Renal System Flashcards
Functions
Excretion of waste and toxins
Regulation of blood ionic composition
Maintenance of blood osmolarity
Regulation of blood pH
Regulation of blood pressure
Hormone production
Regulate blood glucose
Kidneys
Either side of the vertebral column
Level T12-L3
Lateral - convex
Medial - concave
Renal cortex and renal medulla
Nephrons
Functional units of the urinary system
Intricate system of tubules surrounded by blood vessels
Millions per kidney
Glomerulus
Compact network of capillaries
Afferent and efferent arterioles
Proximal convoluted tubule (PCT)
In renal cortex
Loop of Henle
Begins in the cortex
Extends into the medulla
Ascending and descending limb
Distal convoluted tubule (DCT)
Links loop of Henle with the collecting duct
In the cortex
Collecting duct (CD)
Function to drain the renal tubules
Glomerulus: Juxtaglomerular appparatus
Differentiated cells that occupy a region of the renal corpuscle
Role in the regulation of blood pressure, volume and osmolarity, secretion of renin
Glomerulus: visceral layer
Fenestrations - small pores, blood plasma can go through
3.4-4.2 nm wide
No big molecules can not enter the filtrate
Glomerulus: filtration membrane
Negative charge molecules can not enter the filtrate
Glomerulus: podocytes
Stellate squamous epithelial cells
Projections that wrap around the capillaries
Filtration
Blood is filtered - water and solutes move out
Glomerular filtrate
Renal corpuscle
Filtrate - glucose, amino acids, wastes, vitamins, electrolytes, nutrients, water.
Glomerular filtrate rate
Rate the kidney/nephron filters the blood
GFR = 125ml/minute
180 tires of filtrate are produced per day
Promotion of filtrate: net filtration pressure
Sum of all forces/pressure
From the glomerular capillaries to the capsular space
Promotion of filtrate: glomerular blood hydrostatic pressure
55mmHg
In glomerular capillaries
Force liquid through the filtration membrane
Promotes filtration
Promotion of filtrate: blood colloid osmotic pressure
30mmHg
Presence of large proteins that cannot pass through the filtration membrane
Opposes filtration
Promotion of filtrate: capsular hydrostatic pressure
15mmHg
Presence of fluid already inside the capsular space and renal tubule
Prevents the passage of liquid through the filtration membrane
Opposes filtration
Auto-regulation
High pressure - afferent arterioles constrict
Low pressure - efferent arterioles constrict, afferent arterioles release renin
Tubular reabsorption
Water and solutes reabsorbed
Proximal convoluted tubule
Sodium is actively reabsorbed
Water, some ions and nutrients by osmosis, diffusion or facilitated diffusion
Tubular reabsorption: transport maximum
Maximum amount of a substance that can be reabsorbed
E.g. glucose exceeds its Tm it is lost in the urine
Tubular reabsorption: aldosterone
Influences reabsorption of water and sodium
In distal convoluted tubule Prevents
Tubular reabsorption: ADH
Affects permeability of the collecting duct to water
Reabsorb more water or increase water loss
Tubular secretion
Substances moved out of blood into the filtrate
Remove particular chemicals
Control ionic composition of the blood
Potassium - proximal and distal convoluted tubule in exchange for sodium
Urine chemical composition
Water
Urea - breakdown of amino acids
Sodium, potassium, phosphate, sulphate
Creatine - metabolism in muscle tissue
Uric acid - metabolism of nuclei acids
Regulation of urine concentration and volume
Body fluid osmotic concentration - 300mOsm
Osmolality - number of solute particles in 1Kg
Osmolarity - number of solute particles in 1L of water
Counter current system
Defending limb - water moves out into capillaries
Ascending limb - impermeable to water, pumps salt out
Anti-diuretic hormone (ADH)
Plasma osmolarity detected by osmoreceptors in hypothalamus, tells posterior pituitary gland to increase or decrease ADH secretion
Affects permeability of collecting duct
Increase of ADH
Collecting duct more permeable to water
More aquaporin channels in membrane
Greater water reabsorption
Less urine
More concentrated
Decrease of ADH
Collecting duct less permeable to water
Less aquaporin channels in membrane
Less water reabsorption
More urine
Less concentrated
Renin-angiotensin-aldosterone mechanism
Renin release from Juxtaglomerular apparatus - low pressure
Converts angiotensinogen (inactive protein) into angiotensin I (inactive) then into angiotensin II by angiotensin converting enzyme (ACE)
Angiotensin II causes
Vasoconstriction of systemic blood vessels
Release aldosterone from adrenal cortex - reabsorption of sodium and water in DCT
Influences ADH release
Acid-bases balance
pH rage of blood - 7.35 - 7.45
More hydrogen ions - lower pH, more acidic
More OH- ions - higher pH, more alkaline
Mechanisms to maintain the acid-base balance
Buffer - soak up excess H+ or OH-
Respiratory system - H+ increase, respiratory rate increase, excess H+ breathed out as CO2
Renal system - low pH, H+ in urine
Production of erythropoietin
By kidneys
Stimulates bone marrow to produce more red blood cells
Hypoxaemia - low levels of oxygen in the blood, stimulates erythropoietin production
Calcium and phosphate regulation
Parathyroid hormone (PTH)
Calcium reabsorbed and phosphate excreted
Low plasma calcium - release PTH, increase calcium reabsorption from kidneys and GIT, release calcium from bones
Needed for - strong bones and teeth, nerve impulse transmission, muscle contraction, blood clotting
Vitamin D metabolism
Obtained from sunlight
Converted in the skin to form modified cholesterol
Kidneys - converts vitamin D into the active form, stimulates absorption of calcium from GIT, maintain calcium levels
