Date post: | 27-Mar-2015 |
Category: |
Documents |
Upload: | logan-sharp |
View: | 219 times |
Download: | 2 times |
Urinary System
Four major structures Kidneys Ureters Urinary bladder Urethra
Kidneys Organ that produces urine Performs other functions Contains nephrons
microscopic structure that produces urine
Left kidney lies in the upper ABD behind the spleen
Right kidney lies behind the liver Located at what we call the flank area Hilum
Where the renal artery, nerves, lymphatic vessels, and ureter pass into the kidney
Nephrons In a young adult there are aprox. One million We loose 10% per decade after age 40
CortexThe outer tissue region of the kidney MedullaThe inner tissue region of the kidney PyramidsMedulla is divided into fan-shaped regions PapillaWhere the pyramids terminateCasts into the renal pelvis a hollow space
The spaces of the pelvis come together at the derivation of the ureter
Urine forms in the cortex and medulla and leaves the kidney through the renal pelvis and the ureter
Nephron Functional unit of the kidney Forms urine Consists of a tubule Each tubule is divided into parts of a different
structure and capillaries which form a complex net of vessels that covers the surface of the tubule
Glomerulus
Capillaries that filter blood into a nephron Bowman’s capsule First part of the nephron tubule that is a cup-
shaped, hollow structure
Water and chemical substances enter the tubule through the bowman’s capsule and after passing through the successive parts of the tubule proximal tubule
descending loop of henley
ascending loop of henley
distal tubule
Urine drips in the collecting duct before entering the renal pelvis and ureter
Nephron Physiology
Major functions of the kidneys
forming urine
eliminating urine
Entails Maintaining blood volume with proper balance
of water,electrolytes and pH Retaining glucose while excreting waste such
as urea
Controlling arterial blood pressure
relies both on urine formation and another mechanism that does not involve formation of urine
Kidney cells regulate erythrocyte development ; does not involve urine formation
First step in urine formationfiltration of blood
Blood flows through the capillaries of the glomerulus and water and numerous chemical materials are filtered out into the Bowman’s Capsule
Blood cells and plasma proteins are not filtered as they are too large to pass through into the capsule
Filtrate
Fluid after the filtration process Blood is filtered at a rate of 180L/day Thus urea and drug metabolites can be filtered
so quickly that they don’t accumulate in the blood
The process of reabsorption and secretion maintain homeostatis of the body
Reabsorption and Secretion Intracellular transport
simple diffusion
facilitated diffusion
active transport
Simple diffusion Molecules small enough to permiate the cell
membrane randomly move in and out of the cell
Requires no energy Higher [ ] to lower [ ] equalizes both sides
Osmosis
the movement of water to equalize [ ] on both sides of the membrane
Osmolarity
When particles are dissolved in water they move so that the [ ] is equal on both sides
Facilitated diffusionA molecule-specif “helper” or carrier acts as a
tunnel and speeds the molecule along and through the membrane
i.e.GlucoseWhen insulin binds to a glucose-specific carrier,
it can pass 10x quicker than without insulin
Active transport {“uphill”} Net movement of lower to higher [ ]. Requires E Essential for homeostasis by handling
electrolytes and glucose as well as other substances
Water and Electrolytes
Electrolytes
Na+
K+
H+
Cl-
The handling of water and electrolytes is the footing for control of blood volume and electrolyte balance
Maintaining blood volume Na+ is the main cation in extracellular fluid
whereas K+ is the main cation in intracellular fluid
Appropriate retention of Na+ along with osmotic retention of water
Electrolyte and pH balance Retention of K+ and Cl-
So. . . . . . . .
Filtrate formed in the Bowman’s capsule enters the proximal tubule.
65% of Na+ and Cl- is reabsorbed as well as osmotic reabsorption
At the same time H+ is secreted which through a process determines the pH of venous blood leaving the kidneys as well as the excreted urine
20% of water in the filtrate is reabsorbed
Diuresis
Formation and passage of a dilute urine, decreasing blood volume
Handling of Glucose Freely filtered into the Bowman’s capsule Reabsorbed before filtrate enters the proximal tubule Retained to a certain level then glucose is lost in
urine When there is so much glucose in the filtrate
reabsorption becomes insufficient so not only is glucose lost in but large amounts of water as well
Control of arterial blood pressure The balance of water and electrolytes thus
maintaining blood volume Juxtaglomerular cells respond to low blood
pressure by releasing the enzyme renin Renin then produces the hormone angiotensin
I Angiotensin I flows through the lungs and by
process produces Angiotensin II
Angiotensin II acts on both kidney tubular cells and on adrenal cells
Adrenal cells produce aldosterone
So how do these all come into play. . . .?
Aldosterone
Target tissue; distal tubule
collecting duct
Effects increases reabsorption of Na+, Cl- and water
Angiotensis II
Target Tissue; Proximal tube
Effects: increases reabsorption of Na+, Cl- and water
increases secretion of H+