Ppt chapter 50

Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
Introduction to
the Renal System
Chapter 50

Components of the Renal System
• Kidneys
• Organs of the Urinary Tract
– Ureters
– Urinary bladder
– Urethra

Major Functions of the Renal System
• Maintaining the volume and composition of body fluids
within normal ranges
• Regulating vitamin D activation
• Regulating blood pressure through the renin–angiotensin
system
• Regulating red blood cell production through the
production and secretion of erythropoietin

The Kidney and Organs of the Urinary
Tract

Components of the Nephron
• Bowman’s Capsule
• Ascending Loop of Henle
• Distal Convoluted Tubule
• Collecting Ducts
• Renal Pelvises

The Nephron

Processes Involved in the Functioning of
the Nephrons
• Glomerular Filtration
– Straining fluid into the nephron
• Tubular Secretion
– Actively removing components from the capillary
system and depositing them into the tubule
• Tubular Reabsorption
– Removing components from the tubule to return
them to the capillary system and circulation

Maintenance of Volume and Composition
of Body Fluids
• The kidneys regulate the composition of body fluids by
balancing the levels of the key electrolytes.
• They secrete or absorb these electrolytes to maintain the
desired level within the body.
• The volume of body fluids is controlled by diluting or
concentrating the urine.

Sodium Regulation
• Body major cations
• Filters through the glomerulus and enters the renal
tubule, then is actively reabsorbed in the proximal
convoluted tubule to the peritubular capillaries
• As sodium is actively moved out of the filtrate it takes
chloride ions and water with it
• This occurs by passive diffusion as the body maintains
the osmotic and electrical balance on both sides of the
tubule

Carbonic Anhydrase
• Catalyst that influences the sodium reabsorption
• Allows carbon dioxide and water to combine
• This combination forms carbonic acid

Question
Please answer the following statement as true or false.
The body’s mechanism for controlling the volume of body
fluid is by diluting or concentrating the urine.

Answer
True
Rationale: The volume of body fluids is controlled by
diluting or concentrating the urine.

Aldosterone
• Influences the sodium levels
• Is a hormone produced in the adrenal gland
• Is released into the circulation in response to high
potassium levels, sympathetic stimulation, or angiotensin
III
• Stimulates the sodium-potassium exchange pump in the
cells of the distal tubule

Potassium Regulation
• Potassium is another cation that is vital to proper
functioning of the nervous system, muscles, and cell
membranes.
• About 65% of the potassium that is filtered at the
glomerulus is reabsorbed at Bowman’s capsule and the
proximal convoluted tubule.
• Another 25% to 30% is reabsorbed in the ascending loop of
Henle.
• If potassium levels are very high the retention of sodium
exchange for potassium also leads to a retention of water
and a dilution of blood volume.

Chloride Regulation
• Chloride is an important negatively charged ion that
helps to maintain electrical neutrality with the movement
of cations across the cell membrane.
• Chloride is primarily reabsorbed in the loop of Henle,
where it promotes the movement of sodium out of the
cell.

Antidiuretic Hormone
• Produced by the Hypothalamus
• Stored in the Posterior Pituitary Gland
• Important in Maintaining Fluid Balance

Factors Stimulating Release of ADH
• Falling Blood Volume
• Sympathetic Stimulation
• Rising Sodium Levels

Nephrons and Points of Regulation

Countercurrent Mechanism
• It further regulates sodium absorption in the medullary
nephrons in the loop of Henle.
• Sodium is actively reabsorbed into the surrounding
peritubular tissues, and water flows out of the tubule into
this sodium rich tissue to maintain osmotic balance.
• The filter at the end of the descending loop of Henle is
concentrated in comparison to the rest of the filtrate.

Renin–Angiotensin System

Role of the Kidneys
• Influence blood pressure control
• Release renin to activate the renin–angiotensin system
• Leads to increased blood pressure and volume
• Increased blood flow to the kidney
• Can lead to water retention or excretion

Functions of Calcium
• Muscle Function
• Blood Clotting
• Bone Formation
• Contraction of Cell Membranes
• Muscle Movement

Regulation of Vitamin D Activation
• The absorption of calcium from the gastrointestinal (GI)
tract is regulated by vitamin D.
• Vitamin D must be activated in the kidneys to a form that
promotes calcium absorption.
• Once absorbed, calcium levels are maintained within a
very tight range by parathyroid hormone (PTH) and
calcitonin.

Male Urethra
• Passes through the prostate gland
– May enlarge or become infected
• Often associated with advancing age

Question
Vitamin D plays an important part in the absorption of
calcium by the body. Where is vitamin D activated into a
form that promotes calcium absorption?
A. Small intestine
B. Vitamin D is not activated into another form
C. Kidneys
D. Large intestine

Answer
C. Kidneys
Rationale: Vitamin D must be activated in the kidneys to a
form that promotes calcium absorption.

Ppt chapter 50

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Ppt chapter 50