Cardiovascular System: Heart and Blood Vessels Vocabulary

Vocabulary flashcards covering heart anatomy, heart wall layers, cardiac conduction, ECG components, blood vessel tunic structure, vessel classifications, capillary exchange, and hemodynamics based on Chapter 20 and Chapter 21 lecture notes.

Mediastinum

The anatomical region extending from the sternum to the vertebral column, the first rib, and between the lungs where the heart is located.

Fibrous pericardium

The tough, outer layer of dense irregular connective tissue surrounding the heart that prevents overstretching and provides physical protection.

Serous pericardium

The thinner, delicate double-layered membrane of the pericardium consisting of an outer parietal layer fused to the fibrous pericardium and an inner visceral layer.

Epicardium

The external layer of the heart wall, also known as the visceral layer of the serous pericardium, composed of mesothelium and connective tissue.

Myocardium

The middle layer of the heart wall that constitutes approximately $95\%$ of the heart mass, composed of cardiac muscle tissue responsible for pumping blood.

Endocardium

The smooth inner lining of the heart wall composed of endothelium and connective tissue that covers the chambers and valves, continuous with the endothelial lining of large blood vessels.

Auricles

Pouch-like structures located on the external surface of each atrium that increase the capacity of the atria to hold blood.

Fossa ovalis

An oval depression in the interatrial septum that represents the remnant of the fetal foramen ovale, which typically closes 6 to 12 months after birth.

Trabeculae carneae

Raised ridges formed by rounded or irregular bundles of cardiac muscle fibers on the inner walls of the ventricles.

Ligamentum arteriosum

The fibrous remnant of the fetal ductus arteriosus, which shunted blood from the pulmonary trunk to the aorta during development and closes 12 to 24 hours after birth.

Lubb

The first loud heart sound caused by blood turbulence associated with the closure of the atrioventricular (AV) valves during ventricular contraction.

Dupp

The second loud heart sound caused by blood turbulence associated with the closure of the semilunar (SL) valves during ventricular relaxation.

Intercalated discs

Irregular transverse thickenings of the sarcolemma connecting adjacent cardiac muscle fibers, containing desmosomes for structural attachment and gap junctions for electrical conduction.

Sinoatrial (SA) node

The natural pacemaker of the heart located in the right atrial wall that spontaneously and repeatedly generates action potentials to trigger heart contractions.

P wave

The wave on an electrocardiogram (ECG) that represents atrial depolarization and precedes atrial contraction.

QRS complex

The deflection wave complex on an ECG that represents rapid ventricular depolarization prior to ventricular contraction, while masking atrial repolarization.

T wave

The wave on an ECG that represents ventricular repolarization, occurring just as the ventricles begin to relax.

Cardiac output (CO)

The total volume of blood ejected from the left or right ventricle into the aorta or pulmonary trunk per minute, calculated as $\text{CO} = \text{Stroke Volume (SV)} \times \text{Heart Rate (HR)}$.

Preload

The degree of stretch on the cardiac muscle fibers prior to contraction, described by the Frank-Starling law of the heart.

Afterload

The pressure that must be overcome in the systemic or pulmonary arterial trunks before a semilunar valve can open and allow blood ejection from the ventricles.

Vasa Vasorum

Microscopic blood vessels ("vessels of vessels") located within the tunica externa that supply blood to the thick tissues of large arterial and venous walls.

Tunica media

The muscular and elastic middle layer of a blood vessel wall, containing smooth muscle cells that regulate lumen diameter via vasoconstriction and vasodilation.

Elastic arteries

Large-diameter conducting arteries with thin walls relative to size and abundant elastic fibers that function as a pressure reservoir during ventricular relaxation.

Muscular arteries

Medium-sized distributing arteries whose tunica media contains a high proportion of smooth muscle, enabling extensive vasoconstriction and vasodilation.

Anastomoses

Unions of branches of two or more blood vessels supplying the same body region, providing alternative pathways for blood circulation known as collateral circulation.

Precapillary sphincters

Rings of smooth muscle located at the entrance of capillaries that open and close to monitor and regulate blood flow through capillary beds.

Continuous capillaries

The most common type of capillary, characterized by an uninterrupted endothelial lining connected by tight junctions.

Fenestrated capillaries

Capillaries featuring small pores or openings (fenestrations) in their endothelial walls, allowing heightened permeability to small solutes and fluid.

Sinusoids

Wide, winding capillaries with unusually large fenestrations, large intercellular clefts, and incomplete basement membranes that allow proteins and whole red blood cells to pass into or out of circulation.

Transcytosis

A capillary exchange process in which large, lipid-insoluble plasma molecules are enclosed in pinocytotic vesicles, cross endothelial cells via endocytosis, and exit via exocytosis.

Vascular resistance

The opposition to blood flow caused by friction between blood and vessel walls, dependent on lumen size, blood viscosity, and total vessel length.

Cardiovascular center (CVC)

A nucleus in the medulla oblongata that regulates heart rate, stroke volume, neural and hormonal mechanisms, and blood vessel diameter.

Baroreceptors

Pressure-sensitive sensory receptors located in the neck and thorax that monitor blood pressure changes and the degree of stretch in arterial walls.

Proprioceptors

Sensory receptors that monitor movement in joints and muscles, providing sensory input to the cardiovascular center to increase heart rate during physical activity.

Tachycardia

An abnormally elevated resting pulse rate or heart rate exceeding $100\text{ beats/min}$.

Bradycardia

An abnormally slow resting pulse rate or heart rate falling below $60\text{ beats/min}$.

Hepatic portal circulation

A specialized venous route that collects blood from the stomach, intestines, pancreas, spleen, and gallbladder and channels it through the hepatic portal vein to the liver for processing and detoxification.