Cardio - Histology - Vascular Tissue; Lymphoid Tissue Flashcards
What are the three layers (tunicas) of any blood vessel?
Tunica intima
Tunica media
Tunica adventitia (externa)
The lumen is wider in which, arteries or veins of comparable size?
Veins
The wall is thicker in which, arteries or veins of comparable size?
Arteries
What fiber is found in uniquely high concentrations in the aorta and other large arteries?
Elastin
What are the three types of artery?
Elastic;
muscular;
arterioles
Which arteries are elastic?
The aorta, carotids, and subclavians
What does the elastin in the aorta do?
What does the collagen in the aorta do?
Propel blood (rebound effect);
provides strength to control distension
What transition occurs in the tissues from elastic to muscular arteries?
A shift from elastic tissue to smooth muscle
What subendothelial layer is especially prominent in muscular arteries?
The internal elastic membrane
What is a normal blood pressure?
< 120 / < 80
What blood pressure is in the elevated category?
120 - 129 / < 80
What blood pressure defines hypertension stage 1?
130 - 139 systolic OR 80 - 89 diastolic
What blood pressure defines hypertension stage 2?
≥ 140 systolic OR ≥ 90 diastolic
What structure connects arterioles and capillaries?
Metarterioles
Is capillary blood flow continuous or pulsatile?
Pulsatile
(for maximum nutrient/waste exchange)
Where are precapillary sphincters located?
What are they?
Metarterioles;
bands of smooth muscle
What intermediate filaments lend structural support to capillaries?
Desmin and vimentin
What type of tissue is shown in this micrograph?
A capillary bed
What molecule promotes tight junction leakage in capillary beds?
Histamine
How do large molecules leave capillary beds?
Transcytosis
(endocytosis and then exocytosis on the other side)
What type of well-developed mesenchymal cell surrounds capillary endothelial cells and have the ability to differentiate into smooth muscle?
Pericytes
What contractile filaments are present in pericytes?
Tropomyosin;
isomyosin
What are the three types of capillary?
Continuous;
fenestrated;
sinusoidal (discontinuous)
What types of vessel in the body contain valves?
Veins;
lymphatics
Where do Purkinje cells travel?
The subendocardium
Purkinje cells are large cells containing large amounts of what substance?
Glycogen
Identify the structure with an ‘A’ in the lumen.
Identify the structure with a ‘B’ in the lumen.
A = Medium vein
B = Muscular/medium artery
Identify the areas indicated by green bars and yellow bars.
Identify the structure at the tip of the blue arrows.
Yellow bar = Tunica media
Green bar = Tunica adventita
Arrows indicate internal elastic lamina
Identify the structures labeled ‘A’, ‘B’, and ‘C’.
All three structures are components of what structure?
A = Peripheral nerve
B = Muscular artery
C = Medium vein
Neurovascular bundle
What structure is surrounded by arrows in this micrograph?
Vasa vasorum
Identify the entire structure.
Identify the area indicated by the black bar.
Identify the area indicated by the blue bar.
Identify the structure at the tip of the arrows.
Large/elastic artery
Black bar = Tunica media
Blue bar = Tunica adventita
Arrows = Vasa vasorum
The bar indicates the thickness of the wall of this structure.
Identify the structure.
Large vein/vena cava
Identify A and B.
A = Muscular artery
B = Small vein
Identify the structure at the tips of the black arrows.
Identify the structure at the tips of the blue arrows.
Black arrows = Arteriole
Blue arrows = Venule
Identify the blood vessel in this micrograph.
A fenestrated capillary
Identify the blood vessel in this micrograph.
Sinusoid
Identify this structure.
Medium/small vein
Identify the vessel.
Identify the structure indicated by black arrows.
Identify the structure indicated by black bar.
Muscular artery
Arrows = Internal elastic lamina in tunica intima
Bar = Tunica media
As you move from arteries to veins, what change would you expect to see in the relative sizes of the tunica intima, media, and adventitia?
Intima - remains the same
media - decreases in size
adventitia - increases in size
The internal elastic lamina is part of what layer of the blood vessel wall?
The external elastic lamina is part of what layer of the blood vessel wall?
The tunica intima;
the tunica media
Which blood vessels are ‘resistance’ vessels?
Which blood vessels are ‘capacitance’ vessels?
Which blood vessels are ‘conducting’ vessels?
Which blood vessels are ‘distributing’ vessels?
Which blood vessels are ‘exchange’ vessels?
Resistance - arterioles
Capacitance - veins
Conducting - elastic arteries
Distributing - muscular arteries
Exchange - capillaries
The tunica adventitia (externa) is thicker (relative to wall thickness) in which type of vessel, arteries or veins?
Veins
The tunica media is thicker (relative to wall thickness) in which type of vessel, arteries or veins?
Arteries
Describe the changes in blood pressure as blood travels out through arteries and back through veins.
Where are capillaries with extensive tight junctions especially common?
The blood-brain barrier
In what example tissues are fenestrated capillaries likely to be found?
Endocrine glands,
the intestines,
the kidneys
Organs such as endocrine glands, the intestines, and the kidneys are likely to be supplied by what type of capillary?
Fenestrated
What type of capillary is characterized by an abundance of small pores covered by a thin diaphragm?
Fenestrated
What type of capillary is found in the adrenal medulla?
Fenestrated
What is another term for sinusoidal capillaries?
Discontinuous capillaries
Which type of capillary allows for quickest exchange of material between tissues and the bloodstream?
Sinusoidal (discontinuous) capillaries
Which of the following capillary types are characterized by fenestra covered by a thin diaphragm?
Continuous
Fenestrated
Discontinuous (sinusoidal)
Fenestrated only
Which of the following capillary types are characterized by fenestra with no diaphramagtic barrier?
Continuous
Fenestrated
Discontinuous (sinusoidal)
Discontinuous (sinusoidal)
True/False.
Sinusoidal (discontinuous) capillaries are characterized by fenestra and no diaphragm, yet they have an intact basal lamina.
False.
The basal lamina is also discontinuous
In what example tissues are sinusoidal (discontinuous) capillaries likely to be found?
Liver, spleen, gallbladder
What are the two terminal vessels of the lymphatic system?
The thoracic duct;
the right lymphatic duct
What two structures can often be found acompanying a muscular artery?
A vein and peripheral nerve of proportional sizes
What structures are indicated by the arrows in this micrograph?
Red -
Orange -
Blue -
Green -
Gray -
Red - Nerve (shows perineurium)
Orange - Lymph cap
Blue - Artery (shows 2 layers of smooth muscle + a pericyte)
Green - Vein
Gray - Vein
How much of total blood volume can be held in the veins at one time?
How much of this blood can remain stationary without negative effects?
70%;
0% (venous blood is not stationary)
From smallest to largest, what are the names of vessels returning blood to the heart?
Venules,
small veins,
medium veins,
large veins
True/False.
Many large and medium veins are muscular.
True
Does cardiac contraction begin at the apex or the base of the heart?
Does cardiac contraction begin in the deep layers or superficial layers of the heart?
Apex;
deep (endocardium –> epicardium)
During microscopic examination of a tissue specimen, the pathologist notices numerous capillaries with continuous endothelium, lacking fenestrations but with many pinocytotic vesicles. Based on these observations, the tissue being examined most likely is:
A. muscle
B. liver
C. spleen
D. adrenal medulla
A. muscle
- B. liver (sinusoidal)*
- C. spleen (sinusoidal)*
- D. adrenal medulla (fenestrated)*
What are some examples of large veins?
Vena cava, portal v., splenic v., renal v.
What are some examples of medium veins?
Typically, named deep veins
(e.g. popliteal, radial, tibial)
What type of vein is the great saphenous?
A muscular (medium) vein
What vessels are typically most likely to be affected by atherosclerosis?
Large and medium arteries
Which gender is more at risk for atherosclerotic development?
Males
Describe the (very basic) components of an atheroma.
A soft lipid core + a fibrous cap
What is the ‘response to injury’ theory of atherosclerosis?
Atherosclerosis is a chronic inflammatory reaction to endothelial damage
1) Injury to the endothelium of the arterial wall
2) Tissue response of the vascular wall to the injury
Describe the basic pathophysiology of atherosclerosis.
What are three negative outcomes that may occur at a site of severe atheroma development?
Vessel stenosis;
plaque aneurysm and rupture;
vessel occlusion by thrombus
What is the difference between stable and vulnerable atheromas?
Thickness of the fibrous cap;
degree of inflammation
The collagen and ECM in atheromatous plaques are synthesized largely by what type of cell?
Smooth muscle cells
Although they decrease the risk of plaque rupture, what risk do stable atheromas have when compared to vulnerable plaques?
Increased risk of vessel stenosis
Why would rupture of an atheromatous plaque lead to clot development?
What are two potential adverse outcomes for these clots?
Exposed thrombogenic factors in the underlying ECM;
thrombosis, embolus development
What is a ‘true’ aneurysm of the cardiovascular system?
What is a ‘false’ aneurysm?
One that involves all three layers of the vessel wall;
rupture of the intima –> hematoma between the media and externa (adventitia)
What type of aneurysm shape is a balloon-like direct outpouching of the vessel wall?
What type of aneurysm is a more football-shaped expansion in all directions?
Saccular,
fusiform
What is the most common location for an atherosclerotic aneurysm?
The abdominal aorta
True/False.
A false aneurysm of the aorta is an aortic dissection.
False.
False aneurysm –> between the media and externa (adventitia)
Dissection –> between the intima and media
Dissections take place between what layers of the vessel wall?
The intima dissecting off the media
What is congestive heart failure in terms of bodily metabolic need?
Cardiac output is insufficient to match bodily metabolic requirements
Are most cases of congestive heart failure due to systolic or diastolic function?
Systolic
(inadequate contractile function)
What are the most common causes of left-sided heart failure?
Ischemic heart disease;
hypertension;
aortic/mitral valve diseases;
1° myocardial diseases
What is the most common causes of right-sided heart failure?
Left-sided heart failure
What immediate effect(s) does left-sided heart failure have on associated organs?
Pulmonary congestion/edema;
poor perfusion of systemic organs
What pulmonary immune histology is expected in cases of left-sided heart failure?
Wet, congested lung tissue with hemosiderin-laden macrophages
Hemosiderin-laden macrophages are a sign of:
Left-sided heart failure
What is cor pulmonale?
Isolated right-sided heart failure
(i.e. not caused by left-sided HF)
Cor pulmonale typically occurs in patients with:
Chronic disorders affecting the lungs
(e.g. COPD, pulmonary fibrosis, sleep apnea, PE, poliomyelitis, myasthenia gravis, etc.)
What are some major signs or symptoms of left-sided heart failure?
Pulmonary congestion –> cough with frothy sputum, orthopnea, paroxysmal nocturnal dyspnea, shortness of breath;
cyanosis
What are some major signs or symptoms of right-sided heart failure?
Hepatosplenomegaly, JVD, dependent edema;
anorexia, GI distress, weight loss
Cardiac ventricular hypertrophy can result from anything that causes what?
Increases in afterload
What are the changes in color seen in myocardium as a result of ischemia?
(Start with normal myocardium and end with a scar)
No change –>
dark mottling –>
hyperemia –>
yellow-brown softening –>
gray-white scar
During what time period following infarction will myocardial histology show no color changes?
1 - 4 hours
During what time period following infarction will myocardial histology show dark mottling?
4 - 24 hours
During what time period following infarction will myocardial histology show a yellow-brown softening with a hyperemic border?
3 - 10 days
During what time period following infarction will myocardial histology show gray-white scar formation?
2 - 8 weeks
(scar complete after ~2 months)
What proportion of patients with a STEMI typically die within the first hour before receiving medical care?
Of what?
1/3;
fatal arrythmias
What is the in-hospital MI death rate?
7%
Cardiac rupture is a complication of 1 - 5% of MIs.
In what time frame is it most likely to occur?
3 - 7 days following the infarction
What percentage of PEs arise from DVTs?
> 95%
How do peri-mortem clots appear? Are they attached to the underlying wall?
How do post-mortem clots appear? Are they attached to the underlying wall?
Grayish-red; yes.
Gelatinous, yellow, ‘chicken fat’ clots; no
Via activation of what proteins do macrophages know that bacterium are present for phagocytosing?
Toll-like receptors
(common invader patterns)
How long do neutrophils typically live?
Do they have APC abilities?
5 days;
no
What type of substance do natural killer cells phagocytose?
Nothing; they are not phagocytes
Via what two mechanisms do natural killer cells exert any effect?
- Release of cytokines
- Inducing suicide in tumor cells, virus-infected cells, etc.
Memory cell activation by an antigen leads to a rapid increase in plasma cells specific to that antigen via what process?
Clonal selection
Via what two methods do immunoglobins exert an effect on pathogens?
Opsonization;
neutralization
Macrophages have receptors for what part of the immunoglobin?
The Fc region
T cell MHCs are useful for identifying what two types of problem?
Problems within the cell (MHC I);
APCs presenting problems outside the cell (MHC II)
What type of connective tissue fiber is found in high concentrations in lymphoid tissues?
What cells produce this tissue?
Type III collagen (reticulin);
reticular cells
What type of cell provides the support framework of the thymus?
Thymic epithelial cells
(epithelioreticular cells)
What are the primary lymphoid organs?
Bone marrow;
thymus
True/False.
Secondary lymphoid tissues can be found in each of the following:
nasopharynx
oropharynx
bronchus
lung tissue
small intestine
urogenital tissues
True.
Are reticular fibers found in the thymus?
No
True/False.
The thymus is histologically homogenous all the way through, but it is divided by septa into various lobules.
False.
The thymus has a cortex and a medulla that are histologically distinct.
Based on structure and location, how many types of epithelioreticular (thymic epithelial cells) are there throughout the thymus?
6
True/False.
Many macrophages can be found in the thymus.
True
What types of T cell selection occur in the thymic cortex and medulla, respectively?
Positive selection,
negative selection
What is the purpose of thymic positive T cell selection?
Where does it occur?
To select for T cells with the correct surface proteins (e.g. CD4 or CD8, TCR, CD3, etc.);
the thymic cortex
What is the purpose of thymic negative T cell selection?
Where does it occur?
To ensure certain T cells don’t have the incorrect surface proteins (e.g. just CD4 or just CD8);
the thymic medulla
Positive and negative T cell selection in the thymus is all contained and controlled by what type of cell?
How many types of this cell are there (based on location and structure)?
Thymic epithelial cells
(epithelioreticular cells);
6
What are the six types of epithelioreticular (thymic epithelial) cell found in the thymus?
Type I - outer boundary of cortex
Type II - positive selection
Type III - inner boundary of cortex
Type IV - outer boundary of medulla
Type V - negative selection
Type VI - Hassall’s corpuscle (express thymic stromal lymphopoietin - TSLP)
What two types of epithelioreticular (thymic epithelial) cell are the boundaries of the thymic cortex?
I and III
What two types of epithelioreticular (thymic epithelial) cell are responsible for positive and negative T cell selection, respectively?
Types II and V
What type of epithelioreticular (thymic epithelial) cell makes up Hassall’s corpuscles in the thymic medulla?
What do they secrete?
Type VI;
thymic stromal lymphopoeitin (TSLP)
Which is more basophilic, the thymic cortex or medulla?
Cortex
What specialized structure lines thymic capillaries?
What type of capillaries are these?
The blood-thymus barrier;
continuous
Between the endothelial cells / pericytes of thymic capillaries and the epithelioreticular (thymic epithelial) cells of the thymic medulla, what type of cell is found in the connective tissue space?
Macrophages
How many basal lamina are found surrounding thymic capillaries?
Two
(see image)
Where are most B cells found in a lymph node?
Where are most T cells found in a lymph node?
Where are most plasma cells found in a lymph node?
Cortex (follicles, nodules)
Paracortex (deep cortex)
Medulla (medullary cords)
Name the predominant type of cell in the following locations:
Cortex (follicles, nodules)
Paracortex (deep cortex)
Medulla (medullary cords)
Cortex (follicles, nodules) - B lymphocytes
Paracortex (deep cortex) - T lymphocytes
Medulla (medullary cords) - Plasma cells
What type of cell is the predominant type found in a lymph node cortex (follicles)?
B lymphocytes
What type of cell is the predominant type found in a lymph node paracortex (deep cortex)?
T lymphocytes
What type of cell is the predominant type found in a lymph node medulla (medullary cords)?
Plasma cells
What type of cell and fiber makes up much of the lymph node stroma?
Reticular cells / reticular fibers (type III collagen)
True/False.
Lymph nodes are non-encapsulated lymphatic tissue.
False.
The lymph node paracortex has a large concentration of what vessel type?
High endothelial venules
What is in the center of a lymphatic follicle (with all the B cells)?
A germinal center
Afferent lymphatic vessels pierce lymph node capsules and drain into what space?
The subcapsular space
Describe the flow of lymph through a lymph node.
(Note: from afferent lymphatic vessel to efferent lymphatic vessel.)
Afferent lymphatic vessel –>
Subcapsular space –>
Paratrabecular sinuses –>
Through cortex –>
Through medulla –>
Efferent lymphatic vessel
Where does blood flow enter the lymph node?
Where does it exit?
The hilum;
the hilum
Describe the route taken by the fluid that enters the lymph node as blood but leaves as lymph.
(Note: obviously, this is not all the blood. Most of it leaves through lymph node venules.)
Enters through arteries –>
Leaves circulation through high endothelial venules (perfuses paracortex) –>
Enters lymphatic sinusoids –>
Exits lymph node through efferent vessels –>
Returns to circulation through thoracic duct or right lymphatic duct
What type of structure is shown in this micrograph?
A lymph node
Most (90% of) lymphocytes enter lymph nodes via what?
High endothelial venules
(in the paracortex)
A lymph node germinal center is a ________ follicle.
Secondary
What two types of pulp are found in the spleen?
Red and white
What structure is shown in this micrograph?
The spleen
From deep to superficial, name the three portions of a splenic white pulp island.
Central artery, (+ sheath)
germinal center,
marginal area
What structure accompanies arteries in the splenic white pulp?
This structure is mostly comprised of what type of cell?
A periarterial lymphatic sheath (PALS);
T cells
The splenic white pulp is mostly what type of cell?
The splenic PALS is mostly what type of cell?
B cells;
T cells
The splenic white pulp has what functions?
Blood antigen removal
Antigen presentation
Antibody production
Lymphocyte proliferation (T and B cells)
The splenic red pulp has what functions?
Remove the following from circulation:
- Blood antigens
- RBC’s & platelets (aged, abnormal, and/or damaged)
- Iron (macrophage phagocytosis & digestion)
The splenic red pulp is mostly centered around ________ the blood.
The splenic white pulp is mostly centered around mounting an ________ ________ to what is found in the blood.
Cleaning/filtering;
immune response
The splenic cords and sinusoids are found in which type of splenic pulp?
Red pulp
Non-encapsulated secondary lymphatic tissues (e.g. tonsils, Peyer’s patches) are mostly just aggregates of:
Lymphatic nodules
Although splenic tissue does not stain red and white upon histology preparations, what is a defining feature that indicates which is white pulp?
Presence of a central artery
Afferent lymphatic vessels
Lymphatic germinal center
Lymphatic vessels
Lymph node; filters blood and produces antibodies
Lymphatic nodule with germinal center
PALS (T cells);
central arteriole
(splenic white pulp)
Arrows - white pulp
A - red pulp
B - hilum
Peyer’s patches
A - smooth muscle
B - dense irregular connective tissue
A - central arteriole
B - pulp arteriole
Arrows - venous sinusoids
A - pulp cords
(splenic tissue)
What organ is shown in this micrograph?
The spleen
A splenic nodule
Paracortex;
high endothelial venules
Lymph node micrograph
A - medullary cords
Arrow - macrophage
Black arrows - subcapsular sinus
Green arrows - cortical sinuses
A - Cortex
B - Paracortex
C - Medulla
Lymph node micrograph
High endothelial venule
Lymph node hilum
Black arrows - subcapsular lymph node sinus
White arrows - cortical lymph node sinus
What organ is shown in this micrograph?
The thymus
Tonsil
Arrow –> tonsilar crypt
Identify the three types of vessel.
A - lymphatic vessel
B - venule
C - arteriole
Identify A - E in this micrograph of vessels.
A - venule
B,C,E - arterioles
D - lymphatic vessel
What is unique about the tunica adventitia (externa) of the largest veins?
Smooth muscle is present
Are neutrophils APCs?
No
What molecule presents antigens to TH cells?
What is the effect?
MCH II (from APCs);
TH cell activation (and subsequent B cell proliferation)
What molecule presents antigens to TC cells?
What is the effect?
MHC I (from virally infected cells);
TC cell activation and infected cell lysis
What cytokine is especially important in activating TH cells and TC cells?
Interleukin-2
(IL-2)
MHC I signaling alerts TC cells to problems in which location?
MHC II signaling alerts TC cells to problems in which location?
Intracellular problems (e.g. viruses);
extracellular problems (phagocytosed and then presented)
What surface receptor is found on both TC and TH cells?
What surface receptor is found on only TC cells?
What surface receptor is found on only TH cells?
TCR (T cell receptor)
CD8+
CD4+
Positive selection in the thymic cortex does what to T cells?
Negative selection in the thymic cortex does what to T cells?
Both CD4+ and CD8+ are added to the T cell
(results in cells positive for TCR, CD4+, and CD8+);
one of the CD receptors is removed
(results in cells positive for TCR and either CD4+ or CD8+)
Where in the thymus are T cells double negative? What does this mean?
Where in the thymus are T cells double positive? What does this mean?
What happens next?
The cortex –> the cells lack CD4+ and CD8+;
the cortex –> the cells have both CD4+ and CD8+;
in the medulla, the cells lose one of the above (either CD4+ or CD8+ is lost)
Via what vessel do most lymphocytes enter lymph nodes?
Via high endothelial venules (HEVs)
What type of epithelium lines high endothelial venules (HEVs)?
Simple cuboidal cells
A micrograph shows packed lymphocytes with interspersed plasma cells. This is likely a slide of what tissue?
A lymph node medulla
A micrograph shows packed lymphocytes with interspersed epithelioreticular cells and a few Hassall’s corpuscles. This is likely a slide of what tissue?
The thymic medulla
A micrograph shows packed lymphocytes with interspersed epithelioreticular cells and no Hassall’s corpuscles. This is likely a slide of what tissue?
The thymic cortex
Does the spleen have efferent lymph vessels or afferent lymph vessels or both?
Do lymph nodes have efferent lymph vessels or afferent lymph vessels or both?
Does the thymus have efferent lymph vessels or afferent lymph vessels or both?
Efferent only;
both;
efferent only
How does the spleen pull out old RBCs for recycling?
Young RBCs can deform and pass through the sinusoids;
older RBCs cannot, and continue through the vessel system until they are picked up by splenic macrophages
True/False.
Large arterioles typically have an internal elastic lamina.
True.
The tunica media of an arteriole usually contains __ or __ layers of smooth muscle.
1, 2
The tunica adventitia is ______ in arterioles.
Scant
The endothelial cells in postcapillary venules are supported by what type of cell and what type of fiber?
Pericytes, reticular fibers
Large venules will often contain __ or __ poorly organized and somewhat incomplete layers of smooth muscle.
1, 2
