A&P Cardiovascular System: Heart

Cardiovascular System

The cardiovascular system is a circulating transport system consisting of a pump (the heart), a conducting system (blood vessels), and a fluid medium (blood).

Functions of Blood — Transport

Blood transports oxygen, carbon dioxide, nutrients, hormones, and waste products throughout the body.

Functions of Blood — Regulation

Blood helps maintain appropriate body temperature, normal pH of body tissues, adequate fluid volume, and proper salt and protein content in the blood.

Functions of Blood — Protection

Blood protects the body by housing and distributing immune system components, helping prevent infection, and containing clotting agents that prevent excessive fluid loss.

Blood

Blood is a specialized type of connective tissue consisting of a fluid matrix called plasma and formed elements consisting of red blood cells, white blood cells, and platelets.

Characteristics of Blood

Blood is a viscous liquid, about five times more viscous than water, with a slightly alkaline pH of 7.35–7.45.

Normal Blood Volume in Males

Approximately 5–6 liters of blood.

Normal Blood Volume in Females

Approximately 4–5 liters of blood.

Why Do Males Typically Have More Blood?

The difference is mainly related to larger average body size in males, and testosterone also stimulates blood cell formation.

Normovolemic

Having a normal blood volume.

Hypovolemic

Having a blood volume that is lower than normal.

Hypervolemic

Having a blood volume that is higher than normal.

Blood pH

Normal blood pH is slightly alkaline, ranging from approximately 7.35 to 7.45.

Venous Blood

Venous blood in the systemic circulation is more acidic than arterial blood.

Components of Blood

Blood consists of plasma and formed elements. Formed elements include erythrocytes, leukocytes, and platelets.

Plasma

The fluid matrix of blood. It makes up approximately 50–60% of blood volume and contains water, dissolved plasma proteins, ions, gases, wastes, and nutrients.

Formed Elements

The cellular components of blood: red blood cells (erythrocytes), white blood cells (leukocytes), and platelets.

Centrifugation of Blood

Centrifugation separates blood into erythrocytes, the buffy coat, and plasma based on density.

Erythrocytes in Centrifuged Blood

Erythrocytes make up approximately 45% of total blood volume in a centrifuged blood sample.

Hematocrit

The percentage of whole blood volume occupied by red blood cells. It is also called packed cell volume (PCV) or volume of packed red cells (VPRC).

Buffy Coat

The thin layer between erythrocytes and plasma containing leukocytes and platelets. It makes up less than 1% of blood volume.

Plasma in Centrifuged Blood

Plasma makes up approximately 55% of total blood volume and is the fluid layer containing ions, dissolved proteins, and nutrients.

Major Components of Plasma

Plasma contains water, dissolved plasma proteins, ions, gases, wastes, and nutrients.

Three Major Classes of Plasma Proteins

The three major plasma protein classes are albumins (about 60%), globulins (about 35%), and fibrinogen (about 4%).

Albumins

Albumins make up approximately 60% of plasma proteins. They help retain water in the circulatory system, contribute to osmotic pressure, act as pH buffers, and transport substances such as fatty acids and hormones.

Where Are Albumins Produced?

Albumins are produced by the liver.

Albumin and Osmotic Pressure

Albumin helps hold water within the circulatory system by contributing to the osmotic pressure of blood.

Albumin as a Transport Protein

Albumin transports fatty acids, thyroid hormones, and steroid hormones.

Globulins

Globulins make up approximately 35% of plasma proteins and include immunoglobulins (antibodies) and transport globulins.

Immunoglobulins

Immunoglobulins are antibodies involved in immune defense. They are produced by plasma cells, which are white blood cells.

Transport Globulins

Transport globulins carry small molecules such as hormones, metals, fatty acids, cholesterol, and steroid hormones.

Transferrin

Transferrin is a transport protein that carries iron in the blood.

Ceruloplasmin

Ceruloplasmin is a transport protein associated with carrying copper.

Apolipoproteins

Apolipoproteins are transport proteins associated with fatty acids and cholesterol.

Where Are Transport Globulins Produced?

Transport globulins are produced by the liver.

Fibrinogen

Fibrinogen is the most numerous clotting protein in plasma. It is converted into long, sticky, insoluble strands of fibrin during blood clotting.

Where Is Fibrinogen Produced?

Fibrinogen is produced by the liver.

Serum

Serum is the liquid portion of a blood sample after fibrinogen has been converted into solid fibrin and removed.

Other Plasma Proteins

Other plasma proteins make up less than 1% and include specialized proteins such as enzymes, hormones, and prohormones.

Origin of Plasma Proteins

Approximately 90% of plasma proteins are made in the liver. Antibodies are made by plasma cells, and peptide hormones are made by endocrine organs.

Nonprotein Components of Plasma

Nonprotein plasma components include amino acids, nitrogenous wastes, nutrients, oxygen, carbon dioxide, and electrolytes.

Nitrogenous Compounds in Plasma

Plasma contains amino acids from dietary protein or tissue breakdown and nitrogenous wastes such as urea produced during catabolism.

Urea

Urea is a nitrogenous waste produced as a toxic end product of catabolism and is normally removed from the blood by the kidneys.

Plasma Nutrients

Plasma transports glucose, vitamins, fats, minerals, and other nutrients.

Plasma Electrolytes

Electrolytes are dissolved ions in plasma. Sodium (Na+) makes up approximately 90% of plasma cations.

Three Types of Formed Elements

The three formed elements are red blood cells (erythrocytes), white blood cells (leukocytes), and platelets.

Hemopoiesis

Hemopoiesis is the formation of blood cells, including erythrocytes, leukocytes, and platelets.

Hemocytoblast

A hemocytoblast is a blood-forming stem cell involved in the development of blood cells.

Early Hemopoiesis

Hemocytoblasts first form in blood islands of the yolk sac during early embryonic development, with the first appearance around the third week.

Hemanigioblast

A hemanigioblast is an embryonic cell population located near the developing aorta and heart that gives rise to endothelial stem cells and hemocytoblasts.