Well today was my first anatomy credit test of the semester and covered the stuff I learnt about the animal mouth last week. We’ve a different lecturer this semester so there was a change in the exam structure with two of us being examined at the same time instead of the individual exams we had last semester. I’m still not sure which method I prefer more however today I did finish with an A!
We then went on to look at the two different types of stomach (complex and simple) and their differences across the animal species. Basically ruminants which eat grass have a specialised system for digesting the cellulose in the cell walls which the simple stomach cannot handle. This consists of a complex stomach with four different chambers including the Rumen, Reticulum, Omasum and Abomasum (for a description of the structures check out Monday’s diary for histology of the stomach). The simple stomach has just a single compartment which secretes enzymes and digestive juices to help breakdown the food that is eaten. Though I had looked at the complex stomach before in my previous degree it was fascinating to go into so much more depth looking at the different areas, and how it changes with age.
In young ruminant animals for example there is a gastric groove called the sulcus ventriculi which extends from the entrance through the reticulum, omasum and nearly to end of the abomasum and is formed from muscular lips. In unweaned animals this groove often closes to form a tube allowing the mothers milk to bypass the sections of the stomach responsible for digesting plant matter and straight into the abomasum where it is absorbed into the body. As the animal matures the tube flattens out until it is no longer used.
This afternoon I started horse riding which is an optional module available to the post bachelor students here at UVM Kosice. The name is a little deceptive as it is in fact a complete equine 101 module covering basic horse care, rehabilitation, handing and off course a little riding once the weather gets a bit better. The lecture today covered the different types of rehabilitation that are used for horses. Check out the road back to dorms with the snow we’ve had this afternoon…
Start of my second week of my second semester, last week vanished in a blur and this week I have tried to plan my time better to get a lot more of the research for my Emergency First Aid for Animals book completed.
Now I think I have previously said before how the stomach with ruminants is divided into four different compartments; the rumen and reticulum, omasum and the abomasum. Each of these has a specific role to play in digestion and specific structure to match. This is known as the complex stomach and the esophagus enters this between the reticulum and rumen. The rumen is the largest stomach compartment and is connected to the reticulum with a large opening allowing food to be passed back and forth between the two. Remembering that ruminants eat plant matter the rumen is where fermentation takes place with a large amount of bacteria and protozoa act on the contents breaking it down. The surface of this is covered in small papillae (low conical projections) and looks like this.
The reticulum has a honeycomb like structure and sits next to the rumen and starts the mechanical breakdown of food into fine particles. This compartment is usually involved in “hardware disease” where cows swallow screws, nails wire or other hardware and it embeds into the lining. Occasionally this will completely penetrate the reticulum lining causing disease and as the reticulum sits next to the diaphragm will head into the thorax towards the heart.
The last structure unique to compound stomach is the omasum which is where the final stage of mechanical digestion takes place before the plant matter enters to Abomasum which is basically the same as a simple stomach. The lining of the omasum consists of really large muscular folds which help the mechanical breakdown of food into tiny particles suitable for digestion in the stomach and intestine. Below you can see the size of these folds in relation to the Rumen and Reticulum (its so big I’ve had to put multiple different pictures together to make it!)…
After this the food then enters the abomasum which is the same as the simple glandular stomach and enzymes and gastric juices start to digest the food here before it then enters the small intestine.
This afternoon in Physiology we finished up looking at the endocrine system which is responsible for controlling the body systems using chemical messengers (aka hormones). There are several different hormones and I do have plans to do a diary entry in depth on each hormone in the near future so will leave this here until then.