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The Urinary system and renal function - Coggle Diagram
The Urinary system and renal function
Items normally found in urine:
Water, ions including NA+, K+ and CA2+. Nitrogenous waste: creatine, urea, uric acid. Hormones: sex hormones. Dead cells: Epithelial cells. Crystals: Calcium citrate.
Movement of urine:
3 ways urine moves from the kidney to the bladder: 1. peristaltic contractions. 2.Hydrostatic pressure. 3. Gravity. Urinary back flow from bladder up to the ureters is prevented by - pressure exerted on the uterers as the bladder fills up. One way valve between the utterers and the bladder.
Systems in the body which effect urine production:
CARDIAC- Blood flow and blood pressure ENDOCRINE - hormone release for high and low blood volume. NERVOUS - Sympathetic nervous sytem response.
Kidneys produce 3 hormones:
Erythropoeitin (EPO)
- inportant role in the production of red blood cells. Released in response to hypoxaemia. Stimulates red bone marrow to produce red blood cells.
Calcitriol
- Active form of vit D. Helps promote absorption of calcium in foods. Helps regulate bone formation.
Renin
- RELEASED FROM CELLS IN AFFERENT ARTERIOLES WHEN BLOOD PRESSURE DROPS. ACTIVATES THE RENIN-ANGIOTENSIN-ALDOSTERONE SYSTEM (RAAS). CASCADE THAT ACTIVATES OTHER HORMONES TO CONSERVE WATER AND INCREASE BLOOD PRESSURE IN RESPONSE TO LOW BLOOD PRESSURE.
Glomerular Filtration Rate;
“The amount of filtrate formed by both kidneys per minute.” Good indicator of kidney efficiency. Normal range between 105- 125mls/min. eGFR is calculated by estimating creatinine clearance
THE KIDNEY MAINTAINS HOMEOSTASIS BY:
Regulating blood electrolytes by secreting excessive ions into the urine. Regulating blood pH by excreting/conserving H+ or bicarbonate ions. Regulating blood volume by conserving or eliminating water. Maintaining blood osmolarity by secreting excessive Na+ into the urine. Excreting waste products: ammonia, urea, creatinine. Producing hormones: EPO, calcitriol, and produces the enzyme renin which leads to the production of angiotensin & aldosterone. Regulating blood glucose.
Kidney:
Each kidney has 2 distinct regions: The cortex - outer component of kidney.
The cortex
- outer component of kidney. Renal columns contain blood vessels and fibrous tissue to anchor the cortex.
The medulla
- inner component of kidney. Contains renal pyramids. These contain microscopic collecting tubes and blood capillaries.
NB
, the renal pelvis is the funnel shaped area connecting to the urerter.
The hilum is the entrance for the:
Renal Artery. Renal Vein. Ureters. Nerves. Lymphatics
RENAL BLOOD SUPPLY:
Blood supply: Oxygenated blood enters each kidney via a renal artery. The renal arteries are large branches of the abdominal aorta. Deoxygenated blood exits each kidney via a renal vein. Renal blood flow is approx - 1200mls/minute.
Nephrons:
More than a million microscopic functional units make up the bulk of each kidney - these are called nephrons. Nephrons have 2 main regions: the renal corpuscle and the renal tubule. Fluid is filtered out of the blood to form filtrate. Much of this Is returned to the blood, and the remainder leaves the connecting duct as urine.
The renal corpuscle:
The renal corpuscle consists of two parts: the glomerulus - a mass of capillaries. The glomerular (Bowmans) capsule. The glomerulus is fed by the afferent arteriole and drains (exits) into the efferent arteriole. The afferent arteriole is bigger than the efferent.
BLOOD FLOW THROUGH THE NEPHRON:
RENAL ARTERY
->
AFFERENT ARTERIOLES
->
GLOMERULUS
->
EFFERENT ARTERIOLES
->
PERITUBULAR CAPILLARIES
->
RENAL VEINS
The number of nephrons:
Constant from birth. Not replaced if injured. Kidney dysfunction often not apprarent until <25% of normal function. Removal of one kidney causes enlargement of the other, in order to maintain renal function.
Formation of urine:
1.
Glomerular filtration - Water and small dissolved solutes move from the glomerulus into the glomerular capsule.
2.
Tubular reabsorption - Water and important substances are returned from the filtrate in the tubule back into the blood.
3.
Tubular secretion - The transfer of unwanted substances from the blood into the urine (or removal of H+ from the blood). Urine composition reflects the exchange of substances between the nephron and the blood in renal capillaries.
GLOMERULAR FILTRATION:
Water & solutes move from the blood into the glomerular capsule. Glomerular filtrate travels into the renal tables. Blood cells, plasma proteins & platelets are too large to filter into the glomerular capsule, so remain in the blood. Effective glomelar capsule, so remain in the blood. Effective glomerular filtration requires a constant blood pressure to force the fluids and solutes across the membranes into the glomerular capsule.
Waste products: These include; creatinine
- a waste product of muscle metabolism. Excreted via glomerular filtration (not reabsorbed or secreted in tubules) Urea - limited reasbsorption in from the convoluted tubule. Some electrolytes - NA+, k+. A reduction in GFR = rise in creatinine levels in blood.
TUBULAR REABSORPTION:
TUBULAR REABSORPTION IS THE PROCESS OF RETURNING IMPORTANT SUBSTANCES FROM THE FILTRATE BACK INTO THE BLOOD
How tubular reabsorption occurs:
Passive transport
- Proximal convoluted tubule is 'leaky' and allows substances (e.g NA+) to pass through into the capillaries. Water follows by osmosis. The proximal convoluted tubule has the greatest level of reabsorption.
Active transport
- Sodium and potassium pumps.
Assessing renal function:
Rate of filtration through GFR. Eltrolites including potassium, high levels show kidney is failing to excrete it. Waste products if there is lots of waste means kidney isn't doing a good job of getting rid of waste products. Example urea rises as renal function declines. And creatine
Ways renal system contributes to balance of homeostasis of the cardiovascular system:
Kidneys filter the blood and dispose of nitrogenous wastes, maintain fluid, electrolyte, and acid base balance in the blood. Kidneys control blood volume and blood pressure by regulation of Na+ and water balance. Kidneys produce erythropoietin which stimulates the production of red blood cells. Kidneys produce renin which initiates the RAAS pathway when blood pressure is lowered.
HORMONAL CONTROL in kidneys:
Kidneys produce 3 hormones - Erythropoeitin (EPO), Calcitriol and Renin (next slide).
ERYTHROPOIETIN
- helps produce white blood cells, realised in response to hypoxaemia, stimulates red bone marrow to produce red blood cells.
CALCITRIOL -
form of vitamin D, helps with calcium absorption.
RENIN -
related from cells in afferent arterioles when blood pressure drops.
TWO hormones respond to DECREASED blood volume and result in less urine production to increase blood volume and BP:
ALDOSTERONE AND ALDOSTERONE.