4.Urinary system Flashcards
Function of urinary system
-filter out cellular wastes from blood and excrete urine
-stimulate RBC production
-regulate pH
-produce vitamin D
Structure of ureter
-two tubes from each kidney
-3 layers
Outline 3 layers of ureter
fibrous outer, smooth muscle middle and inner mucous membrane
function of ureter
tubes that transport urine from kidney to bladder via peristalsis
Structure of urinary bladder
-distensible muscular bag
-outer layer of of loose connective tissue, containing blood and lymph vessels
-middle layer of interlacing smooth muscle and elastic tissue called the detrusor muscle, contracts to empty the bladder
-inner mucosa of transitional epithelium which allows the bladder to expand when required
-posterior to pubic symphysis
Function of urinary bladder
to sore of urine before ‘voiding’
Structure of the urethra
-muscular tube/canal that extends from the bladder to the exterior
-surrounded by internal and external urethral sphincter
Compare and contrast female and male urethras
-males are approx. 20 cm long whereas females are 3-4 cm long
-In males it runs with the prostate gland
-in males it conducts both semen and urine compared to only urine in females
Function of the urethra
To transport urine from the bladder to outside of body (excretion)
Structure of the kidneys
Two bean shaped organs, each about the size of a fist
-found posteriorly on abdominal wall, either side of spine, inferior to diaphragm, outside peritoneum, right sits lower
Function of kidney
To remove wastes and extra fluid from the body via urine (regulates blood volume)
-pH regulation
-Electrolyte and fluid balance
-secrete erythropoietin that stimulates RBC production
-Produce renin (regulate BP)
-Metabolise Vitamin D to its active form
Function of cortex (kidney)
protects the inner pars of the kidney
Function of renal pelvis (kidney)
storage of urine before it is transported to urinary bladder
Function of medulla (kidney)
concentrates urine
Function of renal artery and renal vein
Renal artery transports blood from the heart to kidneys for filtration whereas the renal vein transports blood from kidneys to heart
Define nephron
minute or microscopic structural and functional unit of kidney
Structure of Bowmans (Glomerular capsule)
membranous, double walled capsule that surrounds glomerulus
Function of Bowmans (Glomerular capsule)
Receives filtrate of the glomerulus, does not receive blood cells and platelets
Structure of glomerulus
directly encloses the tiny arterial capillary network of the glomerulus
Function of glomerulus
filters the blood plasma, blood cells and platelets
Function of proximal convoluted tubule
reabsorption of ions, glucose, water and amino acids
Function of loop of Henle (medullary loop)
descending = reabsorption of water
ascending = reabsorption of salts
Function of distal convoluted tubule
selective/tubular secretion of ions ( H+ and HCO3-)
Identify steps of urine formation
1.GLOMERULAR FILTRATION
2.TUBULAR RE ABSORPTION
3.TUBULAR SECRETION
Describe glomerular filtration
Occurs in glomerulus
-passive and non selective process driven by pressure
-high pressure in the glomerulus pushes small molecules through the semi permeable capillary walls and walls of the Bowmans capsule into renal tube
-now the filtrate is formed
What molecules pass through capillary walls in glomerular filtration
water, electrolytes, amino acids, glucose and urea
Describe tubular/selective reabsorption
occurs in proximal convoluted tubule
-reabsorption of substances from filtrate into CV system based on needs
-can be down or against concentration gradient (active or passive)
Describe tubular secretion
occurs in distal convoluted tubule
-drugs/meds secreted into tubules,
-ions secrete to regulate pH
-urine formed
-substances not already in filtrate are disposed of
-eliminate unwanted substances by passive means eg urea or uric acid
-remove excess K+
what substances get reabsorbed in tubular reabsorption
water, glucose, amino acids, salts
What are the characteristics of urine
-clear or straw colour due to bile pigments
-pH 4.5 to 8
-96% water, 2% urea, 2% uric acid, creatinine, sodium and potassium, 2% phosphates, chloride, sulphates, and oxalates
Define osmoregulation
process of maintaining a stable water and salt content in the blood
Function of osmoreceptors
specialised receptors in the hypothalamus which detect water levels in the blood
Outline thirst response
insufficient water in body , detected by osmoreceptors of hypothalamus, thirst centre in hypothalamus stimulated, increased thirst, increase water consumption
Outline ADH response (dehydration)
increased ADH secreted by pituitary gland (brain), increased permeability of collecting ducts and distal convoluted tubules, increased reabsorption of water, less in urine (more concentrated urine)
WATER levels are closer to WNL and homeoastsis is maintained
Outline Aldosterone response (dehydration)
Kidneys identify low blood volume, kidneys secrete renin, renin converts angiotensin into angiotensin 2, aldosterone secreted by adrenal gland , acts on distal convoluted tubules, increased reabsorption of sodium ions (water follows) so urine is more concentrated (less H2O)
WATER levels are closer to WNL and homeostasis maintained/Increased blood volume and BP
Outline ANP response (high BP)
-secreted by atria of heart due to increased BP
-acts on ditsal convoluted tubules and collecting ducts
-decreased reabsorption of salts and H2O (less H2O follows)
-more water goes to urine (less concentrated)
-decreases BP closer to WNL
How does body respond to increased BGL
insulin secreting cells of pancreas detect the increased BGL, they release insulin this means that excess glucose is stored as glycogen in liver and muscle cells (most body cells take up glucose), decreasing BGL to WNL
How does the body respond to decreased BGL
glucagon secreting cells of the pancreas detect a decrease in BGL, they release glucagon that converts glycogen stores into glucose in the liver and muscle cells, increasing BGL to WNL
