Kidney Function and Anatomy Quiz

Renal System Overview

• The renal system, also known as the urinary system, is responsible for filtering blood and producing urine.
• The primary organs of the system are the kidneys.
• The kidneys filter waste products from the blood, regulate blood volume, maintain the balance of water and salts, and control the balance between acids and bases.
• Kidneys also produce renin, regulate blood pressure and release erythropoietin, and convert vitamin D into its active form.
• The system also includes ureters, urinary bladder, and urethra, which are essential for transporting and excreting urine

Intended Learning Outcomes

• Describe the location of urinary system organs.
• Identify kidney structure.
• Describe nephrons.
• Describe urine formation.
• Understand the role of kidneys in maintaining blood composition.

Kidney Functions

• Filter fluid from the bloodstream.
• Produce urine containing waste products.
• Regulate blood volume.
• Maintain the proper balance between water, salts, acids, and bases.
• Produce renin regulating blood pressure.
• Produce erythropoietin for red blood cell production in bone marrow.
• Convert vitamin D into its active form.

Urinary System Structures

• Kidneys: Located on either side of the vertebral column; responsible for urine formation and regulation of water balance.
• Ureters: Tubes that transport urine from the kidneys to the bladder.
• Urinary Bladder: A reservoir that stores urine until it is expelled from the body.
• Urethra: Tube that carries urine from the bladder out of the body.

Kidney Internal Anatomy

• The kidney has three regions: cortex, medulla, and renal pelvis.
• The renal cortex contains nephrons, the functional units of the kidney.
• The medulla consists of renal pyramids, which funnel the urine into the renal pelvis.
• Renal pyramids and renal columns form the lobes of the kidney.
• The renal pelvis leads to the ureters on the outside of the kidney.
• Major calyces are extensions of the renal pelvis branching into minor calyces.

Nephron Structure

• A nephron is composed of a renal corpuscle and a renal tubule.
• Renal Corpuscle: made of glomerulus (knot of capillaries), glomerular capsule (Bowman's capsule).
• Renal tubule is a series of convoluted tubes that further process the filtrate.

Podocytes

• Podocytes are highly modified cells forming the inner layer of the glomerular capsule.
• Their foot processes make the glomerular membrane a "holey" membrane that enables filtration..

Renal Tubule

• About 3cm long; beginning at the glomerular capsule, it coils and twists forming a hairpin loop.
• The loop, then recoils before entering a collecting duct.

Types of Nephrons

• Cortical nephrons: Located almost entirely within the cortex.
• Juxtamedullary nephrons: Situated close to the cortex-medulla junction; nephron loops extending deep into the medulla.

Collecting Ducts

• Each collects urine from many nephrons.
• Runs downward through the medullary pyramids.
• Deliver the final urine product into the calyces and renal pelvis.

Blood Supply to Nephrons

• Each nephron is associated with two capillary beds: the glomerular capillary bed and the peritubular capillary bed.
• Glomerulus is fed by the afferent arteriole and drains through the efferent arteriole.
• Blood pressure within glomerular capillaries is higher than other capillaries.
• Fluid and small solutes leave the blood into the glomerulus.
• Most of the filtrate is returned to the blood by the renal tubule cells.
• Peritubular capillaries are adapted for absorption, rather than filtration. Absorb substances like water and solutes from the tubule cells.

Urine Formation (Glomerular Filtration)

• Glomerular filtration is a non-selective, passive process.
• Fluid filtered from blood into glomerular capsule is called filtrate..
• Essentially blood plasma without blood proteins.
• Large particles like proteins and blood cells are too large to pass through the filtration membrane.

Glomerular Filtration Rate (GFR)

• Average GFR is approximately 120-125ml/min.
• GFR is relatively constant.
• Can increase if excess body fluid or decrease for fluid conservation.
• Is used to check how well kidneys are functioning

Tubular Reabsorption

• Waste and excess ions are removed from the filtrate.
• Water, glucose, amino acids, and needed ions are reclaimed and transported into the blood.
• Process begins as filtrate enters proximal convoluted tubule (PCT).
• Water is reabsorbed passively.
• Other needed substances reabsorbed actively.
• Most reabsorption occurs in PCT

Tubular Secretion

• Essentially tubular reabsorption in reverse.
• Removal of hydrogen and potassium ions and creatinine.
• Helps control blood pH

Nitrogenous Wastes

• Nitrogenous wastes include urea, uric acid and creatinine.
• Poorly reabsorbed or not at all.
• Present in high concentrations in excreted urine

Urine Facts

• In 24 hours, about 150-180 liters of blood plasma is filtered in the kidneys.
• Healthy individuals produce 1-1.8 liters of urine.
• Urine color varies from clear to yellow-due to urochrome.

Abnormal Urine Constituents

• Abnormal substances in urine (e.g. glucose, proteins, pus, RBCs, hemoglobin, bile).
• Abnormal constituents can occur from various causes; non-pathological and pathological.

Ureters, Urinary Bladder, and Urethra

• Ureters: Slender tubes (25-30cm long, 6mm diameter), transport urine from kidneys to bladder via peristalsis.
• Urinary Bladder: Smooth, collapsible muscular sac storing urine until release.
• Urethra: Thin walled tube carrying urine from bladder to outside the body.
  • Internal urethral sphincter, keeps urethra closed; helps with involuntary control.
  • External urethral sphincter, keeps urethra closed; important for voluntary control.

Micturition

• Process of emptying the bladder.
• Controlled by two sphincters; internal and external urethral sphincters.
• Bladder collects urine to about 200 ml, and nerves activate reflex contractions to release urine.
• When urine collected increases to about 500ml, then reflex starts again.
• Voluntary control has no effect eventually.

Maintaining Fluid, Electrolyte, and Acid-Base Balance

• Kidneys are crucial for keeping blood composition constant by regulating water, electrolytes, and acid-base balance.
• Controlling water balance ensures that we don't lose more water than we take in.
• Electrolyte balance prevents water movement from one compartment to another altering blood volume and blood pressure.
• Acid-base balance maintains blood pH between 7.35 and 7.45 using various mechanisms.

Regulation of RBC Production

• Erythropoietin (EPO) regulates production of mature red blood cells (RBCs) in the bone marrow.
• Hypoxia (low oxygen) stimulates EPO production.

Vitamin D

• Kidneys convert vitamin D into its active form, 1,25(OH)2D, essential for calcium absorption. Vitamin D is initially created in the skin, travels to the liver and the Kidney to produce its active form.

Kidney Disease

• Diabetes, high blood pressure, infection, drugs, and kidney stones can cause kidney disease.
• Some kidney failure types can be treated by dialysis, a treatment that replaces the functions of the kidneys.

Kidney Dialysis

• Process of removing waste and excess fluid from the blood using an artificial kidney machine.
• Blood is collected and filtered through a semi-permeable tube and the waste is removed.
• Dialysis is usually done 3 times a week and each treatment lasts about 5 hours.

Kidney Transplantation

• Kidney transplant is an option for kidney failure patients.
• A donor kidney can either be from a living person or a deceased person (after permission).

Pros and Cons of Kidney Dialysis

• Pros: Facilities are widely available, trained professionals are available, and patients can get to know others.
• Cons: Treatments are fixed, you must travel to the center, strict diet and fluid limits, and need more medications.

Pros and Cons of Kidney Transplant

• Pros: Normal lifestyle (no dialysis), better quality of life.
• Cons: Good tissue match needed, expensive operation, risk of transplant rejection, and daily immunosuppressant drugs.

Summary of Renal System Physiology

• Nephron is the smallest functional unit of the kidney and performs functions of filtration, resorption, and secretion.
• Kidneys help maintain acid-base and fluid balance, regulate electrolytes, eliminate toxins, absorb glucose and amino acids, regulates blood pressure and activate vitamin D (including EPO).

Test your knowledge on the anatomy and functions of the kidneys with this engaging quiz. Topics cover kidney disease, dialysis, and the various structures that make up the renal system. Perfect for students studying biology or health sciences.