This article is about an anatomical part.

The reticulum is the second chamber in the alimentary canal of a ruminant

Ruminant

A ruminant is a mammal of the order Artiodactyla that digests plant-based food by initially softening it within the animal's first compartment of the stomach, principally through bacterial actions, then regurgitating the semi-digested mass, now known as cud, and chewing it again...

 animal. Anatomically it is considered the smaller half of the reticulorumen

Reticulorumen

The reticulorumen represents the first chamber in the alimentary canal of ruminant animals. It is composed of the rumen and reticulum. The reticulum differs from the rumen with regard to the texture of its lining. The rumen wall is covered in small, finger-like projections called papillae, which...

 along with the rumen

Rumen

The rumen, also known as a paunch, forms the larger part of the reticulorumen, which is the first chamber in the alimentary canal of ruminant animals. It serves as the primary site for microbial fermentation of ingested feed...

. Together these two compartments make up 84% of the volume of the total stomach. The reticulum is located between the rumen

Rumen

The rumen, also known as a paunch, forms the larger part of the reticulorumen, which is the first chamber in the alimentary canal of ruminant animals. It serves as the primary site for microbial fermentation of ingested feed...

 and the omasum

Omasum

The omasum, also known as the bible, the fardel, the manyplies and the psalterium, is the third compartment of the stomach in ruminants...

.

The reticulum is colloquially referred to as the honeycomb. It is also known as the bonnet and as the kings-hood. When cleaned and used for food, it is called "tripe

Tripe

Tripe is a type of edible offal from the stomachs of various farm animals.-Beef tripe:...

".

Heavy or dense feed and foreign objects will settle here. It is the site of Hardware disease

Hardware disease

Hardware disease is a common term for bovine traumatic reticuloperitonitis. It is usually caused by the ingestion of a sharp, metallic object. These pieces of metal settle in the reticulum, and can irritate or penetrate the lining. It is most common in dairy cattle, but is occasionally seen in...

in cattle and because of the proximity to the heart this disease can be life threatening.

Anatomy

The internal mucosa has a honeycomb shape. When looking at the reticulum with ultrasonography it is a crescent shaped structure with a smooth contour. The reticulum is adjacent to the diaphragm, lungs, abomasum, rumen and liver. The heights of the reticular crests and depth of the structures vary across ruminant animal species. Grazing ruminants have higher crests than browsers. However, general reticulum size is fairly constant across ruminants of differing body size and feeding type.

In a mature cow, the reticulum can hold around 5 gallons of liquid. The rumen and reticulum are very close in structure and function and can be considered as one organ. They are separated only by a muscular fold of tissue.

In immature ruminants a reticular groove is formed by the muscular fold of the reticulum. This allows milk to pass by the reticulorumen straight into the omasum.

Role in digestion

The fluid contents of the reticulum play a role in particle separation. This is true both in domestic and wild ruminants. The separation takes place through biphasic contractions. In the first contraction there is sending large particles back into the rumen while the reticulo-omasal orifice allows the passage of finer particles. In the second contraction the reticulum contracts completely so the empty reticulum can refill with contents from the rumen. These contents are then sorted in the next biphasic contraction. The contractions occur in regular intervals. High density particles may settle into the honeycomb structures and can be found at slaughter. It is during the contractions of the reticulum that sharp objects can penetrate the wall and make their way to the heart. Some ruminants, such as goats, also have monophasic contractions in addition to the biphasic contractions.