Cytology of the Cervix and Testing for Abnormalities

In the cervix there is a nice transition from the rough and tough squamous epithelial cells of the outside world (vagina) to the squishy secretory columnar epithelial cells of the inside (uterus). Over time the junction between these two cell types moves towards the inside (more squamous cells) and this is normal metaplasia. This is not to be confused with dysplasia, which is the transformation of normal squamous cells to less differentiated cells.

When women get colposcopies the examiner is looking for dysplasia, and two of the tricks they have up their sleeves to make the dysplasia more apparent are vinegar and iodine.

Both rely on the fact that dysplastic cells are more active and have a much larger nucleus:cytoplasm ratio.

  • When vinegar (acetic acid) is applied, the cells become dehydrated, and the nuclei reflect more light. This makes the cells with larger nuclei more prominent because they appear more white. This includes dysplastic cells and cells infected with HPV.
  • With an iodine solution (Lugol’s iodine) the iodine binds to glycogen in cells making them appear dark brown. Healthy columnar cells don’t have glycogen and due to their small amount of cytoplasm, dysplastic and HPV-infected cells don’t either.

Using these two techniques can help differentiate areas of dysplasia and guide sampling biopsies.

Basal Ganglia (fill in the blanks)

The basal ganglia are a group of nuclei in the brain stem and are associated with voluntary motor control, procedural learning and emotions.

I’ve decided to go back to the good old days and have one where you can fill in the blanks.

the answers:

Where diuretics work in the nephron

The nephron is composed of distinct areas that are specific to regulating different electrolytes.

An overview of nephron anatomy

Loop diuretics: blocks the sodium/potassium/chloride transporter in the ascending loop of Henle, potassium-wasting
Thiazide diuretics: blocks the sodium/chloride transporter in the distal tubule, potassium-wasting
Amiloride: directly blocks sodium channels in the collecting duct, potassium-sparing
Spironolactone: blocks the aldosterone receptors in the cortical collecting duct. This causes a decrease in sodium and water reabsorption and decreases potassium secreting (therefore is potassium-sparing)

Anatomy of a nephron

The nephron is divided into 6 distinct parts

  1. Proximal (covoluted) tubule
  2. Descending loop of Henle
  3. Ascending loop of Henle
  4. Distal (convoluted) tubule
  5. Cortical collecting duct
  6. Distal collecting duct

Each of these sections has a main function in adjusting the amount and kind of solutes in the urine. Different drugs and diuretics work at distinct areas, which is why some diuretics are potassium sparing while others (like Lasix/furosemide) are potassium wasting.

Determinants of Glomerular Filtration Rate (GFR)

GFR should be ~100 mL/min

Calculating GFR
(140 – age) x lean body weight (kg) / sCr (umol/L)

What determines GFR

  1. Renal blood flow: effective circulating volume, cardiac output
  2. Resistance to flow: vascular tone of afferent and efferent arterioles
  3. Permeability of glomerular basement membrane

Drugs that increase GFR

  • Prostaglandin: vasodilator (afferent > efferent)
  • Angiotensin II: vasoconstrictor (efferent > afferent)
  • Norepinephrine: vasoconstrictor, increases blood pressure
  • ANP: afferent vasodilator, efferent vasoconstrictor

Drugs that decrease GFR

  • NSAIDs: afferent vasoconstriction
  • ACE Inhibitors: decrease efferent vasoconstriction
  • Angiotensin Receptor Blockers (ARBs): decrease efferent vasoconstriction