Heart and Vascular Histology Flashcards
______ muscle cells are single, very long cylindrical, multinucleate cells with obvious striations
Skeletal
______ muscle cells are single, fusiform, uninucleate with nucleus centrally located, and without striations
Smooth
______ muscle cells are branching chains of cells that may be uni- or binucleate and they do have striations
Cardiac
Which of the following describes skeletal muscle cells?
A. Striated and voluntary
B. Striated and involuntary
C. Non-striated and voluntary
D. Non-striated and involuntary
A. Striated and voluntary
Which of the following describes cardiac muscle cells?
A. Striated and voluntary
B. Striated and involuntary
C. Non-striated and voluntary
D. Non-striated and involuntary
B. Striated and involuntary
Which of the following describes smooth muscle cells?
A. Striated and voluntary
B. Striated and involuntary
C. Non-striated and voluntary
D. Non-striated and involuntary
D. Non-striated and involuntary
Describe the type of contractions exhibited by smooth muscle
Produces continuous contractions of low force
Rhythmic contraction that is inherent, but responsive to ANS
Skeletal and smooth muscle both have actin and myosin involved in their contraction, but what makes smooth muscle different?
They are not arranged in sarcomeres, so they lack longitudinal arrangement of contractile proteins. Instead, actin and myosin bundles criss-cross the cell and are anchored at focal densities
Tension produced is transmitted through the densities to the membrane; cells contract as one unit and assume a globular shape.
The signaling mechanism also differs
_____ Muscle cells are short, branched, and y-shaped. They are associated with extensive capillaries.
Cardiac
Cardiac muscle cells are associated with _______ ______ which are transverse junctions at the ends of cells that allow passage of electrical current
Intercalated discs
_______ cells are modified cardiac muscle cells that act as the pacemaker for the heart
Purkinje
What are the 2 layers of the pericardium?
Fibrous pericardium
Serous pericardium
The _______ pericardium is the outer covering of dense connective tissue
Fibrous
The serous pericardium consists of the following:
_______ layer = lines the inner surface of the fibrous pericardium
_______ layer = covers the outer surface of the heart
_______ ______ = space between the above 2 layers
Parietal
Visceral (epicardium)
Pericardial cavity
Which of the following is referred to as the epicardium?
A. Fibrous pericardium
B. Parietal layer of serous pericardium
C. Visceral layer of serous pericardium
D. Pericardial cavity
C. Visceral layer of serous pericardium
What are the 2 major layers of the heart wall?
Epicardium = outermost layer
Myocardium = thickest layer of the heart
Endocardium = inner layer
Describe the histological composition of the epicardium
Dense fibrocollagenous CT with elastic fibers, lined with mesothelium
Branches of coronary arteries are embedded in adipose tissue
The myocardium is the thickest layer of the herat. What are the 3 major cell types associated with the myocardium?
Cardiomyocytes (contractile)
Nodal cardiomyocytes (SA and AV nodes)
Myoendocrine cardiomyocytes (contain atrial granules)
Which layer of heart tissue is lined with mesothelium? What is mesothelium?
Epicardium; mesothelium is simple squamous epithelium that is associated with a serous membrane
Myocardium is characterized by:
________ due to sarcomere arrangement
________ discs
_______ t-tubule system
Mitochondria
_______ and _______ granules
Striations
Intercalated
Diad
Lipofuscin; atrial
Compare/contrast the t-tubule systems in cardiac vs. skeletal muscle
Cardiac = diad t-tubule system
Skeletal = triad t-tubule system
Intercalated discs are specialized interdigitating junctions between cardiomyocytes found at sites where cells meet end-to-end. They always coincide with _______
Z lines
What is the function of intercalated discs?
Bind cells, transmit forces of contraction, and allow the spread of excitation
Intercalated discs have varying membrane-membrane contacts based on 2 regions: transverse (perpendicular) and longitudinal (parallel).
What are the 3 types of membrane-to-membrane contacts exhibited by intercalated discs? Which region are these associated with?
2 in transverse region:
Fascia adherens
Desmosomes
1 in longitudinal region:
Gap (nexus) junctions
Intercalated discs have 3 types of membrane-membrane contacts. 2 in transverse region: fascia adherens and desmosomes; and 1 in longitudinal region: gap (nexus) junctions.
Which type of membrane-membrane contact transmits contractile forces between cells and is the most predominate?
Fascia adherens
Intercalated discs have 3 types of membrane-membrane contacts. 2 in transverse region: fascia adherens and desmosomes; and 1 in longitudinal region: gap (nexus) junctions.
Which type is found at sites of low electrical resistance and allows excitation to pass between cells?
Gap (nexus) junctions
Intercalated discs have 3 types of membrane-membrane contacts. 2 in transverse region: fascia adherens and desmosomes; and 1 in longitudinal region: gap (nexus) junctions.
Which type contains actin filaments at the ends of terminal sarcomeres which insert into junction?
Fascia adherens
Intercalated discs have 3 types of membrane-membrane contacts. 2 in transverse region: fascia adherens and desmosomes; and 1 in longitudinal region: gap (nexus) junctions.
Which type provides the anchorage for the intermediate filaments of the cytoskeleton?
Desmosomes
Describe the components of a diad T-tubule system associated with cardiac muscle cells
Diad = 1 T-tubule + 1 SR cisterna
Diad t-tubules are fingerlike invaginations of the ________ and are found at the ___-lines.
They permit uniform contraction of _____ within a single cardiomyocyte
Sarcolemma; Z
Myofibrils
______ granules are small bodies that accumulate ith age in stable non-dividing cells like cardiomyocytes
Lipofuscin
Lipofuscin granules are small bodies that accumulate ith age in stable non-dividing cells like cardiomyocytes. They contain material derived from what?
Residual bodies after lysosomal digestion
What important biological molecule is contained within atrial granules?
Atrial natriuretic factor - which targets the kidneys to decrease Na+ and H2O retention, thus increasing urine output
Important because it gives your heart some endocrine function!
About 600 atrial granules are contained within each ________ cell, although smaller quantities are found in the _____ atrium and ventricles
Myoendocrine; left
The endocardium is made up of what 2 major components?
Endothelium
Thin layer of loose CT
What type of endothelium is found in the endocardium?
Simple squamous
The thickness of the endocardium differs in ventricles vs. atria. The ventricular endocardium has a ________ layer composed of a thin layer of CT with smooth muscle as well as purkinje fibers
Subendocardial
In the _____ of the heart, Purkinje fibers are often closer to the endothelium and intermixed with the myocardium
Atria
List direction of heart conduction from the SA node (pacemaker) to the purkinje fibers
SA node –> AV node –> AV bundle –> R/L bundle branches –> purkinje fibers
_______ cardiomyocytes are modified cardiomyocytes within the SA/AV nodes that initiate/relay electrical signals
Nodal
_________ _________, also known as right and left bundle branches, transmit signals to ventricular cardiomyocytes (purkinje fibers)
Subendocardial branches
The cardiac skeleton is made up of ____ ____ CT located in the __________.
It extends into the valve cusps and _____ ______, acting as the insertion of cardiac muscle as well as the electrical insulator between atria and ventricles.
Dense irregular; endocardium
Chordae tendinae
What is the function of the cardiac skeleton?
Anchors valves and surrounds AV canals to maintain shape
Contributes to interventricular and interatrial septa
Electrical insulator between atria and ventricles
Insertion of cardiac muscle
Heart valves have a core of _______ CT, aka lamina fibrosa, and are covered by _________.
Fibroelastic; endothelium
Heart valves are continuous with the _____ ______. Their fibroelastic CT (lamina fibrosa) layer condenses to form a _____ ____, which creates the central portion of the valve.
Cardiac skeleton
Valve ring
Structurally, arteries and veins are made up of what 3 histological layers?
Tunica externa/adventitia
Tunica media
Tunica interna
What are the structural components of the tunica externa/adventitia?
Fibroblasts Elastin Collagen Vaso vasorum Nerves
The tunica externa/adventitia is associated with vaso vasorum, particularly when it comes to large arteries like the aorta. What is the vaso vasorum?
It means “vessels of vessels”, referring to blood supply to these large muscular vessels
What is the overall function of the tunica externa/adventitia?
Anchors blood vessels to an organ
What are the structural components of the tunica media?
Smooth muscle
Elastic and reticular fibers
Sensory fibers
External elastic lamina (arteries)
What are the structural components of the tunica intima?
Endothelium Subendothelium (loose CT) Basal lamina (type IV collagen) Internal elastic lamina
What is unique about the tunica intima in veins?
Tunica intima contains valves in veins
What type of artery is considered the largest, and contains elastic fibers in all 3 tunics?
Elastic arteries
Elastic arteries have elastic fibers in all 3 tunics which allow for stretching due to the increased pressure generated by blood flow from the heart. What are some examples of elastic arteries?
Aorta Brachiocephalic trunk Common carotid a. Subclavian a. Pulmonary arterial vessels
What type of arteries do elastic arteries branch into?
Muscular arteries
Muscular arteries possess elastic fibers in the internal and external _______ ________.
They have a proportionally thicker tunica _______.
Elastic laminae
Media
T/F: most ‘named’ arteries are elastic arteries
False - most named arteries are considered muscular arteries
What do muscular arteries branch into?
Arterioles
Arterioles are the smallest arteries with less than 6 layers of smooth muscle. What histological layer is lost in arterioles?
Internal elastic lamina
What do arterioles feed into?
Capillaries
Sympathetic innervation to tunica media causes ________
Parasympathetic innervation to the tunica media causes ________
Vasoconstriction (increase in BP)
Vasodilation (decrease in BP)
Capillaries are the smalles of all blood vessels that form capillary beds. Their diameter is only slight larger than an erythrocyte, and their wall is thin enough for gas exchange. Which tunics are present in capillaries?
Capillaries only have tunica intima - single layer of endothelium!
_______ are perivascular contractile cells associated with regulating blood flow into the capillary beds
Pericytes
Trace the blood flow into a capillary bed from the arterial end to the venous end
Arteriole –> metarteriole –> true capillaries –> thoroughfare channel –> postcapillary venule
______ capillaries are branches from the metarteriole with rings of smooth muscle in their walls
True
Metarterioles and ______ ______ regulate blood flow through the true capillaries
Precapillary sphincters
_________ ________ = distal end of metarteriole that lacks smooth muscle, leads into postcapillary venule
Thoroughfare channel
What is the smallest type of vein found in the body?
Postcapillary venule
Contracted precapillary sphincters will “shunt” bloodflow, preventing exchange within true capillaries. What effect does this have on venous return?
It forces blood to enter venous return more quickly
[Shunting of blood flow will differentially occur based on metabolic demand]
_________ cells are flat, polygonal cells that form the innermost aspect of the tunica intima, which acts as a permeability barrier via cell-cell junctions
Endothelial
Endothelial cells forming the innermost aspect of the tunica intima support the ________ _______ and produce _________.
Basement membrane; collagen
Endothelial cells that form the innermost aspect of the tunica intima are metabolically involved in what processes?
Blood coagulation and thrombosis
Local vasodilation/constriction
What are the 3 types of capillaries in order of least leaky to most leaky?
Continuous capillaries (cells meet end-to-end)
Fenestrated capillaries (fenestra = window)
Sinusoid capillaries (discontinuous)
What is the most common type of capillary?
Continuous
Continuous capillaries have tight, occluding junctions sealing off intercellular clefts. Thus, all molecular exchange must occur via _____ or _______
Diffusion; transcytosis
Compare/contrast the basement membrane associated with the 3 types of capillaries: continuous, fenestrated, and sinusoid
Continuous = continuous basement membrane
Fenestrated = continuous basement membrane
Sinusoidal = partial discontinuous basement membrane
Where might you find continuous capillaries?
Most common, found throughout the body in muscle, brain, peripheral nerves, exocrine glands, etc.
Where might you find fenestrated capillaries?
Organs where molecular exchange with the blood is important - like kidneys, endocrine organs, intestinal walls, choroid plexus
Describe molecular exchange within fenestrated capillaries
Fenestrated capillaries have tight junctions with fenestrations among endothelial cells
This allows greater exchange across the endothelium, but limited to the size of the macromolecule
Where might you find sinusoidal capillaries?
Where exchange of macromolecules and cells (between tissue and blood) must openly occur - like bone marrow, liver, and spleen
Describe molecular exchange within sinusoidal capillaries
Large fenestrations among endothelial cells (larger than in fenestrated capillaries)
This allows open exchange to occur, large cell movements are allowed
_________ are vessels tht drain capillaries and return blood to the heart
Venules
T/F: pressure in veins is much lower than in arteries and at rest, the body’s veins hold about 60% of the body’s blood
True; veins function as blood reservoirs!
Veins usually travel as companions to arteries. They are classified as small, medium, or large based on size/development of ________.
They contain _____ which are thin folds of intima projecting into the lumen, preventing the backflow of blood
Tunics
Valves
______ veins travel with muscular arteries; both the media and externa/adventitia are better developed, but the wall is often folded around large lumen
Medium
T/F: medium veins contain valves
True
Large veins have a muscular media layer, although it is thin compared to the surrounding adventitia. Walls are often folded with the ______ projecting into the lumen as a valve.
Large veins travel with ______ arteries
Intima
Elastic
Lymph is a clear, yellowish fluid comprised of interstitial fluid, solutes, and foreign material.
It is produced due to pressure differences across ______ ______
True capillaries
Lymphatic vessels collect lymph and return it to the _____ supply
Venous
Lymphatic capillaries are _______-ended tubes found among capillary beds. They are composed of overlapping _______cells that form 1-way valves for collecting lymph; these cells are typically ______ than those of blood capillaries
Closed
Endothelial
Larger
Openings between endothelial cells of lymphatic capillaries are held in place by _______ filaments which contain _______ and are covered by extensions of endothelial cells. They lack a complete _______ lamina
Anchoring; elastin; basal
What vascular tunics are found in lymphatic vessels?
All 3 in addition to valves
The walls of lymphatic vessels remain extremely _____
Normally they do not contain RBCs
_______ lymph vessels carry lymph toward lymph nodes
_______ lymph vessels carry “clean” lymph away from lymph nodes, which is able to stay clean due to one-way flow thanks to ______
Thin
Afferent
Efferent; valves
Trace lymph flow from lymphatic capillaries to its final venous destination
Lymphatic capillaries
Lymphatic vessels
Lymphatic trunks
Right lymphatic duct (lymph from R side of head, neck, upper limb, and thorax)
Thoracic duct (from most of the body)
Drain into brachiocephalic veins
