Lymphatic System

Question 1

What is the lymphatic system?

Answer 1

a system of lymphatic vessels and lymphatic organs that works continuously to drain and filter ECF from the extracellular fluid spaces throughout the body. It works as a system for draining excess tissue fluid, controlling ECF fluid pressure, and for assisting in the control of infection in the body.

Question 2

Lymphatic vessels

Answer 2

these vessels collect tissue fluid from extracellular fluid spaces all over the body and deliver it to a large lymphatic vessel called the thoracic duct that is located in the chest cavity. The fluid then goes directly to the Cr vena cava where it is returned to the general blood circulation
–the ECF drained from the tissue spaces is called lymph fluid once it has entered the lymphatic circulation

Question 3

What is the origin of extracellular fluid?

Answer 3

Extracellular fluid (ECF) denotes all body fluid outside the cells. Total body water in humans makes up between 45 to 75% of total body weight. About two thirds of this is intracellular fluid within cells, and one third is the extracellular fluid.[1] The main component of the extracellular fluid is the interstitial fluid that bathes cells.

Question 4

Size of lymphatic vessels?

Answer 4

The smallest size lymphatic vessels are about the size of capillaries
–these are located near capillary beds and are open ended so that ECF fluid can drain into them
–lymph fluid that is collected by these very small size lymphatic vessels runs into larger and larger
size lymphatic vessels which ultimately empty into the thoracic duct in the chest

Question 5

Thoracic duct

Answer 5

It is also called the left lymphatic duct or the alimentary duct. A large portion of the body’s lymph is collected by this duct and then drained into the bloodstream near the brachiocephalic vein between the internal jugular and the left subclavian veins.

The thoracic duct is actually much smaller in size than the large and medium size arteries and veins
The thoracic duct runs parallel and very close to the aorta in the chest
The thoracic duct ends where it attaches to the Cr vena cava

Question 6

What is the purpose of the valves inside of the lymphatic vessels?

Answer 6

the valves encourage lymph to move in a single direction and operate like the valves of veins.

Question 7

Lymph nodes

Answer 7

these encapsulated nodular shaped structures are located along the course of most of the lymphatic vessels throughout the body
inside of lymph nodes there are large numbers of lymphocytes and plasma cells that play important roles in immunity.
Lymph nodes are classified as either superficial or deep in location.

Question 8

What is the difference between superficial and deep lymph nodes

Answer 8

The only difference is location.

Question 9

Do lymph nodes change in size?

Answer 9

Lymph nodes increase in size in the presence of infection. If the first lymph node in a chain of lymph nodes is unable to stop the infection, then the infection spreads to the next lymph node in the chain. Cancer cells can be spread this way also.

Question 10

Other lymphoid tissues

Answer 10

–some lymphoid tissues are found scattered diffusely in some organs; eg., intestinal mucosa

– some lymph nodes are encapsulated to form lymphatic structures such as lymph nodes, tonsils, the thymus, and the spleen.

Question 11

Spleen

Answer 11

a large encapsulated lymphoid organ that is attached to the greater curvature of the stomach by the gastrosplenic ligament.

Question 12

basic functions of the spleen:

Answer 12

a. The spleen serves as reservoir for blood storage

Example: The spleen of the dog and the horse have a large capacity to “store” some blood which can 	be used to increase the total blood volume of the general circulation. That is, when needed such as 
during exercise, the spleen contracts to push this “extra” blood into the general circulation.
This has the effect of increasing the oxygen carrying capacity of the general circulation when the 
demand for O2 is highest.

b.  The spleen phagocytizes and removes old and damaged RBC’s from the bloodstream; ie., the 	
spleen serves as filter for removal of old dying RBCs

Question 13

Where is the thymus located and what is its function

Answer 13

The thymus gland is located in the neck above the heart. The function of the thymus gland is to generate mature T lymphocytes (white blood cels that help the immune system fight off illness).

Question 14

Hepatic portal circulation

Answer 14

this is a special arrangement of veins that carry venous return blood, drained from the pancreas, spleen, and the G.I. tract, to a large vein called the portal vein. All of this blood runs through the portal vein to the liver and then through the liver before emptying into the caudal vena cava

Question 15

The pathway of the hepatic portal circulation is as follows:

Answer 15

Veins of the pancreas, the spleen, the small intestine, the large intestine, and the stomach  portal vein 
 liver sinusoids  central veins  hepatic veins  Cd vena cava  right atrium of the heart.

As this venous return blood flows through the liver it comes into direct contact with hepatocytes.

Question 16

–Liver cells (hepatocytes) make changes in the compostion of blood as it passes through the liver; these include:

Answer 16

1.Modification and/or storage of nutrients

Ex: glycogen storage in the liver

2. Biotransformation and detoxification 

Ex: Conversion of ammonia to urea 

Ex: Some medications are biotransformed in the liver and then excreted in the biotransformed state 
through the kidneys. Without biotransformation of the drug, it can’t be eliminated from the 
bloodstream by the kidneys and instead would buildup to toxic levels in the bloodstream.

Not all drugs need to undergo biotransformation before renal clearance can occur. Some will be 
filtered out of the bloodstream by the kidneys in the unchanged state.

Question 17

What is glycogen and why does it need to be stored in the liver

Answer 17

Glycogen is a multibranched polysaccharide of glucose that serves as a form of energy storage in humans,[2] animals,[3] fungi, and bacteria. The polysaccharide structure represents the main storage form of glucose in the body.
Glycogen is mainly stored in the liver and the muscles and provides the body with a readily available source of energy if blood glucose levels decrease.

Question 18

why neonates are so prone to hypoglycemia?

Answer 18

.

Question 19

Why is ammonia in the blood stream and why does it need to be converted into urea

Answer 19

Most ammonia in the body forms when protein is broken down by bacteria in the intestines . The liver normally converts ammonia into urea, which is then eliminated in urine.