ADVANCED RENAL ANATOMY AND PHYSIOLOGY

Body Fluids and Gross External AnatomyInternal Gross Anatomy of Kidney

BODY FLUIDS

Water is the major component of the body

Makes up 45-80% of the body weight

DISTRIBUTION OF BODY WATER

Two major compartments• Intracellular (Inside cells)

• 2/3 of total body water

• Extracellular (Outside cells)• 1/3 of total body water

• Intravascular (within a blood vessel)

• 5% of body weight

• Interstitial (water between cells, organs, tissues)

• 15% of body weight

DISTRIBUTION OF BODY WATER

Solvent• Any liquid in which a substance can be

dissolved

Solute• Substance being dissolved

Solution• Stable mixture of two or more substances in a

single phase

DISTRIBUTION OF BODY WATER

Colloid

• State of matter where large molecules are suspended in a liquid

Colloid dispersion

• Substance with components of one or two phases

DISTRIBUTION OF BODY WATER

Movement of water• Water diffuses freely

• Osmotic pressure

Osmotic pressure• Force produced by solvent particles of a solution as

they move through a semi-permeable membrane

• Depends on the number of particles in a solution

• Inversely proportional to the volume of a solvent

• Varies directly with temperature

DISTRIBUTION OF BODY WATER

Osmosis• The movement from high

concentration to low concentration across a membrane

• Equalize concentration on either side

Isotonic 0.9% Hypertonic > 0.9%

• Will draw water out of cells or tissues

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WHAT IS THISGARBAGE?!!!

OSMOTIC PRESSURE

Typical membranes restrict passage of colloidal particles

Proteins account for plasma’s high colloid osmotic pressure• Albumins

• 60% of plasma proteins

• Most abundant protein for transporting

CONTROL OF WATER MOVEMENT

Regulated by

• Thirst• Low water intake-levels of sodium increase

• Kidneys decrease urine volume

• High sodium-body increases amount of retained water

• Kidneys secrete ADH

• Water excretion by the Kidneys

Water Loss Sensible water loss

• Urine and GI tract• Vomiting, diarrhea, suctioning from stomach

Insensible water loss• Skin (Fever)

• Lungs (Inadequate humidity)• Artificial airways

• Increased ventilation

Tracheostomy patient may lose an additional 700ml/day of water if humidification is inadequate

KIDNEYS

Kidneys are Retroperitoneal

• Lie behind (outside) the lining of the abdominal cavity

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KIDNEYS

Maintain the volume and concentration of body fluids by

• Filtration and re-absorption of sodium

• Water secretion regulated by anti-diuretic hormone (ADH)

• Any material that is filtered and not reabsorbed will be lost in urine

FUNCTION OF THE URINARY SYSTEM

Homeostasis of the body

• Controlling volume and concentration of blood

• Removing and restoring select amounts of water and solutes

• Excreting select amounts of wastes

FUNCTION OF THE KIDNEYS

Excrete end products of metabolism

Control concentration of body fluids

FUNCTION OF THE KIDNEYS

Erythropoiesis

• Mechanism to speed up production of RBC’s

• Stimulated by oxygen deficiency in the kidney cells

EXTERNAL ANATOMY

Renal Cortex• Outer region of kidney

Three layers of tissue around kidney

• Renal capsule

• Adipose capsule

• Renal fascia

INTERNAL ANATOMY http://medicalimages.allrefer.com/large/kidney-anatomy.jpg

INTERNAL ANATOMY

Parenchyma

• Area of cortex that includes pyramidsNephron

• Functional unit

RENAL BLOODFLOW

20% of blood pumped by the heart each minute enters the kidneys through the renal artery

SUBSTANCES CLEARED FROM THE BLOOD

Excess ions• Sodium is 90% of the positive ions in extracellular

fluid• Increased sodium=increase extracellular osmotic

pressure

• Decreased sodium-decreased extracellular osmotic pressure

• Kidney controls concentration of sodium by regulating amount of water in the body

• Secretion of ADH and thirst

Anti Diuretic Hormone (ADH)

ADH affects the Reabsorption of water in the distal convoluted tubule and collecting duct

Increased ADH = increased Reabsorption of water

Released by posterior pituitary gland via stimulation from the hypothalamus

SODIUM

Primary positive ion in extracellular fluid• Fluids (blood plasma, i.e. intravascular)

Osmoreceptors in hypothalamus• Responsible for maintaining optimal salt and

water balance in the body

• Sense balance of sodium and water concentration in extracellular fluid

SODIUM

Osmoreceptors in hypothalamus (cont)

• Loss of body water• Hypernatremia

• Excess body water• Hyponatremia

SODIUM

Same system can be used in medical treatment to regulate body fluids• Diuretic drug given

• Kidneys excrete sodium

• Osmoreceptors in blood

• Additionally sense lower sodium concentration in the blood

Hypertension is an early sign of renal failure

POTASSIUM

Normal 3.5-5 mEq/L• Primary intracellular cation

• Important in maintaining fluid and electrolyte balance in body

Muscle contraction and sending nerve impulses• Action potential

POTASSIUM Hypokalemia

• Potentially fatal

• Accompanies diarrhea/vomiting/increased diuresis

• Symptoms include• Muscle weakness

• Paralytic ileus

• ECG abnormalities (Arrhythmia, Cardiac arrest)

• Decreases reflexes

• Respiratory paralysis

• Alkalosis

May need to replace K whenever diuretics are given

POTASSIUM

Increased potassium• Metabolic acidosis

• Direct stimulation of kidney to transport potassium into urine

• Indirect stimulation of adrenal cortex to produce aldosterone

• Kidney cells transport potassium into urine

CALCIUM

Deficit• Affect bone and tooth formation

Too much• Kidney stones

Long term defect• Osteoporosis

Adults need 100-1300 mg calcium daily

RENAL FAILURE

Decrease in glomerular filtration rate• Increased serum creatinine

Chronic renal failure• Develops slowly w/ few symptoms

• Kidney diseases Acute renal failure

• Rapidly progresses

• Characterized by oliguria

NEPHRON

Functional unit of the kidney

Regulates water and soluable substances• Filtering blood

• Reabsorbing what is needed

• Excreting the rest as urine

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NEPHRON

Eliminate waste Regulate blood volume and pressure Control levels of electrolytes and metabolites Regulate blood Ph Function regulated by endocrine system

• ADH

• Aldosterone• Hormone that governs Na+ Reabsorption in the kidneys

• Parathyroid hormone

NEPHRON Nephron composed of 2 sections

• Renal corpuscle

• Initial filtering component

•Filters out large solutes

•Delivers water and small solutes to renal tubules

• Renal tubule

•Specializes in reabsorption and secretion

NEPHRON

Controls blood concentration and volume• Removing selected amounts of water and electrolytes

Regulate blood pH• Regulates secretion of H+ and reabsorption of HCO3

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Remove toxic wastes from blood• Remove materials from the blood

• Return materials the body requires

• Eliminate anything left over

NEPHRON FUNCTION Filtration

• Filters a large portion of plasma through glomerular membrane to nephron tubules

Reabsorption• Movement of substances out of the renal tubules into the blood

capillaries• Fluid flows into tubules

• Unwanted substances pass to urine

• Substances needed by body reabsorbed back into plasma (capillaries)

Secretion• Substances in plasma directly secreted into epithelial cells lining

tubules• Into tubular fluid

***Urine formed by three processes: Filtration ,Reabsorption, secretion

NEPHRON ANATOMY

Kidney composed of approximately 1,000,000 nephrons

Nephron composed of renal tubule and vascular supply• Renal corpuscle

• Cortex of kidney

• Renal tubule• Dips into medulla

RENAL CORPUSCLE

Renal corpuscle contains• Bowman’s capsule

• Glomerulus inside Bowman's capsule

• Site of initial urine formation Glomerular filtrate

• Fluid from the glomerulus to Bowman’s capsule• Composition of fluid almost same as plasma

• No significant amount of protein

• Fluids further processed along the nephron to form urine In the average adult, approximately 125 mL/min

(180 L/day) of fluid is filtered across the glomerulus

PROXIMAL CONVOLUTED TUBULE

Fluid leaves the Bowman’s capsule and flows into the proximal convoluted tubule.

LOOP OF HENLE

Leaves the proximal convoluted tubule and flows into the loop of Henle.

Loop of Henle is part of the nephron and is found in the medulla of the kidney

DISTAL CONVOLUTED TUBULE Cells lining the tubule have numerous mitochondria

• Allows active transport to take place Ion transport regulated by the endocrine system

• Parathyroid hormone• Reabsorbs more calcium• Excretes more phosphate

• Aldosterone• Reabsorbs sodium• Excretes more potassium

COLLECTING DUCTS

Begins in the renal cortex Extends deep into medulla

• Urine passes by medullary interstitium

• hypertonic

Collecting duct will become permeable to water in presence of ADH• Can reabsorb as much as ¾ water by osmosis

*** Collecting duct not considered part of the full nephron

THE JOURNEY CONTINUES

Lower portions of collecting duct permeable to urea

Urine leaves through the renal papilla• Into the renal calyces

• Renal pelvis

• Ureter

• Bladder

• Urethra

Start to Finish

Glomerulus Proximal convoluted tubule Loop of Henle Distal convoluted tubule Collecting tubule Ureter Urinary bladder Urethra

FORCES CONTROLLING FLUID EXCHANGE

Glomerular filtration rate (GFR)• Quantity of glomerular filtrate formed each

minute in all nephrons of both kidneys• Normal is 125 mL/min (180 liters/day)

FORCES CONTROLLING FLUID EXCHANGE

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