Lymphatic System
Consists of Lymph, Lymphatic Vessels, Lymphatic Tissues + Red Bone Marrow.
Lymphatic System
-functions with the cardiovascular system for the delivery of nutrients to the tissue cells and the removal of metabolic waste products from the tissues.
-lymphatic system is a 1-way system (unlike the cardiovascular system)
-arises in the tissues and extends towards the heart
-its vessels and organs return the lymphatic fluid from the tissues to the blood circulation for reuse
Immune System is closely related to the Lymphatic System
Immune Ststem...
responsible for the body's response to foreign microorganisms and molecules
-operates through the cells of the lymphatic system
-products of the immune system are usually carried in the lymphatic vessels and in the blood.
Function of the Lymphatic System
...to return fluid (lymph) to the circulator system from the intercellular tissue spaces
1. Drains excess interstitial fluid.
2. Transports dietary lipids.
3. Carries out immune responses.
3 Primary Functions of Lymphatic System
1. Drains excess interstitial fluid. Lymphatic vessels drain excess interstitial fluid from tissue spaces and return it to the blood.
2. Transports dietary lipids. Lymphatic vessels transport lipids and lipid-soluble vitamins (A,D,E, and K) absorbed by the GI tract.
3. Carries out immune responses. Lymphatic tissue initiates highly specific responses directed against particular microbes or abnormal cells.
Lymphatic Vessels
Lymphatic capillaries are found throughout the body except in avascular tissues, the CNS, portions of the Spleen, and Bone Marrow
Lymphatic Vessels
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Sequence of Lymph Fluid Flow
1. Blood Capillaries (blood)
2. Interstitial Spaces (interstitial fluid)
3. Lymphatic Capillaries (lymph)
4. Lymphatic Vessels (lymph)
5. Lymphatic Ducts (lymph)
6. Juntion of the Internal Jugular & Subclavian Veins (blood)
**Lymph flows one way - From the TISSUES to the HEART
Lymphatic System as it relates to the Circulatory System
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Spleen Functions
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Edema
An accumulation of fluid in the interstitial spaces.
Lymphatic Capillaries
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Thoracic Duct
Largest Lymphatic Vessel in the body
-arises in the abdominal cavity
-proceeds up to the thorax - anterior to the vertebrae and dorsal to the esophagus
-as it nears the neck, the thoracic duct turns to the left and empties its contents into the base of the left subclavian vein.
Right Lymphatic Duct
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Thoracic (Left Lymphatic) Duct
-begins as a dilation called the cisterna chyli anterior to the 2nd lumbar vertebrae
-this is the main duct for the return of lymph to blood.
Cisterna Chyli
Collects lymph from:
-right + left lumbar trunks
-intestinal trunk
The thoracic duct also receives lymph from the left jugular, left subclavian, and left bronchomediastinal trunks
Right Lymphatic Duct
Receives Lymph from:
-right jugular
-right subclavian
-and right bronchomedistinal trunks
Both Thoracic (Left) & Right Lymphatic Ducts...
Drain into venous blood at the junctions of their respective internal jugular and subclavian veins
Recap
-Cistern Chyli - 2nd lumbar vertabrae
-Lumbar Trunks - lower limbs, wall + viscera of pelvis, kidneys, adrenal glands, abdominal wall
-Intestinal Trunk: stomach, intestines, pancreas, spleen, and part of the liver
-Bronchomediastinal Trunks: thoracic wall, lung, and heart
-Subclavian trunk: upper limbs
-Jugular Trunk - head and neck
How Lymph Flows
-unlike blood circulation, the lymphatic system does not have a pump
it moves slowly by:
-muscular contraction (exercise!)
-pressure changes from breathing
-valves
Lymphatic Ducts
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Principal Organs of the Lymphatic System
1. Lymphatic Vessels
2. Lymph Nodes
3. Spleen
4. Thymus
Lymphatic Vessels
Carry lymph from peripheral tissues to the veins of the cardiovascular system
Lymph Nodes
-Monitor the composition of lymph;
-site of cells that engulf pathogens;
-immune response
Spleen
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Thymus
Controls development & maintenance of T-lymphocytes
Afferent Lymphatic Vessels
Bring lymph TO a lymph node
Efferent Lymphatic Vessels
Drain lymph nodes
Afferent vs. Efferent
Afferent lymph nodes bring lymph to a lymph node.
Efferent ones drain the lymph node
Lymph Nodes
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Afferent Lymphatic Vessels
Vessels that ENTER lymph nodes
Efferent Lymphatic Vessels
Vessels that EXIT lymph nodes
T-Lymphocytes & B-Lymphocytes
-Lymph nodes contain these 2 types of cells.
-they are the basic underpinnings of the body's immune system.
Two distinct regions of the lymph nodes
cortex & medulla
Cortex
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Lymph Sinuses
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Medulla
The central region of the lymph node containing fewer lymphocytes
Group clusters of Lymph Nodes
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Location of Lymph Nodes
They prevail in the tissues of the:
-neck (cervical lymph nodes)
-groin (inguinal)
-bend of the elbow (cubital fossa)
-behind the knee (popliteal fossa)
-armpits (axillary lymph nodes)
-mediastinum (thoracic region between the lungs)
Additionally:
-they follow the course of large blood vessels in the abdominal cavity & body's appendages
Tonsils
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Tonsils
-tonsils are aggregates of lymph node tissue located under the epithelial lining of the oral and pharyngeal cavities.
-'tonsil' usually refers to the palatine tonsils - located at the surface of the palatine bone.
-other tonsils include that massive tissue known as the pharyngeal tonsil (also called adenoids) at the roof of the pharynx, and the lingual tonsils found in the tissue of the tongue
Palatine Tonsils
Located at the surface of the palatine bone
Pharyngeal Tonsil (Adenoids)
mass of tissue at the roof of the pharynx
Lingual Tonsils
found in the tissue of the tongue
Peyers Patches
Nodules of lymphoid tissue found in the wall of the intestinal tract.
Thymus
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Functions of the Spleen
1. Reservoir of lymphocytes.
2. Filters blood.
3. Storage depot for blood.
4. Contains B & T-lymphocytes for immune response.
**Remember: Old RBC components are recycled in the Spleen & LV
Spleen
-a lymphatic organ because its functions are consistent with those of the lymphatic system & its cells are lymphatic cells.
-located in the upper portion of the abdominal cavity, inferior to the diaphragm, and on the left side.
-shape of the spleen conforms to the structures it contacts
-the spleen is convex where it touches the diaphragm + concave in 3 places where it contacts the left kidney, stomach, + large intestine
-hillus = area where large blood vessels + turn + leave the spleen
-like lymph nodes, the Spleen is surrounded by a capsule of connective tisue which extends inward to divide the organ into numerous smaller regions/lopes (lobes?) consisting of cells and small blood vessels.
-lymphocytes are packed densely in the cortex, but less so in the medulla
-blood enters the spleen by way of the splenic artery.
Splenic Artery
Blood enters the spleen this way
Spleen's Functions
1. Reservoir of Lymphocytes for the body.
2. Filters Blood
3. Important in RBC and Iron metabolism because macrophages in the spleen phagocytize old and broken RBC's and recycle the iron by sending it to the liver.
4. It serves as a storage depot for blood
5. contains B & T lymphocytes for the immune response
Lymph
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Lymph of the GI tract...
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Laceals
lymph vessels in the intestinal wall
Edema
An accumulation of fluid in the interstitial spaces between the cells
-Edema can occur if the lymphatic vessels are blocked, such as an infection.
-Edema also occurs if there is a delay in blood movement within the veins or as blood accumulates in the veins
-the escape of protein into the intercellular spaces, such as during inflammation, is another possible reason for edema.
-protein draws water out of the vessels by osmosis, and the water contributes to the swelling.
Drainage
The swelling will reduce as the accumulated interstitial fluid flows to the lymph. Find the cuase! Fix the cause.
Innate Defenses
First Line of Defense - Provides physical and chemical barriers against external pathogens
First Line of Defense
Physical Factors & Chemical Factors
Physical Factors
Skin, Mucus Membranes, Mucus, Hairs, Cilia, Lacrimal Apparatus, Saliva, Urine, Defecation, and Vomiting
Chemical Factors
Sebum, Lysozyme, Gastric Juice and Vaginal Secretions
Skin
Provides physical barrier to entrance of microbes.
Periodic shedding of epidermal cells also removes microbes at skin surface
Mucus
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Lacrimal Apparatus
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Saliva, Urine, Defecation & Vomiting
Expel/Washes Away Microbes
Sebum
Acidic film over skin that inhibits growth of many microbes
Vaginal Secretions/Saliva
Creates slightly acidic environment that inhibits growth of bacteria
The Immune System
-Stem Cells arise in Bone Marrow
-Lymphopoietic Cells (Lymph Stem Cells) can follow either of these 2 courses:
- Become T-Lymphocytes
or
-Become B-Lymphocytes
T-Cells
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B-Cells
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Immune System Function
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Development of the Immune System
-Develops in the 3rd month after conception
-At this stage of fetal development a set of primitive cells called stem cells arise in the bone marrow.
-Certain stem cells form forerunners in the immune cells called lymphopoietic cells.
-these cells follow either of 2 courses of development:
1)Become T-Cells/T-Lymphocytes - by passing through the Thymus
-modified and receptor molecules are placed on the surface of the cells.
-T-Cells migrate through the circulation and come to rest in the lymphoid tissues such as the spleen, tonsils, and lymph nodes - where they control the immune system.
2) B-Cells/B-lymphocytes
-organs responding to B-cells are the bone marrow, liver, and lymph node tissues in the GI Tract
-during formation B-Cells synthesize antibodies and position them on their cell membranes.
-these antibodies will later act as receptor sites + react with foreign substances during the immune response.
Recap - Origins of Immune System
-Stem cells (hemocytoblasts) in the bone marrow give rise to lymphopoietic cells which take either of two courses:
-some pass through the thymus and are modified to form T-lymphocytes
-Certain T-lymphocytes return to the bone marrow to participate in the immune reaction, but most proceed to the peripheral tissues where they congregate.
-Other lymphopoietic cells are modified to form B-lymphocytes and natural killer cells.
-the B-lymphocytes also migrate to the peripheral tissues to join the T-lymphocytes.
-the lymph nodes and spleen are major depositories of T-lymphocytes and B-lymphocytes
Immune Cells + their functions
1) Leukocytes - White Blood Cells
-Neutrophils - engulfing & elimination
-Basophils - inflammation
-Eosinophils - destroy worms; hypersensitivity reactions
-Monocytes - engulfing
-Lymphocytes - specific immune responses
(a) B Cells - recognize foreign antigens; secrete antibodies to guide attack
(b) Cytotoxic T Cells - recognize + attack cancerous + infected cells
(c) Helper T Cells - helps activate B cells and cytotoxic T cells (**attacked by HIV)
(d) NK Cells - kill cells with guidance from antibodies.
2) Plasma Cells - make and secrete antibodies
3) Macrophages - engulf invading particles
4) Mast Cells - trigger inflammatory response
Inflammation
An attempt to dispose of microbes/toxins/foreign material at the site of injury, to prevent their spread to other tissues and to prepare the site for tissue repair to restore tissue homeostasis.
-A non-specific, defensive response of the body to tissue damage.
-Conditions that cause inflammation include: pathogens, abrasions, chemical irritations, distortion/disturbance of cells and extreme temperatures
-Characterized by redness, pain, heat, and swelling.
-May cause loss of function - eg. inability to detect sensation
3 Stages of Inflammation
1) Vasodilation and increased permeability of blood vessels
2) Emigration (movement) of phagocytes from blood to interstitial fluid
3) Tissue Repair
Vasodilation
-Allows blood to flow through damaged area, thus helping to remove microbial toxins and dead cells to facilitate arrival of defensive proteins such as antibodies and clotting factors.
-Increased permeability allows more 2-way passage of substances in and out of vascular system around damaged areas.
-eg. antibodies and clotting factors in, dead cells and toxins out.
-this allows more blood to flow through a damaged area thus helping to remove microbial toxins and dead cells and to facilitate arrival of defensive proteins such as antibodies and clotting factors.
Vasodilation & Increased Permeability of Blood Vessels:
-Produce Heat, Redness & Swelling
-heat & redness is due to large amounts of blood that accumulates in damaged area.
-swelling results from the movement of more fluid from blood plasma into surrounding tissue spaces.
-pain results from injury to neurons and from toxic chemicals released by microbes; some of the substances that induce vasodilation; and due to increased pressure from swelling
Emigration (movement) of phagocytes from blood to interstitial fluid
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Abscesses
Formed when pus cannot drain out of an inflamed region. (eg. pimples + boils)
Ulcers
Occurs when superficial inflamed tissue sloughs off the surface of an organ or tissue causing an open sore.
Fever
-occurs during infection + inflammation - many bacterial toxins elevate body temperature
-Initial Stage: hypothalamus resets body's thermostat at a higher level - cold + shivery, no sweating, blood vessels constrict to keep heat inside (hence pale complexion), skin may be hot to touch.
-Elevated body temperature inhibits the growth of some microbes and speeds up body reactions that aid repair.
-Subsequent stage: fever breaks, profuse sweating as body seeks to lower its temperature again.
-During sweating, toxins produced by infection agents and other toxins are excreted along with viruses.
**Sheets of bed-ridden patients should be changed after a bout of sweating so that they are not surrounded by the very toxins the body is trying to get rid of
Antigens
-a substance (usually a large protein) that has the ability to provoke an immune response by stimulating the production of antibodies
-all body cells display surface protein molecules known as MHC for 'major histocompatibility'
-Antigens enter the body through a variety of portals, including tiny openings in the mucous membranes of the respiratory tract and openings in the skin when it is penetrated by a wound.
Antigens
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The Immune Response
-Foreign organisms are approached by phagocytes
-Macrophages (engulfing + digesting microorganism)
-Antigen displayed on the MHC molecules
-MHC molecules identify the macrophages as normal body cells
-Macrophage enters lymph node + encounters T4 cell
-Lymphokines (reactive protein) released and stimulates either B or T-lymphocyte
-Immune system diverges into cell-mediated or antibody-mediated immunity
*Remember: MHC molecultes display antigens to stimulate specific T + B lymphocytes in the immune response
Immune Response
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Cell-Mediated Immunity
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Natural Killer Cells (NKC)
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Suppressor T-Lymphocytes (T8 Cell)
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Cell-Mediated Immunity
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T-Lymphocyte Activation
In cell mediated immunity, antigens react only with those T-lymphocytes having the complimentary antigen receptor
Antibody-mediated immunity
-depends on the activity of B-lymphocytes
-binding of antigen and antibody activates (commits) the B-Lymphocytes
-B-lymphocytes divide and clones produce antibodies
-Antigen can be produced at a rate of 2000 per second
-other substances (like milk, bee venom, ragweed) can also stimulate a specialized an immune reaction = allergy
*Remember: antibodies tag antigens for removal from the body
Antibody-mediated immunity
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