1- Kidney Anatomy

Blood osmolarity

measures the concentration of dissolved particles in your blood, crucial for balancing water inside and outside of the cell

Kidney regulation of blood osmolarity

↑osmolarity, indicates dehydration or excess solutes, triggering thirst and water retention

↓osmolarity, suggests overhydration, causing water excretion

Diagnosis of blood osmolarity

fluid/electrolyte problems, dehydration, kidney issues, and diabetes

Blood pH

tightly regulated to be between 7.35 to 7.45, crucial for enzymes and oxygen transport, with extreme levels potentially fatal

Acidosis

blood pH below 7.35

Alkalosis

blood pH above 7.45

Lungs role in maintaining blood pH

controls CO2 levels by expelling it

Kidneys role in maintaining blood pH

excrete excess acids or bases in urine

Kidneys regulation of blood volume

adjusts water and sodium excretion in urine, controlled by aldosterone, ADH, and RAS in response to changes in blood pressure and fluid balance

Kidneys and blood pressure relationship

high blood pressure → kidney damage → further uncontrolled blood pressure

How does high blood pressure harm kidneys?

1. vessel damage

2. impaired filtration

3. hormonal imbalance

Kidney hormones

• renin

• erythropoietin (EPO)

• vitamin D (Calcitriol)

Erythropoietin

stimulates bone marrow to produce RBC, essential for oxygen delivery; prevents anemia

Renin

enzyme the starts the Renin-Angiotensin System, crucial or regulating blood pressure by controlling blood vessel constriction and fluid balance; combats hypertension

Active vitamin D (calcitriol)

kidneys convert inactive vitamin D → active form, helps absorb calcium and phosphorus from the gut and keeps bone strong; prevents disorders like rickets

Kidneys filtration of foreign substances

filters using millions of nephrons, primarily at the glomerulus; removes toxins, drugs, and metabolic wastes while conserving vital nutrients

Glomerulus

network of capillaries that acts as a sieve, filtering based on size and charge, preventing large molecules and cells from passing

Tubules

fine-tune the filtrate by reabsorbing needed substances and secreting wastes, ensuring balance

What is filtered by kidneys?

• water, urea, creatinine, uric acid

• ions and electrolytes

• drugs and toxins

• glucose and amino acids

Proximal convoluted tubule

reabsorbs ions, water, and nutrients, removes toxins and adjusts filtrate pH

Distal tubule

selectively secretes and absorbs different ions to maintain blood pH and electrolyte balance

Collecting duct

reabsorbs solutes and water from filtrate

Descending loop of henle

aquaporins allow water to pass from filtrate into interstitial fluid

Ascending loop of henle

reabsorbs sodium and calcium from the filtrate into the interstitial fluid

Steps of filtration through nephrons

1. glomerulus

2. proximal convoluted tubule

3. descending loop of henle

4. ascending loop of henle

5. distal tubule

6. collecting duct

Renal fascia

envelopes the kidney in dense, elastic connective tissue; also encases the adrenal gland

Perirenal fat layer

around the kidneys, thickest at the renal borders and extends into renal sinus at the hilum

Renal cortex

vascular outer portion, contains glomeruli enclosed in Bowman’s capsule; afferent arteriole enters with blood with waste, efferent arteriole exits blood without waste

Renal medulla

inner region containing renal pyramids, containing loops of henle and collecting ducts; crucial for concentrating urine and balancing body fluids, salts, and acids by reabsorbing water and electrolytes

Body fluids

blood, plasma, interstitial, intracellular; crucial for transport, temperature, and metabolism and divided into intracellular and extracellular compartments

Clearance

refers to the body’s process of removing waste, often measured by kideny function or specialized systems

Body fluid composition

water, makes up about 60% of body weight

Intracellular fluid

inside cells, 2/3 of body fluid, 40% body weight

Extracellular fluid

outside cells, 1/3 of body fluid, 20% of body weight

Renal clearance

how the kidneys filter waste from blood, measured by creatinine clearance by assessing how much creatinine is removed from plasma per unit time

Glymphatic system

brain-specific network using perivascular space and water channels to flush metabolic waste from the brain via cerebrospinal fluid

Waste transport

fluids carry metabolic waste to elimination organs (kidney, lungs, skin)

Which organs regulate body fluids?

brain, adrenal glands, kidneys