In the lungs, gaseous exchange takes place: carbon dioxide from the blood filters into the air sacs as oxygen passes from the air to replenish the blood. The used air is then exhaled. Breathing is automatic: chest muscles contract and relax, acting like a pump on the ribs and diaphragm, driving air in and out of the lungs. The breathing rate varies in each individual and depends upon:
– age
– exercise
– emotion
– environmental temperature

The normal respiration rate of a healthy, resting, adult cat is 20-30 breaths per minute.
During respiration, the cat draws in air through his nasal passages via his nose and mouth. This air passes through the throat pharynx and down the windpipe trachea, through the bronchi and into the lungs.

Circulatory system
Every body cell needs a sugar nourishment, and this is achieved via the blood, which delivers it and removes waste products from the body. Blood is made up of red cells and white blood corpuscles and are contained in a fluid called Plasma. It contains platelets contain a blood-clotting agent in the event of cuts and wound.
Red blood cells transport oxygen while white blood corpuscles and transport impurities and be that have invaded the red cells.

Incredible journey
Blood is continually pumped around the body via the four-chamber heart, its journey beginning in auricle upper chamber. Filled with oxygen from the lungs, the blood from the left auricle travels it left ventricle lower chamber, into a great artery – the aorta – it coursed quickly through arteries and arterioles and intricate network of capillaries through, body, distributing its store of and nutrients as it goes. As it travels, the blood collects waste bacteria, dead blood cells & carbon dioxide.

Leaving the capillaries, the enters tiny veins and begins to slow down, gathering waste products, before passing the great veins that transport to the lungs before being replenished with oxygen and nutrients. From here it enters heart to repeat its journey.

Why cats are usually sleepy after meals
Extra nutrient-rich blood with its nutrients is required by different parts of the body at different times. After a heavy meal, for example, the cat’s abdomen draws in extra blood to aid digestion, at the expense of the supply to the brain and other parts of the body. Hence the need of the cat and indeed other animals to rest or sleep after eating – the brain is less active and energy is being utilized in digestion rather than in other activities.

Pulse
Blood passing through the aorta causes its walls to expand, and a pressure wave pulse passes down the arteries. In a healthy adult cat at rest, the pulse rate is 160-240 beats per minute, depending on environmental temperature and the cat’s emotional state at the time.