The main part of the respiratory system are the lungs. The lungs are where the air goes after you inhale. whenever you breathe in, the air goes down your trachea then splits into two bronchus, the left and right ones that lead into both lungs. then inside the lungs the bronchus split into a ton of bronchi. the bronchi are like little tree branches in the lungs. at the end of the bronchi are the alveoli. The alveoli are where the lungs and the blood exchange oxygen and carbon dioxide. Beneath your lungs is your diaphragm. When you breathe in, or inhale, your diaphragm contracts and moves downward. This increases the space in your chest cavity, and your that space allows your lungs to expand into it. On the outside of your lungs is your rib cage. your rib cage protects your lungs and everything around your chest area. now on to the tissue of the respiratory system.

Most of the respiratory tree, from the nose to the bronchi, is lined by pseudostratified columnar ciliated epithelium. The bronchioles are lined by simple columnar to the cuboidal epithelium, and the alveoli possess a lining of thin squamous epithelium.

The respiratory system actually works with other systems. for example, the circulatory system, which is made up of the heart and blood vessels, and it supports the respiratory system by bringing blood to and from the lungs. The circulatory system helps bring nutrients and oxygen from the lungs to tissues and organs throughout the body. Think of the respiratory system as an upside down tree. the trunk and large long stem of the tree is your trachea, which splits into two big branches and those branches split into smaller branches.

This system has one of the most vital organs, the heart. the heart is what allows our organs to function properly, including our brain. our heart pumps blood throughout the body and through our vein and artery. The heart is made up of 2 sides, the right atrium, and the left atrium. the main function of this system is to pump blood through the body to your organs and other things.

The cardiovascular system comprises four primary tissues known as muscle, nerve, epithelial, and connective tissues. Muscle tissue is involuntary and striated, and they aid in pumping blood throughout the body. Nerve tissues comprised of neurons are used as messengers in our body.

Like i said earlier, the circulatory system works with many other systems. for example, The small intestine absorbs most of the nutrients in your food, and your circulatory system passes them on to other parts of your body to store or use. Special cells help absorbed nutrients cross the intestinal lining into your bloodstream.

The circulatory system is like a town. there are highways, interstates, and tons of roads. your veins are like the little roads, and your artery's are like the big highways. and finally, the heart is like the whole big town, and is the most important thing out of them all.

The digestive system is made up of tons of different organs. so, lets start with the major ones. your stomach is where the food goes after you swallow and after it goes down your esophagus. in the stomach the food is churned and then it goes to your small intestine. in the small intestine all the nutrients are absorbed, and then it goes into the large intestine. in the large intestine, water is absorbed and then your end result is feces. some other parts of the digestive system are the pancreas, liver, gallbladder, and the appendix.

The two most important tissues in the GI tract are the mucosa and submucosa tissue layers. The mucosa forms the epithelial lining of the stomach and intestines, and produces the gastric juices used to break down and process food. Smooth muscle is also found throughout the body where it serves a variety of functions. It is in the stomach and intestines where it helps with digestion and nutrient collection.

The digestive system also works with many other systems. one of them is the muscular system. The large, hollow organs of the digestive tract contain a layer of muscle that enables their walls to move. The movement of organ walls can propel food and liquid through the system and also can mix the contents within each organ. Food moves from one organ to the next through muscle action called peristalsis.

The stomach is kind of like a pot in a way. the food goes in the pot, and it boils to make it edible. The stomach stores the food, like the pot does. It also mixes with digestive juices, which the pot also has liquid in it to help combine all the food into its designated recipe.

This system is made up of your brain, which is the most important in the body. it is also made up of the spinal cord, and all the nerves of your body. The brain is the control center of your body and the spinal cord is the major highway to and from the brain. The nerves carry the messages to and from the body, so the brain can interpret them and take action. There are tons of nerves in your body that are part of this system.

The main tissue in the nervous system is the nervous tissue. Nervous tissue is composed of two types of cells, neurons and glial cells. Neurons are the primary type of cell that most anyone associates with the nervous system. They are responsible for the computation and communication that the nervous system provides.

The nervous system works with other systems, just like the rest of them. One system it works with is the respitory system. Breathing requires complex interactions of the central and peripheral nervous systems with the respiratory system. It involves cortical (volitional) as well as subcortical (automatic) output. Cortical output is mainly through the corticospinal tract, whereas the brainstem sends signals via the reticulospinal tract.

If you think about it, the nervous system is like an orchestra. the brain acts as the conductor directing the activities of the nervous system. the neurons are the musicians, so each neuron plays a specific role just like each musician plays a different instrument.

The three main types of muscle include:

Skeletal muscle – the specialized tissue that is attached to bones and allows movement. Generally speaking, skeletal muscle is grouped into opposing pairs such as the biceps and triceps on the front and back of the upper arm. Skeletal muscles are under our conscious control, which is why they are also known as voluntary muscles. Another term is striated muscles, since the tissue looks striped when viewed under a microscope.

Smooth muscle – located in various internal structures including the digestive tract, uterus and blood vessels such as arteries. Smooth muscle is arranged in layered sheets that contract in waves along the length of the structure. Another common term is involuntary muscle, since the motion of smooth muscle happens without our conscious awareness.

Cardiac muscle – the muscle specific to the heart. The heart contracts and relaxes without our conscious awareness.

The muscular system works with other systems. One of the systems that it works with the most is the skeletal system. Tendons connect the skeletal system to the muscular system by attaching muscle to bone. When muscle contracts, the tendon acts on the bone, causing movement. Your skeleton supports the weight of your body. It's also the anchor for all the tissue that connects to it. Your joints, connective tissue and muscles all work together to push and pull parts of your body every time you move.

The muscular system is kind of like a car engine. Other muscles, like the ones in your stomach, heart, and intestines are involuntary - they are controlled automatically by the nervous system. In a car, the engine is very similar to the muscular system. They both help their systems to move. Without them, the car or body would not operate.