Lymphatic System

Question 1

What are the functions of the lymphatic system?

Answer 1

1. Returning excess fluid from the tissues to the blood system
2. Passing excess proteins into the bloodstream
3. Assists in the absorption of foods especially fats from the small intestine
4. Lymph nodes filter harmful substances from the lymph
5. Lymph nodes produce fresh lymphocytes for circulation

Question 2

What is oedema?

Answer 2

Build up of excess fluid in the ISF spaces

Question 3

What is ascites?

Answer 3

Build up of excess fluid in body cavities

Question 4

What are the two main causes of oedema?

Answer 4

1. Too much protein in ISF (due to blocked lymphatics or leaky capillaries)
2. Inactivity of animal - the lymphatic system requires muscle and tissue movement in order to move lymph through the system

Question 5

Describe the characteristics and functions of the lymphatic capillaries

Answer 5

Gather excess tissue fluid
Found everywhere except Brain
very permeable to larger molecules in order to collect excess proteins
They are blind capillaries (i.e. there is no arterial side)
Known as lacteals in the small intestine where they absorb the products of fat digestion producing chyle

Question 6

Describe the characteristics and functions of the lymphatic vessels

Answer 6

Have valves to prevent backflow of lymph
Join up lymphatic capillaries and lymph nodes
Thin walled collapsible tubes
No smooth muscle in walls- rely on muscle and tissue movement

Question 7

Describe the structure of the lymph nodes

Answer 7

Have an indented region called a hilus where afferent vessels enter and efferent vessels exit and go to a lymphatic duct
Lymph nodes are surrounded by a tough connective tissue capsule
Made up of masses of lymphoid tissue made up of nodules which are held together by a network of connective tissue strands called traberculae
Between the nodules and the traberculae are spaces through which the lymph pass called the lymph spaces

Question 8

Describe the function of the lymph nodes

Answer 8

Filter bacteria and foreign matter out of the lymph
Provide fresh B lymphocytes for circulation
Produce some antibodies and antitoxins to prevent infection (humoral immunity)

Question 9

What are the 2 main lymphatic ducts

Answer 9

Thoracic Duct and the R lymphatic

Question 10

Where does the Right lymphatic duct drain from and empty into?

Answer 10

Drains the Right side of the head, neck, thorax and the right forelimb. Empties into the right subclavian vein which then drains into the right jugular vein

Question 11

What does the thoracic duct drain and drain into?

Answer 11

It originates as the ‘Cisterna Chyli’ in the abdomen into which all the lower body lymph empties. It then moves cranial into the thoracic cavity through the diaphragm. It moves up the right side of the body and moves over to the left at T6 then runs behind the heart to the neck where it joins the left tracheal duct. It collects lymph from the left side of the upper body and the left forelimb. It empties into the left subclavian vein at the junction with the left jugular vein.

Question 12

What is a Chylothorax?

Answer 12

Occurs when Chyle leaks out of a damaged thoracic duct

Question 13

Where is the Parotid Lymph node found and what does it drain?

Answer 13

Found caudal to the temporomandibular joint and receives lymph from the dorsal half of the head

Question 14

What drains into the mandibular lymph node?

Answer 14

Receives lymph from the head

Question 15

Where is the superficial cervical lymph node found

Answer 15

usually 2 or 3 on each side of the neck

Question 16

Where is the popliteal lymph node found

Answer 16

Caudal to the stifle joint

Question 17

Where is the prescapular lymph node found

Answer 17

base of the neck, cranial to scapula

Question 18

Where is the axillary lymph node found?

Answer 18

In the axilla (armpit)

Question 19

Where is the superficial inguinal lymph node found?

Answer 19

Dorsal to mammary gland between the thigh and abdominal wall

Question 20

Name the 4 other lymphatic tissues

Answer 20

Spleen, Thymus, Tonsils, Peyer’s Patches

Question 21

Where is the spleen found?

Answer 21

Within the greater omentum closely attached to the greater curvature of the stomach

Question 22

What are the 4 functions of the spleen?

Answer 22

1. Storage of Blood (reservoir of RBCs + platelets)
2. Destruction of worn out red blood cells
3. Filters out foreign particles and bacteria + phagocytic cells destroy them
4. Production of lymphocytes

Question 23

Where is the Thymus found?

Answer 23

Lies in the cranial thoracic inlet

Question 24

What are the functions of the Thymus

Answer 24

Active in late foetal +early life - responsible for production of T lymphocytes that give rise to the cell-mediated immune response. It regresses during puberty and then will eventually almost completely disappear

Question 25

Where are the tonsils found and what is their function?

Answer 25

Found in pharynx - act as a first defence against microorganisms that enter via the mouth

Question 26

What is the name of the lymphoid tissue found in the small intestine? What is their function?

Answer 26

Peyer’s Patches. Help combat the numerous potential infections that enter via the gastrointestinal tract

Question 27

What is the function of the immune system?

Answer 27

Prevents invasion of foreign matter + microorganisms (antigens) by removing them or neutralising them

Question 28

What are the 2 types of immunity

Answer 28

Humoral Immune Response and Cellular Immune Response

Question 29

What is the Humoral Immune Response?

Answer 29

Production of antibodies by B lymphocytes in response to recognition of antigens.
B lymphocytes develop from cells in the liver, spleen and bone marrow
They convert to plasma cells which produce antibodies and some revert to memory cells.

Question 30

When is peak antibody production?

Answer 30

10 days after initial exposure

Question 31

What is the Cellular Immune Response?

Answer 31

Sensitising of T lymphocytes to specific antigens - they recognise and help B lymphocytes or macrophages function more efficiently.
T lymphocytes are produced initially from thymus which then migrate to lymph nodes, spleen + Peyer’s patches

Question 32

What is the difference between active and passive immunity

Answer 32

Active immunity is when the animal fights off the antigen itself
Passive immunity is when the animal directly receives ready-made antibodies directly + does not produce own. - These get broken down really quickly and have no memory cell components.