Sunday, June 24, 2012

Biological Science 8 (Circulatory, Lymphatic and Immune System)


Day 14: 

A. Circulatory System

The circulatory system delivers nutrients and building materials, and removes waste from the cells.

1. Functions (Circulation of Oxygen, Nutrients, Hormones, Ions, and Fluids; Removal of Metabolic Waste)
Circulation creates an area for diffusion to occur, like a swap-meet. The vendors are cells, the money is nutrients, the items for sale are waste, the buyers are circulation cells such as red blood cells. Nutrients are exchanged for waste in stationary cells that depend on the circulating cells to keep functioning.

  • Oxygen is taken into the body from the environment, travels to the circulatory system via the lungs, into the capillaries, where the oxygen binds to hemoglobin on red blood cells. Red blood cells travel through the body and back to the heart exchanging oxygen for waste. Oxygen is needed to make ATP though cellular respiration.
  • Nutrients are absorbed mainly by the small intestines and then transported to the blood stream. Cells such as the liver can also release nutrients into the bloodstream. Cells can uptake nutrients (some require hormones, Ex. glucose needs insulin).
  • Hormones need to travel in the circulatory system to get to their target.
  • Fluids and ions circulate making them available to cells (regulation of water and salt occurs in the kidney). Waste in the form of urea travels in the blood, to the kidney to become urine.

2. Role in Thermoregulation
Vasoconstriction conserves heat by keeping heat near the core, vasodilation cools the body by letting blood (with heat) near the surface of the body (where heat is lost to the outside enviornment).

3. Four-Chambered Heart (Structure, Function)
The heart must pump blood with oxygen to all the cells for cellular respiration to occur. The four-chambered heart does not allow oxygenated and deoxgenated blood to mix. Blood gets pumped faster and oxygen is absorbed better by the lungs. Blood travels through: the vena cava, right atrium, tricuspid valve, right ventricle, pulmonary valve, pulmonary artery, lung, pulmonary vein, left atrium, bicuspid (mitral) valve, left ventricle, aortic valve, aorta. TP-BA.

The Four Chambered Heart

4. Systolic and Diastolic Pressure
Systolic pressure = left ventricle contracts (highest system pressure)
Diastolic pressure = left ventricle relaxes (lowest system pressure)
When taking blood pressure, the first sound that is heard (when the heart's pressure surpasses the cuff's resistance) is called the first Korotkoff sound. Diastolic pressure, the left ventricle relaxes, is measured when no more sound is heard. 

Hearing Systolic and Diastolic Pressure

5. Pulmonary and Systemic Circulation
Pulmonary (the lungs) circulation: blood comes from the heart via right ventricle, into the lungs via pulmonary arteries, then back to the heart (left atrium) via pulmonary veins.

Systemic (the whole body) circulation: blood comes form the heart via left ventricle, into the body via the aorta, back to the heart via the inferior and superior vena cava into the right atrium.

6. Arterial and Venous Systems (Arteries, Arterioles, Venules, Veins)
  • Elastic Arteries: have elastic tissue, they are not active in vasoconstriction, their layers are endothelium, smooth muscle and connective tissue. 
  • Muscular Arteries: are somewhat active in vasoconstriction, have a lot of muscle and distribute blood to specific organs.
  • Arteriole: controls blood flow to capillaries, most active in vasoconstriction.
  • Capillary: single cell of endothelium, diffusion occurs between blood and tissue solutes.
  • Venule: conduct capillaries to veins.
  • Vein: have valves to prevent the back flow of blood, layers endothelium, smooth muscle and connective tissue, vasoconstriction may occur, muscle movement (muscle milking) helps blood flow back to the heart.

A. Structural and Functional Differences
Veins have anti-back flow valves, arteries have more smooth muscle (thus are thicker). Arterioles and venules are smaller versions of arteries and veins. Arteries always go away from the heart, veins go to the heart (sometime oxygenated, Ex. the pulmonary veins).

B. Pressure and Flow Characteristics
Arteries have high pressure, veins have low pressure. Veins flow evenly, arteries flow turbulently.

7. Capillary Beds
Oxygen and carbon dioxide are exchanged. Nutrients and wastes are exchanged. Heat can be lost due to dilation of capillaries in the extremities. 

A. Mechanisms of Gas and Solute Exchange
Diffusion is the main mechanism of gas and solute exchange, which is why high surface area is important at a cellular level (facilitating diffusion). 
  • Continuous Capillary: Ex. Blood-brain barrier (seals clefts by tight junctions) and skin and muscle, no pores on endothelial cells, may have clefts. 
  • Fenestrated Capillary: Ex. Small intestines, endocrine organs, kidneys (allow blood filtration), pores allow fluid out, but not blood cells.
  • Sinusoidal Capillary: Ex. Lyphoid tissue, liver, spleen and bone marrow, large pores allow blood cells to leak out, facilitation their travel.

B. Mechanism of Heat Exchange
Capillaries expand in the extremities to give off extra heat (they constrict to save heat in cold environments). More warm blood near the surface of the body causes greater heat loss to the outside environment. Counter current exchange of heat occurs in the kidneys of mammalia, not sure how much this affect humans...

8. Composition of Blood
55% plasma (top layer), 44 % red blood cells (no nucleus, bottom layer), 1% white blood cells (middle layer with platelets). White blood cells: 60% neutrophils, 40% T and B lymphocytes.

A. Plasma, Chemicals, Blood Cells
There are water molecules, ions, gases, hormones, wastes, nutrients and clotting factors in the blood plasma. Chemicals in blood include clotting factors or hormones. Blood cells can be red blood cells (erythrocyte), that carry oxygen and carbon dioxide or white blood cells (leukocyte), that fight pathogens. Platelets are not cells, but are fragments of huge cells used for clotting.

B. Erythrocyte Production and Destruction (Spleen, Bone Marrow)
The bone marrow has stem cells that make myeloid stem cells, which then make erythrocytes. The spleen, liver and bone marrow destroy damaged erythrocytes. Iron is recycled, heme turns into bilirubin, then bile and is excreted in the feces, globin is broken down into amino acids to be reused.

C. Regulation of Plasma Volume
The volume of fluid in the body is regulated by sensing the blood osmolarity (which is why drinking too much water really fast can kill you). Osmolarity is kind of like stickiness, (it really refers to amount moles of dissolved contents, but usually that makes a fluid more thick or sticky). Higher blood osmolarity causes water to flow naturally (through osmosis) out of the cells and into the blood, to dilute the blood. That results in higher blood volume, lower interstitial volume. Low blood osmolarity causes water to flow into the tissues and interstitial space, lowering blood volume. 

Vasopressin/Antidiuretic Hormone (ADH) keeps fluid in the body by preventing urination and reabsorbing more water in the kidneys (the exact opposite of a "water pill"/diuretic, that causes frequent urination). Aldosterone causes increased salt reabsorption, which causes the same effect as ADH, greater water reabsorption in the kidney and thus higher blood volume.

Day 15:

D. Coagulation, Clotting Mechanisms, Role of Liver in Production of Clotting Factors
Clotting is a positive feedback mechanism. Clotting, leads to more (not less) clotting. Platelets are sticky pieces of megakaryoctyes, they contain enzymes for clotting. Clotting factors are produced in the liver (fibrinogen), which then circulates in the blood plasma. When a wound occurs, the platelets pile up onto it (platelet plug) and release chemicals that activate the fibrinogen. The fibrinogen follows are series of reactions becoming fibrin (a mesh that seals the clot during coagulation. Retraction and repair occur as the clot contracts (the clot dissolves after the wounded blood vessel is repaired).

9. Oxygen and Carbon Dioxide Transport by Blood
Transport of oxygen and carbon dioxide in the blood is carried out by red blood cells, which contain hemoglobin to bind the gases to the protein.

A. Hemoglobin, Hematocrit

  • Hemoglobin is the molecule in red blood cells that carries oxygen. Each red blood cell has millions of hemoglobin molecules. 
  • Hematocrit is the percentage of blood that is made red blood cells (by volume).

B. Oxygen Content
Each hemoglobin can have up to four oxygen molecules (one for every iron atom). 

Hematocrit (the percent of blood that is red blood cells and can carry oxygen) is normally 40-50% for men, 36-45% for women.

C. Oxygen Affinity
The more oxygen binds onto hemoglobin, the easier it is for more oxygen to bind due to a relaxed conformation of the other subunits. Carbon monoxide binds to hemoglobin better then oxygen, ruining red blood cells in cases of carbon monoxide poisoning (the blood still looks bright red). 

10. Details of Oxygen Transport: Biochemical Characteristics of Hemoglobin
Hemoglobin contains 4 heme groups (which contain iron), allowing up to 4 molecules of oxygen to bind to hemoglobin (allowing transport to cells for cellular respiration). Carbon dioxide is also transported by hemoglobin as well as nitric oxide. Hemoglobin is famous for having a quaternary structure composed of 4 protein subunits in a tetrahedral arrangement.

A. Modification of Oxygen Affinity
Conditions of stress (high temperature, low pH, and high carbon dioxide) cause lowering of oxygen affinity to hemoglobin, thereby allowing it to be delivered to cells that need it.

B. Lymphatic System

The lymphatic system probably describes the chi. Chi is the commander of blood, blood is the mother of chi. The bloods leaking fluid creates the lymph, the lymph cleans the fluid and returns it to the blood. Chi stagnation is the root of illness, as is lymphatic stagnation.

According to the Lymphatic Research Foundation: 
"The well being of every individual depends on the health of the lymphatic system.... The lymphatic system plays an integral role in the immune functions of the body. It is the first line of defense against disease. This network of vessels and nodes transports and filters lymph fluid containing antibodies and lymphocytes (good) and bacteria (bad). The body's first contact with these invaders signals the lymphatics, calling upon this system to orchestrate the way the infection-fighting cells prevent illness and disease from invading microorganisms."

1. Major Functions
  • Blood, interstitial and lymph fluid balance.
  • Transport of molecules too large to fit in blood capillaries (fat and protein) to the veins.
  • Immune function (lymphocytes produced in the bone marrow live inside lymphoid tissue (growing and changing), such as lymph nodes, the thymus, tonsils, Peyer's patches and various organs. The lymphocytes kill foreign invaders that pass through the lymph nodes and lymph fluid.

A. Equalization of Fluid Distribution
Blood fluid pressure is higher then interstitial fluid pressure, therefore it leaks out through capillary pores into interstitial space if that fluid has higher pressure than the lymph, it will flow into the lymphatic capillaries, if not the lymph vessel flaps close preventing lymph back flow. Lymph fluid will rejoin the blood in the subclavian veins completing the cycle.

B. Transport of Proteins and Large Glycerides
The small intestines have lymph capillaries called lacteals, fat gets absorbed there. Fat is transported in the lymph system to the subclavian veins, and then liver, because it is too large for capillaries. Fat and plasma proteins are transported via the lymph.

C. Return of Materials to the Blood
Water, proteins, ions and fats are returned to the blood at the subclavian veins.

2. Composition of Lymph (Similarity to Blood Plasma; Substances Transported)
The same as interstitial fluid to begin with, but picks up lymphocytes and proteins as it flows through lymph nodes. Transports metastatic cancer cells, returns protein and interstitial fluid to circulation, brings fat from the digestive system to the blood. 

The name lymph came from the roman god of fresh water Lympha.
Lymph is the same as blood plasma, but without plasma proteins, which are too large to go through the capillaries pores. No red blood cells or platelets either.

3. Source of Lymph (Diffusion from Capillaries by Differential Pressure)
Blood plasma from capillaries leaks out (since there are fenestrations/openings), becoming lymph. The lower pressure of the lymph and higher pressure of the capillary drives the diffusion. The path is blood, to interstitial fluid, to lymph, back to blood.

4. Lymph Nodes (Activation of Lymphocytes)
Lymph nodes contain lymphocytes that are activated when foreign antigens enter the lymph node, this causes proliferation (chemical release), antibody production and cytokine release.

C. Immune System: Innate and Adaptive Systems

The immune system protects us from and causes disease. Rheumatoid arthritis is an example where the immune system attacks the body (at the joints).

1. Cells and their Basic Functions
The cells of the immune system are the leukocytes (white blood cells). 

The Cells of the Immune System

  • Bone marrow pluripotent stem cells form either 1) myeloid precursors (end up as phagocytes, basophils or eosinophils) or 2) lymphoid precursors (end up as lymphocytes). The myeloid stem cells make red blood cells, megakaryocytes (form platelets), monocytes (become macrophages and dendritic cells) or polymorphonuclear leukocytes (eosinophils, basophils and neutrophils) and mast cells. While lymphoid stem cells, form T cells, B cells and natural killer cells.
  • T-lymphocytes (from the Thymus), cytotoxic T cells kill infected cells via apoptosis, and helper T cells signal for macrophages, T and B cells, both recognize antigens on infected cells.
Helper T Cell Function

Cytotoxic T Cell Funciton
  • B-lymphocytes (from the Bone Marrow) plasma cells (secrete antibody when exposed to antigen), and memory cells (waiting for the same antigen to attack again in the future).
  • Natural killer cells (increased count as a result of massage) kill cancer/abnormal cells. 
  • Phagocytes (macrophages, dendritic cells and neutrophils) eat foreign invaders, clean debris and dead cells .
  • Macrophages and dendritic cells present antigens.
  • Eosinophils kill multicellular parasites.
  • Basophils fight ticks (and other ectoparasites) and help regulate T cells, as well as being involved with allergic inflammation.
  • Mast cells are also involved with allergies, they are the attacker in rheumatoid arthritis and multiple sclerosis, the benefit of mast cells is they activate the bodies immune response when under bacterial attack.

A. Macrophages, Neutrophils, Mast Cells, Natural Killer Cells, Dendritic Cells (Innate/Nonspecific Immunity)
The mast cells cause inflammation and alert the body to attack, the neutrophils kill invaders, the macrophages and dendritic cells both kill and present antigens of invaders (for T and B lymphocytes to memorize).

B. T Lymphocytes (Specific Immunity)
The T lymphocytes recognize antigens, cytotoxic T cells kill the invading cells via apoptosis, helper T cells call for back up by signaling for macrophages, T and B cells to come kill the invading cells.

C. B Lymphocytes, Plasma Cells (Specific Immunity)
The B lymphocytes alert the immune system using antibodies. Plasma cells secrete antibodies when exposed to an antigen.

Day 16:

2. Tissues
The main tissues associated with the immune system are the thymus tissues (T cell mature), the bone marrow (B cells mature), the lymph nodes and the spleen tissues.

A. Bone Marrow
Blood cells are made in the bone marrow, B lymphocytes mature here (thus the name).

B. Spleen
The spleen removes old red blood cells from circulation, also removes platelets allows white blood cells to hang out and grow. The fetal spleen makes blood cells. Removes bad stuff from the blood.

C. Thymus
T cells mature in the thymus (thus the name).

D. Lymph Nodes
White blood cells also hang out here (can't always hang out in the spleen). The lymph nodes are like blind canyons, trapping pathogens for the white blood cells to kill. When the white blood cells of the body notice antigens, they signal the immunological alert.

3. Basic Aspects of Innate Immunity and Inflammatory Response
Innate immunity means non-specific immunity. The first time a pathogen enters the body it only has innate immunity and inflammation to kill the pathogen. The next time it knows the tricks, habits and appearance of the pathogen and the body will have specific immunity as well as innate immunity and inflammatory response. 

  • Skin is part of innate immunity; the thick oily kerainized outer layer is like a rain jacket, the bacteria and friends (flora) that live on our skin keep other stuff from having room to live there.
  • Mucus membranes are part of innate immunity; the mucus traps pathogens physically preventing them from moving like a fly trap, cilia they "bounces" the pathogen out of the body.
  • White blood cells (the phagocytes anyways) are part of innate immunity; the swallow and kill pathogens, like snakes.
  • Natural killer cells are part of the innate immunity; I'm not going to explain what they do the pathogens...
  • Antimicrobial proteins: lyse (slice up) bacteria, interfere with virus replication, and complement (punch a hole in) pathogen membranes. In summary if attached by a bacteria, a virus and a fungus, the antimicrobial proteins slice up the bacteria, pierce the fungus and cock block the virus.
  • Fever and Inflammation are part of innate immunity; heat helps white blood cells function better, inflammation causes more white blood cells to go to the site of infection by sending out chemical signals and making capillaries more permeable.

4. Concepts of Antigen and Antibody

  • Antigen: Key
  • Antibody: Lock
  • Antigens and antibodies are used for specific immunity, also called adaptive immunity. 
  • Antigen presenting cells kill invaders then display their antigen on their surface, like a warrior displaying a decapitated head on a spike. 
  • Antigens are recognized by T and B cells. The cyctotoxic T cells see the antigen and go kill the invaders with that antigen. 
  • Helper T cells call for help when they see an antigen. They call macrophages, cytotoxic T and B cells. 
  • B cells produce antibodies, which not only make pathogens easier to find but also, kill pathogen by putting holes in their membranes (complement activation), making them easier to eat (opsonization) and making pathogens unable to sick to a host cell (neutralization) keeping them in circulation where white blood cells are hunting them.

5. Structure of Antibody Molecule
Antibodies are Y shaped (contain two light chains and 2 heavy chains linked together by disulfide bonds, the tips of the fork (called the hypervariable region) bind to a specific antigen.

6. Mechanism of Stimulation by Antigen; Antigen Presentation
The mechanism of stimulation by antigen varies based on if the pathogen is extracellular or intracellular. An extacellular pathogen will be eaten by a macrophage, pieces of it get displayed on the surface of the macrophage, helper T cells call the alarm when they see the pieces, allowing the macrophages to destroy the pathogen and B cells to make antibodies that can also destroy the pathogen. An intracellular pathogen invades a host cell, pieces of the pathogen end up on the cell membrane, cytotoxic T cells recognize the pieces (antigens) and cause the infected cell to self-destruct.

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