Male Infertility: Sperm Diagnosis, Management and Delivery Jayant G. Mehta, Bryan Woodward
Note: Page numbers in bold or italic refer to tables or figures respectively.
Accessory sex glands 12
Acridine orange test (AOT) 48, 49
Agglutination 12, 66
Aggregation 66
Agitator 10, 10
Alcohol, effects of, on fertility 104
Alpha-receptor blocking agents, and retrograde ejaculation 90
Androgens 4
Aneuploidy testing 115
Annexin-V 113
Antibiotics, in culture media 75, 75
Antidepressants, and retrograde ejaculation 90
Antifertility factor (AF-1) 38
Antioxidant therapy 58, 59
Antisperm antibodies (ASAs) 12, 17, 45, 51, 5960
bypassing of, with ART 5354
epidemiology of 51
causes of 53
prevention of 53
immunological infertility and 5152
infertility 51
treatment of 5354
testing for 51, 52
vasectomy and 53, 53
Array comparative genomic hybridization (array-CGH) technology 115
ART see Assisted reproduction therapy (ART)
ASAs see Antisperm antibodies (ASAs)
Aspermia 69
Assisted reproduction therapy (ART) 37, 40, 45, 4849, 53, 7179, 93, 97
culture media for 2527 (see also Culture media)
impact of, on sperm function tests 49 (see also Sperm function tests (SFTs))
sperm morphology in, influence of 2122
Atomic force microscopy 114
Azoospermia 5, 13, 65, 67, 81, 93, 98
non-obstructive 68, 69
obstructive 68, 69, 81
Bacteriospermia 76
Blood-borne virus (BBV), screening for 72
Bulbourethral gland 1
Cancer patients
sperm banking for 98100
sperm cryostorage, legal issues related to 122
Candida albicans 77
Capacitation 28, 37 see also Sperm preparation
Cellometer counting chamber 12, 13
Cell-Vu 12, 13
Cervical mucus 47
Chlamydia trachomatis 58
Chromosome microdeletions 48
Clomiphene (clomiphene citrate) 62, 69, 105
Coitus interruptus 8, 66
Collection artifacts 66
COMET (Single cell gel electrophoresis) assay 48, 49
Competence matrix 119, 119
Computer-aided sperm analyses (CASA) 17
Computer-controlled sperm freezing 95, 96
Congenital bilateral absence of vas deferens (CBAVDs) 69
Congenital rubella syndrome 121
Corpora cavernosa 2
Corpus spongiosum 2
high-security straws 94, 95
high-security tubes/vials 95, 95 Cryoprotectant medium (CPM) 94
Cryptorchidism 57, 57
Culture media 2526, 26, 26
amino acids in 3132
antibiotics in 75, 75
back-to-nature principle 25, 26
development of 27, 27
ejaculated sperm journey and 28, 28
ionic composition 29
pH 29, 2931, 30, 31
phosphate 29
let-the-embryo-choose principle 25
macromolecules in 32
nutrients in 28
glucose 29
lactate 2829
pyruvate 28
osmolality of 32, 3233
preimplantation development and 2728
sequential and monoculture media, constituents of 28
sperm selection process and 25, 25
vitamins in 32
Cytomegalovirus (CMV) 7778
Diff-Quik stain 15
Dimethylsulphoxide (DMSO) 94
Direct swim-up technique 42 see also Sperm preparation
Discontinuous Percoll gradient method 3839
Dithiothreitol (DTT) 127
Donor sperm 93
Donor sperm banking 123
Earle's balanced salt solution 27
Efferent ductules 2
Egg yolk, as extender 94
antegrade 90
normal 89, 89
retrograde (see Retrograde ejaculation (RE))
Ejaculatory duct 2
Ejaculatory duct obstruction (EDO) 65, 69
Electroejaculation 69
Enzyme-linked immunosorbent assay (ELISA) 52
Eosin–nigrosin test 16
Epididymal obstruction 69
Epididymis 1, 2, 3
Escherichia coli (E. Coli) 75
Ethical issues, related to ART 123124
European Tissues and Cells Directive (EUTCD) 7174, 8485, 94, 120, 121
European Union (EU) Directive, for sperm laboratories 119
authorities and enforcement 119120
cryopreservation 121
documentation 120121
equipment and materials 120
facilities 120
laboratory testing 121
personnel 119, 119
quality management 121
traceability 120
EUTCD see European Tissues and Cells Directive (EUTCD)
Evie insemination device 104, 105
Extenders 94
External quality assessment (EQA) service 17
Flow cytometry 46, 52
Fluorescence-activated flow cytometry 126
Fluorescent in situ hybridization (FISH) 115, 126127
Follicle-stimulating hormone (FSH) 4, 83, 105
Gardnerella vaginalis 58
Genital tract infections 69
Globozoospermia 15
Glucose, in culture media 29
Gonadotropin-releasing hormone (GnRH) 4, 5
Gonadotropins 105
Ham's F10 or T6 solution 27
Hematospermia 11
Hemizona assay 48, 48
Hemocytometer chamber 1213, 14
Hepatitis B virus (HBV) 71
Hepatitis C virus (HCV) 71, 74
Hoechst 33342 126
human chorionic gonadotropin (hCG) 67, 105, 106, 108
Human immunodeficiency virus (HIV) 71, 74
Human serum albumin 30, 31
Human sperm cryobanking 93
indications for 93
autoconservation 93
donor sperm conservation 93
methods of 9398
cooling/freezing method 9596
cryoprotectants 94
packaging container 9495, 95
pre-freeze and post-thaw preparations 9798
sperm freezing 9394
sperm thawing 97
storage tanks and facilities 97, 97
storage temperature 9697
oncological patients and 98100
Human sperm toxicity test (HSTT) 45, 49
Human tubal fluid (HTF) 27
Hyaluronan-binding assay 48
Hyaluronic acid-based sperm binding assays 113, 113
4-(2-Hydroethyl)-1-piperazineethanesulphonic acid (HEPES) 30
Hypogonadotropic hypogonadism (HH) 5, 67
Hypo-osmotic swelling (HOS) test 16, 27, 46, 46, 84, 112
Hypospadias 7, 57, 57
ICSI see Intracytoplasmic sperm injection (ICSI)
Immotile cilia syndrome 5
Immotile sperm viability assay 112
Immunobead test (IBT) 52
Infertility, male 5, 7, 51 see also Semen analysis (SA)
drugs for treatment of 6162
retrograde ejaculation and 89
substances causing 5758, 59
varicocele and 60 (see also Varicocele)
Insemination program 103
emotional support and counseling for 109
fertility nurse's role in 103
intracervical insemination 104, 105
intrauterine insemination 104, 105
loading of IUI catheter 107
ovulation induction and cycle monitoring 104105, 106
patient preparation for insemination 107
planning of 104, 104
semen sample collection 106107
standard operating procedures (SOPs) for 104
steps after insemination procedure 108
ultrasound scanning 105106
vaginal and pelvic examinations and insemination process 107108
Internal quality control (IQC) 17
Intracytoplasmic morphologically selected spermatozoa injection (IMSI) 111, 112
Intracytoplasmic sperm injection (ICSI) 53, 54, 60, 77, 8182, 91, 93, 111 see also Surgical sperm retrieval (SSR)
and bacterial contamination 77
risk of infection during 77
Intrauterine insemination (IUI) 22, 41, 53, 54, 67, 69, 7275, 9799, 104106, 108, 126
In vitro fertilization (IVF) 38, 4041, 45, 49, 53, 54, 71, 7478, 97, 111
pH-ranges of sequential and monoculture media for 30, 31
sperm morphology in, influence of 21
IUI see Intrauterine insemination (IUI)
Kremer test 47
Kurzrok–Miller test 47
Lactate, in culture media 2829
Laser tests, for testing viability in immotile sperm 112, 113
Leukocytospermia 58
Leydig cells 4
Liverpool Solution 91, 91
Luteinizing hormone (LH) 4, 105
Makler counting chamber 12, 13
Male sex organs
anatomy of 1, 12, 2
accessory sex glands 12
epididymis 1
penis 2
scrotum 2
testes 1, 2
blood supply of 23
innervation of 3
Microbial contamination 7576
laboratory practice for reducing 7677
Microepididymal sperm aspiration (MESA) 81 see also Surgical sperm retrieval (SSR)
Microscopic sperm organelle morphological evaluation (MSOME) 111, 112
Microsort see Fluorescence-activated flow cytometry
Mixed agglutination reaction (MAR) 52, 60, 66
3-(N-morpholino)-1-propanesulfonic acid (MOPS) 30
Motility, sperm, assessment of 1112
Multitube direct swim-up technique 42 see also Sperm preparation
Mycoplasma genitalium 77
Necrozoospermia 16
Neubauer hemocytometer 12, 14
Nurse-led clinics 103 see also Insemination program
Oligozoospermia 66, 70, 98
Oocyte–cumulus–corona complex (OCC) 39
Ovarian hyperstimulation syndrome (OHSS) 104
Oxidative stress induced male fertilit 58, 59
Pap-stain 15
‘Partner donation’ 7172
Penis 2, 3
Pentose phosphate pathway (PPP) 29
Pentoxifylline 112
Percoll 38, 41
Percutaneous sperm aspiration (PESA) 81 see also Surgical sperm retrieval (SSR)
pH buffering 3031
Phenol red, use of, as a pH indicator 31
pH, semen 11
Phthalates 57
Plasmalogens 37
PLCzeta 114
Polyzoospermia 66
Postmortem sperm retrieval (PMSR) 123
Potassium simplex optimized medium (KSOM) 27
Primordial germ cells 3
Prostaglandins, and uterine contractions 38
Prostate glands 12
Pyruvate, in culture media 28
Quinacrine chloride 125126
Raman spectroscopy 114
Reactive oxygen species (ROS) 58
Rete testes obstruction 69
Rete testis 1
Retrograde ejaculation (RE) 69, 89, 89
causes of 89
bladder neck and prostate surgery 8990
congenital 90
diabetes mellitus 90
drugs 90
operative nerve damage 90
spinal injury 90
treatment of 90
bladder conditions, adjustments of 91, 91
drug treatments 90
operative measures 90
retrieving sperm from urine 91
special maneuvers 90
Rotator 10, 10
Round cells 1617
Scrotum 2, 3
Semen, abnormal 65
aggregation and agglutination 66
color 66
fructose 65
low volume 65
motility 67, 69
pH 65
round cells 67, 68
sperm concentration 6667, 67, 68
viscosity and liquefaction 66
zinc and neutral α-glucosidase 6566
Semen analysis (SA) 7, 45, 6567 see also Semen, abnormal
computer-aided 17
laboratory area for 10
macroscopic assessment
color 11
liquefaction and viscosity 11
pH 11
volume 1011
microscopic assessment 11
antisperm antibodies 17
count 1213, 13, 14
equipment for 11
morphology 13, 15, 1516, 16
motility 1112, 12
round cells 1617
vitality 16
performers of 7
production to, time from 10, 10
quality assurance, need for 17
reasons for 7
report of 1718, 18
sample production for
home production 8
patient information and instructions 810
production room 78, 66
specimen container 8
staff training for 7
and treatment
aspermia 69
azoospermia 6769
genital tract infections 69
low/high volume semen 67
sexual dysfunction 6970
Semen quality, poor
environment and 57, 5758, 58
immunological causes of 5960
inflammatory and infectious causes of 58, 59, 59
varicocele and 6061, 61
Seminal plasma 37
factors in, affecting fertilization 3738
removal of 3738
and sperm motility and viability 37
sperm separation from 3839
density gradient centrifugation 3839
swim-up technique 38
Seminiferous tubules 1, 2, 2
Sertoli cells 4
Sex selection 125
Microsort for 126128
description of 126127, 127
efficacy of sorting process 127, 127
history and background 126
outcomes 127128, 128
natural methods for
diet and vaginal pH 125
timing of intercourse 125
X- and Y-bearing sperm, physical separation of 125126
Sildenafil citrate (Viagra) 69
Specimen container, semen 8
androgen regulation of 45
hormonal dependency of 5
organization of 34, 4
Spermatogonia 3
Spermatozoa 1, 2
function of 5
production of 3, 3, 4
Sperm bioassay 4849
Sperm chromatin dispersion test (SCD) 48, 49
Sperm chromatin structure assay (SCSA) 48, 49
Sperm count 12
Sperm cryostorage, legal issues related to 121122
cancer patients and 122
information to patients 122
posthumous-assisted reproduction 122123
postmortem sperm retrieval 123
storage contracts for patients 122
Sperm DNA fragmentation index 48, 49
Sperm DNA, integrity of 113114
Sperm function tests (SFTs) 45
hypo-osmotic swelling test 46, 46
objective of 45
sperm acrosome reaction 46
sperm–cervical mucus interaction 4647
sperm chromatin assessment 48
sperm longevity assessment 46
sperm maturity appraisal 48
sperm–zona pellucida binding 4748
stress tolerance test 45
vitality testing 46
Sperm head polarization microscopy 114
Spermiation 3
Spermiogenesis 3, 3
Sperm morphology
analysis of 13, 15, 1516, 16
G-pattern 2122
N-pattern 2122
P-pattern 2122
reference values 2122
role of, in assisted reproduction 2122
WHO approach on semen thresholds 22
Sperm-omics 115
Sperm–oocyte activation process 114
Sperm preparation 37, 74, 74
principle of 39, 3940
protocol for harvesting motile sperm 40
density gradient sperm separation protocol 41, 4142
direct swim-up technique 42
multitube direct swim-up technique 42
semen collection 40
swim-up protocol 4041
sperm separation from seminal plasma in 3738
density gradient centrifugation 3839
swim-up technique 38
Sperm-rise test 38
Sperm selection technologies 111, 111115
Sperm washing 38, 7475, 97
Sperm zona binding tests (ZBT) 4748, 48
Split pot procedure 53
SSR see Surgical sperm retrieval (SSR)
Stress tolerance test 45
Surgical sperm retrieval (SSR) 13, 67, 8182
considerations in
digestive enzyme, use of 84
DNA damage, levels of 83
fertilization rates and pregnancy outcome 83
fresh or frozen sperm 83
likelihood of obtaining sperm 8283
motility enhancement 84
single or multiple biopsies 83
equipment for 85
European regulatory requirements on 8485
fresh and post-thaw preparation 8687
ICSI procedure 87, 87
medium for 85
preparation for 85
samples, cryopreservation of 86
microepididymal sperm aspiration 81
percutaneous sperm aspiration 81, 85
testicular sperm aspiration 81, 81
testicular sperm extraction 81, 82, 8586
thawing in 86
Tadalafil (Cialis) 69
Testes 1, 2
blood supply to 23
endocrine signals, response to 4
germ cells in, development of 3
nerve supply to 3
spermatozoa, production of 3, 3, 4 (see also Spermatogenesis)
Testicular cancer 57, 58
Testicular dysgenesis syndrome 57
Testicular sperm aspiration 81, 81 see also Surgical sperm retrieval (SSR)
Testicular sperm extraction (TESE) 53, 81, 82 see also Surgical sperm retrieval (SSR)
Testicular stem cells, freezing of 99100
Testosterone 1, 4
Theophylline 112
Tight foreskin 7
Tray agglutination test 52
TUNEL (Terminal deoxynucleotidyl transferase dUTP nick and labeling) assay 48, 49
Unstimulated intrauterine insemination (IUI) 103, 104 see also Insemination program
Ureaplasma urealyticum 58
Urethra 2
Vardenafil (Levitra) 69
Varicocele 3, 7, 60, 61
conclusions and recommendations for 60
and poor semen quality 60
repair of, method of 6061, 61
Vas deferens 1, 2
Vasectomy 51, 53, 69, 81
Viral infections, screening for 71
Vitality test 46
Vitrification 95, 99100
Volume, semen 1011
Wet split procedure 53
World Health Organization (WHO) 6, 1013, 16, 17, 21, 22, 46, 65, 69
Xenotransplantation 99
Y chromosome microdeletion testing 83
Zinner syndrome 11
Zona pellucida (ZP) 5
Chapter Notes

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Basic anatomy and physiologyChapter 1

Fidelis T. Akagbosu
The male sex organs consist of testes, epididymides, ductus deferentes, accessory sex glands, and penis (Figure 1.1). The testes differentiate in the fetus from indifferent gonads after expression of the SRY gene on the short arm of the Y chromosome. Fetal Leydig cells then secrete androgens that induce differentiation of the mesonephric (or Wolffian) duct into the epididymis and ductus deferens and some of the accessory sex glands and the indifferent external genitalia into a penis (Meniru 2004).
The testes are two oval structures that normally lie in the scrotum (Figure 1.2). Caudal migration of testes from the abdomen takes place late in fetal life (around week 25–30). Testicular descent into a cool environment may have evolved to minimize the mutation rate in male germ cells (Setchell & Breed 2006). Each testis measures 4–6 cm in length and has a volume of about 25 mL. Testes are encased by a tough fibrous capsule, the tunica albuginea. This comprises an outer layer of visceral peritoneum made up of mesothelial cells, and inside this there is a layer of fibroblasts, collagen fibers, and bundles interspersed by smooth muscle cells.
Testes produce spermatozoa and testosterone (the male hormone). A mature spermatozoon is shown in Figure 1.3. The spermatozoon carries a copy of the man's genetic makeup, the chromosomes, from the site of production in the testis, through the male and female genital tracts, to the oocyte so that fertilization may occur. The spermatozoon carries this genetic material in the headpiece. The rest of the spermatozoon is made up of the mid-piece, which supplies the energy, and the tail, which propels the sperm forward.
Seminiferous tubules are contained within the testis (Figure 1.4). The seminiferous tubules contain germ cells and somatic Sertoli cells that have essential nutritive and physiological functions essential for the developing germ cells. Contractions of the peritubular myoid cells surrounding the seminiferous tubules are responsible for moving the luminal fluid and spermatozoa out of the seminiferous tubules through the rete and the efferent ducts into the epididymis. The interstitial spaces between the seminiferous tubules contain the blood and lymph vessels, macrophages, and Leydig cells. Both ends of each seminiferous tubule open into tubuli recti and then to the rete testis. In humans, up to six seminiferous tubules can join a single tubulus rectus. The rete testis is linked to the epididymal duct by the efferent ducts (ductuli efferentes). These ducts form a cord that is anatomically differentiated into a proximal (initial) zone, where the individual ducts run roughly parallel to each other, and a distal zone (Setchell & Breed 2006).
The epididymis consists of a single highly convoluted duct that develops from the mesonephric (or Wolffian) duct. It measures 5–6 cm and connects the tubules of the testis to the vas deferens. Sperm transport along the epididymal duct is affected by its tunic of smooth muscle. The vas deferens is 35–45 cm long. It originates in the scrotum and courses upward to the groin. It then enters the body cavity through the inguinal canal and joins the duct of the seminal vesicle on that side to form the ejaculatory duct. Spermatozoa reaching the ejaculatory duct from the vas deferens of each side are ejected from the penis, together with secretions from the accessory sex glands at the time of ejaculation. Table 1.1 shows the location and role of the tubules the sperm pass through in the male reproductive tract.
The accessory sex glands arise in part from the mesonephric or Wolffian duct and in part from the prostatic and penile urethra. Vesicular glands (seminal vesicles) and ampullary glands develop as diverticula from the mesonephric duct. The prostate and bulbourethral (Cowper's gland) glands arise from the proximal and distal urethra, respectively, as compound tubular alveolar secretory glands. The secretion of the accessory sex glands contains various substances (e.g. fructose, citric acid, zinc, and acid phosphatase) that are added to semen at ejaculation. The prostate surrounds the urethra at the neck of the bladder and is the largest accessory sex gland.
zoom view
Figure 1.1: Male sex organs: side view.
The penis is an intromittent organ by which semen is deposited in the female reproductive tract. Man has a vascular penis that contains two corpora cavernosa that are united by a septum and, inferiorly, a single corpus spongiosum that surrounds the urethra. The corpora cavernosa are covered by a tunica albuginea with trabeculae of elastic fibers and smooth muscle passing inward to subdivide the cavernous bodies into endothelial-lined cavities that are continuous with blood vessels. Upon erection, these cavities become filled with blood and the blood vessels extend. The distal ends of the corpora cavernosa are covered by the glans, which is an extension of the corpus spongiosum. Caudally, the corpus spongiosum is enlarged to form the urethral bulb, which is surrounded by a bulbocavernosus muscle, whereas the root of the corpora cavernosa is surrounded by ischiocavernosus muscles.
zoom view
Figure 1.2: Male sex organs: front view showing paired components.
zoom view
Figure 1.3: A mature spermatozoon.
The scrotum is an outpouching of skin. It lacks subcutaneous fat and has abundant sweat glands. Beneath the skin there is a layer of smooth muscle, the tunica dartos that contracts in response to cold and draws the testes up toward the body wall, whereas in a warm environment it relaxes to increase the surface area of the scrotum by up to 20% (Setchell & Breed 2006).
The vascular supply and innervations of the male reproductive system are important because interruption of either the blood supply or the innervation leads to disturbances of reproductive function.
The blood supply to the testis is via the long and convoluted testicular artery. It is surrounded by the multiple veins of the pampiniform plexus. The testicular artery originates from the abdominal aorta. The vascular arrangement of the spermatic cord facilitates a countercurrent heat exchange that cools the descending arterial blood by 2–6°C before its entry into the testis. The countercurrent heat exchange between the arterial and venous blood keeps the testes and epididymides cool.
zoom view
Figure 1.4: Section through the testis showing the organization of the various systems of tubules.
Table 1.1   Location and role of the tubules the sperm pass through in the male reproductive tract
Seminiferous tubules
Thousands arranged in an anastomosing network lined with Sertoli cells
Meiosis, spermatogenesis
Efferent ductules
Lined by ciliated and non-ciliated (absorptive) cells
To move sperm from the seminiferous tubules to the epididymis
Pseudostratified epithelium
Sperm maturation
Vas deferens
Lined by stereocilia
Receives fluid from seminal vesicles
Ejaculatory duct
Collagenous tubes, travel through the prostate
Receives fluid from prostate and bulbourethral glands
Duct that transports semen (and urine) out through the penis
Receives mucal fluid from glands of Littré
In approximately 15% of humans, the veins of the pampiniform plexus dilate to form a varicocele, and the incidence is appreciably higher in men attending infertility clinics. Varicocele is more common on the left side. It is often ligated in an attempt to treat male infertility, but results have been inconclusive (Setchell & Breed 2006).
The blood supply to the epididymis is derived from two sources, with anastomoses in the corpus. The caput is supplied by branches of an epididymal artery and the cauda is supplied by the deferential artery, a branch of the internal iliac or hypogastric artery that runs alongside and also supplies the ductus deferens. Lymphatic vessels drain the whole length of the epididymis and the ductus deferens.
The blood supply to the accessory glands is derived from the internal iliac (hypogastric) artery. The prostatic (superior vesical) artery runs dorsal to the vesicular gland, where it branches to supply the ventral and dorsolateral prostate, the vesicular gland, together with the anterior prostate, with some branches from the inferior vesical artery. The veins from the ventral and dorsolateral prostate drain into a single, large, circular anastomosis around the neck of the bladder.
The arterial supply to the penis is derived from a branch of the hypogastric artery, the internal pudendal artery that divides to form three arteries of the penis: the bulbourethral, dorsal, and cavernosal arteries. Three sets of veins, superficial, intermediate, and deep, drain the blood from the penis. The scrotum is supplied by the external pudendal vessels.
The organs of the male reproductive tract receive a visceral afferent and efferent nerve supply, derived from a group of ganglia near the spinal cord, the celiac, aortic, caudal mesenteric, hypogastric, and pelvic ganglia. The scrotum and external cremaster muscle also receive somatic innervations.
The testis is supplied by the superior and inferior spermatic nerves. If the spinal cord is injured, male infertility may result with decreases in sperm production and motility but no effect on morphology. Contrary to earlier suggestions, these effects do not appear to be related to changes in scrotal temperature or serum gonadotropin levels. The nerve supply to the epididymis and ductus deferens is derived largely from the inferior (caudal) mesenteric ganglion and pelvic plexus via the hypogastric and then the inferior and middle spermatic nerves.
The penis is supplied by sympathetic, parasympathetic, and somatic fibers, which are carried in the dorsal and cavernous nerves. The cavernous nerve runs along the posterolateral aspect of the prostate, it is often damaged during prostatectomy, leading to erectile problems. The scrotum is supplied by branches from the genitofemoral (cranial and caudal inguinal) nerves, the superficial (superior) perineal nerve, and the caudal scrotal nerve. In the scrotal skin, there are thermal receptors that transmit information on scrotal temperature to neurons in the thalamus, hypothalamus, and cortex.
The testes originally lie in the abdomen of the developing male fetus but descend into the scrotum during the later part of pregnancy. Cells that will eventually produce spermatozoa (called primordial germ cells) are deposited in the testes in the early stage of testicular development. These primordial germ cells arise in the yolk sac of the embryo and migrate, between the 4th and 6th week of pregnancy, to the genital ridge that eventually forms the testes. The primordial germ cells develop into spermatogonia and lie dormant until the boy reaches puberty when the spermatogonia resume cell division and further development. The testes do not become depleted of spermatogonia unlike the situation in the female (Meniru 2004).
The various germ cell types, from the immature diploid spermatogonia to mature haploid spermatids, are described on the basis of the morphological changes that occur during maturation (Table 1.2). Spermatogonia undergo a series of mitotic divisions to produce a large number of germ cells available for entry into meiosis. The first and second meiotic divisions yield secondary spermatocytes and haploid round spermatids, respectively. Spermiogenesis is the process by which the round spermatid transforms, without further division, into the specialized elongated spermatid via a series of complex cytodifferentiative steps. Spermiation is the final step of spermatogenesis and involves removal of spermatid cytoplasm to yield the streamlined spermatozoon capable of motility, retraction of the Sertoli cell away from the spermatid, and finally, the release of the mature spermatid into the tubule lumen (O'Donnell et al. 2006; Figure 1.5). There are six stages of spermatogenesis in the human, and it takes approximately 64 days to produce spermatozoa from spermatogonia (Heller & Clermont 1963, Russell et al. 1990).
Male fertility depends on the continuous daily production of millions of spermatozoa. Spermatogenesis involves a coordinated series of mitotic and meiotic divisions, elaborate cytodifferentiative steps, and constantly changing intercellular interactions, all overseen by an extraordinary interplay of autocrine, paracrine, and endocrine factors.
The endocrine regulation of spermatogenesis is accomplished via a classic negative feedback loop (Figure 1.6) involving interactions between the hypothalamus, pituitary, and testis. The production of spermatozoa is dependent on stimulation by the pituitary gonadotropins, luteinizing hormone (LH), and follicle-stimulating hormone (FSH), which are secreted in response to hypothalamic gonadotropin-releasing hormone (GnRH).
zoom view
Figure 1.5: Spermatogenesis from spermatogonia to spermatozoon.
Table 1.2   Chromosomal number changes as the spermatozoa develop from the germ cells
Stage of spermatogenesis
No. of cells
Chromosome number (n)
1 (diploid)
46 (2n)
Primary spermatocyte (preleptotene)
1 (diploid)
72 (4n)
Secondary spermatocyte (meiosis I)
2 (haploid)
46 (2n)
Spermatid (meiosis II)
4 (haploid)
23 (1n)
23 (1n)
zoom view
Figure 1.6: Hormonal control of testicular function.
LH stimulates androgen synthesis by the Leydig cells of the testis, which acts locally to regulate sperm production and feeds back on the hypothalamus and pituitary to affect GnRH and LH production in a self-limiting loop. FSH stimulates Sertoli cells to secrete inhibin B that has a negative feedback effect on the pituitary to limit FSH synthesis (O'Donnell et al. 2006).
An important function of the Sertoli and Leydig cells of the testis is the ability to ‘receive’ endocrine signals from the bloodstream and to transmit these signals in an appropriate manner to the developing germ cells.
Androgens are produced by the Leydig cells and regulate spermatogenesis by binding to intracellular androgen receptors (ARs). Testosterone, or its 5α-reduced metabolite dihydrotestosterone, bind to cytosolic ARs, which subsequently dimerise, translocate to the nucleus, and bind to androgen response elements in the promoters of androgen-responsive genes to modulate gene transcription.
FSH exerts its biological effect on the testis via FSH receptors (FSH-R) present on the plasma membrane of the Sertoli cell. FSH plays a key role in the development of the immature testis, particularly by controlling the size of the Sertoli cell population, which is set early in postnatal life. FSH is the primary endocrine hormone regulating Sertoli cell function and proliferation. FSH acts at multiple sites in the spermatogenic process and is required for quantitatively normal spermatogenesis. The frequent requirement for FSH in the establishment of spermatogenesis in congenitally and completely hypogonadotropic men points to the need for FSH to induce permanent maturational effects on the Sertoli cell/seminiferous epithelium, as during normal puberty (O'Donnell et al. 2006).
The expression of LH receptors is generally accepted to be restricted to the Leydig cells where it mediates LH actions on the Leydig cell number, function, LH-responsiveness, and, importantly, steroidogenesis. There is an absolute requirement for LH and androgens for the initiation and maintenance of spermatogenesis.
In the adult, testosterone maintains the size and function of the male reproductive sex organs and is important for the production of spermatozoa. Testosterone is essential for the initiation and maintenance of spermatogenesis, and due to its local synthesis by the Leydig cells, it has an exceedingly high testicular concentration being 50- to 100-fold greater than in the circulation.5
Testosterone is also essential for the completion of spermiogenesis. The final event of spermiogenesis, spermiation (the release of mature sperm from the Sertoli cell), is impaired by FSH suppression, although this process is also affected by testosterone suppression, suggesting that FSH and testosterone have synergistic roles in this process. It seems that FSH and testosterone act cooperatively by exerting effects at different stages of spermatogenesis and, therefore, acting in collaboration to allow complete germ cell development (O'Donnell et al. 2006).
Both FSH and testosterone have been shown to play important roles in the initiation of spermatogenesis at puberty and are essential for quantitatively normal spermatogenesis in adulthood.
The term hypogonadotropic hypogonadism is applied to a range of clinical disorders due to deficiency of hypothalamic GnRH drive or intrinsic pituitary FSH and LH secretory ability, which feature poor sexual development (if prepubertal in onset), or infertility and androgen deficiency in adulthood.
In terms of spermatogenesis in males congenitally deficient in GnRH, germ cells do not proceed beyond the immature state in which only a few spermatogonia are seen (de Kretser et al. 1968). Acquired gonadotropin deficiency after puberty leads to testicular regression and marked oligospermia (i.e. reduced but detectable numbers of sperm in the ejaculate) or azoospermia (i.e. an absence of spermatozoa from the ejaculate) and may result from disorders of the hypothalamic-pituitary-testicular axis or from treatment.
When gonadotropin depletion is partial, qualitatively normal spermatogenesis may occur with a reduced total sperm output but in sufficient quantity to maintain fertility. When the hormonal depletion is more marked, spermatogenesis fails to progress due to inhibition of several key steps and infertility results (O'Donnell et al. 2006).
The main function of spermatozoa is to fertilize an oocyte to form a zygote. The spermatozoon cell must locate the oocyte, penetrate its protective layers, and then finally fuse its genetic material with the oocyte. For successful fertilization to take place, a spermatozoon must first penetrate various layers surrounding the oocyte to reach its protective glycoprotein coat, the zona pellucida (ZP). This is accomplished by the release of powerful enzymes contained in the acrosome of the spermatozoon head. The release of these enzymes begins the acrosomal process. Once a spermatozoon nears an oocyte, capacitation and hyperactivity occur. The spermatozoon begins to swim more rapidly and forcefully. Hyperactivity is linked to a sudden influx of calcium ions into the tail of the spermatozoon. Once a spermatozoon is capacitated and reaches the oocyte, enzymes are released from the acrosome to dissolve cell junctions and the ZP coat.
The ZP is an extracellular glycoprotein matrix, which surrounds all mammalian oocytes. There are four human zona glycoproteins (ZP1, ZP2, ZP3, and ZP4), which participate at several steps in the fertilization pathway. Recent studies employing recombinant and immunoaffinity purified human zona glycoproteins revealed that in addition to ZP3, capacitated acrosome-intact spermatozoa also bind ZP4. Human ZP2 primarily binds to the acrosome-reacted spermatozoa, supporting its role as secondary sperm receptor. Both human ZP3 and ZP4 induce dose-dependent acrosomal exocytosis in capacitated spermatozoa. In humans, ZP3 and ZP4 are involved in binding of the spermatozoa to the oocyte and subsequent induction of acrosome reaction. The contribution, if any, of human ZP1 during these stages of fertilization remains to be elucidated (Gupta et al. 2009).
ZP3 is the species-specific spermatozoon receptor on the oocyte surface that functions in the initial binding and induction of the spermatozoon acrosomal reaction. Once the spermatozoon has bound to ZP3, the fused section of the membranes opens and the head of the spermatozoon is transferred to the oocyte cytoplasm, followed by entry of the whole spermatozoon into the oocyte.
Problems with spermatozoa production or any of the parameters by which semen is assessed may lead to infertility. There are also specific syndromes that affect male fertility, such as immotile cilia syndrome, an autosomal recessive defect, which causes immotility or poor motility of the cilia of the airways and sperm. Consequently, an oocyte cannot be fertilized and male infertility results. In azoospermia, no spermatozoa are present in the semen. Impairment of sperm transport, such as obstruction of the epididymis or vas deferens and cystic fibrosis, may also cause male infertility.
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