Horse liver (Photo credit onemedicine.tuskegee.edu)
Sorry that I have not posted for a little while, but things have been pretty hectic lately. Today, I will tell you about the functions of a horse liver. The liver plays an important role in digestion. It secretes salty bile to help change the acidity of the food as it enters the gut from the strongly acidic stomach. If bile ever runs low, digestion will be altered. Especially the breaking down of fats. And as a horse has no gall bladder and bile is discharged in response to eating, a horse that is starved for 12-24 hours can accumulate the bile pigments in the blood, giving a false impression of jaundice. The liver also acts as a detoxifier. Poisons absorbed from the gut are removed from the blood by the liver before they can affect the rest of the body. Even naturally produced poisons such as ammonia are converted into safe chemicals that can be excreted. Example: Ammonia is converted into urea for excretion by the kidneys. The liver also manufactures many essential micro-chemicals, such as clotting factors and vitamins. Iron and other essential vitamins and minerals are also stored in the liver until they are required; vitamin and mineral deficiency diseases are a common reflection of liver failure, and when these functional reserves of the liver are exhausted the horse may bleed from the nose, into the gut, or urine. The liver is essential to the horse’s survival. Even though it can look pretty gross.
To see where the liver is located and some more pictures, click here to watch my video.
Cow intestines, (photo credit,www2.ca.uky.edu/)
I’m back! And none the worse for wear. Today I’m here to talk about a very interesting subject, cow intestines. A cow’s intestines are made up of three different organs. The small intestine, the cecum, and the Large intestine. The small intestine measures about 20 times the length of the animal. It is composed of three sections: the duodenum, jejunum, and ileum. The small intestine also receives the secretions of the pancreas and the gallbladder, which aids digestion. Most of the digestive process is completed here, and many nutrients are absorbed through the villi (small finger-like projections) and into the blood and lymphatic systems. The cecum is a large area located at the junction of the small and large intestine where some previously undigested fiber may be broken down. Although the complete function of the cecum has not been established. And the large intestine is the last segment of the tract through which undigested feed passes. Some bacterial digestion of undigested feed occurs, but absorption of water is the primary digestive activity occurring in the large intestine. Isn’t it interesting how long the intestines are? Though I imagine that it takes a lot of work to break down and get nutrients from what a cow eats.
To see more cow intestine, click here to watch my video.
Horse intestine (photo credit, VETERINARY ONLINE)
Now that I’m done with mouths, let’s move on to a “more interesting” subject, Intestines! Namely, the horse intestines. True digestion begins in the small intestine when it receives liquefied feed material from the stomach. With assistance from the enzymes secreted by the pancreas, the small intestine is the primary site for digestion and absorption of sugar and starch (a complex sugar in plants), protein (that has been initially digested in the stomach), and fat. The small intestine is also the site for absorption of fat-soluble vitamins (A, D, E, and K), calcium, and phosphorous. The large intestine in the horse works like a large fermentation vat in which tremendous numbers of bacteria and protozoa live to facilitate further digestion of plant fiber by their production of enzymes that are capable of breaking down this component of the equine diet (the horse itself does not have these enzymes). This fiber breakdown produces substances called “volatile fatty acids” that can then be absorbed and used by the horse for energy. A second important function of the large intestine is water absorption. This function occurs very efficiently such that by the final step in the small colon, the waste material not used by the horse is formed into fecal balls. These are subsequently passed into the rectum for evacuation through the anus. There, wasn’t that fun? I sure had fun writing it. 😉
To see some horse intestines, click here to watch my video.
Horse mouth (royalty free)
For the next few weeks, I’ll be writing about different animal mouths. Starting with the horse mouth. Horses grasp food using a combination of the lips, tongue, and teeth. Horses’ lips are extremely tactile when it comes to consuming feed. Feeds are mixed with saliva in the mouth to make a moist bolus that can be easily swallowed. There are three pairs of glands that produce saliva – the parotid, the submaxillary, and the sublingual. Horse saliva contains bicarbonate, which buffers and protects amino acids in their highly acidic stomach. Saliva also contains small amounts of amylase which assist with carbohydrate digestion. The mouth contains 36 – 40 teeth. Wolf teeth are not included as not all horses have them. The horse’s upper jaw is wider than the bottom jaw to allow for a chewing motion that is quite complex. The chewing action of the horse is a sweeping action which incorporates both lateral, forward, backwards, and vertical motions. This allows the feed to be effectively ground and mixed with saliva to initiate the digestive process. The texture of the feeds will dramatically influence the chewing rate (jaw sweeps) and rate of ingestion. An average horse will generally take 60,000 jaw sweeps per day when grazing. This amount will be dramatically reduced when confined to a stable and large amounts of grain are fed. When horses chew fibrous feeds such as hay or pasture it is a long jaw sweep action. This is why horses continually out on pasture rarely develop sharp edges on their teeth. Grains are consumed in a shorter sweep which does not extend past the outer edge of the teeth. When large amounts of grain are given, horses chewing action will be changed and the teeth will not be worn evenly. Hooks or sharp edges will start to form on the outside edge of the teeth. Conclusively, mouths are essential for digestion and a discussion about the digestive system would not be complete without them.
To see where the “wolf teeth” are positioned and what a horse’s skull looks like, click here to watch my video
Chicken stomach (photo credit nutrenaworld.com)
This week we’ll look at the chicken stomach. Bird stomachs are different from mammal stomachs in many ways. Today we will be looking at the Crop, the Proventriculus, and the Gizzard. The crop is an out-pocketing of the esophagus and is located just outside the body cavity in the neck region. Any swallowed food and water is stored in the crop until it is time to pass it on to the rest of the digestive tract. When the crop is empty, or nearly empty, it sends hunger signals to the brain so that the chicken will eat more. Although salivary glands of the mouth secrete the digestive enzyme amylase, very little digestion actually takes place in the crop, it is simply a temporary storage pouch. The proventriculus (also known as the ‘true stomach’) is the glandular stomach where digestion begins. As with human stomachs, hydrochloric acid and digestive enzymes (like pepsin) are added to the food here. At this point however, the food has not yet been ground up. The term ‘proventriculus’ is used since it comes before the ‘ventriculus’ or gizzard, with ‘pro’ being the Latin term meaning before. And finally, the gizzard. The gizzard, or ventriculus, is a part of the digestive tract unique to birds. It is often referred to as the ‘mechanical stomach’. It is made up of two sets of strong muscles which act as the bird’s teeth. Consumed food and the digestive juices from the salivary glands and the proventriculus pass into the gizzard for grinding, mixing, and mashing, which is aided by the small stones or grit the bird consumes. These stones remain in the gizzard until they become ground into pieces small enough to pass through to the rest of the digestive tract. The stones/grit are weakened by the acidic environment created in the proventriculus and then are ground into tiny pieces by the strong muscles of the gizzard. This is how chickens can eat a lot of hard seeds and not get digestive issues like humans. Ultimately, Chicken stomachs are designed to ingest the bugs and seeds which chickens need to survive. If any part of the stomach did not work correctly, the chicken might die. Which just goes to show how intricate the whole system is.
To see more chicken anatomy, click here to watch my video.