In mammals the olfactory mucous membrane is located in the upper part of the nose, called the nasal roof. In this area the inhaled air passes by free nerve endings that are able to sense various molecules in the air, thus functions our sense of smell. Randomly molecules and particles may have contact with these nerves, and by this means directly reach the olfactory bulb, which is connected to our forebrain. This pathway guides into the brain without the necessity of crossing the blood-brain-barrier.  The nose is located at the very top of our respiratory tract. It has...

Gastro-Intestinal Tract  (c) yodijim / fotolia.com
Our gastro-intestinal tract is highly specialised for the uptake of different materials (food), their digestion, and the delivery of the nutrients via the blood to the organs. There is also the possibility for nanomaterials to cross the gastro-intestinal tract barrier. However, this only relates to a very small amount of nanomaterials that are considered to be unproblematic.  Food and Gastro-Intestinal TractOur body depends on the daily uptake of food and water. In emergencies, we can survive without food for several days to a few weeks but only if sufficient water is...

Lung © Nerthuz / fotolia.com
The air-blood barrier is a structure present in the lungs that controls gas exchange in the lungs by means of pressure and concentration gradients. However, all other foreign material in our breathing air will be inhaled too if it is small enough, such as bacteria, viruses including nanomaterials. With this being a very thin barrier, the chance for nanoparticles to cross and enter the interior of our body is relatively high.  The adult human lung has a huge surface area of around 120 m2 to 140 m2 for gas exchange of oxygen and carbon dioxide. Anatomically it is...

Immune defenses © ag visuell / fotolia.com
Nanoparticles that are present in the body (i.e. after injection) are largely taken up and eliminated by the reticulohistocytic system (RHS). This system represents a network of cells that are distributed throughout the body within its organs. The function of the RHS is the inactivation and elimination of dead cells, bacteria, viruses, and infiltrated small particulates. Nanoparticles also belong to these "infiltrates". The reticulohistocytic system, also named reticuloendothelial system (RES) or mononuclear phagocyte system (MPS) is a network of cells and tissues that are...

[© Gray38.png: User Magnus Manske on en.wikipedia derivative work: Amada44
The placenta is an important tissue barrier that separates the unborn child from the mother. The foetus is totally dependent on proper functioning of the placenta during its development as it is fed and protected by the unique physiology and structural complexity of this organ. As nutrients and oxygen have to penetrate to the foetus, waste and carbon dioxide have to be transported in the other direction. Nanoparticles may cross this barrier and affect the unborn child. The placental barrier is mainly formed by two different cell layers, one from the mother's side and one from the...

Cross-section through the skin © 7activestudio / fotolia.com
The skin is the body's largest organ and protects the body against diseases caused by organisms, toxic chemicals, and mechanical damage. Nanoparticles are neither able to easily penetrate intact skin nor through superficial injuries within the skin. Low level mechanical stresses applied to the skin are buffered by a layer called the stratum corneum. Secretion of ichor and other blood components protect deeper abraded skin sites from harmful impacts. Nanoparticles, however, can be deposited in the hair follicles, and this route is used in medicine for the release of nanoparticle-bound drugs...

Immune system © ag visuell / fotolia
The immune system recognizes both self and non-self-entities. When non-self agents are recognized, like nanoparticles, immune cells decide whether they constitute a danger or not. If the body recognizes non-self and considers it dangerous, the immune system responds with inflammation. In the case of pathogens which induce disease, they are confined to a local site, are destroyed, and if an injury has occurred, wound healing is induced. Some technically produced nanomaterials are suspected to promote inflammation. However, an ability to influence immune responses can be medically useful...

Schematic sketch showing the blood-brain barrier © von Kuebi = Armin Kübelbeck, and for the brain: Patrick J. Lynch [CC-BY-3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons
The blood-brain barrier separates the vascular system from the brain and is formed by endothelial cells which are enclosing the brain capillary blood vessels. Under normal circumstances this barrier is impermeable to nanoparticles. The cellular barrier, which separates the brain from the vascular system, is formed by endothelial cells [1]. Our capillary blood vessels are enclosed with these cells (endothelial cells), that are connected to each other with circumventing tight junctions that abolish all substance transport between the cells. Only very small lipophilic molecules can...

 

Cookies make it easier for us to provide you with our services. With the usage of our services you permit us to use cookies.
Ok