THE LYMPHATIC SYSTEM
What exactly is this System?
- Which organs are involved?
- What is the function of the Lymphatic System?
- How does it work?
Jobs of Lymphatic System:
Lymphatic System which consists of vessels and organs plays two vital roles in our lives:
- The vessels essentially maintain interstitial fluid levels by carrying excess fluids as well as any plasma proteins, back into the CVS.
- The organs, house critical immune cells such as lymphocytes which carryout our body defense against infection and disease as well as offer ACQUIRED IMMUNITY .
- Lymph – excess tissue fluid carried by lymphatic vessels ( general definition)
- Properties of lymphatic vessels
- One way system toward the heart
- No pump
- Lymph moves toward the heart
- Milking action of skeletal muscle
- Rhythmic contraction of smooth muscle in vessel walls
Composition of Lymph
- Lymph is usually a clear, colorless fluid, similar to blood plasma but low is protein
- Its composition varies from place to place; after a meal, for example, lymph draining from the small intestine, takes on a milky appearance, due to lipid content.
- Lymph may contain macrophages, viruses, bacteria, cellular debris and even traveling cancer cells.
- Edema is the excess accumulation of fluids in tissue spaces. This can retard normal exchange of nutrients and metabolites. Filtration of the extracellular fluid exceeds drainage. Anything that causes increased capillary pressure, such as decreased plasma protein, increased capillary permeability or lymphatic blockage, can result in swelling and congestion of the extravascular compartment.
- Lymph Capillaries
What Type of Vessels Make up the Lymphatic System?
- The vessels are called lymphatics.
- They are thin-walled and are analogous to veins.
- Small lymphatics are similar to capillaries only more porous; Larger vessels are called collecting vessels: both have valves.
- 2 large Ducts: Right LYMPHATIC DUCT and THORACIC DUCT (BOTH EMPTY INTO THE RT AND LT SUBCLAVIAN VEINS)
- Lymph flows only TO THE HEART (ONE WAY).
- This is a low-pressure, pumpless system. Lymph moves via skeletal muscles and pressure changes in thorax during breathing only.
Lymph Carries …
- Harmful materials that enter lymph vessels
- Cancer cells
- Cell debris
- Then Lymph Nodes take the germ-filled lymph and
- Filter lymph before it is returned to the blood
- Defense cells within lymph nodes
- Macrophages – engulf and destroy foreign substances
- Lymphocytes – provide immune response to antigens
The Lymphatic System
- Consists of two semi-independent parts
- Lymphatic vessels
- Lymphoid tissues and organs
- Lymphatic system functions
- Transport fluids back to the blood
- Play essential roles in body defense and resistance to disease
- A Lymph Node- Important lymphocytes of the immune response are matured here.
- Spleen: DESTROYS RBCs and Resevoir of Blood; IT IS THE LARGEST Lymph organ and it filter blood of bacteria and antigen-filled cells.
- Thymus Gland-produces hormone, thymosin, functions in programing lymphocytes T and B cells; T-cells matured here ( become immunocompetent)
- Tonsils-Traps bacteria and other microbes in throat.
- Peyer’s Patch-capture and destroy bacteria in intestine, thereby preventing them from penetrating the intestinal wall.
Lymph Node Structure
- Most are kidney-shaped, less than 1 inch long
- Outer part
- Contains follicles – collections of lymphocytes
- Inner part
- Contains phagocytic macrophages
Anatomy of a Lymph Node
- Fluid enters afferent vessels
- Exists efferent vessels
- Germinal center of follicle – These enlarge during time of plasma cell production (B Cells)
- Medulla- Phagocytes are located here
- Filters blood of bacteria, viruses and other debris
- Destroys worn out blood cells. It then returns (or recycles) some of the breakdown products of RBCs to the liver ..for example Fe, so that more RBCs can be made .The unusable portion of worn-out blood is excreted in bile.
- Another function: Stores platelets and acts as a blood reservoir.
- Lymphocytes are produced; RBCs also made in fetus only.
Body’s Defense System:
Physical and Chemical
Skin – largest organ of the body
- Skin Flora
- Sweat and Sebum
Mucous membranes on inside:
- in gut
- in lungs
- Inflammatory response
- Immune response
White blood cells, also called leukocytes, are continuously made in the bone marrow White Blood Cells.
There are a variety of leukocytes and they are all derived from hematopoietic stemcells. Leukocytes specific for immunity are called lymphocytes