Cardiac and Vascular Histology Flashcards
how can cardiac cells be described?
short, branched, y-shaped; with 1-2 nuclei
what are intercalated discs?
transverse junctions at the ends of cells that allow passage of electrical current
what are purkinje cells?
modified cardiac muscle cells that act as the pacemaker for the heart
what are the hallmarks of cardiac muscle?
it has striations, intercalated discs, and lipofuscin granules
what are lipofuscin granules?
from lysosomal degeneration; a sign of normal aging (wear and tear pigments)
what are the 2 layers of the pericardium?
fibrous pericardium and serous pericardium
what are the different parts of the serous pericardium?
a parietal layer of serous pericardium, a visceral layer of serous pericardium, and a pericardial cavity
what lines the inner surface of the fibrous pericardium?
parietal layer of serous pericardium
what is the space between the parietal and visceral layers of the heart?
the pericardial cavity
what is clinically important about the pericardial cavity?
if we have fluid in this pericardial cavity, it can lead to the heart not being able to fully pump as it normally would, leading to decreased ventricular outflow (this is a cardiac tympanade)
what are the 3 layers of the heart?
epicardium, myocardium, and endocardium
what is the epicardium synonymous with?
the visceral pericardium
what is a hallmark of the epicardium?
loose/areolar CT containing autonomic nerves and variable amounts of fat, lined with mesothelium
what is embedded in the adipose tissue of the epicardium?
branches of the coronary arteries
what is the thickest layer of the heart?
myocardium
what is found within the myocardium?
cardiocytes, nodal cardiocytes, and myoendocrine cardiocytes
what is the myocardium characterized by?
it has striations, intercalated discs, lipofuscin granules
where are intercalated discs found and what is their purpose?
they are found only in cardiac muscles- at sites where cells meet end-to-end- always coincide with Z lines; they bind cells, transmit forces of contraction, and allow the spread of excitation
what are the different regions found within the intercalated disc?
a transverse region and a longitudinal region
what is the transverse region (perpendicular) made up of?
the fascia adherens and the desmosomes
what is the longitudinal region (parallel) made up of?
gap (nexus) junctions
what are the fascia adherens?
actin filaments at the ends of the terminal sarcomeres that insert into the junction; they transmit contractile forces between cells
what is the role of the desmosomes found within the transverse region?
they provide anchorage for the intermediate filaments of the cytoskeleton
what is the role of the gap junctions found within the longitudinal region?
allows excitation to pass between cells
in skeletal muscle you have a triad T-tuble. Is this the same in cardiac muscle?
no- in cardiac muscle you have a dyad t-tubules
what mades up the dyad found in cardiac muscle?
1 T-tubule and 1 SR cisterna
what are the dyad T-tubules?
fingerlike invaginations of sarcolemma found at z-lines
what is the purpose of the dyad T-tubules?
it allows for the uniform contraction of myofibrils within a single cardiocyte
what are the nodal cardiocytes?
the modified cells within a SA/AV node that initiate/relay electrical signals
what is the pathway of the conducting system?
the sa node–> av node–> av bundle–> r/l bundle branches–> purkinje fibers
what are purkinje fibers and what is their role?
they are specialized cardiac muscle cells that conduct electrical impulses that allow coordinated contraction
what do the purkinje fibers lack?
t-tubules (mostly)
what is a key characteristic of purkinje fibers and why is this important?
they have fewer myofibrils, but a significantly larger amounts of glycogen–> allows them to be much more resistant to hypoxia
what are myoendocrine cardiocytes and what do they contain?
they are atrial cells that contain membrane-bound granules; also contain precursor of atrial natriuretic factor (ANF)
what is the role of ANF?
targets the kidneys to decrease Na+ and H2O retention
what is the composition of endocardium?
endothelium+ thin layer of loose CT
in the ventricles, what does the endocardium look like?
it has a subendocardial layer
what is a subendocardial layer?
a thin layer of connective tissue with smooth muscle; it merges with the myocardium and contains branches of purkinje fibers
on the atria, what does the endocardium look like?
the subendocardial layer is lacking; the purkinje fibers are typically closer to the endothelium; it is intermixed with the myocardium
what is the cardiac skeleton and where is it located?
it is a dense irregular connective tissue located in the endocardium
what is the purpose of the cardiac skeleton?
it anchors valves and surrounds AV canals to maintain shape; it works as an electrical insulator between the atria and the ventricles
what is the composition of the heart valves?
a core of fibroelastic connective tissue (lamina fibrosa) covered by endothelium
what are the heart valves continuous with?
the cardiac skeleton
what creates the central portion of the heart valves?
the fibroelastic layer of endocardium condenses to form a valve ring
walls of the arteries and veins are composed of what?
3 layers–> tunics
what is the innermost layer/ tunic of blood vessels?
tunica intima
what is the tunica intima composed of?
endothelium, basal lamina, subendothelial layer
what is the composition of the endothelium of the tunica intima?
single layer of squamous epithelial cells
what is the basal lamina of the tunica intima composed of?
thin extracellular layer composed of collagen, proteoglycans, and glycoproteins
what is the subendothelial layer of the tunica intima composed of?
internal elastic membrane, which is a sheet-like layer of fenestrated elastic material within arteries and arterioles
what is the border between the tunica intima and the tunica media?
the internal elastic membrane
what cells make up the innermost layer of the tunica intima?
the endothelial cells
how are endothelial cells connected?
via cell-cell junctions (number of junctions will alter permeability)
what is a major role of the endothelial cells?
they are metabolically involved in blood coagulation and thrombrosis, and local vasodilation/constriction
what are the storage granules found in the endothelial cells?
weibel-palade bodies (WPBs)
what do the weibel-palade bodies (WPBs) store and release?
von willebrand factor and P-selectin
what is the role of vom willebrand factor?
hemostasis
what is the role of p-selectin?
inflammation
what is the middle layer of the blood vessels?
tunica media
what is the composition of the tunica media?
circumferentially arranged layers of smooth muscle
what is the tunica media thick in?
arteries
what does the tunica media extend from?
the internal elastic membrane to the external elastic membrane
what is the layer of elastin that separates the tunica media and the adventitia?
external elastic membranes
what is the outermost layer of blood vessels?
tunica adventitia (aka the tunica externa)
what is the composition of the tunica adventitia?
it is longitudinally arranged collagenous tissue with few elastic fibers; will merge with the loose connective tissue surrounding the vessels
where is the tunica adventitia relatively thick?
venules/veins
where is the tunica adventitia relatively thin?
arterial system
what are the vessels that the tunica adventitia contain and what is their role?
vasa vasorum; they supply blood to the vascular walls themselves
how do the blood vessels receive innervation?
through the nervi vasorum (vascularis): ANS input that controls the contraction of the vascular smooth muscle
what are the largest vessels of the arterial system?
large (elastic) arteries
what forms concentric sheets/lamellae between the muscle cell layers of the large (elastic) arteries?
elastin
what do the smooth muscles of the large (elastic) arteries synthesize?
collagen, elastin, and ground substance of ECM
what is a key characteristic/difference between the large (elastic) arteries and the medium (muscular) arteries?
there is more smooth muscle and less elastin in the medium (muscular) arteries than in the elastic arteries
what is a hallmark for medium (muscular) arteries?
the prominent internal elastic membrane become apparent
how are the smooth muscle cells arranged in medium (muscular) arteries?
in a spiral fashion
what can be said about the tunica adventitia of the medium (muscular) arteries?
it is relatively thick
how are the small arteries and arterioles distinguished?
by the number of smooth muscle layers in the tunica media
how many layers of smooth muscle can the small arteries have?
up to 8 layers- will also have an internal elastic membrane
how many layers of smooth muscle can the arterioles have?
1-2 layers and the internal elastic membrane may or may not be present
what is the function of the arterioles?
they are the flow regulators for the capillary beds
what do the arterioles respond to?
the ANS
what does the sympathetic innervation to the tunica media cause?
vasoconstriction
what does the parasympathetic innervation to the tunica media cause?
vasodilation
what are the smallest of all the vessels?
capillaries
what do the capillaries form?
capillary beds
what occurs at the capillary beds?
they are the site of metabolic exchange
what are pericytes?
perivascular contractile cells with branching cytoplasmic processes
what are the pericytes controlled by?
nitric oxide (NO)
what is the role of the pericytes?
they promote the stability of capillaries and postcapillary venules
what are the three types of capillaries?
continuous capillary, fenestrated capillary, and discontinuous capillary
what is the metarteriole?
the first branch off the arteriole supplying the tissues
what are the precapillary sphincters?
regulate blood flow through true capillaries
what are true capillaries?
they branch from the metarteriole; they lack smooth muscle; pericytes may be present
what is a thoroughfare channel?
the distal end of the metarteriole (lacks smooth muscle)
what does the thoroughfare channel connect to?
a postcapillary venule
what receives blood from the capillaries?
venules
what are venules subclassified as?
postcapillary and muscular venules
what is the diameter of the venules?
.1 mm
what is the diameter of the small veins?
less than 1mm
what are the small veins continuous with?
muscular venules
what is the diameter of the medium veins?
10 mm
what is the diameter of the large veins and what are 3 examples?
> 10 mm; superior and inferior vena cava, hepatic portal vein
what are the hallmarks for identifying veins?
veins have thinner walls than accompanying arteries; lumen is larger than of the artery; lumen of veins are often collapsed
what are the layers of the postcapillary venules?
they do not have a true tunica media
what are the layers of the muscular venules?
have 1-2 layers of smooth muscle in tunica media with a thin tunica adventitia
what are the layers of the small veins?
they will have all three tunics; tunica media is 2-3 layers; have a thicker tunica adventitia
how can you identify a medium vein?
the tunica adventitia is significantly thicker than the tunica media
what is the common site for a LE DVT?
medium veins
what are the closed-ended tubes found among the capillary beds (in the lymphatic system)?
lymphatic capillaries
what do the lymphatic capillaries go on to form?
collecting lymphatic vessels
what is the composition of lymphatic vessels?
they have all the vascular tunics and possess valves
where does the thoracic duct drain into?
the left subclavian and internal jugular vein
where does the right lymphatic duct drain into?
right subclavian and internal jugular vein
