Introduction to the kidney and renal function Flashcards
What are the 2 functions of the urinary system?
- Excretion
The removal of organic waste
products from body fluids
- Elimination
The discharge of waste products
into the environment
List the essential renal functions
What is the consequence of renal dysfunction?
How can renal dysfunction kill you?
Renal function is essential for survival… renal failure, if severe and untreated, leads to death
This failure may be rapid:
acute kidney injury (AKI)
about 10% of renal failure
or it may take many months or, more typically, years to develop:
chronic kidney disease (CKD)
about 90% of renal failure
What is the treatment for renal failure?
Ultimately, renal function must be supplemented artificially, either by dialysis or by a transplanted kidney
Where are the kidneys situated?
Paired organs situated«
on posterior (back) wall of abdomen
behind the peritoneum
on either side of the vertebral column
What are the measurements of a kidney?
Each kidney: 120-170 g (adult human)
Approx: 11 cm long, 6 cm wide, 3 cm thick
What is the renal hilum?
Where each kidney is joined at medial side to renal artery and vein, nerves and ureter
What are the 2 layers of the kidney and what do they contain?
Cortex (outer layer) - composed of ~ 1.25 million nephrons
Medulla (inner layer) - pyramids drain into pelvis which drain into ureters
What is a nephron?
A nephron is the “functional unit” of the kidney responsible for urine formation and composition
Why does GFR decrease with age?
Approximately 1.25 million nephrons per human kidney…
but numbers (and therefore renal function) decline with age
(10,000 nephrons lost per year from about 50 years, GFR 50 % of normal adult rate by age 75)
What are the 5 sections of the nephron?
Glomerulus (Renal corpuscle)
Proximal tubule (PT)
Loop of Henle (LOH)
Distal tubule (DT)
Collecting duct (CD)
Label the types of nephron shown
What are the 2 types of nephron?
CORTICAL NEPHRONS
70-80% of all nephrons in human kidneys
Located in the cortex
Short loop of Henle into medulla
JUXTAMEDULLARY NEPHRONS
20-30% of all nephrons in human kidneys
Situated closer to medulla
Loop of Henle extends deep into renal pyramids
Why do kidneys recieve 20% of cardiac output?
Required for energy-consuming transport processes
Complete the diagram on blood vessels in the nephron
Complete the diagram on blood supply to the nephron
What is the sympathetic nerve supply to the kidneys?
Sympathetic postganglionic fibres from sympathetic chain and fibres from coeliac ganglion
- supplies arteries, afferent and efferent arterioles and granular cells
- reduces blood supply to kidney during stress (fight or flight response)
What is the parasympathetic supply to the kidneys?
Parasympathetic efferent supply from vagus nerve - ganglion in hilum
- may control tone of efferent arterioles
- may modify glomerular filtration rate (GFR) and renal blood flow (RBF)
Which nervous supply to the kidneys may be associated with hypertension?
Sympathetic
What are the 3 major functions of the nephron?
FILTRATION of blood to produce a filtrate
REABSORPTION of water, ions and organic nutrients from filtrate
SECRETION of waste products into tubular fluid
What are the 2 types of transport that happens in the nephron?
Transcellular transport - movement through cells
Paracellular transport - movement between cells
What is glomerular filtration
Filtration occurs at the glomerulus
It is the initial step in urine formation
List the molecules that are filtered and not filtered at the glomerulus
All small molecules are filtered
- Electrolytes
- Amino acids
- Glucose
- Metabolic waste
- Some drugs, metabolites
Cells and large molecules remain in the blood
- Red blood cells
- Lipids
- Proteins
Most drugs, metabolites
More than ____% of filtered water, electrolytes and nutrients are reabsorbed back into the blood…
More than 99% of filtered water, electrolytes and nutrients are reabsorbed back into the blood…
How does tubular reabsorption occur?
Some solutes (e.g. Na+) are reabsorbed down concentration and/or electrochemical gradients
Others molecules can undergo co- transport, (e.g. glucose with Na+)
Water follows passively along the osmotic gradient created by solute (Na+) reuptake via aquaporins
Reabsorption of solutes requires energy in the form of adenosine triphosphate (ATP) which drive Na+ reabsorption via the Na+K+ATPase transporter
How does tubular secretion work?
Some endogenous substances and drugs cannot be filtered at the glomerulus - this may be due to their size or due to their protein binding
Specialised pumps in the PT can transport compounds from the plasma into the nephron for excretion
What are the 2 kinds of pumps involved in tubular secretion?
For organic acids or drugs (e.g. uric acid, diuretics, antibiotics – e.g. penicillin)
For organic bases or drugs (e.g. creatinine, procainamide)
