Urinary System Flashcards
Overview of the urinary system
The main components of the urinary system
• 2 kidneys – secret urine
• 2 ureters – transport urine to the bladder
• Urinary bladder – collects and holds urine
• Urethra – transports urine externally
• Adrenal glands – produces hormones The main components of the urinary system
• 2 kidneys – secret urine
• 2 ureters – transport urine to the bladder
• Urinary bladder – collects and holds urine
• Urethra – transports urine externally
• Adrenal glands – produces hormones
Functions of the urinary system and the kidneys
- Bodys main excretory system- for urine.
- Kidneys are the main functional component- specifically the nephrons. Other structures are primarily for transport and storage.
what are the functions of the kidneys?
*excretion
*regulation of blood composition and concentration e.g calcium, potassium.
*regulation of blood volume and interstitial fluid - e.g excrete/ preserve water.
*regulation of bp (production of enzyme renin, increases bp) , and blood pH (acid base balance).
*regulation of calcium homeostasis (hormone calcitriol) , blood glucose (production of glutamine- gluconeogeneiss to produce glucose) .
*red blood cell production
*excretion of metabolic waste products and toxins.
features of the structure of the kidneys
- Paired structures on posterior abdominal wall, lateral to transverse process of spine.
- ovoid in shape- 10-12cm long, 5-7cm wide and 2.5cm thick.
- Retroperitoneal structures- fixed in place.
- anatomical location- T12-L3
- partially protected by the ribs (11th and 12th)
- Level of the kidneys changes with respiration- as you breathe In they move down.
- They lie obliquely with the upper pole being more medial and posterior than the lower pole which is more anterior and lateral.
how do the right and left kidney sit in the body, which one is higher than the other and why?
-Right kidney- situated in the right hypochondrium and right lumbar regions.
-Left kidney- Approx 2.5cm higher than the right kidney- liver pushes the right kidney down. Situated in the left hypochondrium and left lumbar regions.
what is the regional anatomy of the right kidney?
Superior- Right adrenal gland
Anterior- Right lobe of liver, Duodenum, Hepatic flexure
Posterior- Right hemidiaphragm, Posterior abdominal wall
what is the regional anatomy of the left kidney?
Superior- Left adrenal gland
Anterior-Spleen,Stomach,Pancreas, Jejunum, Splenic flexure
Posterior - Left hemidiaphragm, Posterior abdominal wall
why are the supporting tissues of the kidneys important?
Attachment and protection from trauma and infection- acts as a shock absorber.
what are the different supporting tissues around the kidneys?
Outer renal fascia –
- Fibrous connective tissue surrounding kidneys and adrenal glands
- Anterior – Gerota fascia- posterior abdominal wall
- Posterior – Zuckerkandl fascia, fuses with posterior abdominal wall- keeps the kidneys in place.
- Middle Perirenal / perinephric fat- Approximately 2.5cm thick (shock absorber)
Deep peripheral fibrous capsule of kidney
- Smooth transparent membrane; collagen and elastin
- Maintains shape
what is the perirenal space, and what does it contain?
- deep to renal fascia, continues across both sides passes anterior to the spine.
contains both:
- kidneys
- adrenal glands
- renal vessels and hila
- perirenal fat
describe the gross anatomy of the kidney
Bean-shaped, Convex laterally, Concave medially
- 10-12cm long, 5-7cm wide, 3cm thick
- Left normally slightly longer and thinner
- 150 grams
- Hilum medially (small depression on the concave, medial aspect)
- where blood vessels converge, point where everything goes into a structure.
what main components make up the internal structure of the kidneys?
-cortex, medulla, calyces, renal pelvis, renal hilum, renal sinus.
internal structure of kidney- what is the cortex
Reddish-brown granular tissue
* Surrounds and extends into medulla
* Extend internally between pyramids- renal columns
internal structure of kidney- what is the medulla?
Darker in colour
* Contains cone-shaped renal pyramids – approximately 8-18
* Striped appearance – tubules and capillaries
* Central apex – renal papilla
* The tips of the pelvis drain into the minor calyces then the major calyces and then the single renal pelvis to the ureter.
internal structure of kidney- what is the calyces
- Collect urine from papillae
- (8-18) minor to major (2/3) calyces
- Transitional epithelium lined – impermeable
- Smooth muscle walls – peristalsis of urine- collects urine from pyramids. mass transit and movement of urine.
internal structure of kidney- what is the renal pelvis
- Direct continuation from calyces
(similar structure)
- Funnel-shaped
- Continuous with ureter- takes urine out of calyces into there ureter
internal structure of kidney- what is the renal hilum
- Renal artery enters, renal vein exits
- Lymphatic vessels and nerves
- Ureter exits
internal structure of kidney- what is the renal sinus
- Cavity inside medulla
- Contains calyces, renal pelvis, and
blood vessels
what is the microscopic anatomy of the kidneys made up of?
- nephrons
- collecting ducts
collecting ducts are lined with
-principal cells
intercalated cells
what are the nephrons
the functional unit of the kidney; 1-2million per kidney.
Each nephron includes a filter, called the glomerulus, and a tubule.
The nephrons work through a two-step process: the glomerulus filters your blood, and the tubule returns needed substances to your blood and removes wastes.
what are collecting ducts?
- Fewer in number (1000s); drain several nephrons
- Drain urine from nephron through renal pyramids to calyces
- Give striated appearance to pyramids
- Supported by connective tissue and neurovascular structures to supply tissues
- Lined with:
- Principal cells – receptors for antidiuretic and aldosterone hormones; maintain water and Na+
- Intercalated cells – role in homeostasis of blood pH. Microvilli on surface.
what are there functions of the nephron, and what 3 processes does it consist of?
- Homeostasis of blood composition
- Urine production
- Three processes:
1.Glomerular filtration (takes it all out to a separate vessel)
2.Tubular reabsorption (takes what it needs back; most of it)
3.Tubular secretion (gets rid of what’s left
what are the 2 types of nephrons? why do we get 2 different types?
Two types of nephrons dependent on location and minor differences in structure and blood supply:
Cortical 85%
* Located in renal cortex except small part extending into medulla
* Surrounded by peritubular capillaries
Juxtamedullary
* Located closer to cortex/medulla junction
* Loop extends deep into medulla
* Role in producing concentrated urine
* Surrounded by Vasa recta capillary network
what is the renal corpuscule- golmerulus
- Literally means ball of wool
- Very convoluted bunch of tiny arterial capillaries
- From afferent arteriole, leaves via efferent arteriole
- Fenestrated – lots of pores to allow free passage of fluid and solutes
- High pressure throughout- helps filtration process.
what is the golmerulaer (Bowmans) capsule and what 2 layers does it consist of?
- Cup which surrounds most of the glomerulus; ‘catches the filtrate’
Two epithelial layers:
* External parietal layer – simple squamous epithelium
* Inner visceral layer – highly modified cells called podocytes
* octopus-like ‘foot cells’
* cling to glomerulus
* Filtration slits between ‘foot cells’
- Capsular space between layers drains into proximal convoluted tubule
- One associated with each nephron within ascending limb of nephron loop, close to afferent arteriole
what does the Bowmans capsule help regulate?
Helps regulate:
* Rate of formation of Rltrate
* Systemic blood pressure
what 3 types of cells is the woman’s capsule made from?
- Macula densa: chemoreceptors to monitor NaCl levels entering the DCL
- Granular (or JG) cells
-smooth muscle – mechanoreceptors to sense blood pressure
-Secrete renin hormone
- Extraglomerular mesangial cells – pass signals between other cells
renal tubules- what are the 3 different parts of it
- About 3cm long, divided into 3 parts:
- Proximal convoluted tubule
- large mitochondria within epithelial cells
- covered in microvilli to increase surface area to allow increased capacity
- Nephron loop (loop of Henle)
- Descending and ascending limbs
- Different types of epithelial cells result in thin and thick segments
- Distal convoluted tubule
- Similar to PCT
- Fewer microvilli
what are the ureters and their function?
- Carry urine from kidneys to urinary bladder, Continuous with renal pelvis
- 25-30cm long, 3mm in diameter
- Retroperitoneal, anterior to Psoas muscles, over brim of pelvis
- Passes obliquely into posterior aspect of bladder – vesico-ureteric junction (VUJ)
- Pressure in bladder compresses distal ureter to prevent reflux
- Peristalsis to help gravity propel urine – 1-5waves per minute
what 3 layers are the ureters comprised of?
- Peripheral protective fibrous tissue (adventitia), continuous
with renal capsule
- Middle muscular layer to propel urine:
-Internal longitudinal
-External circular
-External longitudinal (distal 1/3 only)
- Inner protective mucosa
-Transitional epithelium
-Protects from urine
what is the urinary bladder, where does it lie?
- Temporary storage/reservoir for urine
- Smooth muscular sac, collapsed when empty
- Retroperitoneal on pelvic floor, posterior to symphysis pubis
- Relational anatomy dependent on sex
- Lies in pelvic cavity but changes position and size when distended,
moves into abdominal cavity
what are the 3 layers of the urinary bladder?
- External fibrous tissue (peritoneum superiorly)
- Middle thick smooth muscular layer; detrusor
- Internal mucosal layer
what are some features of the urinary bladder?
- Three orifices on base for bilateral ureters and urethra
- Smooth triangular region on base called trigone; sensitive
- Allows micturition to be infrequent and controlled
- Pyramidal shape when empty
- Walls fold into rugae (like stomach)
- As fills, walls thins and rugae lost
- Allows distension without increase in pressure
- Normally holds 300-500mls, Can hold up to 800mls
what is the urethra and some of its features?
Tube extending from neck of bladder to external urethral orifice
* Approximately 4cm in females
* Approximately 20cm in males (prostatic, membranous, spongy sections)
* Differences in structure due to different roles
* Thickening of detrusor muscle at junction; internal urethral sphincter
* Involuntary – autonomic nervous system
* External urethral sphincter – skeletal muscle as passes urogenital diaphragm
* Voluntary, assisted by levator ani muscle
summarise the blood supply to the kidneys and urinary system
- Quarter of entire blood volume passes through kidneys every minute – approx. 1.2 litres per minute
- Each supplied by own renal artery
- Branch of abdominal aorta, inferior to superior mesenteric artery
- Left about L1
- Right about L2, longer, passes posterior to IVC
- Divide before hilum into anterior/posterior branches to parenchyma
- Additional accessory arteries common
- Considered vulnerable as no effective anastomoses
what are the different branches and arteries of the urinary system blood supply.
- Branches of renal arteries into several segmental arteries
- Divide into interlobular arteries towards renal columns
- Arch along border of renal pyramids and cortex as arcuate arteries
- Numerous branches radiate towards periphery of cortex; cortical radiate arteries
- Numerous afferent arterioles, one per nephron…..
- Multiple small renal veins drain into single left and right renal
veins - Anterior to renal arteries
- Left longer and passes anterior to abdominal aorta
- Drain into inferior vena cava at similar level
- Lymphatic drainage into lumbar lymph
what is micturition?
- emptying of the urinary bladder, ‘voiding’.
- to allow this, three processes occur:
-contraction of the detrusor muscle (smooth, involuntary).
-Opening of the internal urethral sphincter (smooth, involuntary).
-Opening of the external urethral sphincter (skeletal, voluntary).
- only final stage is voluntary, but needs to be trained,
what is the process of micturition, 9 steps.
- urine leaves bladder by micturition reflex
- detrusor muscle contracts forcing urine out of the urinary bladder , the external urethral sphincter relaxes.
- Stretching of the urinary bladder triggers micturition reflex centre in the sacral portion of the spinal cord.
- 4, parasympathetic impulses cause the detrusor muscle to contract in waves, urge to urinate is sensed,
- voluntary contraction of the external urethral sphincter and inhibition of the micturition reflex from the brainstem and cerebral cortex precent urination.
- during urination, the external urethral sphincter is relaxed, and impulses from the pons and the hypothalamus facilitate the micturition reflex.
- when the detrusor muscle contractions become strong enough, the internal urethral sphincter relaxes and forced open,
- the external urethral sphincter composed of skeletal muscle is under conscious control, this opens, and urine is expelled.
- bladder can hold up to 600ml of urine but urge to urinate begins at 150ml.
what are the adrenal glands and their function ?
- Part of endocrine, not urinary system
- Paired glands on superficial aspect of kidneys, within renal fascia and fat
Produce hormones for stress response (and electrolyte balance) – directed by hypothalamus
Pyramid-shaped, 4cm long, 3cm thick
what is the hormone and blood supply to and from the adrenal glands?
- Arterial supply from branches from renal arteries and abdominal aorta
- Venous drainage by suprarenal veins; left into left renal vein, right into IVC
what are the 2 different structures of the adrenal glands?
-adrenal cortex- essential for life
-adrenal medulla.
what is the adrenal cortex?
- Bulk of gland, external to medulla
- Produce over two dozen steroid hormones - corticosteroids
what 3 layers make up the adrenal cortex?
Zona glomerulosa:
* Mineralocorticosteroids (including aldosterone)
* Balance of minerals and water in blood (particularly Na+ and K+)
Zona fasciculata:
* Glucocorticoids (e.g. cortisol)
* Body metabolism
Zona reticularis:
* Gonadocorticoids
* Androgens, sex hormones (converted to testosterone/oestrogen)
what is the adrenal medulla and its functions
- Knot of nervous tissue
- Part of sympathetic nervous system
- Cells produce ‘fight-or-flight’ hormones catecholamines
- epinephrine
- norepinephrine
- Short acting effects:
- Increase heart rate and blood pressure
- Divert blood to essential organs by dilating their arteries and constricting less important ones (e.g. skin)
- Increase metabolic rate
- Dilate pupils
what 3 processes are involved in urine formation?
- golemerular filtration
- tubular reabsorption
- tubular secretion
what is golumerular filtration (urine formation)
Glomerular filtration:
- Blood pressure in the glomerular capillaries forces fluid and small molecules out of the blood. Filtration is non-selective; based on size of molecules, those small enough to fit through the filtration membrane are removed
urine formation- what is tubular reabsorption?
Tubular reabsorption:
- cells in the renal tubules contain transport proteins that return water and some filtered molecules back into the blood in the peritubular capillaries
urine formation- what is tubular secretion?
certain tubule cells transport additional solutes from the blood into the filtrate which may have not been filtered by the filtration membrane
what is urea and uric acid? are they more likely to be reabsorbed of excreted in urine?
- Urea is a by product of amino acid metabolism; uric acid is a by product of nucleic acid metabolism.
- urea is passively reabsorbed by diffusion but about 20% of urea is excreted in the urine
- Most uric acid is reabsorbed by active transport and a small amount is secreted into the renal tubule.
composition of urine
- 95% water
- usually contains metabolic waste products: urea, uric acid and creatine,
- likely to contain trace amounts of amino acids and varying amounts of electrolytes.
- urine volume: 0.6 - 2.5L/day ; 50-6- mL of urine output/ hour is normal.
- volume varies with fluid intake and environmental factors
- <30ml/hour can indicate a problem.
normal variants likely to be seen in urinary system x rays,
- Renal agenesis
- ectopic kidney
- horseshoe kidney
- duplex kidney
- duplex ureters
