Kidney structure and function Flashcards
Examples of diseases that are associated with oral health
CVD, RA, respiratory diseases, metabolic diseases (e.g. diabetes), kidney disease
What are the 2 theories that connect oral disease to systemic disease?
- Bacteria from the oral cavity can enter the bloodstream and spread
- Oral inflammation can contribute to systemic inflammation and increase the risk of pathologies at distant sites
What evidence exists to support the theory that oral bacteria can cause systemic problems?
oral bacteria have been isolated in joints of RA patients and in placentas associated with adverse pregnancy outcomes
What is the impact of periodontitis or diabetes on CKD patients?
Having periodontitis / diabetes alongside chronic kidney disease increase mortality risk when compared to patients with only CKD. (association between comorbidities)
What percentage of all global deaths in 2017 were attributed to inflammation-related diseases?
73.4% (diseases that cause damage activate inflammatory pathways leading to chronic inflammation)
Example of an oral disease that can impact survival rates of patients with chronic disease
periodontitis (also is a chronic inflammatory disease)
What does renal physiology literally translate to?
kidney function
What type of organs are kidneys?
excretory organs
Function of kidneys
maintain internal fluid homeostasis by processing blood and removing metabolic waste products via urine
Examples of internal fluids
blood, interstitial fluid, lymph
What must be maintained to ensure internal homeostasis of fluid?
volume and composition must be maintained within homeostatic limits
How can kidneys affect blood pressure?
by regulating fluid volume and electrolyte content of the blood
What are the components of fluids that are regulated by the kidneys?
volume, electrolytes, acid/base (H+/CO3 2-), Ca / vit D metabolism, erythropoietin
How are kidneys involved in vitamin D metabolism?
kidneys convert vit D into an active form that can be utilised by the body
What is the by product of maintaining internal fluid homeostasis?
urine
Describe the gross structure of the urinary system
urine is produced by 2 kidneys, and conveyed by ureters to the bladder where is is stored. The urethra voids urine
What is the medial indentation of the kidneys?
renal hilum
What is the renal hilum?
site where renal artery and nerves enter while ureter and renal vein exit the kidneys.
Location of the kidneys
retroperitoneal - posterior to the peritoneal cavity
What structure protects the kidneys?
renal fat pads (encases kidneys in fatty tissue) (and capsule?)
What are the 3 distinct parts of the kidney?
cortex, medulla, pelvis
What is located in the cortex?
85% of all nephrons
In which part of the kidney is water reabsorbed and urine concentrated?
Medulla
What is the structure of the renal medulla?
composed of medullary pyramids
What are the kidneys encased in?
dense, irregular fibrous capsule and renal fat pads
Function of the renal pelvis
collects and funnels urine into the ureter
Which structures collect urine within the pelvis?
Minor calyces collect urine from the medullary pyramids, and converge to form the major calyces which in turn merge into a central funnel that narrows to form the ureter.
Which artery delivers blood to the kidneys?
renal artery
Which blood vessel does the renal artery originate from?
abdominal aorta
Which blood vessel removes filtered blood from the kidneys?
Renal vein
Where does the renal vein return filtered blood to?
inferior vena cava
Why must the kidney be highly vascular?
Because its function involves filtering blood
What volume of blood is processed by the kidneys per minute?
1.2 L/min (1/5th of cardiac output)
How is the vasculature of the kidney unique to elsewhere in the body?
2 capillary beds - glomerular capillaries and peritubular capillaries (vasa recta)
What is the order of blood vessels in the kidney?
renal artery -> segmental arteries -> lobar arteries -> interlobar arteries -> arcuate arteries -> interlobular arteries -> afferent arteriole -> glomerular capillaries -> efferent arteriole -> peritubular capillaries (vasa recta) -> interlobular veins (and then same as arteries)
Function of glomerular capillaries
site of blood filtration
Function of vasa recta (peritubular capillaries)
supply oxygen and nutrients to the kidney and facilitates water reabsorption
What is the basic functional unit of the kidney?
nephron
What are the 2 types of nephrons?
cortical nephrons and juxtamedullary nephrons
What is the difference between cortical and juxtamedullary nephrons?
Cortical nephrons are located mainly in the cortex and have a short loop of Henle, whereas juxtamedullary nephrons are mainly within the medulla and have a long loop of Henle
Function of juxtamedullary nephrons
conserve water (hence producing very concentrated urine)
Function of the renal corpuscle
filters plasma
Function of the renal tubule
resorption and secretion
Which parts of the nephron makes up the renal corpuscle?
glomerulus and Bowman’s capsule
Which parts of the nephron makes up the renal tubule?
proximal convoluted tubule, loop of Henle, distal convoluted tubule, collecting duct
What is the glomerulus?
A network of fine capillaries that branch from the afferent arteriole and unite to form the efferent arteriole
What is the structure of the glomerular capillaries?
single layer of fenestrated endothelial cells resting on a basement membrane surrounded by pedicels (podocyte processes)
Why is the endothelium of glomerular capillaries fenestrated?
for rapid filtration of blood plasma
What structure surrounds the glomerulus?
Bowman’s capsule
What is the Bowman’s capsule?
a cuplike structure surrounding the glomerulus that collects the filtered fluid in the nephron
Structure of the Bowman’s capsule
Made up of an outer parietal layer and an inner visceral layer with the Bowman’s space in between where the filtrate collects
What is the parietal layer of the Bowman’s capsule made of?
simple squamous epithelium
What is the visceral layer of the Bowman’s capsule made up of?
Podocytes (outer layer of filtration barrier)
What are podocytes?
specialised epithelial cells with long foot-like processes (pedicels) wrapping around capillaries
What is the name of the long branched processes of podocytes that wrap around the glomerular capillaries?
pedicels
What forms the filtration barrier (of glomerular capillaries)?
glomerular endothelium, basement membrane, pedicels
Which structures of the filtration barrier share a basement membrane?
fenestrated endothelium and pedicels
Which structures must a permeable molecule pass through to enter the Bowman’s capsule?
endothelium fenestrations, basement membrane, slits between pedicels
What is the charge of the filtration barrier?
slightly negative charge
What is the effect of the slight negative charge of the filtration barrier?
forms a barrier against large positively charged proteins like albumin which must remain in the blood
What is the filtration barrier referred to as?
true sieve - physically prevents large molecules and cells leaving the blood
How does the filtration barrier determine which molecules are filtered?
depending on the size and charge of filtration slits
What is the first step in blood processing?
glomerular filtration
Via which vessel does unfiltered blood arrive in the glomerulus?
afferent arteriole
Via which vessel does filtered blood exit the glomerulus?
efferent arteriole
What substances are filtered out of the blood at the glomerulus into the Bowman’s space?
water, glucose, amino acids, urea, creatinine, electrolytes (Na+, Cl-, Ca2+, PO43-, K+, HCO3-)
What substances are not filtered?
cells, large proteins, negatively charged proteins (albumin)
Glomerular Filtration Rate (GFR) definition
the rate at which blood is filtered through the glomerulus into the Bowman’s capsule
What primarily drives the GFR?
glomerular hydrostatic pressure (in addition to Bowman’s capsule osmotic pressure)
What generates the high glomerular hydrostatic pressure?
the afferent arteriole has a larger diameter than the efferent arteriole
What counteracts the GFR?
Bowman’s capsule HP (as fluid fills Bowman’s space) and glomerular osmotic pressure (from retained proteins and cells)
Equation to show the effective filtration pressure
(Glomerular HP + capsular OP) - (glomerular OP + capsular HP)
Which factors influence the GFR?
Hydrostatic and osmotic pressure, systemic BP, renin-angiotensin system, disease
What may indicate a compromised filtration barrier?
if proteins / blood cells are present in the urine (dipstick test)
What is a normal healthy GFR?
125ml/min which is 180L/day
How does kidney damage affect GFR?
kidney damage reduces GFR
What is the consequence of a reduced GFR?
there is inefficient blood clearance and waster removal so waste products accumulate in the blood
What substance is measured to estimate the GFR?
serum creatinine (and urea)
Why is serum creatinine used to estimate GFR?
serum creatinine is freely filtered from the blood into the nephron for excretion in urine
What does a high serum creatinine level indicate?
kidney problem as creatinine is accumulating in blood
What does GFR reflect?
kidney function
What percentage of kidney function can be lost before symptoms appear?
50% (stage 3)
Out of the 180L that is filtered by the renal corpuscle per day, what percentage is reabsorbed?
99%
