Anatomy and Physiology Flashcards
What are the organs of the GU system?
- Two Kidneys
- Two ureters
- Bladder
- Urethra
What are the functions of the kidneys?
- Regulate ion levels in the blood
- Regulation of blood volume and pressure
- Regulation of blood pH
- Production of hormones
- Excretion of waste
What ions do the kidneys regulate?
- Sodium
- Potassium
- Calcium
- Chloride
- Phosphate
How do the kidneys regulate blood volume?
Returning water to the blood or eliminating it in urine
How do the kidneys regulate blood pressure?
Secrete enzyme renin which activates renin-angiotensin-aldosterone pathway, adjusting blood flow into/out of the kidney
How do the kidneys regulate pH?
- Regulate concentration of hydrogen ions in the blood
- Conserve blood bicarbonate ions
What are the two hormones produced by the kidneys?
- Calcitriol
- Erythropoietin
What is calcitriol?
- Active form of vitamin D
- Helps regulate calcium homeostasis
What is Erythropoietin?
Stimulates production of red blood cells
What waste products do the kidneys excrete?
- Ammonia and urea
- Bilirubin
- Creatinine
- Uric acid
- Drugs/environmental toxins
General description about the kidneys?
- Pair of reddish organs shaped like kidney beans
- About the size of a bar of soap
- Lie between peritoneum and back wall of the abdominal cavity
- Lies at the 12th thoracic and first three lumbar vertebrae levels
- R kidney lower due to liver
What is the Renal Hilum?
- Near the center of the medial border
- Indentation where ureter leaves
- Indentation where blood and lymph vessels and nerves enter/exit
What is the smooth, transparent renal capsule?
A connective tissue sheath that helps maintain the shape of the kidneys and serves as a barrier against trauma
What surrounds the renal capsule and cushions the kidney?
Adipose tissue
* also anchors the kidney to the posterior abdominal wall
What are the two main, internal regions of the kidneys?
- Renal cortex
- Renal medulla
What is the renal cortex?
Outer light-red region
What is the renal medulla?
Inner, darker red-brown region
What is the further anatomy of the internal regions of the kidneys?
- Cone-shaped renal pyramids are within the renal medulla
- Renal columns, extensions of the renal cortex, fill the spaces between the pyramids
Where does urine formed by the kidneys pass through?
From thousands of papillary ducts within renal pyramids into minor calyces (cuplike structures)
Where does urine go after the minor calyces?
Flows into major calyces —> then into renal pelvis (single large cavity) —> into ureters –> into bladder
How many minor and major calyces does a kidney have?
- Minor: 8-12
- Major: 2-3
What percent of resting cardiac output flows into the kidneys through left/right renal arteries?
- 20-25%
- 1200 ml blood/minute
What is the glomerulus?
Tangled capillary network
What is the pathway of blood through the kidneys?
Renal artery –> smaller vessels –> afferent artiorles –> glomerulus –> efferent artiorles –> peritubular capillaries –>peritubular veins –> smaller veins –> renal vein
What are the small arteries within the kidneys?
- Segmental
- Interlobal
- Arcuate
- Interlobular
What are the smaller veins within the kidneys?
- Interlobal
- Arcuate
- Interlobular
What are the functional units of the kidney?
Nephrons
- Number about a million in each kidney
What are the two parts of a nephron?
- Renal corpuscle
- Renal tubule
What is the renal corpuscle?
Where plasma is filtered
What is the renal tubule?
Where filtered fluid, called glomerular filtrate, passes
What happens to fluid as it moves through the renal tubule?
- Waste and excess substances are added
- Useful materials are returned to the blood
What are the two parts that make up the renal corpuscle?
- Glomerulus
- Glomerular (Bowman’s) capsule
What is the Glomerular (Bowman’s) capsule?
Double-walled cup of epithelial cells that surrounds the glomerular capillaries
What are the three main sections of the renal tubule?
- Proximal convoluted tubule
- Loop of Henle
- Distal convoluted tubule
Where does the renal corpuscle and convoluted tubules lie?
Within the renal cortex
Where does the Loop of Henle extend?
Renal medulla
Where does the proximal convoluted tubule attach?
Glomerular capsule
How is the Loop of Henle situated?
- First part begins in renal cortex
- Extends downward into renal medulla (called descending limb)
- Make hairpin turn and returns to renal cortex (called ascending limb)
Where does distal convoluting tubes empty into?
Common collecting duct
Where does the fluid travel after the common collecting duct?
Several collecting ducts form papillary duct –> minor calyx –> major calyx –> renal pelvis –> ureter
What are the 3 basic functions of a nephron?
- Glomerular filtration
- Tubular reabsorption
- Tubular secretion
What is glomerular filtration?
- Forcing of fluids and dissolved substances through a membrane by pressure
- First step of urine production
- Occurs in glomeruli
What is tubular reabsorption?
- Occurs as filtered fluid flows along renal tubule and collecting ducts
- Returns about 99% of filtered water and useful solutes to blood
How is filtered water and useful solutes returned to blood in tubular reabsorotion?
Peritubular capillaries
What is tubular secretion?
- Occurs as filtered fluid flows along renal tubule and collecting ducts
- Removes substances (waste, drugs, ions) from blood in peritubular capillaries
- Transport substances into fluid in renal tubules
When is filter fluid called urine?
When it has undergone tubular reabsorption and secretion and enters minor and major calyx
What are the two layers of cells that make up the capsule that surrounds the glomerular capillaries?
- Podocytes
- Glomerular endothelium
How does the layering of anatomy in glomerular filtration work?
glomerular capillaries are pushed into glomerular capsule to create the renal corpuscle
What are podocytes?
- Cells that make up the inner wall of the glomerular capsule
- Adhere closely to endothelial cells of glomerulus
What do podocytes and glomerular endothelium form?
Filtration membrane that permits the passage of water and solutes from the blood into capsular space
What forms the outer layer of the glomerular capsule?
Simple squamous epithelium cells
What causes filtration in glomerular capillaries?
Blood pressure
What are the two pressures that oppose glomerular filtration?
- Blood colloid osmotic pressure
- Glomerular capsule pressure
What is the equation of net filtration pressure?
= glomerular capillary blood pressure - (blood colloid osmotic pressure + glomerular capsule pressure)
What is the net filtration pressure?
10 mmHg
What volume of fluid does net filtration pressure force into the capsular space?
- Males: 180 L/day
- Females: 150 L/day
What helps raise blood pressure in glomerular capillaries?
Efferent arteriole because of it has smaller diameter than afferent arteriole
What decreases blood flow into the glomerulas?
Constriction of afferent arterioles
What slows outflow of blood and increases net filtration pressure?
Constriction of efferent arterioles
What is the definition of glomerular filtration rate (GFR)?
Amount of filtrate that forms in both kidneys every minute
What is the number associated with GFR?
- Male: 125 mL/min
- Female: 105 mL/mil
What happens if GFR is too high?
Substances pass through renal tubules too quickly, are not reabsorbed, and pass out of the body as urine
What happens if GFR is too low?
Nearly all filtrate is absorbed and waste products are not adequately excreted
What is Atrial Natriuretic Peptide (ANP)?
Hormone that promotes loss of sodium ions and water in the urine
Where is ANP secreted?
Atrial of the heart
How does ANP work?
Acts on the kidneys to increase loss of sodium ions and water in urine, which reduces blood volume
The blood vessels of the kidneys are impacted by what? What do they cause?
- Sympathetic neurons of the autonomic nervous system
- Cause vasoconstriction
What happens with greater sympathetic stimulation of the arterioles?
Afferent arterioles constrict more than efferent arterioles
What is tubular reabsorption?
Returning most of the filtered water and many filtered solutes to the blood
When does filtered fluid become tubular fluid?
When it enters the proximal convoluted tubule
What carries out tubular reabsorption?
Epithelial cells along renal tubules and collecting tubes
Are solutes actively or passively absorbed?
Both
Which part of the renal tubule adsorbs the most?
Proximal convoluted tubule reabsorbing:
- 65% of filtered water
- 100% of filtered glucose and amino acids
- Large quantities of various ions (Na, K, Cl, HCO3, Ca, Mg)
Which cells maintain homeostasis balances of water and selected ions?
Cells located distal to proximal convoluted tubules
What is tubular secretion?
Transfer of materials from the blood through tubule cells and into tubular fluid
Where does tubular secretion take place and via what process?
- All along renal tubules and collecting ducts
- Passive and active diffusion
What are some substances secreted during tubular secretion?
- Hydrogen ions
- Potassium
- Ammonia (NH3)
- Urea
- Creatinine
What is a poisonous waste product produced when amino groups are removed from amino acids?
Ammonia
Which organ cells convert ammonia to urea?
Liver cells
Where are ammonia and urea filtered and secreted?
- Filtered: glomerulus
- Secreted: Proximal convoluted tubule cells into tubular fluid
How does the body eliminate acids?
Cells of renal tubule secrete H+ into tubular fluid to maintain normal body pH
Why is urine acidic?
Due to H+ secretion
- urine is usually below 7
What are the most important hormonal regulators of ion reabsorption and secretion?
- Angiotensin II
- Aldosterone
Where does Angiotensin II enhance reabsorption of Sodium and chloride?
Proximal convoluted tubules
What does angiotensin II also do?
Stimulates the adrenal cortex to secrete Aldosterone
What does aldosterone do?
Stimulates tubule cells in distal convoluted tubule and throughout collecting ducts to reabsorb more Na+ and Cl- and secrete more K+
When is more water reabsorbed by osmosis?
When more Na+ and Cl- are reabsorbed
What is the major regulator of blood K+?
Aldosterone-stimulated secretion of K+
What plays a minor role in the reabsorption of Na+ and Cl-?
Atrial Natriuretic Peptide
What is the major hormone regulator of water reabsorption and how does it operate?
- Antidiuretic Hormone (ADH)
- Negative feedback system
What stimulate the release of ADH and from where does the release occur?
- Hypothalamus
- Posterior Pituitary
What is a second powerful stimulus for ADH release?
Decrease in blood volume
- from hemorrhaging or severe dehydration
Where does ADH act in the kidneys?
Tubule cells in the last part of the distal convoluted tubules and collecting ducts
What does ADH do?
Increases the water permeability of the tubule cells
What do the kidneys do when ADH levels are low?
Produce a large volume of urine
What stimulates the parathyroid glands to release parathyroid hormone (PTH)?
Lower than normal levels of calcium ions in the blood
What does the parathyroid hormone (PTH) do?
Stimulates cells in early distal convoluted tube to reabsorb more calcium ions into the blood
What is the normal volume of urine eliminated per day in a normal adult and what percentage is water?
- 1-2 L/day
- 95% of total volume is water
