Week 11 Flashcards
First part of the glomerulus
There is an arterial inflow of o2 and arterial outflow of o2, created high pressure environment
What is special about the glomerulus
It is very porous - allows small molecules and fluid out of the blood
It is surrounded by cells called podocytes - allows further filtration
Role of podocytes
Podocytes further filters and allows fluid passing into Bowman’s space
What does/dosent get filtered
Small molecules such as na+, glucose and amino acids get filtered
Large molecules such as red blood cells dosent get filtered
What surrounds the glomerulus
The bowmans capsule
What happens at the proximal convoluted tubule
The start of the reabsorption via the cells lining the PCT
Happens via active transport (use of ATP)
Fluid moves from PCT to..
What happens here
The Loop of henle
Crosses border of cortex and the medulla
Medulla is hypertonic (high electrolyte conc)
Descending loop of henle - reabsorption of h20 - filtrate is losing water so becoming more hypertonic
Acsending loop - reabsorption by body of na+, cl-, k+
Functions of the kidneys
Regulation of water, inorganic ion balance, and acid-base balance
Removal of metabolic waste products from the blood and their exertion in the urine
Gluconeogenesis
Production of hormones/enzymes
-EPO
-Renin
What happens after the loop of henle
Fluid moves to the distilled convoluted tubule
Filtrate is becoming more concentrated
Then it comes to the collecting duct - last stage where body can reabsorb anything it needs
Anti-diuretic hormones acting
Nephrons
Nephrons are the structural and functional units of the kidney. Each kidney has over 1 milllion of these units
Each nephron consists of a renal corpuscle, which contains the glomerulus and a renal tubule
The tubule forms a cup shape around the glomerulus called the glomerular capsule (bowman’s capsule)
Glomerular filtration (GFR)
The GFR is the amount of blood filtered by the glomeruli each minute
Factors influencing GFR:
Capilliary permeability
Surface area (size of capillary bed)
Hydrostatic pressure that drives fluid out of the capillaries
Osmotic forces within the capillaries, which oppose the exit of fluid
Renal clearence (RC)
The amount of substance filtered per minute, divide by its plasma concentration
RC = (U*V) / P
U = conc of the substance in the urine
V = flow rate of urine formation
P = concentration of substance in the plasma
Water and lean body weight
Water makes up 60% of our lean body weight
2/3 of our total body water is located within our cells - intracellular fluid
The remaining 1/3 is outside the cells - extracellular fluid
Sodium reabsorption
It is an active process occuring in all tubular segments except the descending limb of the loop of henle and the medullary collecting duct
Water reabsorption
This is by diffusion (i.e. osmosis)
Key points of sodium reabsorption
Active transport out of cells into interstitial fluid
Transport achieved by Na+/K+ -ATPase pump
Keeps intracellular conc of Na+ low to allow downhill movement of Na+ from lumen
Aquaporins
Water channels that are activated that move towards the cell walls to help transport water out of the tubules and back into the body.
They increase water reabsorption
Anti-diuretic hormone (ADH)
What does it initiate
ADH (aka vasopressin) initiates a cascade of events within the collecting duct cells that leads to an increased number of AQP2 channels in luminal membrane. This allows increased passive diffusion of water into the cell
ADH
It increases the insertion of aquaporins into the membrane of the collecting duct cells, meaning water can flow out of the collecting duct and be reabsorbed by the body
Stimulates through osmoreceptors and baroreceptors
3 factors that deterine the rate of sodium reabsorption
1 - aldosterone
2 - atrial natriuretic peptide (ANP)
3 - local effect of the blood pressure on the tubules
Diuretics
Substances that promote the loss of Na+ and H20.
Alcohol acts like a diuretic by inhibiting the release of vasopressin from the pituitary gland
Basic Renal Process for Sodium and Water
The body gains H2O via ingestion and metabolism, it loses H2Ovia
urine, the gastrointestinal tract, and evaporation from the skin and
respiratory tract.
The body gains Na+ and Cl− by ingestion and loses them via the skin (in
sweat), the gastrointestinal tract, and urine
The renal system is the major homeostatic control point for controlling
H2Oand Na+
Renal Na+ reabsorption
Baroreceptor regulation of blood pressure simultaneously regulates total-body Na+
Aldosterone controls tubular Na+ reabsorption The renin–angiotensin system is one of the two major controllers of aldosterone secretion
ANP also controls Na+ reabsorption
Renal H2O reabsorption
Baroreceptor regulation of blood pressure simultaneously regulatesH2Oexcretion
Main controller of water reabsorption is ADH
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