Answer:
Only when a microorganism has successfully established a site of infection in the host does disease occur, and little damage will be caused unless the agent is able to spread from the original site of infection or can secrete toxins that can spread to other parts of the body. Extracellular pathogens spread by direct extension of the focus of infection through the lymphatics or the bloodstream. Usually, spread by the bloodstream occurs only after the lymphatic system has been overwhelmed by the burden of infectious agent. Obligate intracellular pathogens must spread from cell to cell; they do so either by direct transmission from one cell to the next or by release into the extracellular fluid and reinfection of both adjacent and distant cells. Many common food poisoning organisms cause pathology without spreading into the tissues. They establish a site of infection on the epithelial surface in the lumen of the gut and cause no direct pathology themselves, but they secrete toxins that cause damage either in situ or after crossing the epithelial barrier and entering the circulation.
Most infectious agents show a significant degree of host specificity, causing disease only in one or a few related species. What determines host specificity for every agent is not known, but the requirement for attachment to a particular cell-surface molecule is one critical factor. As other interactions with host cells are also commonly needed to support replication, most pathogens have a limited host range. The molecular mechanisms of host specificity comprise an area of research known as molecular pathogenesis, which falls outside the scope of this book.
While most microorganisms are repelled by innate host defenses, an initial infection, once established, generally leads to perceptible disease followed by an effective host adaptive immune response. This is initiated in the local lymphoid tissue, in response to antigens presented by dendritic cells activated during the course of the innate immune response (Fig. 10.2, third and fourth panels). Antigen-specific effector T cells and antibody-secreting B cells are generated by clonal expansion and differentiation over the course of several days, during which time the induced responses of innate immunity continue to function. Eventually, antigen-specific T cells and then antibodies are released into the blood and recruited to the site of infection (Fig. 10.2, last panel). A cure involves the clearance of extracellular infectious particles by antibodies and the clearance of intracellular residues of infection through the actions of effector T cells.
Explanation:
if wrong correct me
"Complex Carbohydrates" are l<span>iving organisms break down polysaccharides into simple sugars. Complex carbohydrates are made up of sugar molecules. They are like strings that is long and complex chains. They can be found on foods like beans, whole grains, vegetables, and peas. They are converted into glucose in the body which serves as the source of energy of the body.</span>
Based on a soil texture triangle, the kind of soil present in the sample is loamy sand.
Loamy sand refers to soil comprising majorly of sand, silt, and a smaller portion of clay. Loamy is very fine sand comprising 50% or more of very fine sand. This soil is smooth to touch because of the predominance of extremely fine grains. All the kinds of loamy sands vary from sandy loams as loamy sands comprise more silt separates and smaller constituents of clay and sand.
Pine trees are part of the family Pinaceae. Sea urchins are from class <span>Echinoidea. These two organisms are very different in many ways. Pine trees have exposed seeds or sexually reproduce. They are coniferous. Sea urchins, well they don't produced seeds, they reproduce through external fertilization. Sea urchins are omnnivorous. </span>
Answer:
<u>frictional</u>
Explanation:
This scenario follows Newton's third law of motion which alludes to the fact that for every force or action exerted by a person on a body there is an equal and opposite reaction exerted back.
Because there is a limited frictional force (a force exerted by an object when an object moves across it) between
- the canoe and
- water surface (the opposite force/reaction)
Here, the paddle helps the boatman apply a force on the water, resulting in the opposite amount of force been sent back; pushing the boat forward.
