Cardiovascular 3

epicardium

(Outer Layer) (homologous to Tunica Adventitia). But unlike blood vessel adventitia, consists of 2 layers -Deeper loose fatty connective tissue layer -Covered with mesothelium layer (pericardium)

sinoatrial, atrioventricular

-Part of Impulse Conducting System of Heart -Composed of Specialized Aggregates of Cardiac Myocytes _______ (SA) Node located in Wall of Right Atrium: Activates Atrial Myocardium. SA Node is normal natural pacemaker of heart. Responsible for initiation of cardiac cycle (heartbeat). Spontaneously Generates an Electrical Impulse, which after conduction throughout heart, causes heart to contract. ______ (AV) Node is part of Cardiac Electrical Conduction System that Electrically connects Atrial and Ventricular Chambers, which are otherwise electrically insulated from each other by Cardiac Skeleton. Impulse carried by Modified Cardiac Myocytes known as Bundles of His through intraventricular septum, and then distributed to ventricular walls by Purkinje Fibers.

atrioventricular, semilunar

4 Heart Valves: Attenuated Folds of Endocardium. Prevent backflow of blood. 2 ________ (AV) Valves: Intake valves for right and left ventricles, fed with blood from atria. -Right AV valve (3 leaflets); called the Tricuspid Valve. -Left AV Valve (2 leaflets ); called the Bicuspid Valve (or Mitral Valve) Free edges of AV Valves are continuous with thin tendinous cords, the Chordae Tendinae, which attach to Papillary Muscles present in the Ventricles. 2 ________ Valves: Two ventricles have out-take valves that guard the entrances to the Pulmonary Artery and the Aorta. These are called: Pulmonary Semilunar Valve (or Pulmonary Valve) Aortic Semilunar Valve (or Aortic Valve)

endocardium

Analgous to Tunica Intima Composed of: -Simple Squamous Endothelium (1 layer of endothelial cells) -Basal lamina -Subendocardial layer of connective tissue (collagen fibers, elastic fibers, scattered smooth muscle cells, immediately overlying myocardium) Veins, Nerves and Electrical Impulse Conducting System present in subendocardial region.

degenerating metabolic lesion of vessel

Atherosclerosis and cardiovascular disease Tunica Intima becomes thickened by Cholesterol Deposits and hardened by Inflammation and Degeneration •Involvement of coronary arteries leads to interruption of circulation to myocardium (Myocardial Ischemia) (inadequate blood supply) •Tunica Intima and Tunica Media are primarily involved Early stages are partly reversible. In late stages vessels become irreversibly

fibrous skeleton of heart

Cardiac Skeleton (____________), is a high density single structure of Collagenous Connective Tissue that forms/anchors valves and influences forces exerted through them.

heartblock

Damage to AV Node may result in ______. In this condition ventricles beat at their own dissociated slow rate.

bundle branch block

Damage to Bundles of His or Purkinje Fibers results in ________ (failure to excite affected branch, leading to asynchronous and irregular ventricular contraction).

cardiac skeleton

Heart possesses Framework of Dense Irregular Collagenous Connective Tissue (_________). Also known as Cardiac Rings Located between Atria and Ventricles Not a true Skeleton, but does provide: -Mechanical support for valves -Electrical insulation between atria and ventricles -Insertion point for cardiac muscle bundles

cardiac electrical conduction system

In some Subendocardial layers, elements of the Cardiac Conduction System are present, such as Purkinje fibers (Modified Cardiac Muscle Cells (Myocytes)) specialized for electrical conduction. Generally larger than cardiac myocytes, contain elevated levels of glycogen.

artherosis and cardiovascular disease

Leading cause of death in USA and other advanced countries (in the West, especially Scotland /Ireland ). Rates higher in some developing countries. Worse in Eastern Europe, worst in Russia. Bad Diet (saturated fats, red meats, refined sugar, salt, low fiber) Bad Genetics Cigarette smoking Alcohol consumption Lack of exercise Gender (affects men more frequently than women in most age groups) Systemic hypertension (high blood pressure) All play contributory role. Leading cause of death world-wide (responsible for 15.5% deaths globally). Not limited to the elderly

heart pericardium

One layer of Squamous to Cuboidal Mesothelial Cells - mainly secretory cells rests on a basal lamina and forms the Visceral Layer of the Pericardium. Visceral Layer then folds out on itself (reflects out) to form the Parietal Layer. Visceral and Parietal Layers and Fluid-Filled Space Between Them (Pericardial Sac) forms the Pericardium (a fibroelastic, fluid-filled sac that envelops the heart). Mesothelial Cells lining these 2 parts of pericardium secrete a thin film of clear, serous fluid (usually less than 50 mL) into the pericardial sac. Fluid lubricates the heart's surface during contraction to reduce friction. Deeper Epicardium (underlying Pericardium) contains adipose tissue to act as a shock absorber and support branches of coronary arteries and veins and lymphatics, and many nerve fascicles and ganglia.

heart valves

Similar to valve arrangement in veins. Each cardiac valve leaflet has Central Core of Dense Fibrous Connective Tissue, covered externally (both sides) by Endocardium (largely endothelium). In AV valves, the endocardium is thicker on the ventricular side than on the atrial side. Central connective tissue core dominated by mixture of: -Collagen and Elastic Fibers -But also incorporates Fibroblasts and occasional Smooth Muscle Cells Although the leaflets of the 2 Semilunar Valves (Pulmonary, Aorta) are thinner than those of the AV Valves; All 4 Heart Valves are built to same histologic plan

cardiac muscle

composed of cardiac myocytes

heart

develps embryologically from simple blood vessel and thus retains three concentric tunics of vessel walls. -In heart wall, organization and tissue composition of these layers (Endocardium, Myocardium, Epicardium) are modified to reflect the heart's main function as a 4-chambered muscular pump. Endocardium (Inner Layer) (homologous to Tunica Intima) in contact with blood filling heart chambers. Consists of Endothelium and underlying Connective Tissue. Myocardium (Middle Layer) (homologous to Tunica Media) forms bulk of heart wall. Composed of Cardiac Muscle. Epicardium (Outer Layer) (homologous to Tunica Adventitia). But unlike the Adventitia, the Epicardium consists of 2 layers (deeper loose fatty connective tissue layer, covered with mesothelium layer (pericardium)).

myocardium

forms most of thickness of heart wall Light Micrograph (LM) of Atrial Wall (H & E): Innermost Endocardium (En) lines Atrial Chamber. This prominent layer is continuous with intima of vessels entering/leaving heart. The Myocardium - the bulk of the heart wall - consists of bundles of cardiac muscle cells coursing in different directions and separated by Loose Connective Tissue (CT). The thin Epicardium (Ep) consists of adipose tissue and fibrous connective tissue covered by thin mesothelium. (´34)

myogenically

heart contracts ___ langendorff heart preparation Fresh isolated heart perfuse with oxygenated Krebs' Ringer solution will beat by itself for many hours .. Action potentials generated by SA Node

purkinje fibers

larger than cardiac myocytes and have more centrally placed nucleus. Stain more lightly with H&E than regular cardiac myocytes.

endocardium

usually thicker in the Atria than in the Ventricles. Inner surface of Ventricles have trabeculae that project into lumen; composed of cardiac muscle, called Papillary Muscles.

mycardium

•consists of interlacing bundles, or sheets, of Cardiac Muscle Cells embedded in richly vascularized, loose connective tissue. Muscle fibers in each sheet elaborate a complex spiral pattern that winds around atria and ventricles. Compared with Atrial Myocardium, much thicker Ventricular Myocardium reflects differences in workload of heart chambers. Cardiac Muscle Cells (Cardiac Myocytes) form a 3-D Anastomosing Network whereby intercalated discs link almost all the cells. Cardiac Muscle Cells and other cells insert into Cardiac Skeleton of Dense Fibrous Connective Tissue.