Anatomy and physiology
Suzanne Everett in Handbook of Contraception and Sexual Health, 2020
A vertical septum of subcutaneous tissue divides it into two parts, each containing one testis. There are approximately 500 seminiferous tubules per testis. The tubules are divided by fibrous septae and surrounded by the tunica albuginea. Each tubule is 30–70 cm long. The location of the testes, outside the abdominal cavity, provides a temperature about 3°C below normal body temperature. This lower temperature is necessary for production of viable sperm. Interstitial tissue between the seminiferous tubules contains connective tissue, blood vessels, lymphatics and Leydig cells which produce testosterone. In each testis there are tubules and ducts which form the epididymis, which then leads on to become the vas deferens, which enlarges to become the ampulla. The seminal vesicle joins each vas deferens at the lower end of the ampulla; these tubes then become known as the ejaculatory ducts. The ejaculatory ducts then fuse to the urethra in the prostate gland to become one duct, the prostatic urethra. The prostatic urethra will then carry semen and urine, the bulbourethral glands (Cowper’s gland) join the urethra,which enters the penis. The penis comprises three cylindrical bodies: two dorsal corpora cavernosa and one corpus spongiosum. The urethra ends at the external urethral meatus. The head of the penis is usually covered by prepuce or foreskin which can be removed in circumcision.
Endocrine Disruptors and Male Sexual Dysfunction
Rajesh K. Naz in Endocrine Disruptors, 2004
Before birth, testosterone secretion by the fetal testes is responsible for masculinizing the reproductive tract and external genitalia and for promoting descent of the testes into the scrotum. After birth, testosterone secretion ceases, and the testes and other parts of reproductive system remain small and nonfunctional until puberty (see Figure 11.1). Environmental chemicals acting as antiandrogen can disrupt this normal sexual development during fetal life [6]. At the onset of puberty, the Leydig cells once again start secreting testosterone, and spermatogenesis is initiated in the seminiferous tubules for the first time. Testosterone is responsible for the growth and maturation of the entire male reproductive system. Ongoing testosterone secretion is essential for spermatogenesis and for maintaining a mature male reproductive tract throughout adulthood. Potent hormonal disruptors in the environment can impair normal development of these organs of the male reproductive system and can affect sperm production [7]. Other effects of testosterone include development of libido at puberty; maintenance of adult male sex drive; control secretion of LH by the anterior pituitary via feedback mechanisms, development and maintenance of male secondary sexual characteristics, and general protein anabolic effects including bone growth and induction of aggressive behavior. How environmental toxicants alter these effects in the male is not clear.
The immune system of the genitourinary tract
Phillip D. Smith, Richard S. Blumberg, Thomas T. MacDonald in Principles of Mucosal Immunology, 2020
The human male reproductive system includes the testis, epididymis, vas deferens, seminal vesicles, prostate, and the urethra (Figure 20.1, right). The testis of the male serves the dual function of producing both gametes (sperm) and sex hormones (testosterone). In the testis, androgen synthesis occurs in the Leydig cells, and spermatogenesis takes place in the seminiferous tubules. The two hormones (gonadotropins) produced by the anterior pituitary that regulate testicular function are follicle-stimulating hormone and luteinizing hormone (LH), each controlled by hormones produced in the hypothalamus. Spermatogenesis and androgen synthesis in Leydig cells are regulated by a negative feedback loop involving the hypothalamic-pituitary-gonadal axis. Sperm formed in the seminiferous tubules enter the vas deferens, an androgen-dependent organ that transports sperm into the pelvis. The vas deferens joins the seminal vesicles to form the ejaculatory ducts that enter the prostatic urethra. Just prior to ejaculation, the testes are brought close to the abdomen, and fluid is rapidly transported through the vas deferens to the ejaculatory duct and subsequently into the prostatic urethra, the final pathway for both urine and semen.
Aluminum reproductive toxicity: a summary and interpretation of scientific reports
Published in Critical Reviews in Toxicology, 2020
The testes (singular testis) have two primary functions, to produce sperm and hormones including testosterone. The testes are composed of multiple seminiferous tubules and interstitial tissue, housed within a fibrous covering, the tunica albuginea. During embryonic development within the seminiferous germinal epithelium, Sertoli cells, which surround the developing germ cells, associate with the latter to form seminiferous tubules after birth. The seminiferous tubules are coiled masses that produce sperm cells through spermatogenesis, the maturation of germ cells to haploid spermatozoa. At birth, the seminiferous tubules contain spermatogonial stem cells. During the first round of spermatogenesis, Sertoli cells join to form tight junctions that compartmentalize the seminiferous epithelium into basal and luminal compartments. Spermatogonia, which are in the basal compartment, divide into type A spermatogonia that remain to replenish the precursor cells or type B spermatogonia. The latter, through meiosis in the luminal compartment, become (primary) spermatocytes. These divide to form secondary spermatocytes which meiotically divide to from spermatids, which are initially round. Multinucleated giant cells in the seminiferous tubules are degenerating germ cells. Spermatids become spermatozoa during late spermatogenesis.
Therapeutic effect of adipose-derived mesenchymal stem cells on Cisplatin induced testicular damage in adult male albino rat
Published in Ultrastructural Pathology, 2019
Fatma Y. Meligy, Amal T. Abo Elgheed, Shymaa M. Alghareeb
In Group (III), there was resumption of relatively normal architecture of the seminiferous tubules as present in control group. The testis was surrounded by a regular thin capsule. It is formed of rounded and oval cut sections of seminiferous tubules with loose interstitial tissue in between. The whorled appearance of the mature sperm flagella were seen filling the lumen of some seminiferous tubules (Figure 3g).Each seminiferous tubule was lined by layers of spermatogenic cells. They were separated by interstitial connective tissue containing blood vessel and surrounding interstitial cells (Figure 3h). Spermatogonia were rested on the basement membrane with dark ovoid nuclei, primary spermatocyte presented in more than one row and had rounded large nucleus with different patterns of coiling. While early spermatids were represented by rows of cells having rounded nuclei. Late spermatids were embedded in Sertoli cells cytoplasm with tail protrudes toward the lumen. In between the tubules, the interstitium showed Leydig cells with rounded nuclei and pale acidophilic cytoplasm (Figure 3i).
The effect of melatonin on testis histological changes and spermatogenesis indexes in mice following treatment with dexamethasone
Published in Drug and Chemical Toxicology, 2022
Malek Soleimani Mehranjani, Mina Azizi, Firouzeh Sadeghzadeh
100 round seminiferous tubule cross-sections in each testis tissue were randomly selected under a light microscope. All spermatogenic and Sertoli cells were counted and spermatogenesis indexes including tubule differentiation index (TDI), Spermiogenesis index (SPI), meiotic index (MI) and Sertoli cell index (SCI) were calculated. The tubule differentiation index (TDI) is defined as the percentage of seminiferous tubules containing at least three differentiated germ cells (spermatocyte, round and long spermatid) from the B spermatogonia stage. To evaluate the SPI index, seminiferous tubules containing spermatozoa in their lumen were considered as the tubes with positive spermatogenic index and tubules without spermatozoa in their lumen were considered as the tubes with negative spermatogenic index. To calculate the MI, the number of round spermatid cells and the primary spermatocytes in each lumen were counted, and calculated based on the ratio of round spermatid cells to the primary spermatocytes and the SCI was calculated by dividing the number of the germ cells into the number of the Sertoli cells (Sadeghzadeh et al.2019).
Related Knowledge Centers
- Epithelium
- Sertoli Cell
- Spermatogenesis
- Spermatozoon
- Sustentacular Cell
- Gamete
- Meiosis
- Testicle
- Sex Hormone-Binding Globulin
- Sex Cords