Lymphatics Comprehensive Notes

Lymphatic System Recap

  • Recap of fluid exchange.

  • Arterial End: Water and solutes (sugar, salt, proteins) are forced out.

  • Venous End: Water and solutes are forced back in.

  • Fluid outside cells is called extracellular fluid (ECF), interstitial fluid, or ground substance.

  • Once this fluid enters a lymphatic vessel, it's called lymph.

  • Fluid inside the cells is intracellular fluid.

  • Fluid inside blood vessels is blood.

  • Lymph comes from blood via filtration.

  • The difference between lymph and ECF is location.

  • The difference between lymph and blood is composition.

Lymphatic Vessels: Trunks and Ducts

  • When identifying lymphatic vessels, specify "trunk" or "duct".

  • "Drain" refers to lymph, not blood, in this context.

  • Lymph flow is always towards the neck.

Lymphatic Trunks

  • Three main trunks at the bottom (some pictures may show four).

  • Two lumbar trunks.

  • One intestinal trunk.

  • If organ isn't clear, lumbar/intestinal trunks can be mixed up in labeling.

Lumbar Trunks

  • Drain everything below the waist.

  • Includes pelvic cavity and legs.

  • Also drains the abdominal wall (lining of the belly).

Intestinal Trunk

  • Drains digestive organs.

Cisterna Chyli

  • Lymph from lumbar and intestinal trunks flows into the cisterna chyli.

  • Receives lymph from both lumbar trunks and the intestinal trunk.

  • Contains chyle (milky-looking lymph due to fat content from digestive organs).

  • Lymph is normally clear, but high fat content makes lymph in the cisterna chyli milky/cloudy.

  • After leaving the cisterna chyli, it's generally called lymph again.

Thoracic Duct

  • Lymph flows from cisterna chyli into the thoracic duct.

  • The thoracic duct travels along the vertebral column.

  • Makes a U-turn near the shoulder/neck area.

  • Receives lymph from left jugular trunk, left subclavian trunk, left bronchiomediastinal trunk.

Tributaries to Thoracic Duct

  • Left Jugular Trunk: Drains the left half of the head and neck.

  • Left Subclavian Trunk: Drains the left arm and left shoulder.

  • Left Bronchiomediastinal Trunk: Drains the left half of the chest.

Thoracic Duct Endpoint

  • The thoracic duct empties its lymph into the left subclavian vein.

  • Lymph is returned to the blood.

Right Lymphatic Duct

  • Small duct on the right side.

  • Receives lymph from the right jugular trunk, right subclavian trunk, and right bronchiomediastinal trunk.

  • These drain the right half of the head and neck, right upper limb, and right half of the chest, respectively.

Differences Between Ducts

  • The thoracic (left lymphatic) duct is much larger and longer than the right lymphatic duct.

  • The right lymphatic duct is small.

  • The thoracic duct empties into the left subclavian vein.

  • The right lymphatic duct empties into the right subclavian vein.

  • Lymph comes from blood, is cleaned, and returned to blood.

Lymph Nodes Structure

Components

  • Lymph Nodes are bean-like structures.

  • Lymphatic Nodules: Rings within the lymph node (2-3 rings in triangles, like pepperoni pizza slices).

  • Germinal Centers: Dark spots inside the lymphatic nodules.

  • Capsule: Connective tissue surrounding the lymph node (like skin or cellophane).

  • Trabeculae: Extensions of the capsule into the interior, provide structural support (like house walls).

  • The trabeculae create compartments (compartmentalization).

Cortex and Medulla

  • Cortex: Superficial area; everything superficial to the line.

  • Medulla: Deep area; everything deep to the line.

  • Cortex and Medulla will appear in other systems.

  • Medullary Cords: Purple structures in the medulla.

Afferent and Efferent Vessels

  • Hilum: Indentation in the lymph node.

  • Efferent Lymphatic Vessels: Located on the hilum side.

  • Afferent Lymphatic Vessels: Located on the side opposite the hilum.

  • More afferent vessels than efferent vessels.

Lymph Flow

  • More lymph enters the lymph node than leaves it.

  • Lymph spends more time in the lymph node, allowing it to be cleaned.

  • The lymph nodes filter the lymph.

Lymph Flow Pathway

  1. Afferent Lymphatic Vessel.

  2. Subcapsular Sinus.

  3. Cortical Sinus.

  4. Medullary Sinus.

  5. Efferent Lymphatic Vessel.

  • Efferent vessel of one lymph node becomes the afferent vessel of the next.

  • Lymph nodes are strung out like a beaded necklace, cleaning the lymph along the way.

  • Lymph is cleaned then returned to the blood at the subclavian veins.

Sinuses and Macrophages

  • The sinuses are like hallways.

  • Reticular fibers act like spider webs.

  • Macrophages patrol the sinuses.

  • Lymph passes through sinuses, but any pathogens/bacteria get caught in the reticular fibers.

  • Macrophages then engulf and cleanse the lymph.

Lymphatic System Overview Lecture

  • Network of vessels penetrating tissues alongside arteries and veins.

  • Collection of tissues and organs producing immune cells.

  • Cells, tissues, and organs responsible for defending the body.

Functions of Lymphatics

  • Fluid Recovery: Reabsorb excess water and proteins back into blood (specifically, subclavian veins).

  • Immunity: Pick up excess interstitial fluid, foreign cells, and chemicals; cleanse fluid, then return to blood.

  • Lipid Absorption: Lacteals (lymphatic capillaries) in the small intestine absorb lipids.

Lymph Composition

  • Normally clear (like water).

  • After a meal, it's milky and cloudy due to high lipid content.

  • This milky lymph is called chyle and is found in the cisterna chyli.

  • Lymph is like blood plasma but minus the proteins (proteins are too large to fit through intercellular clefts/fenestrations).

  • Contains cellular debris, macrophages, pathogens, and traveling cancer cells.

Lymphatic Capillaries

  • Tiny vessels found almost everywhere except bone, cartilage, CNS (brain and spinal cord), and cornea.

  • Closed at one end (like a cul-de-sac).

  • Overlap each other (like shingles).

  • No tight junctions, no continuous basement membrane.

  • Large gaps allow big things (like lipids) to pass through.

  • Have even thinner walls than veins; collapse easily.

Anchoring Filaments

  • Tether lymphatic capillaries to surrounding tissues to prevent collapse (like tying a tent).

  • Endothelial cells overlap.

  • When pressure outside rises (fluid accumulation), cells pop open and ECF drains in.

  • When pressure drops, they close back up.

Valves and Pressure

  • Hydrostatic pressure in lymph is very low.

  • Valves prevent backflow.

Lymphatic Vessel Hierarchy

  1. Lymphatic Capillaries -->.

  2. Collecting Vessels -->.

  3. Lymphatic Trunks -->.

  4. Ducts (thoracic duct, right lymphatic duct) -->.

  5. Subclavian Veins.

  • Collecting vessels empty into lymph nodes, where pathogens are phagocytized.

  • Lymph nodes are the filters/cleaners, monitoring the fluid.

Lymphatic Trunks: Drainage

  • Lumbar trunks: drain everything below the waist (including abdominal wall).

  • Intestinal trunk: drains digestive organs (small intestine, large intestine, liver, stomach).

  • Bronchomediastinal trunk: drains chest (heart, lungs, thoracic wall).

  • Subclavian trunks: drain arms and shoulders.

  • Jugular trunks: drain the head and neck.

  • Trunks merge to form ducts.

Ducts: Empties

  • Right lymphatic duct: Empties into the right subclavian vein.

  • Thoracic duct (Left lymphatic Duct): Larger and longer, begins at cisterna chyli (formed by lumbar and intestinal trunks), Empties into the left subclavian vein, Drains everything below diaphragm, but gets lymph from same three trunk on the left (head the drain the same on left vs right side of the thoracic cavity). Starts at cisterna chyli, travels along the vertebral column makes U-turn and connects into left subclavian vein.

Lymph Flow Summary

  • Lymph flow similar to veins, but hydrostatic pressure is even lower.

  • Smooth muscle contraction, respiratory pump, skeletal muscle pump, and valves aid flow.

  • Lymph has no physical pump (unlike the heart for blood).

  • Lower pressure = lower/decreased flow/speed.

Lymphatic Cell Types

  • Natural Killer (NK) Cells: Attacks invaded cells or non-self cells.

  • Immune surveillance.

  • T Cells and B Cells: Abbreviated as T cells and B cells (T comes from thymus).

  • B Cells: For us, B = bone marrow, originally from bursa of Fabricius.

  • Plasma cells secrete antibodies.

  • Macrophages: Very active phagocytic cells; antigen-presenting cells (APCs).

  • Dendritic Cells (Langerhans Cells): APCs found in the epidermis.

Lymphatic Tissues and Organs

  • Lymphatic Tissue: Tissue with clusters of lymphocytes.

  • Primary Lymphatic Organs: Where T and B lymphocytes become immunocompetent (trained to do their job), red bone marrow, thymus.

  • Thymus: Located in the superior mediastinum shrink after age 14, Body learning who you are (lymphocytes)

  • Secondary Lymphatic Organs: Where immunocompetent cells migrate to after being trained in primary organs lymph nodes. The cells are being shaped they're have fibrous capsule, the trabeculae (divide interior into compartments provide support). Hilum (the indention of the lymph node), They have the medulla (deep to cortex), afferent lymphatic vessels, efferent lymphatic vessels (on the hilum)

Lymph Nodes

  • Activation of T and B cells occur there, They have the several locations to keep an eye on

  • abdominal area by doctor palpation to look for anything hard, Axillary lymph nodes (under arm by palpation), in the neck, cervical area, and Brest

Tonsils

  • contain crypts for debris / bacteria

  • functions to guard against inhaled and ingested pathogens

  • the pharynx is the throat (not what you think)

  • Lingual tonsils (back of tougne), Palatine tonsils (removable) on sides. pharyngeal tonsils are in back of nose behind ears

Spleen

Largest body lymphatic organ, Red and white pulp, the functions include

  • Hemopoiesis: What function is the spleen looking or monitor for? Answer: Paths, forigen approach make the body sick!

  • Transfers excess blood plasma to lymphatic system

LAB Practical Guidelines

  • There may be a class before. It may take a little to setup

  • don't move any thing, touch or bump. if you do bump please tell so the next person does have to miss the picture to the misplace

  • Micro scopes, No doubling up

  • The practice will run for probably the entire class. There is lecture, so stay after finished