Anatomy and Histology of Testis , Spermatogenesis

1. HUMAN
EMBRYOLOGY
11-4-19
Dr.DEVI

2. MALE REPRODUCTIVE SYSTEM &
SPERMATOGENESIS
11-04-2019

3. CONTENTS
◦Male reproductive system
◦Structure of mature spermatozoon
◦Spermatogenesis
◦Histology of male reproductive organ

4. Male reproductive system
• Two testes: formation of spermatozoa
& synthesis, release and storage of
testosterone
• Genital ducts
• Associated glands..formation of
noncellular portion of semen
– Paired seminal vesicles
– Single prostate glands
– Bulbourethral (Cowper)
glands
• Penis...delivery of semen

5. Testis
• Paired oval organs, located in the
scrotum (approx 4x3x3cm)
• Testes develop retroperitoneally,
carry a peritoneal outpouching while
descending in scrotum: tunica
vaginalis
• Tunica albuginea (irregular dense
connective tissue) surrounds each
testis
• Tunica vasculosa (highly vascular
loose connective tissue) located
immediately deep to TA forms the
vascular capsule.

6. • The posterior aspect of
TA is thickened to form
mediastinum testis.
• The connective tissue
septa radiate from MT
to subdivide each
testis into approx 250
pyramid shaped lobuli
testis.

7. • Each lobule has 1-4 blindly ending seminiferous tubules
• Richly vascularized and innervated loose connective
tissue derived from Tunica Vasculosa surrounds
Seminiferous Tubules.
• Interstitial cells of Leydig make groups within this CT.

8. • Seminiferous epithelium of STs
produces spermatozoa.
• Spermatozoa enter tubuli recti
that connect the open end of
each ST to rete testis
(labyrinthine spaces within MT).
• Spermatozoa leave the RT
through ductuli efferentes (10-
20 short tubules) which fuse
with epididymis.

9. Intratesticular genital ducts
• Tubuli recti
• Rete testis
•Connect seminiferous
tubules to epididymis

10. Tubuli recti
• Short, straight tubules
delivering spermatozoa
from the seminiferous
tubules into rete testis.
• Lined by Sertoli cells in their
first half near the ST
• Formed by seminiferous
epithelium, lined by a simple
cuboidal epithelium in their
second half near the rete
testis
• Cuboidal cells have short
stubby microvilli and most
have a single flagellum

11. Rete testis
• Consists of labyrinthine
spaces lined by a simple
cuboidal epithelium within
the mediastinum testis.
• Cuboidal cells resemble
those of tubuli recti; have
numerous short microvilli
with a single flagellum
• Immature spermatozoa
pass from tubuli recti into
rete testis

12. Ductuli efferentes• 10-20 short tubules that drain
spermatozoa from the rete testis and
pierce the tunica albuginea of testis to
conduct the sperm to epididymis
• Simple epithelium contains
noncilliated cuboidal cells or cilliated
columnar cells
• Cillia of the columnar cells move the
spermatozoa toward the epididimis
• Cuboidal cells having many
lysososomes and apical plasmolemmal
invaginations are responsible of
endocytosis (resorb most of the luminal
fluid)
• CT is surrounded by a thin layer of
circularly arranged smooth muscle.

13. Extra testicular genital ducts
• Epididymis
• Ductus deferens
• Ductus ejaculatorius

14. Epididymis
• Is a thin, long (4-6 m), highly convoluted tubule
consisting of a head, body and tail, placed at
the post end of the testis
• The lumen is lined by pseudostratified
epithelium composed of two cell types: short
basal cells with round nuclei functioning as
stem cells and the tall principal cells with
basally located oval nuclei and stereocillia,
resorbing the luminal fluid and manifacturing
glycerophosphocholine

15. • Epithelium is separated from the
underlying loose connective
tissue by a BL
• Circularly arranged smooth
muscle cells surround the CT
layer. Peristaltic contractions of
this layer help conduct the
spermatozoa to the ductus
deferens.

16. Ductus deferens (Vas deferens)
•
• Each DF is a thick walled muscular tube with
a small irregular lumen that conveys the
spermatozoa from the tail of the epididimis
to the ejaculatory duct.
• Mucosa formed by pseudostratified columnar
epithelium (principal cells are shorter) with
stereocilia and a lamina propria.
Thick outer wall is formed of smooth
muscle (three layers:inner outer
longitudunal middle circular) and collagen
fibers (blue).
• SML is invested by a thin layer of fibroelastic
connective tissue

17. Extra testicular genital ducts
• The dilated terminus of
each ductus deferens is
known as ampulla
• As the ampula
approaches the prostate
gland it is joined by
seminal vesicle.
• The continuation of the
junction of the ampulla
with the seminal vesicle
is known as ejaculatory
duct.

18. Ejaculatory duct
• Ampulla of ductus deferens
joins the seminal vesicle to
form ejaculatory duct; which
then enters the prostate gland
and opens in the prostatic
urethra at the colliculus
seminalis.
• Is a short straight tubule
• Lumen is lined by simple
columnar epithelium
• Subepithelial CT is folded
• Has no smooth muscle in its
wall.

19. Accessory genital glands
• Paired seminal vesicle
• Single prostate gland
• Paired bulbourethral
glands

20. Seminal vesicles
• About 15 cm long highly tubular structures
located between post aspect of the neck of the
bladder and the prostate gland; and join the
ampulla of the ductus deferens just above the
prostate gland
• This gland produces a fructose rich seminal
fluid that makes 70% of the volume of the
semen. It is the source of the enegry for the
spermatozoa.

21. Prostate◦ Largest of accessory glands
◦ Surrounds the urethra
◦ Stroma contains fibromuscular tissue
in which glandular tissue embedded
◦ Prostate secretes 10-30% of final
ejaculates
◦ Contains acid phosphatase,
fibrinolysin, prostate specific antigen
◦ Promotes mobility of sperm

22. Bulbourethral (Cowper’s) glands
• Paired small (3-5 mm diam)
glands located at the root of
glans penis, just at the
beginning of membranous
urethra
• Capsule contains fibroblasts,
smooth and skeletal muscle
cells
• Capsule sends septa dividing
each gland into lobules
• Epith of these compound
tubuloalveolar glands varies
from simple cuboidal to simple
columnar

23. Penis
• Is composed of three columns of
erectile tissue, each enclosed by
its own dense, fibrous connective
tissue capsule, the tunica
albuginea.
• Two of the columns of erectile
tissue, the corpus cavernosa
• Third column of erectile tissue, the
corpus spongiosum, is positioned
ventrally. Because the CS houses
the penile portion of the urethra, it
is also called the corpus
cavernosum urethrae.
• CS ends distally in an enlarged,
bulbous portion, the glans penis
(head of the penis). The tip of the
glans penis is pierced by the end of
the urethra as a vertical slit.

24. Seminiferous
tubules-
microscopic
structure

25. Seminiferous tubules- microscopic
structure
• 30-70 cm long, 150-250, convoluted
• Tunica propria (slender CT) and thick seminiferous
(germinal) epithelium make the wall of ST
• A basal lamina separates SE and the Tunica Propria
• TP contains type 1 collagen bundles housing several
layers of fibroblasts.
◦ There are spermatogenic cells and the Sertoli cells
within the SE.

26. Sertoli cells
◦ Tall columnar cells, with a basal clear oval
nucleus and complex infoldings at the apical
and lateral cell membranes
◦ Extends from basal lamina to free surface of
epithelium
• Cell cytoplasm is filled with SER, has many
mitochondria and a well developed Golgi
apparatus.
• Non dividing cells in adults

28. • Lat. cell membranes of adjacent Sertoli cells form occluding
junctions subdividing the lumen of the Seminiferous Tubules into
narrower basal and the wider adluminal compartments.
• The Sertoli cells establish a blood-testis barrier that isolates the
adluminal compartment from CT influences thereby protecting the
developing gametes from the immune system.(prevents formation
of sperm-specific antibodies)

30. Sertoli cells function in:
• supporting the developing
spermatogenic cells;
• establishing the blood- testis barrier;
• Provide nutrition to spermatogenic
cells
• phagocytosis of cytoplasm shed by
developing spermatogenic cells;
• manufacturing the following substances:
androgen binding protein, antimullerian
hormone, inhibin, testicular transferrin,
and a fructose- rich medium.

31. Spermatogenic cells
• Most of the cells composing the thick seminiferous epithelium are
spermatogenic cells in various stages of maturation.
Spermatogonia, are located in the basal compartment,
•Primary spermatocytes, secondary spermatocytes,
spermatids,spermatozoa occupy the adluminal compartment.
•Spermatogonia are diploid cells that undergo mitotic division to
form more spermatogonia, primary spermatocytes, which migrate
from the basal into the adluminal compartment.

32. spermatogenesis
◦ Formation of gametes takes place
during reproductive period
◦ Spermatogonia (type A )or germ
cells divide mitotically to give rise
to more spermatogonia (type A &
B)
◦ Spermatogonia (type B) enlarge,
or undergo mitosis to form
primary spermatocyte

33. ◦ Primary spermatocytes enter the
first meiotic division to form
secondary spermatocytes, which
undergo the second meiotic
division to form haploid cells
known as spermatids.

34. • Spermatids are transformed into spermatozoa by shedding of much of
their cytoplasm, rearrangement of their organelles, and formation of
flagella. Process of transformation of a circular spermatid to
spermatozoon is called spermiogenesis

35. Spermiogenesis
◦ Spermatid becomes spermatozoon
◦ Spermatogenesis including spermiogenesis requires about two months for
its completion
◦ Spermatid- circular containing nucleus, Golgi apparatus, centriole &
mitochondria
◦ Nucleus forms head ,Golgi apparatus forms acrosomic cap
◦ Centriole – axial filament appears to grow out of them , centriole lies in the
neck, Most of the cytoplasm of spermatid is shed, cell membrane persists
◦ Mitochondria forms a sheath around axial filament in the middle piece
region, Remaining axial filament elongates to form principal piece or tail

36. – Spermatocytogenesis:
spermatogonia
differentiate into primary
spermatocytes
– Meiosis: reduction
division whereby diploid
primary spermatocytes
reduce their
chromosome
complement, forming
haploid spermatids
– Spermiogenesis:
transformation of
spermatids into
spermatozoa (sperm)
The maturation process
(spermatid....spermatozoa)

37. Maturation and
capacitation of
spermatozoa
◦ When first formed in seminiferous tubules-
spermatozoa is immature- incapable of
fertilizing the ovum, non motile
◦ Fluid in the seminiferous tubules carries the
spermatozoa from testis to epididymis
◦ Here they are stored and undergo
maturation
◦ Spermatozoa acquire some motility after
maturation
◦ Becomes fully motile- after ejaculation when
get mixed with secretions of prostate gland
and seminal vesicles

38. Spermatozoa acquire the ability to fertilize
an ovum only after they have been in the
female genital tract
Capacitation: final step of maturation occurs
in uterus or uterine tube
When it comes in contact with zona
pellucida, changes takes place in membrane
over the acrosome and enable the release of
lysosomal enzymes, this is called acrosomal
reaction
Zona reactions : some enzymes help in
digesting the zona pellucida and in
penetration of spermatozoa through it

40. Structure of Spermatozoon
• Spermatids discard much of their
cytoplasm and form a flagellum to
become transformed into
spermatozoa, a process known as
spermiogenesis.
• Spermatozoa (sperm) are long cells
(~65 μm), composed of a head,
housing the nucleus, and a tail, which
accounts for most of its length

41. ◦ Tail of the spermatozoon is subdivided into four regions: neck,
middle piece, principal piece, and end piece.
◦ The plasmalemma of the head is continuous with the tail’s
plasma membrane.

42. Head :
◦ Piriform in shape
◦ 4 um in length
◦ Derived from nucleus which consists of 23
highly condensed chromosomes
◦ Head is covered by a cap-like structure
called acrosome (acrosomic cap/galea
capitis)
◦ Acrosome contains enzymes that help in
penetration of spermatozoon into the
ovum during fertilization

43. ◦ The chromatin in the head is extremely
condensed
◦ This makes the head highly resistant to
various physical stresses

44. • Neck :
• (~5 μmlong) connects the head to the
remainder of the tail.
• Narrow
• Contains funnel shaped basal body and
spherical centriole
• It is composed of the cylindrical arrangement
of the nine columns of the connecting piece
(basal body) that encircles the two centrioles,
one of which is usually fragmented.
• The posterior aspects of the columnar
densities are continuous with the nine outer
dense fibers.

45. ◦ Middle piece (~5 μm long) is located
between the neck and the principal
piece.
◦ It is characterized by the presence of
the mitochondrial sheath, which
encircles the outer dense fibers and the
central most axoneme.
◦ The middle piece stops at the annulus.
Two of the nine outer dense fibers
terminate at the annulus; the
remaining seven continue into the
principal piece.

46. Principal piece (~45 μm long) is the longest
segment of the tail and extends from the
annulus to the end piece. The axoneme of the
principal piece is continuous with that of the
middle piece.
Surrounding the axoneme are the seven outer
dense fibers that are continuous with those of
the middle piece and are surrounded, in turn,
by the fibrous sheath.
End piece (~5 μmlong) is composed of the
central axoneme surrounded by
plasmalemma. The axoneme
is disorganized in the last 0.5
to 1.0 μm.

47. Axial filament :
◦ Begins just behind the centriole
◦ Passes through middle piece and tail
◦ At the point where the middle piece joins the tail, the axial
filament passes through a ring like structure called
annulus
◦ The part of the axial filament which lies in the middle
piece is surrounded by a spiral sheath made up of
mitochondria

49. HISTOLOGY OF MALE
REPRODUCTIVE SYSTEM

51. ◦ Each testis is enclosed
in thick connective
tissue capsule, tunica
albuginea
◦ Internal to this is a
vascular layer of loose
connective tissue ,
tunica vasculosa.

52. ◦ Connective tissue septa arise from
tunica albuginea , runs towards
mediastinum testis dividing testis
into lobules (200- 300)
◦ Each lobule has 2-3 convoluted
seminiferous tubules and
interstitial cells

53. ◦ ST surrounded by a
layer of connective
tissue – lamina propria
◦ Consists of flattened or
spindle shaped myoid
cells arranged in one or
more layers
◦

54. Sertoli cells :
◦ Irregular
◦ Slender pyramidal cells
◦ Nuclei – ovoid, vesicular

55. ◦ Spermatogenic cells :
◦ Seen as various stages of
development
◦ From basement
membrane inwards –
spermatogonia, pri
spermatocyte, sec
spermaocyte and
spermatid
◦ Spermatozoa seen in the
lumen

57. Leydig cells
• Epithelium of
seminiferous tubules
surrounded by myoid
cells. The spaces
between the tubules
contain connective
tissue, blood and
lymphatic vessels, and
interstitial cells.
• Produce testosterone
• Large, ovoid intensely
eosinophilic

58. Epididymis
• Highly coiled ductus
epididymidis
• Its wall is made of a
pseudostratified
columnar epithelium
surrounded by
connective tissue and
smooth muscle.
• epithelial cells with
their long microvilli
(stereocilia).

59. Thank you !