Lymphatic & Immune Lymphatic & Immune SystemSystem

Lymph: Definition Lymph: Definition (1)(1)

Lymph is excess tissue fluid contained in Lymph is excess tissue fluid contained in lymphatic vesselslymphatic vessels

Consists of (mostly) water and plasma Consists of (mostly) water and plasma proteins that have leaked out of the proteins that have leaked out of the capillariescapillaries

Semi-independent parts of the Semi-independent parts of the lymphatic system (1)lymphatic system (1)

1.1. Meandering network of lymphatic vesselsMeandering network of lymphatic vessels

2.2. Lymphoid tissues and organs scattered Lymphoid tissues and organs scattered throughout the bodythroughout the body

Functions of the lymphatic system Functions of the lymphatic system (2)(2)

1.1. Lymphatic vessels return interstitial fluid Lymphatic vessels return interstitial fluid and leaked plasma proteins back to the and leaked plasma proteins back to the bloodblood

2.2. Lymphatic capillaries (lacteals) absorb Lymphatic capillaries (lacteals) absorb fats/fat soluble vitamins at intestinal villi fats/fat soluble vitamins at intestinal villi and transport to the bloodand transport to the blood

3.3. The lymphatic system helps defend the The lymphatic system helps defend the body against diseasebody against disease

Lymphatic vessels: 3 types (3)Lymphatic vessels: 3 types (3)

1.1. Blind-ended capillariesBlind-ended capillaries

2.2. Lymphatic collecting vesselsLymphatic collecting vessels

3.3. Trunks and ductsTrunks and ducts

Blind-ended CapillariesBlind-ended Capillaries

Specially adapted:Specially adapted:

1.1. Highly permeableHighly permeable

2.2. One-way valves (similar to veins) so One-way valves (similar to veins) so lymph only flows towards the heartlymph only flows towards the heart

3.3. Valves resist interstitial pressure to Valves resist interstitial pressure to remain openremain open

4.4. Can absorb cell debris, pathogens, Can absorb cell debris, pathogens, cancer cellscancer cells

Collecting VesselsCollecting Vessels

Similar to veins but have thinner walls and Similar to veins but have thinner walls and more internal valvesmore internal valves

Lots of branching networksLots of branching networks Anastomose = dividing/branchingAnastomose = dividing/branching

Travel with the superficial veins in skinTravel with the superficial veins in skin

Deep vessels travel with arteriesDeep vessels travel with arteries

Vasa vasorum (vessels of the vessels) Vasa vasorum (vessels of the vessels) supply nutrients to cellssupply nutrients to cells

Collecting VesselsCollecting Vessels

Capillaries consist of a single layer of cells Capillaries consist of a single layer of cells and are the only blood vessels that can and are the only blood vessels that can exchange materials with the interstitial exchange materials with the interstitial fluidfluid

Cells will die if they are not within 1 or 2 Cells will die if they are not within 1 or 2 cell widths of a capillarycell widths of a capillary

The lymphatic system removes excess The lymphatic system removes excess fluidfluid

Trunks & DuctsTrunks & Ducts

Capillaries join to form vessels that merge Capillaries join to form vessels that merge in the thoracic cavity before entering one in the thoracic cavity before entering one of two ducts:of two ducts:

Thoracic duct & right lymphatic ductThoracic duct & right lymphatic duct

Trunks are formed by joining of the largest Trunks are formed by joining of the largest collecting ducts and are classified by the collecting ducts and are classified by the regions servedregions served Paired lumbar, subclavian, jugular, intestinalPaired lumbar, subclavian, jugular, intestinal

Trunks & Ducts cont’dTrunks & Ducts cont’d

Lymph is delivered into one of the two Lymph is delivered into one of the two large trunks (ducts)large trunks (ducts)

1.1. Right lymphatic ductRight lymphatic duct1.1. Drains right upper arm, the right side of the Drains right upper arm, the right side of the

head and thoraxhead and thorax

2.2. Thoracic ductThoracic duct1.1. Drains the rest of the bodyDrains the rest of the body

Lymph Transportation (4)Lymph Transportation (4)

Every region of the body has extensive Every region of the body has extensive lymphatic vesselslymphatic vessels

Structural walls are similar to veins (but Structural walls are similar to veins (but are thinner) and contain valvesare thinner) and contain valves

Movement is dependent on muscular Movement is dependent on muscular contraction (skeletal) – when muscles contraction (skeletal) – when muscles contract lymph is squeezed past a valve contract lymph is squeezed past a valve that closes and prevents backwashthat closes and prevents backwash

Chief lymphatic cells & function (5)Chief lymphatic cells & function (5)

T cells and B cells protect the body T cells and B cells protect the body against antigensagainst antigens T for thymus originT for thymus origin B for bone origin (red marrow)B for bone origin (red marrow)

T lymphocytes (T cells) mature in the T lymphocytes (T cells) mature in the thymus (along trachea atop heart) and are thymus (along trachea atop heart) and are “tested” if they react against “self” they die, “tested” if they react against “self” they die, if they have potential to attack foreign cells if they have potential to attack foreign cells they leave the thymusthey leave the thymus

T cells cont’dT cells cont’d

Responsible for cell-mediated immunityResponsible for cell-mediated immunity Depends on actions of several types of T cellsDepends on actions of several types of T cells Antibodies are not produced, instead they Antibodies are not produced, instead they

directly attack foreign cells that carry antigensdirectly attack foreign cells that carry antigens Other T cells release proteins to coordinate Other T cells release proteins to coordinate

other actions of the immune response: T cells, other actions of the immune response: T cells, B cells and macrophagesB cells and macrophages

Protects against parasites, bacteria, fungi, Protects against parasites, bacteria, fungi, cancerous cells – anything “foreign”cancerous cells – anything “foreign”

Chief lymphatic cells & function (5) Chief lymphatic cells & function (5) cont’dcont’d

B lymphocytes (B cells) are responsible for B lymphocytes (B cells) are responsible for antibody-mediated immunityantibody-mediated immunity B cells produce antibodies – proteins that bind B cells produce antibodies – proteins that bind

with and neutralize specific antigenswith and neutralize specific antigens

Growing within the bone marrow B cells Growing within the bone marrow B cells develop unique surface receptors that develop unique surface receptors that allow them to recognize specific antigensallow them to recognize specific antigens Protects against viruses, bacteria and foreign Protects against viruses, bacteria and foreign

molecules soluble in blood and lymphmolecules soluble in blood and lymph

Lymph nodes (11)Lymph nodes (11)

Round bean-shaped structures found at Round bean-shaped structures found at certain points along lymphatic vesselscertain points along lymphatic vesselsA fibrous capsule divided into nodules A fibrous capsule divided into nodules containing sinuses (open spaces) filled containing sinuses (open spaces) filled with macrophages and lymphocytes.with macrophages and lymphocytes.Two distinct regions: cortex & medullaTwo distinct regions: cortex & medullaAs lymph passes through the sinuses in As lymph passes through the sinuses in the nodules it is cleansed of infectious the nodules it is cleansed of infectious organisms and debrisorganisms and debris

Lymph nodeLymph node

Lymph nodes (11) cont’dLymph nodes (11) cont’d

Nodules are mainly in the lymph nodes but Nodules are mainly in the lymph nodes but can also be single or in groups can also be single or in groups (aggregations)(aggregations)

Aggregations are found near the body Aggregations are found near the body surface in inguinal (groin), axillary surface in inguinal (groin), axillary (armpits) and cervical (neck) regions(armpits) and cervical (neck) regions

Function of Lymph Nodes (12)Function of Lymph Nodes (12)

2 basic functions2 basic functions

1.1. Filtration – macrophages destroy Filtration – macrophages destroy microorganisms and debrismicroorganisms and debris

2.2. Immune system activation – monitor for Immune system activation – monitor for antigens and mount attack against them!antigens and mount attack against them!

Tuberculosis and leukemia can Tuberculosis and leukemia can cause the spleen to enlargecause the spleen to enlarge

Spleen and its functions (14)Spleen and its functions (14)

Upper left abdominal cavity just beneath Upper left abdominal cavity just beneath the diaphragm (fist-sized)the diaphragm (fist-sized)

Similar structure to a lymph node: outer Similar structure to a lymph node: outer connective tissue divides it into sinus-connective tissue divides it into sinus-containing lobules BUT in the spleen containing lobules BUT in the spleen sinuses are filled with blood NOT lymphsinuses are filled with blood NOT lymph Blood reservoir if needed in times of low Blood reservoir if needed in times of low

pressure or extra oxygen is requiredpressure or extra oxygen is required

Spleen and its functions (14) cont’dSpleen and its functions (14) cont’d

Spleen lobules contain red pulp and white Spleen lobules contain red pulp and white pulppulpRed pulp – rbc, lymphocytes and Red pulp – rbc, lymphocytes and macrophagesmacrophagesWhite pulp – contains only lymphocytes White pulp – contains only lymphocytes and macrophagesand macrophagesFxns: purify blood that passes through Fxns: purify blood that passes through spleen = quality control (removal of spleen = quality control (removal of damaged rbc and invaders)damaged rbc and invaders)

Spleen’s 2 main functions (14)Spleen’s 2 main functions (14)

Quality control of circulating rbc by Quality control of circulating rbc by removing old damaged ones – cleansed removing old damaged ones – cleansed blood stored in red pulpblood stored in red pulp

Helps fight infection – white pulp – Helps fight infection – white pulp – primarily lymphocytesprimarily lymphocytes

Other spleen functions (14)Other spleen functions (14)

Stores breakdown products of RBCs for Stores breakdown products of RBCs for later reuselater reuse

Spleen macrophages salvage and store iron Spleen macrophages salvage and store iron for later use by bone marrowfor later use by bone marrow

Stores blood plateletsStores blood platelets

Important!Important!

Spleen cleanses the bloodSpleen cleanses the blood

Lymph nodes cleanse the lymphLymph nodes cleanse the lymph

Together they keep circulating body fluids Together they keep circulating body fluids relatively free of damaged cells and relatively free of damaged cells and microorganismsmicroorganisms

Thymus and its function (15)Thymus and its function (15)

Located in lower neck behind sternum, Located in lower neck behind sternum, just above the heartjust above the heart

Bilobed organ that secretes 2 hormones:Bilobed organ that secretes 2 hormones:

1.1. Thymosin Thymosin

2.2. ThymopoietinThymopoietin

These cause certain lymphocytes to mature These cause certain lymphocytes to mature and become active in body defenseand become active in body defense

Thymus cont’d (15)Thymus cont’d (15)

Size and activity level vary with age:Size and activity level vary with age:

1.1. Largest and most active during childhoodLargest and most active during childhood

2.2. Stops growing during adolescence and Stops growing during adolescence and slowly starts to shrinkslowly starts to shrink

3.3. May disappear entirely in old age – May disappear entirely in old age – replaced by fibrous fatty tissuereplaced by fibrous fatty tissue

Tonsils and their function (16)Tonsils and their function (16)

Masses of lymphatic tissue near the Masses of lymphatic tissue near the entrance to the throatentrance to the throatGather and filter microorganisms that Gather and filter microorganisms that enter the throat through air and foodenter the throat through air and foodFamiliar tonsils @ back of throat largest & Familiar tonsils @ back of throat largest & most often infected = tonsilitismost often infected = tonsilitisAdenoids (pharyngeal tonsils) lie at the Adenoids (pharyngeal tonsils) lie at the back of the nasal passages – usually back of the nasal passages – usually shrink by 5 years old & gone by pubertyshrink by 5 years old & gone by puberty

Enlarged tonsilsEnlarged tonsils

Adenoids cont’dAdenoids cont’d

Can enlarge and obstruct air passages – Can enlarge and obstruct air passages – causing mouth breathing and nasal voice causing mouth breathing and nasal voice & snoring& snoring

Sometimes removedSometimes removed