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Lymphatic and Immune System

Anatomy of Lymphatic tissues, vessels, and organs Descriptions of the first and second lines of defense
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Lymphatic system
is a system of organs, glands, and ducts that work synonymously with the immune system to fight against pathogens.
Functions of the Lymphatic System
1. fluid recovery
2. immune defense
3. lipid absorption
Fluid recovery
15% of blood that is not reabsorbed by venous return will travel through the lymphatic system to be cleansed and returned to normal circulation
Lipid Absoprtion
lymphatic ducts are permeable to lipids.
absorbs lipids that were not picked up by capillaries and moves into lymphatic ducts.
Immune Defense
1. filters harmful agents
2. synthesizes specialized immune cells
Components of the Lymphatic System
1. Ducts
2. Vessels
3. Organs
Lymph
1. tissue fluid not reabsorbed by capillaries
2. clear and colorless fluid
3. low in proteins
4. contains macrophages, lymphocytes, cellular debris, bacteria, viruses, hormones that regulate fluid, and lipids.
5. mechanism for transport of mobile cancer cells.
6.
Drainage of Lymph
1. flows through lymphatic ducts,filtered, and recirculated into normal circulation
2. drains from small ducts to large ducts, like venous return
3. maintains homeostasis
Lymphatic Capillaries
1. contains large intercellular clefts that allow fluid to pass through
2. located in all tissues of the body
Places where Lymphatic Capillaries do not exist
CNS
cartilage
bone
bone marrow
cornea of the eyes
Collecting Vessels
1. run parallel to blood vessels
2. contain endothelial sacs that act as valves to prevent fluid backflow
3. passes through multiple lymph nodes
6 Lymphatic Trunks - collect fluid
1. Jugular
2. Subclavian
3. Bronchomediastinal - upper chest cavity
4. Intestinal - abdominal cavity
5. Intercostal - drains thoracic cavity
6. Lumbar - drains lower limbs
Collecting Ducts
large ducts that merge with Lymphatic Trunks
2 types
Rt. Lymphatic Duct and Thoracic Lymphatic Duct
drains fluid into subclavian veins for recirculation
Causes in Lymphatic Flow
pressure in lymphatic vessels are low
1. skeletal muscle pump
2. thoracic pump
3. suction at venous return - at subclavian veins
4. movement of arteries - contraction puts pressure against vessels
Nk Cells
- "natural killers"
- performs immune surveillance
- attacks bacteria, host cells, cancer cells, and transplant tissue cells.
Macrophages
- differentiated monocytes
- large cells
- vacuum cleaners
- phagocytize bacteria, cellular debris, dead cells, and cancer cells
B-Lymphocytes
- immune responder
- made in bone marrow
- produces Plasma cells
Plasma Cells
responsible for production of antibodies
T-Lymphocytes
carry out immune response and immune memory
Dendritic Cells (Langerhans Cells)
- live in mucous membranes, skin, and lymphatic organs
- like macrophages that work by receptor mediated endocytosis
Reticular Cells
stationary cells found in stroma of lymphatic tissues
APCs (Antigen Presenting Cell)
- in macrophages, dendrocytes, and some B and T cells
- consume antigens and show fragments (Epitopes) on the surface to help other cells identify pathogens
Lymphatic Tissues
- clusters of NK cells, Macrophages, Reticular cells, B and T cells, Dendritic Cells, and plasma cells in stroma
- located throughout the body
Diffused Lymphatic Tissue
clusters of lymph cells throughout
Permanent Lymphatic Nodules located?
- ileum of small intestine
- lymph nodes
- tonsils
- appendix
Temporary Lymphatic Nodules (raised surfaces)
- appears during infection and will dissipate when infection is over
Primary Lymphatic Organs
1. Thymus
2. Red Bone Marrow
Secondary Lymphatic Organs
1. Spleen
2. Lymph nodes
3. Tonsils
Function of Primary Lymphatic Organs
- training ground for immune cells like T-cells and B-cells
- provides protection against infection while immune cells mature
Thymus
- soft spongy organ located in the mediastinum just superior to the heart
- surrounded by fibrous tissue capsule
- contains lobules, where T-cells mature
- contains Reticular Epithelial cells
- produces hormones and molecules for immune response
Lobules
ingrowths within tissue
Reticular Epithelial Cells
form blood thymus barrier to protect against pathogens
Lifespan of the Thymus
1. during adolescence - it involutes (shrinks) and becomes fibrous
2. in old age - replaced with fatty and fibrous tissue
Red Bone Marrow
- loose organized soft tissue within bones
- ↑ vascularity
- makes formed elements and B-cells
- allows B-cells to mature
Lifespan of Bone Marrow
- turns into yellow marrow as you age
- if injured yellow marrow may turn back to red bone marrow
- in old age, turns into gelatinous marrow
Where do adults contain bone marrow?
ribs
pelvic bones
in humeral and femoral heads
sternum
Functions of Secondary Organs
1. Immune response
2. house B-cells and T-cells
Lymph Nodes
- several hundred bean shaped organs measuring 3cm long
- varies from person to person
- located all over
- divided by fibrous capsule
- contains stroma
- can move mobile cancer cells all over the body
Components of Stroma In Lymph Nodes
1. Reticular cells
2. Dendritic Cells
3. Macrophages - 99%
4. B and T cells
Locations where lymph passes on lymph nodes
- lymph pass into afferent vessels that percolates and exits through efferent vessels
- fluid passes through multiple lymph nodes to get rid of all waste
Increased concentrations of Lymph nodes found in which areas?
1. Cervical regions
2. axillary
3. thoracic
4. abdominal
5. Intestinal
6. Mesenteric
7. popliteal
8. Inguinal
Lymphadenitis (Swollen Glands)
swelling of lymph nodes when challenged by pathogens
Lymphoma
- cancer of the lymph node
- 1° Lymphoma - mutated cells originated at lymph node
- 2° Lymphoma - metastasized cancer cell
Tonsils
- patches of lymphatic tissue at the enterance of the pharynx
- monitors pathogens passing through the mouth
- contains Tonsillar Crypts
Tonsillar Crypts
- pits lined with permanent lymphatic tissue that hold bacteria, food particles, antigens, cellular debris that can be broken down
3 Sets of Tonsils
1. 1 Pharyngeal (Adenoids) Tonsils - largest located below nasal cavity
2. Several Lingual Tonsils - located on either root of tongue, flat
3. Pair of Palatine Tonsils
Palatine Tonsils
- paired is the largest of the tonsils
- below palate near posterior oral cavity
- most exposure to pathogens
- ↑ likelihood of inflammation
Tonsillitis
- inflammation of palatine tonsils
- caused by streptococcus infections
- strep throat
Chronic Tonsillitis
- commonly occurs in children
- tonsils may need to be surgically removed - Tonsilectomy
Spleen
- largest of the lymphatic organs
- located in left hypochondriac region, inferior to diaphragm, dorsolateral to stomach and deep form ribs (10-12) which protects it
- filters lymph
- stabilizes blood volume by transferring plasma to lymphatic system
- consumes dead RBC
- ↑ vascularity which may cause massive hemorrhage when ruptured
- site that transfers mobile cancer cells
Effect on Removal of the Spleen
1. Jaundice - due to lack of RBC consumption
Types of Tissue in the Spleen
1. Red Pulp - ↑ vascularized RBC
2. White Pulp - ↑ WBC and lymphocytes
Lifespan of the Spleen
- in the fetus, hemopoietic tissues produces RBC
- in adults, RBC will produce only if the body needs for RBC (Anemia)
Immune System
collection of responses responsible for immune defense
1st Line of Defense
- external barriers like skin and mucous membrane keep pathogens from entering the body
- non-specific immune defense
Skin
- mechanical barriers that is composed of dead cells that provides a dry nutrient deprived surface for bacteria to penetrate and live.
- normal flora in the skin fight against pathogens
- chemical barrier sweat
Sweat
secretes lactic acid and antimicrobial proteins - defensins, contains a thin coating with ↓pH environment - acid mantle
Mucous Membranes
- moist environments near the outlets of the body that secrete mucus
- mucus coating traps pathogens
- contains cilliated cells that move mucus to be disposed
- contains lysozymes
Chemical of the eyes that protect against invaders
- tears protect the eyes from infection
- secrete lysozymes that rupture bacterial walls, also found in saliva
CT beneath epidermis
- contains areolar CT
- contains macrophages and WBC
- Contains Hyaluronic Acid
Hyaluronic Acid
thick viscous fluid, ↓ pH, traps most microbes
Hyaluronidase
- enzyme that will break down Hyaluronic Acid
- found in some bacteria, protozoans, and snake venom
2nd Line of Defense
- responds by immune surveillance, inflammation, and fever
- non-specific defense
Function of Neutrophils in 2nd Line of Defense
1. roam infected tissues looking for pathogens
2. Phagocytizing bacteria
3. releases killing zone made of H₂O₂ and HClO
4. ultimately kills itself within killing zone
Cause of Rheumatoid Arthritis
some studies show that overproduction of killing zones is the leading cause of RH - autoimmune inflammation of joints causing damage
Function of Eiosinophils in 2nd Line of Defense
attacks allergens, parasites, and break down Ag-Ab complexes
Function of Basophils in 2nd Line of Defense
release histamines (vasoconstrictors) and Heparin (anticoagulant)
Function of Macrophage System in 2nd Line of Defense
- macrophages, dendritic cells, and microglia for the system to goggle cells
Function of Lymphocytes in 2nd Line of Defense
- contains B-cells, T-cells, and NK cells
- immune surveillance and immunity
Complement System
- collection of chemicals that go after pathogens
- globulins > 30 involved in specific and non-specific defenses
- circulate in inactive form until confronted with an infection
- 3 pathways for globulins to activate
3 Complement Pathways
1. Classical
2. Alternative
3. Lectin
Alternative Pathway
globulins directly bind to pathogens
Lectin Pathway
plasma protein, Lectin, binds to microbial cell
Activated Globulins 1 Use of 4 Defenses
1. Immune Clearance
2. Cytolysis
3. Phagocytosis
4. Inflammation
Immune Clearance
RBC will attach to pathogens and deliver to liver or spleen where it will be dropped off to be phagocytized by macrophage
Cytolysis
- complement proteins will puncture microbial cell walls causing excretion of electrolytes and absorption of water
- ultimately causing lysis
Phagocytosis
complement proteins opsonize bacteria by creating attachment points for macrophages to engulf microbial cells.
Inflammation
localized response to trauma or infection
Functions of Inflammation
1. limits spread of pathogens
2. helps to destroy pathogens and tissue debris
3. initiates tissue repair
4. regulation by cytokines - proteins
Classic Symptoms of Inflammation
1. Edema
2. Pain caused by tissue damage or fluid pressure
3. Redness
4. Heat
Localized Hyperemia
- localized heightened response to increase blood flow initiated by histamines and mast cells
- brings in more WBC, antibodies, and selectin
- flushes out toxins
- ↑ capillary filtration
Selectin
complement proteins that bind WBC to endothelium
Jobs of Inflammation
1. brings blood to ↑clotting, walling off bacteria
2. ↑ WBC and cytokines attract macrophages
3. ↑ of Neutrophils and Eiosinophils by 5x
4. 8-12 hours, monocytes enter and turn into macrophages
5. edema ↑ lymphatic drainage
6. dead macrophages and neutrophils mix with cellular debris forming pus
7. heat ↑ metabolism ↑ healing
8. blood brings nutrients and growth factors
Pyrexia
- Fever
- caused by infections, trauma, drugs, brain tumors, etc
- neutrophils and macrophages release pyrogens which initiate ↑ body temp
- shivering ↑ heat
- ↑ temp attracts interferons and ↑ metabolism
- causes liver to withhold iron and zinc - necessary for bacterial growth
Phases of Pyrexia
1. Onset
2. Stadium
3. Defervescence
Onset of Fever
1. Pyrogens ↑ set pt.
2. cutaneous vasoconstriction occurs to draw in heat from the surface
3. cold clammy hands and chills are a result
4. temperature↑
Set Point
average temp for our species
Stadium
- phase where temperature remains elevated
- ↑ metabolism
Defervescence
- defeated pathogens halt pyrogens - set point lowers
- Cutaneous Vasodilation - bringing blood back to surface
Crisis
rapid drop in temp
Lysis
slow drop in temp
Neutrophilia
↑ neutrophil count
Eisinophilia
↑ Eiosinophil count
Effects of Temperature > 45°C
1. denaturation
2. brain damage (44°-46°C)
3. ↑ of 40°C will cause an ↑ in metabolism, thus ↑temp, causing a positive feedback loop
Symptoms of High Temperatures
1. delirious
2. Convulsions
3. coma
Immune Surveillance
- function of macrophages, neutrophils, and NK cells
- mobile cells that seek out pathogens like microbes, host cells, and cancer cells
Function of NK Cells
binds itself to enemy cells producing compounds called perforins
Perforins
are compounds that poke holes inside microbial cells and injects granzymes that will destroy proteins in enemy cells and initiate apoptosis
Interferons
- released be cells who have turned cancerous or infected with a virus
- warning signal for nearby cells to make to antiviral proteins (Ab) and attract macrophages and NK cells