**1. Introduction**

The cardiovascular system acts as the engine that drives the human body. It is responsible for transporting oxygen, nutrients, hormones, and enzymes throughout the body, as well as removing carbon dioxide and other waste products from it [1]. This cardiovascular system is mainly separated into two parts—(i) the pulmonary circulation and (ii) the systemic circulation, which are supplied by the right and left ventricles of the heart, respectively [2]. Each of these circulations is constituted of the respective heart pump, the microcirculation, the arteries, and the veins. Basically, the cardiovascular system is a well-regulated carrier syntax of the body that allows the circulation of blood throughout an intact system under varying pressure gradients,

generated by the pumping mechanism, with the heart serving as the core pumping unit [3]. This heart is a super sophisticated and highly developed organ that integrates a diverse range of anatomical and functional features to fulfill its fundamental pumping function. It is not just a sophisticated information processing and encoding center [4], but it also functions as an endocrine gland that is capable of generating and releasing its hormones and neurotransmitters [5–8]. The heart is positioned in the center of the chest, between the lungs in humans. An average human heart measures around the size of a clenched fist and its mass falls within the range of 250–350 grams, with a typical beating of around 100,000 times per day (approximately 72 beats per minute (bpm)) [9]. The interior anatomy of the heart exposes four myocardial chambers—two atria and two ventricles. The two atria are the upper chambers that primarily serve as the collecting chambers; whereas the two ventricles are the lower chambers that primarily function as the blood-pumping chambers [10]. A healthy heart has a set of four valves that keep blood flowing in one direction to prevent backflow. The rate and strength of the heart's contractions dictate cardiac functioning [4]. The cardiovascular system entails the blood vessels as well, which circulate the blood pumped by the heart throughout the body. Since the heart and blood vessels are integral parts of the cardiovascular system, any damage or dysfunction of the heart or blood vessels can have catastrophic repercussions, leading to severe cardiovascular diseases (CVDs) and even death [11].

CVDs encompass a wide spectrum of disorders, including diseases of the heart muscle and the vascular system that supplies the brain, heart, and other vital organs with blood and oxygen. CVDs are the preeminent cause of death worldwide, claiming the lives of an estimated 17.9 million people annually [12], with the majority (80%) of these deaths occurring in developing nations [13]. The prevalence of CVDs is projected to increase as their risk factors become more pervasive in formerly low-risk countries. The death toll from CVD is currently three times higher in developing countries than that in developed ones [14]. According to the estimation of the World Health Organization (WHO), more than 75% of premature CVDs are avertible and the mitigation of the risk factors can assist to deal with the rising burden of CVDs [15]. Moreover, WHO has emphasized the importance of lifestyle factors such as unhealthy diet habits, tobacco use, psychological stress, and physical inactivity contributing to the rise of CVD, and according to the estimation of WHO, three-quarters of deaths caused by CVDs might be avoided with united efforts [16]. Furthermore, an early diagnosis of CVDs is pivotal for reorienting the focus of therapy toward prevention rather than treatment [17]. However, in recent years rapid progress is being made in the treatment of heart diseases. Several therapeutic choices are constantly being presented to cardiologists caring for patients with CVDs . The most frequently prescribed drugs for CVDs include beta-blockers, angiotensin-converting enzyme (ACE) inhibitors, angiotensin II receptor blockers (ARB), alpha-adrenoceptor blockers, adrenergic receptor blockers, antihypertensive drugs, vasodilators, nitrates, calcium channel blockers, potassium channel activators, diuretics, positive inotropic drugs, antiarrhythmic drugs, sympathomimetic drugs, anticoagulants and protamine sulfate, antiplatelet drugs, fibrinolytic drugs and lipid-lowering agents etc. [18]. According to the Bangladesh Unani, Ayurvedic and Herbal pharmacopeia, a lot of plant-derived medications are also applied for the treatment of these ailments.

This book chapter aims to present a succinct and simplistic review of the basic physiological and anatomical aspects as well as the pathological information regarding the cardiovascular system. Additionally, this chapter includes information on the diagnosis, treatment, and prevention of CVDs.

## **2. Cardiovascular system**

Every living body relies on a functioning cardiovascular system, which is a complex and multifaceted physiological system with numerous regulatory sub-systems controlled by the central and peripheral autonomic nervous systems as well as humoral factors [19]. The cardiovascular system is primarily responsible for supplying the body's cells with the materials they require to function properly and for removing the waste products that they make as a result of their metabolic processes. It is responsible for transporting blood throughout the body. It is controlled by numerous stimuli, including sympathetic and parasympathetic nervous systems, changes in blood volume, electrolytes, hormones, osmolarity, adrenal glands, kidneys, medications etc. [20–23].

The fundamental role of the cardiovascular system is to meet the metabolic requirements of the body as well as transporting carbon dioxide and other wastes out of the body. This function is accomplished in two ways—by maintaining a healthy circulatory system and by keeping blood pressure at an optimum level.

#### **2.1 Divisions of the cardiovascular system**

The circulatory system has two functionally opposite divisions through which blood flows—systemic circulation and pulmonary circulation as shown in **Figure 1**.

#### *2.1.1 Systemic circulation*

This circulation is more generally referred to as greater or superior circulation with a highly elevated resistance circuit [3]. It commences at the left ventricle and terminates in the right atrium [3]. The left ventricle pumps blood which is traveled through a set of blood vessels known as the arterial system [24]. At the capillaries, blood and tissue exchange a variety of substances. Following such exchange, blood turns back to the right atrium of the heart via the venous system. After that, the right ventricle receives blood from the right atrium. As a consequence of this systemic circulation, the oxygenated blood from the heart travels to the tissues, while venous blood from the tissues returns to the heart [3].
