Lecture 20: Lymphatic System

Question 1

Lymphatic system

Answer 1

Composed of:
Lymph
Lymphatic vessels
Lymphatic organs (red bone marrow, thymus lymph nodes, tonsils, spleen)

Question 2

Functions of lymphatic system

Answer 2

Drain excess interstitial fluid - picked up by lymphatic vessels and return it to blood
Transports dietary lipids - lymphatic vessels transport lipis and lipid soluble vitamins from GI tract to blood
Filters lymph and blood - foreign substances are filtered by lymph nodes, old/defective blood cells are filtered by spleen
Carry out immunological responses - thymus initiates specific responses to certain pathogens

Question 3

Lymph

Answer 3

Transparent, colorless, watery fluid
Lymphatic capillaries collect remnants of interstitial fluid with cell debris and waste metabolic byproducts to form lymph
Receive lipid droplets from GI tract and lymphocytes from blood

Question 4

Lymphatic vessels

Answer 4

At capillaries of circulatory system, plasma carrying oxygen and nutrients in form in interstitial fluid; after exchange of CO2 and waste materials, only 85% is reabsorbed back into the venous system
Remaining 15% is collected by lymphatic vessels
Carry lymph and pass it to lymph nodes to filter (n all organs except CNS, eye, inner ear and cartilage)
Vessels join to make lymphatic trunk (larger lymphatic channels) which make lymphatic ducts to drain into venous system at the junction of subclavian and internal jugular vein

Question 5

Types of lymphatic tissue

Answer 5

Dense lymphoid tissue - encapsulated (tonsils, thymus, spleen)
Diffuse lymphoid tissue - doesn’t have capsule allowing it to easily migrate (Peyer’s patch/MALT - mucus associated lymphoid tissue)

Question 6

Lymph nodes

Answer 6

Bean shaped in groups
Accompany deep and superficial blood vessels
Site of lymph filtration and B lymphocyte proliferation
Cervical, axillary, lumbar, inguinal

Question 7

Structure of lymph node

Answer 7

Surrounded by fibrous capsule
Afferent lymphatic vessels around that collect lymph
Efferent lymphatic vessels on concave surface - hilum
Sinuses - where lymph is drained; deep within
Lymphoid follicles - aggregation of B cells (some T cells and macrophages); filters and monitors contents of lymph

Question 8

Thymus

Answer 8

Pinkish gland; 10-15g (birth) - 30-40g (puberty)
Replaced by connective tissue after puberty
2 lobes in mainly anterior (some superior) mediastinum
Function: train immature T lymphocytes

Question 9

Spleen

Answer 9

In abdominal cavity in left hypochondriac region; size of fist
Parallel to ribs 9-10; fractures may puncture the spleen
Function: filter old or damaged RBC (lifespan 120 days; ~2 million are removed every second), stores platelets
2 surfaces (medial/visceral, lateral/diaphragmatic)
2 borders (superior, inferior)
2 poles (anterior, posterior)
Medial surface: in touch with abdominal viscera (stomach, L kidney, pancreas); at the center is entrance/exit of blood vessels, nerve fibers, splenic artery, splenic vein, efferent lymphatic vessels = hilum

Question 10

Splenomegaly

Answer 10

Enlargement of spleen

Question 11

Splenectomy

Answer 11

Removing spleen

Liver and bone marrow take over spleen

Question 12

Tonsils

Answer 12

Aggregates of encapsulated lymphoid tissue containing lymphoid follices (5)
Function: produce antibodies against antigens in respiratory or digestive system
Pharyngeal tonsil (1): roof of nasopharynx behind nasal cavity; replaced by connective tissue
Palatine tonsils (2): back or oral cavity
Lingual tonsils (2): back of tongue

Question 13

Pathway of lymph

Answer 13

Lymph passes from lymphatic capillaries -> lymphatic vessels -> lymph nodes -> lymph trunks (lumbar, intestinal, bronchomediatinal, subclavian, jugular) -> thoracic duct or R lymphatic duct -> blood circulation

Question 14

Thoracic duct

Answer 14

Starts at cisterna chyli at LI/LII
Passes diaphragm, ascends in posterior mediastinum, drains into junction of L internal jugular and L subclavian vein along with L bronchomediatinal, L subclavian, L jugular trunk
Receives lymph from lower limbs, pelvic cavity, abdominal cavity, L thoracic cavity, L head/neck, L upper limb

Question 15

R lymphatic duct

Answer 15

Union of R subclavian, R jugular, R bronchomediastinal trunk that empties at junction of R subclavian and R internal jugular vein
Receives lymph from R upper limb, R thoracic cavity, R head/neck

Question 16

Lower limb and pelvis lymphatic drainage

Answer 16

Lymph of lower limbs collected by superficial and deep lymphatic vessels, drains into inguinal lymph node along with lower quadrant of anterior abdominal wall and perineum
Pelvic viscera drains into pelvic lymph node
Inguinal lymph nodes drains into pelvic lymph node which drains into lumbar trunk and to cisterna chyli

Question 17

Abdomen lymphatic drainage

Answer 17

Lymph of alimentary canal, liver, pancreas, spleen drains into pre-aortic lymph node which drains into intestinal trunk and to cisterna chyli
Lymph of posterior abdominal wall, kidneys, gonads, adrenal glands drain into para-aortic lymph nodes to lumbar trunks to cisterna chyli

Question 18

Thorax lymphatic drainage

Answer 18

Lymph of thorax drains into parasternal, diaphragmatic, intercostal, mediastinal lymph nodes
Drain into thoracic duct on L side, and R bronchomediastinal trunk to R lymphatic duct on R side

Question 19

Head and neck lymphatic drainage

Answer 19

Lymph of head and neck drain into superficial and deep lymph nodes
Drain into L thoracic duct on L side or R lymphatic duct on R side via jugular trunk

Question 20

Upper limb lymphatic drainage

Answer 20

Lymph of upper limbs drain into superficial and deep lymph nodes, anterior thoracic wall, upper quadrant of anterior abdominal wall
Drains into axillary lymph nodes which drain into subclavian trunk that drains to either L thoracic duct or R lymphatic duct