lymphatic system

fxns of lymphatic system

produce/maintain/distribute lymphocytes
maintain blood volume, BP, interstitial fluids
provide alt route for distribution of hormones, nutrients, wastes
fat absoprtion

plasma

fluid in blood vessels

interstitial fluid

fluid in tissues

lymph

fluid in lymphatic vessels

flow of lymph

capillaries → vessels → trunks → ducts

lymphatic capillaries

smallest vessels intertwined w/blood capillary beds - large highly permeable lumen - carries lymp to lymphatic vessels

lymphatic vessels

formed by merging lymphatic capillaries together- travel w/blood vessels - have one-way valves to move lymph

lymphatic trunks

9 vessels that drain lymph from capillaries/vessels

cisterna chyli

merging of lumbar trunks + intestinal trunks - @ inferior to diaphragm, connects to thoracic ducts

lymphatic ducts

2 vessels drain lymph from trunks and return to blood at right/left subclavian veins (near internal jugular veins

thoracic duct

starts from cisterna chyli - drains most of body

lymphatic drains

trunks from lower limbs, abdomen, left thoracic, left arm, left head/neck

right lymphatic duct

drains trunks from right thoracic, right arm, right head/neck

lymphocytes

white blood cells originating from lymphoid progenitor cells that protect body from infections

T-cells

make up 80% of lymphocytes - thymus-dependent - originate in red bone marrow, mature and activated in thymus
fxn: cell-mediated immune response (directly attack infected cells/pathogens)

B-cells

make up 10-15% lymphocytes - bone marrow derived
fxn: antibody-mediated immune response against pathogens

NK cells (natural killer cells)

make up 5-10% lymphoctyes - part of innate immune response
fxn: performs immune surveillance - attack virus-infected and cancerous cells by releasing perforins to induce cell death

immune surveillance

patrolling body to detect pathogens/cancerous cells

innate immune response

first line of immune defence - fast, non-specifc defence against pathogens
one type lymphocyte (NK cells) + other WBCs

adaptive immune response

second line of immune defence - slower, more specific defence against pathogens
T-cells & B-cells
memory - lymphocytes recognise repeat infections to fight faster

lymphocytes originate from…

lymphoid progenitor cells

other WBCs (macrophages, neutrophils, etc…) originate from…

myeloid progenitor cells

Major hstocompatibility complex (MHC)

molecules present peptide fragments on surface of cells - detects self vs pathogens

lymphatic tissues

where lymphocytes are stored & activated

lymphatic nodules

small oval areas packed w/lymphocytes - @ all throughout body

mucosa-associated lymphoid tissue (MALT)

in mucosal lining (body entry-points) - @ digestive tract, respiratory tract, urinary tract, reproductive tract

Peyer’s patches

type of MALT - @ small intestine

tonsils

type of MALT - @ pharynx

palatine tonsils

type of MALT - @ back of throat

lymphatic organs

have distinct boundaries, surrounded by fibrous capsule

lymph nodes

small, bean-shaped organ found throughout body along lymphatic vessels - filter lymph fluid, activate immune cells, check for pathogens

afferent vessels

take lymph into lymph node

efferent vessels

take lymph out of lymph node

cervical nodes

nodes in head and neck area

axillary nodes

nodes in arms/breasts

thoracic nodes

nodes in lungs/mediastinum

abdominal nodes

nodes in urinary/reproductive organs

intestinal/mesenteric nodes

nodes in digestive tract

inguinal/popliteal nodes

nodes in the legs

thymus

site of T-cell maturation - @ above heart - gets bigger during puberty then shrinks over time

spleen

has white pulp + red pulp - @ upper left abdomen

white pulp

part of spleen - does immune surveillance, mostly contains B and T cells

red pulp

part of spleen - recycles damaged red blood cells (blood filtration)