Spermatid 5. Mature Sperm/Spermatozoa
How many chromosomes do spermatogonium have?
diploid
46 chromosomes
What is the first think that happens at spermatogenesis?
At puberty, the Primary germ cells are Re-activated to become sperm stem cells
in response to brain signals
What sort of division is mitosis?
Asymmetrical division
1st division produces two identical daughter cells.
1x of the daughter cells remains undifferentiated and remains behind in the basal compartment to maintain the stem cell population in the basal compartment (spermatogenesis continues)
1x the other daughter cell produced continues to undergo mitotic divisions
about 7 more mitotic divisions, get progressively smaller. with a cytoplasmic chain between them
Spermatogonia are held together as daughter cells in a cytoplasmic chain - about 6x daughter spermatogonia cells in a chain (forms a series of 256cells)
Where does mitosis occur?
Basal compartment of the seminiferous tubules
How many chromosomes do primary spermatocyte have?
diploid
46 chromosomes
How do spermatogonia/um become spermatocytes?
when the Mitotic division are complete, the spermatogonia move form the basal compartment –> SQUEEZE BETWEEN the adjacent sertoli cells –> into now what is called the Adluminal part of the seminiferous tubules
this physical movement to/transition from the basal compartment –> physically into the adluminal compartment which is what cause spermatogonia to be called spermatocytes
What are the 6x key features of Sertoli cells?
- Support, develop and protect developing spermatogenic cells
- Nourish spermatocytes, spermatids and sperm
- Phagocytose excess spermatid cytoplasm as the development proceeds
- Controls the movement of spermatogenic cells and release in the lumen (adluminal –> lumen)
- Forms the barrier and separates the impermeable basal compartment and adluminal compartment
- Held together by tight junctions (blood testis barrier) - which the 1 primary spermatocytes squeeze through
What occurs to primary spermatocytes?
Primary spermatocytes undergo Meiosis 1 in the adluminal compartment
Meiosis 1 = DNA content doubles (increases)
-homologous pairs line up, crossing over, at the metaphase plate
-23 chromosomes, each with 2 chromatids
-forms Secondary spermatocytes (23 chromosomes each with 2 chromatids)
Undergoes a reduction division 2n –> n, as the spindle pulls chromatids to the opposite poles
- yields 2x secondary spermatocytes form each 1 primary spermatocytes
How many chromosomes do secondary spermatocyte have?
haploid n
23 chromosomes - 2x chromatids which are still attached at the centromere
What occurs to secondary spermatocytes?
Secondary spermatocytes undergo no more replication
there are 2x secondary spermatocytes
Very short phase- therefore is hard to see any 2 secondary spermatocytes
Chromosomes line up in a single file line along the metaphase plate, and then the 2x chromatids separate
overall, results in 4x haploid cells (4x n) which altogether are called spermatids
Which process in spermatogenesis is fast?
2 Secondary spermatocytes
Very short phase - therefore is hard spotting 2 secondary spermatocytes
How many chromosomes do spermatids have?
haploid n
23 chromosomes
(4x spermatids per meiosis II division)
What occurs to spermatids?
Spermatids still have a round morphology ( yet smaller than precursors)
Spermatids undergo spermIOgenesis/Cytodifferentiation
Spermatogenesis is the final stage of spermatogenesis, and involves the differentiation of sperm from round cells into long elongated hydrodynamically adapted spermatoZOA cells - via shedding excess cytoplasm
(round cells aren’t hydrodynamically adapted to move through a female reproductive tract, therefore they need to differentiation into a mature spermatozoa to be able to fulfil its function when long, slender and hydrodynamically adapted)
Note:
Early spermatid= just after Meiosis 1
Late spermatid= undergoes differentiation
The excess cytoplasm (containing protein,s, ribosomes, aa and fats etc which is excess for the job of the sperm but shouldn’t be wasted by the Testes) is shed off the spermatid, into a structure called the residual body
Sperm then move into the luminal compartment of the seminiferous tubules
When does differentiation to a spermatogonial cell occur?
occurs to spermatids
during Spermiogenesis/Cytodifferentiation (hence the name)
via shedding excess cytoplasm and forming separate residual body
How many chromosomes do spermatozoa have?
mature sperm
haploid n
23 chromosomes
How many chromosomes do mature sperm have?
mature sperm
haploid n
23 chromosomes
What occurs to spermatozoa / mature sperm?
Sperm move from the adluminal compartment to the luminal compartment
Spermatozoa are hydrodynamically adapted now to swim the 15cm (human equiv. 16km) female reproductive tract to fertilise an egg
Their tails are projected inwards (towards the lumen) after they are shed from sertoli cells
Loses connection with the seminiferous tubules
The residual body is phagocytosed by sertoli cells AFTER the sperm leaves the adluminal compartment
Sperm that enter the lumen of seminiferous tubule still cannot swim, therefore fluid is secreted by sertoli cells, which pushes the sperm to the ducts of the testes, before they begin 10 day maturation in the epididymis
When do spermatogonial cells lose connection with the seminiferous tubules?
as mature sperm/spermatozoa
What occurs in the basal compartment?
Mitosis
What occurs in the adluminal compartment?
Meiosis I and Meiosis II and beginning of cytodifferentation
What occurs in the basal compartment?
the end of cytidufferentiation
What phagocytoses the residual bodies of spermatids?
Sertoli cells
Sertoli cells phagocytose the residual bodies shed off spermatids AFTER the sperm leave the adluminal compartment
avoids the proteins, ribosomes, aa’s, fats from the residual body being wasted by the seminiferous tubules
Can sperm swim when they enter the Luminal compartment?
No
Sperm cannot swim yet( have the potential too but not physically able to yet)
Sertoli cells secrete fluid to Push the sperm towards the ducts of the testes
before the sperm begin maturation in the epididymis
What are the residual bodies?
No DNA
Only excess cytoplasm
buds/is shed off spermatids
as a mature sperm/spermatozoa want to be effective at it’s ob of swimming 15 cm (equiv human 16km swim) up the uterus/to the top of the fallopian tube to fertilise and egg
therefore they need to be hydrodynamically adapted, and Doesn’t need the proteins, ribosomes, aa, fats etc in the cytoplasm to complete its job - aren’t essential
There residual bodies are Phagocytosed by SErtoli cells AFTER the spermatozoa/mate sperm are in the luminal compartment out of the adluminal compartment
What are the 7x key features of a sperm?
- Total sperm length = 60 microns
- Acrosome: a cap-like vesicle or compartment filled with enzymes such as hyaluronidase, which is required in order to penetrate the eggs hard shell of the zona pellucida through too the 2 secondary oocyte itself during fertilisation - red in histology slide
- if no red acrosome, shows it is a sperm with an already reacted acrosome, therefore can no longer penetrate the zona pellucida, and is a major cause of infertility - Nucleus: contains DNA. Is at Top so it is the key initial piece to enter the egg
- blue in histology slide - Mid-piece: Engine room. contains mitochondria for energy “powerhouse”/engine to drive flagella’s movement. -designed to allowing swimming movement to occur
- red in histology slide - Tail/Flagella Principle piece: Longest part of the tail. is important for the Locamotion and Propulsion of the sperm through the vaginal tract and uterus.
- Tail/Flagella End-piece: last part of the flagella. thinner
- Histology slide: Red: acrosome and midpiece. Blue: DNA in nucleus
What is the total length of a sperm?
60 um micometres
What enzyme is required to be in the sperm’s acrosome in order to penetrate through the eggs hard shell of the zona pellucida to the 2 secondary oocyte during fertilisation?
Hyaluronidase
What is the purpose of a sperm?
To fertilise an egg
travel the 15 cm swim (human equiv. 16km swim) through the vaginal tract, uterus and fallopian tube to penetrate and fertilise an egg
What are the 5x compulsory components of a sperm?
- Acrosome
- Nucleus
- Midpiece
- Tail/Flagella Principle piece
- Tail/Flagella Endpiece
What is the function of the Acrosome component of a sperm?
a cap-like vesicle or compartment filled with enzymes such as hyaluronidase, which is required in order to penetrate the eggs hard shell of the zona pellucida through too the 2 secondary oocyte itself during fertilisation - red in histology slide
-if no red acrosome, shows it is a sperm with an already reacted acrosome, therefore can no longer penetrate the zona pellucida, and is a major cause of infertility
What happens if on a histology slide there is no acrosome?
if no red acrosome on the top of the sperm (no cap like structure), shows it is a sperm with an already reacted acrosome, therefore can no longer penetrate the zona pellucida, and is a major cause of infertility
What is the function of the Nucleus component of a sperm?
contains DNA. Is at Top so it is the key initial piece to enter the egg
-blue in histology slide
What is the function of the Midpiece component of a sperm?
Engine room. contains mitochondria for energy “powerhouse”/engine to drive flagella’s movement. -designed to allowing swimming movement to occur
-red in histology slide
What is the function of the Tail/Flagella Principle piece component of a sperm?
Longest part of the tail. is important for the Locamotion and Propulsion of the sperm through the vaginal tract and uterus.
What is the function of the Tail/Flagella Endpiece component of a sperm?
last part of the flagella. thinner
What is the normal male sperm count?
20 million sperm per mL
-anything number of sperm less per mil is considered infertile
What are the 3x main types of male infertility?
OLI GOes to the ZOO
- OLIGOspermia:
- Low sperm volume/count (less than 20 million sperm per mL) –> IVF - AZOOspermia:
- NO sperm at all in the ejaculate —biposy—> ICSI - Immotile sperm:
- sperm CANNOT SWIM –direct injection–> ICSI
What is Oligospermia?
When there is a low sperm volume/count
(i.e. the number of sperm per ml is less than 20 million sperm mL-1)
example of infertility in males
IVF
What is Azoospermia?
When there is NO SPERM AT ALL in the ejaculate
(therefore definitely below the 20million sperm per mL count)
Example of infertility in males
1. Biopsy (as sperm doesn’t need to be directly located in ejaculate) to collect sperm in testes tissue –> ICSI (intra-cytoplasmic sperm injection)
What are immotile sperm?
When the sperm CANNOT SWIM
example of infertility in males
1. Direct injection of sperm through zone pellucida into secondary oocyte via ICSI
What are the 2x methods of overcoming male infertility?
- IVF
2. ICSI
What is IVF?
In-Vitro Fertilisation
1. Oocytes are harvested
2. Oocytes are fertilised ex vivo
3. Requires approximately 50,000 sperm which are all MOTILE
(requires 50,000 sperm therefore isn’t a solution for patients with Azoospermia) (requires motile sperm therefore isn’t a solution for patients with immotile sperm)
4. Goes into MEDIA DROPLETS, per oocyte
-5 Microlitres of aqueous media droplets + under oil as to avoid dehydration
What are the requirements of IVF?
50,000 sperm (therefore not a solution for Azoospermia (no sperm) infertile type patients)
all 50,000 sperm must be MOTILE (therefore not a solution for infertile immotile sperm type patients)
What is ICSI?
Intra-Cytoplasmic Sperm Injection
solution to all male infertilities
1. a SINGLE sperm is captured and injected DIRECTLY INTO the oocyte, via use of a Holding pipette and Injecting pipette
2. -Egg is placed and maintained under a microscope
-Sperm DOESNT have to be from ejaculate, can be located elsewhere in testes tissue
only a SINGLE sperm required therefore is a solution for Azoospermia, as patient can undergo BIOPSY in his TESTES as sperm can be SOURCED ELSEWHERE THAN EJACULATE
- sperm is INJECTED DIRECTLY INTO the oocyte through the zona pellucida and cytoplasm, directly into 2secondary oocyte to allow fertilisation, therefore is a perfect solution for males who are infertile with IMMOTILE SPERM , as sperm DEOSNT HAVE TO BE MOTILE for ICSI
What are the 2x overall roles of sex hormones in reproduction?
- down-regulating their own production via negative feedback
- spermatogenesis
What 3x hormones are involved in spermatogenesis control?
- GnRH
- LH
- FSH
What does GnRH do for spermatogenesis control?
GnRH are released/secreted from the hypothalamus in a Pulsatile fashion, from the hypothalamic neurosecretory cells, only AFTER puberty
GnRH travels Down the portal system, travels a short distance,
due to travelling down the portal system the contents of the blood are Not diluted by travelling around the body
it Stimulates Gonadotrophs in the anterior pituitary to secrete gonadotrophens LH and FSH
Both LH and FSH now travel via the peripheral blood stream
GnRH Secretion is suppressed (-ve feedback) by Testosterone (alongside LH -ve feedback by testosterone levels)
What does the hypophyseal portal system avoid dilution of?
GnRH from hypothalamus
portal system located in infundibulum
Avoids GnRH from getting diluted so the contents of the blood aren’t diluted by travelling around the body before going to the anterior pituitary
What does LH do for spermatogenesis control?
LH travels via the peripheral blood stream
Stimulates Leydig cells via binding to their LH surface receptor
Leydig cells are OUTSIDE of the seminiferous tubules. is located in the INTERSTITIAL CELLS of the Testes
Leydig cells are involved in the synthesis of Testosterone
Testosterone = Lipid soluble therefore readily diffuses from Leydig cells –through LBL –> Interstitial fluid –through LBL–> blood
Via testosterone’s presence 2x negative feedbacks occur:
1. suppresses the secretion of LH by the anterior pituitary’s gonadotrophs
2. suppresses secretion of GnRH by the hypothalamic neurosecretory cells
Where are LEydig cells located?
Outside of the seminiferous tubules
Located in the Interstitial cells of the Testes
Waht are Leydig cells involved in?
Synthesis of Testosterone
What is the benefit of Testosterone being Lipid Soluble?
Readily diffuses through:
Leydig cells —LBL–> Interstitial Fluid –LBL–> Blood
What do increased levels of Testosterone do?
Stimulated to be produced by LH binding onto LEydig cell’s Lh surface receptor
2x Negative feedback caused by elevated levels of LH:
1. suppresses the secretion of LH by the anterior pituitary’s gonadotrophs
2. suppresses secretion of GnRH by the hypothalamic neurosecretory cells
What is the function of testosterone?
- OUT in some target cells active metabolise testosterone (prostate, external granules)
- Regulation of 2 secondary characteristics (therefore initiation of puberty)
What does FSH do for spermatogenesis control?
FSH travels vie the peripheral blood stream
FSH combined with testosterone act on Sertoli cells, by binding to FSH receptors in the surface of sertoli cells
Sertoli cells are found inside the seminiferous tubule and are in Direct Contact with Spermatogonia(2)
FSH causes sertoli cells to produce ABP (Androgen Binding Protein) into the lumen of Seminiferous tubule, into interstitial cells around the spermatogenic cell
-androgens such as testosterone bind to ABP so their water-insoluble bodies can be transported throughout the blood
-This builds a reservoir of androgens inside the seminiferous tubule, allowing spermatogenesis to continue occurring
ABPs are Nescessary for spermatogenesis
FSH indirectly stimulates spermatogenesis
Maintains concentration of testosterone/androgen in the seminiferous tubule –> locks the testosterone inside the tubule
via negative feedback, sertoli cells produce protein hormone Inhibin, which inhibits FSH secretion be the anterior pituitary’s gonadotrophs
Where are Sertoli cells located?
Inside the adluminal compartment if seminiferous tubules
Sertoli cells are in direct Contact with Spermatogonia(2)
What sort of hormone is Inhibin?
Protein hormone
What causes Inhibin to arise?
sertoli cells secrete inhibin
What does activation of sertoli cells do?
Sertoli cells produce the Protein Hormone Inhibin
Inhibin has a negative feedback effect on FSH secretion by the anterior pituitary’s gonadotrophs
What is the role of Kisspeptin?
Onset of GnRH production at puberty
Above GnRH neurons in hypothalamus are neurons which produce another neuropeptide called kisspeptin
Cause GnRH neurons to produce GnRH
Small peptide hormone/neurotransmitter regulates -production of GnRH and onset of puberty
What are the 2x roles of Kisspeptin?
- Production of GnRH
2. Onset of Puberty
