Anatomy and Physiology
Session 1 - Introduction
To understand anatomy and physiology we first have to understand the basic concepts of each and how they differ.
To understand anatomy and physiology we first have to understand the basic concepts of each and how they differ.
Anatomy - the branch of science concerned with the bodily structure of humans, especially as
revealed by dissection and the separation of parts.
To understand anatomy and physiology we first have to understand the basic concepts of each and how they differ.
Anatomy - the branch of science concerned with the bodily structure of humans, especially as
revealed by dissection and the separation of parts.
It is important to note that anatomy and physiology is NOT this:
The things we will cover will be based on these general definitions, but there are some specifics
that we will also delve into. This includes anatomical structures, endocrinology,
physiological processes before, during, and after labor and birth, and organ systems.
All of this relies on what we call a systems approach. The body is made up of these
various systems, and together they all function with one another to carry on the different
The systems of the body go well beyond this particular course, but we will specifically
look at the endocrine, respiratory,
cardiovascular, reproductive, and some of the muscular and skeletal systems.
We will start with the cardiovascular system in a general overview. It will help us to form a
foundation on many of the things we will be covering later in this course.
In specific terms, the cardiovascular system is a part of the circulatory system. The other part is the lymphatic system which will not be discussed
in any sort of depth. As the name implies, the lymphatic system moves lymph and is tied together in the lymph system and lymph nodes.
The cardiovascular system is much more closely related to maternal and child health as it
comprises the heart, veins and arteries, blood, and the filters (lungs and kidneys) and the brain.
The first piece of the puzzle is the blood. Blood is a fluid that is made up of several main parts:
red blood cells, white blood cells, plasma, and platelets. Together these form the main
Plasma is yellowish in color and is the majority of the entire blood volume. It contains the structure of the blood, meaning that it helps to hold all the other pieces of blood in place. It is also the major
Red blood cells are the main carrier of oxygen to the rest of the body. They are comprised of many
different components, but the one that we are concerned with is an iron-rich substance called hemoglobin. This is a substance able to bind to
Hemoglobin can carry up to four oxygen molecules. The more oxygen it carries, the
brighter red it becomes. This is why oxygenated blood looks bright red and depleted hemoglobin
looks blue. The truth is that it is not blue but actually very, very dark red that appears blue
There are about 2.4 million new red blood cells produced every second in an adult human.
Almost half of the entire blood volume is made of red blood cells and 25% of all cells in the human body are red blood cells. They are created in the
bone marrow and live about 120 days. No picture...they are too small to see, but
White blood cells are also known as leukocytes. They are the immune aspect of blood and their job
is to fight disease and foreign invaders. Making up only about 1% of the total blood volume, you will die without them. Leukocytes are classified into different categories: neutrophils, eosinophils,
When you get a blood draw and ask for a CBC, they will report back different things to you. One of
these is the types of leukocytes found in the blood and their levels. This lets you know what is
happening and gives a strong clue as to why it is happening. For instance, large monocyte activity
The WBC, or white blood cell count, in a healthy adult is reported as 4,000 – 11,000 per microliter
or, 4 X 109/L – 11 X 109/L
Platelets are the wound-closers in the blood.
Their function is to stop bleeding if possible. They fail to do this when the cut is too big or there are too few platelets. They will cling to the edge of a
wound and secrete a clotting factor that binds other platelets together and eventually forms a
Platelets can cling to places that are not actually cuts, however. An example is arterial plaque. This can lead to stroke if the plaque gives way. Another problem is abnormal arterial walls where
Adult humans have around 6 quarts of
blood (5.7 L). This blood circulates in a closed loop through a system of arteries, veins, and
capillaries. About 2,000 gallons of blood circulates in your body each day, traveling through over
The human heart is a pump that pushes the blood around the body, taking oxygen and nutrients as well as other body constituents to the cells. It has
four chambers, two that deal with the depletion loop and two with the enrichment loop.
When the lungs breathe in air they will pull oxygen out of the air and diffuse it into the blood. This
blood is now enriched with oxygen and is circulated to the heart. When blood has been depleted of its oxygen stores it heads back to the
When oxygenated blood reaches the heart it is shunted to the second loop. Two chambers then send this blood around the body where it delivers oxygen and nutrients and so forth, returning to the
heart depleted and crossing back into the first loop. So to recap, four total heart chambers are
We tend to think in circulation that blood starts in the arteries and goes to the veins and finally into capillaries, then back to veins and returns to the
The blood actually goes from the heart to the
arteries and then to the capillaries The capillaries empty into the veins and the veins back to the
arteries. This makes sense because the
capillaries are the small vessels that lead into tissue, bringing oxygen and nutrients. The blood
As the red blood cells travel through the
capillaries there is an oxygen partial pressure differentiation taking place. This means that there
are areas where the content of oxygen in the blood plasma is lower. The hemoglobin gives up
its oxygen molecules to regulate the pressure. Now the capillaries have a higher pressure than the tissues surrounding the capillaries. Oxygen
The diffusion of nutrients and hormones into the cells is done in a similar way. While the blood cells themselves do not carry these nutrients or hormones, they are released into the bloodstream
and carried along in the structure of plasma, diffusing through the cell wall plasma along the
This journey of the circulatory system gives us a glimpse of how and why we are able to move blood, oxygen, nutrients, and hormones through the body. Next we will look at the production and
distribution of hormones in the system and the roles they play in pregnancy and development.