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Ch. 22 Lymphatic System/ Immunity
Resistance Lymphatic System/ Function Lymphatic Vessels and Lymph Circulation
Terms in this set (25)
Disease producing organisms
- Microscopic - viruses, bacteria, fungi, etc
The ability to ward off diseases
Vulnerablility or lack of resistance
2 areas of resistance
Defense mechanisms that provide general protection against invasion by a wide range of pathogens
- Mechanical Barriers - skin, mucus membranes
- Antimicrobial chemicals
- Specific Resistance
- Involves activation of specific lymphocytes that combat a particular pathogen or other foreign substance
- The body system that carries out the immune response is the lymphatic system
The Lymphatic Syst consists of
2. Lymphatic vessels (lymphatics) - that transport lymph
3. Structures and organs that contain lymphatic (lymphoid) tissue
4. Bone marrow which houses stem cells that develop into lymphocytes
The difference between Interstitial Fluid and Lymph
- They are basically the same
- Major difference is LOCATION
- Fliud from interstitial tissue becomes lymph after it passes from interstitial space to lymphatic vessels
- Lymphatic tissue is a specialized form of reticular connective tissue (blood) that contains large number of lymphocytes
Functions of the Lymphatic System
1. Fluid Balance - Lymphatic vessels drain tissue spaces of excess interstitial fluid.
2. Fat Absorption - Lymphatic system absorbs fats and other substances from the digestive tract. Fats enter the lacteals (special lymphatic vessels located in the small intestine) and pass through the lymphatic vessels to the venous circulation
3. Defense - Microorganisms and other foreign substances are filtered from lymph by lymph nodes and from blood by the spleen (lymphocytes)
(A type of white blood cell found in lymph nodes), aided by macrophages (phagocytic cell derived from a monocyte), recognize foreign cells and substances, microbes, and cancer cells.
2 basic reponse methods to foreign cells
T Cells (lymphocytes) - destroy the intruders directly (by causing them to rupture) or indirectly by releasing cytotoxic (cell-killing) substances
B Cells (lymphocytes) - differentiate into plasma cells that secrete antibodies.
Proteins that combine with and cause destruction of specific foreign substances
- Begin as closed-ended vessel called lymphatic capillaries in spaces between cells.
- Lymphatic vessels resemble veins in structure but have thinner walls and more valves.
- At intervals, have structures called lymph nodes
- In the skin, lymphatic vessels lie in subcutaneous tissue and generally follow veins
- Vessels of the viscera generally follow arteries, forming plexuses around them
- Microscopic vessels in spaces between cells from which lymphatic vessels origiate
- Unit to form large tubes called lymphatic vessels; just as blood capillaries unit to form venules and veins
- Permits interstitial fluid to flow into them but not out
The organs inside the ventral (anterior) body cavity
Where capillaries are NOT found
1. Avascular tissue (bloodless)
2. Central Nervous System
3. Splenic pulp
4. Bone marrow
Attach lymphatic endothelial cells to surrounding tissues.
Fingerlike projection (villi) of the small intestine contains blood capillaries and a specialized lymphatic capillary called
Formation and Flow of Lymph
- Most components of blood plasma freely move through the capillary walls to form interstitial fluid
- More fluid seeps out of blood capillaries by filtration than returns to them by absorption
- The excess fluid, about 3 liters per day, drains into lymphatic vessels and becomes lymph.
- Lymph drains into venous blood through the right and left lymphatic ducts at the junction of the internal jugular and subclavian veins
Right and Left Lymphatic Ducts
Lymph drains into venous blood through the right and left lymphatic ducts at the junction of the internal jugular and subclavian veins
Sequence of Fluid Flow
Arteries (blood plasma) -> Blood capillaries (blood plasma) -> Interstitial spaces (interstitial fluid) -> lymphatic capillaries (lymph)-> Lymphatic Vessels (lymph) -> Lymphatic Ducts (lymph) -> Subclavian Veins (blood plasma)
Proteins in Fluid Flow
- Since most plasma proteins are too large to leave blood vessels, interstitial fluid contains only small amounts of protein
- Any protein that do escape, however, cannot return to the blood by diffusion
- (The concentration gradient (high level of proteins inside blood capillaries, low level outside) prevent diffusion back to the blood)
Lymph Flow Factors
1. Contracting of the skeletal muscle (milking action)
2. One-way valve (similar to those found in veins) within the lymphatic vessels prevent backflow of lymph.
3. Breathing movement. With each inhalation, lymph flows from the abdominal region, where the pressure is higher, toward the thoracic region, where it is lower.
From the most proximal group of each chain of nodes, the exiting vessels unite to form lymph trunks
Principal Lymph Trunks
1. Lumba trunk
2. Intestinal trunk
3. Bronchomediastinal trunk
4. Subclavian trunk
5. Jugular trunk
These trunks pass into 2 main channels => Thoracic (Left Lymphatic) Duct and Right Lymphatic Duct which pass lymph into the venous blood
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