The Lymphatic System; The Immune System

Question 1

The lymphatic system

Answer 1

Collects excess interstitial fluid and returns it to the blood. Proteins and large particles that cannot be taken up by the capillaries are removed by the lymph system. The pathway to the blood takes the excess fluid through lymph nodes, which are well prepared to elicit an immune response if necessary.

Thus, the lymph system recycles the interstitial fluid and monitors the blood for infection. In addition, the lymph system reroutes low soluble fat digestates around the small capillaries of the intestine and into the large veins of the neck. Most tissues- except those of the CNS- are drained by lymphatic channels.

Question 2

Open system

Answer 2

The lymph system is an open system (fluid enters at one end and leaves tat the other). Lymph circulates one way through the vessels, eventually dumping into the thoracic duct and the vena cava. To enter the lymph system, interstitial fluid flows between overlapping endothelial cells. Large particles literally push their way between the cells into the lymph. The cells overlap in such a way that, once inside, large particles cannot push their way out.

Note that fluid returns to the blood at the right lymphatic duct and the thoracic duct.

Question 3

Blood

Answer 3

The blood is connective tissue, meaning it contains cells and a matrix. Blood regulates the extracellular environment of the body by:
transporting nutrients, waste products, hormones, and even heat. Blood also protects the body from injury and foreign invaders.

Question 4

Important proteins contained in plasma

Answer 4

Albumin: transport fatty acids and steroids, also act to regulate the osmotic pressure of the blood

Immunoglobulin: aka antibodies

Clotting factors like fibrinogen

These are formed in the liver. Gamma globulins that constitute antibodies are made in the lymph tissue. An important function of plasma proteins is to act as a source of amino acids for tissue protein replacement.

Question 5

Blood composition

Answer 5

Plasma, buffy coat (made of white blood cells), red blood cells

The percentage by volume of red blood cells (hematocrit) is about 35-50%, and higher in men than women.

Question 6

Serum

Answer 6

Plasma in which the clotting factor fibrinogen has been removed

Question 7

Erythrocytes

Answer 7

Red blood cells. “Like bags of hemoglobin”. Their job is to deliver oxygen and remove carbon dioxide.

Erythrocytes have no organelles, not even a nucleus (so they don’t reproduce or undergo mitosis), but have lots of space to carry oxygen.

Squeezing through capillaries wears out their plasma membranes in about 120 days. Senescent (deteriorated) red blood cells are found in the spleen, or in smaller quantities in the liver.

Question 8

Leukocytes

Answer 8

White blood cells. Protect the body from foreign invaders.

Question 9

Stem cell

Answer 9

All blood cells differentiate from stem cell precursors in the bone marrow.

Erythrocytes lose their nucleus while still in the marrow. After entering the blood stream, they lose the rest of their organelles within 1-2 days.

Question 10

Granular leukocytes

Answer 10

AKA granulocytes: types of white blood cells that include neutrophils, eosinophils, basophils. With regards to staining: neutrophils are neutral to acidic and basic dyes, eosinophils stain in acid, and basophils stain in base.

Granulocytes remain in the blood only 4-8 hours before being deposited in the tissues, where they live for 4-5 days.

Granulocytes function nonspecifically against all infective agents. They multiply quickly against any infection, and then die once the infection is gone.

Question 11

Agranular leukocytes

Answer 11

Types of white blood cells that include monocytes, lymphocytes, and megakaryocytes. Once deposited in the tissues, monocytes become macrophages and may live for months or years. Lymphocytes may also live for years.

Agranulocytes work against specific agents of infection, and need to hand around in case the same infective agent returns.

Question 12

Platelets

Answer 12

Small portions of membrane-bound cytoplasm torn from megakaryocytes. Platelets are similar to tiny cells without a nucleus. They contain actin and myosin, residuals of the Golgi and the ER, mitochondria, and are capable of making protaglandins and some important enzymes. It’s membrane is designed to avoid adherence to healthy endothelium while adhering to injured endothelium.

When platelets come into contact with injured endothelium, they become sticky and begin to swell, releasing various chemicals and activating other platelets.

The coagulation process involves many factors, starting with platelets and including the plasma proteins prothrombin and fibrin.

Healthy individuals have many platelets in the blood.

Question 13

Innate immunity includes

Answer 13

1. Using skin as a barrier to organisms and toxins,
2. Stomach acid and digestive enzymes to destroy ingested organisms and toxins,
3. Phagocytotic cells, and
4. Chemicals in the blood

Question 14

Inflammation

Answer 14

Injury to tissue results in inflammation, which includes dilation of blood vessels, increased permeability to capillaries, swelling of tissue cells, and migration of granulocytes and macrophages to the inflamed area.

Histamine, prostaglandins, and lymphokines are just some of the causative agents of inflammation released by the tissue.

Part of the effect of inflammation is to wall off the affected tissue and local lymph vessels from the rest of the body, impeding the spread of infection.

Question 15

Two types of acquired immunity

Answer 15

Humoral (b-cell), cell-mediated (T-cell).

Question 16

Humoral immunity

Answer 16

Promoted by B lymphocytes. Differentiate and mature in the bone marrow and the lover. Each B lymphocyte is capable of making a single type of antibody (aka immunoglobulin) which it displays on its membrane.

If the B-lymphocyte antibody contacts a matching antigen (presented by a macrophage), the B lymphocyte, assisted by a Helper T cell, differentiates into plasma cells and memory B cells.

Humoral immunity is effective against bacteria, fungi, parasitic protozoans, viruses, and blood toxins.

Question 17

Antibody

Answer 17

AKA immunoglobulin. An antibody recognizes a foreign particle, called an antigen.

The portion of the antibody that binds to an antigen is highly specific for that antigen.

The antigenic determinant is removed removed by the antibody can only stimulate an immune response if the individual has been previously exposed to the full antigen.

Macrophages present the antigenic determinants of engulfed microbes on their surfaces.

Once bound, antibodies begin a cascade of reactions involving complement proteins that cause the antigen bearing cell to be perforated. The antibodies may mark the antigen for phagocytosis by macrophages and NK cells. They may cause the antigenic substances to agglutinate or may block chemically active portions.

Question 18

Plasma cells

Answer 18

B lymphocytes differentiate into plasma cells and memory B cells.

Plasma cells synthesize free antibodies and release them into the blood.

Question 19

Agglutinate

Answer 19

To be rejected

Question 20

Primary response

Answer 20

The first time the immune system is exposed to an antigen is known as the primary response. Requires 20 days to reach full potential.

Question 21

Secondary response

Answer 21

In the case of reinfection, Memory B cells can be called upon to synthesize antibodies, resulting in a faster acting and more potent effect called the secondary response. The secondary response requires ~5 days to reach full potential.

Question 22

Memory B cells

Answer 22

B lymphocytes differentiate into plasma cells and memory B cells.

Memory B cells proliferate and remain in the body. In the case of reinfection, each of these cells can be called upon to synthesize antibodies, resulting in a faster acting and more potent effect called the secondary response.

Question 23

Cell mediated immunity

Answer 23

Involves T-lymphocytes. Differentiate into helper T cells, memory T cells, suppressor T cells, and killer T cells (cytotoxic T cells).

Cell mediated immunity is effective to kill infected cells.

Question 24

T-lymphocytes

Answer 24

Mature in the thymus. Have an antibody like protein at their surface that recognizes antigens (just like B lymphocytes!). However, T lymphocytes never make free antibodies. They are tested against self-antigens in the thymus. If the T-lymphocyte binds to the self-antigen, that T lymphocyte is destroyed. If it does not bind, it is released to lodge in lymphoid tissue or circulate between the blood and the lymph fluid.

Question 25

T-lymphocytes that are not destroyed differentiate into:

Answer 25

1. Helper T cells: assist in activating B lymphocytes, as well as killer and suppressor T cells
2. Memory T cells: Have a similar function to memory B cells
3. Suppressor T cells: Play a negative feedback role in the immune system
4. Killer T cells (aka cytotoxic T cells): bind to the antigen carrying cell and release perforin, a protein which punctures the antigen carrying cell. Killer T cells can attack many cells because they DO NOT phagocytize their victims.

Question 26

Course of a bacterial infection

Answer 26

Inflammation.

Macrophages, then neutrophils, engulf the bacteria.

Interstitial fluid is flushed into the lymphatic system, where lymphocytes wait in the lymph notes.

Macrophages process and present the bacterial antigens to B lymphocytes.

With the help of helper T cells, B-lymphocytes differentiate into memory cells and plasma cells.

Memory cells wait in case of secondary response.

Plasma cells produce antibodies, which are released into the blood to attack the bacteria.

Question 27

A single B lymphocyte…

Answer 27

Produces only one antibody type.

Question 28

Blood types

Answer 28

Blood types are identified by their A and B surface antigens.

Type A blood means that the red blood cell membrane has A antigens and does not have B antigens. If the erythrocytes have A antigens, the immune system does not make A antibodies.

Type O blood has neither A nor B antigens, and makes both A and B antibodies.

A blood donor may donate blood only to an individual that does not make antibodies against the donor blood.

The genes which produce the A and B antigens are codominant. An individual with type A or B blood may be heterozygous OR homozygous. An individual with type O blood has 2 recessive alleles.

Question 29

Rh factors

Answer 29

Surface proteins on red blood cells first identified in Rhesus monkeys. Individuals having genotypes that code for nonfunctional products of the Rh gene are said to be Rh-negative. All others are Rh-positive.