Kidneys and Nephrons #4exam

Kidneys

• filter blood

• remove waste products and convert the filtrate into urine

Ureters

transports urine from kidneys to bladder

Bladder

• expandable muscular sac

• stores up to 1L of urine

Kidney function

• eliminate metabolic waste

• regulate ion lvls in blood (sodium potassium, calcium, etc.)

• regulate blood pH (H+ and HCO3-)

• BP regulation

• EPO production

• calcitriol formation

• glucogenesis (production of glucose from non-carb structures) during starvation

Kidney location

retroperitoneal space: posterior, within parietal peritoneum

Fibrous Capsule

maintains and protects kidney shape

Renal fascia

anchors kidney to surrounding structures

perinephric fat

provides cushioning + support for the kidney

kidney regions

• renal cortex

• renal medulla

structures within the renal cortex

renal columns

corticomedullary junction

corticomedullary junction

• base of the pyramid

• lies at edge of medulla

structures within the renal medulla

• renal pyramids

• renal papilla

• renal lobes

• renal sinus

• minor calyx

• major calyx

• renal pelvis

renal pyramids

subdivisions of columns that appear stripped

renal papilla

apex of the renal pyramids

renal sinus

urine drainage area

minor calyses

8-15 funnels

drains into major calyx

major calyses

2-3

drains into renal pelvis

renal pelvis

merge with ureters at the hilum

kidney is innervated by

both divisions of autonomic NS

• sympathetic nerves

• parasympathetic nerves

sympathetic nerves

• T10-T12

• blood vessels (afferent and efferent arterioles) AND juxtaglomerular apparatus

parasympathetic nerves

CN X

Nephron

functional unit of kidney

Renal corpuscle consists of

1. glomerulus

   1. bowman’s capsule

glomerulus

filters blood

Bowman’s capsule

collects filtrate

capsular space

space btwn layers that receive filtrate

vascular pole

where afferent and efferent arterioles attach to glomerulus

afferent arteriole

brings blood toward glomerulus

afferent = arrive

efferent arteriole

blood exits the glomerulus

efferent = exit

tubular pole

where renal tubule originates

Renal tubes has 3 continuous sections

1. Proximal Convolated Tubule (PCT)

2. Nephron Loop (loop of helene)

3. Distal Convolated Tubule (DCT)

Proximal Convolated Tubule (PCT)

1st region; originates at tubule pole

reabsorbs most nutrients

Nephron loop (Loop of Helene)

creates osmotic gradient

thick and thin segments

thin segment > simple squamous epithelium

thick segment > simple cuboidal epithelium

Distal Convolated Tubule (DCT)

selective absorption

regulated by hormones

2 types of Nephrons

1. Cortical nephron

2. Juxtamedullary nephron

Cortical nephron

• ~ 85% of nephrons

• reside in cortex

• short nephron loops

Juxtamedullary nephron

• ~ 15% of nephrons

• long nephron loops

  • regulates urine concentration due to being sensitive to ADH

Nephrons drains where

↓into collecting tubules

↓collecting tubules drains into collecting ducts

↓collecting ducts drain into papilla ducts

• located within renal papilla

Specialized cells of collecting tubules and ducts

1. Principle cells

2. Intercalated cells

Principle cells

responds to aldosterone and ADH

Intercalated cells

regulates urine pH and blood pH

Type A: eliminates H+ ions (if too acidic)

Type B: eliminates HCO3- ions (if too alkaline)

Juxtaglomerular (JG) apparatus

regulates blood filtrate formation and systemic BP

components of JG apparatus

1. granular cells

2. macula densa cells

   1. extraglomerular mesangial cells

Granular cells (JG apparatus)

• near entrance of renal corpuscle

• contract when stimulated by stretch or sympathetic division

• synthesize, store, release Renin (enzyme)

Macula Densa cells (JG apparatus)

• wall of DCT beside afferent arteriole

• detect change in NaCl concentration of filtrate

• signal granular cells to release renin

Extraglomerular messengial cells (JG apparatus)

• btwn afferent and efferent arterioles

• communicate w other JG cells

• release paracrine

blood flow path

renal artery → segmental a. → interlobar a. → arcuate a. → afferent arteriole → glomerulus → efferent arteriole → pertitubullar capillaries → interlobar v. → arcuate v. → renal vein

Urine formation steps

1. Filtration (glomerulus)

2. reabsorption (tubules → blood)

3. secretion (blood → tubules → urine)

Tubular fluid

water + solutes (filtration) that leave blood (by glomerulus) enter capsular space

tubular fluid filtrate enters PCT, then goes

to nephron loop to DCT to collecting tubules to collecting ducts

• after filtrate leaves collecting ducts, it’s considered urine

filtrate formation

• blood flows through glomerulus

• water + solutes filtered from blood plasma

• moves across wall of glomerulus capillaries and into capsular space

• forms filtrate

filtrate → tubular fluid → urine

Filtrate components:

Capsular Space/Bowman’s Capsule

Tubular Fluid components:

• PCT

• nephron loop

• DCT

• collecting tubule

• collecting duct

Urine components:

• papillary duct

• minor calyx

• major calyx

• renal pelvis

• ureter

• urinary bladder

• urethra