Saturday, April 16, 2011

What is our Immune System and how does it work?

Immune System in our bodies serves the defense mechanism and can be divided into first, second and third line of defense. It is a complicated body system and shares an analogy to a nation (country), the Border Patrol, the Immigration system, the Army, the Navy, the Air Force, the Marines, the Special Forces, the Secret Service, the CIA, the NSA, the FBI, the Police, the detectives and other security personnel along with all their training academies. The prime purpose of our Immune System is to deter, defend and thwart any attack on any of the body systems including itself. It utilizes both non-specific and specific defense mechanisms and uses very sophisticated organic hardware (Skin - as a barrier along with its shedding mechanism, water resistance, Langerhans cells, many anti-microbial secretions including peroxide; Mucosal barrier - with saliva containing anti-microbial lysozyme, and secretory antibody IgA; Cell-mediated Immune system including all the different types of White Blood Cells; Humoral Immune system including Immunoglobulins  and the Complement system and the Lymphatic System with its organs - lymph nodes, lymph vessels, spleen, thymus, tonsils) along with the  adaptive software (genetic material - DNA).

This brief overview and analogy can easily make us understand how our Immune System works and learns about our body's internal and external environment and keeps it from changing and getting damaged until it works normally.

The battle-grounds inside the body are the sites of injury and the way our immune system responds to it and are referred to as sites of inflammation that result in swelling, redness, heat, pain, sometimes total or partial loss of function. Depending on the nature of injury and the type of forces deployed by the body to fight these battles with foreign agents (antigens and haptens combined with body proteins) the inflammation might be acute (over a short period of time and usually severe), sub-acute (less severe and more insidious than acute), chronic (long standing and not severe) or acute on chronic(severe and on top of a long standing injury).

Injury in our bodies can take various forms and helps us understand the nature and cause of various disease processes and syndromes.

An easy way to remember most of these causes is to remember the mnemonic:


V - Vascular (Heart, Blood vessels, Bone Marrow and the Blood itself)
I - Infections (Bacterial, Viral, Fungal, Protozoans, Parasitic)
N - Neoplasia [new growths: Benign (non-cancerous) and Malignant (cancerous) and Nervous System (Brain disease, Psychiatric and Psycho-social, Spinal cord and Nerves)]
D - Dietary, Drugs (medications and substance abuse) and Developmental
I - Iatrogenic (Illness caused by medical examination or treatment) and Idiopathic (unknown cause) and Immune system
C - Congenital (condition present at birth)
A - Autoimmune (Immune system fails to differentiate between self and non-self and starts attacking our own body)
T - Trauma
E - Endocrine (Hormonal) and Environmental

M - Metabolic (Genetic Inborn errors of metabolism and problems with chemical reactions in the body)
E - Eating Habits and Exercise (lack of) and Education (lack of)

Video Links:

Thursday, April 14, 2011

The Lymphatic System

Watch these two videos about the lymphatic sysyem and we will discuss these in class on monday.

Monday, April 11, 2011

Blood and its components

Blood (about 8% of total body weight) is a specialized type of connective tissue which has the liquid portion called the plasma (roughly about 55% of the whole blood) and the solid portion (about 45%) known as formed elements.

The formed elements are mainly the Erythrocytes (Red blood corpuscles or cells or RBCs), Leucocytes or Leukocytes (White blood corpuscles or cells or WBCs) and the Thrombocytes (Platelets). The formed elements of the blood are formed in the red bone marrow in adults mainly found in the ends of long bones like the femur, humerus, and flat bones like the skull bones, sternum, ribs, hip bone etc. In fetus and neonate the blood formation (hemopoiesis) also goes on in the liver and spleen.

The bone marrow which constitutes about 4% of the total body weight in adults is mainly of two types: Red bone marrow (hematopoietic) and the Yellow bone marrow (fat cells and stem cells).

The Plasma, by itself, is straw-yellow in color is aqueous (watery) solution of water (92% of plasma is water) and proteins (roughly close to the rest of the 8% of plasma) and traces of other materials. Plasma contains proteins (Albumin - mainly a carrier protein; Globulins alpha, beta and gamma types- gamma globulins  are Immunoglobulins which are antibodies,  20 types of complement proteins also used for defense), electrolytes (Na+, K+, Cl-, HCO3-  etc), glucose and traces of other sugars, amino acids, other organic acids, cholesterol, and other lipids, hormones, clotting factors, fibrinogen, urea and other wastes.

The Erythrocytes or the RBCs are mainly involved in the transport and exchange of O2 (Oxygen) and CO2 (Carbon dioxide) in the lungs and in the tissues. RBCs appear red and give the human blood its red color due to the presence of a red pigment carrier protein called Hemoglobin. Each hemoglobin molecule can bind to 4 molecules of oxygen. After binding with oxygen it’s called oxyhemoglobin which gives the oxygenated blood its bright red color.

The Leukocytes are divided into two categories bases on the presence of granules (Granulocytes) or the absence of granules (Agranulocytes). The Granulocytes are further divided into three types based on the dye that they pick up on being stained using the Hematoxylin and Eosin stain (H&E). The cells that appear blue after picking up the Hematoxylin stain (blue in color) are called Basophils. The ones that stain Lilac, red or pink shades are called Eosinophils. The ones that stay neutral to the dye and stay clear are called Neutrophils. The Agranulocytes are of two types Lymphocytes and Monocytes.