Lymphatic and Immune System

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Anatomy of Lymphatic tissues, vessels, and organs Descriptions of the first and second lines of defense

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

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