Testes, or testis when singular, is responsible for the production of sperm, which is called spermatogenesis.
The testes also produce sex hormones, mainly testosterone.
The male genital ducts carry spermatozoa and liquid from the seminiferous tubules in the testes all the way to the penis.
The genital ducts can be split into two groups, the excretory genital ducts and intratesticular ducts.
The intratesticular ducts include the straight tubules (or tubuli recti), rete testis, and efferent ductules.
And the excretory gential ducts include the epididymis, ductus (or vas) deferens, and urethra.
This very low power image is a sagittal section of a testis, which also includes the head of the epididymis located posterior and partially superior to the testis.
The epididymis is a single, long convoluted duct where spermatozoa accumulate and continue to mature even further, including the development of motility.
Accessory glands, such as the seminal vesicles and prostate gland, secrete seminal fluid that provides lubrication and nutrients for the spermatozoa.
The seminal fluid is also slightly alkaline, or basic.
This alkalinity helps protect sperm and prolong their life after they’ve been deposited in the acidic environment of the vagina.
Surrounding each testis is a thick capsule of connective tissue, called the tunica albuginea.
The connective tissue extends inward from the posterior side of the testes and separates the seminiferous tubules into about 250 incomplete pyramid-shaped lobes.
Each lobe contains one to four highly-coiled seminiferous tubules.
Now, if we zoom in all the way to 40x magnification, we can see the individual seminiferous tubules, which have a germinal epithelium that’s responsible for spermatogenesis.
In this one image, we can see the various stages of spermatogenesis.
The spermatogonia are the undifferentiated germ cells that are mainly found along the periphery of the germinal epithelium, against the basement membrane.
These cells are round with a large round nuclei and a pale cytoplasm.
As the cell differentiates, it moves towards the central lumen of the tubule.
The stages of differentiation can be identified based on subtle differences in the shape and staining of the nuclei.
The next stage or cell type is the primary spermatocyte.
These cells can be found at various levels between the basement membrane and the lumen, but they can be identified by their bigger cytoplasm and large nuclei that have thin threads or clumps of chromatin around them.
The secondary spermatocytes arise from the primary spermatocytes, but they’re rarely seen in images because of how quickly they divide into two haploid spermatids.
The early spermatids can be identified by their smaller size compared to spermatocytes and their very round nuclei.
They continue to get smaller as they become late spermatids with small pointed nuclei, which is the last stage seen before finally becoming mature spermatozoa.
Throughout the germinal epithelium, sertoli cells are also present, which are large columnar cells with pale, euchromatic nuclei and prominent nucleoli
These cells provide nutrition and mechanical support for the spermatogenic cells.
The sertoli cells also secrete two hormones - inhibin and activin - which provide positive and negative feedback to the pituitary for FSH secretion.
In this image, portions of the seminiferous tubules can be seen, but there are also Leydig cells, which are typically found between the tubules in the interstitial space.
Leydig cells are large, round or polygonal cells with round nuclei and often have an eosinophilic cytoplasm because of the lipid droplets that they typically contain.
Also, in this image, we can see the spindle-shaped nuclei of myoid cells surrounding the seminiferous tubules.