Anatomy of the testes and the epididymis

In this note, we will consider the anatomy of the testis and the epididymis.

Testis

The testis (testis), or testicle is a paired ovoid-shaped organ located inside the scrotum. The production of spermatozoa and male sex hormones occurs in the testis.

Testicles are formed in the abdominal cavity and descend into the scrotum during embryogenesis.

There they are suspended on the spermatic cord (funiculus spermaticus)

The left testicle is usually slightly lower than the right one.

There are two surfaces of the testis:

1. The medial surface (facies medialis)

2. The lateral surface (facies lateralis)

There are also borders of the testis:

1. The anterior border (margo anterior)

2. The posterior border (margo posterior)

And two poles:

1. The superior pole (extremitas superior)

2. The inferior pole (extremitas inferior)

The testis is placed in a capsule, which consists of three layers.

The vascular layer (tunica vasculosa) is the internal layer

The tunica albuginea (tunica albuginea) is the middle layer

The tunica vaginalis (tunica vaginalis), namely its visceral layer, is the external layer

Along the posterior border of the organ there is the epididymis (epididymis)

There is a cavity between the testis and the epididymis called the sinus of the epididymis (sinus epididymidis)

In this area, there is also a thickening of the tunica albuginea, which is called mediastinum (mediastinum testis)

Septa (septula testis) extend from it deep into the parenchyma (parenchyma testis).

They divide the testis into lobules (lobuli testis), each of which contains convoluted seminiferous tubules (tubuli seminiferi contorti).

These tubules are lined with spermatogenic epithelium, in which spermatozoa are produced.

The wall of the convoluted seminiferous tubules contains spermatogenic cells. Between these cells, there are supporting epithelial cells (sustentocytes), or Sertoli cells. These cells, in addition to providing support, also provide protection and secrete substances that regulate spermatogenesis. They will also divide the seminiferous tubule into two parts: basal and adluminal, which form the blood-testis barrier separating spermatogenic cells from the immune system. In addition, each lobule contains Leydig cells that produce testosterone.

Together, spermatogenic cells and sustentocytes form the epithelial spermatogenic layer. Their large number determines the constant production of seminal fluid. This layer is covered with smooth muscle and fibrous cells, which contract and push the germ cells out of the convoluted tubules of the testes.

The convoluted seminiferous tubules turn into straight tubules (tubuli seminiferi recti), and those in turn form the rete testis in the mediastinum (rete testis).

From it, the efferent ductules (ductuli efferentes testis) pass into the epididymis.

Epididymis

Let’s consider the anatomy of the epididymis

It has the following parts:

The head (caput epididymidis)

Head of the epididymis (caput epididymidis)

The body (corpus epididymidis)

Body of the epididymis (corpus epididymidis)

The tail (cauda epididymidis)

Tail of the epididymis (cauda epididymidis)

There is a small depression between the testis and the epididymis called the sinus of the epididymis (sinus epididymidis)

The organ is covered with the same membranes as the testis.

The already mentioned efferent ductules pass into the duct of the epididymis (ductus epididymidis), which begins in the head.

Eventually, the duct of the appendix passes into the ductus deferens / vas deferens (ductus deferens).

The system of tubules of the appendix is a reservoir for spermatozoa, in which they mature. The epididymis is an androgen-dependent secretory organ, which means that its work depends on the amount of testosterone in the blood.

Rudimentary structures

In the testis and epididymis, there are several rudimentary formations, remaining after embryogenesis.

The remainder of Müllerian duct: this is the appendix of the testis (appendix testis)

The remainder of Wolffian duct: this is the appendix of the epididymis (appendix epididymis)

The remainder of the Wolffian body: this is the appendix of the paradidymis (paradidymis)

These rudimentary structures are well expressed in children up to 10 years old, and then gradually reduced.

Blood supply

Arterial blood enters the testicle and epididymis from the testicular artery (branch of the abdominal aorta) and the artery of the ductus deferens (branch of the umbilical artery). And also, partially from the cremasteric artery.

Venous drainage

Venous blood drains through the testicular veins forming the pampiniform plexus.

Lymph drainage

Lymph drains from the testis through the lymphatic vessels as part of the spermatic cord to the lumbar lymph nodes.

Innervation

The testis and epididymis are innervated by the nerves from the testicular plexus.

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