Lymph, Spleen, Thymus Flashcards
Lymph is extra fluid that is not taken up by the capillary bed; it is (cell-rich / cell-poor) fluid
Lymph is extra fluid that is not taken up by the capillary bed; it is cell-poor –> there are sometimes WBCs present but not many
Lymph is normally clear but may be white in the regions draining the _
Lymph is normally clear but may be white in the regions draining the small intestine
_ bring more fluid into the capillaries than _ can drain, generating the lymph
Arterioles bring more fluid into the capillaries than venules can drain, generating the lymph
Lymph nodes are made up of aggregates of _
Lymph nodes are made up of aggregates of B cells and T cells; functions to filter the lymph and orchestrate immune responses
How does lymph move and prevent backflow?
Lymph is carried via lymphatic vessels throughout the body to the nodes
* Valves prevent backflow
* Peristalsis (smooth muscle contraction) helps it move
Identify components
S= subcapsular sinus
F= follicles
P= paracortex
What is the function of the labeled structure
This shows a lymphatic vessel with a valve- the valve prevents backflow of lymph
Identify this
This is a lymphatic vessel found in muscle
The right lymphatic duct collects _
The right lymphatic duct collects lymph from right arm and right half of face, neck, chest, back
The right thoracic duct empties into _
The right thoracic duct empties into right subclavian vein
The majority of lymph (from left upper body and the entire lower body) drains into _
The majority of lymph (from left upper body and the entire lower body) drains into thoracic duct
* Thoracic duct later drains into left subclavian vein
Cysterna chyli is a sac at the lower end of the thoracic duct that collects _
Cysterna chyli is a sac at the lower end of the thoracic duct that collects fatty milky-white lymph from the gut
Identify features of the lymph node
Macrophages originate in the _ and mature in the _
Macrophages originate in the bone marrow and mature in the connective tissue
What does the Pp structure tell us about this macrophage?
Pp = pseudopodia or “filopodia” which is a ruffled boarder that can be seen when the macrophage is active
Name the structures that tell us this is an active macrophage
Active macrophages have:
* Pseudopodia
* Phagocytic vacules
* Lysosomes
* Mitochondria
* Residual bodies
* They also have a kidney-shaped or horseshoe shaped nucleus
What are 3 main functions of macrophages
Macrophages:
1. Phagocytosis to remove large particulate matter
2. Assist with immune response by presenting antigens to T lymphocytes
3. Secrete substances to assist in wound healing
Identify the cells depicted
B lymphocyte –> plasma cell
How can we identify plasma cell?
Plasma cell features:
* Clockface nucleus (heterochromatin)
* Basophilic
* Halo due to the golgi (pale area)
The B cells are concentrated at _ region of lymph node
The B cells are concentrated at cortex region of lymph node
The T cells are concentrated at the _
The T cells are concentrated at the paracortex
* Called the “thymus-dependent region”
Primary follicle contains _
Secondary follicle contains _
Primary follicle contains small, naive B cells
Secondary follicle has been exposed to antigen and is prepared to fight infection
(Primary/ secondary) follicles contain a mantle zone and germinal center
Secondary follicles contain a mantle zone and germinal center
(Mantle zone/ germinal center) is composed of cells that are ready to fight off infection; cells are loosely packed
Germinal center is composed of cells that are ready to fight off infection; cells are loosely packed
Mantle zone is composed of _
Mantle zone is composed of small normal B cells that are closely packed
The _ is a special venule that will recognize T and B cells and pull them out of the bloodstream and into the lymphatic
The high endothelial venule is a special venule that will recognize T and B cells and pull them out of the bloodstream and into the lymphatic
This process of moving WBCs between the endothelial cells to exit the vascular system into the interstitium of the lymph is called _
This process of moving WBCs between the endothelial cells to exit the vascular system into the interstitium of the lymph is called diapedesis
* Carried out by high endothelial venules
* After this happens the WBCs get sorted; B cells to follicles, T cells in paracortex
The high endothelial venules are found in the _ region
The high endothelial venules are found in the paracortex
High endothelial venules are uniquely made up of _ cells
High endothelial venules are uniquely made up of simple cuboidal epithelium
What are the structures marked V?
High endothelial venules
After the T/B cells get pulled into the lymph via the high endothelial venules, they will later rejoin the circulation via the _
After the T/B cells get pulled into the lymph via the high endothelial venules, they will later rejoin the circulation via the efferent lymphatic vessel as efferent lymph
_ are columns of B cells, plasma cells, and macrophages
Medullary cords are columns of B cells, plasma cells, and macrophages
_ are “vessels” in between the medullary cords; allows lymphocytes to flow through and exit the lymph node
Medullary sinus are “vessels” in between the medullary cords; allows lymphocytes to flow through and exit the lymph node
Identify medullary cords and sinus
What is the pathway of lymphatic flow?
- Afferent lymphatic vessels
- Subcapsular sinuses
- Peritrabecular sinuses
- Medullary sinuses
- Efferent lymphatic vessel
What is the function of structures MC and MS?
What cells do we see here in the medullary sinus?
Incoming lymphocytes
Macrophages
What is the flow of blood through the lymph node?
- Artery (hilum)
- Arterioles
- Capillary bed
- Venule
- Vein (hilum)
What is the “hilum”?
Hilum is just the region where blood vessels enter and leave
The primary lymphoid organs are _
The secondary lymphoid organs are _
The primary lymphoid organs are bone marrow, thymus
The secondary lymphoid organs are lymph nodes, tonsils, spleen, MALT
Which thymus is adult and which is infant?
Adult thymus is infiltrated with adipose tissue
What is the function of Hassall’s corpuscle
Hassall’s corpuscle has an unknown function; but tells us that this is the thymus and we are in the medulla
* They are layered concentric collections of kertatinized epithelial reticular cells
* Once we identify the thymus, we can identify that we are looking at T lymphocytes
T cells migrate from _ to _ and undergo _ along the way
T cells migrate from cortex to medulla and undergo apoptosis along the way
* Many of the unfit T cells are dying along the way
Identify the tissue and cells
Tissue: thymus medulla
Epithelial cells: abundant in the medulla
T cells: basophilic
What are the three components of the blood-thymus barrier?
Blood thymus barrier:
1. Capillary endothelium and basal lamina
2. Perivascular connective tissue (macrophages)
3. Epithelial reticular cells and basal lamina
The purpose of the blood-thymus barrier is to make sure that antigens in the _ don’t reach the _
The purpose of the blood-thymus barrier is to make sure that antigens in the bloodstream don’t reach the developing T cells in the cortex
What happens to T cell that strongly bind self-antigen?
Apoptosis
What happens to T cells that weakly bind self-antigen
They pass the test and move on to the circulation/ periphery
What happens to T cells that have intermediate binding to self-antigen?
They become Treg cells
VDJ recombination of T cells occurs in _ region of the thymus
VDJ recombination of T cells occurs in subcapsular space region of the thymus
T cells undergo positive selection in _ region of the thymus
T cells undergo positive selection in cortex of the thymus
T cells undergo negative selection in _ region of the thymus
T cells undergo negative selection in medulla of the thymus
_ involves an abnormal development of the 3rd and 4th pharyngeal pouches which leads to a congenital absence of the thymus and parathyroid glands
DiGeorge Syndrome involves an abnormal development of the 3rd and 4th pharyngeal pouches which leads to a congenital absence of the thymus and parathyroid glands
What does the immune system look like in a patient with DiGeorge syndrome
Abnormal cell-mediate immunity (lack of thymus = lack of T cells)
&
Relatively normal humoral immunity
Complete DiGeorge means _
“Complete” DiGeorge means you do not have a thymus at all and do not have any T cells
A consequence of DiGeorge syndrome is low _ due to lack of parathyroid –> leads to tetany
A consequence of DiGeorge syndrome is low calcium due to lack of parathyroid –> leads to tetany
DiGeorge syndrome is associted with a microdeletion of chromosome _
DiGeorge syndrome is associted with a microdeletion of chromosome 22
CATCH 22:
Cardiac defects
Abnormal facies
Thymic hypoplasia
Cleft palate
Hypocalcemia
What are the functions of the spleen?
Spleen:
* Filters blood and removes old RBCs/ platelets
* Stores T and B cells
* Stores platelets
* Fetal spleen has hematopoiesis
The red pulp carries out the (filter/ storage) function of the spleen
The red pulp carries out the filter function of the spleen
* Takes up most of the spleen
* Filters RBCs
* Involved in lymphocyte development
The white pulp carries out the (filter/ storage) function of the spleen
The white pulp carries out the storage function of the spleen
Identify the tissue
Spleen
What is the pathway of blood through the spleen?
- Splenic artery
- Trabecular artery
- Central artery
- Penicillar artery
- Splenic sinusoids/ cords
The central artery is covered by _ and this is in the white pulp
The central artery is covered by periarteriolar lymphoid sheath and is in the white pulp
The splenic follicles are in the (white/red) pulp
The splenic follicles are in the white pulp
The periarteriolar lymphoid sheath (PALS) forms a sheath around the central arteriole and contains _ cells
The periarteriolar lymphoid sheath (PALS) forms a sheath around the central arteriole and contains T cells
* These T cells are removing invaders in the blood
Splenic follicles are in the white pulp and contain mostly _ cells
Splenic follicles are in the white pulp and contain mostly B cells
* Making antibodies
* We have a germinal center, mantle zone, and marginal zone
The germinal center of the follicles in the spleen contain _ cells
The germinal center of the follicles in the spleen contain activated B cells
The mantle zone of the follicles in the spleen contain _ cells
The mantle zone of the follicles in the spleen contain resting B cells
The marginal zone is the first site where splenic cells make contact with the blood; what happens here?
Marginal zone: link between B cells and T cells
* Circulating T and B cells are stored
* Macrophages make contact with pathogens in the blood and present to T cells for removal
Splenic sinusoids are large, leaky capillaries formed by _ cells
Splenic sinusoids are large, leaky capillaries formed by stave cells
* The splenic sinusoids and splenic cords make up the red pulp (filter functions)
_ is extravascular structure surrounding the sinusoids that contains plasma cells and macrophages
Splenic cords is extravascular structure surrounding the sinusoids that contains plasma cells and macrophages
* The splenic sinusoids and splenic cords make up the red pulp (filter functions)
In open circulation, RBCs percolate through the splenic cords –> healthy RBCs _ and damaged ones _
In open circulation, RBCs percolate through the splenic cords –> healthy RBCs re-enter closed circulation and damaged ones get phagocytoses
What is the function of this structure?
Filtration
(Thymus/ spleen/ lymph nodes) have cortex and medulla
Thymus & lymph nodes have cortex and medulla
(Thymus/ spleen) has lymhoid follicles/nodules
Spleen has lymhoid follicles/nodules
* So do lymph nodes
(Thymus/ spleen) has a hilum
Spleen has a hilum
* So does lymph node
