Overview
This lecture covers glomerular (ultrafiltration) in the nephron, detailing the structure and adaptations of the Malpighian body for efficient blood filtration in the kidney.
Structure of the Nephron
- The nephron is the kidney's functional unit responsible for filtering blood and forming urine.
- It consists of two main parts: the Malpighian (renal) body and the renal tubule.
- The Malpighian body includes the Bowman's capsule and the glomerulus.
Glomerular Filtration (Ultrafiltration)
- Blood with waste enters the Bowman's capsule and is filtered at the glomerulus.
- Glomerular filtration and ultrafiltration are the same process—filtering blood in the glomerulus.
- Waste and small dissolved substances move from blood into the Bowman's capsule during filtration.
Adaptations of the Malpighian Body
- The afferent arteriole is wider than the efferent arteriole, creating high pressure for filtration.
- Thin walls of the glomerulus (one layer of squamous epithelium) allow easy passage of small substances.
- Podocytes (cells coating the glomerulus) have slits permitting only small molecules to pass; large proteins remain in the blood.
- The Bowman's capsule is cup-shaped, providing a large contact area for efficient filtration.
Important Filtration Characteristics
- Glomerular filtration is non-selective: all small molecules (including both waste and useful substances like glucose) move into the Bowman's capsule.
- Only small dissolved substances pass through; large proteins and cells are retained in blood.
Key Terms & Definitions
- Nephron — functional unit of the kidney that filters blood and forms urine.
- Malpighian body — part of nephron made up of Bowman's capsule and glomerulus.
- Bowman's capsule — cup-shaped structure surrounding the glomerulus; collects filtrate.
- Glomerulus — network of capillaries where blood filtration occurs.
- Afferent arteriole — blood vessel bringing blood into the glomerulus.
- Efferent arteriole — blood vessel carrying blood away from the glomerulus.
- Podocytes — specialized cells with filtration slits around the glomerulus.
- Glomerular/ultrafiltration — process where blood is filtered under pressure in the glomerulus.
Action Items / Next Steps
- Note the cause-and-effect explanation when listing adaptations.
- Be prepared to discuss how useful substances (like glucose) are reabsorbed after filtration in the next lesson.