Lymphatic system and hematopoietic organs Flashcards
What is the lymphatic system?
Tissues and organs which produce, store and carry white blood cells
What does the lymphatic system do?
Fight infections and other diseases
What does the lymphatic system include?
Bone marrow
Spleen
Thymus
Lymph nodes
Lymphatic vesels
What does the lymphatic system filter?
Pathogens from the blood
3 parts of the lymphatic system
Lymphatic
Lymph nodes
Lymphoid organs
What fluid does the lymphatic system clean?
The interstitial fluid/extracellular fluid
What is extracellular fluid similar to?
Plasma
Different name for white blood cells
Lymphocytes
Which are our infection-fighting cells?
White blood cells
Is the lymphatic system one way/unidirectional or bi-directional?
Unidirectional
Primary function of the lymphatic system
Transport excess interstitial fluid from the intertital space back to the blood circularion
What does the lymphatic system use to transport the interstitial fluid back to the blood circulation?
Thoracic duct
Does the blood circulation have a one way or bi-directional course?
Bi-directional
What are the lymphatic vessels that come before the lymph nodes called?
Afferent lymphatic vessels
What are the lymphatic vessels that come after the lymph nodes called?
Efferent lymphatic vessels
Do lymphatic capillaries have a continuous basal membrane?
No it has a discontinuous basal membrane
Where are the elastic fibers found?
Only the capillaries
What kind of junction I found in the lymphatic cappilaires?
Button like junction
What kind of junction I found in the lymphatic ducts?
Zipper like junctions (has to be tight)
Are there valves in the lymphatic vessels?
Yes
What is the part of the vessels between two valves called?
Lymphangion
Different name for Lymphangion
Primitive hearts
4 types of external compression of the lymphatic vessels
Skeletal muscles
Cardiac muscle
Smooth muscles
Intestinal peristalsis
What happens when there is lymphatic pump dysfunction?
Lowered lymph flow
Increased Edema formation
Increased inflammatory cytokines and cells retention and local immune deficiency
Does the lymphatic system have a central pump?
No
What does the right lymphatic duct drain?
The right upper part of the trunk, right upper limb and right side of the head and neck
What are lymphoid organs classified as?
Primary or secondary organs
Which are the primary lymphoid organs?
Thymus and bone marrow
What are the primary lymphoid organs responsible for?
The production and maturation of lymphocytes
Which are the secondary lymphoid organs?
Spleen
Peyer’s patches
Appendix
Tonsils
Lymph nodes
What are the secondary lymphoid organs responsible for?
Further maturation of lymphocytes and initial of immune
What kind of organs are lymph nodes?
Full organs
Where are lymph nodes located?
Along the course fo the lymphatic collectors
What do the lymph nodes contain?
Lymphocyte B
Lymphocyte T
Shape of lymph nodes
Ovoid/bean shape
Size of lymph nodes
few mm - 1 cm
Where does lymphocyte B originate?
Bone marrow
Where does lymphocyte T originate?
Thymus
Are lymph nodes solid or hollow organ?
Solid organ
What is the lymph node built up of?
Capsule
Parenchyma
Trabecular of the capsule hilum
What is the stroma of the lymph node made up of?
Dense connective tissue and reticular stroma
Where in the lymph node are the plasma cells found?
In the medulla
Where in the lymph node are the macrophages cells found?
The medulla
Where in the lymph node are the lymphocytes cells found?
The medulla
How many efferent vessels from each lymph node?
1
How many afferent vessels in each lymph node?
Several
When does the follicles goes from primary to secondary?
When the b-cells go from naive to memory b-cells
What does the cortex of an unstimulated lymph node consist of?
Primary follicles composed of naive B cells
What are naive B cells?
Small, mature lymphocytes with condensed chromatin and scant cytoplasm
What is the location of the maturation of T-lymphocytes?
Thymus
Where is the thymus located?
Mostly in the anterior mediastinum and small part in the neck
Retrosternal
Is the thymus paired or unpaired?
Unpaired
What is each lobe of the thymus formed by?
A cortex and a medulla
Name of the neck of the thymus
Cornua of the thymus
Name of the lobes of the thymus
Thymic lobes
What is found inside the capsule of the thyroid?
The parenchyma (lymphoid tissue)
4 cells types of the thymus
T lymphocytes
TEC (thyme endothelial cells)
Macrophages
Dendritic cells
What allows for thymus homing?
Markers of the cell surfaces
What is positive selection?
Survival signal
What is negative selection?
Death signal
2 types of early fatal TEC
cTEC (cortex)
mTEC (medulla)
In which bones is there bone marrow?
Long bone
How much of total body weight is made of bone marrow?
3-5%
Where does hematopoiesis take place?
Bone marrow
What does the spleen consist of?
Large encapsulated mass of vascular and lymphoid tissue
Where is the spleen situated?
Upper left quadrant of the abdominal cavity
Which is the largest secondary lymphoid organ?
The spleen
Main spleen function
Destroy aged erythrocytes, aged platelets and repair young erythrocytes
What is the color and consistency of the spleen?
Dark red
Soft
What takes over hemocatheresis if the spleen is removed?
The liver
2 surfaces of the spleen
Diaphragmatic surface (external)
Visceral surface (internal)
Which surface of the spleen is convex?
The diaphragmatic surface
Which ribs does the spleen project on?
9-11th
Which rib is at the mid axis of the spleen?
10th
4 impressions on the visceral surface of the spleen
Gastric impression
Renal impression
Pancreatic impression
Colic impression
3 borders of the spleen
Superior/anterior border
Inferior/posterior border
Internal border
How much is the spleen covered by the peritoneum?
Entirely
Which artery supplies the spleen?
Splenic artery
Which vein drains the spleen?
Splenic vein
Which is the largest branch of the celiac trunk?
The splenic artery
What is white pulp in the spleen made of?
Lymphoid tissue
What does the white pulp in the spleen do?
Immune response
What does the red pulp in the spleen do?
Filtration of the blood (hemocateresis)
What does the splenic artery branch into when entering the hilum?
Trabecular arteries
What does the trabecular arteries in the spleen branch into when entering the white pulp?
Central arterioles
What are the central arterials in the spleen covered by?
Seath of lymphocytes
What does the central arterioles branch into when entering the red pulp?
Penicillar arterioles
What do the penciller arterioles branch into?
Terminal capillaries
What does the sinusoid of the spleen do?
Removal of damaged and aged erythrocytes
Where in the spleen does immune screening happen?
White pulp
What does the interstitial fluid enter the lymphatic system through?
Small lymphatic capillaries (internal or terminal lymphatics)
What are the larger vessels in the lymphatic system called?
Pre-collectors
Collectors
Trunks
Ducts
What is the interstitial fluid called when inside the lymphatics?
Lymph
What prevents retrograde flow in the lymph vessels?
One-way valves (like in veins)
What can lymph contain?
Proteins
Minerals
Fats
Nutrients
Cancer cells
Foreign invaders
Infection-fighting white blood cells
What does the lymphatic vascular system regulate?
Tissue fluid
Homeostasis
Immune cell trafficking
Absorption of dietary fats
Primary function of the lymphatic system?
Transport excess interstitial fluid from the interstitial space back to the blood circulation via the thoracic duct
Does the lymphatic system play an important role in the dissemination of cancer cells?
Yes
At which level does the lymphatic circulation start?
At the capillary level
Do pre-collector vessels have valves?
Yes
Which vessels have propulsive activity?
Afferent and efferent lymphatic vessels
5 places where the major lymphatic trunks can be found
Intestinal
Lumbar
Bronchomediastinal
Subclavian
Jugular
Name of 2 lymphatic ducts
Thoracic and right lymphatic
Are lymphatic capillaries blind ends?
Yes
How much are lymphatic endothelial cells covered by basement membrane?
Only partially
What facilitates interstitial fluid and cellular entry into the lymphatic capillaries?
The button structures
What anchors the lymphatic epithelial cells to the elastic components of the extracellular matrix?
Button structures
2 routes of entry for interstitial fluids to the lymphatic capillaries
Paracellular
Transcellular
What do lymphatic capillaries converge into?
Precollectors
What do precollerctors converge into?
Lymphatics
Where are zippers located?
Among the collector lymphatic epithelial cells
Which lymphatic vessels have complete basement membrane and smooth muscle cell layers?
Lymphatics
What allows for unidirectional lymph flow?
Lymphatic valves
Which junctions are continuous, button or zipper?
Zipper
What acts as primary valves for fluid and cell entry into lymphatics ?
Button junctions
Which endothelial cells have button-like junctions?
Endothelial cells of initial lymphatics
Which vessels have zipper-like junctions?
Collecting lymphatics and blood vessels
Which junctions create the endothelial barrier in collecting lymphatics and blood vessels?
Zipper-like junctions
What makes it possible for lymphangions to perform rhythmic contractions?
The fact that they are innervated with sympathetic and parasympathetic nerves
What does the rhythmic contractions of the lymphangion do?
Pushes the lymph forward
What is the propulsion of lymph a result of?
The combination of both active and passive mechanisms
Do lymphatic capillaries have basement membranes?
No they lack basement membranes
Are larger collecting lymphatics permeable?
No impermeable
What transport lymph back to the venous circulation?
Collecting lymphatics
Does the collecting lymphatics transport the lymph at high or low pressure
Low as it operates without a central pump
Since the collecting lymphatic are a low pressure transport system what have they developed to facilitate fluid transport?
Features such a valves and smooth muscle cells which provide an intrinsic pumping force
Which are the 2 largest lymphatic vessels?
Trunks and ducts
Which lymphatic duct drains the most, the right lymphatic duct or the thoracic?
The thoracic (3/4th of the body)
Which trunks drains the lymph of the abdomen and pelvis?
Left and right lumbar trunks
Intestinal trunk
Which trunks drains the lymph of the head and neck?
Right and left jugular trunks
Which trunks drains the lymph of the upper limb?
Right and left subclavian trunks
Which trunks drains the lymph of the thoracic viscera?
Right and left broncomediastinal trunks
Which is the largest duct in the body?
The thoracic duct
Where does the thoracic duct originate?
The cisterna chyli
Where is the cisterna chyli?
In the abdomen at level of T12
How does the thoracic duct pass into the thorax?
Through the aortic hiatus of the diaphragm
Where does the thoracic duct run?
Between the aorta (on the left) and the azygos vein (on the right) and posteriorly to the oesophagus
Where does the thoracic duct end?
At the confluence of the internal jugular vein with the left subclavian vein
How much of the whole body lymph does the thoracic duct drain?
3/4ths
Is the right lymphatic duct constant?
No
Where does the right lymphatic duct empty?
Into the right subclavian vein
What do high endothelial venules allow for?
The entry of the lymphocytes into the node
What happens to the lymph once its inside the lymph node?
It is filtered by immune cells of the parenchyma (mainly B and T lymphocytes)
What does the cortex of an UNSTIMULATED lymph node consist of?
Primary follicles composed of naive B cells with an underlying meshwork of follicular dendritic cells
What happens when a lymph nodes becomes activated by being exposed to antigen?
Germinal centers form in the center of B cell follicles
Primary follicle cells are pushed to the periphery where they form a mantle zone around the germinal center
What makes up the mantle zone?
Primary follicles and a few memory B cells
What is a secondary follicle made up of?
A germinal center and surrounding mantle zone
What is a sentinel lymph node?
The first lymph node to which cancer cells are most likely to spread from a primary tumor
Can there be more than one sentinel lymph node?
Yes
Which organ controls and harmonises the entire immune system and the immune functioning of the organism?
The thymus
Where do T-progenitor cells replicate and undergo maturation?
In the thymus
What is the thymus covered by on the side?
Mediastinal part of the pleura parietalis
Which large vessels and nerves run behind the thymus?
Aortic arch
Brachiocephalicae vein
Superior vena cava
Where do large vessels and nerves run in relation to the thymus?
Behind
What is the thymus connected to the thyroid gland by?
The thyrothymic ligament
What moulds the shape of the thymus?
Adjacent structures
What lies anteriorly to the thymus?
Sternohyoid and sternothyroid muscles and fascia
Manubrium sterni
Which vein might be partly embedded in the thymus?
The left brachiocephalic vein
What is the thymus in contact with posteriorly?
Vessels of the superior mediastinum
Upper part of the thoracic trachea
Anterior surface of the heart
What cells types are found in the thymus?
Maturing T lymphocytes
Thymic endothelial cells (TEC)
Macrophage
Dendritic cells
What is positive selection?
Survival signal
What is negative selection?
Death signal
Which cells enter the thymus to begin commitment to the T cell lineage?
Bone marrow derived lymphoid progenitor cells
What does positive selection delineates selection of thymocytes into?
CD4, T-helper
CD8, cytotoxic T cell lineage
Where do the cells migrate in the thymus after positive selection?
To the medulla
What mediates negative selection in the thymus?
mTECs
What happens to the cells in the thymus when they after positive selection go to the medulla?
They go through negative selection
What does the process of thymopoiesis result in?
A population of peripheral blood and lymphoid sites with naive CD4+ and CD8+ T cells and CD4+ regulatory T cells (tregs)
What does the establishment of self-tolerance in the thymus depend on?
Promiscuous gene expression (pGE) of tissue-restricted antigens (TRAs) by TECs
What does the spleen consist of?
A large encapsulated mass of vascular and lymphoid tissue
Which quadrant of the abdominal cavity is the spleen situated in?
Upper left/left hypochondrium
Between what is the spleen located?
Between the fundus of the stomach and the diaphragm
Which position is the spleen in?
Supramesocolic
Is the spleen entirely lined by the peritoneum or only partly?
Entirely
What is the supralateral aspect of the spleen shaped by?
The left dome of the diaphragm
What is the inferomedial aspect of the spleen shaped by?
The splenic flexure of the colon, the left kidney and the stomach
2 main functions of the spleen
Destroying aged erythrocytes (hemocatheresis) and aged platelets (catharsis of the platelets)
Repair young erythrocytes (pitting)
What does the spleen process, blood or lymph?
Blood (its a second lymphoid organ)
What does the spleen have reservoirs for?
Granulocytes and platelets
Which is the external surface of the spleen?
Diaphragmatic surface
Which is the internal surface of the spleen?
Visceral surface
Which ribs does the projection of the spleen on the thoracic cage correspond to?
9th, 10th and 11th rib
Which ligaments hold the spleen to the abdominal wall?
Folds of peritoneum:
Splenorenal
Phrenicocolic
Phrenicosplenic
Gastrosplenic ligament
What attaches the spleen to the stomach?
The gastrosplenic ligament
Which is the largest branch of the celiac trunk?
The splenic artery
Where is the fibrous capsule of the spleen thick?
At the level of the hilum
2 main components of the spleen
Red pulp
White pulp
What is the white pulp of the preen composed of?
Lymphoid tissue
What does the splenic artery divide into when it enters the hilum?
Trabecular arteries
What does the trabecular arteries follow?
The course of the trabeculae
What are the branches of the trabecular arteries that enters the white pulp called?
Central arterioles
What are the central arterioles surrounded by?
A sheath of lymphocytes
What happens to the death of lymphocytes that surround the central arterioles when they leave the white pulp and enter the red pulp?
It is lost
What are the branches of central arterioles in the red pulp called?
Penicillar arterioles
2 routes of blood flow though the splenic red pulp?
Open circulation
Closed circulation
What is blood enclosed by in the closed circulation of the red pulp?
Epithelium cells
What is the sinusoid of the human spleen like?
Barrel-like
What does the sinusoid of the human spleen do?
Remove damaged or aged erythrocytes
Permits migration of leukocytes from the cords of billroth into the circulation
How much of the blood in the spleen goes through the open circulation?
90%
In which circulation of the spleen does immune screening take place?
Both
What does the blood drain through in the open circulation of the spleen?
Through the walls of the capillaries
What does the blood undergo when crossing the wall of the sinusoids to reenter the circulation in the open circulation?
Macrophage selection
What happens to the capillaries in the closed circuit of the spleen?
It does directly into the sinusoids
What lines the sinusoids?
Incomplete endothelium that is unique to the spleen
What are the endothelial cells of the sinusoids called?
Stave cells
What are stave cells connected by?
Intercellular junctions which alternate with intercellular slits
What doe white pulp have the same organisation as?
Lymphnodes
What is the term for unencapsulated lymphoid tissue that exists in the walls of the alimentary, respiratory, reproductive and urinary tracts and the skin?
Mucosa-associated lymphoid tissue (MALT)
Subclasses of mucosa-associated lymphoid tissue
Gut-associated lymphoid tissue (GALT)
Bronchus-associated lymphoid tissue (BALT)
Where are the lymphoid cells of MALT located?
In the lamina proprietor and the submucosa as discrete follicles or nodules
What is the Waldeyer’s ring?
Circumpharyngeal ring of MALT which surrounds the openings into the digestive and respiratory tracts
What is the Waldeyer’s ring made up by?
The tonsils and smaller collections of lymphoid tissue
