BUNDLE 6: LYMPHATIC SYSTEM & NERVOUS SYSTEM
__________________________________________________
PART A: LYMPHATIC SYSTEM
__________________________________________________
INTRODUCTION
Body tissues bathed in interstitial fluid, which leaks constantly from bloodstream through
permeable walls of blood capillaries.
• Some tissue fluid returns to capillaries at venous end
• Others diffuse through more permeable lymph capillaries forming lymph
COMPONENTS
• Lymph
• Lymph vessels
• Lymph nodes
• Lymph organs (spleen, thymus)
• Diffuse lymphoid tissues (tonsils)
• Bone marrow
__________________________________________________
FUNCTIONS OF LYMPHATIC SYSTEM
1. Tissue drainage
• Most fluid leaving plasma returns directly to bloodstream
• Excess (~3-4 L) drained by lymphatic vessels
• Without this: tissues waterlogged; cardiovascular system fails
2. Absorption in small intestine
• Fats and fat-soluble materials absorbed in central lacteals (lymphatic vessels) of villi
3. Immunity
• Lymphatic organs aid production and maturation of lymphocytes
__________________________________________________
LYMPH AND LYMPH VESSELS
LYMPH
• Clear watery fluid similar to plasma (except plasma proteins)
,• Identical in composition to interstitial fluid
Functions:
• Carries large particles (bacteria, cell debris) from damaged tissue to lymph nodes for
destruction/filtering
• Contains lymphocytes involved in immunity
• Transports plasma proteins that seep out back to bloodstream
LYMPH CAPILLARIES
• Blind-end tubes in interstitial space
• Same structure as blood capillaries but more permeable
• Present in almost all tissues EXCEPT: CNS, cornea, bones, most superficial skin
layers
LARGER LYMPH VESSELS
• Often run alongside arteries and veins
• Walls similar thickness to veins; same tissue layers
• Cup-shaped valves ensure one-way flow toward thorax
• No pump; muscles contract rhythmically
LYMPH DUCTS
Two large ducts empty lymph into subclavian veins:
Thoracic duct (~40 cm):
• Starts at cisterna chyli (dilated lymph vessel in front of 1st-2nd lumbar vertebrae)
• Opens into left subclavian vein in root of neck
Right lymphatic duct (~1 cm):
• In root of neck
• Opens into right subclavian vein
• Drains right half of thorax, head, neck, right arm
__________________________________________________
LYMPHATIC ORGANS AND TISSUE
LYMPH NODES
• Oval or bean-shaped; often in groups along lymph vessels
• Lymph drains through them
• Outer capsule of fibrous tissue dips down forming trabeculae
• 4-5 afferent vessels enter; 1 efferent vessel leaves
• Hilum: Concave surface where arteries, veins, and efferent vessels leave
Drainage routes:
, • Head/neck -> deep and superficial cervical nodes
• Upper limb -> elbow nodes -> superficial and deep axillary nodes
• Thoracic organs -> nodes near mediastinum
• Pelvic/abdominal -> many nodes before cisterna chyli
• Lower limbs -> deep and superficial nodes behind knee and groin
Functions:
• Filtering and phagocytosis: Filter lymph; phagocytose microbes
• Proliferation of lymphocytes: Activated T and B lymphocytes multiply
__________________________________________________
SPLEEN
• Contains reticular and lymphatic tissue
• Largest lymph organ
• Lies in left hypochondriac abdominal cavity between fundus of stomach and
diaphragm
• Purplish; ~12 cm long, 7 cm wide, 2.5 cm thick, ~200 g
Organs associated:
• Superiorly/Posteriorly: Diaphragm
• Inferiorly: Left colic flexure of large intestine
• Anteriorly: Fundus of stomach
• Medially: Pancreas and left kidney
• Laterally: Separated from 9th-11th ribs by diaphragm
Structure:
• Slightly oval with hilum on lower medial border
• Enclosed by fibroelastic capsule (trabeculae)
• Splenic pulp (lymphocytes and macrophages) lies between trabeculae
• Blood flows in sinusoids with pores between endothelial cells
Structures entering/leaving:
• Splenic artery (branch of coeliac artery)
• Splenic vein (branch of portal vein)
• Lymph vessels (efferent only)
• Nerves
Functions:
• Phagocytosis: Destroys old/abnormal erythrocytes, leukocytes, platelets, urea
• Storage of blood: Up to 350 mL; available during sympathetic stimulation
__________________________________________________
PART A: LYMPHATIC SYSTEM
__________________________________________________
INTRODUCTION
Body tissues bathed in interstitial fluid, which leaks constantly from bloodstream through
permeable walls of blood capillaries.
• Some tissue fluid returns to capillaries at venous end
• Others diffuse through more permeable lymph capillaries forming lymph
COMPONENTS
• Lymph
• Lymph vessels
• Lymph nodes
• Lymph organs (spleen, thymus)
• Diffuse lymphoid tissues (tonsils)
• Bone marrow
__________________________________________________
FUNCTIONS OF LYMPHATIC SYSTEM
1. Tissue drainage
• Most fluid leaving plasma returns directly to bloodstream
• Excess (~3-4 L) drained by lymphatic vessels
• Without this: tissues waterlogged; cardiovascular system fails
2. Absorption in small intestine
• Fats and fat-soluble materials absorbed in central lacteals (lymphatic vessels) of villi
3. Immunity
• Lymphatic organs aid production and maturation of lymphocytes
__________________________________________________
LYMPH AND LYMPH VESSELS
LYMPH
• Clear watery fluid similar to plasma (except plasma proteins)
,• Identical in composition to interstitial fluid
Functions:
• Carries large particles (bacteria, cell debris) from damaged tissue to lymph nodes for
destruction/filtering
• Contains lymphocytes involved in immunity
• Transports plasma proteins that seep out back to bloodstream
LYMPH CAPILLARIES
• Blind-end tubes in interstitial space
• Same structure as blood capillaries but more permeable
• Present in almost all tissues EXCEPT: CNS, cornea, bones, most superficial skin
layers
LARGER LYMPH VESSELS
• Often run alongside arteries and veins
• Walls similar thickness to veins; same tissue layers
• Cup-shaped valves ensure one-way flow toward thorax
• No pump; muscles contract rhythmically
LYMPH DUCTS
Two large ducts empty lymph into subclavian veins:
Thoracic duct (~40 cm):
• Starts at cisterna chyli (dilated lymph vessel in front of 1st-2nd lumbar vertebrae)
• Opens into left subclavian vein in root of neck
Right lymphatic duct (~1 cm):
• In root of neck
• Opens into right subclavian vein
• Drains right half of thorax, head, neck, right arm
__________________________________________________
LYMPHATIC ORGANS AND TISSUE
LYMPH NODES
• Oval or bean-shaped; often in groups along lymph vessels
• Lymph drains through them
• Outer capsule of fibrous tissue dips down forming trabeculae
• 4-5 afferent vessels enter; 1 efferent vessel leaves
• Hilum: Concave surface where arteries, veins, and efferent vessels leave
Drainage routes:
, • Head/neck -> deep and superficial cervical nodes
• Upper limb -> elbow nodes -> superficial and deep axillary nodes
• Thoracic organs -> nodes near mediastinum
• Pelvic/abdominal -> many nodes before cisterna chyli
• Lower limbs -> deep and superficial nodes behind knee and groin
Functions:
• Filtering and phagocytosis: Filter lymph; phagocytose microbes
• Proliferation of lymphocytes: Activated T and B lymphocytes multiply
__________________________________________________
SPLEEN
• Contains reticular and lymphatic tissue
• Largest lymph organ
• Lies in left hypochondriac abdominal cavity between fundus of stomach and
diaphragm
• Purplish; ~12 cm long, 7 cm wide, 2.5 cm thick, ~200 g
Organs associated:
• Superiorly/Posteriorly: Diaphragm
• Inferiorly: Left colic flexure of large intestine
• Anteriorly: Fundus of stomach
• Medially: Pancreas and left kidney
• Laterally: Separated from 9th-11th ribs by diaphragm
Structure:
• Slightly oval with hilum on lower medial border
• Enclosed by fibroelastic capsule (trabeculae)
• Splenic pulp (lymphocytes and macrophages) lies between trabeculae
• Blood flows in sinusoids with pores between endothelial cells
Structures entering/leaving:
• Splenic artery (branch of coeliac artery)
• Splenic vein (branch of portal vein)
• Lymph vessels (efferent only)
• Nerves
Functions:
• Phagocytosis: Destroys old/abnormal erythrocytes, leukocytes, platelets, urea
• Storage of blood: Up to 350 mL; available during sympathetic stimulation
