 So the second theme is one that hopefully you're familiar with because you have taken some general biology and it's a characteristic of all living systems. They are built in hierarchical levels. And in this class and in human physiology, we will be looking at different levels of organization. We'll be looking at the structures of the different levels and we'll be looking at the function of the different levels. So let's just review the levels of organization. I'm having some adventures in tech land. So the biggest level of organization that we're going to deal with in this course is the level of the organism. And that's probably, that says organism is just going to have to be patient with my lovely handwriting. It's the critter. It's the human critter in this class. We're not talking about any other organisms in here except for humans in human anatomy. The organism, we can look at organismal structure and function and we absolutely will. We also, the organism itself is made up of organ systems or body systems. And we're going to look at the organ systems in detail in the next theme because the organ systems actually work together to maintain the organismal function. Organ systems are cardiovascular system which includes the heart, nervous system which includes the brain, digestive system which includes your lovely tummy, stomach, come on, we're in an anatomy class. You can imagine that the organ systems that are working together are made up of organs. I guess you're not really imagining that. That sort of is how it is. So different organs in the nervous system, you have the brain as an organ. You also have the spinal cord. That's an organ that is functioning to work together with an organ system. The organs are actually made up of tissues. And I think we probably should do some definitions. Maybe I'll give you the entire list and then we'll look at the definitions for these things. Tissues, I just got to tell you straight up and down on the real, the study of tissues is histology. And if you already purchased your textbooks for the class, you know that you have an entire histology textbook for this class. We do gross anatomy, which is the structures that you can touch and you can see usually organ level of organization, organ system level of organization. But we also pull out those microscopes frequently and look at the tissue level of organization. And tissues are made up of cells. Cells, if you remember, are the first level of organization where we have characteristics of life. We're going to talk about the level of detail of cell structure that we're going to know for this class. Not a huge amount of detail. You'll get more of that in human physiology. But, dude, cells are incredibly diverse and you think of your little like round cell with its little nucleus in it. We've got some weird cells going on and we're going to look at those in the next lecture when we do an intro to histology and tissues. Cells are made up of organelles. Interestingly, that says organelles. Organelles and organs, for some reason people get them confused. Organelle, little organ, found inside a cell with a smaller level of organization than cells. And organelles, as you know, are made up of biomolecules. And remember, biomolecules, proteins, carbohydrates, nucleic acids, and lipids. And biomolecules are made up of just regular molecules. Water, carbon dioxide, oxygen, biomolecules are just more complex. Biomolecules are usually, what's the word like? Hierarchical. They actually are built of little units. For example, I don't know what I'm trying to say, but proteins are made of amino acids. What are those things? Like the functional unit of a protein is an amino acid. The building blocks. The building blocks of these biomolecules are molecules like amino acids. Okay, the molecules are made up of atoms. And we know atoms are actually not individual things. Atoms are actually divisible. They're made up of subatomic particles. But for our purposes today, let's just kind of keep it here. Anatomy, we're going to spend a lot of time in histoland talking about tissues. Because tissues are made of cells, we will spend some time looking at cells and identifying different cells. But a huge amount of our time is spent on organs and organ systems. We will provide perspective of overall organismal function. But knowing where you are in this hierarchy will actually be really helpful. In human physiology, most of the time is spent at the cellular level. And the biochemical processes that are happening at the cellular level that inform function at the organ and organ system level. So getting comfortable with this as we work through human anatomy, I think it will be really helpful for you. Moving on to the very next fun one, which is a theme that is... we're going to get to look at all the body systems together.