Infectious Disease Flashcards
Name the two main physical barriers that prevent the invasion of pathogens in the first line of the body’s defence.
Skin and mucus.
What are the chemical barriers included in the first line of defence?
Acid from sweat on the skin, enzymes within saliva, mucus and tears - as well as stomach acid.
What is mucus?
A thin, clear liquid which consists of water, salts, and immune cells.
What is the function of mucus and how does it defend the body?
The viscous and sticky substance traps pathogenic cells and prevents them from entering the body. Immune cells also help to attack pathogens.
Where is mucus-secreting tissue located?
Nose, mouth, throat and lungs.
What is the complement system and how does it work?
The complement system consists of at least 20 complement proteins that circulate through the blood. They work by binding to bacterial cell membranes and creating pores in its cell wall. This allows water and salts to flood the bacterium and cause it to swell and burst. This is known as lysis. These proteins can also assist other immune functions such as phagocytosis and pathogen flagging.
What is another term used for ‘white blood cells?’
Leukocytes.
What are the four types of leukocytes?
Macrophage, Natural Killer (NK) cell, Eosinophil, and Neutrophil.
Which of the four leukocytes are phagocytic cells?
Macrophages and neutrophil.
What do phagocytes do?
Phagocytes remove pathogenic cells through a process known as phagocytosis, where the pathogen is engulfed and digested by the cell.
Describe the process of phagocytosis.
Pseudopodia (legs) of a pathogen surround and trap it. The pathogen(s) is then engulfed through endocytosis, where a VACUOLE is formed around it. The vacuole and a lysosome containing enzymes fuse together. This exposes the contained pathogen to the enzymes and other toxic compounds, killing it. Debris from the destroyed pathogen exit the phagocyte through exocytosis.
What is the organelle involved in phagocytosis?
Macrophages internalise pathogens through phagocytosis, entrapping them into organelles called phagosomes. Phagosomes then fuse with lysosomes to mature into phagolysosomes, acquiring an acidic and hydrolytic lumen that kills the pathogens.
Answer: Phagosomes or phagolysosomes
What is the role of Natural Killer Cells?
Circulating through the blood, the function of NK cells is to locate abnormal cells, which can be infected, cancerous, etc. They then either release cytokine chemicals to cause cell death by lysis, or apoptosis (programmed cell death).
What is the role of Eosinophils?
Eosinophils protect your body by assisting inflammation and fighting parasites, allergens, foreign bacteria, and outside organisms that phagocytic cells cannot.
What is the role of histamine and how does it help the body fight off pathogens?
In the presence of an injured and/or infected area, white blood cells will release histamine and cytokine proteins to said area. This stimulates the surrounding blood vessels and instigates dilation. This allows more fluid release to the area causing swelling. This allows more immune cells to flood the area and fight off pathogens. This is known as inflammation, which causes redness, pain, swelling, heat, and loss of function in the affected area.
What does pus consist of?
Pus, a thick opaque yellowish white substance, is formed usually as a product of inflammation due to invasion of the body by pathogens. It consists of dead/degenerating white blood cells/leukocytes, tissue debris, and living or dead microorganisms.
What is fever a result of?
A fever is a part of the nonspecific immune response, where the body instigates a temporary rise (constriction and contraction of vessels and muscles, trapping heat) in body temperature. This occurs when the body is attempting to kill off pathogens with heat.
Define an infectious and non-infectious disease.
An infectious disease is a deviation in cell biology and structure in an organism that is not a direct result of physical injury, caused by microorganisms. A non-infectious disease is the same thing, but is congenital and/or caused by genetics.
Define:
- Infection
- Host
- Pathogen
- The successful entry of a pathogen into the body. This does not necessarily mean disease will ensue, as the innate and adaptive immune system can still fight it off.
- The organism which allows the pathogen to cause infection within it.
- A microbe which is dangerous and can cause disease.
What is the role of the human microbiome?
The human microbiome, a personal bunch of helpful bacteria on and in the human body, helps kill external and potentially dangerous bacteria.
What are the 5 main causes of infectious disease?
- Bacteria (prokaryotic cells)
- Viruses (non-living)
- Protozoans (single-celled eukaryotes)
- Fungi (yeasts and moulds)
- Parasites (multicellular eukaryotic animals)
Describe how pathogens adhere and enter the cell.
- Exposure to pathogen
- Adherence of pathogen to skin, microbiome can kill it off at this point
- Invasion through openings in the body’s defence (openings in skin like cuts, through the mouth, nose, eyes, etc.)
- Infection in the cells and tissue fluid
- This can lead to toxicity and/or invasion of other tissue
- Which leads to tissue damage, causing disease
Describe the process through which bacteria and viruses cause disease.
Once bacteria and viruses successfully adhere and penetrate the host’s cell membrane, they go about similar processes to initiate disease. Bacteria tend to invade the membrane and replicate through asexual binary fission, which then causes tissue damage and disease. Viruses enter cells and hijack their biochemistry by releasing their RNA/DNA within, making host cells replicate the virus.
What are the factors that affect disease?
Disease can be influenced by:
- Type of pathogen, (Covid, influenza)
- Microbiome of host
- Age of host
- Season
- Lifestyle (stress, diet, air pollution, sleep, proximity to potential pathogens)
- Genome of host
- State of immune system
