 This video will give you an overview of an Introduction to Human Anatomy. The material comes from the OpenStacks Anatomy and Physiology textbook as well as Grey's Anatomy. As we go, we will cover the following objectives, define anatomy and physiology, and describe the relationship between structure and function. Describe homeostatic control mechanisms, compare negative and positive feedback, and be able to give and recognize examples of each. Describe the levels of structural organization found in the body and their relationships to each other, chemical, cellular, tissue, organ, organ system, and organism, and list the 11 organ systems of the body, their organ components, and the system's overall general functions. Anatomy is the study of body structures and their relationships to one another. There are different subdivisions of anatomy. We could study gross anatomy, which is the study of all the large structures that are visible to the naked eye. We could study surface anatomy, which is the study of the structures that are visible without making any cuts, without slicing up or sectioning the body. We can study the surface anatomy. And systemic anatomy is the study of structures that work together to perform a common function. And so here we see the cardiovascular system, which includes several different organs, including the heart, which provides the pumping action to move blood through the blood vessels. And so the heart and blood vessels work together to perform a common function of delivering nutrients throughout the body and removing waste from the body. And so the circulatory system, or the cardiovascular system, is a collection of organs that work together for a common function. And so systemic anatomy is the approach of studying the structure of organs that are working together to form a common function. Here on the left we can see an image of the human brain. And so the gross anatomy of the nervous system would include studying the structures visible to the naked eye, such as the specific lobes of the brain. We can see here the temporal lobe, frontal lobe, parietal lobe, and occipital lobe are all major regions of the brain. And we could also study microscopic anatomy of the nervous system. We could slice the brain and look at it under a microscope. And so microscopic anatomy is the study of small structures that cannot be seen with the naked eye that we can only study with magnification. And so here in the image we can see neuron cells, the cells that are important for signaling, sending, communication rapidly through the nervous system. And if we study the structure of an individual neuron cell and the various internal structures inside of a cell called organelles, then we're studying cytology, cytology or the study of cell structure. However, multiple cells work together and there are different types of cells performing related functions in order to work together within an organ. And we call this collection of different cells working together a tissue. The study of tissues is called histology. And so here we can see another image showing nervous tissue. And we can see there are several different types of cells found in nervous tissue. There are neurons as well as glial cells and different types of glial cells like astrocytes, microglial cells and oligodendrocytes. And all of these cells are working together as a tissue and the study of the tissue structure is known as histology. The study of cell structure is known as cytology. And so we could magnify even further and look way deep inside of a cell and see the structures inside of a cell. These large structures inside of a cell are called organelles. Here we can see an illustration of a specific organelle called a mitochondria which is found inside of cells. And we can only view structures this small as the mitochondria and the membranes, the inner and outer membranes that form the mitochondria. In order to see this much detail we need to use a special microscope called an electron microscope. And so the image on the right here is a picture taken with an electron microscope allowing us to see the mitochondria inside of a cell magnified 236,000 times from its normal size. With our light microscopes we won't be able to see anything more than about a thousand times magnification. And so we won't be able to see this much detail with light microscopes. However we will study some basic cytology and we'll study lots of histology using the light microscopes in the laboratory. So anatomy is the study of biological structures. Physiology is the study of the function of those structures. So the study of how the body works, how the structures of the human body function is physiology. People used to think that the heart was the region of the body, the structure in the body that was important for consciousness, for thought, for processing sensory information and responding to that information. And it was thought that the brain served a function of regulating the temperature of the blood. Modern research has led us to a different perspective showing us that the function of the brain is sensation and the control of movement. And the heart is important for pumping blood throughout the body. So the heart has the function of pumping blood through blood vessels in order to provide nutrients to cells all through the body and remove waste from those cells. The heart's pumping action can be demonstrated if someone has loss of heart function, if they have a heart attack and their heart stops beating, then we can see that the pressure inside of their blood vessels will decrease and blood will stop being pumped through the body. And so this loss of function approach is often how we've learned the function of biological structures. Similarly, if someone has a stroke that is a loss of blood supply to part of the brain, then we can see impairment in sensation or the control of movement, some aspect of the cognitive functions that the brain performs will be impaired if there's damage to the brain. And so a grand theme in the field of anatomy and physiology is that structure determines function. We have an example here of the elbow joint. The elbow joint is where the humerus and ulna come together, forming a hinge joint. And so the region of the humerus that fits into the ulna is called the trochlea, which is at the distal end of the humerus. So the humerus, your arm bone, the distal end is the end out near the elbow and the distal end has a surface and a surface that articulates or forms a joint with the ulna. And that surface is called the trochlea of the humerus. And the trochlea of the humerus fits tightly into the ulna, a region of the ulna that has a notch shape known as the semilunar notch or the trochlear notch because the trochlea of the humerus fits into this notch. It's often called the trochlear notch. And the tight fit between these bones restricts motion but enables motion as well. And so the tight fit enables motion to flex and extend the elbow. The way that you're used to being able to move the elbow is flexion and extension through the sagittal plane. And other motion is restricted. So we can't perform rotation of the elbow. We can't perform abduction and abduction of the elbow. There's very limited ability to rotate and move the elbow in other directions except for the one motion of flexion and extension. And so the structure of the elbow joint determines the range of motion determines the function of the elbow. Another major theme in anatomy and physiology is the concept of homeostasis. That is a state of balance in which the body's internal environment remains relatively stable despite changes in the internal and external environment. A homeostatic control mechanism maintains homeostasis and involves a variable which is some factor being regulated. And that variable is maintained within a set range, the homeostatic set point. If there is a change in the variable outside of the set point, if it becomes higher or lower than the set point, that change is a stimulus. And the stimulus is detected by a sensor also known as a receptor that is monitoring the environment. And when it detects a change, it relays that information into a control center usually found in the central nervous system. The control center analyzes input from the receptor or sensor and then determines the appropriate output that will be sent as commands in order to regulate the activity of an effector cell or organ. The effector carries out the response in order to regulate the variable either depressing or enhancing, either increasing or decreasing the level of that variable. Most of the homeostatic control mechanisms we'll study in this class are negative feedback mechanisms where the response of the effector counteracts the intensity of the original stimulus. The example we see here on the right shows the negative feedback mechanism to maintain body temperature. The homeostatic set point for body temperature is around 37 degrees Celsius. If our body temperature is too high, if it exceeds 37 degrees Celsius, then sensors that are nerve cells in the skin and brain will detect this stimulus and send the signal in to a temperature regulatory control center in the brain, which then sends commands out to effector organs like sweat glands in our skin, which will produce sweat in order to cool our body down, restoring the homeostatic set point for our body temperature. And so we'll see many negative feedback mechanisms as we go through this class. Another example would be regulating blood composition. For example, the concentration of calcium in the blood is regulated by a negative feedback loop where the parathyroid gland is the sensor that measures blood calcium levels and also serves as a control center that will secrete a hormone, parathyroid hormone. If blood calcium levels fall too low, parathyroid gland produces parathyroid hormone, which stimulates the effector organ of the bones to release calcium into the blood in order to maintain blood calcium concentration, restoring homeostasis. A positive feedback mechanism is less common in the body, but involves an effector producing a response that intensifies the original stimulus, which causes the variable that's being regulated to move further away from its normal limits, which will be destabilizing. The example shown here is childbirth, which is driven by a positive feedback loop where the head of the baby pushing against the cervix, the opening of the uterus, is detected by sensors. These sensors detect the stretching of the cervix and transmit that information into the brain, and then a region of the brain causes the pituitary gland to release a hormone. A region of the brain stimulates the pituitary gland to release this hormone called oxytocin. Oxytocin travels through the blood to reach the uterus, where it stimulates the uterus to contract. As the muscles of the uterine wall contract, the babies pushed towards the cervix, producing further stretching of the cervix. As the cervix stretches and the sensors in the uterine wall detect stretching of the cervix, we get a stronger signal traveling into the brain, stimulating even more oxytocin to be produced, which stimulates even more contraction of the uterine wall, and even more stretching of the cervix until eventually the baby is born at childbirth. The baby is delivered, then stretching will no longer occur, and that will end this positive feedback loop. Another example of a positive feedback loop would be blood clotting, where cells called platelets, or fragments of cells called platelets that are found in our blood, in fact, they serve as the sensor to detect bleeding, they detect a tear in the blood vessel, and they start to stick to that tear, and they release signals called clotting factors. And those clotting factors will recruit more platelets to come stick to the tear in the blood vessel to join producing more clotting factors that continue to attract more platelets in a positive feedback mechanism until the blood vessel tear has been completely covered with a clot, which stops the bleeding and ends the positive feedback cycle. The human body is organized in six distinct levels of increasing complexity from the smallest chemical building blocks all the way up to an organism, a human, an individual, like yourself. And so the smallest level and simplest level of organization is the chemical level, where atoms are the smallest particles, which are the building blocks of matter, and molecules are multiple atoms combined together, multiple atoms held together through chemical bonds. And so here we can see the water molecule as an example, where two hydrogen atoms are chemically bonded to one oxygen atom forming H2O or water. The next level of analysis is the cellular level. Cells are the smallest living units in the body. Cells contain many molecules that are together forming a cell. We'll see different types of molecules that are commonly found in cells are proteins, which are very important structural functional units inside of the cell and multiple proteins working together carry out most of the functions of the cell. Together with nucleic acids like DNA and RNA that provide the genetic instructions to produce proteins and then there are some other molecules that are important for producing cells. There are lipids like the phospholipid that forms a bilayer creating a membrane surrounding a cell and many of the structures inside of the cell called organelles are also composed of a bilayer of a lipid or a phospholipid bilayer. And so there are many different types of cells and cells together form tissues. The next larger level and slightly more complicated level of organization is the tissue level where similar cells are grouped together to perform a common function. We can see the example here of smooth muscle tissue. It's a multiple smooth muscle cells together form a smooth muscle tissue that can contract in order to control the size of an organ. And so the wall of the urinary bladder contains smooth muscle called the detrusor muscle that contracts when we urinate to relieve our bladder. So we can see the organ level is the next level up which consists of multiple different tissues. There is the smooth muscle layer of the bladder but there's also a inner lining of the bladder and a mucus membrane that's lining the inner surface of the bladder that contains different types of tissues like epithelial tissues and connective tissues. And then the next level up from the organ level is the organ system. Here we can see the urinary system consists of the kidneys that filter the blood and produce urine. Uritors that are muscular tubes that transport urine from the kidney to the bladder, the urinary bladder that stores the urine and then can contract in order to release urine from the body through the urethra. So the urinary system is just one of 11 organ systems that work together within an organism. So the organism is the entire human body which consists of 11 organ systems that work harmoniously together to perform the functions of an individual organism. Now we'll go through each of the 11 organ systems starting off with the integumentary system which consists of the skin, hair, nails, sensory receptors for touch. We also have sweat glands and other exocrine glands like sebaceous glands that are found in the skin. The functions of the integumentary system are to enclose and protect the body and contains sensory receptors that perform the functions of detecting sensory information for touch. The next system we see here is the skeletal system that consists of bones, cartilage and ligaments and the functions of the skeletal system include supporting the body and enabling movement. The muscular system consists of muscles and tendons that function to the muscles contract pulling on tendons in order to produce motion and the metabolism of muscles is also important for producing heat and warming our body. The nervous system consists of the brain, the spinal cord and nerves that connect to the brain and spinal cord will see there's cranial nerves and spinal nerves that connect to the brain and spinal cord. The functions of the nervous system include collecting sensory information, processing this information and then sending information out in order to regulate organs like the muscles and glands of our body. The endocrine system includes many different endocrine glands, for example the pituitary gland, thyroid gland, pancreas, adrenal gland, gonads in men, the testes and in women, the ovaries. And the functions of the endocrine system are to regulate other organs but through chemical communication the endocrine system glands produce hormones that are chemical signals that travel through the blood throughout the body in order to regulate other organs. The cardiovascular system includes the organs of the heart and blood vessels and the functions are to circulate blood around the body in order to deliver nutrients to organs and cells and carry the waste products away from those organs and cells. The lymphatic and immune system includes the organs of lymphatic vessels, lymph nodes, spleen and thymus. The functions of the lymphatic and immune system are to drain fluid from peripheral tissues and this fluid is drained into veins to return back to the blood. And also to defend the body against pathogenic organisms like pathogenic bacteria or pathogenic viruses that can make us sick and endanger the body. The respiratory system includes the lungs, bronchi, trachea, larynx, ferrinx, nasal cavities and sinuses and the functions are to bring air in and out of the body enabling external respiration where oxygen is transferred into the blood and carbon dioxide is removed from the blood. The digestive system organs include the oral cavities, salivary glands, ferrinx, esophagus, stomach, small intestine, liver, gallbladder, pancreas and large intestine. The primary function is to ingest food, break that food down and absorb nutrients from the food and then eliminate waste from the body. The urinary system organs include the kidneys, ureter, urinary bladder and urethra and the functions of the urinary system are to filter blood producing urine. And as the blood is being filtered the kidneys regulate the composition of the blood and then any waste or excess water or excess nutrients are eliminated from the body in the urine. The reproductive system in men includes the testes, epididymis, ductus deference, seminal glands, prostate gland and penis. In women it includes the ovaries, uterus, vagina, vulva and mammary glands. And the functions of the reproductive system are to produce offspring. The men produce the sperm, the gametes that fertilize the ovum, the female gamete. In order to produce a zygote that is a cell that will divide and grow inside of the female reproductive tract inside of the uterus, the embryo will grow into a fetus that will eventually be delivered as the child as the baby.