Exam 2 Histology- Heart and circulatory system
What does the circulatory system consist of?
- Heart -Blood vessels -lymphatic system
Pericytes what are they what is their function
- mesenchymal-like stem cells -in wound healing, they may differentiate into fibroblasts or smooth muscle cells
Venules what is their diameter -which tunicas do they have
-12micrometer- 1mm diameter diameter -tunica intima of endothelial cells tunica media of 1-2 layers of smooth muscle cells -tunica adventitia has several layers of collagen fibers
what are the physical characteristics of discontinuous (sinusoidal) capillaries
-Large (30-50 micrometers) -Irregular, tortuous walls -wide gaps between cells -incomplete basal lamina
what courses through lymphatic vessels?
-Plasma proteins -fluid -enzymes -lipids -antibodies -hormones -other macromolecules that leak from blood vessels and bathe tissues and interstitial spaces
describe the tunica media of small to medium sized veins
-Thin -has some reticular and elastic fibers interspersed with smooth muscle cells
what are the characteristics of continuous (somatic) capillaries?
-continuous endothelium and basal lamina -NO fenestrae -Numerous pinocytic vesicles (for transcytosis)
Tunica Intima of elastic arteries -What is it composed of -what does it include?
-endothelium + underlying sub-endothelial CT -includes internal elastic lamina in larger vessels
Septum Membranaceum (membranous septum) -what is it -what is it an attachment for
-fibrous portion of the interventricular septum -attachment sites of cardiomyocytes
Annuli Fibrosi (annulus fibrosus) -what is it? -what does it support?
-fibrous rings around the origins of the pulmonary artery, aorta, and atrioventricular canals support heart valves
Trigona Fibrosa (fibrous trigone) -what is it? -what does it support?
-fibrous tissue supports AV openings, and the base of the aorta
What does the subendothelial layer of the endocardium contain? What is below this?
-fine collagenous fibers -thin layer of dense fibroelastic CT
Parasympathetic nerves -where are they found -what is their function
-from Vagus to sinoatrial node -slow the heart
Sinoatrial Node (SA node) --function -made of -spread of impulse
-heart pacemaker -made of modified cardiac muscle cells concentrically arranged around a nodal artery -impulse spreads from this node via conduction fibers to the AV node
Atrioventricular Node (AV node) - location -cell composition -what does it form
-located beneath the septal wall endocardium of the right atrium -cells similar to those in SA node (modified cardiac muscle cells) -this node continues to form a common stem--> AV bundle of His
Underneath the mesothelium of the epicardium, it a subepicardial layer. What does this layer contain?
-loose CT -adipose tissue -coronary blood vessels and nerves
Subendothelial layer of an elastic artery -Type of CT -what does the CT contain
-made of loose CT -Contains collagen, elastic fibers, and fibroblasts.
describe the tunica media of a muscular artery
-media of up to 40 circular layers of smooth muscle interspersed with elastic fibers
Purkinje fibers -what are they -what do they contain -where do they travel? -what do they make contact with?
-modified muscle cells (cardiac conduction fibers) -contain glycogen -travel in the subendocardial layer to the heart apex. -then reverse direction and branch to make contact and form gap junctions with cardiac muscle cells
what do continuous capillaries have in the CNS? What is their contribution?
-occluding junctions that contributes to blood-brain barrier
Tunica Media of elastic arteries -what is it composed of and what does it contain?
-primarily smooth muscle cells -external elastic lamina
Atrial natriuretic peptide -where is it released from -why is it released -what are its primary effects?
-released from modified atrial muscle cells -released in response to high BP -primary effect is to increase sodium and water secretion from the kidney.
describe the adventitia of veins
-well developed -with multiple layers of collagenous fibers, a few smooth muscle cells, and elastic fibers
where are continuous (somatic) capillaries located?
1- Muscle 2- CT 3- CNS 4- Exocrine pancreas 5- Gonads My. Cat. Can't. Eat. Grapes
which are the controlling structures of the heart?
1- SA node 2- AV node 3- AV bundle of His 4- Parasympathetic nerves 5-Sympathetic nerves 6-Atrial cardiac muscle cells
what are the three tunics found in blood vessels?
1- Tunica intima 2- Tunica media 3- Tunica Adventitia
describe the flow of blood starting from the aorta
1- aorta 2- arteries 3- arterioles 4- capillaries 5- post-capillary venules 6- venules 7- veins 8- vena cava 9- right atrium 10-right ventricle 11- pulmonary artery 12- lung capillary bed 13- pulmonary vein 14- left atrium 15- left ventricle 16- aorta
the cardiac skeleton can become fibrocartilage in ________, hyaline cartilage in_______ ,or boney in ______________
1- dogs 2- horse 3- older animals (large ruminants)
What are the three ways in which arteries can be classified?
1- large (elastic) 2- Medium (muscular) 3- Small (arterioles)
What are the physical characteristics of capillaries -layer(s) of endothelial cells -diameter -surrounded by?
1- single layer of endothelial cells 2) 7-10 micrometer diameter 3- surrounded by thin sheath of reticular and collagenous fibers and some pericytes
What are muscular venules composed of?
1-2 layers of smooth muscle and thin tunica adventitia
describe the tunica media of an arteriole
1-3 layers of smooth muscle cells -occasional elastic fibers some references say 5-6 layers of SMC
which are examples of elastic arteries?
1-Aorta 2- Pulmonary 3- Brachiocephalic 4- Common carotid 5- Subclavian 6- Common iliac arteries
Which are the 4 different hormones that the ANP gene makes?
1-long acting natriuretic (sodium) peptide 2-vessel dilator 3-kaliuretic (potassium) peptide 4-ANP (atrial natriuretic peptide
where are fenestrated (visceral) capillaries located?
1. Mucosa of GI tract 2. endocrine glands 3. ciliary body 4. choroid plexus 5. renal glomerular and peritubular capillaries Mary. Eats. Chocolate. Chips. Rapidly
what is the diameter of lymphatic vessels?
10-50 micrometers
describe the tunica adventitia of muscular arteries
Adventitia may be as thick as media, with collagen and elastic fibers
what is diastole?
Arterial hydrostatic pressure between contractions
Which cells are the source of polypeptide hormones?
Atrial cardiac muscle cells and some cells in the interventricular septum (myoendocrine cells)
What are the tunics/layers of the circulatory system -Blood vessels -Heart
Blood vessels 1- tunica intima 2- tunica media 3- tunica adventitia Heart 1- endocardium 2- myocardium 3- epicardium
True/false arterioles always have an internal elastic lamina
False it may or may not be present
true/false the tunica adventitia of an elastic artery has a distinct external elastic lamina
False, it does not.
what is the first functional unit in the embryo?
Heart
Where are discontinuous (sinusoidal) capillaries found?
In the liver and hematopoietic organs (BM and spleen)
do muscular venules have pericytes?
NO
What is the epicardium? Which cells form the epicardium?
Outermost epicardial layer formed by mesothelial cells (simple squamous epithelium)
which protein in diaphragms of capillaries maintains the endothelial barrier integrity and controls permeability?
PV1
What is the function of postcapillary venules?
Receive blood from capillaries
what is the function of an arteriole?
Regulate blood flow to capillary beds via vasoconstriction/vasodilation important for regulation of BP
describe the tunica adventitia of an elastic artery
THIN adventitia -has elastic and collagen fibers -NO distinct external elastic lamina
which are the common sites for congenital defects in newborn animals?
The fusion of endocardial tubes and subsequent formation of the chambers, septa, and valves
Composite Blood vessel
The thickness and characteristics of different layers will change based upon vessel type: elastic or muscular artery, arteriole, vein, or venule
True/false All large blood vessels have tunics
True
true/false postcapillary venules have an incomplete layer of pericytes that becomes more complete as the vessel gets larger
True
True/false endothelial cells regulate the traffic of inflammatory cells
True early in inflammation, macrophages in surrounding CT secrete cytokines (TNF-alpha, IL-1) which induce expression of E-selectin by endothelial cells. -neutrophils bind to selectins and then extravasate by migration through the endothelium
what does the internal elastic lamina of an arteriole consist of?
a network of fibers that may not be visible at the level of LM can be seen with PAS or elastin stain
what is endothelin-1
a vasoconstrictor
what is the function of sympathetic nerves
accelerate the heartbeat innervate atrial and ventricular cardiac muscle cells.
How is the myocardium arranged in the ventricles?
arranged into deep and superficial layers
in an arteriovenous anastomoses, what happens when the shunt is closed?
arterial blood flows into the capillary bed
compare the shape of an arteriole to a vein
arterioles have a more regular round shape relative to venules
in an arteriovenous anastomoses, what happens when the shunt is open
blood bypasses the capillary bed and flows into a vein (i.e. cutaneous subpapillary plexus in skin)
what does nitric oxide do?
causes smooth muscle in the tunica media to relax--> vasodilation
what are endocardial cushions?
cell subset that forms the septa
what course do deep fibers of the myocardium have around the ventricle?
circular course
What do elastic arteries do?
conduct blood to muscular arteries.
what are arteriovenous anastomoses
connections primarily between arterioles and venules they have a specialized tunica media with a sphincter
medial endocardial tubes fuse into a single centrally located tubular, _____________ heart
contractile
what aids blood circulation through veins?
contraction of surrounding muscles
what is the function of muscular arteries?
deliver blood to organs
which type of arteries (muscular or elastic) stretch with ventricular contraction and store energy?
elastic arteries
Development of the heart begins as a pair of medial ______________________ tubes
endocardial
What is an atrioventricular canal
endocardial cushion defect
lymphatic vessels are an _____________________ lined vessel. lymph flows in ___________ direction, which is toward the base of the ____________
endothelial 1 neck
Endocardium -what is it -what is it lined by -what is it continuous with -What are its layers
endothelial surface layer of the heart and underlying connective tissue -lined by endothelium -continuous with blood vessels Consists of endothelium, sub-endothelial layer of thin collagenous fibers, thin layer of dense fibroelastic CT, and subendocardial layer of loose CT with nerves, blood vessels, and purkinje fibers.
what lines the entire circulatory system?
endothelium
true/false the cardiac skeleton always remains collagenous
false can range from loose collagen to bone depending on the age and species
true/false BM has lymphatics
false it does not
true/false fenestrated endothelium in the glomerular capillaries have diaphragms
false they do not
Tunica Adventitia -what is it made of
fibroelastic CT (dense irregular CT with small amounts of elastic fibers.)
what holds the lymphatic vessel open in smaller vessels?
fine anchoring filaments that attach to perivascular collagen
what is a patent foramen ovale?
hole between the right and left atrium
where do lymphatic vessels originate?
in CT as anastomosing capillaries capillaries have NO basal lamina
other than in veins, where can valves be found?
in larger lymphatic vessels
where would vasa vasorum (small vessels) be found in larger vessels?
in the tunica adventitia and outer part of the media
what does prostacyclin do?
inhibits platelet adhesion and clot formation
_____________________ in the intestine are an important route of fat absorption
lacteals
what does the heart differentiate from?
lateral plate mesoderm
describe the tunica adventitia of an arteriole
layer of loose CT with longitudinally arranged collagenous and elastic fibers
what is the diameter of an arteriole?
less than 0.5mm
postcapillary venules are similar to capillaries but have a wider __________
lumen
Apart from vasa vasorum, larger vessels may have ______________ and nerves (__________ ______________) in the adventitia
lymphatics nervi vascularis
subendocardial layer of the endocardium -What is it made of -What is it connected to -What does it contain?
made of loose CT, connected to the myocardium contains blood vessels, nerves, and portions of purkinje fibers
The visceral layer of the serous pericardium is the epicardial ______________
mesothelium
what is the myocardium
middle layer of cardiac muscle tissue
papillary muscles -what are they composed of -what is their function?
muscles composed of cardiomyocytes (contractile) prevent inversion/prolapse of the valve leaflets
apart from protstacyclin, what do endothelial cells secrete?
nitric oxide endothelin-1
do arterioles have an external elastic lamina?
no
does the subendothelial connective tissue of muscular arteries have smooth muscle cells?
no, it lacks them
which vessels are an important site of activity in inflammation?
postcapillary venules (vasoactive compounds- histamine and serotonin- affect fluid extravasation and migration of WBCs)
What is systole?
pressure increase in vessel during contraction
what do endothelial cells produce from arachidonic acid?
prostacyclin
Atrioventricular Bundle of His -formed by?
purkinje fibers (cardiac conduction fibers) that penetrate the skeleton and then branch to form the right and left bundle branches
what do the annuli around atrioventricular orifices result in and what does this control?
results in electrical discontinuity between myocardial cells of atria and ventricles controls communication between them via specialized conduction tissue (A-V bundle)
What is the Fibrous cardiac skeleton?
skeleton composed of: -dense irregular CT -Septum membranaceum -Annuli fibrosi -Trigona fibrosa
the intima of which vessel may have a thin subendothelial connective tissue layer
small to medium size veins (1-9mm diameter)
precapillary sphincter -what has this sphincter -what does it control
some microvascular beds (i.e. mesenteric) -control the amount of blood flowing into a capillary
what course does the superficial layer of the myocardium have around the ventricle?
spiral course
which are examples of large veins
superior and inferior vena cava portal trunk
How do elastic arteries maintain BP between heart contractions?
they recoil
Do muscular arteries have a thin or thick external elastic lamina? Where is it found?
thick, found at the edge of the tunica media
Is the tunica intima of muscular arteries thinner or thicker compared to elastic arteries?
thinner.
which are the 2 atrioventricular valves?
tricuspid and mitral valves
True/False heart layers are homologous to the tunics of blood vessels
true
True/false Elastic fibers of the intima of elastic arteries form an incomplete internal elastic lamina
true
true/false -all parts of the cardiac skeleton start out as irregular collagen and elastin
true
true/false arterioles have a thick wall relative to the lumen
true
true/false arterioles have sparse subendothelial connective tissue
true
true/false fluid is scavenged by the lymphatic system, filtered by lymph nodes, and recycled back into the venous circulation at the base of the neck
true
true/false purkinje fibers are portions of the impulse-conducting system of the heart
true
true/false valves have both dense and loose CT layers surrounded by endothelium
true
true/false venous valves are paired, semilunar folds of the tunica intima covered with endothelium
true
true/false larger vessels have an intima, media, and adventitia, like blood vessels, but these may be difficult to discern at LM level
true
true/false (visceral) capillaries are fenestrated
true -they have attenuated endothelium (very thin) with large 60-80 nm fenestrae fenestrae are closed by thin 4-6 nm diaphragms
describe the tunicas of large veins
tunica intima: similar to small veins tunica media: thin tunica adventitia: thick with collagenous fibers and longitudinal arranged smooth muscle cells
What happens to the fused heart tube?
undergoes bends and forms a heart loop with subsequent formation of the chambers, septa, and valves
which are the semilunar valves?
valves between the ventricles and aorta and pulmonary artery
Which vessels have more vasa vasorum?
veins
what is the function of venous valves?
veins operate under low pressure. -valves prevent backflow
what are the mitral and tricuspid valves connected to?
ventricle papillary muscles by fibrous cords (chordae tendineae)
does the tunica intima of muscular arteries have a well developed or poorly developed internal elastic lamina?
well developed
describe the tunica media of an elastic artery
~500 micrometers or 40-70 concentric elastic sheets