2. Definition
• Spermatogenesis is a process of development of the male gametes/ sperm
within the male reproductive organs.
• This process occurs in the seminiferous tubules of the testes.
• It is followed by maturation of spermatids in the epididymis.
• This process begins during puberty and ends only when the individual
dies.
• The process of Spermatogenesis occurs to create mature male gametes,
which then fertilize female gametes to create a zygote, a single-celled
organism. For a healthy offspring, the number of chromosomes must be
maintained properly as failure can lead to genetic abnormalities.
3. Spermatogenesis
Greek words sperma (meaning “seed”) and genesis (meaning
“birth”, “origin”, “creation”)
The Sperm formulation involves three steps:
• Spermatocytogenesis : spermatogonia form
spermatids. spermatids are still rounded and large due to the
cytoplasmic structures that are still intact. They will go through
changes in their form so that they become adapted for
fertilization.
4. Contd…
• Spermiogenesis: spermatids which bulky and rounded undergo
morphological changes to become compacted and
streamlined spermatozoa. Spermiogenesis is comprised of four phases.
These phases are
• (1) Golgi phase,
• (2) Cap phase,
• (3) Tail phase, and
• (4) Maturation phase.
By the end of the last phase, the spermatozoon consists of three distinct
parts: the acrosomal head, mid (connecting) piece, and the tail.
5. • Spermiation is the process of releasing mature spermatozoa
from the Sertoli cells into the lumen of seminiferous tubules. to
migrate to the epididymis where they become fully-
differentiated motile spermatozoa.
• Disturbances in any of these three phases could give rise to
sperm cells with abnormal morphology, which in turn could
affect male fertility.
6. Spermatogenesis Spermiogenesis
Function Responsible for the formation of mature
motile sperm cells, starting from
spermatogonia
Responsible for the formation of
mature sperm cells that are not yet
motile, starting from spermatids
Stages
/ Phases
Spermatocytogenesis (mitotic phase)
Spermatidogenesis (meiotic phase)
Spermiogenesis
Spermiation (differentiation phase)
(1) Golgi phase
(2) Cap phase
(3) Tail phase
(4) Maturation phase
End
product
Four fully-differentiated motile
spermatozoa from each spermatogonium
One mature yet-to-be motile
spermatozoon from each spermatid
Location Seminiferous tubules, then epididymis Seminiferous tubules
7. Spermat0genesis process:
• The primitive sex/ germ cells appear earliest in 4th week of intra uterine life in
male baby in the wall of yolk sac as primordial germ cells. They migrate to the
developing testes and lie there in dormant stage as the cells lining the
seminiferous tubules.
• At puberty the germ cells become active and start the actual process of
spermatogenesis.
• Spermatogonia are the germ cells. They lie in the outer wall of the seminiferous
tubules. These cells are composed almost entirely of nuclear material.They are
diploid (2n). They undergo mitosis to reproduce themselves that is to increase in
number. Some of these cells replace themselves that is form spermatogonia, while
some continue development to produce sperm.
8. Contd…
• Spermatogonia destined to develop into mature sperm cells are known as
primary spermatocyte. These move from the outer portion of the seminiferous
tubule to a more central location and attach themselves around the Sertoli cells.
Primary spermatocyte undergoes meiosis. It is diploid (2n). Each day about 3
million of them differentiate into primary spermatocytes, the cells that undergo
meiosis.
• After meiosis I Primary spermatocyte to produces two secondary spermatocytes.
Here homologous chromosome pairs separate. These secondary spermatocytes
are now haploid (n) but still contain two chromatids per chromosome.
• Each of these secondary spermatocytes undergoes meiosis II to each produce
two spermatids. Here sister chromatids separate. Spermatids are haploid (n) and
each contain chromatid. The result is total 4 spermatids.
9.
10. Spermiogenesis & Spermiation
• Spermiogenesis and spermiation are such subdivisions of spermatogenesis.
• Spermiogenesis is a process by which spermatids are transformed
into mature spermatozoa.
• whilst
• Spermiation is the process where the spermatozoa are released from
the Sertoli cells into the cavity of seminiferous tubules.
• This is the key difference between Spermiogenesis and Spermiation.
11. Spermiogenesis
• Spermiogenesis is the process in which morphological changes occurs in
to spherical spermatids & it becomes elongated sperms. The changes
include:
• Appearance of the acrosomal cap from the Golgi complex.
• Nucleus become condensed, ovoid and forms the head. This is capped by
the acrosomal cap.
• The centriole divides into two parts: One of the centrioles moves to the
neck and give the axial filament. The other centriole moves distally and
gets surrounded by a small ring, the annulus.
12. Contd…
• The axial filament between the head and the annulus get surrounded by
mitochondria. This part of the spermatid is known as the middle piece.
• The axial filament elongates and forms the principle piece or the tail. Last
part is the end piece.
• Excess cytoplasm of the cell disintegrates and only membrane remains as a
covering of the spermatozoon.
• Cytoplasmic bridges break and sperms release from Sertoli cells to lie free in
lumen of seminiferous tubules.
• Still the sperm that emerge from the testes are immature, non motile and
incapable of fertilization.
13. Spermatid to sperm
it is composed of four major stages including Golgi phase, cap phase, tail formation phase and maturation phase.
14. Spermiation:
Spermiation is the process of release of mature spermatids (sperms) from Sertoli cells into the
seminiferous tubule lumen after spermiogenesis, prior to their passage to the epididymis.
• Extensive restructuring and remodelling of the spermatid to produce a streamlined spermatozoan
involves several discrete steps including
1. remodelling of the spermatid head and cytoplasm
2. removal of specialized adhesion structures
3. the final disengagement of the spermatid
• This is an important process where it determines the number of sperms that enter to
the epididymis and also the ejaculating sperm content.
15. Maturation of Spermatozoa
• The spermatozoa undergoes a process of maturation during passage though
the male genital tract (epididymis). The secretions of epididymis, seminal
vesicle and the prostate have an effect on maturation and motility of
spermatozoa. However it becomes fully motile (hyperactivated motility)
only after ejaculation into female genital tract. Sperms are viable for 48-72
hours but their capacity to fertilize is limited to 24 hours.
16. Activation in female genital tract
• Capacitation: In the female genital tract, the sperms undergo an activation process
called capacitation. It consists of enzymatic changes that result in the removal of a
glycoprotein coat and seminal plasma proteins from the plasma membrane over
the acrosome.
• Acrosomal reaction: This reaction follows capacitation and occurs after binding to
the zona pellucida. This is induced by zonal proteins. During acrosome reaction,
the enzymes are released from the acrosome. These disperse cells of corona
radiata, to penetrate zona pellucida and mature oocyte cell membrane.
17. Structure of sperm
• Each day about 300 million sperm complete spermatogenesis The human sperm
cell is about 70 µm long
- Head
- Nucleus with 23 chromosomes (haploid or n)
- Acrosome – vesicle filled with oocyte penetrating enzymes
- It is the head which binds to the egg at fertilization
- Midpiece:
- the energy for motility is generated by mitochondria
- Tail:
- motility – the beat is initiated just behind the midpiece, and then propagated along the tail
• –Once ejaculated, sperm do not survive more than 48 hours in female reproductive
tract.
21. 2. In which organ of the human male does the mature sperm stored for a time?
a) Testis
b) Epididymis
c) Vas Deferens
d) Accessory Glands
• Answer: B
22. 3. Arrange the following organs in the correct sequence for
the travel of sperm: epididymis, testis, urethra, vas
deferens.
a) Testis – urethra – epididymis – vas deferens
b) Epididymis – testis – urethra – vas deferens
c) Testis – epididymis – vas deferens – urethra
d) Epididymis – vas deferens – testis – urethra
• Answer: C
