Introduction 

Humans have different stomachs than a cow. Cows have one stomach but it has four distinct compartments made of the rumen, reticulum, omasum, and abomasum.

Rumen 

A rumen can hold up to 50 gallons of food as it begins the digestion process. 

The rumen is the largest and first compartment of the stomach. The food enters the rumen. The unchewed food travels to the first two stomachs, the rumen and the reticulum, where it is stored until later.

Reticulum

A thin tissue (group of cells) divides the reticulum from the rumen. This tissue is there because even though these parts do some things together they also do some functions independently. 

The reticulum is also known as the honey chamber because the tissues are arranged in a way that resembles a honeycomb. This is where heavy or dense feed and metal objects that are eaten by the cow ends up. 

Omasum

The omasum also called the "bible" or the "fardel" or the "manyplies" or the "psalterium" is the third part of the stomach. This is where water is absorbed by the cow and particles of food that are small enough get moved into the abomasum.

Abomasum

The last part is the abomasum known as the true stomach because it has the glands. The abomasum, also called the "mau" or the "rennet-bag" or "reed tripe" is the fourth and final stomach compartment in ruminants. Rennet is a liquid that is produced in the abomasum. Rennet is used by people to make cheese.

Some more important information

  A cow's liver can be called a fatty liver because of the extra amount of fat stored there. Also the cow's stomach is the most important part of the cow's digestive system out of all six parts.

We call cows hoofed animals but the real name is ungulates. When a cow eats, it grabs up grass as it can start to eat in a short time period. The cow has four stomachs and undergoes a special digestive process to break down the tough and coarse food it eats. 

Conclusion

A cow needs all four parts of the stomach to stay alive. The rumen, reticulum, omasum and abomasum all work together to digest and get the nutrients the cow needs from the feed and grasses it eats.

Cows need four stomach parts because when they are grazing on grass, the first time they just swallow it straight down without chewing it. That's why they need the extra stomach parts, because the cow will re-swallow and chew the grass several times in order to break down the food and get the nutrients out of the grass.