Chapter 24 Urinary System terms

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Chapter 24 Urinary System Vocabulary words

Retroperitoneal space

space posterior to parietal peritoneum where the kidneys are located/positioned

Parenchyma

The functioning tissue of the kidney.

Renal medulla

The inside layer of the parenchyma.

Corticomedullary junction

Where the cortex and renal pyramid base meets.

Fibrous capsule

directly adhered to the external surface of the kidney; composed of dense irregular connective tissue and maintains the kidney's shape, protects it from trauma, and helps prevent infectious pathogens from penetrating the kidney

Perinephric fat

external to the fibrous capsule; contains adipose connective tissue; provides cushioning and support for the kidney

Renal fascia

external to the perinephric fat; composed of dense irregular connective tissue; anchors kidney to surrounding structures

Paranephric fat

outermost layer surrounding the kidney; composed of adipose connective tissue and provides cushioning and support for the kidney

Renal columns

extensions of the cortex, project into the medulla and subdivide it into renal pyramids

Renal pyramids

appear striated or striped; an adult kidney typically contains 8-15

Corticomedullary junction

the wide base of the renal pyramid that lies at the external edge of the medulla where it meets the cortex

Renal papilla

tip of the renal pyramid

Renal lobes

consists of a renal pyramid, portions of renal columns adjacent to either side of the renal pyramid, and the renal cortex external to the pyramid base

Renal sinus

medially located space; serves as a urine drainage area; organized into minor calyces, major calyces, and a renal pelvis

Nephron

microscopic,functional filtration unit of the kidney; each consists of two major structures: renal corpuscle and renal tubule

Renal corpuscle

an enlarged, bulbous region of a nephron housed within the renal cortex; composed of two structures: glomerulus and glomerular capsule

Glomerulus

a thick tangle of capillary loops called glomerular capillaries

Afferent arteriole

where blood enters the glomerulus

Efferent arteriole

where blood leaves the glomerulus

Glomerular capsule

(Bowmans capsule) formed by two layers: an internal permeable visceral layer that directly overlies the glomerular capillaries and an external impermeable parietal layer composed of simple squamous epithelium

Capsular space

the space between the viseral layer and the parietal layer that receives the filtrate

Vascular pole

where afferent and efferent aterioles attach to the glomerulus

Tubular pole

where the renal tubule originates

Renal tubule

makes up remaining part of the nephron and consists of three continuous parts: proximal convoluted tubule, the nephron loop, and the distal convoluted tubule

Proximal convoluted tubule (PCT)

first region of renal tubule; originates at the tubular pole of the renal corpuscle and is composed of a simple cuboidal epithelium with tall, apical microvilli that markedly increase its surface area and thus its reabsorption capacity

Nephron loop

originates at a sharp bend in the PCT; has two limbs: descending limb and ascending limb that connect at a hairpin turn withing the medulla

Descending limb

extends medially from the PCT to the tip of the nephron loop

Ascending limb

Returns to the renal cortexand terminates at the DCT

Distal convoluted tubule (DCT)

originates at the renal cortex at the end of the nephron loop and extends to the collecting tubule

Cortical nephrons

85% of nephrons; oriented with their renal corpuscles near the peripheral edge of the cortex and have a relatively short nephron loop that barely penetrates the medulla

Juxtamedullary nephrons

15% of nephrons; renal corpuscles lie adjacent to the corticomedullary junction and they have relatively long nephron loops that extend deep into the medulla

Collecting tubule

where the nephron drains; each kidney contains thousands of them that empty into collecting ducts; both collecting tubules and collecting ducts project medially through the renal medulla toward the renal papilla

Papillary duct

where collecting ducts empty into, located within the renal papilla

Principle cells

responsive to hormones aldosterone(released from the adrenal cortex) and antidiuretic hormone (released from the posterior pituitary)

Intercalated cells

specialized epithelial cells that help regulate urin pH and blood pH

Juxtaglomerular apparatus

important structure in regulating filtrate formation and blood pressure

Granular cells

modified smooth muscle cells of the afferents ateriole located near its entrance into the renal corpuscle; contract when stimulated either by stretch of by the sympathetic division; synthesize,store, and release renin enzyme

Renin

required in the production of angiotensin II hormone

Macula densa

a group of modified epithelial cells in the wall of the DCT where it contacts the granular cells; detect changes in the sodium chloride (NaCl) concentration of fluid within the lumen of the DCT; signal granular cells to release renin throughparacrine stimulation

Renal artery

how blood is delivered to the kidney

Filtrate

the materials that pass through a filter

Tubular fluid

fluid that enters the PCT, nephron loop, and DCT

Urine

fluid and disolved substances excreted by the kidney

Filtration

seperates some water and dissolved solutes from the blood plasma in the glomerular capillaries; water and solutes enter into the capsular space of the renal corpuscle due to pressure differences across the filtration membrane

Tubular reabsorption

occurs when components within the tubular fluid move by diffusion, osmosis, or active transport from the lumen of the renal tubules, collecting tubules, and collecting ducts across their walls and return to the blood within the peritubular capillaries and vasa recta. Generally all vital solutes and most water that was in filtrate is reabsored while excess solutes, and some water , and waster products remain within the tubular fluid

Tubular secretion

movement of solutes, usually by active transport, out of the blood within the peritubular and vasa recta capillaries into the tubular fluid. Materials are moved selectively into the tubules to be eliminated or excreted from the body

Filtration membrane

a porous, thin, and negatively charged structure that is formed by the glomerulus and visceral layer of the glomerular capsule; composed of three sandwhich layers

Endothelium of glomerulus

fenestrated; allows plasma and its dissolved substances to be filtered, while restricting the passage of large structures

Basement membrane of glomerulus

porous basement membrane composed of glycoprotein and protoglycan molecules; restricts the passage of large plasma proteins while allowing smaller structures to pass through

Visceral layer of glomerulus

composed of specialized cells called podocytes, these have long foot like processes called pedicels that wrap around the glomerular capillaried to support the capillary wall but do not completley ensheathe it. The pedicels are seperated by thin spaces called filtration slits that are covered with membrane. Pedicels of one podocyte interlock with pedicels of a different podocyte, similar to how your fingers interlock. The filtrarion slits restrict the passage of most small proteins

Mesangial cells

specialized cells positioned within and between the capillary loops of the glomerulus; have phagocytic and contractile properties

Glomerular hydrostatic pressure (HPg)

blood pressure in the glomerulus; the driving force that pushes water and some dissolved substances out of the glomerulus into the capsular space of the renal corpuscle; promotes filtration

blood colloid osmotic pressure(OPg)

osmotic pressure exerted by the blood due to the dissolved solutes it contains; opposes filtrations because it tends to pull or draw fluid back into the glomerulus

Capsular hydrostatic pressure (HPc)

pressure in the glomerular capsule due to the amount of filtrate already within the capsular space; the presence of this filtrate impedes the movement of additional fluid from the blood into the capsular space and thus it also opposes filtration

Net filtration pressure (NFP)

difference in the glomerular hydrostatic pressure,blood colloid pressure, and capsular hydrostatic pressure

Glomerular filtration rate (GFR)

an important variable influenced by net filtration pressure; the rate at which the volume of filtrate is formed, and is expressed as volume per unit time

Intrinsic control

within the kidney itself; maintains GFR at a normal level

Extrinsic control

external to the kidney; involve neural of hormonal regulation; may decrease or increase GFR

Renal autoregulation

the intrinsic ability of the kidney to maintain a constant blood pressure and glomerular filtration rate despite changes in the systemic arteriole pressure

Myogenic mechanism

involves contractions and relaxation of smooth muscle in the wall of the afferent ateriole;a decrease in systemic blood pressure results in lower volume of blood entering the afferent arteriole, reducing the stretch of the arteriole wall. vessel relaxes, resulting in vasodilation, allows more blood into glomerulus, which compensates for the lower systemic blood pressure, glomerular blood pressure and GFR remain normal

Tubuloglomerular feedback mechanism

based on detection of NaCl levels in tubular fluid; if myogenic mechanism is not sufficient enough then there is an increase in amount of NaCl remaining in the tubular fluid, an increase in NaCl is detected by macula densa cells, macula densa cells release a signaling molecule that binds to , and stimulates the afferent wall, GFR returns to normal

Paracellular (intercellular) transport

Substances pass between the epithelial cells of the tubular wall

Transcellular transport

substances move through the epithelial cells

Luminal membrane

in contact with the tubular fluid

Basolateral membrane

rests on the basement membrane

Transport maximum (Tm)

the maximum amount of a substance that can be reabsorbed across the tubule epithelium in a given period of time

Renal threshold

the maximum plasma concentration of a substance that can be carried in the blood without eventually appearing in the urine

Aldosterone

a steroid hormone produced by the adrenal cortex; stimulates protein synthesis of NA+ channels and Na+/K+ pumps

Atrial natriuretic peptide (ANP)

inhibits both the reabsorbtion of Na+ in the PCT and collecting tubules and the release of aldosterone; increases GFR to eliminate fluid; occurs when there is either an increase in blood volume return or an increase in blood pressure; relaxes the afferent arteriole and inhibits the release of renin from the granular cells to cause relaxation of the mesangial cells to increase filtration membrane surface area

Aquaporins

a water transporter protein

Obligatory water reabsorption

the movement of water out of the PCT follows Na+ by osmosis; dependent upon the movement of Na+ so the water is "obliged" to follow Na+

Facultative water reabsorption

tubular reabsorption in the response to ADH

Antidiuretic hormone (ADH)

increase water reabsorption from the filtrate into the blood, resulting in the production of a smaller volume of a more concentrated urine

Urea

small, water-soluble molecule produced from protein breakdown in the liver

Uric acid

produced from nucleic acid breakdown primarily in the liver

Creatinine

produced from the metabolism of creatine in muscle tissue

Countercurrent multiplier

involves the nephron loop and is partially responsible for establishing the salt concentration gradient within the interstitial fluid

Countercurrent exchange system

the process by which the vasa recta help maintain the concentration gradient

Renal plasma clearance

measures the volume of plasma that can be completely cleared of a substance in a given period of time-usually 1 min

Specific gravity

the density of a substance compared to the density of water

Urinoid

normal smell of fresh urine

Ureters

long, endothelial-lined, fibromuscular tubes that conduct urine from the kidneys to the urinary bladder

Adventitia

External layer of ther ureter wall

Urinary bladder

an expandable, muscular container that serves as a reservoir for urine

Trigone

posteroinferior triangular area of the urinary bladder wall

Mucosal folds

allow for even greater distension

Mucosa

lines the bladder lumen

Submucosa

immediately external to the mucosa and supports the urinary bladder wall

Urethra

an epithelial-lined fibromuscular tube that exits the urinary bladder through the urethral opening from its anteroinferior surface and conducts urine to the exterior of the body

Internal Urethral sphincter

the incoluntary, superior sphincter; composed of smooth muscle and surrounds the neck of the bladder, controlled by tthe autonomic nervous system

External urethral sphincter

infereior to the internal urethral sphincter and is formed by skeletal muscle fubers of the urogenital diaphragm; a voluntary sphincter controlled by the somatic nervous system

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