Compendium 7 Flashcards
What structures make up the renal system
2 kidneys
2 ureters
Urinary bladder
Urethra
Describe the kidneys
Lie behind parietal peritoneum on posterior abdominal wall on either side of vertebral canal
Considered to be retroperitoneal
Located in abdominopelvic cavity
Right Kinney slightly lower than left due to liver
Lumbar vertebrae and rib cage partially protect kidneys
Adipose tissue engulfs renal capsule and acts as cushioning and to insulate heat
Renal fascia: thin, layer, connective tissue which anchors kidneys to posterior abdominal wall
Explain external anatomy of kidneys
Renal capsule: fibrous, connective tissue surrounding kidneys
Hilum: area with renal vein and artery
Renal artery and vein
Ureter
Explain internal anatomy of kidneys
Hilum: renal artery and nerves enter, renal vein and ureters exit
URETER: exits at hilum, connects to bladder
CORTEX: outer area
MEDULLA: inner ares
RENAL COLUMNS: part of cortical tissue extending from medulla
RENAL PYRAMIDS: where urine production occurs
Top of pyramid is called RENAL PAPILLA
MINOR CALYCES: 8-20 which merge to from 2-3 MAJOR CALYCES
Converge to form renal pelvis
What is a nephron
Functional unit of the kidney
What makes up a nephron
Renal corpuscle (in cortex)
Proximal convoluted tubule (cortex)
Loop of henle (descends into medulla)
Distal convoluted tubule (cortex)
Where does urine flow after nephron
Collecting duct to papillary ducts to minor calyces, major calyces, renal pelvis, ureter
Many distal tubules will drain urine into same collecting duct
What are juxtamedullary nephrons
Renal corpuscle located near medulla
Long loops of henle extend deep into medulla
15% of all nephrons
What are cortical nephrons
Renal corpuscle located nearer to periphery of cortex
Loops of henle don’t extend deep into medulla
85% of all nephrons
What two parts is the renal corpuscle divided into
Glomerulus
Bowmans capsule
Explain glomerulus
Network of capillaries
Blood enters through afferent arteriole and exits through efferent arteriole to return to body
Afferent larger in diameter than efferent as blood enters at higher pressure in order to encourage filtration across capillary walls into capsule
Explain bowmans capsule
Enlarged end of nephron
Double walled chamber
Blood enters at high pressure, it is filtered and then enters proximal tubule
Parietal layer: outer layer, simple squamous, becomes cuboidal in proximal tubule
Visceral layer: inner layer, specialised podocytes that wrap around capillaries and facilitate filtration
Explain podocytes
Filtration membrane
Fenestrae: window like openings in endothelial cells of capillaries so fluid moves into capsule
Filtration slits: gaps between podocytes for leaking
Basement membrane: sandwiched between Endothelial cells of capillaries and podocytes
Explain proximal convoluted tubule
Simple cuboidal epithelium with microvilli
Active reabsorption K, Na, Cl
Large surface area, many mitochondria
80% water reabsorbed here, 100% reabsorption of sugars and amino acids
Explain loop of henle
Has descending and ascending limbs
Thick parts= simple cuboidal, thin parts= simple squamous
Reabsorbs ions and water
Osmosis and diffusion
Explain distal convoluted tubule
Shorter than proximal Simple cuboidal with few microvilli Numerous mitochondria Controlled waste secretions Controls urine concentration by varying water reabsorption
Explain collecting ducts
Large diameter
Extend through medulla towards papilla and then to ureter
Simple squamous epithelium
How does blood flow in to kidney
Heart to kidneys through abdominal aorta
Renal arteries then branch off to each kidney taking blood into hilum through afferent arteriole
How does blood exit kidney
When things are too big to pass through to afferent arteriole they flow to efferent arteriole which takes blood away from glomerulus, them through peritubular capillaries, finally all merge to become left or right renal vein which then both merge to form inferior vena cava
Explain the movement of urine
Pressure forced urine through nephron
Smooth muscle moves urine from renal pelvis to ureters to bladder ureters via peristalsis = constant flow
Ureters enter bladder obliquely and posterior through section called trigone which doesn’t expand when the bladder does this creates pressure which can compresses ureter and prevents backflow
Explain ureter
Bring urine from renal pelvis to bladder
Lined with transitional epithelium to allow for stretch (touches urine)
Epithelium surrounded by mucosa then smooth muscle layer then connective/fatty tissue
Explain bladder
Increases or decreases size based on volume of urine
Transitional epithelium lines inside followed by lamina propria, submucosa, detrusor muscle (smooth muscle, allowing for contraction and expulsion of urine)
Flow to uretha isn’t constant, bladder has to be full to cause increased pressure
Explain urethra
Bladder to outside
Internal urinary sphincter: elastic connective tissue and smooth muscle that prevents urine constantly flowing out of bladder
External urinary sphincter: skeletal muscle surrounding urethra, acts as a valve to control urine flow and can make decisions to relax and let urine out, or contract and keep in
Lined with transitional epithelium at top and stratified columnar epithelium towards opening
Difference between male and female urethra
Males: longer than females
Females: shortness is why women are more prone to urinary tract infections than men
Functions of renal system
Excretion Regulate blood volume and pressure Solute concentration of blood Extracellular pH Red blood synthesis Vitamin D synthesis
What are the three stages of urine formation
Filtration
Tubular reabsorption
Tubular secretion
What occurs in filtration stage
Movement of fluid derived from blood flowing through glomerulus and filtration membrane
Substances moved across membrane into bowmans capsule to be filtered and fluid is now called filtrate
Filtrate contains: water, glucose, amino acids, urea, irate ions, creatinine, some ions
Driven by pressure
What is renal fraction
The part of cardiac output that passes through the kidneys
Varies from 20-30% in a healthy resting adult
What is glomerular filtration rate
Amount of filtrate produced each minute (~180L/day)
99% filtrate reabsorbed
Filtration membrane so important as it allows vital molecules (red blood cells, large molecules) can stay in body transport O2 and toxins can be removed
Explain juxtaglomerular apparatus
Smooth muscle cells of wall of afferent arteriole are called juxtaglomerular cells
Specialised tubule cells form distal convoluted tubule called MACULA DENSA
These secrete RENIN that can travel through blood to act on proteins and organs to reduce urine volume
Explain tubular reabsorption
Return of water, small molecules and ions into blood (amino acids, ions, sugar) - most reabsorption
Occurs in renal tubules
Low pressure in capillaries allows for flow of substances from tubules (high to low pressure) to capillaries then into renal vein for circulation
Contains 2 surfaces:
Apical- out of nephron lumen
Basal- into blood
Example of the movement of glucose across the cell membrane
SYMPORT- active movement Na across basal membrane linked to reabsorption of most solutes
Basal membrane = potassium sodium pumps that move Na so it has high conc. in filtrate and now conc. in nephron cell
Na wants to move from high to low, so will move across apical surface
Glucose piggybacks and comes in with Na (symport) and is moving up its conc gradient from low conc. in filtrate to high in nephron cell
Glucose now high conc in cell and wants to move to low conc. so binds to specific carrier molecules so it can cross basal surface via facilitated diffusion into interstitial fluid whereby it is picked up by capillaries to be returned to blood
What is antiport
Example: movement Na with Ca - they move in opposite directions
Na with conc. gradient, Ca against conc. gradient
Where do symport and antiport usually occur
Proximal convoluted tubule
Role of loop of henle in tubular reabsorption
Reabsorption water and some solutes
Reduces filtrate down to 20%
Thickness/thinness and osmotic gradient of tube determines what transport mode
Role of distal convoluted tubule and collecting duct in tubular reabsorption
Little reabsorption as under normal control by anti-diuretic hormone
ADH makes walls more permeable to water so water moves out of filtrate back in to body = small amount of concentrated urine
Reabsorption water via osmosis
Sometimes ion reabsorption via active transport and symport
Coffee and alcohol are diuretics so urine is passed more frequently as less water reabsorbed by kidneys –> too much leads to dehydration as more water lost than what is being taken in
Explain tubular secretion
Movement of non filtered substances, toxin by products of metabolism, drugs or molecules not normally produced by body into nephron for excretion
Occurs mainly in distal convulted tubule
Can be active or passive
Ammonia, penicillin, H, K often secreted
Explain composition of urine
1% filtrate becomes urine , 1-2 L per day
Dilute or concentrated depending on body’s needs (ADH or renin)
95% water, 5% wastes (urea, ammonia, uric acid, H, K, creatinine, bile, drugs, toxins)
Hydrated body = small amount concentrated urine
Very hydrated = produces large amounts of dilute urine
Explain micturition reflex
Bladder capacity is 1L
Elimination of urine
Full bladder activates receptors in smooth muscle which sends message to CNS
Brain voluntarily controls external urinary sphincter
When sphincter relaxes = urination
