97 terms

A & P Chapter 20

Lymphatic System
What two body systems does the Lymphatic System support?
The Cardiovascular and Immune System.
How many "parts" make up the Lymphatic System?
Three. 1) a meandering network of Lymphatic Vessels, 2) Lymph, the fluid contained in those vessels, and 3) lymph nodes that cleanse the lymph as it passes through them.
What is "Lymph?"
The Interstitial fluid that is collected by the Lymphatic Vessels. Once fluid enters the lymphatics it's called "Lymph."
What cleans the Lymph?
The Lymph Nodes as the Lymph passes through them.
What makes up the Lymphoid Organs?
Lymph Nodes, Spleen, Thymus, Tonsils, and other lymphoid Tissues scattered throughout the body.
What do Lymphoid Organs house?
Phagocytic cells and lymphocytes, which play essential roles in the body's defense mechanisms and its resistance to disease.
Together, the Lymphatic System and the Lymphoid Organs and Tissues provide the structural basis of what system?
The Immune System
What is the main function of the Lymphatic Vessels?
This system "sucks" in all the fluid(s) left behind in the tissue spaces (Interstitial Fluid) plus any plasma proteins that escapre from the bloodstream and carry it back to the blood to ensure that the cardiovascular system has sufficient blood volume to operate properly.
What is meant by "Lymphatics?"
Lymphatic Vessels
What is "Interstitial Fluid?"
The Hydrostatic and Colloid Osmotic Pressures operating at capillary beds force fluid out of the blood at the arterial ends of the beds ("upstream") and cause most of it to be reabsorbed at the venous ends ("downstream").
In which direction does Lymph flow once in the Lymphatic System?
It flows in a one-way system which is towards the heart.
Where does the transport system for Lymph begins?
In microscopic blind-ended Lymph Capillaries.
Where are Lymphatic Capillaries found?
These capillaries weave between the tissue cells and blood capillaries in the loose connective tissues of the body.
Are Lymphatic Capillaries found everywhere in the body?
No! They are not found in bones, bone marrow, teeth, and the entire Central Nervous System (where the excess tissue fluid drains into the cerebrospinal fluid).
What is one difference between blood capillaries and lymphatic capillaries?
Although similar to blood capillaries, lymphatic capillaries are so remarkably permeable that they were once thought to be open at one end like a straw.
What are the 2 reasons Lymphatic Capillaries so remarkably permeable.
1) The endothelial cells forming the walls of lymphatic capillaries are not tightly joined. Instead, the edges of adjacent cells overlap each other loosely, forming easily opened, flaplike mini-valves. 2) Collagen filaments anchor the endothelial cells to surrounding structures so that any increase in interstitial fluid volume opens the minivalves, rather than causing the lymphatic capillaries to collapse.
What does "Blind-Ended" tubes mean? (in reference to the lymphatic capillaries)?
These are tubes that are sealed on one end.
How are the "mini-valves" open to allow fluid to enter?
When fluid pressure in the interstitial space is greater than the pressure in the lymphatic capillaries.
Why doesn't interstitial fluid leak out of the Lymphatic Capillaries?
Because the pressure is greater inside the lymphatic capillary, the endothelial minivalve flaps are forced closed.
Describe the Lymphatic "Trunks."
They are formed by the union of the largest collecting vessels, and drain fairly large areas of the body.
Name the major "trunks." (Note: they're named mostly for the regions from which they collect Lymph)
Lumbar Trunk, Bronchomediatinal Trunk, Subclavian Trunk, Jugular Trunks, and Intestinal Trunk.
Which of the "trunks" is a single trunk?
The Intestinal Trunk
Can Proteins in the interstitial space enter blood capillaries?
No. But they can enter lymphatic capillaries easily.
How do blood capillaries respond when tissue is inflamed?
Lymphatic capillaries "develop" openings that permit uptake of even larger particles such as cell debris, pathogens (disease-causing microorganisms such as bacteria and viruses), and cancer cells.
Lymphatic Capillaries pick up pathogens, which are disease-causing microorganisms, and travel throughout the body. How is this threat to the body "Partly" resolved?
The Lymph takes "detours" through the lymph nodes, where it is cleansed of debris and "examined" by cells of the immune system.
What are "Lacteals?"
They are highly specialized lymphatic capillaries present in the fingerlike villi of the intestinal mucosa. It take up lipids.
Why is it that the Lymph which drains from the digestive viscera is milky white rather than clear?
Because the Lacteals play a major role in absorbing digested fats from the intestine.
The Lacteals play a major role in absorbing digested fats from the intestine. What color is the "Fatty Lymph" and what is it called?
It's white versus clear. It's called Chyle.
What is Chyle and where does the Lymphatic stream deliver the Chyle to?
Chyle is the white "fatty lymph" absorbed from the intestines by Lacteals. Chyle is also delivered to the blood.
Lymph flows through successively larger and thicker-walled channels. What is it's route?
1st it begins in collecting vessels, then trunks, and finally the largest of all, the ducts.
When Lymph is "vaccumed" up, where is it eventually delivered to?
Lymph is eventually delivered to one of two large ducts in the thoracic region.
Where are the two large ducts where Lymph is delivered to located?
The two large ducts are located in the thoracic region.
Name the parts Listed.
A) Internal Jugualr Vein B) Entrance of right lymphatic duct into vein C) Entrance of thoracic duct into vein D) Thoracic Duct E) Cisterna Chyli F) Aorta G) Lymphatic Collecting Vessels H) Cervical Nodes I) Auxillary Nodes J) Inguinal Nodes
View the picture. Which letters represent Lymph Nodes. Name them.
H) Cervical Nodes I) Axillary Nodes J) Inguinal Nodes
Look at the picture. What does the green section represent? Into what letter is that Lymph deposited?
The green portion represents the area that the Right Lymphatic Duct drains which is from the right upper limb to the right side of the head and right side of the thorax. It's deposited into (B) which is the entrance of right lymphatic duct into vein.
Look at the picture. What does the pink section represent? Into what letter is that Lymph deposited?
The much larger Thoracic Duct (as compared to the right lymphatic duct) receives Lymph from the rest of the body. It is deposited into (C) which is the entrance of Thoracic Duct into vein.
What is the function of the "Cisterna Chyli?"
It collects lymph from the two large lumbar trunks that drain the lower limbs and from the intestinal trunk that drains the digestive organs.
Where is the Cisterna Chyli located?
Anterior to the first two lumbar vertebrae.
About how much Lymph does the Lymphatic System drains and clean each day?
About three liters per day.
Once Lymph is cleaned (filtered) where does it go? How?
To the circulatory system. Through the junctions of the internal jugular veins and subclavian veins on its own side of the body.
Where does filter Lymph enter the Circulatory System? In which side?
It enters through the junctions of the (A) & (D) Internal Jugular Veins and (B) & (F) Subclavian Veins. It enters it on its own side of the body.
Name all the parts listed?
A) Right Jugular Vein, B) Right Subclavian Vein, C) Thoracic Duct D) Esophagus, E) Left Jugular Vein, F) Left Subclavian Vein, G) Trachea H) Cisterna Chyli I) Inferior Vena Cava.
What is "Lymphangitis?"
This is when Lymphatic vessels are severely inflamed, due to the "Vasa Vasorum" (which is a network of small blood vessels that supply the larger vessels with nutrients) becoming congested with blood. As a result, the pathway fo the associated superficial lymphatics becomes visible through the skin as red lines that are tender to the touch.
Does the Lymphatic System have a pump?
No, the Lymphatic System doesn't have a pump. The Lymphatic Vessels are are low-pressure conduits.
How is Lymph "pumped" through the Lymphatic System?
The milking action of active skeleta muscles, pressure changes in the thorax during breathing, and valves to prevent backflow. Pulsation of nearby arteries alsopromote pymph flow. In addition to these mechanisms, smooth muscle in the walls of the lymphatic trunks and thoracic duct contracts rhythmically helping to pump the lymph along.
Why is it a good idea to immobilize a badly infected body part?
To hinder flow of inflammatory material from that region to other areas of the body.
What are 3 functions of the Lymphatic Vessels?
(1) return excess tissue fluid to the bloodstream, (2) return leaked proteins to the blood, and (3) carry absorbed fat from the intestine to the blood (through lacteals).
Where do "Lymphocytes" form from?
Red bone marrow
What do "Lymphocytes" form into?
One of the two main varieties of immunocompetent cells- T Cells (T Lymphocytes) or B Cells (B Lymphocytes) which protect the body against antigens.
What is an "Antigen?"
Antigens are anything the body perceives as foreign, such as bacteria and their toxins, viruses, mismatched RBS's, or cancer cells.
What is the function of the T Cell?
Activated T Cells (which matured in the Thymus) manage the immune respnse, and some of them directly attack and destroy infected cells.
What is the functionof the B Cell?
B Cells protect the body by producing plasma cells, daughter cells that secrete antibodies into the blood (or other body fluids).
Lymphoid (Lymphatic) Tissue is an important component of the immune system. Why?
Mainly because it (1) houses and provides a proliferation site for lymphocytes and (2) furnishes an ideal surveillance vantage point ofr lymphocytes and macrophages.
What is the main "Lymphoid Organ" in the body?
Lymph Node
How many Lymph Nodes are found in the human body?
There are hundreds but becasue they're usually embedded in connective tissue, they are not ordinarily seen.
What are the 3 regions where large clusters of Lymph Nodes occur (near the surface of the body)?
In the Inguinal, Axillary, and Cervical Regions.
What are the two main functions of Lymph Nodes?
Both are concerned with body protection. (1) As Lymph is transported back to the bloodstream, the lymph nodes act as Lymph "Filters." (2) They help activate the Immune System.
What role do Macrophages play in the Lymph Nodes?
Macrophages in the nodes remove and destroy microogranisms and other debris that enter the lymph from the loose connective tissues, effectively preventing them from being delivered to the blood and spreading to other parts of the body.
Why does it say that "Lymph Nodes activates the Immune System?"
Lymph nodes and other lymphoid organs are strategically located sites where lymphocytes encounter antigens and are activated to mount an atttack against them.
Look at the picture. Label all parts indicated.
A) Afferent Lymphatic Vessels, B) Trabeculae, C) Medullary Cord, D) Efferent Lymphatic Vessels, E) Medullary Sinus, F) Subcapsular Sinus.
In the Lymph Nodes, where do Macrophages reside?
They reside in the Lymph Sinuses which is crisscrossing reticular fibers. Macrophages phagocytize foreign matter in the lymph as it flows by in the sinuses. ADDITIONALLY, some of the lymph-borne antigens in te percolating lymph leak into the surrounding lymphoid tissue, where they activate lymphocytes to mount an immune attack against them.
Where does Lymph enter the Lymph Nodes through?
The Afferent Lymphatic Vessels.
Where does Lymph exit the Lymph Nodes through?
At the node's "Hilum" via the Efferent Lymphatic Vessels.
Why does Lymph drain slow (stagnates) through the Lymph Nodes?
Because there are more Afferent Lymphatic Vessels (entrances) than Efferent Lymphatic Vessels (exits).
Why is slow draining from the Lymph Nodes important?
This allows time for the lymphocytes and macrophages to carry out their protective functions.
How many Lymph Nodes does Lymph pass before it's completely cleansed?
Passes through several.
Are Lymph Nodes glands?
No. So when they say swollen gland and refer to the Lymph nodes, this is incorrect.
Lymph nodes may become overwhelmed by the agents they are trying to destroy and become inflamed. What is this called?
Buboes (bu' boz)
What are "Buboes" and what obvious symptom is associated to it?
Buboes is inflamed Lymph Nodes. Buboes are the most obviou symptom of bubonic plague, the "Black Death" that killed much of Europe's populationint he late Middle Ages.
You find Lymph Nodes that are swollen but do not hurt, what might be causing this?
Cancer. This fact that cancer-inflammed Lymph Nodes don't hurt helps distinguish cancerous lymph nodes from those infected by microorganisms which do hurt a person.
Besides the Lymph Nodes, what are the other Lymphoid Organs?
Spleen, Thymus, Tonsils, and Peyer's Patches of the intestine, as well as bits of lymphatic tissue scattered in the connective tissue.
What is one noted difference about the Thymus to the rest of the Lymphoid Organs?
The tissue make up. All, except the Thymus, are composed of reticular connective tissue.
Besides the Lymph Nodes, do the other Lymphoid Organs have Afferent and Efferent Lymphatics?
No. They only have Efferent Lymphatics (exits).
"The Spleen" youtube link.
Where is the "Spleen" located?
The spleen is located to the left of the stomach.
The Spleen provides a site for what?
Lymphocyte proliferation and immune surveillance and response.
Besides the Spleen extracting aged and defective blood cells and platelets from the blood, it's Macrophages remove what?
Debris and foregin matter from blood flowing through its sinuses.
What are 3 additional functions for the Spleen mentioned in the book?
(1) It stores some of the breakdown products of red blood cells for later reuse (for example, it salvages iron for making hemoglobin) and releases others to the blood for processing by the liver. (2) It sotres blood platelets. (3) It is thought to be a site of erythrocyte production in the fetus (a capability that normally ceases after birth).
What is "White Pulp?" Where is it found?
Areas in the Spleen composed mostly of lymphocytes suspended on reticular fibers are called white pulp. White pulp is involved with the immune functions of the spleen.
What is "Red Pulp?" Where is it found?
Red pulp is the red area you see inside the Spleen. It is mainly concerned with disposing of worn-out red blood cells and bloodborne pathogens.
If the Spleen ruptures, must it be removed? Why?
No. Years back they would, but now surgeons have discovered that, if left alone, it will repair itself.
If the Spleen is removed, who picks up the responsiblities of it?
The liver and bone marrow take over most of its functions. In children younger than 12, the spleen will regenerate if a small part of it is left in the body.
What is the main function of the Spleen?
This is where T-lymphocytes precursors mature to become immunocomptentent lymphocytes. In other words, the thymus is where T lymphocytes become able to defend us against specific pathogens in the immune response.
Why doesn't the Thymus have follicles?
Because it lacks B Cells.
What two things does the Thymus differ from other Lymphoid Organs?
1st, it functions strictly in maturation of T lymphocyte precursors and thus is the only lyphoid organ that DOES NOT directly fight antigens. 2nd, the stroma of the thymus consists of epithelial cells rather than reticular fibers. These epithelial cells provide the physical and chemcial environment in which T lymphocytes can become immunocompetent.
What are the names of the 3 types of tonsils that we have? (Top to Bottom)
Phayngeal, Palatine, Lingual tonsils.
Which are the largest of the 3 tonsils?
Palatine Tonsils are the largest and they are also the ones that get infected most often.
What is the main function of tonsils?
Tonsils gather and remove many of the pathogens entering the pharynx in food or in inhaled air.
What is a "Tonsillar Crypts?"
Tonsillar crypts which trap bacteria and particulate matter, and the bacteria work their way through the mucosal epithelium into the lymphoid tissue, where most are destroyed.
Which Lymphoid Organs are located in the digestive tract?
Peyer's patches, the appendix, and teh tonsils.
Where is teh Peyer's Patches located?
They are located in the wall of the distal portion of the small intestine.
Where is the Appendix?
It's a tubular offshoot of the first part of the large intestine.
Why does the book state that the tonsil takes "calculated risks" to "invite" infection? Is there a benefit?
The strategy produces a wide variety of immune cells that have a "memory" for the trapped pathogens. In other words, the body takes a calculated risk early on (during childhood) for the benefits of heightened immunity and better health later.
Why are the "Peyer's Patches" and the "Appendix" are in the ideal position?
Because (1) to destroy bacteria (which are present in large numbers in the intestine) before these pathogens can breach the intestinal wall, and (2) to generate many "memory" lymphocytes for long-term immunity.
What is "MALT?"
Mucosa-associated lymphatic tissue (MALT) protects passages that are open to teh exterior from the never-ending onlaughts of foreign matter entering them. Ex: in the walls of bonchi and in the mucosa of genitourinary (reproductive) organs.
Which two lymphoid organs are developed BEFORE birth?
The Spleen and Tonsils. Shortly after birth, the rest of the Lymphoid organs become heavily populated by lymphocytes.
Which is the first Lymphoid Organ to develop in an embryo?
The Thymus.