Kidney Structure and Function 1 Flashcards
What is the main function of the kidneys
By excretion of water and solutes the kidneys regulate the volume and composition of body fluids within a narrow range
What do the kidneys regulate
- Body fluid osmolality (kg) and volume
- Electrolyte balance
- Acid-Base balance
What hormones do the kidneys produce and secrete
Renin, erythropoietin and calcitriol
Name some end products of metabolism that are excreted by the kidneys
Urea (from AAs)
Uric acids (from nucleic acids)
Creatinine (muscle creatine)
What regulates urination
2 sphincters surrounding the urethra
What % of the CO makes up the renal blood supply
20%
What does the renal vein drain into
The inferior vena cava
What is the outer and inner layer of the kidney called
Outer - Cortex
Inner - Medulla
What is a renal column
Extensions of the renal cortex
What are renal pyramids
The triangular shaped tissue in the medulla formed by the renal columns
What are the papillae
The apical end of each renal pyramid
What is a minor calyx
The tissue that surrounds the papilla
What is the major calyx
The structure formed when you put all the minor calyxes together
What is the renal pelvis
The structure when you put the major calyxes together
What is the hilum
A deep vertical slit on the medial margin of each kidney through which the renal and lymphatic vessels and nerves enter and leave
What are the 2 main types of nephron
Cortical
Juxtamedullary
Where are the cortical and juxtamedullary nephrons found
Cortical = originates in outer two thirds of the cortex Juxtamedullary = originates in inner one third of cortex and have loops of hence that pass deep into the medulla
Name the structures of the nephron in order
Bowmans capsule Proximal Convoluted Tubule Loop of Henle Distal Convoluted Tubules Collecting Ducts
What is the role of the renal corpuscle (glomerulus and bowman capsule)
Formation of ultra filtrate
What is the role of the proximal tubule
Bulk reabsorption of slots and water and secretion of solutes (except potassium)
What is the role of the loop of hence
Establishes medullary osmotic gradient
Reabsorption of water (descending limb) and NaCl (ascending limb)
What is the role of the Distal convoluted tubule
Fine-tuning of the reabsorption /secretion of small quantities of solute
What is the role of the collecting duct
Fine-tuning of water reabsorption
Reabsorption of urea
What is the juxtaglomerular apparatus
A specialised structure where the DCT passes between the afferent and efferent arterioles that supply the glomerulus
What is the macula densa
The short section of the DCT that sense the flow and composition of tubular fluid, it touches the specialised region of the afferent arteriole whose granular cells secrete renin
What does the glomerular filtrate pass through to get into the lumen of the bowman capsule
From the capillary lumen through the fenestrated endothelium, basal lamina of the bowman’s capsule and podocytes
What is the basal lamina of the bowman capsule made up of and how can it act as a filter
Mainly composed of CT, but also contains mesangial cells that are both phagocytic and contractile
Able to actively reduce glomerular filtration by reducing the area available for filtration by contracting
What determines glomerular filtration rate
Net filtration pressure
Why is there an outwards hydrostatic pressure affecting glomerular filtration
Because the afferent blood vessels are wider than the efferent vessels
What factors oppose glomerular filtration
Protein in the blood
Fluid pressure in the bowman’s capsule
Define Glomerular Filtration Rate (GFR)
The volume of fluid filtered from glomeruli into the Bowman’s space per unit time
Despite a low net filtration pressure how does a large volume of filtrate form
As the glomerular capillaries are extremely permeable and have extensive surface area
What regulates GFR
The SNS as it controls the constriction/dilation of the afferent arteries
How does GFR and glomerular capillary pressure change over the systemic arterial pressure range (90-200mmHg)
It doesn’t lol
What is the myogenic response of auto regulation
The myogenic response of the afferent arteriole constricts when systemic arterial pressure rises
this doesn’t affect GFR and works vice versa
What is the tubular glomerular feedback mechanism of auto regulation
Increased flow in the DCT causes cells in the macula densa to release substances to constrict afferent arterioles and dilates efferent arterioles to reduce the glomerular capillary hydrostatic pressure.
How does plasma oncotic pressure affect filtration and what determines it
Plasma oncotic pressure tends to keep fluid in the capillaries and inhibit filtration
Largely determined by plasma proteins
In renal plasma clearance how is quantity excreted per minute calculated
(mg/min)= V (ml/min) x U (mg/ml)
V = rate of urine formation U = inulin conc in urine
In renal plasma clearance how is quantity filtered per minute calculated
(mg/min)= GFR (ml/min) x P (mg/ml)
P = Inulin conc. in plasma
Why is Inulin special in terms fo renal plasma clearance
It is neither secreted nor absorbed and so the amount excreted/min = amount filtered/min
What can the rate of clearance of inulin tell us about the clearance of other substances
Inulin can tell us the GFR and so if the equation for other substances doesn’t equal the GFR then we know it is being reabsorbed
Show how inulin can be used to determine GFR
When inulin is injected into the blood and is filtered by the glomeruli: GFR x P = V x U and so GFR = (V x U)/P Remember : V = rate of urine formation U = Inulin conc in urine P = inulin conc in plasma
