Anatomy and Physiology of the Human Body

In this lesson on anatomy and physiology, we will discuss the relationship between these two subjects. While they can be studied separately, I believe they are best understood when studied together. Anatomy focuses on the form, structure, and location of bodily parts. For example, let's consider the pericardium, which is the sac that surrounds the heart. The term "pericardium" is derived from "cardia" or "cartium," which means heart, and "per" which usually means around or surrounding. The pericardium is made of connective tissue and is slightly larger than the heart itself. It is located right here, providing some anatomical facts about the pericardial sac. On the other hand, physiology is more concerned with the function of bodily parts and the processes involved. It explores how different organs are connected and what each organ is doing in relation to others. Taking the pericardium as an example again, it serves as a protective and lubricating layer for the heart. The fluid inside the sac acts as lubrication for the beating heart, similar to how oil is necessary for the proper functioning of moving engine parts. The pericardial sac plays a vital role in maintaining the health and function of the heart.

The pericardium is associated with physiological facts related to the heart and its protection. Understanding the composition of the body's parts is crucial, starting with the building blocks of matter. All molecules in the body are made up of atoms, which are the fundamental units. While subatomic particles like protons and electrons are occasionally discussed, atoms are the main focus in this course. The different kinds of atoms on Earth are known as elements, and the periodic table of elements from a chemistry course provides information about each element's smallest functional unit, which is an atom. In the human body, the most abundant atoms are oxygen, carbon, and hydrogen, but there are also others like nitrogen, calcium, sodium, and phosphorus. These atoms have a nucleus consisting of protons and neutrons, with electrons orbiting around the outside. When atoms combine, they form molecules, and there are various common molecules found in the human body.

H2O, commonly known as water, is a molecule composed of two hydrogen atoms and one oxygen atom. On the other hand, CO2 refers to carbon dioxide, which is a compound consisting of one carbon atom and two oxygen atoms. When we exhale, we release CO2, while also including O2, which is oxygen. The key difference between the oxygen present in the atmosphere and the oxygen we breathe in is that the latter is the gas that our bodies utilize for aerobic respiration in our cells. Oxygen, as a gas, typically exists as two oxygen atoms bonded together through a covalent bond. However, when we combine a larger number of atoms, we form macromolecules, which are large molecules. These macromolecules, also known as organic compounds, are primarily carbon-based and play a crucial role in life. Examples of macromolecules include carbohydrates (sugars), proteins, DNA, and RNA. These molecules consist of numerous atoms and serve as the fundamental building blocks of life. When we assemble carbohydrates, proteins, fats, DNA, and other such molecules in a functional manner, we can create organelles. Organelles can be thought of as the microscopic cell's organs, as they are the working components that enable a cell to sustain its life. One well-known organelle is the nucleus, which acts as the cell's brain and control center, storing DNA and facilitating genetic expression. Another important organelle is the ribosome.

The ribosome, composed mainly of proteins and fragments of RNA, functions as the cell's protein factory. In addition to the ribosome, another essential organelle is the mitochondria, also known as chondrion in its singular form. The mitochondria serve as the powerhouse of the cell, responsible for generating energy to support cellular functions. Properly arranged organelles form cells, which are the fundamental units of biology and the basis of anatomy and physiology. Within cells, various types of cells exist, such as red blood cells (RBCs), which are produced and lost at an astonishing rate of at least a million per second. Neurons, the building blocks of the nervous system, make up the brain, spinal cord, and nerves. Macrophages, on the other hand, are cells found in tissues that engulf and destroy foreign invaders like bacteria and viruses. When cells are organized and serve a collective purpose, they form tissues, such as those found in the human body.

The epidermis refers to the outermost layers of your skin, which primarily consist of dead cells. These layers are constantly shed, and you lose thousands and thousands of them every day. However, your body replenishes them, so there's no need to worry. Another example of a tissue is the cerebral cortex, which is the outermost superficial layer of the brain. This thin layer, just a few millimeters thick, is highly active and developed in humans compared to other animals.

Now, let's talk about the mucosa. The term mucosa is derived from mucus, and it is used to describe the inner lining of organs that secrete fluids or aid in digestion. For instance, the mucosa is the innermost layer of the stomach, which contains glands responsible for producing digestive enzymes. Speaking of organs, the stomach itself is composed of various tissues that play a crucial role in the digestive system. While the heart is a well-known organ, there is another lesser-known organ called the thymus. The thymus is located behind the breastbone, near your sternum, and it plays a vital role in supporting your immune system.