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Slide 1-

Histology of the Male Reproductive System M1 - Endocrine/Reproduction Sequence A. Kent Christensen Department of Cell and Developmental Biology University of Michigan Medical School Winter, 2009
Slide 2-

Male reproductive system Sperm Sperm production in the testis Spermatogenesis Meiosis Spermiogenesis Sertoli cell Leydig cell (source of testosterone) Hormonal regulation of the male system Testosterone Pituitary hormones (LH, FSH) The male reproductive tract Passage of sperm to the site of fertilization
Slide 3-

Sperm (About 65 µm long) Head Nucleus: tightly-packed 23 chromosomes. Acrosome: Flattened sac containing digestive enzymes. Tail Central core is a typical flagellum (9+2=axoneme). Dense fibers. Middle piece: Helically wound mitochondria. Principal piece: Fibrous sheath (for support). End piece: End of flagellum. Plasma membrane. LadyofHats, wikimedia commons
Slide 4-

Sperm, EM drawing Bloom and Fawcett Histology, 11th ed.
Slide 5-

Sperm, EM drawing, detail Principal piece Principal piece Bloom and Fawcett Histology, 11th ed.
Slide 6-

Sperm head, longitudinal EM section, showing nucleus and acrosome Acrosome contains enzymes (hyaluronidase, neuraminidase, acid phosphatase, acrosin), which will be released in the "acrosome reaction" at the time of fertilization. LadyofHats, wikimedia commons
Slide 7-

Middle piece, EM cross section view (9 + 2) Visual atlas of human sperm structure and function for assisted reproductive technology
Slide 8-

Male reproductive organs Elf Sternberg, wikimedia commons
Slide 9-

Testis The testis has about 250 lobules, each containing 1-4 seminiferous tubules. Seminiferous tubule Germ cells: Develop into sperm. Sertoli cells: Somatic cells, support, nutrition, hormone receptors. Boundary layer (flattened fibroblasts). Interstitial tissue Leydig cells produce testosterone (a steroid hormone).
Slide 10-

Diagram of testis and epididymis Testis Gray’s Anatomy, answers
Slide 11-

Testis, low power LM, seminiferous tubules A.K. Christensen
Slide 12-

Seminiferous tubule and interstitial tissue, human testis, LM A.K. Christensen
Slide 13-

Spermatogenesis Development of germ cells into sperm. Stem cells: Spermatogonia With 23 pairs of chromosomes (normal amount of DNA). Meiosis: Primary and secondary spermatocytes Primary spermatocyte: Chromosome pairs fuse, crossing over. Long prophase (about 20 days). First meiotic division, where each daughter cell receives one chromosome from each pair. Secondary spermatocyte: Prompt second meiotic division, which is a normal mitotic division. Spermiogenesis: Spermatids With 23 chromosomes (half of DNA, for fertilization). Remarkable differentiation into sperm.
Slide 14-

Meiosis Primary spermatocyte Secondary spermatocytes Spermatids (Reduction division) Chromosomes fuse (each 2 chromatids), crossing-over (haploid) Source Undetermined
Slide 15-

Steps of spermatogenesis Heller and Clermont, 1964
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Seminiferous tubule, LM A.K. Christensen
Slide 17-

Primary spermatocytes, spermatids, Sertoli cells Young spermatid nucleus Older spermatid head Lumen A.K. Christensen
Slide 18-

Secondary spermatocyte, division figures A.K. Christensen
Slide 19-

Spermiogenesis, diagram Junqueira and Carneiro, 10th ed., 2003, page436, fig. 22-9
Slide 20-

Spermatid, acrosome, flagellum, EM A.K. Christensen
Slide 21-

Sertoli cell Cell trunk extends from basement membrane to lumen. Supports and nourishes germ cells. All germ cells are surrounded by Sertoli processes or lie in Sertoli surface invaginations. Main endocrine target cell in the seminiferous tubule. Testosterone receptors. Follicle stimulating hormone (FSH) receptors. Blood-testis barrier (Sertoli-Sertoli tight junctions). Blocks entrance of extraneous proteins, etc., into seminiferous tubules between Sertoli cells (must go through Sertoli cell). Special fluid inside tubule (high K+) made by Sertoli cell. Possible protection of germ cells from immune system. Sperm first arise at puberty, when immune system already set. Sperm surface antigens may be seen as foreign. Fawcett, Handbook of Physiology,1975
Slide 22-

Blood-testis barrier (= Sertoli-Sertoli junction) (actin) Fawcett, Handbook of Physiology,1975
Slide 23-

Tight junctions of the blood-testis barrier, freeze-fracture, EM Fawcett, Handbook of Physiology,1975
Slide 24-

Leydig cell Source of the male sex hormone testosterone, a steroid hormone synthesized from cholesterol. Testosterone is the main testicular androgen. Testosterone secretion is regulated by pituitary LH. A well-developed smooth endoplasmic reticulum (SER) is the site of most enzymes of testosterone biosynthesis.
Slide 25-

Leydig cells in the interstitial tissue, testis, LM A.K. Christensen
Slide 26-

EM of Leydig cell cytoplasm, showing abundant smooth ER SER A.K. Christensen
Slide 27-

Actions of androgen On Seminiferous tubules Testosterone is the main hormone regulating spermatogenesis. It acts on Sertoli cells, which have androgen receptors. On the male reproductive tract Androgen regulates development and maintenance of most of the tract. Dihydrotestosterone(DHT). On male secondary sexual characteristics, which arise at puberty Muscle tone and strength. Lower voice. Axillary and pubic hair. Beard and dense body hair, acne. Receding hairline and baldness (also genetic).
Slide 28-

Action of testosterone on the male tract, rat Castrate minus testosterone Turner and Bagnara, General Endocrinology, 5th ed, 1971, fig 12-7, p 454
Slide 29-

Pituitary regulation of male reproduction Luteinizing hormone (LH) Regulates androgen secretion by Leydig cells. The androgen then regulates spermatogenesis, the male tract and male secondary sexual characteristics. LH receptors are on the plasma membrane of Leydig cells. Follicle stimulating hormone (FSH) Regulates the establishment of spermatogenesis at puberty. FSH receptors are on the plasma membrane at the basal surface of Sertoli cells. Although Sertoli cells in the mature testis have FSH receptors that probably have some functions, FSH does not appear to be essential for spermatogenesis in the adult testis.
Slide 30-

Testis of a rat from which pituitary removed (= hypophysectomy), LM A.K. Christensen
Slide 31-

Sperm pathway through the male tract Mediastinum of the testis. Straight tubules. Rete testis. Efferent ducts. Passageway from testis to epididymis. There are 15-30 efferent ducts. Epididymis. Head, body, tail. Single long coiled duct (~6 m long). Sperm mature during passage, and are stored in the tail of the epididymis (for ejaculation). Ejaculation Ductus deferens conducts sperm from epididymal tail. Seminal vesicles usually furnish most of seminal fluid. Prostate gland contributes to seminal fluid. Semen passes through prostatic and penile urethra. Ross and Pawlina, 5th ed, 2007, fig 22.4a, pg 732.
Slide 32-

Mediastinum (dense irreg. C.T.), rete testis (channels), LM A.K. Christensen
Slide 33-

Efferent duct, epididymis, LM A.K. Christensen
Slide 34-

Efferent duct (star-shaped lumen) Cilia Smooth muscle A.K. Christensen
Slide 35-

Epididymis (pseudostratified columnar epithelium) Microvilli (“stereocilia”) Basal cell Sperm A.K. Christensen
Slide 36-

The scrotum keeps testis about 2° cooler than rest of body. If not, then testis inactive (= cryptorchidism) Image of cryptorchidism and ectopia removed. Original here: Ciba Collection of Medical Illustrations, by Frank Netter.
Slide 37-

Male reproductive tract Elf Sternberg, wikimedia commons
Slide 38-

Spermatic cord: ductus (vas) deferens, testicular artery, pampiniform plexus of veins, cremaster muscle, LM Ductus deferens Artery Veins Cremaster Countercurrent heat exchange Kirkman slide collection
Slide 39-

Semen Normally about 3.5 ml per ejaculate in humans. Sperm About 100 million sperm per ml. Concentrations lower than about 20 million/ml may cause fertility problems. Seminal fluid Mainly from seminal vesicle (usually about 70%), prostate and epididymis.
Slide 40-

Seminal vesicle, human, low power LM The secretion includes fructose, ascorbic acid, prostaglandins. Kirkman histological slide collection
Slide 41-

Seminal vesicle, LM Smooth muscle Mucosal folds Secretory epithelium From Japanese 35mm histological slide set (Mizoguti), slide 689
Slide 42-

Prostate gland Drawing of glands in a fetal prostate. Compound tubuloalveolar glands, each emptying separately into the prostatic urethra. Below is a cross section of the fetal prostate. Image of fetal prostate glands removed. Original here: Campbell M.F. & Harrison J.H., 1970, Urology, vol. 1, ed. 3, page 141
Slide 43-

Adult prostate gland, cross section, low power LM. There are 30-50 compound tubuloalveolar glands. The secretion is expelled into the semen during ejaculation. The contents include acid phosphatase, citric acid, fibrinolysin, and prostate-specific antigen (PSA). Glands Ejaculatory ducts Urethra Utricle University of Michigan Virtual Slide Collection
Slide 44-

Prostate Gland The glands are organized into three rather indistinct zones: (1) Mucosal (or urethral) glands. (2) The main (or peripheral) glands occupy about 70% of prostate volume. (3) Submucosal (or median) glands are located anteriorly between the mucosal and main glands. Benign prostatic hypertrophy (BPH, nodular hyperplasia) is common in men over 50 years of age. It occurs primarily in the mucosal and submucosal glands, sometimes giving rise to urethral obstruction. Prostatic cancer (carcinoma) is the second most frequent cause of death from cancer in U.S. males. Carcinomas occur primarily in the main (or peripheral) glands. Image of normal human prostate removed. Original here: Martin Dym in Leon Weiss, Cell and Tissue Biology, 6th ed., 1988, Urban & Schwarzenbergy (Baltimore), fig 30-44, page 967.
Slide 45-

Detail of prostate glands, LM Gland Smooth muscle A.K. Christensen
Slide 46-

Prostate gland, concretions (= amyloid bodies), composed of calcified glycoproteins Concretion Gland Smooth muscle Kirkman histological slide collection
Slide 47-

Penis cross section, LM drawing Gray’s Anatomy, wikibooks
Slide 48-

Fertilization Semen is deposited in the female tract. Cervix: Ability of sperm to pass depends on the consistency of cervical mucus. Lumen of uterus and oviducts: Sperm undergo "capacitation," an induced change that will allow sperm to undergo subsequent acrosome reaction. Events in vicinity of ovum (usually in the ampulla of the oviduct): Secretion from the ovum induces sperm to undergo an acrosome reaction, releasing acrosomal hydrolytic enzymes that may facilitate sperm entry through the cumulus and zona pellucida of the ovum. A sperm enters the ovum. Subsequent sperm are excluded. Fusion of the female and male pronuclei yields a nucleus with 23 pairs of chromosomes, the beginning of a new individual.
Slide 49-

Fertilization: acrosome reaction releases hydrolytic enzymes that help sperm reach the surface of the egg LadyofHats, wikimedia commons
Slide 50-

Additional Source Information for more information see: http://open.umich.edu/wiki/CitationPolicy Slide 5: LadyofHats, Wikimedia Commons, http://commons.wikimedia.org/wiki/File:Human_spermatozoa.png Slide 6: Bloom and Fawcett Histology, 11th ed, fig 31-20, p 813. Slide 7: Bloom and Fawcett Histology, 11th ed, fig 31-20, p 813. Slide 8: LadyofHats, Wikimedia Commons, http://commons.wikimedia.org/wiki/File:Complete_diagram_of_a_human_spermatozoa.svg Slide 9: Visual atlas of human sperm structure and function for assisted reproductive technology, fig 3, p 397. Slide 10: Elf Sternberg, Wikimedia Commons, http://commons.wikimedia.org/wiki/File:Male_anatomy.png, CC:BY-SA http://creativecommons.org/ licenses/by-sa/3.0/ Slide 12: Gray’s Anatomy, Answers, http://www.answers.com/topic/efferent-duct Slide 13: A. Kent Christensen Slide 14: A. Kent Christensen Slide 16: Source Undetermined Slide 17: Heller and Clermont, 1964 Slide 18: A. Kent Christensen Slide 19: A. Kent Christensen Slide 20: A. Kent Christensen Slide 21: Junqueira and Carneiro, 10th ed., 2003, page436, fig. 22-9 Slide 22: A. Kent Christensen Slide 23: Fawcett, Handbook of Physiology,1975 Slide 24: Fawcett, Handbook of Physiology, fig 29, 1975 Slide 25: Fawcett, Handbook of Physiology, fig 29, 1975 Slide 27: A. Kent Christensen Slide 28: A. Kent Christensen Slide 30: Turner and Bagnara, General Endocrinology, 5th ed, 1971, fig 12-7, p 454 Slide 32: A. Kent Christensen Slide 33: Ross and Pawlina, 5th ed, 2007, fig 22.4a, pg 732. Slide 34: A. Kent Christensen Slide 35: A. Kent Christensen Slide 36: A. Kent Christensen Slide 37: A. Kent Christensen Slide 39: Elf Sternberg, Wikimedia Commons, http://commons.wikimedia.org/wiki/File:Male_anatomy.png, CC:BY-SA http://creativecommons.org/ licenses/by-sa/3.0/ Slide 40: Kirkman slide collection Slide 42: Kirkman histological slide collection Slide 43: From Japanese 35mm histological slide set (Mizoguti), slide 689
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Slide 45: University of Michigan Virtual Slide Collection Slide 46: Regents of the University of Michigan Slide 47: A. Kent Christensen Slide 48: Kirkman histological slide collection Slide 49: Gray’s Anatomy, Wiki Books, http://en.wikibooks.org/wiki/Human_Physiology/The_male_reproductive_system Slide 51: LadyofHats, Wikimedia Commons, http://commons.wikimedia.org/wiki/File:Acrosome_reaction_diagram.svg