Chapter 23, Lesson 3: Glomerular Filtration

Flashcards from Chapter 23, Lesson 3 of McGraw Hill Anatomy and Physiology, Tenth Edition, by Kenneth S. Saladin.

Urine formation stages

1. Glomerular filtration

2. Tubular reabsorption

3. Tubular secretion

4. Water conservation

Glomerular filtrate

Fluid in the capsular space, similar to blood plasma but without protein

Tubular fluid

Fluid from the proximal convoluted tubule (PCT) to the distal convoluted tubule (DCT), with substances being removed or added by tubules

Urine

Fluid within the collecting duct and beyond, undergoes little alteration beyond this point except for water content changes

Glomerular filtration

The creation of a plasmalike filtrate of the blood; water and some solutes pass from within the glomerulus to the capsular space of the nephron

Tubular reabsorption

Removal of useful solutes from the filtrate to return to the blood

Tubular secretion

Removal of additional wastes from the blood to add to the filtrate

Water conservation

Water removal from the urine to return to the blood

Filtration membrane

Barrier through which filtered fluid passes in the glomerulus with three components:

• Fenestrated endothelium (pores that exclude blood)

• Basement membrane

• Filtration slits (has podocytes for filtration)

Fenestrated endothelium

Part of the filtration membrane that contains large filtration pores that are highly permeable but exclude blood cells

Filtration slits

Slits created by podocyte foot processes wrapping around the capillaries

Proteinuria (albuinuria)

Albumin in the urine

Hematuria

Blood in the urine

Hydrostatic pressure

Pressure that is high in glomerular capillaries to allow for molecule passage

Glomerular filtration rate (GFR)

Amount of filtrate formed by the two kidneys, combined; equals about 50 to 60 times the amount of blood today with 99% reabsorption

Renal autoregulation

The ability of the nephrons ot adjust their own blood flow and glomerular filtration rate (GFR) without external control for stability, regulated through:

• Myogenic mechanism (stretch stabilizer)

• Tubuloglomerular feedback (filtration rate adjustment)

Myogenic mechanism

Stabilizing GFR based on smooth muscle contraction upon stretching

• Higher blood pressure causes arteriole to constrict to prevent flow

• Lower blood pressure causes arteriole to relax to allow for more flow

Tubuloglomerular feedback

Feedback on the glomerulus on the status of downstream fluid to adjust filtration rates

Juxtaglomerular apparatus

Complex structure found at the end of the nephron loop reentering the renal cortex as it comes in contact to the arterioles; uses macula densa and granular cells

Macula densa

A patch of slender, closely spaced sensory cells in the nephron loop that detects filtrate to stimulate granular cells

Granular cells

Modified smooth muscle cells that wrap around arteries close to the macula densa for constriction to correct GFR

Sympathetic control

Constriction of the arterioles by the sympathetic nervous system, adrenal epinephrine during times of shock or strain to redirect blood