Cow small intestine

Cow small intestine extends from the abomasum compartment of the stomach to the ileo-cecal junction. It is one of the major parts of the gastrointestinal tract of the cow’s digestive system.

Here, I will describe the anatomy of the cow’s small intestine with the hand-drawing diagrams and real pictures.

Quick answer: Cow small intestine continues the gastrointestinal tract caudally from the abomasum and divides into three parts: duodenum, jejunum, and ileum.

I will help you to learn and identify these 3 parts of the cow’s small intestine practically.

Cow small intestine

Figure 1 presents the hand-drawing diagram of the different parts of the two types of intestines along with some associated organs. It also highlights the three different parts of the small intestine with some exceptional features.

Here, the figure clearly states that our identified small intestine has the following features –

Location/extension: The specific tube-like structure after the stomach is identified as the small intestine. Thus, it has a specific start point and a specific end point.

Topographic relationship: The small intestine have the direct or indirect relationship with the various visceral organs of the cow’s abdomen. You will find the relationship of the different parts of the cow’s small intestine with the stomach, liver, pancreas, peritoneum, cecum, and colon.

Parts/segments with special features: As there are three parts (Figure 2) in the small intestine named duodenum, jejunum, and ileum have unique anatomical features. These unique anatomical features make them identifiable from the live sample and help to differentiate them from each other.

Here, Figure 2 highlights only the cow’s duodenum, jejunum, and ileum parts from its small intestine with real pictures.

Thus, while describing the anatomy of the cow’s small intestine, you might mention the above features with diagrams clearly. However, you might also describe the anatomy of the cow’s duodenum, jejunum, and ileum separately.

What is the small intestine of a cow?

So, from the Figure 1 and 2, you will easily understand the cow’s small intestine. It is the part of the gastrointestinal tract that starts from the pylorus of the abomasum and terminates at the iliocecal orifice of the large intestine.

In a averaged sized cow, it is about 40 meters/ 140 feet. However, the average diameter of the small intestine is about 5 to 6 centimeters (cm)/ 2 inches.

But, in small ruminants like the sheep and goat, the average length of the small intestine is about 20 meters. Again, the diameter is less than that of the large ruminant and measures about 2 to 3 centimeters.

Small vs large intestine: The length of the cow’s large intestine is about 12 meters, which is less than the length of the small intestine (Figure 3). Thus, you may have the question – why is the first segment of the intestine termed the small intestine?

Well, based on the diameter, the small and large intestines are named. Here, the diameter of the first segment of the intestine is less (5/6 cm) than the second main segment (6/7cm).

Overview of the parts of the cow’s small intestine

Figure 4 presents an overview of the three different parts of the cow’s small intestine. This might help you to memorize the features of the cow’s duodenum, jejunum, and ileum.

The strategies shown in the above figure also help you to present the anatomy of these structures perfectly in your examination.

• Duodenum: It is the first part of the small intestine and has different special features, such as the S-shaped curved and others. You will also find the opening of the bile and pancreatic ducts on the different parts of the cow’s duodenum what I will discuss in the description section.
• Jejunum: It is the longest part of the small intestine and consists of a huge number of coils attached to the border of the mesentary. Here, these coils are constricted and dilated and form the U-shaped tubular loops.
• Ileum: It is a thick, tube-like part and is considered the terminal part of the small intestine.

Here, Figure 5 highlights the special features of the cow’s duodenum, jejunum, and ileum. I made this figure with the combination of the cow’s hand-drawing diagram and real pictures.

Now, I will describe every single part of the cow’s small intestine in detail with the hand-drawing diagrams.

Cow duodenum anatomy

The duodenum is the first fixed part of the cow’s small intestine. It is about 1 meter/3 to 4 feet long in the cow.

The cow’s duodenum begins at the pylorus of the abomasum at the level of the ventral end of the tenth rib. Now, it passes dorsally and cranially to the visceral surface of the liver.

Here, it forms the S-shaped curved which is termed the ansa sigmoidea/sigmoid flexure. Figure 6 presents the ansa sigmoidea of the cow’s duodenum along with its other caudal flexures and parts.

Now, the sigmoid flexure turns back and continues caudally at the level of the tuber coxae of the cow’s hip/pelvic bone. This portion of the cow’s duodenum is known as the descending part.

The descending part of the cow’s duodenum continues and forms the caudal flexure. It passes from the right to the left side around the caudal mesenteric artery.

However, the caudal flexure continues as the ascending part of the duodenum. It runs cranially on the left side of the cranial mesentery artery.

However, it terminates at the duodeno-jejunal flexure and continues with the jejunum part. Thus, in the cow’s duodenum, you will find 4 different segments that are also shown in Table 1 –

Segments of the cow’s duodenum	Extension of the segment
First: Ansa sigmoidea	S-shaped curved after the abomasum
Second: Descending part	Continuation of the ansa sigmoidea on the right side
Third: Caudal flexure	Cranial turning area of the descending part
Fourth: Ascending part	Continuation of the caudal flexure on the right slide

Attachments of the cow’s duodenum with various organs

You will find the following attachments of the cow’s duodenum with various organs –

• Cranial part of the duodenum: It is attached to the cow’s liver by the lesser omentum.
• The descending and caudal flexure parts: These two parts of the duodenum are attached dorsally to the mesoduodenum (Figure 7). However, they are also attached ventrally to the superficial wall of the omental bursa.
• Ascending part: This part of the duodenum is connected to the cow’s descending colon caudally by the duodenocolic ligament.

What is the mesoduodenum in a cow?

Figure 7 shows that the various parts of the cow’s duodenum are attached to the pancreas, colon, and cecum by a short peritoneal fold. This short fold of the peritoneum/mesenteries is known as the mesoduodenum.

Thus, the mesoduodenum in a cow is very short and remains fixed with the duodenum.

What are the mesenteries in the cow’s small intestine?

The mesenteries are the peritoneal folds that specially covers the small and large intestines of the cow. Figure 8 presents the mesenteries of the cow’s small intestine.

Here, the mesenteries suspend the small intestine from the dorsal body wall. They are named according to the part of the small intestine they support.

Thus, you will find the following mesenteries in the small intestine of a cow –

• Mesoduodenum: Mesentery attaches to the parts of the cow’s duodenum,
• Mesojejunum: Mesentery attaches to the part of the cow’s jejunum, and
• Mesoileum: The mesentery attaches to the part of the cow’s ileum.

Here, the mesoduodenum is short, whereas the mesojejunum and mesoileum are long and fanlike. The mesojejunum and mesoileum are often collectively known as the great mesentery.

Here, the great mesentery has a narrow stalk by which it attaches to the body wall. However, the vessels, nerves, and lymphatics also communicate with the intestine through the narrow stalk. The narrow portion of the great mesentery is also called the root of the mesentery.

The length of the cow’s great mesentery permits considerable mobility of the intestinal masses.

Opening site for the bile and pancreatic ducts on the cow’s duodenum

Figure 9 highlights the opening sites for the bile and pancreatic ducts on the various parts of the cow’s duodenum.

So, where do the bile ducts open on the cow’s duodenum? Well, from the figure, you may easily understand the opening site for the bile duct on the duodenum.

Here, the bile duct opens into the second bend of the S-shaped curve of the duodenum. It is about 60 centimeters away from the pyloric end of the cow’s duodenum.

Where do the pancreatic ducts open on the cow’s duodenum? Well, the figure also clearly shows the opening site of the cow’s pancreatic duct on the duodenum.

Here, the cow’s pancreatic duct opens into the descending part of the duodenum. It is about 30 centimeters caudal from the opening of the bile duct.

Cow jejunum anatomy

Figure 10 presents the hand-drawing diagram of the cow’s jejunum. The length, appearance, and arrangement of the cow’s jejunum are totally different from the duodenum part of the small intestine.

Here, the jejunum is the continuation of the cow’s duodenum caudally. It is arranged in the form of several close coils that are attached to the border of the mesentery.

Several coils of the cow’s jejunum form the U-shaped series of loops on the extended part of the mesentery.

Location: The cow’s jejunum chiefly lies on the right side of the rumen and right abdominal wall below the large intestine. However, you will find the following boundaries of the cow’s jejunum by various organs –

• Medially: by the right surface of the rumen,
• Laterally: by the abdominal wall,
• Dorsally: by the large intestine, and
• Cranially: by the omasum and abomasum.

The cow’s jejunum can be exposed by removing the caudal fold of the omentum cranially. However, you can display the cow’s duodenum by straightening it after removing all attachments.

Vessels of the cow’s jejunum: The vessels of the cow’s jejunum are arranged in a few layers of arches in the mesentery/mesojejunum. Here, the straight vessels connect the loops of the jejunum with the convexity of the vascular arches.

Here, Figure 11 presents the hand-drawing diagram of the arrangement of the jejunum’s vessels. It presents the major vessels, straight vessels, vascular arches, and the loop of the cow’s jejunum.

Cow ileum anatomy

Figure 12 highlights the cow’s ileum parts from its small intestine. It is the terminal part of the small intestine of a cow. (Cow ileum anatomy)

Here, the ileum part of the cow’s small intestine is a straight tube and measures about 1 meter in length. It passes the edge of the mesentery and runs cranially between the cecum and colon of the large intestine.

Finally, it terminates on the medial surface of the cecum on the cecocolic junction.

How to identify the cow’s ileum: It is the small, straight part that can be distinguished from the jejunum by a fold of mesentery between it and the cecum. This is the ileocecal fold, which is found on the side of the intestine opposite the attachment of the mesentery.

Structure of the cow small intestine

The wall of the cow’s small intestine consists of serous, muscularis, submucosa, and mucosa coats (Figure 13) –

• Serous coat: It is the outer coat of the cow’s small intestine.
• Muscular coat: It is the coat medial to the serous coat.
• Submucosal coat: It is medial to the muscular coat.
• Mucosal coat: This is the innermost coat of the cow’s small intestine.

Here, Figure 13 presents the common features of the different coats of the cow’s small intestine.

The outer serous coat of the cow’s small intestine consists of loose connective tissue with simple squamous epithelium. Again, the muscular coat of the small intestine possesses the inner circular muscle and outer longitudinal muscle coats.

However, the submucosa coat of the cow’s small intestine consists of vessels, nerves, glands, and solitary and aggregated lymph nodes. However, the appearance and name of the glands and lymph nodes are different in various sections of the cow’s small intestine.

These differences among the different segments are discussed in the histology section of the cow’s small intestine. However, the submucosa consists of Brunner’s glands in the first few meters of the cow’s small intestine.

The free surface of the mucous coat of the cow’s small intestine presents permanent folds and villi. These villi are of different shapes in the various segments of the cow’s small intestine.

Glands and lymphatic nodules in the small intestine

The intestinal glands are present throughout the segments of the cow’s small intestine. However, you will find the lymphatic tissue occurs in the form of distinct nodules.

They can appear as either a scattered solitary structure or in groups. When the lymphatic tissues occur in a group in the small intestine, then it is termed the Peyer’s patches.

The patches are very long in the cow and consist of eighteen to thirty in number. However, close to the ilio-cecal junction, the patches are very long.

FAQ’s on the cow’s small intestine

Conclusion

So, the small intestine of a cow has three distinct parts: duodenum, jejunum, and ileum. Here, the jejunum is the longest part, and the ileum is the shortest part of the small intestine.

The anatomical features of the duodenum, part of the cow’s small intestine, are unique compared to other parts.

References

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