Renal and Body Fluids Physiology (PIO212) Practice Flashcards

These flashcards cover the essential concepts of renal physiology, body fluid compartments, acid-base balance, and the mechanisms of urine concentration and micturition.

Renal Physiology

The study of the functions and processes of the kidneys, which are bean-shaped organs in the lower back.

Erythropoietin

A hormone produced by the kidneys that stimulates the production of red blood cells.

Glomerular Filtration

The process by which the kidneys filter waste and excess fluids from the blood into the Bowman's capsule.

Tubular Reabsorption

The process of reabsorbing essential nutrients, electrolytes, and water from the renal tubules back into the bloodstream.

Tubular Secretion

The process of secreting waste products and excess substances from the bloodstream into the urine.

Hilum

A narrow, vertical slit on the medial surface of the kidney where the renal artery, vein, and ureter enter and exit.

Renal Cortex

The outer layer of the kidney containing renal corpuscles and convoluted tubules.

Renal Medulla

The inner layer of the kidney containing renal pyramids and collecting ducts.

Renal Corpuscle

The functional unit of the kidney consisting of a glomerulus surrounded by a Bowman's capsule.

Podocytes

Specialized visceral epithelial cells lining the Bowman's capsule that have foot processes and a slit diaphragm for filtration.

Glomerular Filtration Rate (GFR)

The volume of fluid filtered from the renal glomerular capillaries into the Bowman's capsule per unit time.

Normal Adult GFR

$$120-130\,mL/min$$

Kidney Failure GFR

A GFR of less than $30\,mL/min$

Clearance

The volume of plasma from which a substance is completely removed by the kidneys per unit time.

Clearance Formula

$$C = \frac{Urine\,concentration \times Urine\,flow\,rate}{Plasma\,concentration}$$

Inulin Clearance

A measure used to determine GFR because inulin is filtered but neither reabsorbed nor secreted.

Transcellular Route

A route of reabsorption where substances move through the cell's apical and basolateral membranes.

Paracellular Route

A route of reabsorption where substances move through the tight junctions and intercellular spaces between cells.

Renal Blood Flow (RBF) Regulation

Regulated by renal sympathetic nerves (constriction), Angiotensin II (constriction), and Atrial natriuretic peptide (dilation).

Intracellular Fluid (ICF)

Fluid located within cells, accounting for approximately $40\%$ of total body weight.

Extracellular Fluid (ECF)

Fluid located outside cells, accounting for approximately $20\%$ of total body weight, including plasma and interstitial fluid.

Bicarbonate Buffer System

A critical ECF buffer consisting of carbonic acid ($H_2CO_3$) and bicarbonate ions ($HCO_3^-$).

Phosphate Buffer System

An important buffer in the ICF and renal tubular fluids consisting of dihydrogen phosphate and hydrogen phosphate ions.

Hemoglobin

The most effective protein buffer and major buffer in the blood, with six times more buffering capacity than plasma proteins.

Metabolic Acidosis

A clinical disturbance characterized by low $HCO_3^-$ caused by conditions like diabetic ketoacidosis or renal failure.

Respiratory Acidosis

A clinical disturbance characterized by high $PCO_2$ often caused by hypoventilation in COPD or asthma.

Countercurrent Multiplier

The division of the countercurrent system formed by the loop of Henle responsible for developing the medullary hyperosmolarity gradient.

Countercurrent Exchanger

The division of the countercurrent system formed by the vasa recta responsible for maintaining the medullary gradient.

Antidiuretic Hormone (ADH)

A hormone that stimulates water reabsorption in the collecting ducts by activating urea transporters $UTA1$ and $UTA3$.

Aldosterone

A hormone that stimulates sodium reabsorption in the collecting duct to regulate electrolyte balance.

Micturition

The process of urinating, involving coordinated contraction of the detrusor muscle and relaxation of the urethral sphincters.

Parasympathetic (Pelvic) Nerve

Known as the 'nerve of emptying,' it causes contraction of the detrusor muscle and relaxation of the internal sphincter.

Sympathetic (Hypogastric) Nerve

Known as the 'nerve of filling,' it causes relaxation of the detrusor muscle and constriction of the internal sphincter.

Pudendal Nerve

The nerve responsible for the voluntary control of the external urethral sphincter during micturition.

Nephrotic Syndrome

A condition characterized by excessive loss of protein in the urine due to damage to the glomeruli.

Indicator Dilution Method Formula

$V = \frac{M}{C}$ where $V$ is volume, $M$ is mass of marker injected, and $C$ is concentration in the sample fluid.

Deuterium Oxide

A marker substance used to measure total body water volume.

Inulin Space

A term for ECF volume measured by using inulin, which passes through capillaries but does not enter cells.

Osmolality

The number of particles (osmoles) per kilogram of solution.

Osmolarity

The number of particles (osmoles) per litre of solution.