Cardiovascular system

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Questions and Answers

What separates the two atria in the heart?

Atrioventricular valve

Interventricular septum

Interatrial septum (correct)

Cardiac vessels

What is the primary function of the ventricles during the cardiac cycle?

Pump blood out of the heart (correct)

Conduct electrical signals

Prevent backflow from the arteries

Receive blood from the atria

What happens during diastole in the cardiac cycle?

The heart is beating rapidly

The heart muscles contract

Blood is pumped out of the ventricles

Blood fills the heart with relaxation (correct)

Which valve prevents backflow of blood into the right atrium during ventricular contraction?

Tricuspid valve Signup and view all the answers

What structure is responsible for the thick muscular separation between the left and right ventricles?

Interventricular septum Signup and view all the answers

What structure prevents backflow of blood into the left atrium during ventricular contraction?

Bicuspid mitral valve Signup and view all the answers

During which phase does blood pass from the left atrium to the left ventricle?

Diastole Signup and view all the answers

Which heart sound is associated with the closing of the atrioventricular valves?

S1 ('Lub') Signup and view all the answers

What is the role of the sinoatrial (SA) node in the heart's conduction system?

Serves as the heart's pacemaker Signup and view all the answers

Which part of the heart's conduction system directly conducts impulses to the ventricles?

Bundle of His Signup and view all the answers

What does an electrocardiogram (ECG) measure during a heartbeat?

Rhythm and electrical activity Signup and view all the answers

Which wave on an ECG corresponds to atrial depolarization?

P wave Signup and view all the answers

What condition could an ECG help to detect?

Heart attacks Signup and view all the answers

What structural feature of the left ventricle allows it to pump blood more effectively than the right ventricle?

Thicker walls Signup and view all the answers

What is the significance of heart murmurs in relation to heart valves?

They result from turbulence created by valve closure. Signup and view all the answers

What is the primary function of the left side of the heart?

Pumping blood to the body Signup and view all the answers

Which layer of the heart wall is primarily responsible for contraction?

Myocardium Signup and view all the answers

Where is the heart located within the body?

In the mediastinum Signup and view all the answers

What is the purpose of the pericardial fluid?

To reduce friction between the heart and surrounding organs Signup and view all the answers

Which structure is responsible for connecting cardiac muscle cells?

Intercalated discs Signup and view all the answers

Which of the following statements about cardiac muscle is correct?

It is controlled by the autonomic nervous system. Signup and view all the answers

The apex of the heart points in which direction?

Downwards towards the diaphragm Signup and view all the answers

Which chambers of the heart are considered the receiving chambers?

Left atrium and right atrium Signup and view all the answers

What is the primary function of the right atrium?

Receiving deoxygenated blood from the body Signup and view all the answers

Which component of the pericardium adheres directly to the heart's surface?

Visceral pericardium Signup and view all the answers

What is the primary function of the circulatory system?

To circulate blood and transport nutrients Signup and view all the answers

How does pulmonary circulation function?

Transports deoxygenated blood from the right ventricle to the lungs Signup and view all the answers

Which blood vessels supply oxygenated blood directly to the heart?

Coronary arteries Signup and view all the answers

Which roles do veins play in the circulatory system?

Serve as a reservoir of blood and prevent backflow Signup and view all the answers

What type of blood vessels are suited for exchange of oxygen and nutrients?

Capillaries Signup and view all the answers

Which feature is characteristic of the blood-brain barrier?

It protects the brain from foreign substances Signup and view all the answers

What connects the fetus to the placenta during fetal circulation?

Umbilical cord Signup and view all the answers

Which vessels receive deoxygenated blood from the upper and lower body?

Superior and inferior vena cava Signup and view all the answers

What are the primary layers of an artery's wall?

Tunica externa, tunica media, tunica intima Signup and view all the answers

What is a key role of the foramen ovale during fetal circulation?

To bypass the pulmonary circulation Signup and view all the answers

Study Notes

The Heart: Structure and Function

The heart is a four-chambered muscular organ, roughly fist-sized, beating approximately 100,000 times daily.
It functions as two separate pumps: the right heart pumps blood to the lungs, and the left heart pumps blood to the body.
Located in the mediastinum of the thoracic cavity, between the lungs, it sits behind the sternum, mostly to the left of the midline, with its apex pointing downwards.

Heart Structure: Pericardium and Heart Wall

Enclosed by the parietal pericardium (pericardial sac), separating the heart from other thoracic organs and containing pericardial fluid.
The parietal pericardium has an outer fibrous and inner serous layer; the serous layer secretes pericardial fluid.
The heart wall comprises three layers: the epicardium (outer), myocardium (thick middle layer of cardiac muscle), and endocardium (smooth inner layer).

Cardiac Muscle

Found only in animal hearts, controlled by the autonomic nervous system.
Branched, striated fibers connected by intercalated discs (containing fascia adherens, gap junctions, and desmosomes).
This structure allows smooth, repetitive contractions.

Heart Chambers

Divided into four chambers: two atria (receiving chambers) and two ventricles (pumping chambers).
Atria are separated by the interatrial septum; ventricles by the interventricular septum.
Grooves on the heart surface indicate chamber partitions and contain cardiac vessels supplying the heart wall.

Right Atrium and Ventricle

The right atrium receives venous blood from the superior and inferior vena cava.
The cardiac cycle involves diastole (relaxation and filling) and systole (contraction).
During diastole, blood flows from the right atrium to the right ventricle through the tricuspid valve.
During systole, the tricuspid valve closes, preventing backflow.

Left Atrium and Ventricle

Oxygenated blood from the lungs enters the left atrium via the pulmonary veins.
During diastole, blood flows from the left atrium to the left ventricle through the bicuspid (mitral) valve.
During systole, the mitral valve closes to prevent backflow.
The left ventricle has thicker walls than the right.
Oxygenated blood exits the left ventricle via the aorta.

Heart Sounds

Heart sounds (S1 'Lub' and S2 'Dub') are produced by valve closure.
Variations in these sounds (heart murmurs) may indicate valve problems.

Conduction System of the Heart

Consists of the sinoatrial (SA) node (pacemaker), atrioventricular (AV) node, Bundle of His, and Purkinje fibers.
The SA node initiates each heartbeat through spontaneous depolarization (pacemaker potential).
The impulse spreads across the atria (atrial systole), then to the AV node, which delays the impulse to allow atrial emptying.
The Bundle of His conducts the impulse to the Purkinje fibers in the ventricles.

Electrocardiogram (ECG)

A non-invasive test measuring heart electrical activity.
The ECG trace shows P wave, QRS complex, and T wave, reflecting atrial depolarization, ventricular depolarization and repolarization, respectively.
It detects arrhythmias, enlarged heart, hypertension, and myocardial infarction.

Circulatory System

Also known as the cardiovascular system.
Circulates blood, transports nutrients, oxygen, hormones, removes waste, and controls homeostasis.
Includes pulmonary circulation (heart to lungs to heart) and systemic circulation (rest of the body).

Coronary Circulation

The heart's own circulatory system.
Oxygenated blood is delivered by the right and left coronary arteries.
Blood from the myocardium enters cardiac veins and flows into the right atrium.

Foetal Circulation

Pulmonary circulation is unnecessary in utero due to placental oxygenation.
The umbilical cord connects the fetus to the placenta.
Systemic venous blood is shunted from the right atrium to the left atrium via the foramen ovale.
Blood from the left ventricle is diverted away from the pulmonary circulation.

Blood Vessels

Arteries: carry oxygenated blood away from the heart (except pulmonary artery), have thick elastic muscular walls, and blood flows under high pressure. They have three layers: tunica externa, tunica media, and tunica intima.
Capillaries: smallest and most abundant vessels; walls consist of endothelium only, allowing rapid exchange of substances. Three types exist: continuous, fenestrated, and discontinuous (sinusoidal).
Veins: carry deoxygenated blood back to the heart; contain valves to prevent backflow; act as a blood reservoir; rely on skeletal muscle and respiratory pumps; have three layers, but less muscular/elastic than arteries.

Blood-Brain Barrier

A selective boundary between blood and the brain/spinal cord.
Protects the brain from foreign substances and maintains a constant environment.
Brain capillaries are not fenestrated, and their endothelial cells are tightly packed, preventing large molecules, immune cells, bacteria, and viruses from entering the central nervous system.

Major Blood Vessels: Great Vessels

Arteries: Pulmonary artery (deoxygenated blood from right ventricle to lungs), Aorta (oxygenated blood from left ventricle to body), Aortic arch (with ascending and descending segments).
Veins: Pulmonary veins (oxygenated blood from lungs to left atrium), Superior vena cava (deoxygenated blood from upper body to right atrium), Inferior vena cava (deoxygenated blood from lower body to right atrium).

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