Behaviour & Structure of Spermatozoa

1. Course: Andrology and Male infertility
Lecture-2: Sexual Behaviour and Structure of spermatozoa
Dr. Farooz Ahmad Lone (Ph.D Gold Medalist)
Assistant Professor
Animal Reproduction

2. Sexual Behaviour
• The flehmen reaction is found in all domestic animals
except swine.
• Erection is predominantly under the influence of
parasympathetic system and ejaculation is controlled
by the sympathetic system.
• Testosterone in male is aromatized to estradiol in the
brain. This estradiol promotes reproductive behaviour in
male.

3. Structure of Spermatozoa
• Semen=seminal plasma + sperm
• Shape of spermatozoa
Bull, Ram, Buck, Dog, Boar: Oval, flattened /Spatulate
Buffalo: Rectangular
Rodents (Rat): Falciform (Sickle or hook)
Cock: Filiform (Thread, Pencil, filamentous
or cylindrical)
• Size
• Bull sperm……….60-74µm
• Stallion sperm………..61–86 μm
• Human sperm……….57 μm

4. • Head is divided into two segments
-The anterior acrosome
- The post acrosomal region
The junction between these two
regions is called as nuclear ring or
equatorial segment.
Posterior ring demarcates the
junction between the head and tail.
-is the site of plasma membrane
anchoring into the nuclear envelope
- produces a tight seal

5. Acrosome
• Double layered membranous sac overlying the 60% of sperm
nucleus, located between the plasma membrane and the
nucleus.
• Developed from Golgi apparatus………specialized lysosome
• Composed of outer and inner acrosomal membrane containing
a protease filled matrix
• Enzymes
-Hyaluronidase (dispersal or digestion of cummulus
oophorous extracellular matrix)
-CPE (penetration of corona radiate)
- Acrosin (trypsin like, located on inner membrane, helps
in penetration through the zona pellucida
- Neuraminidase (enhances passage through the ZP)

7. Nucleus
• Largest component of sperm head
• Contains highly condensed DNA (protamines)
• Condensed DNA state ……………..non-dividing and
transcriptionally inactive
• Compacted DNA occupies small volume….billions of
sperm within narrow lumen of epididymal duct stacked like
coins

9. Sperm DNA
protamine
Toroid (doughnut loop, 50-100kb of
DNA)
high levels of arginine and cysteine
within protamine (disulfide cross links
between protamine cysteine residues)
toroids are stable and compact
structures, attached to nucleomatrix by
toroid linker region- susceptible to
DNases
folded histone solenoid punctate the
toroid chromatin structure (1-14%
histone retention)

10. Q. No. 6: Which of the following acts as a motor of sperm?
• Outer dense fibres
• Principal piece
• Axoneme
• Midpiece

11. 1. Axoneme (Motility apparatus or Motor of the sperm)
• The centrally located axoneme is composed
• 9 microtubule doublets + a central pair of singlet
microtubules (9+2 configuration)
• Extend throughout the length of tail

12. • Microtubules are made up of tubulin protein (Maximum)
• Dynein arms contain dynein protein
2. Outer dense fibres (ODF)
• Remarkable cytoskeletal structure, consisting of nine fibres
that surround the axoneme.
• These extend through the neck, midpiece and PP
• Provide structural support and passive elasticity during
flagellar bending.
3. Mitochondrial sheath
• Mitochondria arranged helically surround the ODF in the
midpiece only
• No. of mitochondria in a mature bull sperm are 50-75.
4. Fibrous sheath
• it surrounds the ODF in PP only.

13. • The Principal piece is the largest part, extend from annulus to the
end piece.
• The mid-piece has the largest diameter.
• The end piece contains only terminal portion of axoneme surrounded
by cell membrane