Seminiferous Epithelial cycle

Spermatogenic Epithelial
Cycle(SEC)
By
Falana Benedict Abiola
B.Sc (Hons) Unilorin; M.Sc. (Anatomy) Ile-Ife
Practice Seminar 1
Department of Anatomy, College of
Medicine of the University of Lagos,
Nigeria
Matriculation Number 109091016

Outline
• Introduction to SEC
• The cycle and wave
• Selected Stages
• Structure of the testes and spermatogenesis
• Evolution of the study
• Seminiferous epithelium
• Conclusion
• References

Introduction
• Spermatogenic lineage development is a
complex process but occurs in an orderly
manner referred to as the spermatogenic cycle
((Clermont 1972)
• Proteins and mRNAs are exchanged via
cytoplasmic bridges and may help in
coordinating the synchronized development of
germ cell clones.( Braun et al.,1989)

Introduction
• Each stage is characterized by a combination
of different types of spermtogoonia,
spermatocytes and spermatids that
synchronously proceed through the
spematogenic process.
• The complete spermatogenic cycle in mouse
was

SEC
• Layers of germ cells all develop in a
coordinated, repeating programme known as
seminiferous epithelial cycle.
• In rodents, successive stages are arranged in
cylindrical segments along the STs.

• Its existence been demonstrated in many
vertebrate species. (Kerr, 1995; Sharpe, 1994)
• They are features of vertebrate spermatogenic
organization that reflect the need for a rigorous
sperm production. (Timmons et al.,2002)
Cycle and Wave

Cycle and Wave
• Cycle of the seminiferous epithelium :
– synchronous mitotic meiotic divisions
– 6 stages in man
– 4.6 cycle from sperm release (16 days per cycle)
• Waves of the seminiferous epithelium :
– in rodents and other mammals
– no waves in human seminferous tubule

Stages
• These are designated stages I-XIV of the
seminiferous epithelial cycle in rat (Leblond and
Clermont,1952).
• Twelve such stages (I-XII) have been
described in the mouse (Oakberg, 1965a)

Stages
• Stage duration is precisely timed.
• The complete spermatogenic cycle was
determined to be 8.6 days in the mouse (Okberg
1956b) and 12.6 days in rats (Hilscher et al.,1969)

Stages in the indian gerbil field rat
(Terata indica)
• Four generations of A type, a single generation
of intermediate(In) and two generations of B
type spermatogoonia are identified by Bilaspuri and Kaur
(1994).

Stages in T.indica
• Spermatocytes have been observed in
prophase, metaphase, anaphase and telophase;
in terms of size and morphology, the phases of
prophase could further be subdivided. (Bilaspuri and Kaur
1994).

Stages in the Buffalo (Bos
Bubalos)
• Using H&E preparations the SEC in the
buffalo has been divided into 8 stages;1,2,3,4
and 8 have been subdivided. Guraya and Bilaspuri (1976)

Stages in the Buffalo
• The buffalo spermatogenesis is constituted by
4.57 cycle of seminiferous epithelium which
resembles that of the bull. (Guraya and Bilaspuri 1976)

Stages 1–8 of the seminiferous epithelium cycle based on the tubular morphology system.
França L R , Godinho C L Biol Reprod 2003;68:1554-1561
©2003 by Society for the Study of Reproduction

Structure of the testes
• Tunica albuginea : fibrous connective tissue
– mediastinum :
– septa :
• Tunica vasculosa : loose connective tissue
• Lobule : 250
– seminiferous tubules : 1-4
– interstitial (Leydig) cells :
• Rete restis :

Seminiferous Tubules
• Seminiferous epithelium : stratified epithelium
– spermatogenic cells :
• spermatogonia :
• spermatids :
– Sertoli cells : supporting or sustentacular cells
• Tunica propria : lamina propria
– myoid cells (peritubular contractile cells) :
• rhythmic contraction

Spermatogenesis (I)
• Spermatogonial phase :
– type A dark (Ad) spermatogonia :
• the stem cells of the seminiferous epithelium
– type A pale (Ap) spermatogonia :
• committed to differentiation
– type B spermatogonia :
• differentiated from type A spermatogonia
• the last event in the spermatogonial phase

Spermatogenesis (II)
• Spermatocyte phase : meiosis
– primary spermatocyte : 4n
• produced by type B spermatogonia
• first meiotic division
• homologous chromosomes crossing-over
• give rise to secondary spermatocyte
– secondary spermatocyte : 2n
• second meiotic division
• give rise to spermatid

Spermatid Phase (Spermiogenesis)
• Golgi phase :
– proacrosomal granules-acrosomal vesicle
– axonemal complex : sperm tail
• cap phase : acrosomal cap
• acrosome phase :
– manchette (flagellum development), nucleus condense
• maturation phase :
– residual body is pinched off and phagocytized by Sertoli
cells

Sperm Passway
• Seminiferous tubules :
• Straight tubules :
• Rete testis (mediastinum) :
• Efferent ductules :
• Ductus epididymis : acquire motility
• Female tract : acquire fertilization ability
– capacitation : removal and replacement glycocalyx
components on the sperm membrane

Structure of Mature Sperm
• Head :
– acrosomal cap :
• acrosin : acrosome reaction
– nucleus :
• Tail :
– neck : centrioles
– middle piece : mitochondria
– principal piece : fibrous sheath and axonemal complex
– end piece : only axonemal complex

Variation in Sperm Production
• Testis Size
• Efficiency of spermatogenesis
– mitotic division
– degeneration of germ cells
• Length of spermatogenesis

Human Spermatozoon:
• 60 um long, consist of a head & a tail.
• Head: pear-shaped & flattened w/ a nuclear & a
acrosome (contains hydrolytic enzyme important for
fertilization).
• Tail: 55um in length w/ a microtubular axoneme in the
core.
Subdivided into 4 segments:
(a)The neck, containing a centriole (connect)
(b)The middle segment (5-7um), containing a
sheath of mitochondria (provide energy).
(c)The principal segment (45um), containing a
fibrous sheath (support the tail).
(d)The end piece (5-7um), containing a
microtubular axoneme.

Evolution of the study
• The definition of stages of the cycle of
seminiferous epithelium in rats was made
possible by the work of (Leblond and Clermont (1952)
• The existence of a wavy nature of
spermatogenic epithelium was discovered by
Perey et al .,(1961)

• Further more Huckins and Clermont(1968) reported the
evolution of gonocytes in the rat testes during
late embryonic and early post natal life.
• Sertoli-germ cell communications network
was reported to play a key role in regulating
SEC Jegou (1993)

• The macro, micro and molecular research on
spermatogenesis was undertaken by Kerr (1995) in a
quest to understand its control.

Evidence of Expressed Proteins
• Galectin family currently includes 10
mammalian members (Cooper and Barondes, 1999), which are
expressed in many different embryonic tissues
and adult tissues where they may be found
either in the intracellular or extracellular
compartments, or both (Harrison and Wilson 1992; Hughes, 1999)

Expressed Proteins
• These proteins have been implicated in many
different biological processes, including cell
recognition (Puche et al.,1996), cell adhesion (Cooper et al.1991;Hadari
et al. 2001; Kuwabara and Liu 1996), organization of extracellular
matrix (Hikita et al., 2000) and programmed cell death
(Akahani et al., 2001; Perillo et al., 1995)

Galectin 1 expression in the developing testis.
Timmons P M et al. Development 2002;129:635-647

Seminiferous epithelium(SE)
• A complex and highly dynamic tissue.
• Male reproductive success ultimately depends
on the ability of this tissue to produce
prodigious numbers of sperm consistency.

Seminiferous epithelium(SE)
• Its organization into tubules serves provide
maximum area for sperm production.
• The structure of the epithelium and the precise
orchestration of spermatogenesis makes sperm
release regular.

Seminiferous epithelium
• Developing cells gradually traverse the
epithelium from the basement membrane to
the apical surface .
• They are then released into the tubule lumen
as spermatozoa.
• Spermatogenesis progresses.

• The adult Seminiferous epithelium always
contains several layers of germ cells at
different stages of development.

• Stages of the seminiferous epithelial cycle in
sections of adult testes has been determined by
light microscopy ( leblond and Clermont, 1952; Parvinen, 1982;
Russell et al.,1990)

Review of the germinal epithelium
Sertoli cell Germinal epithelium
• 1. Basal lamina
• 2.Spermatogonia
• 3. spermatocyte first order
• 4.Spermatocyte second
order
• 5. spermatatid
• 6.mature spermatid
• 7.sertoli cell
• 8.tight junction

SeminiferousSeminiferous
TubulesTubules

Seminiferous TubulesSeminiferous Tubules
D = 150 - 250um, 30 - 70cm long,
Spermatogenic Spermatogenic cells
epithelium Sertoli cells
Basement membrane
Collagenous fibers
Limiting membrane
Myoid cells

Mis. Egg , I miss you
very much!
Mr. sperm,
Mr. Sperm , I
miss you very
much too !

Sertoli cells:
Columnar cell rest on B.M., the free surface reaches to
lumen. spermatogenic cells locate b/w adjacent cells
Features & function:
LM: no clear outline, basally-
located, ovoid nucleus w/ a
distinct nucleolus.
EM:
(l) abundant sER., Gl., Ly.,
Mf., & Mt.
(2) Tight junctions present
b/w adjacent Sertoli cells
(isolate spermatogonia from
other spermatogenic cells).

Function:
(l) Support & nourish spermatogenic cells;
(2) Secrete fluid to help the sperm moving;
(3) Phagocytize & digest the residual bodies
(4) Synthesize & secrete ABP (androgen binding
protein) which combines androgen in
seminiferous tubule to stimulate spermatogenesis;
(5) Form the blood-testis barrier: Tight junction
constitute the main part (rest: B.M. & limiting
membrane). Function: separates germ cells from
immune system & prevents auto-immune
reaction.
(6) Prevent some physical & chemical factors from
damaging germ cells, e.g. radiation, body
temperature, infection

Conclusion
• The SEC is a conserved feature necessary for
the sustenance of fertility in Man.
• Further studies on SEC in other Mammals
would shed more light on these complex
phenomena.

References
• Timmons, P.M., Rigby, P.W.J.,Poirier F.,(2002).The
murine sminifeous epithelial cycle is pre-figured in
the sertoli cells of the embryonic testis
• Bilaspuri, G.S and Kaur, I (1994). Spermatogenic
cells and stages of the seiniferous epithelial cycle in
the indian gerbil rat, Terata indica

References
• Prince C.G and Loveland K.L (2000).Germ cell
suicide: New insights into apoptosis during
spermatogenesis. Bioessays 22, 423-430
• Perey, B.,Clermont,Y., and leblond, C.(1961)The
wave of the spermatogenic epithelium in the rat.
Am .J.of Anat.108, 47-48
• Leblond, C.P andClermont,Y.(1952).Definition of the
stages of the cycle of seminiferous epithelium in the
rat.AnnNew yorkacad.sci.55, 548-573

References
• Kiers zemembaum, A.L. (2001). Apoptosis during
spermatogenesis: The trills of being alive. Mol.
Reprod. Dev. 58, 1-3
• Kerr, J.B.(1995)Macro, microand molecular research
on spermatogenesis: quest to understandits control.
Microsc.Res.Tech.32, 364-384

References
• Jegou, B .(1993).The sertoli-germ cell
communications network in mammals.
Intrev.Cytol.14725-96
• Hughes, R.C.(1999). Secretion of galectin family of
mammalian carbohydrate –binding proteins. Biochim
biophys.Acta.1473, 172-185
• Huckins, C and Clermont, Y.(1968).Evolution of
gonocytes in the rat testes during late embryonic and
early post-natal life . Arch.Anat.Histol.Embryol.51-
341-354

References
• Hikita C..,
Vijayakumar.,S.,Takito.,J.,Erdjument-Bromage,
H.,Tempest, P.,and Al-awquati, Q.
(2000).Induction of terminal differentiation on
in epithelialcells requires polymerization of
hensin by galectin 3..J.Cell Biol.151, 1235-
1246
• Eddy, E.M., and O’Brien, D.A.,(1998).Gene
expression durin mammalian meiosis.
Curr.top.Dev.Biol37,141-200

References
• Enders, G.C.(1993).Sertoli-sertoli and sertoli-
germ cell communication. In the sertoli cell.
(ed L.D. Russel and M.D.Griswold), pp.447-
460. Clearwater, FL. Cache RiverPress
• Clermont, Y and Perey, B.(1957).Quantitative
study of the cell populationof the seminiferous
tubules in immature rats.Am. J. Anat100, 241-
268

Seminiferous Epithelial cycle

More Related Content

What's hot (20)

Similar to Seminiferous Epithelial cycle (20)

Recently uploaded (20)

Seminiferous Epithelial cycle

Editor's Notes