Urinary (Basics) Flashcards
What is the main function of the renal cortex?
Filtration (to form urine)
What is the main function of the medulla?
Collection & excretion of urine
What happens in the renal papilla?
Medullary pyramids empty urine into major/minor calyces
Where are the glomeruli located in the kidney?
Cortex
what % of cardiac output may pass through the kidneys at any one time?
25%
Where is the capillary network found in the glomerulus?
Between TWO arterioles
What is the functional unit of the kidney?
The nephron
What are the 3 main section of the renal tubule?
PCT
Loop of Henle
DCT
What is the glomerulus?
Afferent arteriole divisions forming a capillary network at the Bowmans Capsule
Which type of nephron are present in dogs and cats? Clinical significance?
Juxtamedullary ONLY - urine very concentrated
Where do JM nephrons recieve their blood supply from?
Vasa Recta - runs parallel to LoH
What are the3 major functions of the kidney?
Regulates fluid/electrolyte balance
Extretes waste
Produces hormones
Which two hormones are produced in the kidney?
EPO
Renin
Describe how the peritubular capillaries promote reabsorption.
High oncotic pressure
What does the renal corpuscle consist of?
Bowmans Capsule
Glomerulus
What are the 3 major functions of the nephron?
Glomerular Filtration
Tubular reabsorption
Tubular secretion
What is the GFR?
Amount of filtrate formed in all renal corpuscles of both kidneys in each minute.
What is the aim of tubular reabsorption?
Returning important substances to the body FROM the filtrate
What is the aim of tubular secretion?
Movement of waste from body TO the filtrate
Where does filtration take place?
Glomerulus (Renal corpuscle)
Where does bulk, unregulated reabsorption take place?
PCT
Where does secretion take place?
PCT
How much filtrate doe shte kidney produce per day?
60x plasma volume
Which process in the nephron is indiscriminate?
Filtration
Which process in the nephron is extensive and selective?
Tubular reabsorption
Where does fluid filtered from the glomerulus enter?
Bowmans space (lumen of urinary tract)
Why is it important to maintain glomerular capillary BP?
GFR is directly related to CBP
what cannot be filtered at the glomerulus?
Proteins
What are the 3 factors affecting GFR?
capillary HSP
capillary flow rate
capillary SA
Desrcibe the link between vasoconstriction and GFR.
Vasoconstriction decreases GFR.
Vasodilation increases GFR
Which cells detect increases in GFR and where are they?
Macula Densa Cells
In JM apparatus.
AUTOREGULATE
A massive increase in sympathetic tone has what effect on GFR?
Vasoconstriction
Dec renal blood flow
Dec GFR
What effect does sympahtetic drive have on blood volume and how?
Conserves fluid via dec GFR and stimulation of renin
What effect does Ang II have on GFR?
Decreases
What effect does ANP have on GFR?
increases it
Why is ANP released?
stretching of atria
Where is angiotensinogen made?
Liver
Where is aldosterone secreted from?
Adrenal Cortex
Where is ADH secreted from?
Hypothalamus to Posterior Pituitary and blood
What are the two routes of tubular reabsorption?
PAracellular (passive)
Transcellular (active)
The asymmetrical distribution of which ion pump is key to tubular reabsorption?
Na/K
In which direction does Na move in reabsorption and how?
Active transport of Na OUT of tubular cells towards capillaries
How does Na reabsorption drive reapsorption of H20?
Anions follow electrochemical gradient made by Na+ active transport.
Water moves via osmosis following solute.
How is glucose reabsorbed?
secondary active transport - facilitated via Na symport.
How do other Cations become reabsorbed?
Follow water down diffusion gradient (passive)
What is transamination?
conversion of amino acid to glutamate
What is deamination?
conversion of glutamate to urea
How is urea transported?
Passively
How does the body get rid of urea?
continuous high GFR required to prevent high blood concentration
What are the 3 key principles of secretion in the PCT?
Always active
Non-selective
Substances must be ionised
What substances are secreted in the PCT?
Hormones
Drugs
Environmental Pollutants
How does the PCT affect acid-base balance?
Secretes H+
Reabsorbs HCO3
What is the key membrane transporter in the LoH?
Ka+-K+2Cl- symporter
What is the descending loop of henle permeable to?
water
What is the descending loop of henle NOT permeable to?
Na
What is the ascending loop of henle permeable to?
Na/K/Cl (active)
What is the ascending loop of henle NOT permeable to?
water
Was is the osmolarity of the water leaving the LoH?
Hyposmotic
How does ADH cause water retention in the kidney?
Insert aquaporins onto apical memberane to promote absorption
What 2 things cause ADH release?
Hypovolaemia
Hyperosmolarity