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Urinary system

urinary bladder, a temp storage reservoir for urine, plus three tubelike organs (the paired ureters and the urethra).

Location of Kidneys

bean shaped, lie retropertioneal position in the superior lumbar region. Extending approx from T1-T2. Receive protection from the lower part of the rib cage. Right kidney is slighter than the left due to the liver. Avg size of a bar of soap.

Renal hilum

medial surface is concave and has a vertical cleft that leads into an internal space within the kidney.

Three supportive tissue around each kidney

Renal fascia (outer, anchors), Perirenal fat capsule (fat cushions it), and fibrous capsule (transparent prevents infections).

Renal cortex

most superficial region is light in color and has a granular appearance.

Renal medulla

deep to the cortex, darker reddish brown, which exhibits cone shaped tissue masses called medullary or renal pyramids.

Renal pyramids

appear striped because they are formed almost entirely of parallel bundles of microscopic urine-collecting tubules and capillaries.

Renal columns

inward extensions of cortical tissue, separate the pyramids

Lobes

Each pyramid and its surrounding cortical tissue constitutes one of approx eight of these.

Renal pelvis

a funnel shaped tube is continuous with the ureter leaving the hilum.

Renal arteries

Kidneys continuously cleanse the blood and adjust its composition, therefore they have a rich blood supply. under normal conditions they deliver one-fourth of the total cardiac output to the kidneys each minute.

segmental arteries

As each renal artery approaches a kidney, it divides into five segments.

Interlobar arteries

Within the renal sinus, each segmental artery branches further to for several of these.

Arcuate arteries

At the medulla-cortex junction, the interlobar arteries branch into these, they arch over the bases of the medullary pyramids.

Cortical radiate arteries

very small, radiate outward from the arcuate arteries to supply the cortical tissue.

Renal plexus

a variable network of autonomic nerve fibers and ganglia, provides the nerve supply of the kidney and its ureter.

Nephrons

the structural and functional units of the kidneys. Each kidney contains over 1 million of these tiny blood-processing units which carry out the processes that form urine.

glomerulus

Each nephron consists of a ( ) which is a tuft of capillaries and a renal tubule.

Podocytes

The visceral layer, which clings to the glomerular capillaries, consists of highly modified branching epithelial cells.

Collecting ducts

each of which receives filtrate from many nephrons, run through the medullary pyramids and give them their striped appearance.

Foot processes

The octopus-like podocytes terminate in here, which intertwine as they cling to the basement membrane of the glomerulus.

Filtration slits

the clefts or openings between the foot processes.

Capsular space

Through filtration slits, filtrate enters the capsular space inside the glomerular capsule.

The remainder of the renal tube has three major parts..

Proximal convoluted tubule (PCT)-coiled, Lopp of Henle-makes a hairpin loop, distal convoluted tubule (DCT)-winds and twists.

Cortical nephrons

represent 85% if the nephrons in the kindneys.

Juxtamedullary nephrons

the remaining originate close to the cortex-medulla junction, and they play an important role in the kidneys ability to produce concentrated urine.

vasa recta

bundles of long straight vessels that extend deep into the medulla paralleling the longest loop of Henle.

Juxtaglomerular apparatus (JGA)

each nephron has a region, where the most distal portion of the ascending limb of the loop of Henle lies against the afferent arteriole feeding the glomerulus.

Macula densa

a group of tall, closely packed cells of the ascending limb of the loop of Henle that lies adjacent to the granular cells. Chemoreceptors that respond to changes in in the NaCl content of the filtrate. Interconnected by gap junctions

Filtration membrane

Lies between the blood and the interior of the glomerular capsule. A porous membrane that allows free passage of water solutes smaller than plasma proteins.

urine formation involves three major processes..

glomerular filtration by the glomeruli, and tubular reabsorption and tubular secretion in the renal tubules.

Urine

Contains mostly metabolic wastes and unneeded substances. The kidneys process about 180 L of blood-devrived fluid daily.

Step 1- Glomerular filtration

a passive process in which hydrostatic pressure forces fluids and solutes thorough a membrane.

Net filtration pressure (NFP)

responsible for filtrate formation, involves forces acting at the glomerular bed.

Glomerular hydrostatic pressure (HPg)

essentially glomerular blood pressure, the chief force pushing water and solutes out of the blood and across the filtration membrane.

Glomerular filtration rate (GFR)

The volume of filtrate formed each minute by the combined activity of all 2 million glomeruli of the kidneys.

Step 2- Tubular reabsorption

Our total plasma volume filters into the renal tubules about every 22 minutes, so all our plasma would be drained away as urine in less than 30 min were it not for the fact that most of the tubule contents are quickly reclaimed and returned to the blood. A selective transepithelial process that begins as soon as the filtrate enters the proximal tubules.

Sodium reabsorption

Sodium ions are the single most abundant cation in the filtrate, and about 80% of the energy used for active transport is devoted to their reabsorption. Almost always active and via the transcellular route.

Secondary active transport

The push comes from the gradient created by Na+ -K+ pumping the basolateral membrane. Include glucose, amino acids, lactate, and vitamins.

Transport maximum (Tm)

For nearly every substance that is reabsorbed using transport protein in the membrane. The Tm reflects the number of transport proteins in the renal tubules available to ferry each particular substance.

Passive tubular reabsorption

Encompasses osmosis, diffusion, and facilitated diffusion, substances move down their electrochemical gradients without the use of ATP.

Step 3- Tubular secretion

The failure of tubule cells to reabsorb some solutes is an important way of clearing plasma of unwanted substances. The way is essentially reabsorption in reverse.

Tubular secretion is important for...

Disposing of substances, such as certain drugs and metabolites that are tightly bound to plasma proteins, eliminating undesirable substances or end products that have been reabsorbed by passive processes, ridding the body of excess K+, and controlling the blood pH.

Osmolality

Crucial renal function is to keep the solute concentration of body fluids constant. We use this to measure the amount of solutes in body fluids. The number of solute particles dissolved in 1 kg of water and reflects the solution's ability to cause osmosis.

Concurrent multiplier

est. the osmotic gradient because of two factors.. The descending limb of the loop of Henle is relative impermeable to solutes and freely permeable to water and the ascending limb is permeable to solutes, but not to water.

Urochrome

Freshly voided urine is pale to deep yellow. The yellow color is due to " " a pigment that results form the body's destruction of hemoglobin. The more concentrated, the deeper yellow.

Urine

pH around 6 with a slightly aromatic scent, if allowed to stand develops an ammonia odor.

specific gravity

the ratio of the mass of a substance to the mass of an equal volume of distilled water.

Nitrogenous wastes

in urine include uric acid (an end product of nucleic acid metabolism) and creatine (a metabolite of create-phosphate, which stores energy for the regeneration of ATP and is found in large amounts in skeletal muscle tissue.

Ureters

Slender tubes that convey urine from the kidneys to the bladder.

Three layers of the Ureter

The transitional epithelium of its lining mucosa is continuous with that of the kidney pelvis superiorly and the bladder medially. The middle= muscularis; composed of two smooth muscle sheets (internal longitudinal layer and external circular layer). The external longitudinal layer appears in the lower third ureter. External surface=adventitia.

Urinary Bladder

Smooth, collapsible, muscular sac that store urine temporarily . Located on the pelvic floor just posterior to the pubic symphysis.

male bladder

prostate lies inferior to the bladder neck, which empties into the urethra.

female bladder

anterior to the vagina and uterus.

Trigone

The smooth triangular region of the bladder base outlined by three openings. Important clinically because infections tend to persist in this region.

Detrusor muscle

Muscular layer, consists of intermingled smooth muscle fibers arranged in inner and outer longitudinal layers and a middle circular layer.

Urethra.

A thin walled muscular tube that drains urine from the bladder and conveys it out of the body.

Micturition

referred to as urinating, the act of emptying the urinary bladder.

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