Heart Pt 1

pages 1-11

Cardiovascular System

Comprises the heart and blood vessels to circulate blood throughout the body, forming a closed circulatory loop. Transports oxygen, nutrients, hormones, and removes waste from tissues.

Divided into pulmonary and systemic circuit.

*Aids in immune defense by transporting white blood cells and antibodies throughout the body.

Pulmonary circuit

Sends blood from R side of the heart to the lungs for oxygenation.

Systemic circuit

Distributes oxygenated blood from L side of the heart to all body systems.

Arteries

Carry blood away from the heart. Blood flows from the heart into large arteries, then to smaller arteries, then into arterioles, and finally capillaries.

Veins

Carry blood towards the heart. Blood flows from capillaries into venules, then into larger veins, and returns to the heart.

Capillaries:

Allow for the exchange of substances between blood and surrounding tissues.

The Heart

Approximately the size of a clenched fist, proportional to body size, exercises can grow larger.

Between the second and fifth pairs of ribs in the mediastinum.

Apex points toward the left hip.

Pericardium

A sac surrounding the heart with 2 layers: the fibrous layer and the serous layer.

The cells making up parietal and visceral layer of the serous pericardium, secrete a slippery pericardial fluid that prevents friction between the parietal and visceral layers as the heart beats.

*The visceral layer of the serous pericardium is exactly the same as the epicardium - the most outside layer of the heart organ.

Fibrous pericardium layer

Tough outer layer made of dense connective tissue. Anchors the heart in the thoracic cavity and prevents the heart from overfilling and over expanding when blood volume increases.

Serous pericardium layer

Underneath the fibrous layer. Serous membrane consisting of two layers, parietal layer and visceral layer.

Heart Wall Layers

Consist of three layers epicedium, myocardium, and endocardium.

Epicardium

The outermost layer of the heart. Exactly the same as the visceral layer of the serous pericardium.

Myocardium

The middle layer of the heart. It is the thickest muscle layer, containing cardiac muscle cells, blood vessels, and nerves.
Cardiac muscle cells = cardiomyocytes = heart muscle cells.

Endocardium

The inner layer of the heart, the deepest one lining the wall of the heart chambers. Made of simple squamous epithelium providing a smooth surface for blood flow.

Endocarditis

Inflammation of the endocardium, can lead to serious complications due to potential damage to the heart.

Pericarditis

Inflammation of the pericardium, causing chest pain and discomfort with each heartbeat.

Endocarditis

Inflammation or infection of the endocardium, potentially leading to damage to heart valves and systemic complications.

Cardiac Muscle (Myocardium)

Have striations and are connected by intercalated discs consisting of desmosomes and gap junctions.

*Desmosomes prevent the cells from separating when the heart contracts.

*Gap junctions allow spread of electrical current between cardiac muscle cells. This creates a coordinated contractile wave during heartbeats.

Heart Structure

Two atria and two ventricles. Atria have pouch-like structures called auricles, increasing their capacity.

- On the heart's surface we see sulci and grooves that help define the chambers and separate them.

- Interatrial groove separates the atria into right and left.

- Interventricular septum separates the right and left ventricles.

- Interatrial septum separates the right and left atria.

* The function of these two septa is to prevent blood mixing from the right (oxygen-poor blood) and left (oxygen-rich blood) sides of the heart, maintain the efficiency of the cardiovascular system.

Coronary sulcus

Separates atria from ventricles and contains coronary vessels.

Anterior and posterior interventricular sulci

Separate ventricles in the anterior and posterior aspects of the heart.

Right atrioventricular (AV) valve

Separates the right atrium and the right ventricle. Right AV valve is also called tricuspid valve.

Left atrioventricular (AV) valve

Separates the left atrium and the left ventricle. Left AV valve is also called bicuspid valve or mitral valve.

RIGHT Side of the Heart

Deoxygenated blood arrives at the right atrium of the heart

*Blood is brought to the right atrium of the heart by the superior vena cava, inferior vena cava, and the coronary sinus.

~ 70% of the blood moves passively (due to gravity) into the right ventricle.

~ 30% of the blood is left inside the right atrium and is then ejected into the right ventricle when the right atrium contracts.

*When the right ventricle is filled up with blood, the blood is pumped from the bottom up into the pulmonary trunk.

Superior vena cava

Brings blood from the upper body.

Inferior vena cava

Brings blood from the lower body.

Coronary sinus

Brings blood from heart organ itself.

Pulmonary trunk

Branches into 2 pulmonary arteries that carry the blood into the lungs (pulmonary circuit) for oxygenation.

* 2 pulmonary arteries - 1 for each lung. The right pulmonary artery takes blood into the right lung, the left pulmonary artery takes blood into the left lung.

LEFT Side of the Heart

Oxygenated blood coming from the lungs, arrives at the left atrium of the heart.

Blood is brought to the left atrium of the heart by the pulmonary veins (4 pulmonary veins - 2 from each lung)

~ 70% of the blood moves passively (due to gravity) into the left ventricle.

~30% of the blood is left inside the left atrium and is then ejected into the left ventricle when the left atrium contracts.

*When the left ventricle is filled up with blood, the blood is pumped from the bottom up into the aorta. Aorta branches into several blood vessels that carry the blood into all body systems (systemic circuit).

Coronary arteries

Supply blood to the heart organ itself. Coronary arteries branch off at the base of the aorta.

* As blood is ejected out of the left ventricle into the aorta, blood goes up against gravity and then it weighs down. When it weighs down, the blood is inhibited from going back into the left ventricle because there is a valve at the entrance of the aorta - the aortic semilunar valve. The aortic semilunar valve has the cups in a halfmoon shape. When the blood weighs down, it fills up the cups of the semilunar valve and that causes the valve to close.

Right Coronary Artery (RCA)

The RCA supplies blood to the right atrium, the right ventricle, and the conduction system of the heart! It penetrates deep inside the right atrium wall to supply blood to specialized cells of the conduction system.

*Leaves the base of the aorta and follows the right direction along the coronary sulcus. It keeps going around the heart until it reaches the posterior aspect of the heart. Then it starts to go down between the ventricles, and it is called Posterior Interventricular Artery.

Left Coronary Artery (LCA)

Leaves the base of the aorta and follows the left direction. As soon as the LCA passes behind the pulmonary trunk it splits into 2: the Circumflex artery that keeps going left along the coronary sulcus, and the Anterior Interventricular Artery, the branch of the LCA that keeps going down, between the ventricles, in the anterior aspect of the heart.

The LCA supplies blood to the left atrium and the left ventricle.

Coronary thrombosis

Caused by the formation of a blood clot in a coronary artery can lead to myocardial infarction (heart attack) due to inadequate blood supply to a portion of the heart muscle.

- Symptoms of myocardial infarction include chest pain, shortness of breath, and sweating, requiring prompt medical intervention to restore blood flow and prevent tissue damage.

- Severity of coronary thrombosis depends on duration and affected area.

Coronary veins

Collect deoxygenated blood from the heart organ itself and take this
"used" blood into the right atrium of the heart.

*The Great Cardiac Vein, Middle Cardiac Vein and Small cardiac vein dump their deoxygenated blood into the Coronary Sinus, a blood vessel that is in the posterior aspect of the heart along the coronary sulcus. The Coronary Sinus takes the deoxygenated blood into the right atrium of the heart.

Anastomosis

Physical connection between blood vessels.

Anastomosis between: Two arteries (Arterial anastomosis), Two veins (Venous anastomosis), An artery and a vein (Arteriovenous anastomosis)

Heart Anastomosis

Interconnected network of capillaries receives blood from two different arteries (collateral arteries - independent arteries that supply blood to the same area, ensuring adequate blood supply to the heart tissue in case one of the arteries becomes blocked.

• Increased arterial anastomoses improve tissue perfusion and reduce the risk of ischemic injury. *Ischemic - death of cells due to deprivation of oxygen caused by inadequate blood supply.

Right Atrium of the Heart

- Interatrial septum between the right and left atria, ensures blood doesn’t mix.

- Superior, Inferior, Coronary sinus

Pectinate muscles

In the right atrial wall and right auricle maximize blood flow.

Fossa ovalis

Scar in the interatrial septum from the closure of the foramen ovale.

Foramen ovale

A hole in the interatrial septum during fetal development. Allows blood to flow from the right atria to the left atria, serves as a shortcut since the blood does not need to go to the lungs to be oxygenated during embryonic development.

It closes at birth becoming the fossa ovalis

*If the hole doesn't close completely or at all, it can lead to a "hole in the heart" condition.

Right Atrioventricular Valve = Tricuspid Valve

Valve between the right atrium and right ventricle. It prevents retrograde (backward) blood flow during ventricular contraction.

Right Ventricle of the Heart

Trabeculae carneae, Moderator band, chordae tendineae,

Trabeculae carneae

(muscular ridges in the ventricular wall that enhance contractility, ensuring efficient ejection of blood into the pulmonary trunk.

Moderator band

Only in the right ventricle, band extending from the interventricular septum to the anterior wall of the right ventricle. Helps maximize blood ejection into the pulmonary trunk by serving as a shortcut for the electrical impulse that causes the ventricular cardiomyocytes to contract, allowing it to reach the anterior wall of the ventricle efficiently.

Chordae tendineae

Papillary muscles prevent valve cusps from turning inside out during contraction.

Ventricular contraction

Contract from the bottom of the heart up to eject blood into the blood vessels at the top part of the heart. Valves' cusps are held down by the chordae tendineae attached to the papillary muscles. Pressure of the blood filling up the ventricles closes valves, but the chordae tendineae attached to the papillary muscles keeps them closed.

Pulmonary semilunar valve

Valve between the right ventricle and the pulmonary trunk. At the entrance of the pulmonary trunk ensures one-way flow. It prevents retrograde (backward) blood flow during ventricular relaxation.

Left Atrium of the Heart

Four blood vessels bring blood to the left atrium:

2 Right Pulmonary Veins: oxygenated blood from the right lung.

2 Left Pulmonary Veins: oxygenated blood from the left lung.

Left Atrioventricular Valve = Bicuspid Valve = Mitral Valve

Valve between the left atrium and left ventricle. It prevents retrograde (backward) blood flow during ventricular contraction. Has 2 cups covered by endocardium - simple squamous epithelium, which means it is a single layer of flat cells.