Phase 1 - Week 10 (Kidneys, Prostatic Hyperplasia, Screening Programmes) Flashcards
Describe the location of the kidneys
- Posterior abdominal walls
- Level T12-L3
- Right slightly lower than left (due to right lobe of liver)
- Held to posterior abdominal wall, behind parietal peritoneum (retroperitoneal)
- Partially protected by lower ribs
List the layers of the external anatomy of the kidneys
From inside to outside:
- Renal capsule
- Adipose tissue
- Renal fascia
Renal capsule
Thin, fibrous sac, dense irregular connective tissue. Adheres closely to kidney. Maintains shape and protects from trauma and infection.
Adipose capsule of kidneys
Layer of fat - surrounds renal capsule. Protects and supports the kidney.
Renal fascia
Layer of tissue, passes in front of and behind both kidneys to anchor them to the peritoneum and posterior abdominal wall. Dense, irregular connective tissue, attaches to renal capsule by strings of fibres. Provides anchorage of kidneys to surrounding tissues.
List the sections of the internal anatomy of the kidneys
From outside to inside:
- Renal cortex
- Renal columns
- Renal medulla
Renal cortex
Dark outer 1cm of kidney, contains arcuate + interlobar arteries + veins + cortical nephrons (except parts of loop of Henle + collecting ducts - in medulla). Where ultrafiltration takes place.
Renal columns
Extensions of cortex - project in between the pyramids of the medulla - anchor the cortex.
Renal medulla
Inner section of kidney, contains renal pyramids. Appears striated - contains tubular systems of the juxtamedullary nephrons, parts of loop of Henle + collecting ducts of cortical nephrons
Describe the route which urine takes after production
- Renal pyramids
- Renal papilla
- Minor calyces
- Major calyces
- Renal pelvis
- Ureters
Renal pyramids
- Contain tubules of juxtamedullary nephrons, parts of loop of Henle + collecting ducts of cortical nephrons
- Cone-shaped
- Terminate medially, protrude into minor calyces
- Appear striated - bundles of nephron loops and collecting ducts and associated capillaries
Renal papilla
- Tips of pyramids, protrude into minor calyces
- Where all urine from collecting ducts drains into minor calyces
Minor calyces
- Cup-like projections
- Surround the papilla of each pyramid in renal medulla
- Several converge to from a minor calyx
- Collect and convey urine produced by kidneys to major calyces
Major calyces
- 2/3 per kidney
- Formed by fusion of minor calyces
- Unite to form renal pelvis
- Collect urine from minor calyces, drain it to renal pelvis then into ureter
Renal pelvis
- Single, funnel-shaped structure
- Located centrally at hilum of kidney
- Forms from union of major calyces
- Drains urine out of kidney to ureter
Describe the passage of blood through the kidneys
- Renal artery
- Segmental artery
- Interlobar artery
- Arcuate arteries
- Interlobar arteries
- Capillary network
- Interlobar vein
- Arcuate vein
- Renal vein
Renal arteries
- Pass laterally from abdominal aorta to hilum of kidney
- Branch into segmental arteries
Segmental arteries
- Branch from renal artery
- Split into interlobar arteries
- No venous equivalent
Interlobar arteries
- Branch from segmental arteries
- Pass through renal column
Arcuate arteries
Leave interlobar arteries at right angles, branch over outer surface of pyramids, forming arterial anastomosis.
Interlobular arteries
- Also called cortical radiate arteries
- Branch from arcuate arteries
- Supply cortex
Capillary network of the kidneys
- Interlobular arteries enter renal cortex - divide into branches called afferent arterioles
- Each nephron receives one arteriole - divides to plexus of capillaries around nephron
- Network of vessels is highly specialised - location of filtration of blood flowing through kidney
- Capillaries leave nephron as efferent arteriole - carry blood out of glomerulus
- Efferent arterioles divide into peritubular capillaries - eventually reunite to from interlobular veins
Interlobular veins
- Also called cortical radiate veins
- Drain cortex into arcuate veins
Arcuate veins
- Travel along outer surface of pyramid
- Travel down renal columns as interlobular veins - forming a venous anastomosis
Renal vein
- Formed by union of the arcuate veins at the hilum of the kidney
- Passes medially to drain into inferior vena cava
Describe the innervation of the kidneys
- Origins at renal ganglion
- Travel along renal arteries - inter-renal plexus
- Renal nerves regulate volume of blood through kindeys by affecting vasoconstriction/vasodilation of the aterioles
- Part of the autonomic nervous system
List the functions of the kidneys/urinary system
- Excretion of waste/toxins - products of metabolism
- Regulation of blood ionic composition
- Maintenance of blood osmolarity
- Regulation of BP
- Hormone production
- Regulation of blood glucose
List the waste products excreted in urine
Products of metabolism - mostly urea from breakdown of amino acids, also bilirubin, ammonia and uric acid
Which ionic components of blood are regulated by the kidneys?
Sodium ions, potassium ions, chloride ions, phosphate ions
What is the normal osmolarity of blood?
300 mOsm/L
How do the kidneys contribute to the regulation of blood pressure?
Through secretion and activity of renin - renin production increases BP
List the hormones secreted by the kidneys
- Renin - BP
- Erythropoietin - RBC production
- Calcitriol - active Vit. D, absorption of calcium and phosphorus
How do the kidneys contribute to the regulation of blood glucose?
Decrease in blood glucose, kidneys metabolise glutamine to glucose via gluconeogenesis - blood glucose increases
Nephrons
Functional units of urinary system
List the types of nephrons
- Cortical
2. Juxtamedullary
Cortical nephrons
Short loops of Henle, barely penetrate the renal medulla
Juxtamedullary nephrons
Within the cortex, long loops of Henle - penetrate deep into the medulla
Renal corpuscle
- Compact network of capillaries - glomerulus, surrounded by glomerular capsule (Bowman’s capsule)
- Surface between glomerulus and capsule is highly specialised to facilitate filtration of blood to produce the glomerular filtrate - enters renal tubules for further processing before it becomes urine
Describe the structure of the Bowman’s capsule
2 layers
1. Visceral layer
2. Parietal layer
+ basal lamina
Describe the structure of the visceral layer of the Bowman’s capsule
- Podocytes - highly specialised stellate squamous epithelial cells
- Surround glomerular capillaries
- Have thousands of finger-like projections (processes) - wrap around capillaries of the glomerulus
- Processes branch into secondary + tertiary processes which give rise to fine terminal processes known as pedials
Describe the structure of the parietal layer of the Bowman’s capsule
Capsular epithelium - sheet of simple squamous epithelial cells
Describe the basal lamina of the Bowman’s capsule
- Thick layer of ECM - hidden by overlying epithelial cells of capsular epithelium
- Forms part of basement membrane - epithelial cells anchored
List the parts of the renal tubules
- Proximal convoluted tubule
- Thick descending loop of Henle
- Thin descending loop of Henle
- Thin ascending loop of Henle
- Thick ascending loop of Henle
- Distal convoluted tubule
Proximal convoluted tubule
- Located entirely in renal cortex
- Directly connected to glomerular capsule
- Twisted structure
- Function = large proportion of solute and water reabsorption
- Cell type = simple cuboidal or low columnar epithelial cells - well-developed brush border (border of microvilli) increase surface area for tubular reabsorption
Thick descending loop of Henle
- Extends from renal cortex -> renal medulla as a continuation of the PCT
- Function = water reabsorption, some solute reabsorption
- Cell type = simple cuboidal or low columnar epithelial cells with brush border of microvilli, increased surface area for tubular reabsorption
Thin descending loop of Henle
- Extends deep into renal medulla
- Function = active + passive reabsorption of sodium ions and water
- Cell type = simple squamous epithelial cells, short sparse microvilli
Thin ascending loop of Henle
- Connected to the descending limb, begins in medulla, runs parallel to descending limb
- Function = passive ion reabsorption, impermeable to water
- Cell type = simple squamous epithelial cells - short sparse microvilli
Thick ascending loop of Henle
- Enters renal cortex, joins early distal convoluted tubule
- Function = impermeable to water, sodium, potassium and chloride ions reabsorbed
- Cell type = simple cuboidal + low columnar epithelial cells
Distal convoluted tubule
- In renal cortex
- Two parts - early and late
- Early = reabsorption of water, sodium, chloride and calcium ions
- Simple cuboidal epithelial cells
- Late = reabsorption of sodium, bicarbonate, urea and facultative reabsorption of water. Secretion of potassium + hydrogen ions
- Simple cuboidal or low columnar epithelial cells, principle cells and intercalated cells
Collecting ducts
- Nephrons drain into a single collecting duct, which then drains into a papillary duct in the renal pyramid
- Function = reabsorption of sodium ions, bicarbonate, urea and water. Secretion of potassium + hydrogen
- Cell type = simple cuboidal or low columnar epithelial cells, intercalated cells - abundant mitochondria + longer villi
Describe the function of the glomerulus and Bowman’s capsule
- Ultrafiltration - water, ions, glucose, amino acids out
- Filtration between podocytes
Describe the function of the proximal convoluted tubule
- Active reabsorption
- Glucose, amino acids, sodium + potassium ions
- Co-transporters, aqueous channels, membrane pumps
- Substantial water reabsorption
Describe the function of the loop of Henle
- Active pumping of solute out of ascending, diffuses into descending
- Recycling of solute
- Develops high osmotic pressure at tip of loop
Describe the function of the distal convoluted tubule
- Similar function to PCT
- ‘Fine tune’ sodium and potassium ion exchange
Describe the function of the collecting ducts
- Concentration of urine
- Ducts pass close to loop - high osmotic pressure
- If CD is permeable to water, it is drawn out of the duct by osmotic pressure to concentrate filtrate
- Duct permeability set by ADH
- When ADG present AQP2 inserted into collecting duct membrane to allow water movement
Describe how the kidneys control blood osmolarity when there is decreased water intake
- Decreased water intake
- Increased production of ADH by hypothalamus
- Increased number of AQP2 recruited by membrane of collecting ducts
- More water reabsorbed
- Decreased urine water concentration
Describe how the kidneys control blood osmolarity when there is increased water intake
- Increased water intake
- Decreased production of ADH by hypothalamus
- Decreased number of AQP2 recruited by membrane of collecting ducts
- Less water reabsorbed
- Increased urine water concentration
Explain how the kidneys regulate blood pressure
Low blood pressure = low rate of filtration of blood in the kidneys (hypofiltration)
This stimulates the kidneys to secrete Renin
Renin triggers the conversion of angiotensin to angiotensin I, which is then converted to angiotensin II by angiotension converting enzyme (ACE).
Angiotensin II regulates renal blood flow and glomerular filtration rate, causing an increase in blood pressure - via sympathetic nerves.
Describe control of salt balance by the kidneys
Aldosterone production increases when electrolyte concentration fall (secreted by glomerulosa cells of the adrenal cortex). Aldosterone increases reabsorption of ions from the loop of Henle, DCT and duct cells. Also increases potassium secretion. When electrolyte reabsorption increases, water reabsorption increases.
Describe the structure/location of the prostate
- Underneath the bladder
- Surrounds the beginning of the urethra
- Posterior surface can be easily palpated through anterior wall of the rectum
- Composed of tubolalveolar glands supported by stromal connective tissue containing thick sheets of smooth muscle
- Secretory epithelium = psuedostratified, tall columnar cells + basal cells supported by a fibroelastic stroma
Describe the function of the prostate
- Produces thin, milky prostatic fluid:
1. Aids sperm motility
2. Aids viability of sperm
3. Protects sperm against acidic vaginal secretions
Benign prostatic hyperplasia
- Common in elderly males - half of all 60 year olds, nearly all males >85 y/o
- Prostate made of glandular + fibromuscular tissue, beneath urinary bladder. Part of urethra runs through middle of prostate
- Prostate proliferates due to high levels of testosterone
- Enlargement causes compression of glands around prostate - e.g. urethra
List the symptoms of benign prostatic hyperplasia
Mostly due to effects of prostate compressing urethra:
- Increased urination at night - nocturia
- Poor urine flow
- Difficulty starting urination (hesitancy)
- Dribbling at end of urination
- Incontinence
- Recurrent UTIs
- Enlarged prostate gland on rectal exam
Describe the diagnosis of benign prostatic hyperplasia
- Confirmed by ultrasound, guided biopsy of prostate
- Blood levels of PSA - usually slightly raised
- Signs of infection in urine
- Investigation of urine flow
Describe the aims treatment of benign prostatic hyperplasia
To reduce size of prostate, improve urinary flow and reduce symptoms
Describe the treatment of mild benign prostatic hyperplasia
Advice on fluid intake, bladder training
Describe the treatment of moderate benign prostatic hyperplasia
Adrenergic blockers - improve urine flow
Describe the treatment of severe benign prostatic hyperplasia
Surgical intervention - - Transurethral resection of prostate - insertion of probe into urethra, remove parts of prostate causing obstruction
- Complete surgical removal of prostate (prostatectomy)
Define a screening programme
Examination of a group of usually asymptomatic people to detect those with a high probability of having a given disease, typically by means of an inexpensive diagnostic test
List the criteria for a screening program
- Condition is important problem for individual/community
- Accepted treatment
- Facilities for diagnosis + treatment available
- Recognisable latent/early symptomatic stage
- Suitable test/examination
- Test acceptable to population
- Development of disease understood
- Agreed policy on who is treated as a patient
- Economically viable - cost of test balanced with overall medical care cost
- Case finding = continuing process
- Quality assurance - minimise risk
- Informed choice, confidentiality, respect for autonomy
- Promote equity + access for all
- Benefits outweigh harm
What process helps the flow of urine in the ureters?
Peristalsis
What is the:
a) Minimum
b) Maximum
urine production rate?
a) 1ml/min
b) 20ml/min
How does the bladder detect the volume of urine?
Stretch receptors in the bladder wall signal volume
Describe the structure of the male bladder
- Bladder wall = smooth muscle (detrussor), allows large volume changes
- Activity of detrussor affected by reflexes - passive stretch of the wall triggers contractions
- Contraction of detrussor produces additional force/pressure
- Several sites of pressure measurement
- Bladder fills when sphincter pressures > vesicle pressure
- Bladder empties when vesicle pressures > sphincter or urethral pressures
List the phases of bladder filling and emptying
- Storage phase
2. Voiding phase
Describe the bladder’s storage phase
- Early filling phase, low pressure in bladder, bladder wall and sphincter relaxed
- No flow in urethra - urethral pressure > bladder pressure
- Sensations develop, sphincter contracts to maintain continence
Describe the bladder’s voiding phase
- ‘Urge’ then ‘voluntary voiding’
- Bladder contracts, urethra and sphincter relaxes. Flow in urethra - bladder pressure > urethral pressure
- Voluntary stop flow then a second voiding phase
Describe the innervation of the bladder and sphincter
Sympathetic - L1, L2 (bladder wall and internal sphincter)
Parasympathetic - S2 (bladder wall)
Somatic - S2, S3 and S4 (sensory and motor to external sphincter)
List the sensations which accompany filling of the bladder
- Sense of filling
- Fullness
- Desire
- Discomfort
- Pain
Give examples of screening programmes
- Cervical screening
- Breast screening
- Bowel screening
Who is eligible for cervical screening?
- Age 25-49 every 3 years
- Age 50-64 every 5 years
Who is eligible for breast screening?
- Age 50-70 every 3 years
Who is eligible for bowel screening?
- Age 50-74 every 2 years
Drug receptor
A macromolecular component of a cell with which a drug interacts to produce a response, usually a protein
List the types of drug receptors
- Enzyme linked (multiple actions)
- Ion channel linked (fast)
- G protein linked (amplifier)
- Nuclear (gene) linked (long lasting)
Agonist
Drug which stimulates the action of its receptors. Drug that interact with and activate receptors - possess both affinity and efficacy.
Antagonist
Drug which inhibits the action of its receptor. Interact with the receptor but do not change the receptors - have affinity but no efficacy.
Affinity of a drug
Measure of propensity of a drug to bind receptor - the attractiveness of drug and receptor
Efficacy (or Intrinsic Activity) or a drug
Ability of a bound drug to change the receptor in a way that produces an effect
Potency of a drug
Relative position of the dose-effect curve along the dose axis. Has little clinical significance - low potency is only a problem is the dose is s large that it is awkward to administer.
Describe the two types of agonists
- Full - agonist with maximal efficacy
2. Partial - agonist with less than maximal efficacy
List the types of antagonists
- Competitive
2. Non-competitive
Competitive antagonist
- Competes with agonist for receptors
- Surmountable with increase agonist concentration
- Reduces the apparent affinity of the agonist
Non-competitive antagonist
- Drug binds to receptor and stays bound
- Irreversible - does not let go of receptor
- As more receptors are bound the agonist drug becomes incapable of eliciting a maximal effect
Median effective dose 50
The dose at which 50% of the population of sample manifests a given effect
Median toxic dose 50
Dose at which 50% of the population manifests a given toxic effect
Median toxic dose 50
Dose which kills 50% percent of the subjects
Therapeutic index
TD50 or LD50 / ED50
The higher the TI, the better the drug. Drugs acting on the same receptor or enzyme system often have the same TI
