Membrane & Skeleton
Band 3's day job (besides anchoring the skeleton): it swaps chloride for this ion to help carry CO2.
What is bicarbonate?
The kidney senses this (via HIF) and releases erythropoietin.
What is hypoxia?
The single physical property the spleen is really testing as cells squeeze through its slits.
What is deformability?
The one CBC index that is characteristically HIGH in HS.
What is MCHC?
Given lifelong in chronic hemolysis to prevent a megaloblastic crisis.
What is folic acid?
The main “bridge” anchoring the spectrin skeleton to band 3; the protein most commonly deficient in HS.
What is ankyrin?
Reticulocytes still contain RNA from these organelles that mature RBCs lack.
What are ribosomes?
Blood empties into this open, macrophage-rich meshwork of the red pulp.
What are the Cords of Bilroth
Smear finding: small, dense red cells lacking central pallor.
What are spherocytes?
The definitive treatment that stops the hemolysis but doesn't fix the membrane defect.
What is splenectomy?
Name the two directions of skeletal linkage and what each connects.
What are vertical bonds (skeleton→bilayer, via band 3/ankyrin) and horizontal bonds (spectrin–spectrin & 4.1R junctions)?
Give the reason chronic hemolysis raises folate demand and risks a megaloblastic crisis.
What is: the marrow divides rapidly to replace destroyed cells, burning folate for DNA synthesis faster than intake supplies it?
Describe how the spleen physically separates normal cells from spherocytes.
What is: cells must deform through ~1–3 µm slits to reach the sinusoids, flexible discs pass, rigid spheres are trapped in the cords?
Why is the MCHC high in HS — and what does that reveal about the cells?
What is: the spherocytes are dehydrated (they leak K+ and water), so hemoglobin is more concentrated within each cell?
After splenectomy patients risk overwhelming infection; why is this?
What is: the spleen normally filters and opsonizes encapsulated organisms, so without it they evade clearance causing infection?
Explain why a VERTICAL-bond defect makes a spherocyte while a HORIZONTAL defect makes an elliptocyte.
What is: vertical defects shed membrane so the cell rounds up (sphere); horizontal defects split the skeleton lengthwise into an elongated cell?
Why do reticulocytes climb within days while hemoglobin lags behind?
What is: retics reflect production rate (rises fast with EPO), while Hgb/HCT reflect total red-cell mass, which recovers slowly as hemolysis continues?
Explain why splenectomy fixes the anemia even though the membrane defect remains.
What is: it removes the organ that traps and destroys the spherocytes, so the still-abnormal cells now survive far longer?
With spherocytes on the smear, which test must be NEGATIVE and which one then CONFIRMS HS?
What is: a negative direct Coombs (to exclude autoimmune hemolysis), followed by EMA flow cytometry to confirm HS?
State at least one of the two things done before a child's elective splenectomy to lower Overwhelming Post-Splenectomy Infection risk.
What is: vaccinate against the encapsulated organisms and defer surgery past ~5 years of age (± prophylactic antibiotics)?
Walk through how one missing anchor protein ends as a rigid sphere.
What is: skeleton detaches → bilayer sheds vesicles → surface area falls → biconcave disc becomes a rigid spherocyte?
After a red-cell precursor extrudes its nucleus, what young cell is released into the blood, and what is that nucleus-removing step called?
Name two consequences specific to extravascular (splenic) hemolysis.
What is: increased indirect bilirubin (jaundice, pigment gallstones) and splenomegaly.
Describe how each red-cell index moves in HS — which are LOW, and which are HIGH?
What is: RBC, hemoglobin, hematocrit, and MCV are low, while MCHC and the reticulocyte count are high?
How do folic acid and erythropoietin each help correct the labs, and why are BOTH needed?
What is: EPO is the signal driving red-cell production, folate is the substrate for the DNA synthesis it requires — together the marrow out-produces destruction?