Blood-testis barrier
Encyclopedia
The blood–testis barrier (abbreviated as BTB) is a physical barrier between the blood vessel
s and the seminiferous tubules of the animal testes
. The name "blood-testis barrier" is misleading in a sense that it is not a blood-organ barrier sensu strictu, but is formed between Sertoli cell
s of the seminiferous tubule and as such isolates the further developed stages of germ cells from the blood. A more correct term is the "Sertoli cell barrier" (SCB).
The barrier is formed by tight jucntions, adherens junctions and gap junctions between the Sertoli cell
s, which are sustentacular cell
s (supporting cells) of the seminiferous tubules
, and divides the seminiferous tubule in a basal compartment (outer side of the tubule, in contact with blood and lymph) and an adluminal compartment (inner side of the tubule, isolated from blood and lymph).
The presence of the SCB allows Sertoli cell to control the adluminal environment in which germ cells (spermatocytes, spermatids and sperm) develop by influencing the chemical composition of the luminal fluid.
The barrier also prevents passage of cytotoxic
agents (bodies or substances that are toxic
to cell
s) into the seminiferous tubules.
. When the blood–testes barrier is breached, and sperm enters the bloodstream, the immune system
mounts an autoimmune response against the sperm. The anti-sperm antibodies
generated by the immune system can bind to various antigen
ic sites on the surface of the sperm. If they bind to the head, the sperm may be less able to fertilize an egg
, and if they bind to the tail, the motility of the sperm can be reduced.
Blood vessel
The blood vessels are the part of the circulatory system that transports blood throughout the body. There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and...
s and the seminiferous tubules of the animal testes
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...
. The name "blood-testis barrier" is misleading in a sense that it is not a blood-organ barrier sensu strictu, but is formed between Sertoli cell
Sertoli cell
A Sertoli cell is a 'nurse' cell of the testes that is part of a seminiferous tubule.It is activated by follicle-stimulating hormone and has FSH-receptor on its membranes.-Functions:...
s of the seminiferous tubule and as such isolates the further developed stages of germ cells from the blood. A more correct term is the "Sertoli cell barrier" (SCB).
The barrier is formed by tight jucntions, adherens junctions and gap junctions between the Sertoli cell
Sertoli cell
A Sertoli cell is a 'nurse' cell of the testes that is part of a seminiferous tubule.It is activated by follicle-stimulating hormone and has FSH-receptor on its membranes.-Functions:...
s, which are sustentacular cell
Sustentacular cell
A sustentacular cell is a type of cell primarily associated with structural support.One type of sustentacular cell is the Sertoli cell, in the testicle...
s (supporting cells) of the seminiferous tubules
Seminiferous tubules
Seminiferous tubules are located in the testes, and are the specific location of meiosis, and the subsequent creation of gametes, namely spermatozoa....
, and divides the seminiferous tubule in a basal compartment (outer side of the tubule, in contact with blood and lymph) and an adluminal compartment (inner side of the tubule, isolated from blood and lymph).
The presence of the SCB allows Sertoli cell to control the adluminal environment in which germ cells (spermatocytes, spermatids and sperm) develop by influencing the chemical composition of the luminal fluid.
The barrier also prevents passage of cytotoxic
Cytotoxicity
Cytotoxicity is the quality of being toxic to cells. Examples of toxic agents are a chemical substance, an immune cell or some types of venom .-Cell physiology:...
agents (bodies or substances that are toxic
Toxicity
Toxicity is the degree to which a substance can damage a living or non-living organisms. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell or an organ , such as the liver...
to cell
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
s) into the seminiferous tubules.
Auto-immune response
The blood–testes barrier can be damaged by trauma to the testes (including torsion or impact), by surgery or as a result of vasectomyVasectomy
Vasectomy is a surgical procedure for male sterilization and/or permanent birth control. During the procedure, the vasa deferentia of a man are severed, and then tied/sealed in a manner such to prevent sperm from entering into the seminal stream...
. When the blood–testes barrier is breached, and sperm enters the bloodstream, the immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
mounts an autoimmune response against the sperm. The anti-sperm antibodies
Antibody
An antibody, also known as an immunoglobulin, is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, termed an antigen...
generated by the immune system can bind to various antigen
Antigen
An antigen is a foreign molecule that, when introduced into the body, triggers the production of an antibody by the immune system. The immune system will then kill or neutralize the antigen that is recognized as a foreign and potentially harmful invader. These invaders can be molecules such as...
ic sites on the surface of the sperm. If they bind to the head, the sperm may be less able to fertilize an egg
Ovum
An ovum is a haploid female reproductive cell or gamete. Both animals and embryophytes have ova. The term ovule is used for the young ovum of an animal, as well as the plant structure that carries the female gametophyte and egg cell and develops into a seed after fertilization...
, and if they bind to the tail, the motility of the sperm can be reduced.