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• Cardiovascular system


  • Blood vessels: carry blood to and from all regions of the body
  • Heart: pumps the blood
  • Closed circuit known as the circulatory system
• Functions of the cardiovascular system

  • Provides tissues with oxygen and nutrients
  • Carries away carbon dioxide and waste products
• Lymphatic system


  • Lymph vessels: roughly parallel the blood vessels
  • Lymph nodes: cluster at body sites such as the groin, neck, armpit, and intestines
  • Spleen
• Function of the lymphatic system


  • Major source of immune cells and fluids
  • One-way passage: collects fluid from tissues, filters out impurities, and returns it to the cardiovascular system
• Heart


  • Fist-sized muscular organ that pumps blood throughout the body
  • Atria: upper chambers
  • Ventricles: lower chambers
  • Pericardium: fibrous covering of the heart and occasional site of infection
  • Wall of the heart has three layers: Epicardium (outermost), Myocardium, Endocardium (innermost) covers the valves of the heart; common target of microbial infection
• Blood vessels


  • Arteries: carry oxygenated blood away from the heart under relatively high pressure; branch into arterioles
  • Veins: begin as venules in the periphery of the body; carry deoxygenated blood back to the heart
  • Capillaries: smallest blood vessels, connect arterioles to venules, and have only one layer of endothelium
  • Innermost layer: composed of endothelium; smooth surface encourages the flow of cells and platelets
  • Middle layer: composed of connective tissue and muscle fibers
  • Outer layer: thin layer of connective tissue
• Cardiovascular system


  • Highly protected from microbial infection
  • Microbes that successfully invade the system have access to every part of the body
  • Every system has the potential to be affected
  • Bloodstream infections are considered systemic infections
• Defenses of the cardiovascular and lymphatic systems

  • 5,000 to 10,000 WBC per milliliter of blood
  • Lymphocytes: specific immunity
  • Phagocytes: critical to specific and nonspecific response
• Medical conditions involving the blood

  • Viremia: presence of viruses in the blood
  • Fungemia: presence of fungi in the blood
  • Bacteremia: presence of bacteria in the blood
  • Septicemia (sepsis): bacteria growing and flourishing in the blood
  • Septic shock: cascading immune responses to septicemia, resulting in decreased blood pressure
• The cardiovascular and lymphatic systems are "closed" systems with no normal access to the external environment
• In a healthy state, no microorganisms colonize either the lymphatic or cardiovascular systems
• Recent studies from the HMP have suggested that the bloodstream is not completely sterile, even in periods of apparent health
• These low-level microbial "infections" may contribute to diseases for which no etiology has been found or for conditions thought to be noninfectious
• Defenses of the cardiovascular system

  Blood-borne components of nonspecific and specific immunity—including phagocytosis, specific immunity
• Defenses of the lymphatic system

  Numerous immune defenses reside here
• Malaria has been one of the greatest afflictions throughout human history
• Malaria threatens 40% of the world's population every year
• Malaria


  • Dominant protozoan disease
  • Name comes from the Italian words mal ("bad") and aria ("air")
• Malaria signs and symptoms

  • 10- to 16-day incubation period; first symptoms are: Malaise, fatigue, vague aches, and nausea with or without diarrhea, followed by chills, fever, and sweating
  • Symptoms occur at 48- or 72-hour intervals, as the result of synchronous red-blood-cell rupture
  • Falciparum malaria: persistent fever, cough, and weakness for weeks without relief
  • Complications: Hemolytic anemia from lysed red blood cells, Organ enlargement and rupture due to cellular debris that accumulates in the spleen, liver, and kidneys
• Cerebral malaria


  • Small blood vessels in the brain become obstructed due to RBCs adhering to blood vessel walls
  • Decrease in oxygen in the brain can cause coma and death
• Malaria caused by Plasmodium vivax and P. ovale are subject to relapses because some infected liver cells harbor dormant protozoans for up to 5 years
• Plasmodium species


  • Protozoans in the sporozoan group
  • Contains more than 200 species but only five infect humans: P. malariae, P. vivax, P. knowlesi, P. ovale, and P. falciparum, each showing variations in pattern and severity of disease
• Development of the malarial parasite

  1. Asexual phase: carried out in the human

  2. Sexual phase: carried out in the mosquito
• Malaria pathogenesis and virulence factors

  • Invasion of merozoites into RBCs leads to the release of fever-inducing chemicals into the bloodstream
  • Chills and fevers often occur in a cyclic pattern
  • Plasmodium also metabolizes glucose at a very high rate, leading to hypoglycemia in the human host
  • Damage to RBCs results in anemia
  • Accumulation of malarial products in the liver and the immune stimulation in the spleen can lead to enlargement of these organs
  • Individual protozoa can express different surface antigens, making it difficult for the host immune system to battle
• Malaria transmission and epidemiology

  • Primarily spread by the female Anopheles mosquito
  • Malaria was once distributed throughout the world
  • Mosquito control in temperate areas has restricted it to a belt around the equator
  • 200 million new cases are still reported each year, 90% of them in Africa
  • Most frequent victims are children and young adults; 500,000 to 1 million die annually
  • Total case rate in the U.S. is 1,000 to 2,000 new cases a year
  • Most occur in immigrants or travelers to endemic areas
• There were an estimated 619,000 malaria deaths globally in 2021 compared to 625,000 in the first year of the pandemic. In 2019, before the pandemic struck, the number of deaths stood at 568,000. Malaria cases continued to rise between 2020 and 2021, but at a slower rate than in the period 2019 to 2020.
• The global tally of malaria cases reached 247 million in 2021 compared to 245 million in 2020 and 232 million in 2019.
• COVID-19 deaths: 6,881,955 globally, 1,123,836 in the US
• Malaria prevention


  • Prevention is attempted through long-term mosquito abatement and human chemoprophylaxis
  • Scientists have attempted introducing sterile male mosquitoes into endemic areas to reduce mosquito populations
  • Humans reduce their risk by: Using netting, screens, and repellants, Remaining indoors at night, Taking weekly doses of antimalarial drugs
• Malaria vaccine


  • The best protection would come from a malaria vaccine
  • In 2016, a major breakthrough in vaccine research occurred with development of a vaccine called RTS,S
  • Effective against P. falciparum (the most deadly and most common strain in Africa)
  • Found to be highly effective in children
  • Beginning in 2018, it will be used in pilot vaccination programs in sub-Saharan Africa
• Malaria treatment


  • Quinine has long been a mainstay of malaria treatment
  • Chloroquine, the least toxic type, is used in nonresistant forms of the disease
  • Malarial protozoan has developed resistance to nearly every drug used for its treatment
  • Artemisinin, a plant compound, has been most effective
  • It should be used in combination with other drugs to prevent resistance development
• Sickle cell anemia and malaria

  • 2 traits for normal hemoglobin - malaria
  • 2 traits for sickle cell anemia - SCA die of SCA
  • One of each trait - don't have SCA and you're not going to die of malaria
  • Heterozygote
• HIV infection and AIDS signs and symptoms

  • Symptoms of HIV are directly tied to two things: Level of virus in the blood, Level of T cells in the blood
  • Initial symptoms: Fatigue, diarrhea, weight loss, and neurological changes
  • Opportunistic infections or neoplasms (cancer)
  • Other disease-related symptoms appear to accompany severe immune deregulation, hormone imbalances, and metabolic disturbances
  • Pronounced wasting of body mass: consequence of weight loss, diarrhea, and poor nutrient absorption
  • The most virulent complications are neurological: Lesions occur in the brain, meninges, spinal column, and peripheral nerves
  • Patients with nervous system involvement show some degree of withdrawal, persistent memory loss, spasticity, sensory loss, and progressive AIDS dementia
• Dynamics of virus antigen, antibody, T cells in circulation


  See diagram
• AIDS-defining illnesses


  • Skin and/or Mucous Membranes (Includes Eyes), Nervous System, Cardiovascular and Lymphatic System or Multiple Organ Systems, Respiratory Tract, Gastrointestinal Tract, Genitourinary and/or Reproductive Tract
• HIV


  • Retrovirus in the genus Lentivirus
  • Many retroviruses have the potential to cause cancer
  • They produce dire, often fatal, diseases and are capable of altering the host's DNA
  • Contain reverse transcriptase (RT): Catalyzes the replication of double-stranded DNA from single-stranded RNA
  • Retroviruses can permanently integrate viral genes into the host genome that is passed on to progeny cells
  • Some retroviruses also transform cells (make them malignant) and regulate certain host genes
• HIV structure


  • Outermost layer is a lipid envelope
  • Membrane glycoprotein spikes mediate viral adsorption to the host cell
  • Can only infect host cells that display a combination receptor consisting of the CD4 marker plus the coreceptor CCR-5
  • Virus uses these to gain entrance to several types of leukocytes and tissue cells
• HIV infection and AIDS pathogenesis and virulence factors

  • HIV enters a mucous membrane or the skin and travels to dendritic cells beneath the epithelium
  • Virus grows inside the dendritic cell and is shed without killing the cell
  • Virus is amplified by macrophages in the skin, lymph organs, bone marrow, and blood
  • It infects and destroys helper T4 and CD4 lymphocytes, monocytes, macrophages, and B lymphocytes
  • Virus docks to host cell surface receptors and induces cell fusion, creating syncytia
• Multiplication cycle of HIV


  See diagram
• HIV infection and AIDS transmission

  • HIV is mainly transmitted through sexual intercourse or transfer of blood or blood products
  • Babies can be infected before or during birth, or through breast feeding
  • Mode of transmission is similar to the hepatitis B virus, except HIV does not survive long outside the host and is more sensitive to disinfectants
  • Virus is not transmitted through saliva
  • Health care workers should be aware of the fluids they may come in contact with during childbirth or invasive procedures that can transmit the virus: Amniotic fluid, Synovial fluid, Spinal fluid