733 Lymphatic System

lymphatic sytsem

responsible for carrying out immune responses to protect us from harmful substances in both our internal and external environments

what structures make up the lymphatic system

• lymphatic vessels carrying lymph

• lymph nodes

• thymus

• spleen

• red bone marrow

what is the lymphatic system closely allied with

the cardiovascular system to maintain interstitial fluid volume and assists the digestive system in transporting nutrients

functions of the lymphatic system

• drains excessive fluid from the body tissues and transport it back to venous circulation

• recirculate proteins that escape from vascular capillaries

• absorb fat not taken up in the digestive system and transport it back to the venous circulation

• contains and transports cells and products of the immune system

cells and products of the immune system

white blood cells, antibodies, and other cytokines that regulate immune responses

lymphatic vessels

circulate lymph, a clear and watery fluid similar to blood plasma

lymphatic capillaries

originate from most tissues in the body and merge to form larger lymphatic vessels

lymphatic vessels pathway

eventually merge into two main ducts (right and thoracic lymphatic duct) that drain fluid back into venous system

right lymphatic duct

drains the right upper quarter into the junction of the right internal jugular and right subclavian veins

thoracic duct

drains the remaining areas of the body; travels up through the left posterior thorax, emptying into the internal jugular or left subclavian vein

lymphatic flow

lymphatic capillaries → lymphatic vessels → major lymphatic vessels → lymphatic ducts → venous system

primary lymphatic organs

sites where lymphocytes are formed and become immunocompetent (capable of carrying out an immune response)

secondary lymphatic organs

sites where most immune responses occur

primary lymphatic organs structures

• thymus

• bone marrow

thymus location

located in the mediastinum posterior to the sternum and anterior to the aorta

thymus function

plays a role in the development of the immune system; t-cells migrate here to be developed and stored

bone marrow location

connective tissue found between trabeculae of spongy bone

bone marrow function

site of production of white blood cells, including lymphocytes and B cells

secondary lymphatic organs structures

• lymph nodes

• spleen

• lymphatic nodules (tonsils)

lymph nodes location

found in clusters along lymphatic vessels that contain many lymphocytes and other leukocytes to filter lymph that passes through

phagocytic cells (neutrophils and macrophages)

leukocytes that filter out and destroy microorganisms or foreign material in the lymph

lymphocytes in the lymphatic system

when they encounter foreign material initiate an immune response

spleen location

upper left quadrant in between stomach and diaphragm

spleen function

largest lymphatic organ; primary role is to filter blood, recycle aging red blood cells and circulating microorganisms, supply immunocompetent T and B lymphocytes, and manufacture antibodies. Estimated to filter 10-15% of total blood volume every minute

spleen tissues

consists of two different types of tissues:

1. red pulp tissue

2. white pulp tissue

red pulp tissue

removes old red blood cells from circulation (through phagocytosis)

white pulp tissue

contains and produces antibody-producing lymphocytes and contains monocytes which remove antibody-coated bacteria from circulation

lymphatic nodules

small masses of lymphatic tissue that are not surrounded by a capsule

mucosa-associated lymphatic tissue

found in the mucous membranes lining the GI tract, urinary tract, reproductive tracts, and respiratory airways

tonsils

five different lymphatic nodules usually in the pharyngeal region

fluid exchange in capillary beds

blood plasma→ interstitial space→ lymphatic capillaries (3L per day)

filtration

fluid moves from blood to interstitial space

reabsorption

fluid moves from interstitial space to blood

blood hydrostatic pressure

the pushing force exerted by blood against the capillary walls, driving fluid and small solutes out into the tissues to form interstitial fluid and eventually lymph

blood osmotic pressure

work together to maintain fluid balance between your blood vessels and body tissues by pulling fluid into the capillaries

Starling’s Law (Starling’s Equilibrium)

the net pressure acting on the fluid in the capillaries

where is blood hydrostatic pressure highest

at the arterial end of the capillary than at venous end of the capillary

what are blood colloid pressure levels

constant throughout the capillary

what does net pressure favor

favors filtration at the end of the capillary

arterial end net filtration pressure

fluid exits capillary since capillary hydrostatic pressure is greater than blood osmotic pressure

mid capillary net filtration pressure

no net movement of fluid since capillary hydrostatic pressure = blood osmotic pressure

venous end net filtration pressure

fluid re-enters capillary since capillary hydrostatic pressure is less than blood osmotic pressure

edema

swelling due to fluid that remains in the interstitial space; is either the result of increased filtration or decreased reabsorption in the microcirculation

edema- increased filtration

• increased capillary blood pressure

• increased permeability of blood capillaries

edema- decreased reabsorption

decreased concentration of plasma proteins

• malnutrition

• kidney disease

• liver disease

lymphedema

a disorder in which the lymphatic system is unable to remove water and protein from the tissue of a certain area of the body. This results in abnormal accumulation of water and proteins in the interstitial space, primarily in subcutaneous tissues

causes for lymphedema

• hereditary or congenital affecting lymphatic system

• radiation therapy causing fibrosis of involved tissue

• injury to the system following surgical procedure

• tumors that grow in lymph vessels

complement

attacks and helps eliminate foreign substances

T cells

a type of white blood cell that plays a central role in the body’s adaptive immune system