Liberal Arts Blog — The Kidney Re-visited — Homeostasis, Osmosis, Dialysis

Liberal Arts Blog — Wednesday is the Joy of Science, Engineering, and Technology Day

Today’s Topic — The Kidney Re-visited — Homeostasis, Osmosis, Dialysis

What should every 8th grader know about the kidney? 12th grader? Harvard graduate? Think about it. Your kidney is your slave — slaving away 24/7. Show some appreciation. Think about what your kidney does for you. Thank your kidney at least once a day. Experts — please chime in. Correct, elaborate, elucidate.

HOMEOSTASIS, OSMOSIS, DIALYSIS — the quest for equilibrium, stability, sustainability

1. In a word: homeostasis. The excretion thing (urination) is really the secondary by-product of an adjustment process, a balancing process, a process of making sure the blood volume and composition is just right. It is a process of determining the gaps between the ideal and the real and closing the gaps. Perhaps a great metaphor for the meaning of the democratic process.

2. To put numbers on it — the kidney processes roughly 200 liters of blood per day but only excretes 1–2. Your entire blood volume (about 1.3 gallons) is recycled every 30 minutes!!!

3. Osmosis is the process by which the system equilibrates.

NB: Dialysis is engineered osmosis. Started with peritoneal dialysis in which the peritoneum, the lining of the abdominal cavity served as the membrane through which the osmosis occurred. The cavity was filled with a solution of the ideal mix of elements sloshing around and equilibrating across the membrane and then the cavity was emptied. Now this is done more elegantly by channeling the blood through an external machine.


1. Keeping blood volume at the optimal level is key to keeping blood pressure at the optimal level.

2. High blood pressure is a major cause kidney failure. The first line of treatment for high blood pressure involves diuretics — to lower blood volume. The first recommendation of cardiologists to those with high blood pressure is to lower salt consumption because salt results in fluid retention.

3. The pituitary gland plays a key role in maintaining blood fluid levels.


1. Typical hemodialysis today takes about 3–5 hours per day, three days per week.

2. It is a complicated procedure requiring expert technicians, high water and electricity quality, high standards of cleanliness, and sophisticated machinery.

3. The first kidney transplant was performed by a plastic surgeon named Joseph Murray in 1954, for which he won the Nobel Prize in Physiology and Medicine in 1990.

NB: “In 2018, an estimated 95,479 kidney transplants were performed worldwide, 36% of which came from living donors.” (See second link below)

FINAL QUESTIONS — Diagrams and Paragraphs

1. What is the best diagram you have ever seen on the kidney?

2. Best paragraph explaining its function? Please share.

Kidney transplantation


PDF with headlines — Google Drive

ATTACHMENT BELOW — “39 Songs, Prayers, and Poems: Keys to the Hearts of Seven Billion People” — handout from Zoom presentation made to Adams House Senior Common Room in November 2020.


Please share the coolest thing you learned this week related to science, engineering, or technology. Or, even better, the coolest or most important thing you learned in your life related to science and engineering.

This is your chance to make someone else’s day. Or to cement in your mind something that you might otherwise forget. Or to think more deeply about something dear to your heart. Continuity is key to depth of thought.



Passionate about education, thinking citizenship, art, and passing bits on of wisdom of a long lifetime.

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John Muresianu

Passionate about education, thinking citizenship, art, and passing bits on of wisdom of a long lifetime.