Lymphatic system

Question 1

Lymph

Answer 1

Coagulable fluid in the lymphatic system that has similar contents to plasma.

Except:
Contains white blood cells
Lipids

The word ‘lymph’ only applies to interstitial fluid in the lymphatic vessels.

Question 2

Interstitial fluid

Answer 2

Environment surrounding tissues

Receives nutrients from arteries and removes waste products from veins.

When in the lymphatic vessels, interstitial fluid is called ‘lymph’

Question 3

Pathway of lymph through lymphatic system

Answer 3

Arterial capillary --->
Interstitial space ---->
Lymphatic capillary ----->
Afferent lymphatic vessel ---->
Lymph node ----->
Efferent lymphatic vessel ---->
Lymphatic trunk ----->
Collecting duct ----->
Jugular/ subclavian vein.

Question 4

Lymphatic tissues around the body (8)

Answer 4

Cervical nodes
Thymus
Axillary nodes
Thoracic duct
Spleen
Iliac nodes
Bone marrow
Interstitial nodes

Question 5

Lymphatic capillaries

Answer 5

A plexus formed in tissue space

10-50 micrometres in diameter.

Composed of unicellular endothelial cells that allow unidirectional flow of lymph due to overlapping of cells.

Contains pores in the endothelial cells, allows flow of lymph into vessel.

Question 6

Function of the lymphatic system

Answer 6

Drains fluid from tissue- prevent oedema

Absorbs fatty acid from the intestines

Provides immunological defence, through white blood cells.

Question 7

Pathological significance of the lymphatic system

Answer 7

Can allow the spread of cancer- metastasis

Can allow the spread of infection

Question 8

Lacteals

Answer 8

Lymphatic capillaries in the small intestines that carries chyle.

Chyle has more lipids compared to normal interstitial fluid.

Question 9

Lymphatic afferent vessels

Answer 9

Vessels that carry lymph to the lymph nodes.

Formed from the joining of lymphatic capillaries.

Composed of three layers:
Endothelium- inner layer, one cell thick
Tunica intima- Middle layer, composed of smooth muscle
Tunica adventitia: Outer layer, connective tissue. This prevents vessel from expanding.

Contains valves- prevents backflow of lymph, due to low pressure in vessels,

Question 10

Describe the flow of lymph through a lymph node

Answer 10

Afferent lymphatic vessel---->
Subcapsular sinus ---->
Trabecular sinus ---->
Cortex ----->
Medulla ----->
Efferent lymphatic vessel

Question 11

Lymphatic nodules

Answer 11

Smaller version of lymph nodes without a capsule.

Formed from a collection of lymphatic tissue.

Located:
Tonsils
Peyer’s patches in the small intestines
Appendix

Nodules act as a first line of defence due to their locations. This is what pathogens would usually meet first if they enter through the mouth or stomach.

Question 12

Structure and function of the lymph nodes

Answer 12

Lymphatic tissue found in clusters, around 600 in the body. This is where lymph is processed.

Structure:

Capsule- outer layer of connective tissue. Prevents node from swelling

Subcapsular sinus- space between cortex and capsule

Trabecular sinus: drains lymph from the subcapsular sinus, connects to the cortex

Cortex: divided in outer and paracortex region.
Outer contains B cells and macrophages.
Paracortex contains T cells.

Medulla: The deepest region of the node. Contains B cells and macrophages

Question 13

Lymphatic chain

Answer 13

Line of lymph nodes connected by lymphatic vessels.

A primary node is at the start of the chain, whilst the terminal node is at the end of the chain.

This allows all the lymph to be filtered efficiently.

Question 14

How is lymph moved in the lymph vessels?

Answer 14

Contraction of skeletal muscles.

Respiratory movements

Contraction in the lymphatic vessel walls.

Question 15

How is lymph moved into the lymphatic capillaries?

Answer 15

Filtration pressure:

build up of interstitial fluid is forced into the capillaries.

Question 16

Lymphatic drainage of the breast

Answer 16

Contains a lymphatic plexus around the nipple.

75% of lymph drains out the axillary region

25% drains out the parasternal.

This is important for when cancer treatment is targetted

Question 17

Axillary lymph nodes and vessels

Answer 17

Axillary lymphatic plexus drains 75% of the breast into the axillary lymph nodes.

Lymph is also collected from the upper limb vessels.

There are around 20-30 axillary lymph nodes

The nodes drain into the subclavian trunk.

Question 18

Primary cervical lymph nodes

Answer 18

Collects lymph from the nose to the base of the neck.

Question 19

How are lymphatic vessels/ nodes classified

Answer 19

Deep or superficial

When deep: close to the viscera. Usually close to arteries
Named according to the organ is is next to
I.e Left pulmonary lymph node

When superficial: named according to the anatomical region. Usually close to veins.
I.e right superficial inguinal lymph nodes

Question 20

Spleen

Answer 20

Largest lymphatic organ, around 12cm.
Located in the left hypochondrium (below costal cartilage).
Supplies by splenic vein and artery.

Divided into:
White pulp- inner region with white blood cells. Central to the arteries.
Red pulp- outer region with red blood cells. Next to venous spaces

Functions:
Filters blood
Stores and removes platelets

Question 21

Thymus

Answer 21

Primary lymphatic organ that is larger in children. Shrinks from 70g in children to 3g in adults.

Contains 2 lobes- cortex and medulla

Located between the aorta and sternum at the T4/5 space.

Function:
Contain T cells and macrophages

Question 22

Thoracic duct

Answer 22

Left thoracic collecting duct- 40 cm in length
Vessel that ascends between the azygos vein and the oesophagus.
Passes through the diaphragm and aortic hiatus.
Extends from the base of the neck to L2

Function:
Collects chyle from the cisterna chyli and drains into the left venous angle- between the left subclavian vein and left internal jugular

Question 23

Right collect duct

Answer 23

Lymphatic vessel around 1.2cm in length, located at the right venous angle- between right internal jugular vein and right subclavian vein

Drains:
Upper right section of the trunk
The right arm
The right side of the head and neck

Formed from the joining of;
Right jugular trunk
Right subclavian trunke
Right bronchomediastinal trunk

Question 24

Jugular trunk

Answer 24

Lymphatic vessel that runs along the internal jugular vein.

There is the right and left jugular trunk.

Carries lymph from the head and neck.

Left drains into Thoracic duct whilst right drains into the right collecting duct.

Question 25

Subclavian trunk

Answer 25

Lymphatic vessels that runs along the subclavian veins.

There is a right and left subclavian trunk which both collect lymph from the upper limb of their respective sides.

Question 26

Bronchomediastinal trunk

Answer 26

Lymphatic vessel that collects lymph from the thoracic walls, viscera and upper abdominal viscera.

There is a right and left trunk which collects lymphs from their respective sides.

Question 27

Cisterna chyli

Answer 27

Lymphatic sac that collects chyle from the abdomen, lower limbs and pelvis.

Receives lymph from:
Right and left intestinal trunk
Right and left lumbar trunk

Passes chyle to thoracic duct.