cardio blood

• The focus of this chapter is blood; the next two chapters will examine the heart and blood vessels, respectively
• Blood


  • Transports various substances
  • Helps regulate several life processes
  • Affords protection against disease
• Blood is as unique from one person to another as are skin, bone, and hair
• Blood


  • Contributes to homeostasis by transporting oxygen, carbon dioxide, nutrients, and hormones to and from body cells
  • Helps regulate body pH and temperature
  • Provides protection against disease through phagocytosis and production of antibodies
• Viscous


  Thick
• Oxygen content


  Bright red when saturated, dark red when unsaturated
• Blood volume

  1. 6 litres in average-sized adult male, 4-5 litres in average-sized adult female
• Hormones

  Aldosterone, antidiuretic hormone, atrial natriuretic peptide regulate water excretion in urine
• Withdrawing blood


  1. Venipuncture

  2. Finger/heel stick

  3. Arterial stick
• Blood plasma


  Watery liquid extracellular matrix that contains dissolved substances
• Formed elements


  Cells and cell fragments
• Blood is about 45% formed elements and 55% blood plasma
• Formed elements


  • Red blood cells
  • White blood cells
  • Platelets

  
• Hematocrit


  Percentage of total blood volume occupied by red blood cells

  
• Testosterone


  Stimulates synthesis of erythropoietin, which stimulates production of red blood cells
• Plasma proteins

  Albumins, globulins, fibrinogen
• Plasma solutes


  • Electrolytes
  • Nutrients
  • Regulatory substances
  • Gases
  • Waste products
• Waste products

  • Urea
  • Uric acid
  • Creatine
  • Creatinine
  • Bilirubin
  • Ammonia
• Most are breakdown products of protein metabolism that are carried by the blood to organs of excretion
• Formed elements of the blood


  • They last only hours, days, or weeks, and must be replaced continually
  • Negative feedback systems regulate the total number of RBCs and platelets in circulation, and their numbers normally remain steady
  • The abundance of the different types of WBCs varies in response to challenges by invading pathogens and other foreign antigens
• Hemopoiesis (blood cell production)


  1. Occurs first in the yolk sac of an embryo and later in the liver, spleen, thymus, and lymph nodes of a fetus

  2. Red bone marrow becomes the primary site of hemopoiesis in the last 3 months before birth, and continues as the source of blood cells after birth and throughout life
• Red bone marrow


  • It is a highly vascularized connective tissue located in the microscopic spaces between trabeculae of spongy bone tissue
  • About 0.05–0.1% of red bone marrow cells are pluripotent stem cells (hemocytoblasts) derived from mesenchyme
• In newborns, all bone marrow is red and thus active in blood cell production. As an individual ages, the rate of blood cell formation decreases and red bone marrow in the medullary cavity of long bones becomes inactive and is replaced by yellow bone marrow
• Under certain conditions, such as severe bleeding, yellow bone marrow can revert to red bone marrow as blood-forming stem cells from red bone marrow move into yellow bone marrow
• Pluripotent stem cells


  They have the capacity to develop into many different types of cells
• Myeloid stem cells


  They begin their development in red bone marrow and give rise to red blood cells, platelets, monocytes, neutrophils, eosinophils, basophils, and mast cells
• Lymphoid stem cells


  They begin their development in red bone marrow but complete it in lymphatic tissues, and give rise to lymphocytes and natural killer (NK) cells
• Progenitor cells


  They are no longer capable of reproducing themselves and are committed to giving rise to more specific elements of blood
• Precursor cells (blasts)


  They develop into the actual formed elements of blood over several cell divisions
• Erythropoietin (EPO)


  It is a hormone produced primarily by cells in the kidneys that increases the number of red blood cell precursors
• Thrombopoietin (TPO)


  It is a hormone produced by the liver that stimulates the formation of platelets from megakaryocytes
• Cytokines


  They are small glycoproteins that regulate development of different blood cell types
• Colony-stimulating factors (CSFs) and interleukins


  They are two important families of cytokines that stimulate white blood cell formation
• Red blood cells (RBCs)

  • They are highly specialized for their oxygen transport function
  • They lack a nucleus and mitochondria, so all their internal space is available for oxygen transport
  • Their biconcave disc shape facilitates gas diffusion
  • Each RBC contains about 280 million hemoglobin molecules
• Hemoglobin


  It is a protein consisting of four polypeptide chains and a heme group with an iron ion that can reversibly bind oxygen
• Hemoglobin also transports about 23% of the total carbon dioxide, a waste product of metabolism
• Hemoglobin


  Oxygen-carrying protein in red blood cells
• Oxygen transport in blood

  1. Hemoglobin binds oxygen in lungs

  2. Oxygen diffuses into interstitial fluid and cells

  3. Hemoglobin releases oxygen in tissues
• Carbon dioxide transport


  Hemoglobin transports about 23% of total carbon dioxide<|>Remaining carbon dioxide dissolved in plasma or carried as bicarbonate ions
• Carbon dioxide transport in blood


  1. Blood picks up carbon dioxide in tissues

  2. Carbon dioxide combines with amino acids in hemoglobin

  3. Carbon dioxide released from hemoglobin in lungs and exhaled