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Home , Efferent ducts, Rete testis, Seminiferous tubule, Spermatid, Spermatocyte, Spermatocytogenesis

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

To learn what structures and hormonal regulation facilitate the male to produce an exocrine secretion (the ) and an endocrine secretion ().

Outline

History Spermatozoon Sertoli and Leydig cells Hormonal control Epididymal and accessory glans characteristics and functions Fertile ejaculate First scientific endocrine study involved the testes of roosters studying the observable effects of hen testosterone on the secondary structures.

Transplanted tested maintained wattles and comb growth in castrated roosters. Functions of Male Reproductive System are to:

- produce, maintain, and transport mature spermatozoa (the male ), - produce nutritive and protective fluid (), and - discharge the spermatozoa-containing semen within the reproductive tract during .

Primate Mouse spermatozoon

Rat Bull

Human Details of spermatozoa

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

Middle piece with mitochondria Human Human

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

Leydig cells

Seminiferous Slide 165 tubules Human testicular capsule

Vein

Artery

Mesothelium

Slide 165 34455 Human testis toluidine blue Seminiferous 19680 tubules

Leydig cells Seminiferous

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

Germ cells

467

Two kinds of cells present in the seminiferous epithelium: Sertoli cells and germ cells: Sertoli cells nurse germ development. Nuclei of Sertoli cells 19680 Horse Seminiferous Tubules Seminiferous tubules are composed of seminiferous epithelium and boundary cells:

Myoid Cells

Sertoli Cells

Germ Cells Spermatogonia, , Human Seminiferous Tubules composed of:

Myoid cells

Sertoli cells

Germ cells Spermatogonia, Spermatocytes, Human Spermatids

Meiotic activity

UT165 larger secondary nuclei and smaller Golgi phase nuclei human testis metaphase figures in #92 secondary spermatocytes

Pachytene primary spermatocytes

Letotene primary spermatocytes

To find secondary spermatocytes, one needs to find a 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.

Early and late spermatids Leydig (interstitial) Slide 92: Testis cells

Tunica albuginea

Residual bodies Basement membrane

Myoid cell

Sertoli cells

Seminiferous tubules 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

Meiosis

Spermiogenesis 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. Spermatocytogenesis

Horse Meiosis (only in spermatogenesis and )

Exchange of genetic material in homologous (leptotene, zygotene, pachytene, and diplotene steps of development)

Produces haploid condition of gametes Meiosis Exchange Of Genetic Material

Secondary Spermatocytes Meiosis Produces Haploid Condition of Gametes 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)

Flagellar cannel Shedding excess Manchette Golgi phase

Cap phase

Elongation phase

Maturation phase Maturation phase Spermiogenesis

human Horse

Manchette Golgi

Developing

Spermatid nucleus Cis face

Golgi

Black acid phosphatase precipitates in Acrosomal the developing cap Cytosol Transport vesicles acrosome Trans face

Nucleus Golgi Spermatid showing the developing acrosome over its nucleus. Acid phosphatase enzymes (black precipitates) first appear in the trans face of the and are transferred to the Acrosomic vesicle developing acrosome via transport vesicles. Testis of a spermatid Manchette is a transient Flagellar as it is not found in spermatozoa cannel Flagellar cannel When the annulus migrates to end of middle piece, it removes the cell membrane of the flagellar cannel from the surface of the developing in the middle piece region and allows mitochondria access to that portion of developing tail. Annulus Mitochondria are found only in the Flagellar middle piece on spermatozoa as that cannel is the only region with access.

Residual bodies Spermatids and Spermatozoa Residual bodies Sertoli Cells • Provide support and nutrition to developing germ cells

• Release spermatids as sperm

• Phagocytize degenerating germ cells and residual bodies

• Secrete: – binding – Calmodulin – Plasminogen activator – Inhibin

• Blood testis barrier Human – infertile

Occluding junctions between Sertoli cells

Blood-testis occluding junctions between sertoli cells in seminiferous tubules

Human spermatogenesis: path followed by given cell

Basal compartment with spermatocytogenesis Blood Testis Barrier Adluminal compartment with meiosis and spermiogenesis 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 Intercellular Bridges

Occluding junctions between Sertoli cells are still above but now appear below the zygotene spermatocytes 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 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 Testicular interstitium human Primary nucleus spermatocytes 19680

Fibroblasts, Myoid cells droplets in Sertoli cells Artery

Mitotic figures in dividing spermatogonia to produce Spermatogonia primary spermatocytes

Nerve , Leydig cells 19680 Leydig cells Myoid cells. Capillaries

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

Nerve

19670

Odd : What appears to be Leydig cells inside the nerve in the human testis.

Horse Hormonal Control of Spermatogenesis

Hormone Cell Stimulated In Spermatogenesis

FSH Sertoli Cells Spermatocytogenesis Spermiation

LH Leydig Cells Meiosis (Testosterone)

Deleterious Influences on Spermatogenesis

• Heat

• Irradiation

• Chemicals

• Aging

Extragenital Components of the Male Reproductive System

Excretory Ducts

Composition (, , , Ductus Deferens, Ejaculatory Ducts, )

19709 Human testis: junction of and rete testis for sperm to exit (toluidine blue)

Junction of seminiferous tubule and rete testis tubule

Region of the

Rete testis 467 Testis and epididymis – efferent duct and epididymis

Profiles of the epididymal duct

Efferent Seminiferous ducts tubules

Rete testis tubules True cilia on their apical Efferent ducts surface help move Efferent ducts have a characteristic scalloped sperm through the duct. luminal profile due to alternating groups of high and low columnar cells in the lining epithelium

Lumen 199

Horse efferent duct

19673 True ciliated cells (efferent duct) and stereociliated cells (epididymis, with sperm in lumen) of psudostratified columnar epithelium (toluidine blue)

19678 Efferent duct

Epididymis Epididymis Head Efferent duct

19673 Efferent duct 199 Extremely long (30µm), branching microvilli (stereocilia) projects from the apical surface of these cells Stereocilia

Head Tail of epididymis Smooth muscle layer is thicker in more distal regions of epididymis 467 19716 Human

Human DUCTUS DEFERENS IN THE

Psudostratified columnar epithelium, but lower in height

Epithelium and its lamina propria, showing longitudinal folds into Blood vessels and ductus deferens the lumen

Nerve 196 Smooth muscle, extremely thick layers 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 speed is 800 mm/second Spermatic cord

Testis

Spermatic cord 38

Human testis and epididymis 19678

Epididymal Spermatozoan Maturation

Fertility

Nature of plasma membrane Mitochondrial structural stability

Chromatin stability

168 Seminal vesicle, monkey

Branched network produces a "honeycomb" appearance

Prostate is a firm mass of collagenous and smooth muscle that is invaded by numerous glandular outpocketings of the urethra

Lumen of gland 271 Note the abundance of smooth muscle in its interstitium. Prostate

169

BULBOURETHRAL GLAND

Two main function of male reproductive system are to:

Produce male gametes

Deliver male gametes

Penis – transitional epithelium and surrounding spongy cavernous of penal urethra Cavernous erectile tissue

Nerve Smooth muscle

Transitional epithelium Spongy cavernous

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 277 fluids are traveling down its length when the is rigid. Variations in the Microvasculature

Common Arteriole  Capillary  Venule

Shunts Arteriole  Metarteriole  Venule

Artery  Av Shunt  Vein

Fig. Mechanism of 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.

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. Accessory Glands - Composition and Secretion

Accessory glands Secretion Fructose fibrinogen

Prostate Citrate fibrinolysin

Bulbourethral gland Mucus-like lubricant

Glands of Littré Mucus 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 CHARACTERISTICS OF FERTILE HUMAN EJACULATES

GOOD VISCOSITY (CLOT THEN DISPERSE) about 3 ml in volume

Many illustrations in these VIBS Histology YouTube videos were modified from the following books and sources: Many thanks to original sources!

Bruce Alberts, et al. 1983. Molecular 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. Nature (http://www.nature.com), Vol. 414:88,2001. A.L. Mescher 2013 Junqueira’s Basis Histology text and atlas, 13th ed. McGraw Internet images and videos on biological presentations During the hour of this lecture the average male produced 6.6 million spermatozoa

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 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.

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 Stages of the spermatogenic cycle in humans Human spermatogenesis: path followed through spermatocytogenesis, meiosis, and spermiogenesis as a given cell travels through five spermatogenic cycles

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. 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)

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

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 Wave of the seminiferous epithelium (not in humans)

"The wave is in space what the cycle is in time."

Horse rat