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==Introduction==

==Introduction==

The ruminant stomach is composed of 4 separate compartments. Food passes first into the [[The Rumen|rumen]], then [[The Reticulum|reticulum]], [[The Omasum|omasum]] and finally into the [[The Abomasum|abomasum]] before entering the [[Duodenum - Anatomy & Physiology|duodenum]]. The first three stomachs are adapted to digest complex carbohydrates with the aid of microorganisms which produce [[Volatile Fatty Acids - Anatomy & Physioogy|volatile fatty acids]]- the major energy source of ruminants. The last stomach, the [[The Abomasum|abomasum]] resembles the simple [[Forestomach - Anatomy & Physiology|monogastric stomach]] in structure and function.

The ruminant stomach is composed of 4 separate compartments. Food passes first into the [[Rumen - Anatomy & Physiology|rumen]], then [[Reticulum - Anatomy & Physiology|reticulum]], [[Omasum - Anatomy & Physiology|omasum]] and finally into the [[Abomasum - Anatomy & Physiology|abomasum]] before entering the [[Duodenum - Anatomy & Physiology|duodenum]]. The first three compartments are adapted to digest complex carbohydrates with the aid of microorganisms which produce [[Volatile Fatty Acids|volatile fatty acids]] - the major energy source of ruminants. The last compartments, the [[Abomasum - Anatomy & Physiology|abomasum]] resembles the simple [[Monogastric Stomach - Anatomy & Physiology|monogastric stomach]] in structure and function.

The microorganisms in the ruminant stomach also synthesis all of the B vitamins, vitamin C and vitamin K. Vitamin synthesis in the rumen is sufficient for growth and maintenance. Only vitamins E, D and A should be provided in the ruminant diet. Under normal conditions, ruminants will not require B vitamins added in the diet. Cobalt is needed for vitamin B12 synthesis and so cobalt should be provided in the diet or vitamin B12 injected directly into the bloodstream. In stress conditions, vitamins B3 (Niacin) and vitamin B1 (Thiamine) may also need to be provided in the diet.

The microorganisms in the ruminant stomach also synthesise all of the B vitamins, vitamin C and vitamin K. Vitamin synthesis in the rumen is sufficient for growth and maintenance. Only vitamins E, D and A should be provided in the ruminant diet. Under normal conditions, ruminants will not require B vitamins added in the diet. Cobalt is needed for vitamin B12 synthesis and so cobalt should be provided in the diet or vitamin B12 injected directly into the bloodstream. In stress conditions, vitamin B3 (Niacin) and vitamin B1 (Thiamine) may also need to be provided in the diet.

The ruminant stomach occupies most of the left hand side of the abdomen. It is a vast structure, holding up to 60 litres in an adult cow. The [[The Rumen|rumen]] holds 80%, [[The Reticulum|reticulum]] 5%, [[The Omasum|omasum]] 8% and [[The Abomasum|abomasum]] 7% in larger ruminants. In smaller ruminants the proportions are slightly different, with the [[The Rumen|rumen]] holding 75%, [[The Reticulum|reticulum]] 8%, [[The Omasum|omasum]] 4% and [[The Abomasum|abomasum]] 13%.

The ruminant stomach occupies most of the left hand side of the abdomen. It is a vast structure, holding up to 60 litres in an adult cow. The rumen holds 80%, reticulum 5%, omasum 8% and abomasum 7% in larger ruminants. In smaller ruminants the proportions are slightly different, with the rumen holding 75%, reticulum 8%, omasum 4% and abomasum 13%.

The different stomachs of the ruminant develop from the foregut spindle in foetal life. During embyogenesis and after birth the [[The Abomasum|abomasum]] is the largest of the stomachs (over half of the weight and capacity of the four stomachs) due to the [[oesophageal groove|Oesophageal Groove]] directing milk from the oesophagus to the [[The Rumen|rumen]] into the [[The Abomasum|abomasum]], bypassing the [[The Reticulum|reticulum]].  

The different compartments of the ruminant stomach develop from the foregut spindle in foetal life. During embryogenesis and after birth the [[Abomasum - Anatomy & Physiology|abomasum]] is the largest of the compartments (over half of the weight and capacity of the four stomachs) due to the [[Oesophageal Groove|oesophageal groove]] directing milk from the oesophagus to the abomasum, bypassing the rumen, reticulum and omasum.

[[The Reticulum]]

In most animals, after swallowing, food leaves the [[Oesophagus - Anatomy & Physiology|oesophagus]] and enters the [[Monogastric Stomach - Anatomy & Physiology|stomach]]. In ruminants, food enters the [[Abomasum - Anatomy & Physiology|abomasum]] after fermentation in the forestomach. The stomach acts as a reservoir in which a semi-solid mass (chyme) is formed from the ingested food before passing into the [[Duodenum - Anatomy & Physiology|duodenum]]. With the exception of water, little absorption occurs in the stomach. Gastric juice is highly acidic, and contains: HCl, produced by the parietal cells, which maintains gastric pH at 2 which denaturing protein. It also contains pepsin, derived from pepsinogen, produced by zymogen cells. The action of HCl facilitates this. Surface epithelial cells and mucous neck cells produce mucus which forms an alkaline sheet over the epithelial surface. This provides protection from the gastric juice. The cells of the mucosa are renewed at different rates. This is an important consideration in the pathogenesis of certain gastric diseases. Surface epithelial cells and mucous neck cells are replaced about every 3 days. Parietal cells and zymogen cells are produced at a slower rate; the parietal cells have a half-life of 23 days.

[[The Abomasum]]

 

 

 

 

 

 

|flashcards = [[:Category:Ruminant Stomach Anatomy & Physiology Flashcards|Ruminant Stomachs Flashcards]]

 

 

[[Category:A&P Done]]