KIN 3304 1nd EditionExam #3 Study Guide Lectures: 18 - 21Chapter 23: The Lymphoid System – pg. 607The Vaccine Wars Link: http://video.pbs.org/video/1479321646/ Lecture 18 (October 13) The Lymphatic System has several components:- Lymph – the fluid connective tissue transported by this systemo Consists of: Interstitial fluid, that resembles blood plasma but with less proteins Lymphocytes  Macrophages- Lymphatic vessels – the vessels that carry lympho Originate in the peripheral tissueso Deliver lymph to the venous systemo Run parallel to blood vessels- Lymphocytes – the cells in the liquid o Responsible for immune response- Lymphoid Organs – produce lymphocytes- Lymphoid Tissues – adjust the composition of lymphThere are lymph nodes found throughout the body and they are easily palpable during infectionand disease. Exercise can help the immune system.There are 3 primary functions of the Lymphoid System: 1. Produce, maintain, and distribute lymphocytes2.Maintain normal blood volume and eliminate variations in the chemical composition of the interstitial fluid3.Provide an alternate route for the transport of hormones, nutrients, and waste products 1.Lymphocytes are produced within the spleen, thymus, and bone marrow. There are primary and secondary classifications. The thymus and the bone marrow are the primarylymphoid organs. Although in mice, the spleen is considered primary.a. Primary lymphoid structures are the thymus and the bones marrow. They are responsible for developing and maturing lymphocytes. So T cells originate in the bone marrow and then go to the thymus to get educated.b. Secondary lymphoid structures are where most immune responses begin. This is where lymphocytes divide to produce more of the same type. Secondary structures are located at the front lines where invading bacteria are first encountered such as lymph nodes and tonsils.Thymus: - Is at its maximum size during puberty and decreases in size thereafter. The functionalcells are replaced by connective tissue fibers. This degeneration process is called involution. - Involution increases susceptibility to novel pathogens.- It has a blood-thymus barrier that is similar to BBB and prevents leakage of cells. - It is separated into 2 thymic lobes, a right lobe and a left lobe. The septa divided the thymus into little compartments known as lobules. The lobules contain an outer cortex and a central medulla. o The outer cortex is where lymphoid stem cells divide rapidly that produce daughter cells that mature and migrate to the medulla. During maturation, any daughter cells that are too sensitive to normal antigens are destroyed because it is highly selective and about 2% survive selection.- There is such thing as a nude mouse that has no thymus, which means no immune system. - SCID – severe combined immunodeficiency in which an example is the bubble boy that had no protection.Spleen:- Largest lymphoid organ- Attached to the stomach by the gastrosplenic ligament- 3 Functionso Removes abnormal blood cells through phagocytosiso Stores iron by recycling broken down red blood cellso Initiates immune responses by B cells and T cells2. The BP at the proximal end of a systematic capillary is ~35 mm Hg and this BP forces water and solutes out of the plasma and into the interstitial fluid. About 3.6 L/day of blood volume enters the interstitial fluid each day. This helps put H2O back into the blood supply.a. Lymphedema is when a lymphatic vessel is blocked, or if it is damaged. Drainage will slow or even stop which leads to swelling. This is why some people wear sleeves to pump fluid.3. It also functions as an alternate route for hormones, nutrients, waste, immune cells, cytokines, and etc. For example, lipids absorbed by the digestive tract will be carried to the blood stream by lymphatic vessels versus being absorbed across capillaries.Lymphatic Capillaries form a complex network within the peripheral tissues. They differ from vascular capillaries in several ways:- They are larger in diameter- They have thinner walls because their endothelial cells lack a continuous basal lamina- They have an irregular outline- They have anchoring filaments that help keep passageways open during increasing pressure.- They have overlapping endothelial cells that are not tightly banded that act as a one-way valveLymphatic Capillaries absorb interstitial fluid and dissolved solutes, but they also absorb any viruses or anything abnormal such as bacteria or cell debris that are present in damaged or infected tissues. This is why lymphatic capillaries contain evidence about the health of the surrounding tissue.There are two types of Lymphatic Collecting Vessels. - Superficial Lymphaticso Travel with superficial veins and are found in these locations: In the subcutaneous layer next to skin In the loose connective tissue of mucus membranes that line the digestive, respiratory, urinary, and reproductive tracts. In the loose connective tissues of serous membranes that line the pleural,pericardial and peritoneal cavities.- Deep Lymphaticso They accompany the deep arteries and veins.o They collect lymph from skeletal muscles and organs**TQ: Know the distribution of lymphoid tissues and lymph nodes:- Cervical LN: monitor lymph of the head and neck- Axillary LN: filter lymph arriving at the truck from the upper limbs. In women, the axillary nodes also drain lymph from mammary glands- Popliteal LN: filter lymph arriving at the thigh from the lego Inguinal LN: monitor lymph arriving at the trunk from the lower limbs- Thoracic LN: receive lymph from the lungs, respiratory passageways, and mediastinal structures- Abdominal LN: filter lymph arriving from urinary and reproductive system- The lymphoid tissue of Peyer’s Patches, the intestinal LN and the mesenterial LN: receive lymph originating from the digestive tractLymphomas are malignant tumors that consist of cancerous lymphocytes or lymphocytic stem cells. There are about 61,000 cases per year in the US and is very common in dogs.- Hodgkin’s Diseaseso Accounts for 1 of 7 lymphoma cases. It is common in the ages of 15-35 and over 50. The reason for this pattern is unknown. Even though the cause of this diseaseis unknown, an infectious agent (probably a virus) may be involved.- Non-Hodgkin’s Lymphoma (NHL)o This is when there are abnormalities in chromosomes (85% of the time, NHL is associated with