600 Flashcards
Blood is a liquid connective tissue
consists of cells and cell fragments surrounded by a liquid extracellular matrix (blood plasma)
Functions and Properties of Blood
- transports oxygen, carbon dioxide, nutrients, wastes, and hormones.
- regulate pH, body temperature, water content of cells.
- It provides protection by clotting and by combating toxins and microbes through certain phagocytic white blood cells or specialized blood plasma proteins
Functions and Properties of Blood
Physical characteristics of blood include a viscosity greater than that of water; a temperature of 38°C (100.4°F); and a pH of 7.35–7.45.
Blood constitutes about 8% of body weight, and its volume is 4–6 liters in adults.
Blood is about 55% blood plasma and 45% formed elements.
Functions and Properties of Blood
The hematocrit is the percentage of total blood volume occupied by red blood cells.
Blood plasma consists of 91.5% water and 8.5% solutes. Principal solutes include blood plasma proteins (albumins, globulins, fibrinogen), nutrients, vitamins, hormones, respiratory gases, electrolytes, and waste products.
The formed elements in blood include red blood cells (erythrocytes), white blood cells (leukocytes), and platelets.
Formation of Blood Cells
Hemopoiesis is the formation of blood cells from multipotent stem cells in red bone marrow.
Myeloid stem cells form RBCs, platelets, granulocytes, and monocytes. Lymphoid stem cells give rise to lymphocytes.
Several hemopoietic growth factors stimulate differentiation and proliferation of the various blood cells.
Red Blood Cells
Mature RBCs are biconcave discs that lack nuclei and contain hemoglobin.
The function of the hemoglobin in red blood cells is to transport oxygen and some carbon dioxide.
RBCs live about 120 days. A healthy male has about 5.4 million RBCs/μL of blood; a healthy female has about 4.8 million/μL.
Red Blood Cells
After phagocytosis of aged RBCs by macrophages, hemoglobin is recycled.
RBC formation, called erythropoiesis, occurs in adult red bone marrow of certain bones. It is stimulated by hypoxia, which stimulates the release of erythropoietin by the kidneys.
A reticulocyte count is a diagnostic test that indicates the rate of erythropoiesis.
White Blood Cells
WBCs are nucleated cells. The two principal types are granulocytes (neutrophils, eosinophils, and basophils) and agranulocytes (lymphocytes and monocytes).
The general function of WBCs is to combat inflammation and infection. Neutrophils and macrophages (which develop from monocytes) do so through phagocytosis.
Eosinophils combat the effects of histamine in allergic reactions, phagocytize antigen–antibody complexes, and combat parasitic worms. Basophils liberate heparin, histamine, and serotonin in allergic reactions that intensify the inflammatory response.
White Blood Cells
B lymphocytes, in response to the presence of foreign substances called antigens, differentiate into plasmocytes that produce antibodies. Antibodies attach to the antigens and render them harmless. This antigen–antibody response combats infection and provides immunity. T lymphocytes destroy foreign invaders directly. Natural killer cells attack infectious microbes and tumor cells.
Except for lymphocytes, which may live for years, WBCs usually live for only a few hours or a few days. Normal blood contains 5000–10,000 WBCs/μL.
Platelets
Platelets are disc-shaped cell fragments that splinter from megakaryocytes. Normal blood contains 150,000–400,000 platelets/μL.
Platelets help stop blood loss from damaged blood vessels by forming a platelet plug.
Stem Cell Transplants from Bone Marrow and Cord Blood
Bone marrow transplants involve removal of red bone marrow as a source of stem cells from the iliac crest.
In a cord-blood transplant, stem cells from the placenta are removed from the umbilical cord.
Cord-blood transplants have several advantages over bone marrow transplants.
Hemostasis
Hemostasis refers to the stoppage of bleeding.
It involves vascular spasm, platelet plug formation, and blood clotting (coagulation).
In vascular spasm, the smooth muscle of a blood vessel wall contracts, which slows blood loss.
Platelet plug formation involves the aggregation of platelets to stop bleeding.
Hemostasis
A clot is a network of insoluble protein fibers (fibrin) in which formed elements of blood are trapped.
The chemicals involved in clotting are known as clotting factors.
Blood clotting involves a cascade of reactions that may be divided into three stages: formation of prothrombinase, conversion of prothrombin into thrombin, and conversion of fibrinogen into fibrin.
Hemostasis
Clotting is initiated by the interplay of the extrinsic and intrinsic pathways of blood clotting.
Normal coagulation requires vitamin K and is followed by clot retraction (tightening of the clot) and ultimately fibrinolysis (dissolution of the clot).
Clotting in an unbroken blood vessel is called thrombosis. A thrombus that moves from its site of origin is called an embolus.
Blood Groups and Blood Types
ABO and Rh blood groups are genetically determined and based on antigen–antibody responses.
In the ABO blood group, the presence or absence of A and B antigens on the surface of RBCs determines blood type.
In the Rh system, individuals whose RBCs have Rh antigens are classified as Rh+; those who lack the antigen are Rh−.
Hemolytic disease of the newborn (HDN) can occur when an Rh− mother is pregnant with an Rh+ fetus.
Before blood is transfused, a recipient’s blood is typed and then either cross-matched to potential donor blood or screened for the presence of antibodies.
Anatomy of the Heart
The heart is located in the mediastinum; two-thirds sits on the left. Its apex is the pointed, inferior part. its base is the broad, superior part.
The pericardium is the membrane that surrounds and protects the heart; it consists of an outer fibrous layer and an inner serous pericardium.
this is composed of a parietal layer and a visceral layer. Between the parietal and visceral layers of the serous pericardium is the pericardial cavity, a potential space filled with a lubricating fluid
Anatomy of the Heart
Three layers make up the wall of the heart
-epicardium
-myocardium
-endocardium
The epicardium consists of mesothelium and connective tissue, the myocardium is composed of cardiac muscle tissue, and the endocardium consists of endothelium and connective tissue.
Anatomy of the Heart
The right atrium receives blood from the superior and inferior vena cava, and coronary sinus. It is separated from the left atrium by the interatrial septum, which contains the fossa ovalis. Blood exits the right atrium through the right atrioventricular valve.
The right ventricle receives blood from the right atrium. Separated from the left ventricle by the interventricular septum, it pumps blood through the pulmonary valve into the pulmonary trunk.
Anatomy of the Heart
Oxygenated blood enters the left atrium from the pulmonary veins and exits through the left atrioventricular valve.
The left ventricle pumps oxygenated blood through the aortic valve into the aorta.
The thickness of the myocardium of the four chambers varies according to the chamber’s function. The left ventricle, with the highest workload, has the thickest wall.
The fibrous skeleton of the heart is dense connective tissue surrounding and supporting the heart valves.
Anatomy of the Heart
The heart chambers include two superior chambers
-right and left atria
two inferior chambers
-the right and left ventricles
External features of the heart include the auricles, the coronary sulcus between the atria and ventricles, and the anterior and posterior sulci between the ventricles on the anterior and posterior surfaces of the heart, respectively.
Heart Valves and Circulation of Blood
Heart valves prevent backflow. The atrioventricular (AV) valves, lie between atria and ventricles
- the right AV is the tricuspid valve
- the left AV is the bicuspid or mitrial valve
- The semilunar (SL) valves are the aortic valve, at the entrance to the aorta
- the pulmonary valve, at the entrance to the pulmonary trunk.
The left side of the heart is the pump for systemic circulation (to the body)
-The left ventricle ejects blood into the aorta, and blood then flows into systemic arteries, arterioles, capillaries, venules, and veins, which carry it back to the right atrium.
Heart Valves and Circulation of Blood
The right side of the heart is the pump for pulmonary circulation
-The right ventricle ejects blood into the pulmonary trunk, and blood then flows into pulmonary arteries, pulmonary capillaries, and pulmonary veins, which carry it back to the left atrium.
The coronary circulation provides blood flow to the myocardium. Its main arteries are the left and right coronary arteries; its main veins are the cardiac veins and the coronary sinus.
Cardiac Muscle Tissue and the Cardiac Conduction System
- Cardiac muscle fibers usually contain a single centrally located nucleus.
- cardiac muscle fibers have
- more and larger mitochondria
- smaller sarcoplasmic reticulum
- wider T tubules located at Z discs.
- Cardiac muscle fibers are connected end-to-end via intercalated discs
- Desmosomes in the discs provide strength, and gap junctions allow muscle action potentials to conduct from one muscle fiber to its neighbors.
Cardiac Muscle Tissue and the Cardiac Conduction System
-Autorhythmic fibers spontaneously depolarize and generate action potentials.
- Components of the conduction system are the
- sinuatrial (SA) node,
- atrioventricular (AV) node,
- atrioventricular (AV) bundle,
- bundle branches
- subendocardial conducting network
Cardiac Muscle Tissue and the Cardiac Conduction System
Phases of an action potential are rapid depolarization, a long plateau, and repolarization.
Cardiac muscle tissue has a long refractory period, which prevents tetanus.
Cardiac Muscle Tissue and the Cardiac Conduction System
A normal ECG consists of a P wave (atrial depolarization), a QRS complex (onset of ventricular depolarization), and a T wave (ventricular repolarization).
The P–Q interval represents the conduction time from the beginning of atrial excitation to the beginning of ventricular excitation. The S–T segment represents the time when ventricular contractile fibers are fully depolarized.
The Cardiac Cycle-The phases of the cardiac cycle are (a) atrial systole, (b) ventricular systole, and (c) relaxation period.
A cardiac cycle consists of the systole (contraction) and diastole (relaxation) of both atria, plus the systole and diastole of both ventricles. With an average heartbeat of 75 beats/min, a complete cardiac cycle requires 0.8 sec.
S1, the first heart sound (lubb), is caused by blood turbulence associated with the closing of the atrioventricular valves.
S2, the second sound (dupp), is caused by blood turbulence associated with the closing of semilunar valves.
Cardiac Output- (CO) is the amount of blood ejected per minute
- stroke volume (SV) × heart rate (HR)
- Stroke volume is the amount of blood ejected by a ventricle during each systole.
- Cardiac reserve is the difference between a person’s maximum CO and his or her CO at rest.
Cardiac Output
Stroke volume is related to
-preload, contractility and afterload
Cardiac Output
Nervous control of the cardiovascular system originates in the medulla oblongata.
Sympathetic impulses increase heart rate and force of contraction; parasympathetic impulses decrease heart rate.
Heart rate is affected by hormones (epinephrine, norepinephrine, thyroid hormones) and ions (Na+, K+, Ca2+)
age, gender, physical fitness, and body temperature also affect HR
Frank–Starling law
greater preload (stretching) increases their force of contraction until the stretching becomes excessive.
