Human Anatomy Unit 3

Cardiovascular System

1. Heart: Pumps blood 

2. Arteries: carries blood away from heart

3. Veins: carries blood toward the heart

Pulmonary Circuit

Route between heart & lungs that allows blood to pick up oxygen.

Right ventricle of heart → Pulmonary trunk and arteries → Lungs → Pulmonary veins → Left atrium of heart

Systemic Circuit

Route between heart & tissues of the body (other than the lungs) that brings oxygen out to cells.
Left ventricle of heart → Aorta & branches → Cells of the body → Veins → Right atrium of heart

Heart Basics

• Pumps ~1800 gallons/day through 60,000 miles of blood vessels

• Approximately fist-sized 

• Sits to the left of the midline & on top of the diaphragm

• 4 distinct chambers

Pericardium

Heart is contained within a pericardial sac known as the pericardium.

Fibrous pericardium

Touch outer layer of sac that anchors heart and prevents overfilling; dense irregular CT

Serous pericardium

Serous membrane around heart

Parietal layer of serous pericardium

Inner layer of sac, secretes serous fluid

Visceral layer of serous pericardium

Outer layer of heart, secretes serous fluid (epicardium)

Pericardial cavity

Space between parietal & visceral layers; filled with serous fluid

Myocardium

Cardiac muscle tissue; left ventricle has thickest layer of cardiac muscle

Endocardium

Simple squamous epithelium

Heart wall

1. Visceral layer (epicardium)

2. Myocardium

3. Endocardium

Superior & Inferior vena cava

Large veins that return deoxygenated blood from the body into the right atrium

Tricuspid (right atrioventricular) valve

separates right atrium from right ventricle 

Chordae tendineae

Dense regular CT that attaches cusps of tricuspid valve to ventricle wall and other end attaches to papillary muscles.

Papillary muscle

Projection of cardiac muscle in the ventricular walls; right ventricle contains 3 papillary muscles that attach to the tricuspid valve

Pulmonary semilunar valve

Separates right ventricle from pulmonary trunk (artery)

Pulmonary veins

return oxygenated blood to heart from lungs

Bicuspid/mitral (left atrioventricular) valve

Separates left atrium from left ventricle 

Aortic semilunar valve

Separates left ventricle from the aorta 

Blood flow through the heart

Tricuspid & Bicuspid/Mitral (right & left atrioventricular) valves

• Named by # of cusps per valve

• Cusps formed of endocardium reinforced with dense CT

• Chordae tendineae prevent valves from inverting into the atria when the ventricles contract

Function of the atrioventricular valves (tricuspid & bicuspid)

Atrioventricular valves open as gravity and atrial contraction moves blood from the atria to the ventricles. Ventricles are at rest.

Pulmonary & Aortic Semilunar valves

• Valve cusps resemble pockets 

• Blood pushes them open when the ventricles contract 

• When ventricles relax, blood fills the pockets and forces the valve closed

Function of the semilunar valves

As ventricles contract, blood is pushed up against the semilunar valves, forcing them open.

Heart Murmur

Noise in the heart caused by blood leaking past a closed valve

Mitral valve prolapse

Most common; weakness in the collagen of the valve or chordae tendinae

Stenosis

Narrowed opening between valves, may be caused by calcium deposits or illness

Cardiac muscle

• Striated muscle cells connected by intercalated discs

• Some of the cells are adapted to conduct an impulse instead of contracting

Gap junctions

Allow for quick communication between cells for a coordinated contraction

Fascia adherens

Desmosome-like connections; provide strength

Sinoatrial (SA) node

 In the right atrium; initiates the electrical impulse 

• Pacemaker 

• Inherent Rhythmicity (automaticity)

Internodal pathway

Carries impulse away from SA node to AV node

Atrioventricular (AV) node

Delays impulse before it is passed on to the ventricles

Fibrous skeleton

Barrier between the atria and ventricles that prevents an electrical impulse from passing 

Only one pathway from atria to ventricles: AV node

The conducting system of the heart

• Atria contract top to bottom

• Ventricles contract bottom to top

Cardiac cycle

Cardiac Cycle: 1 heartbeat; ~0.8 seconds/cycle 

Systole

Contraction (forcing blood out)

Diastole

Relaxation (filling with blood)

Heart needs an external blood supply

• Right coronary artery & branches

• Left coronary artery & branches

Atherosclerosis

Build-up of plaques which cause narrowing of artery

Most common cause of arteriosclerosis (any hardening of arteries)

Some causes: 

• Damage to inner surface (endothelium) caused by inflammatory response to smoking, diabetes, high blood pressure, etc.

• Cholesterol, calcium, and lipids can attach damaged lining and harden into plaques

Myocarial Infarction

Heart Attack; Result of blood not reaching cardiac muscle tissue

Thrombus

Blood clot

Ischemic

Restriction in blood supply resulting in oxygen and glucose deprivation of tissues

Balloon angioplasty without stent

Procedure used to open up a narrowed or blocked blood vessel (usually an artery) using only a balloon catheter, without placing a stent afterward; One alternative to bypass surgery

Coronary bypass

A type of open-heart surgery used to restore blood flow to the heart muscle when one or more of the coronary arteries are blocked or severely narrowed.

Blood vessels

• Transport blood

• Continuous circuit between heart and capillaries

Lymph vessels

• Transports lymph: fluid that has accumulated in tissues

• One way: not a circuit 

Tunica intima

• Endothelium: simple squamous epithelium 

• Subendothelial layer: loose areolar CT

• Veins forms valves

• A layer of the vessel walls

Tunica media

Smooth muscle arranged circularly to allow for vasoconstriction; artery is thicker with more elastic fibers; a layer of the vessel walls

Tunica externa

loose areolar CT

• Vaso vasorum: blood vessels that run through this layer and supply cells of vessel wall

• Tunica externa of veins have equal thickness or thicker than arteries

Arterial walls are thicker and stronger than veins:

must withstand the higher pressure of blood pumped from the heart.