10 The Urinary System Flashcards
What are the structures of the urinary system?
- kidneys (2)
- ureters (2)
- the bladder
- urethra
What are the functions of the urinary system?
- regulation of the volume and composition of body fluids
- regulation of electrolyte/ion balance
- regulation of acid-base (pH) balance
- hormone production and secretion
- waste exretion
- regulation of blood glucose levels
The maintenance of normal body fluid levels is important for:
- maintaining normal cell volume
- normal function of the cardiovascular system
The urinary system maintains normal body fluid levels by:
- regulating the excretion of water and NaCl
- enzyme secretion (renin) which results in water retention
The kidneys regulate pH balance by exreting ___ ___ and reabsorbing ___
hydrogen ions (H+); bicarbonate
What hormones do the kidneys produce and what do they do?
- erythropoietin (EPO) stimulates red blood cell production
- calcitriol – the active form of vitD
- renin – an enzyme that activates the renin-angiotensin-aldosterone system (helps in the regulation of blood pressure and Na+ and K+ balance)
Urine contains:
- ammonia and urea (waste products from protein metabolism)
- bilirubin (waste product from the breakdown of hemoglobin)
- uric acid (waste product from the breakdown of nucleic acids)
- creatinine (waste product from skeletal muscle)
- medications, toxins
With hypoglycemia, the kidneys can produce and release ___ into the blood stream
glucose
Where are the kidneys located?
- retroperitoneal
- located between T12 and L3, partially protected by ribs 11 and 12
What are the superficial and deep portions of the kidneys called?
- renal cortex: superficial layer
- renal medulla: inner portion
What’s the name of the functional unit of the kidney and what are its parts?
- nephron
- 3 parts
- proximal convoluted tubule (PCT)
- loop of Henle (nephron loop)
- distal convoluted tubule (DCT)
Where does blood enter the kidneys?
blood enters the kidney (renal artery) and branches into smaller and smaller vessels
What’s the glomerulus and what happens there?
- glomerulus: a tangled ball-like network of capillaries (pl. glomeruli)
- at the level of teh glomerulus, water and solutes in blood plasma are filtered through the capillary walls, into the glomerular (Bowman’s) capswule space and into the renal tubule
- the fluid that enters the capsular space is called the glomerular filtrate
- blood flows out of the glomerulus into teh efferent arteriole
- the efferent arteriole leads to another capillary network – the peritubular capillaries
- the peritubular capillaries merge to ultimately form the renal vein which leaves the kidney
What happens as filtered fluid moves along the renal tubule and collecting duct?
- most of the water and useful solutes are reabsorbed and returned to the blood in the peritubular capillaries
- wastes are drawn from the peritubular capillaries and are secreted into the fluid for removal from the body
- urine: fluid produced by the kidneys that contains wastes and excess materials
What’s Glomerular Filtration Rate (GFR)?
- the amount of filtrate formed per minute
- GFR is an indicator of kidney function
- GFR is fairly constant under normal conditions
What are the ways the body regulates Glomerular Filtration Rate (GFR)?
- in general, the body will regulate GFR by:
- adjusting blood flow into and out of the glomerulus
- altering the capillary surface area available for filtration
- specifically, there are 3 ways the body controls GFR:
- renal auto-regulation
- neural regulation
- hormonal regulation
When the body regulates GFR, how does Renal Auto-Regulation work?
- myogenic mechanism
- an increase in BP increases renal blood flow which increases GFR
- it also stretches the walls of the afferent arterioles
- this stretching triggers the contraction of smooth muscle in the walls of the afferent arterioles
- vasoconstriction reduces blood flow and reduces GFR to previous level
- the opposite happens with a decrease in BP
- tubuloglomerular feedback
- an increase in BP increases renal blood flow which increases GFR
- this also increasees the NA+, Cl-, and water in tubular fluid
- the increased NA+, Cl-, and water in tubular fluid triggers vasoconstriction of the afferent arteriole
- vasoconstriction reduces blood flow and decreases GFR to the previous level
- the opposite happens with a decrease in BP
When the body regulates GFR, how does Neural Regulation work?
- kidney BVs get SyNS innervation (no PaNS)
- SyNS activation causes vasoconstriction (both afferent and efferent)
- with increasing SyNS activation, vasocontriction of the afferent arteriole is greater which decreases GFR
- this reduces GFR and helps redirect blood flow to other tissues
When the body regulates GFR, how does Hormonal Regulation work?
- angiotensin II
- strong vasoconstrictor (both afferent and efferent)
- reduces GFR
- atrial natriuretic peptide (ANP)
- released by the heart in response to atrial stretching (i.e. increased blood volume)
- increases GFR
The following 5 hormones affect the re-absorption and secretion of water and ions by the renal tubules. How do they each work?
- angiotensin II
- aldosterone
- ANP
- ADH
- PTH
- the renin-angiotensinaldosterone system
- decreased BP –> kidneys secrete renin (an enzyme)
- renin converts angiotensinogen (made by the liver) into angiotensin I
- angiotensin I is converted to angiotensin II at the lungs by angiotensin-converting enzyme (ACE)
- angiotensin II
- decreases GFR (afferent arteriole vasoconstriction)
- increases re-absorption of Na+ and Cl- ions and water stimulates the release of aldosterone
- aldosterone: increases re-absorption of Na+, Cl-, and water
- ANP (atrial natriuretic peptide): increases exretion of sodium and water
- ADH (antidiuretic hormone): increases water reabsorption
- PTH (parathyroid hormone): increases re-absorption of calcium
What are ureters and how do they work?
- collecting ducts (which receive urine from several nephrons), collect and form larger and larger pathways to the level of the ureter (1 from each kidney)
- peristaltic contractions in teh ureter move urine to the bladder
Describe the bladder and its location.
a hollow muscular organ that sits posterior to the pubic symphysis, anterior to the rectum, and in females sits inferior to the uterus
What are urethra and urethral sphincters and how do they work?
- internal urethral sphincter: controls the flow of urine from the bladder into the urethra
- urethra: the tube from the floor of the bladder to the exterior
- external urethral sphincter: part of the pelvic flood mm., controls the flow of urine out of the urethra
What’s the Micturition Reflex and how does it work?
- micturition/urination/voiding/elimination: the discharge of urine
- pressure within the bladder stimulates stretch receptors which initiate a reflex via the PaNS – the bladder contracts, the internal sphincter relaxes
- the external sphincter also relaxes
- bladder filling gives a sensation of fullness before the micturition reflex occurs
- after early childhood, we have conscious control
What are some causes of urinary incontinence?
- increased abdominal pressure (stress incontinence)
- nerve damage
- aging
- disease/injury
- some medications
- smoking
What are some things that happen with the urinary system with (advanced) aging?
- kidneys decrease in size
- renal blood flow and GFR decrease
- glomeruli become less (or non-) functional
- kidney diseases become more common
What’s gynecology?
a specialized branch of medicine concerned with the diagnosis and treatment of diseases of the female reproductive system
What’s urology?
male and female urinary systems and male reproductive system
What is/are gamete?
germ cells (sperm in males, egg in females) that combine to form the offspring
What’s an embryo?
the devoloping organism from fertilization to the end of 8 weeks
What’s a fetus?
the developing organism (in utero) from 9 weeks to birth
