What are the main functions of the kidneys?
- Maintain water and ion balance
- Regulate osmolarity
- Maintain plasma volume and acid-base balance
- Excrete wastes and foreign compounds
- Produce erythropoietin, renin, and activate vitamin D
How does the male urethra differ from the female urethra?
The male urethra is longer and serves both urinary and reproductive functions; the female urethra is shorter and only carries urine
What is the nephron?
The functional unit of the kidney that forms urine; about 1 million per kidney.
What are the two types of nephrons?
- Cortical nephrons (80%) — short loops of Henle.
- Juxtamedullary nephrons (20%) — long loops important for urine concentration.
What are the functions of the nephron’s vascular parts?
- Afferent arteriole: Brings blood to glomerulus.
- Glomerulus: Filters plasma.
- Efferent arteriole: Carries blood away.
- Peritubular capillaries: Exchange substances with tubules
What are the functions of the nephron’s tubular parts?
- Bowman’s capsule: Collects filtrate.
- Proximal tubule: Major reabsorption site.
- Loop of Henle: Creates osmotic gradient.
- Distal tubule/collecting duct: Controlled reabsorption and secretion
What layers form the glomerular membrane?
- Glomerular capillary wall
- Basement membrane
- Inner layer of Bowman’s capsule (podocytes
What forces affect glomerular filtration?
- Glomerular capillary blood pressure (55 mmHg) – favors filtration
- Plasma-colloid osmotic pressure (30 mmHg) – opposes
- Bowman’s capsule hydrostatic pressure (15 mmHg) – opposes
How is Net Filtration Pressure (NFP) calculated?
NFP = GCBP – (PCOP + BCHP)
= 55 – (30 + 15) = 10 mmHg
What increases and decreases GFR?
High arterial pressure or afferent arteriole dilation then deceasing: Kidney stones, dehydration, or constricted afferent arteriole
What substances are completely reabsorbed
Glucose and amino acids
What substances are mostly reabsorbed?
Sodium, chloride, and water
What are the 5 barriers in transepithelial transport?
- Luminal membrane
- Cytosol
- Basolateral membrane
- Interstitial fluid
- Capillary wall
Where is most sodium reabsorbed?
67% in the proximal tubule.
What hormone increases Na⁺ reabsorption?
Aldosterone
Which system controls aldosterone secretion?
Renin–angiotensin–aldosterone system (RAAS).
What hormones decrease Na⁺ reabsorption
Atrial natriuretic peptide (ANP) and Brain natriuretic peptide (BNP
What is the tubular maximum (Tm)?
The maximum amount of a substance that can be reabsorbed per minute.
What is the renal threshold for glucose?
300 mg/100 mL of plasma
What hormone regulates calcium and phosphate reabsorption?
Parathyroid hormone (PTH).
What percent of water is reabsorbed in each nephron part?
- Proximal tubule: 65%
- Loop of Henle: 15%
- Distal/collecting tubule: 20% (hormonal control)
Which hormone controls water reabsorption?
Vasopressin (antidiuretic hormone, ADH).
What are the main substances secreted?
H⁺, K⁺, and organic ions (e.g., drugs, bile salts, ammonia).
What regulates K⁺ secretion?
Aldosterone.
