lymphatic system

Question 1

list the 3 components of the lymphatic system

Answer 1

1. lymph
2. lymphatic vessels
3. lymphoid tissues and organs

Question 2

list some circulatory and immune functions of the the lymphatic system

Answer 2

• returns fluids that have leaked from the vascular system back to the blood
• transports nutrients, hormones and wastes
• protects the body by removing foreign material from lymph streams
• provides site for immune surveillance

Question 3

what do lymphatic vessels do?

Answer 3

lymphatic vessels (lymphatics) form an network of drainage vessels that collect excess interstitial fluid and return it to the bloodstream. This is a one way system in which lymph flows toward the heart.

Question 4

what is lymph?

Answer 4

the interstitial fluid that has entered the lymphatics

Question 5

what are lymphatic capillaries and list their 2 structural modifications

Answer 5

lymphatic capillaries drain the interstitial space of most tissues.

1. endothelial cells overlap forming easily opened, flap-like minivalves
2. collagen filaments anchor the endothelial cells to surrounding structures so that an increase in interstitial fluid volume opens the minivalves

Question 6

what is a lacteal?

Answer 6

a lacteal is a highly specialised lymphatic capillary present in the villi of intestinal mucosa.
lacteals absorb digested fats from the intestine.
fatty lymph is called ‘chyme’

Question 7

describe the flow of lymph

Answer 7

lymphatic capillaries-collecting vessels-trunks-ducts-toward heart

Question 8

list the major trunks (hint there are 9)

Answer 8

2 jugular trunks
2 subclavian trunks
2 bronchomediastinal trunks
2 lumbar trunks
1 intestinal trunk

the first 4 drain into the thoracic duct or right lymphatic duct.
the 2 lumbar trunks and intestinal trunk drain into the cysterna chyli

Question 9

superficial lymph vessels follow…

Answer 9

veins

Question 10

deep lymph vessels follow…

Answer 10

arteries

Question 11

list the 2 lymphatic ducts and state their drainage point

Answer 11

1. Right Lymphatic Duct
2. Thoracic Duct
   these ducts empty into the blood vascular system at the junction of the internal jugular and subclavian veins in the neck (on their own side)

Question 12

list 4 factors affecting lymphatic flow

Answer 12

1. skeletal muscle contraction
2. pressure changes in thorax
3. contractions of lymphatic vessels
4. valves (prevent backflow)

Question 13

3 lymphatic cell types

Answer 13

1. lymphocytes- T, B, Natural Killer
2. auxillary immune cells-macrophages, dendritic cells
3. supporting cells-reticular cells that form CT stroma

Question 14

2 functions of lymphoid tissue

Answer 14

1. proliferation site for lymphocytes

2. surveillance for lymphocytes and macrophages

Question 15

2 types of lymphoid tissue

Answer 15

1. diffuse lymphoid tissue-loose (most common)

2. lymphoid follicles-dens;germinal centres of proliferating B lymphocytes

Question 16

list functions of lymph nodes

Answer 16

• house lymphocytes and macrophages
• activate immune system
• filter lymph

Question 17

describe the flow of lymph through a lymph node

Answer 17

lymph enters the lymph node through afferent vessels, and exits via efferent vessels.
there are few efferent vessels than there are afferent vessels, which allows time for cleansing of lymph.

Lymph flows into the node through afferent lymphatic vessels (convex surface)
Moves through subscapular sinus towards medulla
Flows through medullary sinuses
Exits via afferent lymph vessels located at the Hilum (concave surface)

Question 18

list some other lymphoid organs a part from lymph nodes

Answer 18

spleen, thymus, tonsils and Peyer’s Patches of intestinal wall

Question 19

embryologically, what do lymphatics develop as?

Answer 19

outpockets of developing veins

Question 20

embryologically, lymphoid organs develop from?

Answer 20

haematopoietic tissue

Question 21

5 functions of spleen

Answer 21

1. immunity
2. blood filter
3. reservoir
4. recycles
5. erythropoesis in the foetus
   the spleen provides a site for lymphocytic proliferation and immune function, and destroys aged or defective RBCs and blood borne pathogens. it also stores and releases the breakdown products of haemoglobin, stores platelets and acts as a hematopoetic site for the fetus.

Question 22

differentiate primary lymphoid organs from secondary lymphoid organs

Answer 22

primary:
-site of B and T cell maturation
-red bone marrow, thymus
secondary:
-mature lymphocytes first encounter antigens and become activated
-lymph nodes, spleen, appendix, tonsils, Peyer’s Patches (intestinal follicles)

Question 23

The capsule of the spleen contains smooth muscle fibres. In which situations would this organ need to contract?

Answer 23

When it needs to release blood, platelets and monocytes, e.g. severe bleeding, fight infection
this is initiated by the sympathetic nervous system

Question 24

Define the following terms:

a) Microbiome
b) Microbiota
c) Commensal
d) Probiotic
e) Pathogen
f) Dysbiosis

Answer 24

a) Microbiome-collection of microbial genomes
b) Microbiota-collection of microbes
c) Commensal-a colonising organism that is neither beneficial nor harmful
d) Probiotic-an organism that elicits health benefits to the host
e) Pathogen-an organism that is detrimental to the host or causes disease
f) Dysbiosis-loss of balance within the microbial community

Question 25

Explain how dysbiosis can potentially lead to disease

Answer 25

a) microbiome diversity increases at sites which normally have restricted diversity b) reduced diversity at sites which normally have great diversity

Question 26

Provide examples of conditions that have been associated with (i) the GIT microbiome and (ii) the vaginal/urethral microbiome

Answer 26

``` GIT microbiome associated conditions Dental caries Peptic ulceration, oesophageal and gastric carcinoma Obesity IBD IBS ``` Vaginal/urethral microbiome associated conditions Bacterial vaginosis Recurrent UTIs Susceptibility to infection during pregnancy Pre-term birth