FUNCTION OF THE KIDNEYS

What do the Kidneys regulate?

1) Extracellular Fluid Volume

2) Blood Pressure

3)Osmolarity

4)pH

FUNCTION OF THE KIDNEYS

What do the kidneys maintain?

Ion Balance

FUNCTION OF THE KIDNEYS

What do the kidneys excrete?

FUNCTION OF THE KIDNEYS

In what pathways do the kidneys participate?

ANATOMY OF THE URINARY SYSTEM 

Name the structures that compose the urinary system.

Two Kidneys

Two Ureters

One Bladder

One Urethra

ANATOMY OF THE URINARY SYSTEM

How is the kidney arranged in cross-section? 

An outer cortex

and 

An inner medulla

ANATOMY OF THE URINARY SYSTEM

Fill in the blank:

Each Kidney has about 1 million microscopic (Blank). 

Nephrons

ANATOMY OF THE URINARY SYSTEM

Describe the route of Renal Arterial Blood Flow. 

Renal artery --> Afferent Arteriole --> Glomerulus -->

Efferent Arteriole --> Peritubular Capillaries -->

Vasa Recta Capillaries

ANATOMY OF THE URINARY SYSTEM

Describe the route of fluid filtration in the kidneys:

Fluid filters from the glomerulus into Bowman's capsule. From there it flows through the proximal tubule, loop of Henle, distal tubule, and collecting duct. Then it drains into the renal pelvis. Urine flows through the ureter to the urinary bladder.

Overview of Kidney Function:

The movement of fluid from plasma into Bowman's Capsule:

Overview of Kidney Function:

The movement of filtered materials from tubule to blood:

Overview of Kidney Function:

The movement of selected molecules from blood to tubule:

Overview of Kidney Function:

Average Urine Volume/day:

Overview of Kidney Function:

Osmolarity of Kidneys:

Overview of Kidney Function:

The urinary excretion of a substance depends on its filtration, reabsorption, and secretion. Give the formula for amount of solute secreted:

Amount     Amount          Amount     Amount of Solute

Filtered  -  Reabsorbed + Secreted =       Excreted

FILTRATION:

Fill in the blank.

One-fifth of (Blank) filters into the tubule lumen.

Renal Plasma Flow

FILTRATION:

The filtration fraction is:

The percentage of total plasma volume that is filtered.

FILTRATION:

What are podocytes and what do they do?

Specialized cells of the epithelium of Bowman's capsule. They wrap around the glomerular capillaries and create filtration slits

FILTRATION:

 Mesangial Cells are associated with (Blank).

The Glomerular Capillaries

FILTRATION:

Describe the pathway of filtered solutes through a renal corpuscle.

Filtered solutes pass first through glomerular capillary endothelium, then basal lamina, and finally through Bowman's capsule epithelium before reaching the lumen of the Bowman's capsule.

FILTRATION:

Describe what is filtered in the renal corpuscle.

Most components of plasma are allowed to enter the tubule. Blood cells and plasma proteins are excluded.

FILTRATION

What is the average hydrostatic pressure in glomerular capillaries? What does this indicate?

Average hydrostatic pressure = 55 mm Hg

Indicates a tendency toward filtration.

FILTRATION

Name pressures opposing filtration, there average values, and what this means in relation to hydrostatic pressure.

Colloid Osmotic pressure: 30 mm Hg

Hydrostatic capsule fluid pressure: 15 mm Hg

The opposing pressures come to a total of 45 mm Hg. Hydrostatic pressure = 55 mm Hg and therefore there is a net driving force of 10 mm Hg favoring filtration.

FILTRATION

What is the Glomerular Filtration Rate, and what is its average value?

This is the amount of fluid that filters into Bowman's capsules per unit time. The average value is 125 mL/min or 180 L/day. 

FILTRATION

What alters hydrostatic pressure in glomerular capillaries?

Resistance in the afferent and efferent arterioles.

FILTRATION

How is autoregulation of glomerular filtration accomplished?

It is accomplished by a myogenic response of vascular smooth muscle in response to pressure changes and by tubuloglomerular feedback. When fluid flow through the distal tubule increases, the macula densa cells send a paracrine signal to the afferent arteriole which constricts.

(See fig 19-10 in the text p. 634)

FILTRATION

How is reflex control of GFR (glomerular filtration rate) mediated?

Through systemic signals such as hormones and the autonomic nervous system.

REABSORPTION

Where does most reabsorption occur? Where does finely regulated reabsorption occur?

Most: in the proximal tubule

Finely regulated: the distal segment of the nephron

REABSORPTION

What creates concentration gradients for passive reabsorption of urea and other solutes.

The active transport of Na+

REABSORPTION

What is the primary mode of reabsorption? What is an alternative reabsorption pathway?

Primary: transepithelial transport

Alternative: paracellular pathway

REABSORPTION

Name 4 molecules which are reabsorbed by Na+ linked secondary active transport.

Glucose

Amino Acids

Ions

Various organic Metabolites

REABSORPTION

Most renal transport is mediated by (Blank) and exhibits (Blank 3x). The (Blank) is the transport rate at saturation.

Membrane Proteins

Saturation, Specificty, and Competition

Transport Maximum (Tm)

REABSORPTION

What is the renal threshold?

The plasma concentration at which a substance first appears in the urine. 

REABSORPTION

What is a primary function of peritubular capillaries?

They reabsorb fluid along their entire length.

SECRETION

How does secretion enhance excretion? What molecules are secreted?

Secretion removes solutes from the peritubular capillaries.

Secretion removes K+, H+, and a variety of organic compounds.

SECRETION

What slows the secretion of a molecule?

Molecules that compete for renal carriers.

EXCRETION

The excretion rate depends on:

(Two factors)

1) its filtered load

2) whether it is reabsorbed or secreted as it passes through the nephron

EXCRETION

What is clearance?

How many milliliters of plasma passing through the kidneys have been totally cleared of a solute in a given period of time.

EXCRETION

Inulin clearance = (Blank)

Creatinine is used to measure (same Blank).

Glomerular Filtration Rate (GFR)

MICTURITION

What is the external sphincter composed of and what is its state of being except during urination?

The external sphincter is composed of skeletal muscle and it is tonically contracted except during urination.

MICTURITION

Micturition is a simple (Blank) subject to (Blank) and (Blank) control.

Spinal Reflex

Conscious

Unconscious

MICTURITION

Describe the roles of the parasympathetic and somatic neurons during micturition.

Parasympathetic neurons cause contraction of the smooth muscle in the bladder wall. Somatic motor neurons leading to the external sphincter are simultaneously inhibited.