3/22 - UWorld (heme)

Question 1

Lymph nodes of the large intestine

Answer 1

Question 2

What parts of the body drain to the superficial inguinal lymph nodes?

Answer 2

Most of the cutaneous lymph from the umbilicus down, including the anus

Exceptions are the glans penis and posterior calf, which drain to the deep inguinal nodes

Question 3

What is the pathophysiology of cystic fibrosis?

Answer 3

Defect in CFTR gene on chromosome 7

CFTR normally encode an ATP-gates Cl- channel that:

• Secretes Cl- in the lungs and GI tract
• Absorbs Cl- in sweat glands

Less Cl- secretion into the lungs means less Na+ secretion, and thus less water secretion –> thick mucus

Less Cl- reabsorption in the sweat glandsleads to excess Cl- in the sweat –> diagnostic test

Risk of hypokalemia due to malabsorption of fat-soluble vitamins

Question 4

Describe the effects of carbon monoxide poisoning

Answer 4

CO poisoning can occur due to exposure to gas exhausts, fire smoke, or improperly vented natural gas appliances

CO binds to hemoglobin with higher affinity that O2:

• CO-bound hemoglobin (carboxyhemoglobin) levels increase
• PaO2 remains normal

Question 5

What causes shifts of oxygen-hemoglobin dissociation curve, and in what direction?

Answer 5

Shifting curve to the R (hemoglobin more likely to release O2):

Think of places where you want to give O2 to the tissues, such as muscles or placenta:

• low pH (lactic acid being produced)
• high temp (when muscles being used)
• high pCO2
• 2,3 BPG (this is an intermediate of glycolysis)

Shifting cuve to the L (hemoglobin holding on to more O2):

(e. g. lungs)
- high pH (breathing off CO2 = low acidity)
- low temp (breathing in cool air)
- low pCO2
- HbF (super high affinity for O2)

Question 6

What forms will candida be in at what temperatures?

Answer 6

Pseudohyphae with budding yeast at 20 C (first image)

Germ tubes at 37 C (second image)

Question 7

What is mean corpuscular hemoglobin concentration (MCHC) and when will it be elevated?

Answer 7

MCHC is a measure of hemoglobin concentration. It will be increased when cells shrink but cytoplasm remains the same, thus increasing Hb concentration

Will be elevated in hereditary spherocytosis

Question 8

Which part of the thymus (cortex or medulla) does positive and negative selection take place?

Answer 8

Positive selection - thymic cortex

Negative selection - thymic medulla

Question 9

What are the top 3 most common cancers among women, aside from skin cancer?

Answer 9

1) breast (low mortality rate)
2) lung (high mortality rate)
3) colon

Question 10

Describe cyanide toxicity and explain the reasoning behind administering amyl nitrate

Answer 10

Cyanide binds ferric iron (Fe3+) with high affinity, inhibiting cytochrom C oxidae in the mitochondria, thus inhibiting electron transport chain

Cyanide poisoning presents with reddish skin discoloration, tachypnea, HA, and tachycardia

Labs reveal lactic acidosis

Inhaled amyl nitrate will oxidize ferrous iron (Fe2+) in Hb to ferric iron (Fe3+), generating methemoglobin

Methemoglobin is incapable of carrying O2 but has a high affinity for cyanide - so it can bind and sequester cyanide, freeing it from cytochrome oxidase

Question 11

What is the mutation in sickle cell anemia

Answer 11

Glutamic acid –> valine on the beta globin chain

Question 12

What causes cells to sickle in sickle cell anemia?

Answer 12

HbS polymerizes when deoxygenated

Can occur with hypoxemia, dehydration, and acidosis