The Cardiovascular System (eBook)

Ian Peate (Autor)

eBook Download: EPUB

2024 | 1. Auflage
160 Seiten
Wiley (Verlag)
978-1-394-25236-7 (ISBN)

Infos

PEATE'S BODY SYSTEMS
THE CARDIOVASCULAR SYSTEM

A CONCISE, ILLUSTRATED, AND ACCESSIBLE GUIDE TO THE CARDIOVASCULAR SYSTEM

Each of the twelve volumes in Peate's Body Systems series is rooted in the belief that a deep and thorough understanding of the human body is essential for providing the highest standard of care. Offering clear, accessible and up-to-date information on different body systems, this series bridges the gap between complex scientific concepts and practical, everyday applications in health and care settings. This series makes for an invaluable resource for those committed to understanding the intricacies of human biology, physiology and the various systems that sustain life.

The Cardiovascular System is the perfect companion for students and newly registered practitioners across nursing and allied health fields with an interest in cardiovascular care, providing a comprehensive yet easy-to-digest guide for both academic and clinical application.

• Equips healthcare students and practitioners with the necessary information to provide safe and competent care
• Features colourful illustrations to aid comprehension, clarify complicated concepts, and render content more engaging and accessible
• Empowers readers to adapt to a rapidly evolving healthcare landscape, preparing them for the future of healthcare delivery
• Contains information necessary for effective patient care of those with heart failure, hypertension, and other cardiovascular diseases and conditions

IAN PEATE is a Visiting Professor at Northumbria University, a Senior Clinical Fellow at the University of Hertfordshire, and a Professorial Fellow at the University of Roehampton. He is also the Editor-in-Chief of the British Journal of Nursing and the Consultant Editor of the Journal of Paramedic Practice and the International Journal of Advancing Practice.

Textauszug

Chapter 1
Anatomy and Physiology: The Cardiovascular System

The cardiovascular system, also known as the circulatory system, is a complex network of organs and vessels responsible for circulating blood throughout the body. It consists of:

• Blood: the fluid in which materials are transported to and from tissues.
• Blood vessels: the system by which the blood moves to and through tissues and back to the heart.
• Heart: the pump driving blood throughout the body.

Blood provides the fluid environment for the cells of the body with blood vessels transporting the blood. Blood vessels are the network carrying the blood. The heart performs its work as a pump, maintaining blood circulation. The cardiovascular system is essential for maintaining overall health and homeostasis, ensuring all cells receive the necessary oxygen and nutrients whilst removing waste products.

Circulation is key to maintaining organs and tissues. This chapter discusses the anatomy and physiology of the cardiovascular system, the system maintaining blood volume and perfusion of tissues and organs. Understanding how circulation is fundamental to maintaining organs and tissues can help enhance patient care and safety across all spheres of practice.

Blood

Through the blood (and lymph) substances are transported around the body; it is the main transportation system of the body, playing a critical role in maintaining homeostasis and supporting the functioning of various body systems. Blood performs three general functions:

1. Transport: transportation of substances around the body, delivering oxygen to every cell.
2. Regulation: blood regulates fluid and electrolyte balance, acid−base balance (pH) and temperature.
3. Protection: clotting factors are present in the blood (thrombocytes), helping protect the body from haemorrhage; blood also contains leucocytes; they help fight infection.

Composition of Blood

A red sticky fluid, blood is classified as a connective tissue despite its fluid nature. Connective tissues connect, support and bind together various structures and organs in the body. Blood has several different components and can vary slightly from person to person; it can change in response to factors such as hydration, diet and overall health.

Blood consists of formed elements, for example, red blood cells (erythrocytes), white blood cells (leucocytes) and platelets (thrombocytes) (see Table 1.1).

Table 1.1 The three types of blood cells

Blood cell	Description	Role

Erythrocytes

Make up 90% of the formed elements of blood. Disc shaped (bi-concave). Young red blood cells contain a nucleus (nucleated), while this is absent in mature red blood cells, thereby increasing the oxygen‐carrying capacity of the cell. Red in colour due to the presence of the protein haemoglobin (Hb). Formed in the red bone marrow. Life span of approximately 120 days. Old and worn-out erythrocytes are destroyed in the liver and spleen.

Transportation of gases (take oxygen to cells and carry carbon dioxide away from cells).

Leucocytes

These are the largest of all blood cells. They lack Hb and, as such, are white in colour. Two categories: Granulocytes: Accounting for 75% of white blood cells, further divided into neutrophils, eosinophils and basophils. Agranulocytes: Divided into lymphocytes, 20% of all white blood cells and monocytes account for 5% of white blood cells. Leucocytes often only survive for a few hours but may live for months or years.

Provides the body with protection against infection and disease through the process of phagocytosis (engulfing and ingesting microbes, dead cells and tissues).

Thrombocytes

Also known as platelets. Granular, disc shaped with no nucleus. Small fragments of cells. The smallest cellular elements of blood. Formed in bone marrow. Life span of a thrombocyte is short – five to nine days.

Responsible for initiating the blood clotting process leading to the development of blood clots. These blood cells prevent blood loss from a blood vessel by: Gathering where a blood vessel is injured. Forming a plug at the injured site and releasing fibrinogen (a chemical) and converting this to fibrin (the net that holds the clot together).

The fluid portion of blood, plasma, contains different types of proteins and other soluble molecules. When a blood sample is separated, the formed elements account for 45% of blood and plasma makes up 55% of the total blood volume. Normally, more than 99% of the formed elements are cells named for their red colour (red blood cells). White blood cells and platelets comprise less than 1% of the formed elements (Figure 1.1). Between the plasma and erythrocytes is the buffy coat, consisting of white blood cells and platelets. See Figure 1.2 for the three formed elements of blood.

Figure 1.1 Appearance of centrifuged blood

Figure 1.2 Three formed elements of blood

The volume of blood is constant unless a person has physiological problems, for example, haemorrhage.

Properties of Blood

The average adult has a blood volume of approximately 5 L, accounting for 7–9% of the body’s weight. Men have 5–6 L and women 4–5 L of blood. Blood is thicker, denser and flows slower than water due to the red blood cells and plasma proteins. Plasma proteins, including albumin, fibrinogen, prothrombin and gamma globulins, make up around 8% of blood plasma in the body (Tortora and Derrickson 2017). These proteins help maintain water balance, affecting osmotic pressure, increasing blood viscosity and helping to maintain blood pressure. The plasma proteins, apart from the gamma globulins, are synthesised in the liver.

Blood has a high viscosity, resisting blood flow. Red blood cells and proteins contribute to the viscosity of blood, which ranges from 3.5 to 5.5 compared with 1.000 for water. Viscosity relates to stickiness of blood; normal viscosity of blood is low, allowing it to flow smoothly. However, the more red blood cells and plasma proteins in blood, the higher the viscosity and the slower the flow of blood. Normal blood varies in viscosity as it flows through the blood vessels; the viscosity decreases as it reaches the capillaries.

Plasma

Plasma is a straw-coloured aqueous solution containing plasma proteins, i.e. albumin, globulins and fibrinogen. It also contains inorganic ions regulating cell function, blood pH and osmotic pressure; these include sodium, potassium, chloride, phosphate, magnesium and calcium. Small amounts of nutrients, waste products, drugs, hormones and gases are also found in plasma. Figure 1.3 shows the composition of blood plasma along with the different types of formed elements in the blood.

Figure 1.3 Components of blood

Plasma is around 91.5% water with 8.5% solutes and most are proteins. Some of the proteins in blood plasma are found elsewhere in the body; those confined to blood are known as plasma proteins. Specific blood cells develop into cells producing gamma globulins, an important type of globulin; these are called antibodies or immunoglobulins, produced during specific immune responses. Other solutes in plasma include electrolytes, nutrients, regulatory substances, such as enzymes and hormones, gases as well as waste products such as urea, uric acid, creatinine, ammonia and bilirubin.

Formation of Blood Cells

Red bone marrow is the primary centre for haemopoiesis. Bone marrow is the soft fatty substance found in bone cavities. Within the bone marrow, all blood cells originate from a single type of unspecialised cell, a stem cell. When a stem cell divides, it first becomes an immature red blood cell, white blood cell or platelet‐producing cell. The immature cell divides, matures further and eventually becomes a mature red blood cell, white cell or platelet. Haemopoiesis describes the process by which the formed elements of blood develop (Figure 1.4).

Figure 1.4 Haemopoiesis

Blood Groups

Red blood cells define which blood group an individual belongs to. On the surface of red cells are markers called antigens. Apart from identical twins, each person has different antigens and these antigens are the key to identifying blood types and must be matched in transfusions to avoid serious complications. The structure for defining blood groups is known as the ABO system. If an individual has blood group A, then they have A antigens covering their red cells. Group B has B antigens on their red blood cells, while group O has neither antigens and group AB has both antigens (see Figure 1.5).

Figure 1.5 ABO blood groups

The ABO system also covers antibodies in the plasma, the body’s natural defence against foreign antigens, for example, blood group A has anti‐B in their plasma, B has anti‐A and so on. However, group AB has no antibodies and group O has both. If these antibodies find the wrong red blood cells, they attack them and destroy them. Transfusing the wrong blood to a patient can be fatal.

Blood Vessels

Blood vessels are part of the...

Produkt-Details

• Erscheint lt. Verlag: 12.12.2024
• Sprache: englisch
• Themenwelt: Medizin / Pharmazie
• Themenwelt: Naturwissenschaften ► Biologie
• ISBN-10: 1-394-25236-6 / 1394252366
• ISBN-13: 978-1-394-25236-7 / 9781394252367