circulatory system

• Blood is considered a connective tissue, the only fluid tissue in the body, full of fibrous proteins
• Blood is comprised of formed elements, which are blood cells, suspended in a fluid called plasma
• When blood is placed in a centrifuge, it separates into components: erythrocytes (red blood cells), yellowish plasma, and the buffy coat containing platelets and leukocytes (white blood cells)
• Plasma is a sticky fluid made mostly of water, containing proteins, nutrients, ions, gases, and hormones
• Blood is responsible for distributing substances around the body, including oxygen, nutrients, hormones, and waste products
• The most abundant plasma protein is albumin, followed by a variety of globulins that bind to certain molecules for transport
• Erythrocytes (red blood cells) are shaped like flattened discs with depressed centers, contain hemoglobin for oxygen transport, and are produced through erythropoiesis in the red bone marrow
• Hemoglobin is made of globin and heme groups with iron at the center, allowing for reversible binding of oxygen molecules
• Leukocytes (white blood cells) are part of the immune system, produced through leukopoiesis, and can be granulocytes (neutrophils, eosinophils, basophils) or agranulocytes (lymphocytes, monocytes)
• Platelets are fragments of megakaryocytes, essential for blood clotting during hemostasis, and are constantly regenerated every ten days
• Hemostasis involves vascular spasm, platelet plug formation, and coagulation to stop bleeding and repair damaged vessels
• Blood types in humans are A, B, AB, and O, determined by glycoproteins and glycolipids on red blood cell membranes
• Rh blood groups refer to Rh factors, where a person is either positive or negative, reported along with the ABO blood group
• Primary functions of blood:

  • Transportation of respiratory gases, nutrients, and wastes
  • Regulation of hormonal and temperature
  • Protection through clotting and immunity
• Characteristics of blood plasma:

  • Makes up 55% of blood volume
  • Contains plasma proteins like albumin, globulins, and fibrinogen
  • Regulatory mechanisms maintain plasma volume to maintain blood pressure
• Formed elements of blood and their functions:

  • Erythrocytes (red blood cells): carry oxygen, lack nuclei and mitochondria, have a 120-day lifespan
  • Leukocytes (white blood cells): have nuclei and mitochondria, involved in immunity
  • Platelets (thrombocytes): help clot blood, release serotonin for vasoconstriction
• Structure and function of red blood cells:

  • Flattened, biconcave discs
  • Carry oxygen through hemoglobin
  • Anemia can occur due to low hemoglobin or RBC count
• ABO and Rh blood typing:

  • ABO system: Type A, Type B, Type AB, Type O based on antigens on erythrocyte cell surfaces
  • Rh system: Rh-positive and Rh-negative blood types, risk of erythroblastosis fetalis
• Structure and function of white blood cells:

  • Have nuclei and mitochondria
  • Move in amoeboid fashion
  • Types include granular leukocytes and agranular leukocytes
• Steps involved in blood clotting:

  • Intact endothelium secretes prostacyclin and nitric oxide
  • Platelets play an essential role in clotting by releasing clotting factors
  • Thrombin reacts with fibrinogen to form fibrin and trap RBCs to form a clot
• Medical terms associated with blood:

  • Acidosis, serum, hematocrit, anemia, sickle cell, polycythemia, erythroblastosis fetalis, Rh factor, leukocytosis, leukopenia, phagocytosis, fibrinogen, thrombosis
• The process by which new blood cells are created is called hematopoiesis
• Billions of white blood cells, red blood cells, and platelets are produced every day to replace older cells that die during normal processes or because of illness
• Blood cells, including white cells, are made in the bone marrow, which is the soft spongy material in the center of the bones
• Blood cells are created from a group of master cells called stem cells, which also live within the bone marrow
• Stem cells have the ability to divide and produce all the different types of blood cells
• White blood cells are an important part of the body's immune system
• Granulocytes are a special group of white blood cells that play an important role in protecting the body against infections
• Neutrophils are a special class of granulocytes that can chase, engulf, and digest bacteria that cause infections
• Neutrophil development in the bone marrow takes approximately ten days
• Mature neutrophils are released into the blood where they survive for only three to six hours
• The bone marrow constantly produces large numbers of neutrophils to meet the body's needs
• The body makes natural proteins that can signal stem cells to start making cells that will eventually develop as neutrophils
• One important cytokine in the leukopoiesis process is called granulocyte colony-stimulating factor (G-CSF)
• The entire process of stem cells developing into mature neutrophils takes about ten days and includes two phases
• 1. CSF works on the cells in the bone marrow that eventually become neutrophils and signals them to start becoming neutrophils
• During the first phase, stem cells and their offspring can divide as they develop and mature, taking about six days
• Over another four to five days, the cells mature further but can no longer divide
• Mature neutrophils are finally released into the blood where they can fight bacteria and protect the body from infection
• Erythropoiesis is the scientific term for the production of red blood cells, also known as erythrocytes, which carry oxygen around the body