Urinary System Flashcards
Renal system and circulating blood:
Normal adult 5-6 liters, filtered 60 x a day
What are the major structures?
Kidneys x 2: Left and right, left is slightly higher, filters and produces urine
Ureters x 2: Receive urine from kidneys, carries urine to the bladder via gravity and peristalsis (involuntary contraction of longitudinal muscles)
Bladder: Receives and stores urine
Urethra: Carries urine from the bladder to the external environment
Functions of the urinary system?
Moves blood volume through kidneys, filters blood plasma, conserves valuable nutrients, regulates blood volume and pressure, regulates blood pH and glucose levels, releases hormones, regulate acid balance
Location and connective tissue of the kidney?
Location: Sits either side of the vertebral column, kidney is slightly superior to the right, Retroperitoneal (sits behind the peritoneum)
Tissues (3):
Fibrous capsule: Entirely covered by a capsule of collagen fibers
Perinephric/ perirenal fat: A thick cushioning layer of adipose tissue
Renal fascia; A dense fibrous layer that anchors the kidney to surrounding structures
What is the superficial anatomy of the kidney?
Hilum: Entry/ exit point for renal artery, renal nerves, renal vein and ureter
Renal Artery: Large in diameter, supplies kidney with 20% resting cardiac output to be filtered
Renal vein: Takes blood out of the kidney
Ureter: Takes urine to the bladder
Internal anatomy of the kidney?
Renal cortex: Outermost, 1cm of kidney, filtration and reabsorption of, waste products
Renal Medulla: 2-3 cm region below cortex, regulates the concentration of urine
Renal sinus: A central cavity that contains structures such as renal pelvis, renal calyces, blood vessels, fat
Function: Ureters, bladder Urethra
Ureters: Muscular tubes connecting kidneys to bladder, 25-30cm, attached to the posterior abdominal wall, mucosa allows for expansion, muscularis facilitates peristalsis (movement of urine)
Bladder: Stores urine, sphincters control urine flow (internal= involuntary, External= voluntary)
Urethra: Transports urine from bladder to exterior of the body, 20-25 cm in males (transports urine and semen), 4cm in females (transports urine)
What is micturition (urination)?
Urine reaches the bladder by peristaltic contraction of the ureters, when full stretch receptors in the bladder wall trigger the micturition reflex (often around 200ml). At 500ml muscle contractions force the internal urethral sphincter
What is the Micturition reflex?
Detrusor muscle (surrounding the bladder) contracts in response to a full bladder (involuntary), external urethral sphincter relaxes (voluntary), urine flows through the urethra and out of the body
What do nephrons do in the urinary system?
1 million nephrons per kidney and are the functional unit.
Cortical nephrons (85%) located entirely in the renal cortex allows for excretion of waste products and urine
Juxtamedullary nephrons (15%) have long nephron loops that extend deep into the renal medulla and creates concentrated urine
Has an afferent and efferent pathway, sits in a cup structure called the bowman’s structure as the kidneys jobs is to stop large things going out of the blood and into the tubule e.g. large proteins and glucose
What are some key terms?
Filtration: Fluid and waste leaving circulation and entering nephron, what the net does to stop big things from getting into the urine
Filtrate: Name of fluid once in nephron (after being filtered)
Secretion: waste ions leaving vessels, enter tubule (post filtration)
Reabsorption: Fluid and molecules returned to plasma (circulation)
Excretion: discharge of urine from the body
What is the filtration membrane?
Stops large proteins and cell platelets from getting through. Allows water, small proteins, amino acids, glucose, waste solutes
What is the anatomy of the nephron?
Renal corpuscle:
- Where water and dissolved solutes are pushed out of the blood and into the renal tubule
- Site of blood filtration
Diuretic act on different sections of this pipe, as a practitioner, if they are on medication the treatment may impact this
Renal Tubule:
- Where the components of the filtrate are altered (via secretion and absorption)
- Site of filtration modification
- Goes down into the renal medulla
- Main area where we reabsorb fluid, and if it doesn’t work we can absorb fluid back into the bloodstream
- We export salt so the medulla stays salty
Proximal convoluted tubule (PCT):
- Beginning of the renal tubule
- Reabsorption of essential substances from the filtrate back into the blood
- Cells have microvilli to aid reabsorption
Loop of Henle:
- Middle segment of the renal tubule
- Descending and ascending portions
- Descending = reabsorption of water
- Ascending = reabsorption of Na+ and CI= from the filtrate
Distal Convoluted Tubule (DCT)
- Last segment of the renal tubule
- Only 15-20% of initial filtrate volume reaches the DCT
Adjust filtrate composition via reabsorption and secretion
Collecting system:
- Tubular fluid (urine) from each nephron empties into the collecting system (minor calyces)
- Last passage to transport to the bladder
What is the Glomerular Filtration Rate (GFR)?
The rate which filters blood through kidneys, measure of renal performance (too slow=not enough clearance, too fast= not enough reabsorption), it is a homeostatic response to fasten or slow
What are;
Urine
Urea
Creatinine
Uric Acid
Urine: Metabolic waste products
Urea: a by-product of amino-acid breakdown
Creatinine: generated in skeletal muscle tissue through the breakdown of creatine phosphate
Uric acid: a by-product of recycling the nitrogenous bases of RNA
molecules
