Why can't some macromolecules be taken up by blood capillaries?
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Because they are too big.
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Why can't some macromolecules be taken up by blood capillaries?
Because they are too big.
What is a lacteal?
A specialized set of lymphatics large enough to absorb large molecules or chylomicrons.
Describe the movement of chylomicrons after absorption in the intestine.
Intestines → lymphatic vessels → lymph nodes → ductal system.
What is the function of the blinded terminal ends of lymphatic capillaries?
They are inserted within the blood capillaries themselves to take up any excess fluid thrown into the extracellular space.
What are the characteristics of lymphatic vessels?
Larger, thicker-walled vessels with valves that ensure unidirectional flow, affected by pressure gradients.
What happens to lymphatic vessel valves under high pressure?
They open.
What happens to lymphatic vessel valves under low pressure?
They close.
What is the shape and function of a lymph node?
Bean/Kidney-shaped; it filters lymph.
How does lymph flow through a lymph node?
Lymph flows in through multiple afferent vessels and exits through one efferent vessel.
Where can lymph flow after passing through a lymphatic vessel?
Into another lymph node or directly into a lymphatic trunk.
What are lymphatic trunks?
Larger and thicker lymphatic vessels that include three pairs of trunks in the thoracic cavity.
What are the two main components of the circulatory system?
The Cardiovascular System and The Lymphatic System.
What is the function of systemic capillaries in the cardiovascular system?
They are the terminal end of the cardiovascular system where a lot of fluid exchange occurs.
How much excess fluid is thrown into the extracellular spaces daily?
At least 3 liters.
What is lymph?
Lymph is the fluid that flows inside the lymphatic system, including lymphatic vessels and lymph nodes.
What materials, besides excess fluid, are leaked into the extracellular spaces?
Plasma proteins and material originating from tissue cells, such as cytoplasm from disintegrating cells.
What are the important parts of the lymphatic system?
Lymphatic capillaries, lymphatic vessels, lymphatic trunks, lymph nodes, lymphocytes, lymphatic organs, and collecting ducts.
What is edema?
Edema is an excess of interstitial fluid, manifesting as swelling.
What is the role of lymphatic capillaries in preventing edema?
They prevent the accumulation of excess fluid in the extracellular spaces.
What is the smallest structure in the arterial system?
Arterioles.
What are the three main functions of the lymphatic system?
Return excess fluid to the heart, absorption and transport of fat, and immune surveillance.
What areas are drained by the cervical lymph nodes?
Head and Neck
What type of blood do arterioles carry to the capillaries?
Oxygen-rich blood.
What special lymphatic capillaries are involved in the absorption and transport of fat?
Lacteals.
Which lymph nodes drain the upper extremities and breast?
Axillary lymph nodes
What is the structure of capillaries?
Capillaries contain a single layer of endothelial cells and are very porous due to the presence of fenestrations.
What is chyle?
Chyle is a milky fluid conveyed by visceral lymphatics, containing lipids and lipid-soluble vitamins absorbed by the intestine.
What areas do the tracheobronchial lymph nodes drain?
Lungs and mediastinum
What can escape from capillaries into the interstitial space?
Fluids and some proteins.
Describe the general sequence of microcirculation.
Arteries → Arteriole → Capillaries → Venules → Veins.
Which lymph nodes are responsible for draining the lower group of nodes including iliac and inguinal?
Aortic lymph nodes
What occurs in the capillaries?
Fluid, gas, and nutrient exchange, including the continual exchange of O2 and CO2.
What areas are drained by the popliteal lymph nodes?
Legs
What is the smallest structure in the venous system?
Venules.
Which lymph nodes drain the lower limbs?
Inguinal lymph nodes
What do venules do?
Venules receive fluid from the capillaries and deliver blood to the veins.
What areas do the thoracic lymph nodes drain?
Thoracic viscera
What are the four pressures acting on the capillaries?
Two hydrostatic pressures (capillary and tissue/interstitial) and two oncotic pressures (capillary and tissue/interstitial).
Which lymph nodes are responsible for draining the pelvic region?
Abdominal lymph nodes
What is hydrostatic pressure?
The force of a fluid in a contained environment, also known as 'push' pressure.
What areas are drained by the intestinal and mesenteric lymph nodes?
Abdominal viscera
What is oncotic pressure?
Pressure brought about by proteins inside the plasma or blood vessels, also known as 'pull' pressure.
What are diffuse lymphatic tissues?
Sparsely distributed tissues around the area with loosely arranged lymphoid cells and proteins.
What happens at the arterial end of the capillary?
Net fluid has the tendency to move out of the capillary, extruding about 20 liters of fluid over 24 hours.
What is MALT and where is it found?
Mucosa-associated lymphatic tissue, found in the mucosa of the trachea, intestine, GI tract, and respiratory tract.
What happens at the venous end of the capillary?
Fluid tends to move back into the capillary, reabsorbing 17 of the 20 liters extruded from the arteriolar end.
What are lymphatic nodules?
Discrete concentrations of lymphocytes without an outer covering or capsule.
What can result from an excess of 3 liters of fluid in the interstitial space?
Edema.
Where can lymphatic nodules be found?
In the tonsils (lingual, palatine, and pharyngeal), intestinal ileum (Peyer's patches), and appendix.
Where are lymphatic capillaries located?
Inserted in between the blood capillaries.
What distinguishes lymphatic organs from lymphatic nodules?
Lymphatic organs are larger and have a capsule.
What makes lymphatic capillaries very permeable to fluid?
The loosely packed cell arrangement of their single layer of endothelial cells.
What are the main lymphatic organs?
Lymph nodes, thymus, and spleen.
What are the functions of anchoring/collagen filaments in lymphatic capillaries?
They allow free movement by attaching one end to the endothelial wall while the other end is unattached.
Where is the thymus located and what is its function?
Located in the thoracic cavity (anterior mediastinum), it produces T-cells.
What are minivalves in lymphatic capillaries?
Unattached portions or ends of endothelial cells that allow fluid movement towards the lumen of the lymphatic capillary.
What is the origin of the lymphatic system?
Excess fluid not reabsorbed by the blood capillaries (~3L).
What happens to the thymus in adulthood?
It 'disappears' and is replaced by fat.
Describe the one-way flow of lymph in lymphatic capillaries.
Fluid enters via minivalves, moves towards the lumen at high pressure, and shuts the opening at low pressure.
Describe the organization of the lymphatic system.
The lymphatic system includes lymphatic capillaries, vessels, nodes, trunks, and collecting ducts.
Where is the spleen located?
Inside the abdominal cavity, related to the GI tract (left, lateral to the stomach and splenic flexure of the colon, anterior to the kidney).
What is interstitial fluid called once it enters the lymphatic vessel?
Lymph.
What are the characteristics of lymphatic capillaries?
Blinded terminal ends inserted within the blood capillaries themselves.
Describe the production of lymph.
Lymph is fluid flowing through the lymphatic system, originating as interstitial (tissue) fluid that enters the lymphatic vessels.
What is the specialized set of lymphatics in the intestinal epithelium called?
Lacteals.
What are the features of lymphatic vessels?
Larger, thicker walled vessels with valves.
What is the function of lymphatic nodes?
Bean or kidney-shaped organs that filter lymph.
How does lymph enter and exit lymphatic nodes?
Lymph enters via multiple afferent vessels and exits via a single efferent vessel.
What are lymphatic trunks and what do they include?
Larger and thicker vessels that include lumbar trunks (2), intestinal trunk, bronchomediastinal trunk, subclavian trunk, and jugular trunk.
What are the two collecting ducts in the lymphatic system?
Right Lymphatic Duct and Thoracic Duct.
What areas does the Right Lymphatic Duct collect from?
Right side of face, neck, thoracic cavity, and right upper extremities.
What areas are drained by the jugular trunk?
Head and Neck
What areas does the Thoracic Duct collect from?
All other areas not drained into the right lymphatic duct.
What areas are drained by the subclavian trunk?
Upper extremities, breast
Describe the connection of the subclavian vein on the left side.
Left internal jugular vein + Left subclavian vein → Left Brachiocephalic vein.
What areas are drained by the bronchomediastinal trunk?
Lungs, mediastinum
Describe the connection of the subclavian vein on the right side.
Right internal jugular vein + Right subclavian vein → Right Brachiocephalic vein.
What areas are drained by the intestinal trunk?
Intestines (via lymphatic lacteals)
What is the final connection of the left and right Brachiocephalic veins?
Left + Right Brachiocephalic vein → Superior Vena Cava (SVC).
What areas are drained by the thoracolumbar trunk?
Abdominal organs
What areas are drained by the lumbar trunk?
Lower limbs & pelvic organs
What are the three parts of a lymph node?
Cortex (B lymphocytes), Paracortex (T lymphocytes), Medulla (phagocytes).
Into how many collecting ducts do the lymphatic trunks drain?
2 collecting ducts
What is diffuse lymphatic tissue and where is it distributed?
Accumulation of lymphatic tissue in MALT, distributed sparsely in the intestines and respiratory tracts.
Which trunks drain into the right lymphatic duct?
Right subclavian trunk, right jugular trunk, right bronchomediastinal trunk
What are lymphatic nodules and what do they include?
Discrete and packed concentration of lymphocytes, not encapsulated, includes tonsils, Peyer’s patches, and appendix.
Which trunks drain into the left lymphatic duct?
Left subclavian trunk, left jugular trunk, left bronchomediastinal trunk, cisterna chyli (intestinal trunk, lumbar trunk)
What are lymphatic organs and what do they include?
Encapsulated and larger than lymphatic nodules, includes lymph nodes, thymus, and spleen.
Where does the right lymphatic duct drain?
Between the right internal jugular vein and right subclavian vein
Where does the left lymphatic duct drain?
Between the left internal jugular vein and left subclavian vein
What is the cisterna chyli?
An enlarged, starting portion of the intestinal trunk that pierces the diaphragm and enters the thoracic cavity
What forms the left brachiocephalic vein?
Left internal jugular vein and left subclavian vein
What forms the right brachiocephalic vein?
Right internal jugular vein and right subclavian vein
What forms the superior vena cava?
Left and right brachiocephalic veins
What do lymph nodes contain to fend off foreign substances?
Antibodies
What type of cells are found in the cortex of a lymph node?
B-lymphocytes
What type of cells are found in the paracortex of a lymph node?
T-lymphocytes
What type of cells are found in the medulla of a lymph node?
Phagocytes
What is the function of phagocytes in the lymph node medulla?
To engulf foreign material
