Heart Tissue Flashcards
What are the contents of the cardiovascular system?
Heart
Blood vascular system
Lymph vascular system
What is the function of the cardiovascular system?
Maintains and regulates the continuous movement of all body fluids
Heart pumps blood toward capillary beds
Vessels (conduits for blood or lymph)
What is the flow of deoxygenated blood?
Tissues - microcirculation - venous vessels - heart - arterial vessels - lungs
What is the flow of oxygenated blood?
Lungs - venous vessels - heart - arterial vessels - microcirculation - tissues - lymph vessels - lymph nodes
What is the lymph vascular system?
Carries fluid (lymph) to lymph nodes for filtration and then returns filtered lymph to blood
What are the parts of the heart?
Heart wall - 3 layers
Cardiac skeleton - valves and ings CT within interventricular and atrioventricular septae
Conducting system - SA node, AV node, Purkinje fibers
Coronary vasculature - arterial supply to the heart and cardiac veins and coronary sinus
What are the 3 parts of the heart wall?
Endocardium
Myocardium
Epicardium
What are the layers of the heart wall from superficial to deep?
Epicardium
Visceral pericardium
Subepicardium
Myocardium
Endocardium
Subendocardium
Myoelastic CT later
Subendothelium
Endothelium
What are the layers of the epicardium?
Visceral Pericardium
Subepicardium
What are the layers of the endocardium?
Subendocardium
Myoelastic CT layer
Subendothelium
Endothelium
Are there layers in the myocardium?
No!
Describe the 2 structures of the epicardium or outer layer of the heart
Visceral pericardium - shiny surface on heart, simple squamous epithelium (1 layer)
Subepicardium - layer of fibroelastic CT (dense irregular CT with collagen I gibers and elastic fibers) just below the visceral pericardium, adipose CT layer in the sulci/grooves and surrounding coronary vessels
What does the visceral pericardium and the subepicardium do?
Visceral pericardium - Secretes lubricating fluid for pericardial cavity (anti-friction)
Subepicardium:
Fibroelastic CT layer connects epithelium to underlying fat and/or to myocardium
Adipose CT layer protects coronary vessels (cushions the vessels and prevents squishing when heart expands) and is local energy storage site for hearts
What is the myocardium?
The middle muscular layer
Most of the heart wall
What are contractile cardiomyocytes? What do they do?
Main cell type in myocardium
Aka contractile cardiac muscle fibers
Y-shaped cells (branches)
1-2 euchromatic nuclei in cell center
The heart pumps by coordinating these cells’ contraction and relaxation
What are intercalated discs?
Present in contractile cardiomyocytes
Concentrated gap junctions that aid in rapid ion transfer and allows depolarizing current (produced by cations) to flow from cell to cell very rapidly
What is the other cell in the myocardium and what does it do?
Myoendocrine cells
Modified contractile cardiomyocytes that also secrete peptide hormones
In the atria - myoendocrine cells secrete atrial natriuretic peptide (ANP)
In the ventricles - myoendocrine cells secrete B-type natriuretic peptide (brain natriuretic peptide, BNP)
What are Purkinje fibers?
Modified contractile cardiomyocytes in myocardium that are highly specialized for rapid impulse conduction
Fibers mostly travel in the subendocardium layer of the endocardium, but they terminate in the myocardium
What is the endocardium?
The inner layer of the heart
Lines chambers
Has 4 sublayers - subendocardium, myoelastic CT layer, subendothelium, and endothelium
What is the structure and function of the subendocardium of the endocardium?
Layer next to myocardium
Loose CT with blood vessels, nerves, and Purkinje fibers
CT anchors endocardium to myocardium and provides a pathway for Purkinje fibers
What is the structure and function of the myoelastic CT layer of endocardium?
Smooth muscle cells, elastic fibers, and some collagen I
Facilitates contraction/expansion of endothelium
What is the structure and function of the subendothelial layer?
Collagenous or fibroelastic CT (lots of collagen I fibers and some elastic fibers)
Anchors endothelium to rest of endocardium
What is the structure and function of the endothelium?
Layer closest to chamber lumen
Simple squamous epithelium
Lines heart chambers
What is the conduction pathway of the heart?
SA node - conducting cells along atrial walls - AV node - along fibrous skeleton - AV Bundle (of His) - R and L bundle branches - Purkinje fibers
What is the SA node?
The pacemaker
Rate of depolarization is faster than AV node
Most SA nodal cells (pacemaker cells) generate impulses, some transmit impulses to nearby conducting cells in R atrium
Small, elongate cells w/ 2 or more cytoplasmic extensions and fewer myofibrils vs. contractile cardiomyocytes
What is the AV node?
Delays transmission of signals from atria to ventricles
Ensures atrial contraction precedes ventricular contraction
AV nodal cells look pretty similar to pacemaker cells
What are Purkinje fibers specialized for?
Highly specialized for rapid impulse transmission
Mainly located in the subendocardium and eventually terminate in myocardium
What are important characteristics about Purkinje fibers?
2x the diameter of normal contractile cells - faster conduction velocity and faster repolarization
3x more gap junctions in their intercalated discs
Lighter staining
What is the function and structure of the cardiac skeleton?
Fibrous - dense irregular collagenous CT
Flexible anchor for cardiac muscle tissue - can withstand pulling from several directions during heart contraction
What is the structure and function of heart valves?
Each valve has several leaflets or cusps
Valves are avascular typically
Valves maintain unidirectional blood flow through the heart (prevent backflow)
Normal function requires valves to be intact, mobile, and pliable
How many layers do valves have?
5 layers
What are the 5 layers of the valves in the order of the direction of blood flow?
Endothelium - inflow surface
Elastic layer - inflow side
Spongiosa - central core
Fibrosa - outflow side
Endothelium - outflow surface
What 3 layers of the valves are composed of fibroelastic CT?
They contain collagen or elastic fbers in various proportions
Fibrosa - dense, mostly collagen I fibers - structural integrity and resists stretching and breaking
Spongiosa - loose, 50/50 mix; compressable core that absorbs some force of blood hitting the valve
Elastic layer - dense, mostly elastic fibers; allows valve to stretch and then snap back (recoil)
