Heart Tissue

Question 1

What are the contents of the cardiovascular system?

Answer 1

Heart

Blood vascular system

Lymph vascular system

Question 2

What is the function of the cardiovascular system?

Answer 2

Maintains and regulates the continuous movement of all body fluids

Heart pumps blood toward capillary beds

Vessels (conduits for blood or lymph)

Question 3

What is the flow of deoxygenated blood?

Answer 3

Tissues - microcirculation - venous vessels - heart - arterial vessels - lungs

Question 4

What is the flow of oxygenated blood?

Answer 4

Lungs - venous vessels - heart - arterial vessels - microcirculation - tissues - lymph vessels - lymph nodes

Question 5

What is the lymph vascular system?

Answer 5

Carries fluid (lymph) to lymph nodes for filtration and then returns filtered lymph to blood

Question 6

What are the parts of the heart?

Answer 6

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

Question 7

What are the 3 parts of the heart wall?

Answer 7

Endocardium

Myocardium

Epicardium

Question 8

What are the layers of the heart wall from superficial to deep?

Answer 8

Epicardium

Visceral pericardium

Subepicardium

Myocardium

Endocardium

Subendocardium

Myoelastic CT later

Subendothelium

Endothelium

Question 9

What are the layers of the epicardium?

Answer 9

Visceral Pericardium

Subepicardium

Question 10

What are the layers of the endocardium?

Answer 10

Subendocardium

Myoelastic CT layer

Subendothelium

Endothelium

Question 11

Are there layers in the myocardium?

Answer 11

No!

Question 12

Describe the 2 structures of the epicardium or outer layer of the heart

Answer 12

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

Question 13

What does the visceral pericardium and the subepicardium do?

Answer 13

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

Question 14

What is the myocardium?

Answer 14

The middle muscular layer

Most of the heart wall

Question 15

What are contractile cardiomyocytes? What do they do?

Answer 15

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

Question 16

What are intercalated discs?

Answer 16

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

Question 17

What is the other cell in the myocardium and what does it do?

Answer 17

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)

Question 18

What are Purkinje fibers?

Answer 18

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

Question 19

What is the endocardium?

Answer 19

The inner layer of the heart

Lines chambers

Has 4 sublayers - subendocardium, myoelastic CT layer, subendothelium, and endothelium

Question 20

What is the structure and function of the subendocardium of the endocardium?

Answer 20

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

Question 21

What is the structure and function of the myoelastic CT layer of endocardium?

Answer 21

Smooth muscle cells, elastic fibers, and some collagen I

Facilitates contraction/expansion of endothelium

Question 22

What is the structure and function of the subendothelial layer?

Answer 22

Collagenous or fibroelastic CT (lots of collagen I fibers and some elastic fibers)

Anchors endothelium to rest of endocardium

Question 23

What is the structure and function of the endothelium?

Answer 23

Layer closest to chamber lumen

Simple squamous epithelium

Lines heart chambers

Question 24

What is the conduction pathway of the heart?

Answer 24

SA node - conducting cells along atrial walls - AV node - along fibrous skeleton - AV Bundle (of His) - R and L bundle branches - Purkinje fibers

Question 25

What is the SA node?

Answer 25

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

Question 26

What is the AV node?

Answer 26

Delays transmission of signals from atria to ventricles Ensures atrial contraction precedes ventricular contraction AV nodal cells look pretty similar to pacemaker cells

Question 27

What are Purkinje fibers specialized for?

Answer 27

Highly specialized for rapid impulse transmission Mainly located in the subendocardium and eventually terminate in myocardium

Question 28

What are important characteristics about Purkinje fibers?

Answer 28

2x the diameter of normal contractile cells - faster conduction velocity and faster repolarization 3x more gap junctions in their intercalated discs Lighter staining

Question 29

What is the function and structure of the cardiac skeleton?

Answer 29

Fibrous - dense irregular collagenous CT Flexible anchor for cardiac muscle tissue - can withstand pulling from several directions during heart contraction

Question 30

What is the structure and function of heart valves?

Answer 30

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

Question 31

How many layers do valves have?

Answer 31

5 layers

Question 32

What are the 5 layers of the valves in the order of the direction of blood flow?

Answer 32

Endothelium - inflow surface Elastic layer - inflow side Spongiosa - central core Fibrosa - outflow side Endothelium - outflow surface

Question 33

What 3 layers of the valves are composed of fibroelastic CT?

Answer 33

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)