Lymph from the intestine that carries absorbed dietary fat has a milky appearance and is called chyle.
Missing Word
chyle
Chyle is the milky, lipid-rich lymph formed in lacteals after fat absorption. It flows toward the cisterna chyli and thoracic duct before entering the blood.
Category: Lymphatic Anatomy
Question 2
When the pharyngeal tonsil becomes enlarged, it is commonly called the adenoid.
Missing Word
adenoid
The adenoid is the name for the pharyngeal tonsil when it is swollen. This tonsil sits on the posterior wall of the nasopharynx and helps defend against inhaled pathogens.
Category: Lymphatic Anatomy
Question 3
The tonsils have deep surface pits called crypts that trap bacteria and draw them into the lymphoid tissue.
Missing Word
crypts
Tonsillar crypts are invaginations of the tonsil surface that collect bacteria and particles. Trapping them there exposes the material to lymphocytes and helps build immunity to oral and inhaled pathogens.
Category: Lymphatic Anatomy
Question 4
After a macrophage engulfs a bacterium, the phagosome fuses with a lysosome, an organelle whose digestive enzymes destroy the microbe.
Missing Word
lysosome
A lysosome is a membrane-bound organelle filled with digestive enzymes. Its fusion with the phagosome delivers those enzymes to the engulfed pathogen, killing and breaking it down.
Category: Innate Defenses
Question 5
Natural killer cells release perforin, a protein that inserts into the target cell membrane and forms pores through which granzymes enter.
Missing Word
perforin
Perforin is a pore-forming protein stored in the granules of natural killer cells and cytotoxic T cells. The pores it creates let granzymes into the target cell, where they trigger apoptosis.
Category: Innate Defenses
Question 6
Movement of a cell along a gradient of attracting chemicals, as when neutrophils home in on an infection site, is called chemotaxis.
Missing Word
chemotaxis
Chemotaxis is directed cell movement toward a chemical attractant. Signals such as complement fragments and chemokines guide phagocytes to the site of infection or injury.
Category: Innate Defenses
Question 7
When an activated lymphocyte divides repeatedly, all of its genetically identical descendants with the same receptor make up a clone.
Missing Word
clone
A clone is a population of cells descended from one parent cell and sharing its antigen receptor. Expanding the selected clone multiplies the cells able to fight that specific antigen.
Category: T Lymphocytes
Question 8
Cytotoxic T cells kill infected target cells mainly by inducing apoptosis, a form of programmed cell death.
Missing Word
apoptosis
Apoptosis is programmed cell death in which the cell dismantles itself in an orderly way. Cytotoxic T cells trigger it through Fas ligand or perforin and granzymes, destroying infected cells without spilling their contents.
Category: T Lymphocytes
Question 9
IgA is the antibody class secreted as a dimer into tears, saliva, mucus and breast milk.
Missing Word
IgA
IgA exists as a monomer in blood but is secreted as a dimer onto mucosal surfaces. It is the main antibody protecting body surfaces and gives breastfed infants passive protection.
Category: Antibodies
Question 10
Along with IgM, IgD serves as a surface antigen receptor on mature naive B cells.
Missing Word
IgD
IgD is an antibody class found mainly on the surface of naive B cells, where it acts with IgM as the B cell receptor. Very little of it circulates in the blood.
Category: Antibodies
Question 11
Eosinophils and IgE-driven mast cell responses are major defenses against parasitic worms known as helminths.
Missing Word
helminths
Helminths are multicellular parasitic worms too large to be engulfed by phagocytes. The body attacks them with eosinophil granule proteins and mast cell degranulation, which may also help flush them from the gut.
Category: Pathogen Responses
Question 12
The point in an infection such as HIV when virus-specific antibodies first become detectable in the blood is called seroconversion.
Missing Word
seroconversion
Seroconversion is the appearance of antibodies against a pathogen in the serum. In HIV infection, virus levels fall as antibodies rise, but the antibodies cannot clear the virus completely.
Category: Pathogen Responses
Question 13
A severe systemic allergic reaction marked by a sudden drop in blood pressure and constriction of the airways is called anaphylaxis.
Missing Word
anaphylaxis
Anaphylaxis is a body-wide type I hypersensitivity caused by widespread mast cell degranulation. It can be fatal quickly without treatment, and epinephrine is the drug that counteracts it.
Category: Immune Disorders
Question 14
In type 1 diabetes, the immune system destroys the insulin-producing beta cells of the pancreas.
Missing Word
pancreas
The pancreas contains the islets whose beta cells make insulin. In type 1 diabetes, autoimmune attack on these cells leaves the body unable to produce enough insulin.
Category: Immune Disorders
Question 15
The three stages of the immune response to a tumor are elimination, equilibrium and escape, when resistant cancer cells grow unchecked.
Missing Word
escape
Escape is the final stage, reached when cancer cells that have mutated or stopped expressing target antigens evade immune attack. The surviving subpopulation then grows and the disease progresses.
Category: Cancer Immunology