BLOOD VESSELS-ARTERIES

In preparation for the upcoming quiz I want to go over arteries. Arteries are blood vessels that carry blood away from the heart. Usually it is always oxygenated blood, with the exception of the pulmonary arteries. Elastic arteries are the largest in diameter. They are also called "conducting arteries" because they help move blood through arteries due to their elasticity. An example of an elastic artery is the aorta. Muscular arteries help to move blood to different areas of the body. Because of this they are called "distributing arteries". An example of a muscular artery is the brachial artery. There are three layers (tunics ) to the artery. The inner most is the tunica interna. It is made of simple squamous epithelium, a basement membrane, and internal elastic lamina. This layer is closest to the lumen of the artery. The next layer is the tunica media. It is made up of elastic and smooth muscle fibers. The outermost layer is the tunica externa (or tunica adventitia). This layer is made up of elastic and collagen fibers. In muscle arteries only, there is a external elastic lamina which separates the tunica media from the tunica externa.
Arteries are a very important part of our bodies. Without them we would not be able to supply our bodies with blood. If someone severs an artery they could die very quickly. Nurses can put an arterial line into the radial or femoral artery to monitor blood pressure. If the reading is low, then there is not enough blood going to the arteries and an intervention needs to occur.

WHITE BLOOD CELLS

This post is a little out of order, but I want to discuss the different white blood cells (wbc's). White blood cells have a nucleus and do not contain any hemoglobin, unlike red blood cells. They can live from a few hours to a few days. Wbc's that have granules end in -phil and wbc's that don't have granules end in -cyte. Neutrophils are the most prevalent of the wbc's. They have a multi lobed nucleus and their main function is phagocytosis. They can destroy bacteria with lysozyme or hydrogen peroxide. Lymphocyctes have a large bi-concave nucleus and their function is to mediate immune responses. The T-cells attack viruses and the B-cells secrete antibodies. Monocytes are the largest of the wbc's, have a kidney shaped nucleus and have phagocytic capabilities. When they leave the blood stream they become macrophages. Eosinophils have a 2-lobed nucleus connected by chromatin. The granules are a red/orange color. They combat the effects of histamine in allergic reactions. Basophils are the least common wbc. They contain so many granules (blue/purple in color) that you cannot see the nucleus which has 2 lobes. Basophils intensify overall inflammatory response. They release heparin, histamine, and seratonin.
Cell counts are very important in my line of work. MD's will order a cbc (complete blood count) to try to detect infection, inflammation, or to monitor disease. A high or low count of any one of the categories of wbc's indicates a different condition. With my new knowledge of the different wbc's and their importance I can now understand what this test means and how to detect different disease.

BLOOD

We have begun to discuss the Cardiovascular system. This week we focused on blood. I want to explain the parts of blood and it's three main functions. Blood is a viscous fluid making it flow slower than water. It's temperature is 38 degrees Celsius and makes up 8% of our total body weight. The average male/pregnant female has 5-6L of blood and non pregnant females have 4-5 L. Blood is made up of about 55% plasma, which is a watery fluid. Within the plasma are proteins, water, and a small amount of waste products. Blood also contains 45% of formed elements. These elements are platelets, rbc's, and wbc's. The rbc's make up about 99% of the formed elements. Functions of blood include transportation, regulation, and protection. Blood transports oxygen from the lungs to the body and gases (CO2) from body cells to the lungs. It also transports nutrients to the body cells and waste products away from the cells and out of the body primarily through urination. Blood also transports hormones from the endocrine glands to other body cells. Blood helps to regulate pH (normal pH of blood is 7.35-7.45), regulate body temperature (thermoregulation), and regulate blood pressure/blood volume. Blood circulates wbc's to help "fight infection". Blood has clotting factors to prevent excessive blood loss.
I donate blood pretty regularly because I know that it can save up to three lives. I have also donated platelets, which can help people with thrombocytopenia (low platelet count). I am able to give a pint of blood in under five minutes.

ENDOCRINE SYSTEM

We just finished up studying the Endocrine system (ES). I want to discuss some of the parts of the Endocrine system and their function. The ES works with the Nervous system to help maintain homeostasis. The ES releases hormones into the blood stream to control body cells. The Pituitary gland is the "master gland" of the ES. It secretes hormones that control other endocrine glands. They hypothalamus is the "master of the pituitary gland". It is the major link between the nervous and endocrine systems. It helps to regulate the secretion of hormones from the anterior pituitary. Stimuli causes changes in hypothalamic activity. They hypothalamus regulates body temperature, hunger, sexual behavior, fear, and rage. The hormones released from the pituitary gland and the hypothalamus are very important in regulation of growth, development, and metabolism. A hormone is a molecule that is released in one part of the body to change the physiological effect of target cells in another part of the body. We discussed steroidal hormones, thyroid hormones, and Protein hormones. Steroidal hormones are lipid soluble, therefore they must use a transport protein to travel through the ECF/blood, usually Albumin. Their receptors are in the nucleoplasm or cytoplasm. The half life of steroidal hormones is slower and lasts a long time (7-10 days). They induce target cells to make proteins. Examples of steroidal hormones are Aldosterone, Cortisol, Testosterone, and Estrogens. Thyroid hormones are produced in the thyroid gland. Their secretory products are stored in large supply. They control your basal metabolic rate, increase protein synthesis, increase breakdown of triglycerides, and stimulate body growth. Examples of thyroid hormones are T3 and thyroxine. Protein hormones are water soluble, therefore they don't need to use a transport protein to travel through the ECF/blood. Their receptors are in the plasma membrane. Their effects are quicker and don't last long (hours). The effect on the proteins is to change the activity of the proteins already in the target cells (if already activated will deactivate it, if not activated will activate it). Examples of protein hormones are Oxytocin, ADH, LH, FSH, and ACTH.
The study of the ES was especially interesting to me because I just recently had my thyroid checked. My levels were high suggesting sub clinical hypothyroidism. My symptoms were fatigue, increased need for sleep, and mood swings. I was just started on Levothyroxine to help boost the production of TSH. Since beginning the medication I have noticed that I am less tired and happier. I am also hoping that it will boost my metabolism and maybe I'll lose some weight.

WEEK 4

This week in class we started to discuss the eyeball, it's parts, and their functions. There are three layers to the eye, which are sometimes called Tunics. The outermost layer is the Sclera (Fibrous Tunic), it is normally white due to its vascularity and collagen fibers. The Sclera is a continuation of the Dura Mater. The next layer is the Choroid (Pigmented Tunic), this layer is also vascular. The innermost layer is the Retina (Visual Tunic). Even though when looking at pictures of the eye, the Retina appears to have blood vessels, this layer is avascular. The blood vessels are actually in the vitreous chamber. The Iris sits atop of the Ciliary body and this is "the color" of our eyes. The pupil that appears black is actually a hole in our eye. Our Cornea is clear b/c there are no blood vessels. Our lens grows like a tree trunk, the inside 'rings' are older and when cataracts (deposits of white collagen) form, they start on these inner layers. There are six extrinsic muscles of the eyeball. The Superior Oblique moves the eye down and out and is innervated by Cranial Nerve IV (Trochlear). The Superior/Inferior/Medial Rectus'/ Inferior Oblique are innervated by Cranial Nerve III (Oculomotor). These muscles moves eyes up/down/up & out/inward. The Lateral Rectus allows the eye to move laterally and is innervated by Cranial Nerve VI (Abducens). The Ciliary muscles help us to see up close and far away. When they are relaxed we are able to see further away, when they are contracted we are able to see up close.

I find studying the eye interesting b/c it is such an important part of us. My eyes are hazel. The color of your eyes depends on how much melanin is in the Iris. My eyes must have low to moderate concentration of melanin. I couldn't imagine not being able to see. I had Lasik eye surgery a few years ago. This is when the cornea is cut and a flap is made so that the doctor can remodel it. This was a scary thing to go through b/c if it didn't work my eyesight might have become worse. Luckily it worked and I now have 20-15 vision! It was also a very interesting surgery to watch, but I suggest that if you want to have Lasik, don't watch the procedure until after!

Week 3

This week we started to discuss the brain and spinal cord in depth. I was pretty interested in the meninges. They are the protective membranes. The outermost layer is the dura mater. It is tough, thick, inflexible, vascular, and white in color. It is composed of dense irregular connective tissue. The brain has 2 layers of the dura, the periosteal layer and the meningeal layer. The spinal cord only has one layer. There are 3 extensions of the dura mater that help to separate portions of the brain; the falx cerebri, falx cerebelli, and the tentorium cerebelli. the next layer is the Arachnoid layer. It has fewer collagen fibers, areolar tissue, and more reticular/elastic fibers. The arachnoid layer is avascular. Between the dura mater and the arachnoid mater is the subdural space. The innermost layer is the Pia mater. This layer is vascular. It is very thin and clear in color. It contains collagen and elastic fibers. Between the arachnoid and pia maters is the subarachnoid space which contains CSF.
If someone gets hit in the head or back very hard they could get very sick very fast. A subarachnoid hemorrhage is when there is a bleed in the subarachnoid space. A subdural hematoma is when there is a blood clot in the subdural space. Often times when these situations occur a patient must go to the OR to remove the hematoma or stop the bleeding. Patients can also get tumors in any of the spaces in the brain and a craniotomy is performed to biopsy it or remove it.

Week 2

This week we continued to talk about the Nervous system. I want to discuss the different neuroglia of the nervous system and their functions. Astrocytes are star shaped cells. They create the blood brain barrier and also help to regulate Ca++ ions in the extra cellular fluid. Astrocytes are capable of mitosis. Oligodendrocytes form the myelin sheath of the CNS. They are able to wrap multiple axons for insulation. Although these cells are capable of mitosis, they are unable to assist in regeneration of cell. An injury to the CNS is often permanent because of this. Ependymal cells are the producers/regulators (via the cilia) of CSF. They appear cuboidal, and also are capable of mitosis. Microglia are the macrophages of the CNS. They have phagocytic/mitotic capabilities. Schwann cells are the producers of the myelin sheath in the PNS. Unlike Oligodendrocytes, Schwann cells are only able to wrap one axon. Schwann cells are capable of mitosis and use a process called Wallerian regeneration to assist in repair of an injury to the PNS. These cells form a "fatty tunnel" towards the intended targeted neurons. The axon then grows and is guided through this tunnel of schwann cells.
In my line of work I am able to see injury to both the CNS and the PNS. I never really understood why some injuries healed and some did not. Now that we have studied these different cells and how they function it is more clear. An injury to a limb is more easily repaired than recovering from a cva b/c a limb is part of the PNS and the brain is part of the CNS.

Week 1

This week we discussed some of the basic vocabulary/anatomy of the Nervous system. A neuron is the fundamental cell type of the Nervous system. Dendrites are tree like branches that form from the cell body that receive incoming impulses. An axon is long and thin and conducts impulses away from the cell body toward another neuron, muscle fiber, or gland cell. The cell body is the "house" of the cell. It contains the nucleus, cytoplasm, and many organelles. The ribosomes of the neuron are called Nissl bodies. The cell body is also referred to as the soma or perikaryon. The axon connects to the cell body via the axon hillock. This is also where action potentials are generated. The cytoplasm of the axon is called the axoplasm. At the end of the axon are the axon terminal buttons. The synaptic bulb is here and has vesicles that release neurotransmitters into the synaptic gap.
Neurotransmitters (NT) are proteins such as Acetylcholine (Ach), Dopamine, Lysine, and Seratonin. There are NT receptors embedded in the dendrite membranes. The NT on the tail of one neuron binds to these receptors on another neuron and a shape change occurs, which also changes the function of the NT. Every neuron produces one type of NT and they only bind with their like NT receptor.
I work in the ICU at EMMC and I see patients receive Dopamine. Until we had this discussion on NT's I didn't realize that Dopamine was one, I thought it was a pain medicine. If a patient has a low heart rate or blood pressure, a Dopamine drip can be started to increase them. The Dopamine works with the sympathetic nervous system to cause these changes. We have Dopamine in our systems naturally, but someone who is sick may need help producing it.