L17- Lymphatic system Flashcards
function of the lymphatic system
1) Fluid balance 2) transport of fats and fat-soluble vitamins 3) Defence against invading pathogens and disease 4) storage of and destruction of aged erythrocytes
Fluid balance
- Returns fluid to the heart from tissues o Collecting excess interstitial fluid and returning it to the blood
Transport of fats and fat-soluble vitamins
Quickest way to send lipid soluble materials from the digestive system to the venous circulation
Defence against invading pathogens and disease
a. Lymph nodes and other lymphatic organs filter the lymph to remove microorganisms, parasites, foreign particles and [cancer cells] b. ‘Visiting’ T and B lymphocytes and macrophages
Storage of and destruction of aged erythrocytes
a. The spleen is responsible for this role – liver can take over after splenectomy
organisation of the lymph nodes
(1) Lymph (fluid) (2) Lymphatic vessels (3)Lymphoid tissues and organs (lymph nodes etc) (4) Cells contained within tissues and organs
lymphatics in the CNS?
no
lymph
Fluid which flows through the lymphatic vessels and lymph nodes
how much lymph produced each day
3-4 litres
what does lymph resemble and what is its pH
plasma- pH7.4
how does lymph differ from plasma
less protein
how is chyle different to lymph
lymph that arises in GI tract
what does chyle look like
- White and cloudy (fats and dissolved lipids- chylomicrons and fat-soluble vitamins)
the lymphatic system is not a
closed loop
lymphatic capillaries are
blind ended- meaning that all left over lymph is dumped into veins
lymphatic capillaries structure
smallest lymphatic vessel, endothelial cells line tightly together with some overlapping at the ends to create valves.
found penetrating into lymphatic tissue –> draining system
lymphatic capillaries are in some way comparable to
veins
how are lymphatic capillaries comparable to veins
- Low pressure system - Valves
how are lymphatic capillaries different to veins
- BUT NO CELLS NORMALLY (e.g. no RBC or WBC) - Lymph vessels have less smooth muscle
what do lymphatic capillaries do broadly
- Absorb excess interstitial fluid from interstitial tissue
how do lymphatic capillaries absorb excess interstitial fluid
- Highly porous due to Gaps in lymphatic vessels- formed between endothelial cells
what forces lymph into capillaries
oncotic pressure= when it reaches a certain level the gaps between the endothelial cells are forced open
what prevents lymph flowing in the wrong direction
the way the epithelial cells are layered forms a kind of valve- flow of fluids away from the terminals of the capillary- unidirectional
what anchors lymphatic vessels in place
endothelial cells produce RETICULIN (type 3 collagen)
once lymph has entered the capillaries outline its journey
Capillaries –> Trunks –>Ducts –> Veins
how is lymph moved unidirectionally around lymphatic vessels
Lymphatic vessels lie adjacent to capillaries, arteries and veins.
Lymphangion- compression by local veins and arteries propels lymph through the vessels
Like veins, lymphatic vessels are arranged into
superficial and deep.
deep lymphatics
e.g. in the limbs, use muscle contraction to aid lymph movement
superficial lymphatic vessels use what to move lymph
lymphangion
lymphangion
compression by local veins and arteries propels lymph through the vessels
larged lymphatic vessels are called
duct and trunks
how are ducts and trunks different to smaller lymphatic vessels
contain smooth muscle cells in their walls e.g. abdomen and thorax
ducts and trunks are quivalent to
larger veins
- Larger fibrocartilaginous valves
- Skeletal muscle and organ movement for flow
cisterna chyli
large container of chyl from GI tract (recveive lumph drainng from GI organs
the abodomen can be split into
4 quadrants
- right upper quadrant
- left upper quadrant
- right lower quadrant
- left lower quadrant
the upper right quadrant drains into
the right subclavian veins
the rest of the body drains into the
left subclavian vein
as lymph passes through the body is is filtered by
lymph nodes (600-700 in the body)
which lymph nodes are clinically important
neck (cervical), grain (inguinal) and armpit (axillae)
structure of a lymph node
- Shaped like a kidney
- Each node has multiple afferent lymphatic vessels
- Enter via the convex surface
- A single efferent lymphatic vessel
- Leaves via the concave hilum
- Each lymph node has a feeding artery and a draining vein that enters and leaves via the hilum
- Nodules on the outside of the node (cortex) with germinal centres in the middle
nodules in the cortex of lymph nodes contain
germinal centres
- which contain immune cells scuh as macrophages, dendritic cells, B and T cells
main conenctive tissue fibre in lymph nodes
reticulin produced by reticular cells
capsule is covered in collagen 3 and 1
follicular dendritic cell activation
Dendritic cells from the periphery use long processes to locate pathogen and phagocytose. The activated dendritic cell then travels to the lymph nodes via the afferent lymphatic vessels and activates T cells. This activates proliferation of B and T helper cells in the germinal centre- release of antibodies into blood via efferent lymphatic vessels.
dendritic processes
Dendritic cells have very long processes which find pathogens and T cells and activate them. Macrophages has long processes which helps macrophages with phagocytosis
B cells can
recognise antigens by themselves
T lymphocytes
must be presented the antigen by an APC
lymphadenopathy
enlarged lymph nodes
why does lymphadenopathy occur
- As lymph nodes fight infection, germinal centres fill with increasing number of lymphocytes causing the lymph nodes to swell- painful
- Cancers can metastases to lymph nodes via the afferent lymphatics to also cause swelling
-
Lymphoma- malignancy of lymphoid tissue itself
- Hodgkin lymphoma
- Non-Hodgkin lymphoma
name 5 lymphatic organs
thymus
spellen
tonsils
appendix
payers patches
the spleen is the …. of lymphatic organs
largest
where is the spleen loacted
inferior to diagram and posterior to the stomach
why is the spleen so red
Rich blood supply
Stores RBC (why its so red)
by birth the spleen is
fully formed and functional
two different type of tissue in the spleen
white pulp- in the centre
red pulp- in the cortex
white pulp
immunity
red pulp
both immmune and haemopoietic systems
function of the spleen
- Filters blood in the same way that lymph nodes filter blood
- Removal of old RBC and platelets
- Immune function- APC
- Haemopoietic function
- Retrieval of iron from RBC haemoglobin
- Erythrocytes storage
spleen clinical correlates
Spleen is very soft- rich blood supply
Rupture can lead to death through exsanguination
Surgeons often remove the spleen
after a splenectomy which organs take over removal and desctruction of ageing RBC
liver and bone marrow
splenomegaly
enlarges in response to localised infection (just like lymph nodes) and systemic infection (glandular, malaria, septicaemia)
- Can enlarge to 10X normal size
the thymus is found
superior mediastinum
structure of thymus
Has follicles with germinal centres (found through the thymus- unlike lymph nodes)
thymus and age
Fully formed and functional at birth
By late teens is mostly fat
function of thymus
maturation of marrow derived T cells into immune competent T cells - Thymic cell education
changes in thymus associated with
myasthenia gravis
tonsils found in both
nasopharynx and oropharynx
by birth tonsils are
fully formed and functional
- mainly affected in childhood
tonisl constitute
waldeyers ring
structure of tonsil
nodule resides inferior to surface invagination (crypts)- many M cells
funcion of tonsils
- Prevent antigen ingress through oral, nasal and aural (adenoids) route
- Crypts increase surface area
tonsils have numerous
Surface of epithelia have numerous microfold (m-cells). Present antigens to underlying immune cells.
when tonsils swell
due to B and T cell proliferation
the appendix is also known as
the vermiform (worm like) appendix
where is the vermiform appendix located
inferior to and attached tot he caecum (ascending colon)
structure of the appendix
- Nodule resides inferior to surface invagination (crypts)
- Many M cells in epithelial surfaces
function of appendix
- Prevents pathogen ingress through GI routes
- Prevent pathogen ingress arriving from ileum
- Crypts increase surface area
payers patches located
inferior to and attached to the side of the illium
structure of payers patches
Nodule reside inferior to surface domes.
Many m cells in epithelial surface
payers patches function
prevent pathogen ingress throguh digestion
