Understanding The Body

Introduction

• The human body has many different systems and ways it works. We use cells to have skin, bones to move, a brain to think. With out all these different functions or systems what would we be? Without our brain our race as animals would have died, we would have died. With out one system the others fail. The digestive, respritory, and circulartiory systeam all have differnt roles but they come and work together to help the human body.

The Respiratory System

• This system is used by all animals. It is an involuntary action that we use to breathe. Most people refer to it as breathing and humans use it all the time. It works when the windpipe, filters the air that is inhaled. Then the bronchial tubes lead to the lobes of the lungs. The right lung has three lobes; the left lung has two. The left lung is smaller to allow room for the heart. Lobes are filled with small, spongy sacs called alveoli, and this is where the exchange of oxygen and carbon dioxide occurs. The alveolar walls are extremely thin (about 0.2 micrometers). These walls are composed of a single layer of tissues called epithelial cells and tiny blood vessels called pulmonary capillaries. Blood passes through the capillaries. The pulmonary artery carries blood containing carbon dioxide to the air sacs, where the gas moves from the blood to the air. Oxygenated blood goes to the heart through the pulmonary vein, and the heart pumps it throughout the body. The diaphragm, a dome-shaped muscle at the bottom of the lungs, controls breathing and separates the chest cavity from the abdominal cavity. When a breath it taken, it flattens out and pulls forward, making more space for the lungs. During exhalation, the diaphragm expands and forces air out.

The Digestive System

• Digestion is the complex process of turning the food you eat into nutrients, which the body uses for energy, growth and cell repair, needed to survive. The digestion process also involves creating waste to be eliminated. The digestive tract is a long twisting tube that starts at the mouth and ends at the anus. It is made up of a series of muscles that coordinate the movement of food and other cells that produce enzymes and hormones to aid in the breakdown of food. Along the way are three other organs that are needed for digestion: the liver, gallbladder, and the pancreas.
• It first starts with the mouth. The smell of food triggers the salivary glands in your mouth to secrete saliva, causing your mouth to water. When you actually taste the food, saliva increases. Once you start chewing and breaking the food down into pieces small enough to be digested, other mechanisms come into play. More saliva is produced to begin the process of breaking down food into a form your body can absorb and use. In addition, "juices" are produced that will help to further break down food.
• The next part is when food travels down the pharynx, which is the portion of the digestive tract that receives the food from your mouth. Branching off the pharynx is the esophagus, which carries food to the stomach.
• Then the stomach, a sac-like organ with strong muscular walls, not only holds food, it serves as the mixer and grinder of food. The stomach secretes acid and powerful enzymes that continue the process of breaking the food down and changing it to a consistency of liquid or paste. From there, food moves to the small intestine. Between meals, the non-liquefiable remnants are released from the stomach and ushered through the rest of the intestines to be eliminated. Made up of three segments -- the duodenum, jejunum, and ileum -- the small intestine also breaks down food using enzymes released by the pancreas and bile from the liver. The small intestine is the 'work horse' of digestion, as this is where most nutrients are absorbed. Peristalsis is also at work in this organ, moving food through and mixing it up with the digestive secretions from the pancreas and liver, including bile. The duodenum is largely responsible for the continuing breakdown process, with the jejunum and ileum being mainly responsible for absorption of nutrients into the bloodstream. While food is in the small intestine, nutrients are absorbed through the walls and into the bloodstream. What's leftover moves into the large intestine
• Finally the large intestine is a five- to seven -foot -long muscular tube that connects the small intestine to the rectum. The appendix is a small tube attached to the ascending colon. The large intestine is a highly specialized organ that is responsible for processing waste so that defecation (excretion of waste) is easy and convenient.

The circulatory System

• This system is very important to our survival as a human race. It helps flow blood to and from places, mendicants, and oxygen. This is also an involuntary action that happens all the time.
• It involves the heart, blood, and blood vessels make which up the cardiovascular component of the circulatory system. It includes the pulmonary circulation, a "loop" through the lungs where blood is oxygenated. It also incorporates the systemic circulation, which runs through the rest of the body to provide oxygenated blood.
• The pulmonary circulatory system sends oxygen-depleted blood away from the heart through the pulmonary artery to the lungs and returns oxygenated blood to the heart through the pulmonary veins. Oxygen-deprived blood enters the right atrium of the heart and flows through the tricuspid valve into the right ventricle. From there it is pumped through the pulmonary semilunar valve into the pulmonary artery on its way to the lungs. When it gets to the lungs, carbon dioxide is released from the blood and oxygen is absorbed. The pulmonary vein sends the oxygen-rich blood back to the heart. The systemic circulation is the portion of the circulatory system is the network of veins, arteries and blood vessels that transports blood from heart, services the body's cells and then re-enters the heart.