Sperm (wk 1) Flashcards
Where does vas deferens travel through?
inguinal canal
What is the panpinform plexus? Where is it?
Surrounds vas deferens
Vessels that are supplying the testis
It cools the blood that is travelling to the testis= temperature control
What is tunica albuginea?
White fibrous coat surrounding the testis
Has invaginations that form segments within the testis
What is found within the segments of the testis?
seminiferous tubules
They produce sperm
They drain into the rete testis
Where does the rete testis drain into?
Efferent ducts
What is tunica vaginalis?
fibrous muscular covering
What are the four major compartments of the seminiferous tubule? Which compartments make up the stroma?
Vascular and interstitial make up the stroma
Basal
Adluminal
What are the two main functions of the testis?
Formation of spermatozoa in the seminiferous tubules (basal and adluminal region)
Hormone synthesis in the extra tubular stroma (leydig cells produce testosterone)
What is the role of myoid cells?
In the stroma
Surround each seminiferous tubule
Contractile cells
Provide peristaltic action to the sem tubules
Where can you find sertoli cells and what is their role?
Above the basement membrane
Ensure the proper development of sperm/germ cells by taking in messages from the CNS and translating it to the developing sperm
Explain the blood testis barrier
Tight junctions between neighbouring sertoli cells
Prevents immune response against gametes (these are haploid)
Regulates microenvironment for gamete development
What is the main reason for sexual reproduction and how is this achieved?
Allows for competitive advantage in a variable region
Mixing of genomes, genetic recombination, diploidy
What are the three stages of spermatogenesis?
Spermatocytogenesis (mitotic proliferation) Meiotic division (genetic reduction) Spermiogenesis (germ cell remodelling)
How many rounds of mitosis must the cell go through before it enters meiosis?
6 rounds of mitosis
Primary Spermatocytes enter meiosis
What is the difference between type A and type B?
A: stem cell production, early stages of sperm development
B: have gone through at least one round of cell division
What mechanism allows for gene mixing during meiosis?
Homologous recombination
What occurs in spermiogenesis?
Stage 3 formation of the acrosome development of the flagellum chromatic condensation and nuclear remodelling loss of cytoplasm
What are the stages of spermiogenesis?
Golgi phase:
- Centriole and golgi move closer together
- Form the annulus
- Alixal filament grows out from the most posterior centriole (will form the flagellum)
- Golgi secretes factors for the acrosome vesicle
Acrosomal phase:
- Golgi fills the acrosomal vesicle with enzymes e.g. hydrolytic enzymes
- Centrioles migrate down away from the acrosomal vacuole= start to get polarity
Cap phase:
- Spermatid attaches to sertoli cell
- Get the acrosomal cap: acrosome extends over the nucleus
- Centrioles are all at the posterior end and migrate to the base of the nucleus
- The cytoplasmic cannal forms due to some invagination
Maturation phase:
- Nuclear condensation (protamines replace histones)
- Manchette (circular band of microtubules) shapes the head
- Suppression of transcription
- Sheath forms over the prinicpal piece of the tail
- Mitochondria start to arrange around the most proximal part of the flagellum to form the mid piece
- Annulus migrates posteriorly
- Mitochondria arrange around the axonemal core
- Sertoli cells remove unwanted cytoplasm
Mature Sperm
- Sertoli cells form residual bodies (left over cytoplasm)
- Spermiation= release from seminferous tubules
Explain how the tail allows for movement
2 single microtubules sit in the centre surrounded by 9 pairs of microtubule doublets
The dynein arms grab onto adjacent microtubule doublets to bring them close together, this results in some bending, some release their grip and others will bind on, get progressive bending in the tail which allows for motility
What are the four main types of cells in the epididymus?
Principal
Narrow (regulate pH)
Basal (detoxification)
Halo (phagocytose)
Where are the efferent ducts and vas deferens in relation to the epididymus
Efferent ducts enter the initial segment
Vas deferens begins at the cauda
What is the role of the blood epididymus barrier?
Prevents autoimmune response
Creates a controlled luminal fluid environment
What are the two main roles of the epididymus?
Fluid absorption in the proximal region
Sperm maturation
Sperm transfer
Sperm storage
Explain the two stages of sperm maturation in the epididymus
Forward progressive motility= gaining the ability to swim
- Almost all are mobile by the time you get to the cauda region
- Forward motility protein (from principal cells in epididymus)
- Sperm loses cytoplasmic droplet (halo cells phagocytose it when it drops off), allows more motile potential
Attainment of fertilizing ability
- epididymus secretes proteins to the sperm surface and modifies proteins on its surface
- Allows it to bind and penetrate the zona pellucida and the oocyte
Describe how sperm become active upon ejaculation
Liquefaction of sperm= PSA make the seminal fluid a better environment for the sperm to swim in
Capacitation= biochemical changes that occur in the female reproductive tract
- Get an influx of calcium ions into the sperm
- Causes erratic swimming which helps it to break through the barriers
Progesteron and ZP3 in activation/hyperactivation
Semen is slightly alkaline, vaginal environment is slightly acidic
Describe the barriers of the oocyte that the sperm has to break through
Cumulus oophorus first
Then zona pellucida –> acrosome reaction occurs
Explain hyperactivation
Sperm binds to ZP
Some calcium is released from intracellular stores
Calcium channels e.g. CatSper open to allow influx of extracellular calcium into the flagellum
Sperm becomes hyperactivated (irregular erratic beating of the flagellum)
Which protein does the principal cell secrete and when does this occur? What is the purpose of this protein?
Principal cell secretes the forward motility protein
Occurs in the forward progressive motility stage of sperm maturation in the epidiymus
allows them to become motile
What do halo cells phagocytose and when?
They phagocytose the cytoplasmic droplet in the forward progressive motility stage in sperm maturation in the epididymus
What are some examples of proteins that render the sperm immobile in the epididymus?
Clusterin and immobulin
