Difference between Omasum and Abomasum


The stomach of ruminants is composed of four compartments, namely- the rumen, reticulum, omasum and the abomasum. Usually, the omasum receives the chewed cud and also absorbs fatty acids. It is the third compartment following the rumen and reticulum. Here, the reticulum contracts and leads to the opening of a sphincter. The opening of the reticule-omasal sphincter allows the fragmented cud to enter the omasum.

The omasum has a canal-like structure (omasum canal) that helps in the transport of food. It is then followed by the inter-laminate recesses that aid in the absorption process. Their surface area is usually large to facilitate the absorption of water, volatile fatty acids, minerals, etc.


It is the fourth or final compartment in the ruminant’s stomach. It helps in enzymatic digestion. This abomasum is lined with glands secreting digestive enzymes and hydrochloric acid. This aids in the acid hydrolysis of dietary proteins as well as microbial proteins. It also secretes a complex set of enzymes called the rennet (chymosin and pepsin). This enzyme is used to separate curd and cheese from milk.

Also Refer: Cellulose Digestion

Difference between Omasum and Abomasum



It is the third chamber of a ruminant’s stomach. It is the fourth or final chamber of a ruminant’s stomach.
Absorption of water and electrolytes, as well as the mechanical digestion of food particles, happen here. Chemical or enzymatic digestion happens here.
Absence of glands. Presence of glands.
It is not similar to a non-ruminant stomach. It slightly functions similar to a non-ruminant stomach.

Explore: Nutrition and Digestion in Grass Eating Animals

Frequently Asked Questions on Difference between Omasum and Abomasum


What is rumination?

Rumination is a part of the digestion process involving the regurgitation of the food and chewing it again. The rechewing is done to finely fragment the plant food matter. This type of digestion is seen in the ruminants or grazing herbivores like goats, cows, deers, etc.


What is a cud?

Cud is the partially digested food that reaches the ruminant’s mouth from its stomach. It is a bolus of regurgitated food from the rumen and reticulum.


What is the role of rumen and reticulum?

The rumen is the first and the largest compartment in a ruminant’s stomach. It is the initial site for the microbial fermentation of the food. The second compartment or reticulum helps in particle separation. Its fluid content helps to segregate the larger particles and the finer ones. The former is sent to the rumen, and the latter is emptied into the omasum.

Adaptation In Animals: Diverse Digestive Systems I Class 6 I Learn With BYJU’S

Also Read: Digestion in Ruminants

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