Work 1: Cardiovascular system: Blood.

• Blood is a connective tissue made up of cellular elements and an extracellular matrix
• Formed elements in blood include red blood cells (RBCs), white blood cells (WBCs), and platelets
• Plasma is the fluid component of blood, mostly water, that suspends the formed elements and enables circulation within the cardiovascular system
• Functions of blood:

  • Deliver oxygen and nutrients to body cells
  • Remove wastes from body cells
  • Defense
  • Distribution of heat
  • Maintenance of homeostasis
• Composition of blood:

  • Cellular elements: erythrocytes, leukocytes, platelets
  • Plasma is the fluid in which formed elements are suspended
  • Plasma is the lightest component of blood, floating at the top of a tube separated from erythrocytes by a buffy coat of leukocytes and platelets
• Physical characteristics of blood:

  • Color: Scarlet for oxygen-rich blood, dark red for oxygen-poor blood
  • Temperature: 38.0°C (104.7°F)
  • Volume: Females 4-5 L, males 5-6 L
  • Viscosity: Thicker and more viscous than water
  • Total body weight: Makes up 8%
  • pH: 7.35-7.45
• Production of formed elements:

  • Lifespan of formed elements is brief
  • Body continuously forms new blood cells and platelets through hemopoiesis
  • Hemopoiesis occurs in various tissues before and after birth
  • Sites of hemopoiesis include red bone marrow, liver, spleen, lymphatic tissue, and eventually in adult bones
• Differentiation of formed elements from stem cells:

  • Totipotent cells can form all cell types in the body
  • Pluripotent cells can give rise to all cell types in the body
  • Multipotent cells can develop into more than one cell type
• Erythrocytes:

  • Most common formed element in blood
  • Structure: biconcave discs
  • Function: Facilitate gas exchange
  • Hemoglobin: Large molecule made of proteins and iron
• Leukocytes:

  • White blood cells that protect the body against disease
  • Classified as granulocytes and agranulocytes
  • Function: Defense against microorganisms and mutated cells, clean up debris
• Platelets:

  • Function in blood clotting
• Platelets are not cells but fragments of the cytoplasm of a cell called a megakaryocyte that is surrounded by a plasma membrane
• Megakaryocytes are essential for the repair of blood vessels when damage has occurred
• Megakaryocytes provide growth factors for healing and repair
• Platelets are derived from cells called megakaryocytes
• Thrombocytosis is a condition with too many platelets, which may trigger the formation of unwanted blood clots (thrombosis)
• Thrombocytopenia is a condition with an insufficient number of platelets, leading to improper blood clotting and excessive bleeding
• Platelets play a key role in hemostasis, which is the process of sealing a ruptured blood vessel and preventing further blood loss
• Hemostasis involves three steps: vascular spasm, the formation of a platelet plug, and coagulation (blood clotting)
• Failure in any of these steps can result in hemorrhage (excessive bleeding)
• Coagulation factors are made up of plasma proteins, except for factor IV (calcium) and factor III (thromboplastin)
• Coagulation factors are produced in the liver and activated in a chain reaction
• Factors are activated in a chain reaction, with each one activating the next factor in the chain
• Hemophilia is the inadequate production of functional amounts of one or more clotting factors
• Thrombosis is a condition characterized by excessive numbers of platelets, increasing the risk for excessive clot formation
• A thrombus is an aggregation of platelets, erythrocytes, and even WBCs typically trapped within a mass of fibrin strands
• An embolus is a portion of a thrombus that breaks free and enters the circulation
• An embolus can cause medical emergencies like a heart attack, stroke, or pulmonary embolism
• Blood groups are determined by the presence or absence of specific marker molecules on the plasma membranes of erythrocytes
• Antigens trigger a defensive response from the immune system
• Antibodies are produced by B lymphocytes and cause agglutination of erythrocytes
• The ABO blood group designates the presence or absence of antigens A and B on erythrocyte membrane surfaces
• People with A antigens are blood type A, those with B antigens are blood type B, both A and B antigens are blood type AB, and those with neither are blood type O
• The Rh blood group is classified by the presence or absence of the Rh D antigen
• Rh positive individuals have the Rh D antigen, while Rh negative individuals lack it
• Antibodies to the Rh antigen are produced in Rh negative individuals after exposure to the antigen
• Hemolytic disease of the newborn (HDN) occurs when an Rh negative mother is exposed to Rh positive cells from the fetus
• Anti-Rh antibodies can cross the placenta and destroy fetal RBCs in subsequent pregnancies