The human body consists of 10 systems, as well as the function of the skin, which is technically a system of the physical body. This includes the Skeletal System, the Muscular System, the Cardiovascular System, the Respiratory System, the Nervous System, the Digestive System, the Urinary System, the Reproductive System, the Endocrine System, the Lymphatic System, and the Skin.
The Skeletal System of a human adult usually consists of 206 bones in total. Every human being physically, in essence, are vertebrates. Each persons body relies on its solid, internal frame which is supported by its spine. The skeleton is what provides us the ability to stand, sit, walk and move. Not only does it allow us to move, but it also shields our internal organs and gives us a sense of safety. For example, our skull shields our brains from the outside world. Bones also produce red blood cells within their bone marrow cavities which is an essential part to the body. Most of the formation of the red blood cells in the body are made within the bones, this is also true for Calcium. When the Calcium in the body becomes too low, it is released from the bones in order to insure enough for the metabolic needs. If the Calcium levels become too high, the excess is stored within the bones. There are many different types of bones in the Skeletal System. The bones consist of Long bones, Short bones, Flat bones, Irregular bones, Hyoid bone, 33 vertebrate bones (which creates the Spine), the Axial skeleton and the Appendicular Skeleton (including the upper body and lower body extremities). The bones of the body can be separated in to two different categories, or two divisions: the axial skeleton and the appendicular skeleton. 80 out of the 206 bones are of the axial skeleton. This forms the verticals axis of the human body. The bones of the axial skeleton include the bones of the head, vertebral column, ribs, and the sternum. The remaining bones are separated in to another division, which is called the appendicular skeleton. This appendicular skeleton consists of 126 bones. This includes the free appendages and the attachments to the axial skeleton.
The Muscular System is made up of muscles. Muscles are tissues that contract in the body. The human body has some where around 700 muscles. There are four main functions of the muscle contraction which include movement, posture, joint stability, and heat production. Muscles are attached to the bones by the tendons of the body. Muscles are divided in to three types, which include the skeletal (striated), smooth, and the cardiac. Skeletal muscles are in control of the voluntary movements of the bones. The Central Nervous System controls the skeletal muscles. The skeletal muscle tissue controls nearly all of the movement of the body due to its strong muscle contraction. Smooth muscles are involuntary. The smooth muscles include the blood vessels, the intestines, the bladder, the uterus, and the lungs. The smooth muscles are under the control of the autonomic nervous system and cannot be consciously controlled. There is only one cardiac muscle, and this is the Heart. The Heart is also controlled by the autonomic nervous system. The cardiac muscle is involuntary and moves rhythmically in the body. There are over 600 muscles in the body, which makes up around 40% of the human body weight. There are four major muscle groups in the body. The first consists of the muscles of the face, head and the neck. The next category consist of the muscles of the trunk or the torso. The third category is the muscles of the upper limbs, and the last are of the lower limbs. Each muscle fiber is completely surrounded by endomysium. The fibers of the muscle are lumped in to bundles that are covered by the perimysium. The bundles are called fasciculi. The fasciculi are wrapped together by the epimysium. All of these fibers in total is what creates each muscle.
The Cardiovascular System is also known as the Circulatory System. This system consists of the heart and the blood vessels. This Cardiovascular systems supplies oxygen and nutrients to all of the cells of the body. It also removes wastes residing in the body, which includes carbon monoxide. The heart contracts and pushes the blood with strong pressure into the arteries. Blood travels throughout the body while gradually decreasing in pressure. The blood then flows at a slower rate and circulates back to the heart via the veins of the human body. There are three types of blood vessels. Arteries, capillaries, and veins. The arteries carry blood containing oxygen and nutrients from the heart. The large arteries provide direct flow to the areas of the body, this includes the brain, the lungs, arms, and the abdomen or the solar plexus. If you press your finger on one of these larger arteries, you feel a heart beat. This is called the pulse. The artery coming from the heart is quite large, but flows and divides in to smaller branches. The second type of blood vessel is the veins, which carry blood to the heart. The last of the blood vessels are called capillaries. Capillaries connect the arteries and the veins together. The heart has two separate pumps, one on the left and one on the right. The left side of the heart pumps throughout entire body, and the right pumps blood directly to the lungs. The heart also contains four chambers. The four chambers are there so blood can both enter and leave the body simultaneously. The atrium is a temporary place that stores blood for delivery to the ventricle. The average heart weighs 10 ounces. This is about the size of a human adult fist. It mainly consists of a specific muscle which is called the cardiac muscle. This pumps blood through the body. Blood is made of plasma. Plasma contains red and white blood cells and fragments of cells called platelets. Blood has four main functions. Blood transports material through the body and carries away the wastes of the body. The blood protects us from germs by sealing cuts with plasma and also clots with white blood cells to keep us safe. The blood delivers messages through the hormones and blood also regulates our temperature in our bodies by directing blood to and from the skin.
The Respiratory System works with the Circulatory System to provide oxygen, and to remove the waste of the metabolism. This system controls the function of breathing, as well as the pH of the blood in the body. Breathing is called respiration. This process uses oxygen in coordination with the cells to create energy from food. Simultaneously, carbon monoxide and water are dispelled as waste. The Respiratory System consists of the nose, nasal cavities, the throat, the trachea, and the lungs. The throat is called the pharynx, which connects to the skull and to the vertebra. The trachea is more commonly known as the windpipe. The larynx is also known as the voice box. Nasal cavities filter the incoming oxygen. There are two conducting passages, which include the upper respiratory tract and the lower respiratory tract. The upper respiratory tract contains the nasal cavity, the pharynx, and larynx. The lower respiratory tract contains the trachea, the bronchi, and the lungs. The left lung is longer than the right, more narrow and divided in to two lobes. The right lung is shorter, more broad and is divided in to three levels he’s. When you breathe, the air is 79% nitrogen, 21% oxygen, and 0.04% carbon dioxide. This breath travels through the trachea, through two tubes called the bronchi. The bronchi lead directly to the lungs. The process of respiration includes ventilation, transport of the gases, the external respiration, internal respiration, and the cellular respiration. No conscious effort is required for breathing in nor out.
The Nervous System is the control and communication system for the body. The Nervous System consists of the brain, spinal cord, nerve cells and the nerve fibers that travel throughout the body. There are millions of nerve cells within the body that carry electrical messages in the body. Messages travel at 220 miles per hour. They call this “nerve impulse”. Messages are broken down in to two parts. The first system is called the central nervous system (CNS) – made up of the brain and spinal cord. The second system is called the peripheral nervous system – made up of all the nerves that run from the central nervous system. These two systems control the reactions to the environment around the physical body, as well as the involuntary movements of the muscles, the cardiac muscle (the heart) and the lungs. The automotive nervous system is also an important component here, and mainly regulates the involuntary organs in conjunction with the peripheral nervous system. There are three main types of nerve cells. There are the motor nerves, the sensory nerves, and the connector nerves. Motor nerves carry specific messages that originate in the brain and spinal cord, and carry those messages to the glands and the muscles in the body. Motor nerve cells connect the sensory nerve cells together, which allows decision making of an individual. The sensory nerve cells connect the body’s sense organs to the central nervous system. It is through the sensory nerve cells that the bodies information from senses reach the brain. The Nervous System is the center in the body where all mental activity takes place. This includes any thought within the body, the learning and the memory. This also includes any reflexes a person has: blinking, sneezing, coughing, ‘jumping’ or ducking. Information concerning a reflex would start straight from where the physical pain originates, and be sent to the spinal cord. The information is then transferred to a neuron that connects to a motor neuron. Neurons are also called nerve cells. Every neuron has three parts to it. This includes the cell body (soma), dendrites (fibers), and an axon.
The Digestive Systems main role is to break down all foods and convert them in to energy for the cells of the body. There are two main parts to the Digestive System. The alimentary canal is a long tube that extends to around 9 meters long. This canal begins in the mouth to the anus. The alimentary canal includes the throat, esophagus, stomach, the small and large intestines. The second main part includes the organs and glands, they also play a major part in this process. The teeth, tongue, salivary glands, pancreas, liver and the gallbladder. The digestive tract wall includes four different layers: mucosa, submucosa, the muscular layer, and the serous layer. The food that is ingested goes through three types of processes: digestion, absorption and elimination. The largest pieces of food have to be broken down. The breaking down occurs through the enzymes in conjunction with the food that is ingested. This is called mechanical digestion. There is another type of digestion called hydrolysis. Hydrolysis is also known as chemical digestion. Molecules as a result of the chemical digestion pass through cell membranes in the lining of the small intestine. This carries over into the blood. This is the process of absorption. Elimination is very important and the last process of the Digestive System. The removal of the wastes in the body move through and exit through the rectum and the anus. Before the food wastes are eliminated, everything passes through out the body to the liver, gallbladder, the pancreas, the large and large intestines.
The Urinary System plays an important role in eliminating wastes from the body, just like the Digestive System. The Urinary System is there to excrete liquid wastes. The function of this system controls the appropriate amounts of water that is removed from the body. Not only does it regulate the water and wastes, but it also controls the red blood cell production and the blood pressure by excreting a specific enzyme called renin. The Urinary System is made up of he kidneys, ureters, urinary bladder, and the urethra. There are two kidneys, which filter out chemicals and electrolytes from the blood in the body. They kidneys maintain the acid and alkaline balance. The ureter is a small tube that is around 25 centimeters in length. This carries the urine from the pelvis, to the urinary bladder. The wall of the ureter consists of three layers. The outer layer is made of fibers that support the layer of connective tissue. The second layer of the ureter consists of muscles. This propels the urine throughout the ureter. The inside layer is the mucosa. The mucosa coats and protects the surface of the cells by secreting mucus. The urinary bladder is the temporary storage for the urine in the body. The size and shape of the bladder depends on how much urine it contains, as well as the pressure from surrounding organs. The urethra is the ending passageway in which the urine flows out of the system. There is a lining to the urethra and an internal, or muscle, which pushes the urine through and out of the body. There urethra actually has a voluntary and involuntary muscle for this final passageway.
The Reproductive System consists of organs that assist in the creation of offspring, or children. It exists mainly to ensure the continuation of our human species. Not every person chooses to create offspring, but for the species to continue, some individuals will have children. The male and female reproductive organs differ in organs and in appearance. When sexual intercourse occurs between a male and female, the male counterpart provides the sperm cell which fertilizes the female egg. This is how the fetus is created. The Reproductive System has four main functions. This consists of producing the egg – or sperm, transporting and sustaining the cells, to nurture the creation and development of the offspring, and to produce hormones of the body. The functions of the system are divided in to three parts: primary, secondary, and accessory. The primary reproductive organs (gonads), are made up of the ovaries and the testes. They are responsible for the production of the egg, the sperm cells, and the hormones. The hormones fluctuate and change as the Reproduction System matures. All the remaining functions of the system include the organs, ducts, and the glands. These are all considered secondary, or accessory reproductive organs. The male Reproductive System consists of a pair of testes, a system of excretory ducts, ejaculation ducts, seminal vesicles, the prostate, the bulbourethral glands, and the penis. The female Reproductive System consist of the ovaries, fallopian tubes, uterus, vagina, accessory glands, and the external genital organs, i.e: the clitoris and the labia.
The Endocrine System is made up of glands. The Endocrine glands secrete hormones to the bloodstream. These hormones reach every part of the body, due to flowing through the blood. There are two major categories of the glands in the body. The first is called the exocrine glands, and the second are the endocrine glands. The exocrine carry secretions to the surface of the body, up through the skin. These glands include the sweat glands, the sebaceous glands, the mammary glands, and the glands which secrete digestive enzymes in the body. As mentioned before, the endocrine glands secrete hormones. Hormones are chemicals produced in one area of the body but effect on other parts of the body. There are over 30 hormones. The hormones majorly effect all of the body functions. Specifically the metabolism, reproductive organs, digestion, urine production, as well as the psychological activity in a person. The main hormone is called Thyroxine. This is produced by the thyroid gland and it controls how food is converted into energy. Too much of the hormone can causes underweight tendencies in an individual, and too little can cause someone to be fatigued, weight gain and general discomfort. The major endocrine glands consist of the thymus, thyroid, parathyroid, pituitary, pineal, adrenal, pancreas, ovaries, and the testes. The glands are exactly the same for both sexes, aside from the ovaries belonging to the female and the testes belonging to the male. In addition to the major endocrine glands, there are other organs which play a part in the hormonal activity. This includes the stomach, the small intestines, the heart, and the placenta of the female.
The Lymphatic System has three main functions. The first function is to return excess fluid to the blood. About 90% of the fluid that comes from the capillary gets returned. The remaining 10% does not return and becomes fluid that surrounds cells. Sometimes proteins will leak through the capillary walls, which increases the pressure of the fluid. If the leaking continues, it builds up in blood volume and accumulates in the spaces between the tissues. This causes swelling, or edema. Lymph capillaries carry the excess fluid and proteins and return them to the blood. When the fluid enters the lymph capillaries, it is called lymph. The second function of the system is the absorption of the fats and fat soluble vitamins from the digestive system. The third function of the Lymphatic System is the defense against invading bacteria, microorganisms and disease. The Lymphatic organs are in clusters of lymphocytes, cells, and branching connecting fibers. Lymphocytes are made in the red bone marrow along with other blood cells. These are carried in the blood from the bone marrow to the lymphatic organs. When the body is exposed to dangerous bacteria and organisms, the lymphocytes work with the lymphatic organs to send blood to that area of invasion. This is called the immune response. This is the defense system the body uses to protect us and to destroy the invasion of bacteria. The lymph node structure is around 2.5 cm in size or shape. They consist of the efferent lymphatic vessel, the sinus, module, capsule, hilum, valve to prevent back flow of the lymph node, and the afforestation lymphatic vessel. Tonsils play a major part in the system, as well as the spleen and the thymus.
The Skin is the largest organ of the body. It completely encases and covers all of the organs and tissues. The Skin is an ever changing and growing organ. It protects us from the rain, from the sun, and infectious organisms. The Skin plays a large role in regulating the temperature of the human body. The Skin also provides us with one of our 5 senses, and this is the sense of touch. We can feel because of our skin. It controls our sensory information. There are three layers of the skin: the epidermis, the dermis, and the subcutaneous tissue. The epidermis layer is considered the most outer layer of our skin. It contains 5 layers. The thickness of the epidermis varies for each person. From the bottom layer to the top of the epidermis, the layers are called: stratum, basale, stratum spinosum, stratum granulosum, stratum licidum, and corneum. The top layer called the stratum corneum sheds every two weeks. The dermis size and thickness also varies from person to person. The dermis is made of three tissues, but they are not layers. The types of tissue are collagen, elastic tissue, and reticular fibers. The dermis contains specific structures and cells. Hair is also grown here, in what is called a follicle. There are also two different glands associated with the follicle. Sebaceous (oil) glands, and sudoriferous (sweat) glands. The subcutaneous tissue is a layer of fat and connective tissue that contains large blood vessels and nerves. This layer is very important when regarding the temperature and regulation of temperature of the skin and the body itself. The Skin contains many functions, and the quality of the outside of the body can give many indications of a persons health or dis-ease.