Urinary Flashcards
Two fluid compartments in humans
- Inside the cells (Intracellular; ICF)
- Outside the cells (Extracellular; ECF)
- Interstitial Fluid
- Plasma
- Other (Lymph, CSF, Mucus)
How do we obtain water?
- Ingested in solids and liquids
- Metabolically derived
- Thirst influences intake of water
How do we lose water?
- Excretion in urine
- Excess water and excess or harmful solutes removed
- Evaporation from the lungs and skin
- Sweating
- In feces
Kidney functions
- Remove metabolic wastes from the blood
- Adjust fluid balance in the body
- Water-Salt balance
- Acid-Base balance - Horomone secretion
- Produce erythropoietin
- Produce renin
- Converts vitamin D to a form that facilitates calcium absorption and blood calcium levels (Calcitriol)
How do the kidneys remove metabolic wastes
- CO2: major metabolic waste; exhaled in respiratory system
- Breakdown of protein produces wastes including:
- Ammonia (toxic) converted to urea (in Liver); half is reabsorbed in the kidney
- Creatinine made by muscle cells from the breakdown of creatine phosphate - Breakdown of nucleic acid produces uric acid
- Kidneys maintain the electrolytic balance of ions
Maintenance of water-salt and acid-base balance
- Both are homeostatic mechanisms
- Water-salt balance helps to maintain blood pressure
- Excretes hydrogen ions and reabsorbing bicarbonate ions this maintains acid-base balance (blood pH ~7.4)
Kidneys (filtration)
- Pair of bean-shaped organs
- Outer cortex
- Inner medulla
- Outer covering: renal capsule
- Central cavity: renal pelvis
Urine storage and excretion
- Pair of ureters
- Urinary bladder
- Urethra
Renal Capsule
Tough outer covering of the kidneys
Hilus
A large renal artery enters and similarly large renal vein exits the kidney at the hilus and the kidney’s nerves and lymphatic vessels and ureters pass through here too.
renal pyramids
cone-shaped structures formed from an accumulation of collecting ducts filled with urine
renal pelvis
adjacent to the hilus, is where the formed urine is collected and passed to the ureters
nephron
responsible for filtering a portion of the blood that passes through the kidney
glomerulus
- is a knotted vessel at the beginning of each nephron
- It is formed from an incoming arteriole
- glomerular capsule (also called Bowman’s capsule) surrounds the glomerulus
peritubular capillaries
- The blood vessel leaving each nephron then breaks into peritubular capillaries
- Wind around the entire nephron before collecting into venules and eventually the renal vein
- This capillary bed surrounds the nephron
- It is here that the urinary and cardiovascular systems are linked
The nephron’s tubule has three sections
- The proximal convoluted tubule (PCT)
- A loop of Henle (also called the loop of nephron)
- A distal convoluted tubule (DCT) connected to a collecting duct
- The tubule that extends from the glomerular capsule is the proximal convoluted tubule
collecting duct
- gathers newly formed urine from a series of nephrons and drains it to the renal pelvis
Steps to Urine Formation and locations
- Filtration - occurs at the glomerular capsule
- Reabsorption - occurs all along the tubular part
- Secretion - occurs at the distal tubule
Th three criteria that must be met for Glomerular filtration to occur.
- the first step in urine formation
- Three criteria must be met in order to filter blood plasma through the glomerulus
- Blood pressure must be high enough to force plasma out of the glomerular vessel walls
- The fluid already in the glomerulus must have a low enough pressure to allow more fluid to be forced into the nephron tubules
- The osmotic pressure of blood in the peritubular capillaries must be high enough to draw water back into the capillaries from the nephron tubule
- (If these conditions are not met, the nephron cannot filter the blood, and the urinary system will fail)
Glomerular Filtration
- Glomerular blood pressure is higher than systolic blood pressure
- This is caused by the kinking and twisting of the glomerular vessels
- The incoming afferent arterioles have a larger diameter than the outgoing efferent arterioles
- This increases pressure in the glomerulus by creating back pressure
- The total pressure on the blood forces most of the fluid into the capsule - To filter the blood, the blood pressure must overcome the pressure of the fluid already in the capsule (capsular pressure) as well as the osmotic pressure of the blood itself
- If the systolic pressure drops below 60 millimeters Hg, blood in the glomerulus will not be forced through the glomerular wall
- Because glomerular pressure will not rise high enough to force plasma from the blood vessels
