Male reproductive Flashcards
How does spermatozoa cell size compare to other cells?
They are the smallest human cell with a 3 micrometer diameter
Longest cell relative to the organism.
What layer surrounds the testes?
Tough membranous shell called the tunica albuginea.
What is the name of the fine coiled tubules within the testes?
Seminiferous tubules
Where do developing sperm mature?
Epididymis
Where do sperm pass from seminiferous tubule to the vas deferens?
Seminiferous tubule - rete testis - efferent ducts - epididymis - vas deferens
Where do leydig cells lie?
Inbetween seminiferous tubules
What do leydig cells produce?
Testosterone
In the foetus what are the testis populated with
Spermatogonia
When does mitosis of spermatogonia begin?
In foetal life
When does spermatogenesis and meiosis beign?
At puberty
What is spermatogonium?
Diploid stem germ cell
What is spermatogonia?
Divided (mitosis) spermatogonium (still diploid)
What is the name of the primitive sperm that undergoes meiosis I?
Primary spermatocyte (diploid)
What does meiosis I produce?
Two haploid secondary spermatocytes
What is the name of the primitive sperm that undergoes meiosis II?
Secondary spermatocytes (haploid)
What does meiosis II produce?
4 round spermatids joined by cytoplasmic bridges.
What is the benefit of cytoplasmic bridges?
Cytoplasmic bridges lead to synchronisation between spermatids as they allow transfer of mRNA and proteins between haploid cells
What happens to spermatids?
Differentiate to form spermatozoa
Can all haploid cells fertilise?
Yes
Where do sertoli cells lie?
Inbetween sperm progenitors undergoing spermatogenesis
What is the role of the sertoli cell?
Support spermatogenesis through secretions and phagocytosis action
Forms the blood testis barrier
What does the sertoli cell secrete?
FSH
ABH (androgen binding hormone) - increases the concentration of testosterone at site of sperm development
Inhibin
What is the blood-testis barrier, and what forms it?
Very tight junctions between Sertoli cells separate the basal compartment from the luminal compartment.
What is the role of the blood-testis barrier
Protects sperm from the immune system
Controls the luminal environment for effective spermatogenesis
How is DNA packing different in sperm?
DNA packed more tightly in sperm than somatic nuclei.
Sperm: annulus repeat packed on protamines
How long does the process of spermatogenesis take?
60 days
How frequently do new cohorts of spermatogonia develop?
Every 12 days
How does spermatogeneis occur through the epithelium?
As a wave, so adjacent parts are at a different stage
What are the four final phases of spermatogenesis occuring at the top of the epithelium?
Elongation, Grouping, Maturation, Release
How do elongation, grouping, maturation and release appear on histology slides?
Release - no sperm present at edge of lumen of tubule
Grouping - clumpy appearance at lumen
Maturation - apparent sperm at lumen
What is spermiogenesis?
Spermatid maturation
What are the three phases of spermiogenesis?
Golgi phase
Cap phase
Acrosome phase
What happens in the golgi phase of spermiogenesis (4)?
Begin to develop polarity.
Head forms at one end, Golgi apparatus creates enzymes that will become the acrosome.
At the other end, a distal centriole begins to form an axoneme.
Spermatid DNA also undergoes packaging, becoming highly condensed.
What happens in the cap phase of spermiogenesis?
The Golgi apparatus surrounds the condensed nucleus, mitochondria migrate caudally.
Axoneme extends
What happens in the acrosome phase of spermiogenesis?
The acrosomal cap forms and mitochondria gather around the tail.
Axoneme central to the flagellum
What is the first trigger in puberty?
Hypothalamic kisspeptin neurons become activated
What does kisspeptin activate?
Kisspeptin activates pulsatile secretion of GnRH from GnRH neurons
What does GnRH activate?
Hypothalamic GnRH stimulates secretion of pituitary gonadotrophins FSH and LH
What does FSH stimulate in males?
Stimulates Sertoli cell division, then secretion of inhibin (negative feedback), secretion of ABP – androgen binding protein.
What does LH activate in males?
Acts on the Leydig cells to produce testosterone
Most active form = dihydrotestosterone made by 5-alpha reductase
Essential for sperm production
How is testosterone maintained in high concentrations?
Binding of testosterone by androgen binding protein present in the seminiferous tubules.
How long do sperm take to pass through the epididymis?
4-6 weeks
Is the epididymis a single tube?
Yes
Within the epididymis what is added to the sperm head and why?
Adds a glycoprotein coat over sperm head - prevents premature activation of acrosome
Does the vas deferens passively carry spermatozoa?
No, contractions propel it along
What three sex accessory glands produce seminal fluid?
Prostate, seminal vesicles and bulbourethal gland
How many sperm per ml of semen?
20 million
How much of seminal volume does each sex accessory gland make up?
2/3 -seminal vesicles
1/3 - prostate
a few drops - bulbourethral
What do sperm require for motility?
Fructose
When do spermatozoa begin to swim?
After leaving the epididymis
Lipid mediator hormone present in seminal fluid
Prostaglandin
A pituitary hormone that can cause infertility when levels are raised ?
Prolactin
What is one unique property of mature spermatozoa
They contain a modified lysosomal structure called the acrosome
What is the acrosome derived from?
Golgi
What is the acrosome
The acrosome is a large lysosome-like vesicle overlying the sperm nucleus.
Contains acrosomal enzymes and common enzymes associated with lysosomes in somatic cells.
Do spermatocytes arrest during either meiotic division?
No
What supplies the fructose?
Seminal vesicles/ Vas deferens
What cells line the epididymis?
Epididymis is covered by a two layered pseudostratified epithelium.
What receptors do epithelial cells of the epididymis have?
Testosterone receptors
In the basal compartment of the seminiferous tubules what do the cells undergo?
Repeated mitotic divisions
