Reproductive system
David Sturgeon in Introduction to Anatomy and Physiology for Healthcare Students, 2018
Adult testes vary in size and can be measured using an instrument called an orchidometer. This sounds like a terrifying piece of equipment but is in fact a string of 12, numbered, wooden/ plastic beads of increasing size from 1 to 25 ml (facetiously known as the endocrine rosary or worry beads). A normal adult testis measures 12–25 ml and weighs 10–15 g (slightly smaller than a calf’s testicle/rocky mountain oyster discussed in the previous chapter). It is surrounded by a serous membrane called the tunica vaginalis and a dense capsule of connective tissue called the tunica albuginea. The tunica albuginea also extends inwards and repeatedly divides to form hundreds of small compartments called lobules (Figure 14.4). Each lobule contains between two and three tightly wound vessels known as seminiferous tubules (from the Latin for ‘seed carrying’). The outer layer of the seminiferous tubule consists of smooth muscle that is able to contract to move sperm and fluid along the vessel. The inner layer is lined with millions of specialist epithelial cells called sertoli cells that are responsible for sperm production (spermatogenesis). Follicle-stimulating hormone (FSH), secreted by the anterior pituitary gland, encourages primary spermatocytes (diploid cells) to undergo the first division of meiosis to form secondary spermatocytes (haploid cells). The spermatocytes develop into spermatids and eventually become spermatozoa (sperm). Sertoli cells also secrete a hormone called inhibin which exerts negative feedback on the anterior pituitary gland and inhibits secretion of FSH.
Radiation Damage of the Reproductive Organs
Kedar N. Prasad in Handbook of RADIOBIOLOGY, 2020
The processes of the formation of sperm are referred to as spermatogenesis. The highly proliferating spermatogonia line the seminiferous tubules and give rise to primary and secondary spermatocytes, which then form spermatids. The spermatids do not divide. Each spermatid matures into one spermatozoon. On the criterion of cell death, spermatogonia are most radiosensitive, whereas spermatids and spermatozoa are most radioresistant, but the possibility of genetic damage is high for all cellular elements. The interstitial cells that produce male hormone are also highly radioresistant. Therefore, men exposed at a sterilizing dose (500–600 rads) of radiation retain their fertility and produce seminal and prostatic fluid without sperm for a while. After irradiation, the testis becomes smaller and softer, and may become sterile. However, no change in the beard, voice, or social behavior has been observed.
Fertility treatments
Ruth Chambers in Fertility Problems, 2018
These are immature precursors of spermatozoa. They carry the same genetic information as sperm but have not yet finished maturing. Their use is confined to research purposes in the UK and the HFEA has not issued any clinics with a licence to use spermatids in treatment. There is debate about the potential of using round spermatids which are very immature, as opposed to the more mature version, elongated spermatids, in treating patients. It is thought that spermatids may be useful for fertility treatment in the future in men where it proves impossible to retrieve mature sperm for use in ICSI. There is concern about the difficulty of distinguishing between a spermatid and an immature spermatazoon from the testis that has still to complete spermatogenesis and journey through the epididymis11 and that spermatids may inadvertently be used in some micromanipulation treatment processes.
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.
Evaluating the histomorphological and biochemical changes induced by Tributyltin Chloride on pituitary-testicular axis of adult albino rats and the possible ameliorative role of hesperidin
Published in Ultrastructural Pathology, 2023
Sahar F. Shaban, Maha A. Khattab, Samar H. Abd El Hameed, Shaimaa A. Abdelrahman
Sections stained with H&E of the testes in the control group showed that the testicular parenchyma was formed of contiguous seminiferous tubules separated by the interstitium. The seminiferous tubules were surrounded by thin regular basal lamina and lined with stratified germinal epithelium and Sertoli cells. The germinal epithelium was composed of spermatogonia, primary spermatocytes, early and late spermatids. Sertoli cells had large, pale nuclei resting on the basal lamina. Interstitial cells of Leydig appeared between the seminiferous tubules, they were round in shape with vesicular nuclei (Figure 8a). TBT-treated group showed thickened connective tissue capsule with congested blood vessels. The seminiferous tubules appeared markedly distorted with irregular basal lamina and showed marked cell loss indicated by wide separation between germinal epithelial cells. Most cells had darkly stained nuclei (Figures. 8b, c). The Hesperidin-TBT treated group showed nearly normal appearance of the seminiferous tubules with thin regular basal lamina. The germinal epithelium was composed of spermatogonia, primary spermatocytes, early and late spermatids. Sertoli cells appeared with pale nuclei. Interstitial cells of Leydig had rounded vesicular nuclei (Figure 8d). In the recovery group, the seminiferous tubules still showed less cellularity with separation between the germinal epithelial cells which have dark nuclei. The interstitial tissue showed homogenous acidophilic materials and vacuolation (Figure 8e).
The ameliorative effect of Lactobacillus paracasei BEJ01 against FB1 induced spermatogenesis disturbance, testicular oxidative stress and histopathological damage
Published in Toxicology Mechanisms and Methods, 2023
Khawla Ezdini, Jalila Ben Salah-Abbès, Hela Belgacem, Bolanle Ojokoh, Kamel Chaieb, Samir Abbès
The daily sperm production (DSP) was assessed following the research protocol of Kyjovska et al. (2013) with some modifications. Indeed, the right testis was harvested after the sacrifice. Its half was homogenized for 60 s in a saline solution containing 0.9% NaCl and 0.05% Triton X-100. Only spermatids of the 14th and 16th stages were resistant to homogenization. To visualize them, staining with the Trypan blue 0.04% in PBS (1 M) was done for 30 min before counting. The spermatids were counted with a light microscope at ×400 magnification. The total elongated spermatids in the right testis were calculated by multiplication with the right testis weight. DSP was calculated by dividing the total of spermatids counted by 4.84 days that spermatids spent to develop into stages 14–16 in mouse species (Oakberg 1956). Then, DSP was divided by the weight of the testis to determine the number of sperm per gram of testis, which corresponds to the efficiency of sperm production.
Related Knowledge Centers
- Acrosome
- Ploidy
- Protamine
- Spermatocyte
- Spermatozoon
- Spermiogenesis
- Meiosis
- Chromatin
- Gametid
- Mitochondrion