The tubuli seminiferi recti (also known as the tubuli recti, tubulus rectus, or straight seminiferous tubules) is a structure in the testicle

Testicle

The testicle is the male gonad in animals. Like the ovaries to which they are homologous, testes are components of both the reproductive system and the endocrine system...

 connecting the convoluted region of the seminiferous tubule to the rete testis

Rete testis

Rete testis is an anastomosing network of delicate tubules located in the hilum of the testicle that carries sperm from the seminiferous tubules to the vasa efferentia....

, although the tubuli recti has a different appearance distinguishing it from these two structures.

They enter the fibrous tissue of the mediastinum

Mediastinum

The mediastinum is a non-delineated group of structures in the thorax, surrounded by loose connective tissue. It is the central compartment of the thoracic cavity...

, and pass upward and backward, forming, in their ascent, a close net-work of anastomosing tubes which are merely channels in the fibrous stroma

Stroma (animal tissue)

In animal tissue, stroma refers to the connective, supportive framework of a biological cell, tissue, or organ.The stroma in animal tissue is contrasted with the parenchyma.Examples include:* Stroma of iris...

, lined by flattened epithelium

Epithelium

Epithelium is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. Epithelial tissues line the cavities and surfaces of structures throughout the body, and also form many glands. Functions of epithelial cells include secretion, selective...

, and having no proper walls; this constitutes the rete testis

Rete testis

Rete testis is an anastomosing network of delicate tubules located in the hilum of the testicle that carries sperm from the seminiferous tubules to the vasa efferentia....

.