Human Physiology Exam 3 Part 1

Renal Physiology

First Homeostatic Role of the Renal System

Regulation of water, inorganic ion balance, and acid-base balance

Second Homeostatic Role of Renal System

Removal of metabolic waste products from the blood and their excretion in the urine

Third Homeostatic Role of Renal System

Removal of foreign chemicals from the blood and their excretion in the urine

Fourth Homeostatic Role of the Renal System

Gluconeogenesis

Fifth Homeostatic Role of Renal System

Production of hormones/enzymes

Primary organs of the urinary system

Kidney

Ureter

Bladder

Urethra

Nephron

The functional unit of the Kidney

Renal Cortex

Outer Layer of Kidney

-Houses Cortical Nephrons

-contains renal corpuscles

-contains convoluted tubules

Renal Medulla

Inner layer of the kidneys

- contains long Loops of Henle

- contains collecting ducts

What % of Nephrons are cortical

85%

What % of Nephrons are Juxtamedullary

15%

Cortical Nephrons

• Short or no Loops of Henle

• Do not contribute to hypertonic medullary

interstitium

• Change volume and composition of filtrate

Juxtamedullary Nephrons

• Long Loops of Henle

• Generate gradient in medulla

important for H2O reabsorption

• Peritubular capillaries are called the vasa recta

• Concentrate the filtrate

Juxtamedullary Loops of Henle vs Cortical

Long in Juxtmedullary and short or no loops in cortical

First basic renal process

Glomerular Filtration (Filtration)

(20% of plasma is filtered, 80%

continues into peritubular capillaries

The 20% enters bowman’s space

Second basic renal process

Tubular Secretion

From 80% that wasn’t filtered

Depends on the state of homeostasis to decide what is secreted into tubule

Third basic renal function

Tubular Reabsorption

-Reabsorb from filtrate and put back into

plasma. Prevents excretion in urine.

Tubule → Peritubuar cappilary/vim

Fourth Basic renal process

Urinary Excretion

(Filtation + Secretion) - Reabsorption = Excretion

Volume of material actually excreted after the other 3 processes.

Three layers of golmerular complex

1.) Capillary Endothelium (50x more leaky than other

typical systemic capillary beds)

2.) Basement Membrane (negative charge)

3.) Bowman’s Epithelium (i.e. podocytes)

What is PGC

Glomerular capillary blood pressure

Only force to favor filtration

Normally 60 mmHg

What is PBS

Bowmans Space Pressure

what is πGC

Osmotic force due to protein in plasma

Net glomerular filtration pressure (GFP)

GPT = PGC - PBS - πGC

PGC → Glomerular capillary blood pressure

PBS → Bowmans Space Pressure

πGC → Osmotic force due to protein in plasma

*Positive pressure indicates filtration

Is Sodium excreted?

No, only filtered or reabsorbed, which leads to excretion

What can modify PCG (Glomerular blood pressure)?

Changers in the Efferent arteriole (away from glomeruli) or Afferent arteriole (to glomeruli)

What does caffeine do for renal system?

Dilate efferent arteriole (increases filtration)

What is GFR?

Glomerular filtration rate

Standard GFR

125 mL/min (180 L/day)

RAAS

Renin/Angiotensin/Aldosterone System

What does Angiotensin II do?

Cause Aldosterone action (Promotes retention of H2O and Na+)

Targets CV to cause vasoconstriction

Overall Blood Pressure Increase

Atrial Natriuertic Peptide (ANP)

Anti-aldosterone

Causes an increase in sodium excretion

MAIN function of Vasopressin/ADH

Detect osmolarity changes in the body (excess or low H2O).

The presence of ADH causes water retention through distal tubule reabsorption

Substances that are likely fully reabsorbed

Glucose & amino acids

Transcellular reabsorption route

Luminal membrane → Basolateral membrane → Renal Interstitial fluid → Peritubular capillaries

Used for carrier mediated transport

Paracellular reabsorption route

Thru tight junctions → renal interstitial fluid → peritubular capillaries

passive process diffusion reabsorption

Size varies by region of tubular lumen

(typically proximal tubule has much wider junctions)

Where does most secretion occur?

Proximal tubule

RPC

Renal Plasma Clearance

RPCinulin = ?

GFRm (typically 125 mL/min)

(Inulin freely filtered, but not secreted or reabsorbed)

Inulin

Exogenous substance

RPCCreatinine = ?

GFRe

Estimated based on the filtration of creatinine

Creatinine is freely filtered but not reabsorbed with slight secretion.

Filtered load equation

FL = GFR x Px

Px: subtance plasma concentration

GFR: Glomeruler filtration rate

Excreted Load Equation (EL)

EL = V x Vx

V= Urine Flow Rate

Vx = Concentration of substance in urine

RPC (C) Equation

C = Ux x V / Px

Ux = Urine Concentration

V = Urine Flow

Px = Plasma Concentration

Renal Plasma Flow

Volume of plasma going to kidneys per minute

Calculated using PAH Clearance (PAH 100% secreted and freely filtered)

RPC of PAH = ?

Renal Plasma Flow

Normally 625 mL/min

Micturition

Urination

Detrusor

Large Smooth muscle pouch of bladder

Internal urethral sphincter

smooth musclle sphincter on bladder

External urethral sphincter

skeletal muscle sphincter of bladder

Efferent of Detrusor

Parasypathetic

(cotracts)

Efferent of Internal Urethral sphincter

Sympathetic

(contricts)

Efferent of External urethral sphincter

Somatic motor

(Causes contraction)

Where does Na+ reabsorption occur?

PROXIMAL TUBULE