Respiratory and Circulatory Systems
The respiratory system of nearly all animals begins within the nasal cavity. As an animal inhales the air travels through the cavity and is warmed during its journey. This is especially useful in cold weather. The warm air is more beneficial as it enters the lungs. Once the air reaches the lungs, it then moves over the larynx and pharynx (Sellnow, 2006). The larynx in the neck of the animal is where sounds emanate. The larynx also provides fortification to the trachea. The pharynx is muscular in structure and shaped like a cylinder or tube, it has both respiratory passages and digestive passages that are located behind the nasal cavity extending to the esophagus (Bio-medicine.org, 2009). When the animal, a horse in this case, eats the food is swallowed and the food is transferred into the esophagus or throat rather than the trachea used in breathing. The larynx acts as an impediment to trap food from entering the trachea (Medterms.com, 2009). The inhaled air travels through the trachea and enters the lungs through the bronchial tubes that fan out within the lungs.
The respiratory system functions in harmony with the circulatory system to fuel the body of the equine. Gases are exchanges between the air and the blood in the capillaries of the blood vessels in the alveoli walls within the lungs. The alveoli walls are like tiny receptacles that hold gases. There is a transfer here that allows the two systems circulatory and respiratory to work together. The oxygen will bind to the blood or hemoglobin to be carried away to the tissues of the body by the circulatory system (Sellnow, 2006). This oxygen is carried in the red blood cells to fuel the tissues. When this happens, the cells metabolize and carbon dioxide is generated. The metabolism of cells occurs when a cell expels energy and loses power as it builds molecules to complete a function of life such as rebuilding a cell. This expelling is called anabolism. Another function of metabolism is catabolism where a cell tears down the molecule to produce energy as it decreasing power.
Once the cell metabolizes the blood travels back through the veins with its load of carbon dioxide and a much smaller degree of oxygen. The amount of oxygen in the veins after metabolism occurs depends on the amount of work or exercise the horse is performing. If the horse is lounging around, then respiration is very slow and steady. If the horse is on the job, running in a race for instance, then respiration will increase as the lungs pump to produce enough oxygen through the entire body to sustain the activity (Sellnow, 2006).
The circulatory also called cardiovascular system is made up of the blood vessels and the heart muscle that pumps the blood. The heart controls the flow of blood. An adult equine animal can weigh as much as 1,000 pounds and will have a little over 13 gallons of blood. Blood is made up of white and red blood cells, liquid plasma and platelets. Platelets are sticky on the surface, colorless, and have irregular shapes. They allow the blood to clot (Bio-medicine.org, 2009). The hemoglobin within the red blood cells is a protein that attaches to oxygen and transfers in to the body tissues. White blood cells are the body’s defenders; working within the immune system to fight off any infection or bacteria that attempts to enter the body. The heart pumps this blood through the vessels. The system of blood vessels makes up the circulatory system (Sellnow, 2006).
Along with the intricate network of arteries, capillaries, and veins, the blood circulates through the body depositing necessary oxygen and nutrients throughout the body as it metabolizes to produce energy. The blood has also picked up dead cells and other garbage as it returns to the heart through the larger veins. The circulatory system deposits the blood back to the heart where it is flushed through to the kidneys for disposal. At higher levels of intensity where the horse is exerting a lot of energy, the heart rate will rise to enable more blood and the accompanying minerals and nutrients to provide the necessary fuel. Likewise when the horse is at rest, the heart rate will return to normal. The respiratory and circulatory systems of the body work together to produce oxygen and distribute it plus life giving blood and nutrients throughout the horse’s body. Providing the fuel and the energy to sustain its life.
- Bio-Medicine.org. (2009). Circulatory System. Retrieved March 5, 2009 from http://www.bio-medicine.org/biology-dictionary/Circulatory_system/
- Medterms.com. (2009). Larynx Definition. Retrieved March 5, 2009 from http://www.medterms.com/script/main/art.asp?articlekey=6224
- Sellnow, L. (2006). Of Blood and Breathe. Retrieved March 5, 2009 from http://www.bio-medicine.org/biology-dictionary/Circulatory_system/