There are many pieces and parts that make your dog the guy he is. He is a collection of complicated systems that allow him to run, jump and bark. He also has keen hearing, a super-sensitive nose and feet for walking on tough surfaces.
Cardiovascular and Digestive Systems
The cardiovascular system ferries blood from your dog's heart though his arteries, veins and capillaries to the rest of his organs. Filled with oxygen and nutrients, his blood is fuel for his organs. His digestive system is more than his stomach and intestines; it also includes his mouth, where he chews his food and salivary glands, which provide enzymes to begin the digestive process. Other digestive system organs include the gall bladder, liver and pancreas, all of which contribute to absorbing and digesting food and eliminating solid waste from his body.
Respiratory and Hematopoietic Systems
Your dog's respiratory system does more than help him breathe; it also helps him regulate his body temperature since he can't sweat through his skin -- he pants to keep his cool. His respiratory system includes his mouth, trachea, lungs and the bronchi and bronchioles, the small airways in the lungs that feed him oxygen and remove carbon dioxide. One of the important functions of his hematopoietic system is maintaining the blood cells in his bone marrow. His bone marrow produces white and red blood cells, as well as platelets, to help his blood clot, fight infection and carry oxygen through his body.
Lymphatic, Endocrine and Urogenital Systems
The lymphatic system is instrumental to your dog's immune system and his ability to ward off disease. It also assists the cardiovascular system to replace fluids from the blood vessels back into the bloodstream. His thyroid, parathyroid and adrenal glands are all part of his endocrine system and produce a variety of hormones. His urogenital system removes waste from his bloodstream, to be eliminated as urine, and is also responsible for reproduction. The organs in this system include the kidneys, ureters, bladder and genital organs.
Musculoskeletal, Integumentary and Central Nervous Systems
Your dog's muscles, bones, joints, ligaments and tendons comprise his musculoskeletal system, which helps him move. Whether his fur is long or short, curly or straight, it's all part of his integumentary system. His skin and fur protect everything underneath and insulate him from heat loss. The central nervous system uses the brain, nerves and spinal cord to allow all of your dog's pieces and parts to communicate and work together.
Your dog interacts with the world around him through his sense of smell, sight, hearing and taste. His ears not only hear things, but are important to his balance, thanks to his inner ear. A dog can hear a greater range of frequencies than a human can, picking up sounds in the range between 67 and 45,000 Hz. The placement of a dog's eyes allows him a narrow binocular field of vision but a wide peripheral field of vision. His nose possesses up to 300 million olfactory receptors, making for a very sharp sense of smell.
Paws and Tail
A dog's foot pads serve as insulation against extreme weather, protect tissue within his paws and provide additional cushioning for his bones and joints. His tail is a communication tool, acts as a rudder when he swims and serves as a counterbalance to help him stand steady.