ANATOMIA FUNZIONALE DEL RENE

UNITA’ FUNZIONALE DEL RENE: il nefrone

ANATOMIA FUNZIONALE DEL RENE

IL CORPUSCOLO RENALE: CAPSULA DEL BOWMAN

APPARATO JUXTAGLOMERULARE

MECCANISMI IMPLICATI NELLA FORMAZIONE DI URINA

MECCANISMI IMPLICATI NELLA FORMAZIONE DI URINA: FILTRAZIONE GLOMERULARE

SCAMBI CAPILLARI

DINAMICA DELLA FILTRAZIONE GLOMERULARE

Pg=45mmHg Pc=10mmHg πG=25mmHg πC=0

Pressione netta (Puf)=10mmHg

Feedback tubuloglomerulare

RIASSORBIMENTO di glucosio e amminoacidi

RIASSORBIMENTO di glucosio: a tubulare massimo

RIASSORBIMENTO PASSIVO DI SOLUTI

RIASSORBIMENTO PASSIVO DI UREA

CLEARANCE RENALE

CLEARANCE RENALE

Figure 20-6, steps 1–4

Collecting duct cell

Second messenger signal

Collecting duct

lumen

Medullary interstitial

fluid Vasa recta

Filtrate 300 mOsM

cAMP

Exocytosis of vesicles

Vasopressin receptor

700 mOsM 600 mOsM

Aquaporin-2 water pores

600 mOsM

Cross section of kidney tubule

Vasopressin

Vasopressin binds to membrane receptor.

Receptor activates cAMP second messenger system.

Water is absorbed by osmosis into the blood.

Storage vesicles Cell inserts AQP2 water pores into apical membrane.

H2O H2O

H2O

H2O

1

2

3

4 1

2

3

4

Figure 20-12, steps 1–5

New channels

P cell of distal nephron

Translation and protein synthesis

Proteins modulate existing channels and pumps

New pumps

K+

Na+

K+ secreted

Na+ reabsorbed

Lumen of distal tubule

Interstitial fluid Blood

Aldosterone Aldosterone

receptor

K+

Na+

Na+

Aldosterone combines with a cytoplasmic receptor.

Hormone-receptor complex initiates transcription in the nucleus.

New protein channels and pumps are made.

Aldosterone-induced proteins modify existing proteins.

Result is increased Na+ reabsorption and K+ secretion.

K+

ATP

ATP

1

2

3

4

5

1 2 3

4

5

Sistema renina-angiotensina-aldosterone

Urine Concentration

Figure 20-4, steps 1–4

50–1200 mOsM urine excreted

300 mOsM 300 mOsM

600 mOsM

900 mOsM

1200 mOsM 1200

300 100

Distal tubule

Proximal tubule

Loop of

Henle

CORTEX MEDULLA

Permeability to water and solutes is regulated by hormones.

Variable reabsorption of water and solutes

Ions reabsorbed but no water Only water

reabsorbed

Isosmotic fluid leaving the proximal tubule becomes progressively more concentrated in the descending limb.

Removal of solute in the thick ascending limb creates hyposmotic fluid.

Hormones control distal nephron permeability to water and solutes.

Urine osmolarity depends on reabsorption in the collecting duct.

1

2 3

4

1

2

3

4

Collecting duct

Figure 20-5a

Water Reabsorption

Figure 20-5b

MECCANISMO di moltiplicazione CONTROCORRENTE

RUOLO DEI VASA RECTA (SCAMBIATORI CONTROCORRENTE)

REGOLAZIONE DELLA PRODUZIONE DI ADH

Figure 19-18b, steps 1–3

Stretch receptors fire.

Parasympathetic neurons fire. Motor neurons stop firing.

Smooth muscle contracts. Internal sphincter passively pulled open. External sphincter relaxes.

(b) Micturition

Internal sphincter External sphincter

Tonic discharge inhibited

Higher CNS input may facilitate or

inhibit reflex Sensory neuron

Parasympathetic neuron

Motor neuron

Stretch receptors

1

2

3

1 2

3

2 3

MINZIONE

MECCANISMO RENALE DI RIASSORBIMENTO DEL BICARBONATO