| Iron Intake and Recycling The typical daily diet of most Americans contains approximately 10 to 15 mg of iron. Sources of dietary iron include heme iron from meats and nonheme iron from whole grains and vegetables. Many processed foods, such as breakfast cereal, are fortified with iron. However, the normal individual absorbs only 5% to 15% of dietary iron, or about 1 to 2 mg daily. Females may absorb slightly more iron than males as they require more iron to replace that lost through menstruation and to meet the increased need for iron in pregnancy.Absorption of iron occurs through the mucosal cells in the duodenum (proximal small intestine). Dietary iron that is not absorbed is excreted in the feces. Intestinal absorption provides the means for regulating the amount of iron in the body.The amount of Iron absorbed is normally low because iron is well conserved within the body. Heme iron from senescent erythrocytes is cycled back into the iron pool and reused for incorporation into developing erythrocytes. Furthermore, iron is normally lost from the body only in very small amounts, primarily through desquamation of mucosal cells in the gastrointestinal tract and losses through body secretions, including urine, sweat and feces. Therefore, under normal conditions, very little dietary iron needs to be absorbed to maintain iron homeostasis.(3) | View Page |
| Regulation of Iron Equilibrium Regulation of iron equilibrium occurs mainly through the process of absorption. Iron is absorbed through the mucosal cells lining the duodenum. A variety of proteins are involved in this process. Hepcidin, an antimicrobial protein primarily produced in the liver, has been recently found to be a major (negative) regulator of dietary iron absorption by disrupting cellular iron transport in the intestine. Decreased levels of hepcidin are related to increased iron absorption into the bloodstream. Hepcidin is increased in response to iron overload and inflammation. (4)Additional proteins involved in iron metabolism include transferrin (Tf), transferrin receptor (TfR), ferroportin, HFE protein, hemojuvelin, and others. Their roles in iron absorption are complex and in some instances incompletely understood.Factors affecting iron absorption include: Tissue stores, e.g., decreased stored iron is associated with a decrease in hepcidin and increase in iron absorption. Rate of hematopoietic activity, e.g., an increased rate of erythropoiesis is associated with a decrease in hepcidin and an increase in iron absorption. Oxygen concentration in tissues, e.g., hypoxia decreases hepcidin and increases iron absorption, thereby promoting increased erythopoiesis. Dietary intake, including form of iron ingested, e.g., heme iron is more readily absorbed than non-heme forms of iron. Condition of GI tract mucosal cells Intraluminal factors, e.g. intestinal motility | View Page |
| HFE and Other Genes A hemochromatosis gene, HFE, was identified in 1996. Mutations in the HFE gene are found in the majority of patients diagnosed with hereditary hemochromatosis (HH). The locus for the gene is on the long arm of chromosome 6 where it codes for a membrane protein, HFE. The exact mechanism of the role of HFE protein in iron metabolism is incompletely understood. It is thought that HFE, along with a second protein, beta-2 microglobin, interacts with transferrin receptors (TfR) on cell membranes. This interaction supresses the affinity of transferrin for TfR, thus lowering the uptake of transferrin--and its attached iron--into the cell. Transferrin receptors have been found on the surface of a variety of cells, with the greatest concentration on cell membranes of intestinal cells, hepatocytes, and RBC precursors. In addition to HFE, HH is also associated with mutations in other genes involved in iron homeostasis, including hemojuvelin (HJV), TfR, hepcidin, and ferroportin. Hepcidin production is reduced in HH due to all of these genetic causes, with a resulting increase in iron absorption. Mutations in HFE are the most common cause of HH. | View Page |
| The infective stage for all of the intestinal amebae is the: | View Page |
| The intestinal amebae are primarily transmitted by: | View Page |
| Match each parasite listed here with its corresponding infective stage: | View Page |
| The ameba that lives in the gumline of the mouth is known as: | View Page |
| Which of these parasites may be contracted by swimming in infected water? | View Page |
| Which of the following parasites migrate either to or through the lungs in their corresponding life cycle? | View Page |
| The specimen of choice for the recovery of Entamoeba hartmanni is: | View Page |
| This intestinal parasite, which measures 5 µm, is usually not visible in samples processed using standard permanent stains. Special staining, as indicated by the coloring here, is helpful in its identification. | View Page |
| This intestinal parasite, found in stool, measures 170 µm by 63 µm. | View Page |
| This suspicious form was seen in a stool specimen and measures 33 µm by 28 µm. | View Page |
| This suspicious form was found in stool. | View Page |
| Which of the following parasites causes both intestinal and extraintestinal amebiasis? | View Page |
| A 20 year-old female was admitted into the hospital complaining of 10 to 15 bloody mucous stools per day, fever, gastrointestinal disturbances, abdominal pain, and nausea. The preliminary O & P report went out as "Probable Entamoeba histolytica trophozoites and cysts, confirmation pending." This patient is most likely suffering from: | View Page |
| Match each organism with its respective associated condition: | View Page |
| Which parasite listed here is capable of crossing the placenta and causing serious harm to fetus? | View Page |
| A 32 year old male was seen in the emergency room with gastrointestinal discomfort. Upon questioning the patient it was learned that he first began feeling ill after spending a day at the park where he swam and played volleyball barefooted. He first noticed a lesion on his foot. Later, he developed vague respiratory symptoms. Now his largest complaint is severe abdominal pain along with occasional vomiting. This patient is most likely suffering from: | View Page |
| This parasite and Trichomonas tenax are both considered as oral non-pathogens. | View Page |
| This suspicious form, found in stool, which measures 15 µm by 10 µm, is responsible for which of the following diseases? | View Page |
| Arrange the following hookworm symptoms in order of their occurance based on the parasite's migration through the body beginning with human transmission: | View Page |
| This suspicious form measures 15 µm and was recovered in stool. Which of the following conditions is/are associated with the presence of this form? | View Page |
| Match each parasite named below with its respective primary symptom: | View Page |
| Which of the following parasites is/are considered as atrial ameba(e)? | View Page |
| Arrange the basic steps in the intestinal ameba life cycle in order starting with transmission to a human host: | View Page |
| The motile, feeding stage of the amebas and flagellates is called: | View Page |
| Match each parasite listed here with its corresponding optimal specimen type from which it may be recovered: (Answers may be used more than once.) | View Page |
| Match each parasite listed here with its corresponding optimal specimen type from which it may be recovered: (Answers may be used more than once.) | View Page |
| Match each common name of the helminth groups with its respective scientific name: | View Page |
| Match each parasite listed here with its respective common name: | View Page |
| The body of an adult cestode consists of segments called: | View Page |
| Adult intestinal roundworms are equipped with this structure that serves as a protective outer layer: | View Page |
| Which of the following parasites lay live larvae? | View Page |
| Which of the following parasites, whose common names are listed below, is/are intestinal in nature? | View Page |
| Arrange the parasites listed here in increasing order (starting with none) based on the length of their undulating membranes: | View Page |
| The morphologic structure of select tapeworms that is most likely responsible for piercing the human intestinal wall is/are called: | View Page |
| Label the morphologic structures on this parasite form: | View Page |
| Label the morphologic structures on this parasite form: | View Page |
| A 21 year old male presented in the emergency room with symptoms resembling a liver infection. The patient complained of abdominal pain, fever, cough, nausea, vomiting and constipation alternating with diarrhea. Further examination revealed the presence of a hepatic abscess. This suspicious form was recovered following parasitic examination of a sample from the abscess and measures 20 µm. What condition is the patient most likely suffering from? | View Page |
| A 35 year old male presented to the local clinic complaining of abdominal cramps, severe diarrhea, and intestinal gas discomfort. A stool was collected for parasite examination. It was foul-smelling and light colored in nature. This suspicious form was recovered and measured 10 µm by 12 µm. The patient is infected with: | View Page |
| A 55 year old female, who recently returned from an extensive trip to China, presented to her physician complaining of diarrhea and abdominal cramps. The doctor ordered a complete blood count (CBC), chem 21 panel, and stool for culture and parasite examination (O & P). The CBC revealed pronounced eosinophilia. The chem 21 and stool culture were unremarkable. The O & P revealed suspicious forms like the one below that each measured approximately 140 µm by 80 µm. This patient is most likely infected with: | View Page |
| A 16 year old male champion athlete went to his doctor complaining of a persistent cough, fever, bloody diarrhea and overall weakness. Upon questioning the patient, it was learned that he had recently competed in a freshwater swimming competition in the Caribbean. Examination revealed a dermatitis on the patient's right calf. A battery of tests were ordered including a CBC, chemistry profile, and a stool for culture and parasitic examination. The CBC revealed the presence of eosinophilia. The other hematology and chemistry tests were unremarkable. The culture was negative. This suspicious form was seen on all parasite preparations made from the stool sample submitted. This form measures 165 µm by 68 µm. This patient is most likely suffering from an infection with: | View Page |
| A 10 year old male presented to the local Appalachian Mountain clinic complaining of vomiting, fever and severe abdominal pain. Patient history revealed that the child lives in the area in substandard conditions and receives only one balanced meal per day. A stool was collected and submitted for parasite study. This suspicious form, measuring 50 µm by 35 µm was found. This patient is most likely infected with: | View Page |
| I am found in stool and measure 75 µm by 55 µm. | View Page |
| The artifact that when seen is indicative of intestinal inflammation and is characteristic of a number of parasitic infections is known as (a): | View Page |
| The locomotive structures of Entamoeba histolytica are known as: | View Page |
| This parasite measure 50 µm by 30 µm. Its common name is: | View Page |