Back To CourseHuman Anatomy & Physiology: Help and Review
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Different organs can work together to perform a common function, like how the parts of your digestive system break down food. We refer to an integrated unit as an organ system. Groups of organ systems work together to make complete, functional organisms, like us! There are 11 major organ systems in the human body, which include the circulatory, respiratory, digestive, excretory, nervous and endocrine systems. The immune, integumentary, skeletal, muscle and reproductive systems are also part of the human body.
The circulatory system is responsible for transporting blood throughout the body. It consists of the heart and blood vessels known as veins, arteries and capillaries. Think of blood vessels as the highways of the body, bringing important cargo to and from the cells. In the circulatory system, blood is pumped from the heart to the lungs, so they'll get oxygen, and then pumped to the body's cells. Here is a diagram of the human circulatory system, including the heart and major arteries, which are in red, and veins, which are in blue.
In order for blood to provide oxygen to the body, the body must have a way of obtaining that oxygen. The respiratory system allows air to enter the lungs and for oxygen to diffuse into the blood en route to the body's tissues. The entrance to the respiratory system can be found in the nose and the mouth, where air enters the body and then travels through the larynx and pharynx in the throat to the trachea or windpipe. From the trachea, right and left branches, known as bronchi, carry oxygen to the alveoli, where oxygen moves into the blood, while carbon dioxide moves into the lungs to be exhaled.
The alveoli are the smallest parts of the respiratory system and deal specifically with exchange of gases, like traders at a market. For example, they receive goods, like oxygen and carbon dioxide, from other sources and then trade them in the lungs. In the following illustration, you'll find the major organs of the respiratory system, as well as an illustration of gas exchange in the alveoli on the left.
The digestive system is responsible for bringing food into the body and breaking it down to useable components. As shown in the diagram below, it starts at the mouth, where we ingest our food and use our saliva, teeth and tongue to bite and mash it. The food then travels through the esophagus into the stomach, where strong acids break it down even further. During the last two stages of digestion, nutrients and water are absorbed through the small intestine and the large intestine, respectively. Any remaining waste products are stored in the rectum and eliminated through the anus.
The urinary or excretory system is where liquid waste is eliminated as urine. The excretory system starts with the kidneys, important organs for cleaning the blood and balancing water in the body. In the excretory system, the liquid part of the blood, or plasma, enters through the kidneys, where important nutrients, like sugar and some salt, are reabsorbed into the body. Compounds we don't need, like urea or excess water, are sent to the bladder in the form of urine. Urine leaves the body through the urinary tract and exits the body at the urethra, as shown in the following illustration of the female urinary system.
Without a master control system that tells our bodies what to do, none of the organ systems we've talked about so far would work. The organs in the human nervous system are made up of cells, called neurons, that use chemicals and electricity to send messages. This system has two main parts, the central nervous system (CNS) and the peripheral nervous system (PNS), which you can see in the diagram below. The central nervous system consists of the brain and the spinal cord, which serve as the main control centers for the body and process all incoming and outgoing messages. The peripheral nervous system includes all the nerves in your body that bring messages to the central nervous system and from the CNS to the muscles.
Whereas the nervous system mainly uses electrical signals to communicate between cells, the endocrine system relies upon chemicals, called hormones, to send long distance messages through the body. For example, instead of communicating directly by talking to your neighbor, you decide to send him or her a letter. The main organs found in the human endocrine system are located in the brain and include the hypothalamus, thalamus and pituitary gland. They talk to other endocrine organs, like the adrenal glands, testes and ovaries to assist with other organ systems. The following is an image of the different organs that make up the endocrine system and secrete hormones.
Now let's move on to the immune system which acts like the guardian of your body by keeping harmful things, like pathogens or toxins, out and fighting any infection that gets in. It is made up of a series of tubes called lymphatic vessels, that help to screen the blood for pathogens. The immune system also includes white blood cells that patrol through the lymphatic and circulatory systems checking for invaders. There are many types of white blood cells that work together in your immune system, which are illustrated below.
The integumentary system works with the immune system to provide structure and support for our body. Skin is one organ found in this system. It protects the inside of our tissues and keeps invaders away. Hair and nails are other structural parts of the integumentary system.
The skeletal system also provides support for our body and allows us to stand and walk. It is made up of bones and cartilage. Cartilage is more flexible and supports those parts of our bodies that are not as rigid, such as the nose, ears and some elements of the ribcage. Key bones that make up the human skeletal system are shown in the illustration below.
The muscular system also provides structure for our body and works with the skeletal system to allow us to move. There are three types of muscle: cardiac muscle, which is found in the heart, skeletal muscle, which is involved in conscious movement, and smooth muscle, which is found in organs we do not consciously control, such as the stomach. In the following diagram of the skeletal muscle in a man's arm, we see the specific muscle cells and proteins that control movement.
The human reproductive system allows us to make new organisms. In females, it consists of the vagina, uterus, fallopian tubes, ovaries and eggs, as shown below.
Males have a penis, testes, and sperm, as shown in the following illustration. During sexual reproduction, sperm cells combine with eggs to form a new cell, called a zygote, the first step in forming a new organism.
In summary, the human body is made of 11 important organ systems, including the circulatory, respiratory, digestive, excretory, nervous and endocrine systems. They also include the immune, integumentary, skeletal, muscle and reproductive systems. The systems work together to maintain a functioning human body. For example, the circulatory system uses the heart to pump blood through the body to deliver oxygen and nutrients to cells. It works in partnership with the respiratory system, which provides us with the means to acquire oxygen, which is then transferred to the lungs and the alveoli.
The digestive system breaks down food and supplies important nutrients for our body; waste products are eliminated by way of the kidneys in the excretory system, which also filters blood. While the nervous system uses electrical and chemical systems to control bodily functions, the endocrine system performs a similar function, but through long-distance chemical messages. The immune system is made of white blood cells that keep our bodies safe from pathogens; hard structures that protect our bodies, like the nails and hair found in the integumentary system. Finally, we would not be able to move without the muscular system and skeletal systems, with the latter providing structure and support for our bodies.
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Back To CourseHuman Anatomy & Physiology: Help and Review
20 chapters | 736 lessons