Male reproduction

1. Male Reproductive System
Undergraduate – Graduate
Histology Lecture Series
Larry Johnson, Professor
Veterinary Integrative
Biosciences
Texas A&M University
College Station, TX 77843

2. Objectives
To examine the testis (which produce spermatozoa), excretory ducts
(which transport and mature spermatozoa), and accessory glands
(whose secretions support the viability of spermatozoa) for
characteristics and functions the male reproductive system.
To learn what structures and hormonal regulation facilitate the male
gonad to produce an exocrine secretion (the spermatozoon) and an
endocrine secretion (testosterone).

3. Outline
History
Spermatozoon
Spermatogenesis
Sertoli and Leydig cells
Hormonal control
Epididymal and
accessory glans
characteristics and
functions
Fertile ejaculate

4. First scientific endocrine
study involved the testes
of roosters studying the
observable effects of
testosterone on the
secondary sex structures.
Transplanted tested
maintained wattles and
comb growth in castrated
roosters.
hen

5. Functions of Male Reproductive System are to:
- produce, maintain, and transport mature spermatozoa (the
male gametes),
- produce nutritive and protective fluid (semen), and
- discharge the spermatozoa-containing semen within the
female reproductive tract during mating.

10. Primate
sperm

11. Mouse
spermatozoon

14. Rat Bull

16. Human

17. Details of spermatozoa
The
annulus marks the
end of the middle
piece (houses the
mitochondria) and
beginning of the
principal piece of the
spermatozoon
Horse

18. Horse
Middle piece with mitochondria

19. Spermatozoa are produced
in seminiferous tubules in the testis.
Horse
Human
Human

20. Human testis
Seminiferous
tubules
Leydig
cells
Slide 165

21. Human testicular capsule
Mesothelium
Artery
Vein
34455
Slide 165

22. Human testis toluidine blue
19680
Spermatozoa are produced in the seminiferous epithelium lining
the lumen of the testicular tubules. Testosterone is synthesized
by Leydig cells located between seminiferous tubules.
Seminiferous
epithelium
Leydig
cells
Seminiferous
tubules

23. Human testis toluidine blue
Two kinds of cells present in the seminiferous
epithelium: Sertoli cells and germ cells:
Sertoli cells nurse germ cell development.
Germ cells
Nuclei of Sertoli cells 19680
467

24. Horse Seminiferous Tubules

25. Seminiferous tubules are composed of
seminiferous epithelium and boundary cells:
Myoid Cells
Sertoli Cells
Germ Cells
Spermatogonia,
Spermatocytes,
Spermatids
Human

26. Myoid cells
Sertoli cells
Germ cells
Spermatogonia,
Spermatocytes,
Spermatids
Human
Seminiferous Tubules
composed of:

28. UT165 larger secondary spermatocyte nuclei and smaller Golgi phase spermatid nuclei
human testis
Meiotic activity

29. #92 secondary spermatocytes
To find secondary spermatocytes, one needs to find a tubule in stage VI of the spermatogenic cycle
with metaphase figures in meiosis and no (almost no) pachytene primary spermatocytes. The
pachytene primary spermatocytes are the immediate precursor to secondary spermatocytes.
metaphase figures in meiosis
Pachytene primary
spermatocytes
Letotene primary
spermatocytes

30. Slide 92: Testis
Sertoli cells
Leydig (interstitial)
cells
Tunica albuginea
Basement membrane
Myoid cell
Seminiferous tubules
Residual bodies
Early and late spermatids

31. Spermatogenesis is Divided into
3 Main Events
Event Cell Type Duration
Spermatocytogenesis Spermatogonia 27 Days
Meiosis Spermatocytes 24 Days
Spermiogenesis Spermatids 23 Days
Combined Duration = 74 Days

32. Spermatocytogenesis
Meiosis
Spermiogenesis

33. Spermatocytogenesis
Has Two Functions
Produces primary spermatocytes which result in
the production of sperm 47 days later.
Produces stem cells which insure a constant
supply of germ-cell precursors throughout life.

34. Spermatocytogenesis
Horse

35. Meiosis (only in spermatogenesis
and oogenesis)
Exchange of genetic material in homologous
chromosomes (leptotene, zygotene,
pachytene, and diplotene steps of
development)
Produces haploid condition of gametes

36. Meiosis
Exchange Of Genetic Material

40. Secondary
Spermatocytes

41. Meiosis
Produces Haploid Condition of Gametes

42. Spermiogenesis
(differentiation of spermatids with round nuclei
to those characteristic of spermatozoa)
Acrosome from Golgi
Nuclear condensation and
elongation with appearance
of the spermatid manchette
Flagellum (projects through
the flagellar cannel during
development)
Shedding excess cytoplasm Manchette
Flagellar cannel

43. Golgi phase
Cap phase
Maturation phase
Elongation phase

44. Maturation phase

45. Horse
Spermiogenesis
human
Manchette

46. Spermatid nucleus
Golgi
Developing acrosome

47. Cis face
Spermatid showing the developing acrosome
over its nucleus. Acid phosphatase enzymes
(black precipitates) first appear in the trans face
of the Golgi apparatus and are transferred to the
developing acrosome via transport vesicles.
Nucleus
Cytosol
Golgi
Trans face
Transport vesicles
Golgi
Acrosomic vesicle
of a spermatid
Testis
Black acid
phosphatase
precipitates in
the developing
acrosome
Acrosomal
cap

48. Manchette is a transient organelle
as it is not found in spermatozoa
Flagellar
cannel

49. Flagellar cannel

50. Flagellar
cannel
Annulus
When the annulus migrates to end
of middle piece, it removes the cell
membrane of the flagellar cannel
from the surface of the developing
flagellum in the middle piece region
and allows mitochondria access to
that portion of developing tail.
Mitochondria are found only in the
middle piece on spermatozoa as that
is the only region with access.

53. Residual bodies Spermatids and
Spermatozoa

54. Residual bodies

55. Sertoli Cells
• Provide support and nutrition to developing germ cells
• Release spermatids as sperm
• Phagocytize degenerating germ cells and residual bodies
• Secrete:
– Androgen binding protein
– Calmodulin
– Plasminogen activator
– Inhibin
• Blood testis barrier

56. Human – infertile man

59. Blood-testis occluding
junctions between sertoli
cells in seminiferous
tubules
Occluding
junctions between
Sertoli cells

60. Human spermatogenesis: path followed by given cell
Blood Testis Barrier
Basal compartment
with spermatocytogenesis
Adluminal compartment with meiosis and spermiogenesis

61. Intercellular Bridges
(cytoplasmic bridges)
Cause - incomplete cytokinesis
Found among clusters of spermatogonia,
spermatocytes, or spermatids (never between cells
in different steps of development, e.g., never
between spermatogonia and spermatocytes)
Possible functions
Mediate both differentiation and degeneration of
spermatogonia
Maintain synchronous development

62. Intercellular
Bridges
Occluding junctions between Sertoli cells
are still above
but now appear below the
zygotene spermatocytes

63. Efficiency of Spermatogenesis
Species DSP/g (106)
--------------------------------------------
Rabbit 25
Hamster 24
Boar 23
Rat 20-24
Rhesus monkey 23
Ram 21
Stallion 16-19
Bull 12
Human 4-6

64. Spermatogenic Cycle Length
Species Duration (Day)
Prairie Mole 7.2
Hamster 8.7
Mouse 8.9
Rhesus Monkey 9.5
Rabbit 10.7
Stallion 12.2
Rat 12.9
Bull 13.5
Beagle Dog 13.6
Human 16.0

65. Testicular interstitium human
Nerve
Myoid
cells
Artery
, Leydig cells
Fibroblasts,
19680
Mitotic figures
in dividing
spermatogonia
to produce
primary
spermatocytes
Spermatogonia
Lipid droplets
in Sertoli cells
Sertoli cell nucleus
Primary
spermatocytes

66. 19680
Lymphatic
vessel
Artery
Leydig cells
Lymphatic
vessel
Myoid
cells.
Seminiferous
epithelium
Capillaries
Nerve
Leydig
cells
Lipid droplets
Fibroblasts
Since developing
germinal cells
require a higher
(100 fold)
concentration of
testosterone than
do other cells,
Leydig cells are
located close to
seminiferous
tubules.

67. Odd : What appears to be Leydig cells inside the nerve in the human testis.
Leydig cells Leydig cells ???
Nerve
19670

69. Horse

70. Hormonal Control of
Spermatogenesis
Hormone Cell Stimulated In Spermatogenesis
FSH Sertoli Cells Spermatocytogenesis
Spermiation
LH Leydig Cells Meiosis
(Testosterone)

72. Deleterious Influences on
Spermatogenesis
• Heat
• Irradiation
• Chemicals
• Aging

74. Extragenital Components of
the
Male Reproductive System
Excretory Ducts
Composition (Rete
Testis, Efferent Ducts,
Epididymis, Ductus
Deferens, Ejaculatory
Ducts, Urethra)

77. Human testis: junction of seminiferous tubule and rete
testis for sperm to exit (toluidine blue)
19709
Junction of
seminiferous tubule
and rete testis tubule
Rete
testis
Region of the
mediastinum testis

78. Testis and epididymis – efferent
duct and epididymis
467
Profiles of the
epididymal duct
Efferent
ducts
Rete testis
tubules
Seminiferous
tubules

79. Efferent ducts
199
Lumen
Efferent ducts have a characteristic scalloped
luminal profile due to alternating groups of high and
low columnar cells in the lining epithelium
True cilia on their apical
surface help move
sperm through the duct.
19673
Horse efferent duct

80. True ciliated cells (efferent duct) and stereociliated cells
(epididymis, with sperm in lumen) of psudostratified columnar
epithelium (toluidine blue)
19678
Efferent duct
Epididymis

81. 199
Epididymis
467
19673
19716
Extremely long (30µm), branching
microvilli (stereocilia) projects from
the apical surface of these cells
Stereocilia
Head
Tail of epididymis
Head
Smooth muscle
layer is thicker in
more distal
regions of
epididymis
Efferent duct
Efferent duct

82. Human

89. Human

90. DUCTUS DEFERENS IN THE SPERMATIC CORD
Blood vessels and ductus deferens
Smooth muscle,
extremely thick
layers
Psudostratified columnar epithelium,
but lower in height
Nerve
Epithelium
and its
lamina
propria,
showing
longitudinal
folds into
the lumen
196

91. Mechanisms of Sperm Transport
Location Force
Seminiferous tubules Bulk flow (10 ul/g/hr) minor
Contractions of myoid cells
Rete testis Bulk flow ciliary action
Efferent ducts Bulk flow ciliary action
Epididymis Contractions of smooth
muscle
Ductus deferens Contractions of smooth
muscle during ejaculation
speed is 800 mm/second

92. Spermatic cord 38
Human testis and epididymis
Spermatic cord
Testis
19678

95. Epididymal
Spermatozoan
Maturation
Fertility
Motility
Nature of plasma membrane
Mitochondrial structural stability
Chromatin stability

97. Seminal vesicle, monkey
168
Branched network
produces a
"honeycomb"
appearance

100. Prostate
271
Prostate is a firm mass of
collagenous connective tissue and
smooth muscle that is invaded by
numerous glandular outpocketings of
the urethra
Note the abundance of smooth
muscle in its interstitium.
Lumen
of gland

101. 169
Prostate

103. BULBOURETHRAL
GLAND

106. Two main function of male
reproductive system are to:
Produce male gametes
Deliver male gametes

108. Penis – transitional epithelium and
surrounding spongy cavernous of penal urethra
277
Dense connective tissue bands surround the cavernous erectile
tissue. There is erectile tissue (spongy cavernous) that surrounds
the penile urethra. This allows the urethra to stretch when seminal
fluids are traveling down its length when the penis is rigid.
Spongy cavernous
Cavernous
erectile tissue
Transitional
epithelium
Smooth
muscle
Nerve

109. Variations in the
Microvasculature
Common
Arteriole  Capillary 
Venule
Shunts
Arteriole  Metarteriole
 Venule
Artery  Av Shunt 
Vein

110. Fig. Mechanism of erection
Erection occurs as a complex process, constituted
by psychological, neurological, hormonal, and
vascular factors.
the penis is composed of three basic anatomical
structures – two longitudinal cavernous bodies (a
kind of chambers) and one spongy body, including
the urethra. These are the cavernous bodies that
(supplied by respective arteries) increase their
volume during erection, owing to the inflowing blood.
arteries (as opposed to veins) have their muscular
layer composed of smooth muscles which – by
dilation or contraction – regulate the blood flow.

112. Sexual arousal and increasing activity of the autonomic
nervous system stimulates the release of neurotransmitters at
nerve endings in the cavernous bodies or in the endothelium
of the arteries. This leads to secretion of NO – nitric oxide,
which is one of the strongest smooth muscle relaxants. With
dilated cavernous arteries, the amount of blood flowing into
the penis increases, and its outflow is hindered by a
physiological compression of some specific veins. Moreover,
contraction of the ischiocavernous muscle stabilises the penis
in erectile position. A key factor of effective erection is the
condition of the vascular system, ensuring a proper perfusion
of the reproductive organs. Any pathologies of this system
(e.g., atherosclerosis, coronary disease, hypertension) lead to
problems with erection.

113. Accessory Glands - Composition and
Secretion
Accessory glands Secretion
Seminal vesicles Fructose fibrinogen
Prostate Citrate fibrinolysin
Bulbourethral gland Mucus-like lubricant
Glands of Littré Mucus

114. Functional Properties of the Accessory Glands
Specific contributions of seminal plasma as measured by the
split ejaculate method
Fraction of
Ejaculate Contains Source
First 90% Of All Citrate Prostate
90% Of All Sperm Ductus Deferens
Last 90% Of All Fructose Seminal Vesicles
Developmental response to androgens

115. CHARACTERISTICS OF FERTILE
HUMAN EJACULATES
GOOD VISCOSITY (CLOT
THEN DISPERSE)
about 3 ml in volume

119. Bruce Alberts, et al. 1983. Molecular Biology of the Cell. Garland Publishing, Inc., New York, NY.
Bruce Alberts, et al. 1994. Molecular Biology of the Cell. Garland Publishing, Inc., New York, NY.
William J. Banks, 1981. Applied Veterinary Histology. Williams and Wilkins, Los Angeles, CA.
Hans Elias, et al. 1978. Histology and Human Microanatomy. John Wiley and Sons, New York, NY.
Don W. Fawcett. 1986. Bloom and Fawcett. A textbook of histology. W. B. Saunders Company,
Philadelphia, PA.
Don W. Fawcett. 1994. Bloom and Fawcett. A textbook of histology. Chapman and Hall, New York, NY.
Arthur W. Ham and David H. Cormack. 1979. Histology. J. S. Lippincott Company, Philadelphia, PA.
Luis C. Junqueira, et al. 1983. Basic Histology. Lange Medical Publications, Los Altos, CA.
L. Carlos Junqueira, et al. 1995. Basic Histology. Appleton and Lange, Norwalk, CT.
L.L. Langley, et al. 1974. Dynamic Anatomy and Physiology. McGraw-Hill Book Company, New York, NY.
W.W. Tuttle and Byron A. Schottelius. 1969. Textbook of Physiology. The C. V. Mosby Company, St.
Louis, MO.
Leon Weiss. 1977. Histology Cell and Tissue Biology. Elsevier Biomedical, New York, NY.
Leon Weiss and Roy O. Greep. 1977. Histology. McGraw-Hill Book Company, New York, NY.
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A.L. Mescher 2013 Junqueira’s Basis Histology text and atlas, 13th ed. McGraw
Internet images and videos on biological presentations
Many illustrations in these VIBS Histology YouTube videos were modified
from the following books and sources: Many thanks to original sources!

120. During the hour of this lecture the
average male produced 6.6 million
spermatozoa

125. Spermatogenesis is Divided into
3 Main Events
Event Cell Type Duration
Spermatocytogenesis Spermatogonia 27 Days
Meiosis Spermatocytes 24 Days
Spermiogenesis Spermatids 23 Days
Combined Duration = 74 Days

126. Spermatogenic Cycle
Cycle of seminiferous epithelium is the series of
changes in a given region of seminiferous
epithelium between two appearances of the
same developmental step.
Using spermiation as a reference developmental
step, the cycle would be all events that occur
between two consecutive spermiations.

128. Similarities
College vs. Spermatogenesis
Duration of entire process is longer
than the cycle length
Multiple groups of participants develop
simultaneously
Attrition of participants reduce product
yield
Timing of entry of participants in
different groups create defined
stages of the cycle

129. Stages of the
spermatogenic
cycle
in humans

130. Human spermatogenesis: path followed through
spermatocytogenesis, meiosis, and spermiogenesis as
a given cell travels through five spermatogenic cycles

134. Stage
A stage of the cycle of seminiferous epithelium is
defined by an association of spermatogonia,
spermatocytes, and spermatids whose
developmental age differs by a multiple of the
cycle length plus a common remainder.
The value of the remainder differs for each stage
of the cycle.

135. Multiple Remainder Multiple Remainder
72/16 = 4 + 8 66/16 = 4 + 2
56/16 = 3 + 8 50/16 = 3 + 2
40/16 = 2 + 8 34/16 = 2 + 2
24/16 = 1 + 8 18/16 = 1 + 2
8/16 = 0 + 8 2/16 = 0 + 2
Stage II Stage VI
Stage (cycle of the seminiferous epithelium or spermatogenic cycle)
- man-made (man defined) divisions of the spermatogenic cycle
- cellular association of germ cells at defined developmental steps
- association of spermatogonia, spermatocytes and spermatids whose
developmental ages differ by a multiple of the cycle length plus a
common remainder (unique for a given stage)

138. Differences
College vs. Spermatogenesis
Multiplying component of
participants in
spermatogenesis
Continuous entry of
participants in
spermatogenesis
manifested by the wave of
spermatogenesis along
the tubular length

139. Wave of the seminiferous
epithelium (not in humans)
"The wave is in space what
the cycle is in time."
Horse

140. rat