Ppt chapter 50-1

Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins

Introduction to the Renal SystemIntroduction to

the Renal System

Chapter 50


Components of the Renal SystemComponents of the Renal System

• Kidneys

• Organs of the Urinary Tract

– Ureters

– Urinary bladder

– Urethra


Major Functions of the Renal SystemMajor 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

The Kidney and Organs of the Urinary Tract


Components of the NephronComponents of the Nephron

• Bowman’s Capsule

• Ascending Loop of Henle

• Distal Convoluted Tubule

• Collecting Ducts

• Renal Pelvises


The NephronThe Nephron


Processes Involved in the Functioning of the Nephrons

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

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 RegulationSodium 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 AnhydraseCarbonic Anhydrase

• Catalyst that influences the sodium reabsorption

• Allows carbon dioxide and water to combine

• This combination forms carbonic acid


QuestionQuestion

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.


AnswerAnswer

True

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


AldosteroneAldosterone

• 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 RegulationPotassium 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 RegulationChloride 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 HormoneAntidiuretic Hormone

• Produced by the Hypothalamus

• Stored in the Posterior Pituitary Gland

• Important in Maintaining Fluid Balance


Factors Stimulating Release of ADHFactors Stimulating Release of ADH

• Falling Blood Volume

• Sympathetic Stimulation

• Rising Sodium Levels


Nephrons and Points of RegulationNephrons and Points of Regulation


Countercurrent MechanismCountercurrent 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 SystemRenin–Angiotensin System


Role of the KidneysRole 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 CalciumFunctions of Calcium

• Muscle Function

• Blood Clotting

• Bone Formation

• Contraction of Cell Membranes

• Muscle Movement


Regulation of Vitamin D ActivationRegulation 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 UrethraMale Urethra

• Passes through the prostate gland

– May enlarge or become infected

• Often associated with advancing age


QuestionQuestion

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


AnswerAnswer

C. Kidneys

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

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Ppt chapter 50-1