McCance Chapter 38 Structure and Function of the Renal and Urologic Systems

Sodium-glucose cotransporter 2

Reabsorbs glucose in the proximal tubule, when plasma glucose concentrations exceed a threshold, the SGLT2 becomes saturated and glucose appears in the urine

Capsule

Thin membranous sheath that covers the outer surface of each kidney, composed of tough collagen and elastin fibers

Hilum

Medial indentation for the entry and exit for the renal blood vessels, nerves, lymphatic vessels, and ureter.

Cortex

Outer layer of the kidney that contains the glomeruli, most of the proximal tubules, and some segments of the distal tubule

Medulla

Inner layer of the kidney and consists of regions called the pyramids

Calyces

Apexes of the pyramids project into minor and then major cup-shaped cavities

Renal columns

Extensions of the cortex and lie between the pyramids and extend to the renal pelvis.

Renal papilla

Transports urine from the collecting ducts to the minor calyces

Renal pelvis

Formed from major calyces and connects to the proximal end of the ureters

Ureter

Transports urine from the kidneys to the bladder and is lined with epithelial and smooth muscle cells that contract to move urine to the bladder

Lobe

Composed of a pyramid and the overlying cortex (~14 in each kidney)

Renal arteries

Branches of the abdominal aorta and divide into anterior and posterior branches at the renal hilum

Interlobar artery

Travel down renal columns and between pyramids to form afferent glomerular arteries

Glomerular capillaries

Arise from the afferent arteriole to form four to eight vessels that are arranged in a fist-like structure, empty into the efferent arterioles

Peritubular capillaries

Surround convoluted portions of the proximal and distal tubules and the loop of Henle

Vasa recta

Network of capillaries that forms loops and closely follow the loops of Henle, only blood supply to the medulla and are important for formation of concentrated urine

Renal veins

Follow the arterial path in reverse direction with the same names and empty into the inferior vena cava

Micturition

Urination reflex from contraction of the smooth muscle in the bladder and relaxtion of the internal and external urethral sphincters, stimulated by mechanoreceptors when the bladder is stretched

Detrusor muscle

Smooth muscle fibers in the bladder

Trigone

Smooth triangular area lying between the openings of the two ureters and the urethra

Transitional epithelium

Layers of cells slide past each other and become thinner as the volume of the bladder increases

Uroepithelium

Lines the urinary tract from the renal pelvis to the urethra, barrier to prevent movement of water and solutes between the urine and the blood, communicates information about luminal pressure and urine composition to surrounding nerve and muscle cells

Urethra

Extends from the inferior side of the bladder to the outside of the body

Internal urethral sphincter

Ring of smooth muscle forms the at the junction of the urethra and bladder

External urethral sphincter

Striated skeletal muscle and is under voluntary control

Prostatic urethral segment

Closest to the bladder and passes through the prostate gland, contains the openings of the ejaculatory ducts

Membranous urethral segment

Passes through the floor of the pelvis

Penile urethral segment

Surrounded by the corpus spongiosum (erectile tissue) and contains the openings of the bulbourethral glands

Parasympathetic fibers

Contribute to bladder contraction and urine emptying, arise from the sacral levels of the spinal cord (S2 to S4)

Sympathetic fibers

Inhibit the bladder body and excite the lower bladder and proximal urethral sphincter to retain urine, originate from T11 (thoracic) to L2 (lumbar) vertebrae

Bowman's capsule

Receives filtrate from the glomerulus

Glomerular Filtration Rate

Filtration of the plasma per unit of time and directly related to renal blood flow

Tubuloglomerular feedback

GFR in an individual nephron increases or decreases in relation to changing arterial pressure

Macula densa cells

Located in the distal tubule and sense the increasing or decreasing amounts of filtered sodium.

Juxtaglomerular cells

Renin-releasing cells located around the afferent arteriole where it enters the glomerulus

Renin

Enzyme formed and stored in granular cells of the afferent arterioles of the juxtaglomerular apparatus, converts angiotensinogen (liver) to angiotensin I, released in response to a decrease in blood pressure, decreased sodium in the distal convoluted tubule and sympathetic stimulation of beta adrenergic receptors in juxtaglomerular cells

Angiotensin-converting enzyme

Produced from the pulmonary and renal endothelium, cleaves angiotensin I into angiotensin II

Angiotensin II

Potent vasoconstrictor, stimulates secretion of aldosterone by the adrenal cortex, stimulates thirst

Aldosterone

Hormone, sodium absorption and potassium secretion in the later segment of the distal tubule and collecting duct

Renalase

Hormone released by the kidney and heart that participates in blood pressure regulation

Atrial Natriuretic Peptide

Inhibits sodium and water reabsorption by kidney tubules, inhibits secretion of renin and aldosterone, vasodilates the afferent arterioles, constricts the efferent arterioles, increases urine formation, decreases blood volume and blood pressure.

Brain Natriuretic Peptide

Inhibits sodium and water reabsorption by kidney tubules, inhibits secretion of renin and aldosterone, vasodilates the afferent arterioles, constricts the efferent arterioles, increases urine formation, decreases blood volume and blood pressure.

C-type natriuretic peptide

Secreted from vascular endothelium and in the nephron, vasodilation

Urodilatin

Secreted by the distal convoluted tubules and collecting ducts, vasodilation, increased renal blood flow and urine output

Filtration

Movement of fluid and solutes across the glomerular capillary membrane into the Bowman space

Reabsorption

Movement of fluids and solutes from the tubular lumen to the peritubular capillary plasma

Secretion

Transfer of substances from the plasma of the peritubular capillary to the tubular lumen.

Excretion

Elimination of a substance in the final urine (protein-free fluid).

Renal corpuscle

Glomerulus and Bowman's capsule (filtration)

Glomerulus

Tuft of capillaries that loop into the circular like fingers

Podocytes

Specialized cells with projections (pedicles) that modulate filtration

Vascular epithelial growth factor

Maintains the pores in the Bowman's capsule

Nitric oxide

Vasodilator in the Bowman's capsule

Endothelin-1

Vasoconstictor in the Bowman's capsule

Proximal convoluted tubule

Reabsoprtion of sodium (primary), water, chloride, glucose, potassium, amino acids, bicarbonate ions, urea, secretion of hydrogen ions and drugs and their metabolites

Loop of Henle

Thin ascending segment- permeable to ions but not water. Thick ascending segment- actively transports ions into the interstitium and passes urine into the distal convoluted tubule

Distal convoluted tubule

Final adjustments in urine composition

Collecting ducts

Final adjustments in urine composition

Principal cells

Cells in the distal convoluted tubule and collecting ducts, reabsorb sodium and water and secrete potassium

Intercalated cells

Cells in the distal convoluted tubule and collecting ducts, secrete hydrogen and reabsorb potassium

Antidiuretic hormone (Vasopressin)

Released from the posterior pituitary gland, increases the permeability to water in the distal tubule to retain water and prevent dehydration

Urea

Major constituent of urine along with water, end product of protein metabolism

Uromodulin

Most abundant protein in human urine

Oliguria

Diminished excretion of urine, produced in the thick ascending loop, prevents urinary tract infection, protects the uroepithelium from injury and protects against kidney stone formation

Syndrome of Inappropriate Antidiuretic

Posterior pituitary hypersecretes antidiuretic hormone with excess water reabsorption into the plasma

Diabetes insipidus

Inadequate secretion of antidiuretic hormone causes the distal tubules and collecting ducts to become impermeable to water with excretion of dilute and large volume of urine.

Diuretic

Any agent that enhances the flow of urine

Vitamin D

Obtained in the diet or synthesized by the action of ultraviolet radiation, activated in the kidney and liver, necessary for the absorption of calcium and phosphate by the small intestine

Erythropoietin

Produced by the fetal liver and the adult kidney, essential for normal erythropoiesis (production of red blood cells)

Creatinine clearance

Metabolic product of creatine metabolism from muscle, indirect measure of GFR, tubular secretion, tubular reabsorption, and renal blood flow

Blood Urea Nitrogen

Urea is filtered at the glomerulus and reabsorbed by the blood through the permeable tubules, levels increase as glomerular filtration drops and rise in states of dehydration and acute and chronic renal failure when passage of fluid through the tubules is slowed.

Turbidity

Cloudy urine from formed substances (crystals, blood cells, or casts)

Specific gravity

Estimated measure of the solute concentration

Urine sediment

Examined microscopically and may contain cells, casts, crystals, and bacteria

Hematuria

Large number of red cells are present in the urine and can occur with the administration of anticoagulants and with several renal diseases

Casts

Accumulations of cellular precipitates that originate in the renal tubules, indicate bleeding (RBC), inflammation (WBC) or degeneration of the tubular lumen or necrosis of the renal tubules (epithelial cells)

Crystals

May indicate inflammation, infection, or a metabolic disorder exs. uric acid, calcium oxalate phosphate

Pyuria

White blood cells in the urine