The respiratory system consists of a series of organs that are responsible for both taking in oxygen and expelling carbon dioxide (Zimmermann 1). The primary organs of the respiratory system are the lungs, which carry out this exchange of gases as one breathes (Zimmermann 1).
Red blood cells collect the oxygen from the lungs and carry it to the parts of the body where it is needed (Zimmermann 1). During the process, the red blood cells collect the carbon dioxide and transport it back to the lungs, where it leaves the body when one exhales (Zimmermann 1).
The human body needs oxygen to sustain itself (Zimmermann 1). A decrease in oxygen is known as hypoxia and a complete lack of oxygen is known as anoxia, which can be fatal (Zimmermann 1). After about four minutes without oxygen, brain cells begin dying, which can lead to brain damage and ultimately death (Zimmermann 1).
In humans, the average rate of breathing is dependent upon age (Zimmermann 1). A newborn's normal breathing rate is about 40 times per minute whereas for adults, the average resting respiratory rate is 12 to 16 breaths per minute (Zimmermann 1). Physical exertion also has an effect on respiratory rate, and healthy adults can average 45 breaths per minute during strenuous exercise (Zimmermann 1).
As one breathes, oxygen enters the nose or mouth and passes the sinuses, which helps to regulate the temperature and humidity of the air one breathes (Zimmermann 1). The trachea, also called the windpipe, filters the air that is inhaled. It branches into the bronchi, which are two tubes that carry air into each lung (Zimmermann 1). The right lung has three lobes and the left lung has two in order to allow room for the heart (Zimmermann 1). The lobes are filled with small, spongy sacs called alveoli, and this is where the exchange of oxygen and carbon dioxide occurs (Zimmermann 1). The alveolar walls are extremely thin and are composed of epithelial cells and tiny blood vessels called pulmonary capillaries through which blood passes (Zimmermann 1). The pulmonary artery carries blood containing carbon dioxide to the air sacs, where the gas moves from the blood to the air (Zimmermann 1). Oxygenated blood goes to the heart through the pulmonary vein, and the heart pumps it throughout the body (Zimmermann 1).
The diaphragm, a dome-shaped muscle at the bottom of the lungs, both controls breathing and separates the chest cavity from the abdominal cavity (Zimmermann 1). When a breath it taken, it flattens out and pulls forward, making more space for the lungs (Zimmermann 1). During exhalation, the diaphragm expands and forces air out (Zimmermann 1).
The circulatory system, also known as the cardiovascular system, is a crucial aspect of the human body because it helps the human body in several different ways (Circulatory 1). It helps fight off disease, it helps the body maintain a normal body temperature, and it provides the right chemical balance to provide the body’s stable internal environment, which is known as homeostasis (Zimmermann 1).
The circulatory system consists of four major components: the heart, arteries, veins, and the blood (Circulatory 1). The heart is about the size of two adult hands held together and lies near the center of the chest (Circulatory 1). The heart is extremely important as it keeps the circulatory system working at all times due to its consistent pumping (Circulatory 1). The arteries carry oxygen-rich blood away from the heart to wherever in the body that it needs to go (Circulatory 1). The veins carry deoxygenated blood to the lungs where they receive oxygen (Circulatory 1). Blood is the transport media of nearly everything within the body (Circulatory 1). It transports hormones, nutrients, oxygen, antibodies, and other important things needed to keep the body healthy (Circulatory 1). Oxygen enters the bloodstream through small membranes in the lungs that absorb oxygen as it is inhaled (Circulatory 1). As the body uses the oxygen and processes nutrients, it creates carbon dioxide, which one’s lungs expels as he/she exhales (Circulatory 1). A similar process occurs with the digestive system to transport nutrients, as well as hormones in the endocrine system (Circulatory 1). These hormones are taken from where they are produced to the organs they affect (Circulatory 1).
There are three different types of circulation that occur regularly in the human body: pulmonary circulation, systemic circulation, and coronary circulation (Circulatory 1). Pulmonary circulation is the part of the cycle that carries oxygen-depleted blood away from the heart, through the pulmonary artery, and to the lungs, returning with oxygenated blood back to the heart (Zimmermann 1). Systemic circulation is the network of veins, arteries, and blood vessels that carry oxygenated blood away from the heart and to other parts of the body (Circulatory 1). Lastly, coronary circulation is the type of circulation provides the heart with oxygenated blood so it can function properly (Circulatory 1).
The circulatory system works due to constant pressure from the heart and valves all throughout the body, ensuring that veins carry blood to the heart and arteries transport it away from the heart (Circulatory 1).
The digestive system is constructed in a unique way in order to perform its specialized function of turning food into the energy one needs to survive and packaging the residue for waste disposal (Digestive 1). To help one understand how the many parts of the digestive system work together, it is important to look at an overview of the structure and function of each of its parts (Digestive 1).
Digestion begins in the mouth immediately when one takes his/her first bite of food (Digestive 2). Both chewing and saliva breaks down the food into pieces that are more easily digested (Digestive 2). Next, when one swallows, the esophagus, which is located in the throat near the trachea, receives food from his/her mouth (Digestive 2). Through a series of muscular contractions called peristalsis, the esophagus delivers the food to the stomach (Digestive 2). The stomach is a hollow organ that holds food while being mixed with enzymes that continue the process of breaking down food into a usable form (Digestive 3). When the contents of the stomach are sufficiently processed, they are released into the small intestine (Digestive 3).
The small intestine, a 22-foot long muscular tube that breaks down food using enzymes released by the pancreas and bile from the liver, is made up of three segments: the duodenum, jejunum, and the ileum (Digestive 3). Peristalsis is also at work in this organ, moving food through and mixing it with digestive secretions from the pancreas and liver (Digestive 3). Contents of the small intestine start out semi-solid, and end in a liquid form after passing through the organ (Digestive 3). Once the nutrients have been absorbed and the leftover-food residue liquid has passed through the small intestine, it then moves on to the large intestine, or colon (Digestive 3). The colon, a 6-foot long muscular tube that connects the small intestine to the rectum, is made up of the cecum, the ascending colon, the transverse colon, the descending colon, and the sigmoid colon (Digestive 4). The large intestine is a highly specialized organ that is responsible for processing waste so that emptying the bowels is easy and convenient (Digestive 4). Stool, or waste left over from the digestive process, is passed through the colon by means of peristalsis, first in a liquid state and ultimately in a solid form over the course of about 36 hours (Digestive 4). When the descending colon becomes full of stool, it empties its contents into the rectum to begin the process of elimination (Digestive 4).
The rectum, an 8-inch chamber that connects the colon to the anus, receives stool from the colon, lets the person know that there is stool to be evacuated, and holds the stool until evacuation occurs (Digestive 5). The anus, a 2-inch long canal consisting of the pelvic floor muscles and the two anal sphincters, is the last part of the digestive tract (Digestive 5). The pelvic floor muscle creates an angle between the rectum and the anus that stops stool from coming out when it is not supposed to (Digestive 5). The internal sphincter is always tight, except when stool enters the rectum (Digestive 5). When one gets an urge to go to the restroom, he/she relies on his/her external sphincter to hold the stool until reaching a toilet, where it then relaxes to release the contents (Digestive 5).