Anatomy and Pattern recognition of the urinary system Flashcards
vocab
Nephro – pertaining to the kidney – e.g. nephron – functional unit of the kidney
Renal - kidney eg renal artery
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 urinary system is closely linked with the genitals – the genitourinary system
• Urology is the study of the male / female urinary and male reproductive systems
functions of US
It is the body’s main excretory system
The kidneys are the main functional component
– specifically the nephrons
Other structures are primarily for transport and
storage
Functions of the kidneys include
• Homeostasis of water and electrolytes
• Excretion of metabolic waste, chemicals and drugs
• Hormone and enzyme production
• Production, storage and excretion of urine
Kidneys filter approximately 200litres of fluid
from blood per day
Most water and solutes returns to blood
Excesses, toxins and waste is removed in the urine
Functions of the kidneys – detailed
Excretion – fluid and waste are passed through the urinary system and pass out of the body
Regulation of blood composition and concentration (osmolarity), electrolytes/ions
• Regulate the concentration of major ions such as calcium, potassium, calcium, vitamin D etc.
Regulation of blood volume and interstitial fluid
• Excrete/preserve water
• Regulation of red blood cell synthesis – secretion of erythropoietin
Regulation of blood pressure
• Regulation of blood volume
• Production of enzyme renin, with the effect of
increasing blood pressure (renin-angiotensin pathway)
Regulation of blood pH
• Acid-base balance; H+ and HCO3- ions
Regulation of calcium homeostasis
• Release of hormone calcitriol – activated form
of Vitamin D
Red blood cell production
• Release of hormone erythropoietin – stimulates production of red blood cells
Regulation of blood glucose
• Production of glutamine – gluconeogenesis to
produce glucose
Excretion of metabolic waste products and toxins
• Urine
• e.g ammonia, urea, bilirubin, creatinine, uric
acid, drugs
the kidneys structure
The are paired structures on the posterior abdominal wall, lateral to the transverse process of the spine
Anatomical location – T12-L3
They are partially protected by the ribs (11 and 12th ribs)
The level of the kidney changes with respiration
right kidney
Situated in the right hypochondrium and right lumbar regions
left kidney
Approximately 2.5cm higher than the right kidney
• Situated in the left hypochondrium and left lumbar regions
regional anatomy right kidney
Right kidney
Superior
• Right adrenal gland
Anterior
• Right lobe of liver
• Duodenum
• Hepatic flexure
Posterior
• Right hemidiaphragm
• Posterior abdominal wall
regional anatomy left kidney
Left kidney
Superior
• Left adrenal gland
Anterior
• Spleen
• Stomach
• Pancreas
• Jejunum
• Splenic flexure
Posterior
• Left hemidiaphragm
• Posterior abdominal wall
The kidneys – supporting tissues
Attachment and protection from trauma and
infection
Outer renal fascia –
• Fibrous connective tissue surrounding kidneys and
adrenal glands
• Anterior – Gerota fascia
• Posterior – Zuckerkandl fascia, fuses with posterior
abdominal wall
Middle Perirenal / perinephric fat
• Approximately 2.5cm thick
Deep peripheral fibrous capsule of kidney
• Smooth transparent membrane; collagen and elastin
• Maintains shape
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
Nephrons – key facts
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
Fluid taken out of blood at first stage is known as filtrate
Urine only at the end of the three processes
the nephron
Ensure homeostasis of blood and urine production
Three main processes:
• Filtration of blood
• Return necessary substances to blood
• Remove unwanted substances from body
Surrounded by capillary networks to reabsorb most of fluid and solutes
Renal corpuscle - glomerulus
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
Glomerular (Bowman’s) capsule
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
Capsular space between layers drains into proximal convoluted tubule
Renal tubules
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
The nephron two types
• Two types dependent on location and minor differences in structure and blood supply
- cortical
- juxtamedullary
Glomerular (Bowman’s) capsule regulation
One associated with each nephron within ascending limb of nephron loop, close to afferent arteriole
Helps regulate:
• Rate of formation of filtrate
• Systemic blood pressure
Blood supply
- 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
anastamoses
how blood flows
- 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
how blood is supplied
• 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 nodes near renal artery origin
Ureters
- Carry urine from kidneys to urinary bladder
- • Comprised of 3 layers:
• Peripheral protective fibrous tissue (adventitia), continuous with renal capsule - Middle muscular layer to propel urine
- Inner protective mucosa
Urine formation
Involves three processes
• 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
• 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
• Tubular secretion:
- certain tubule cells transport additional solutes from the blood into the filtrate which may have not been filtered by the filtration membrane
Urea and uric acid excretion
. 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
Micturition three processes
• Contraction of the detrusor muscle (smooth, involuntary)
• Opening of the internal urethral sphincter (smooth, involuntary)
• Opening of the external urethral sphincter (skeletal, voluntary)
Micturition
1 urine leaves bladder by the micturition reflex
2 detrusor muscle.contracts which forces urine out the urinary bladder and allows the external urethral sphincter to relax
3 stretching or the urinary bladder triggers the micturition reflex centre in the sacral portion of the spinal cord
4 parasympthetic impuses cause detrusor muscle to contract in waves and urge to urinate is sensed
5 voluntarybcontraction of external urethral sphincter and inhibition of the micturition reflex prevents urination
6 during urination external urethral sphincter is relaxed
7 when detrusor muscle contractions become strong enough internal urethral sphincter relaxes and is forced open
8 external uretral sphincter composed of skeletal muscle is under concious control this opens and urine is released
9 bladder can hold upto 600ml of urine but urge to urinate begins at 150ml
The adrenal glands
• Produce hormones for stress response (and electrolyte balance)
• Two parts with different structure and functions (effectively separate glands):
• Adrenal cortex – essential for life
• Adrenal medulla
Adrenal cortex
• Bulk of gland, external to medulla
• Produce over two dozen steroid hormones - corticosteroids
adrenal medulla
• Knot of nervous tissue
• Part of sympathetic nervous system
• Cells produce ‘fight-or-flight’ hormones
• 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
