What organs play a role in maintaining blood pressure, blood pH, and composition?
Kidneys
The urinary system is closed associated with the ___________ system.
Reproductive
The parts that make up the internal parts of the urinary and reproductive system…
Share similar pieces of tissue (embyrological development)
Together called urogenital system
What are the organs of the urinary systems?
Two kidneys, two ureters, urinary bladder, and urethra
NOTE
Know more about what he covers in class.
What are the kidney functions?
- Filter blood plasma
- Excrete toxic waste
- Regulate blood, blood pressure, blood osmolarity
- Regulate electrolytes and acid-base balance
- Help regulate calcium
- Secrete erythropoietin
- Secrete calcitrol
- Detoxify free radicals (reactive charged particles that can hurt what they attach to)
Where are the kidneys located?
Retroperitoneal, not in abdomen, lower back, behind peritoneum
Any substance that is useless to the body or present in the excess of the body’s needs
Waste
Waste substance produced by the body’s metabolism
Metabolic waste
How is urea formed?
Proteins
Product of nucleic acid catabolism
Uric acid
Product of creatine phosphate catabolism
Creatinine
Separating wastes from body fluids and eliminating them
Excretion
What are the four body systems that carry out excretion?
Respiratory system
Integumentary system
Digestive system
Urinary system
What is the size and shape of the kidney?
Size: bar of bath soap
Shape: lateral surface is convex, medial is concave with a slit, called the hilum (kidney bean)
Slit on medial (inward) side of kidney; receives renal nerves, blood vessels, lymphatics, and ureter
Hilum
There are three layers on the kidney. What are they?
- Renal fascia: sticks kidney to body wall behind it; holds kidney in place
- Perirenal fat capsule: cushions kidney and holds it into place
- Fibrous capsule: encloses kidney, protec ting it from trauma and infection
Collagen in all three layers.
Glandular tissue that forms urine
Renal parenchyma
Contain/transport urine
Renal sinus
There are two zones of renal parenchyma.
Outer renal cortex
Inner renal medulla:
renal columns (extensions of cortex that project inward toward sinus)
renal pyramids (6-10 with broad base facing cortex and renal papilla facing sinus)
One pyramid and its overlying cortex
Lobe of kidney
Kidneys are only 0.4% of body weight, but receive about 21% of cardiac output
Renal fraction
Renal artery is divided into segmental arteries that become:
Afferent arterioles
Note: Each supply one nephron.
The afferent arterioles end at the __________.
Glomerulus (ball of capillaries)
Drains blood from the glomerulus
Efferent arterioles
What is the difference between afferent and efferent arterioles?
Afferent: going in
Efferent: going out
Most ________ arterioles lead to peritubular capillaries.
Efferent
A network of blood vessels within the renal medulla
Vasa recta
The renal vein empties into the:
Inferior vena cava
Of renal circulation, you need to know renal artery, Rena vein, and the bottom two (chart with the heart)
Know it
The nephron is made of two principal parts. What are they and what do they do?
Renal corpuscle: filters the blood plasma
Renal tubule: coiled tube that converts filtrate into urine
Whatever has been taken out of the blood
Filtrate
The renal corpuscle consists of the glomerulus and a 2 layered glomerular capsule that encloses the glomerulus. What are the layers?
Parietal (outer) layer
Visceral (inner) layer: consists of elaborate cells (podocytes) that wrap around capillaries of glomerulus
Duct leading away from the glomerular capsule and ending at the tip of the medullary pyramid
Renal (uriniferous) tubule
The renal tubule is divided into four regions. What are they?
Proximal convoluted tubule, nephron loop (loop of Henle), distal convoluted tube, and collecting duct
Longest part of renal tubule that is loaded on the inside with microvilli; lots of tubular absorption
Proximal convoluted tubule
Long U-shaped portion of renal tubule; filters more stuff out of blood and absorbs more into blood; adjusts level of salt in blood
Nephron loop
Last part of filtering process of renal tubule
Distal convoluted tubule
What does the urinary system do?
Rids the body of waste products
Three barriers through which fluid passes
Filtration membrane
70-90 nm filtration pores - small enough to exclude blood cells, highly permeable
Fenestrated endothelium of glomerular capillaries
Proteoglycan gel, negative charge, excludes molecules greater than 8 nm
Basement membrane
Almost any molecule smaller than 3 nm can pass ______ through the filtration membrane.
Freely
Filtration pressure depends on _______ and _______ pressures on each side of the filtration membrane.
Hydrostatic; osmotic
High in glomerular capillaries, higher in nephrons
Blood hydrostatic pressure
In capsular space; 18 mm Mercury due to high filtration rate and continual accumulation of fluid of the capsule
Hydrostatic pressure
Amount of filtrate formed per minute by the two kidneys combined
Glomerular filtration rate (GFR)
Total amount of filtrate produced per day equals ___ to ___ times the amount of blood in the body.
50 to 60
What happens if the glomerular filtration rate is too high?
Fluid flows too rapidly through renal tubules, too fast for reabsorption of water and solutes. Causes rise of urine output, and dehydrates body and depletes electrolytes
What happens if the glomerular filtration rate is too low?
Wastes are reabsorbed, azotemia (high levels of nitrogen-containing compounds in the blood) may occur
GFR is controlled by adjusting glomerular blood pressure from moment to moment. The three homeostatic mechanisms to keep control are:
- Renal Autoregulation: enables kidney to maintain stable GFR
- Sympathetic Control: sympathetic nerve fibers richly innervated the renal blood cells
- Hormonal Control: system of hormones that help control blood pressure and GFR
What are the two types of renal autoregulation?
- Myogenic mechanism
2. Tubuloglomerular feedback
Tendency of smooth muscle to contract when stretched (renal autoregulation type)
Myogenic mechanism
Glomerulus receives feedback on the status of downstream tubular fluid and adjusts filtration rate accordingly (renal autoregulation type)
Tubuloglomerular feedback
Patch of slender, closely spaced sensory cells in nephron loop (tubuglomerular regulation)
Macula dense
Modified smooth muscle cells wrapping around arterioles (close to macula densa) (tubuglomerular feedback)
Granular (juxtaglomerular) cells
Might also contract, constricting capillaries and further limiting GFR (tubuloglomerular feedback)
Mesangial cells
Renal autoregulation regulates GFR but cannot keep it entirely ________.
Constant
Active hormone that increases BP
Angiotensin II
PCT reabsorbs about ___% of glomerular filtrate.
65
What are the three steps of urine formation?
- Tubular reabsorption
- Tubular secretion
- Water conservation
The process of reclaiming water and solutes from tubular fluid and returning them to the blood
Tubular reabsorption
What are the 2 routes of reabsorption and how do they occur?
- Transcellular route: substances pass through proximal convoluted tubule epilethial cells and their base
- Paracellular route: Substances pass between proximal convoluted tubule cells, has a solvent drag (water carries dissolved solutes with it)
Reabsorbed fluid is ultimately taken up by ________ ________.
Peritubular capillaries
________ reabsorption is key to tubular reabsorption.
Sodium
Renal tubule extracts chemicals from capillary blood and secretes them into tubular fluid
Tubular secretion
What are the purposes of secretion in the proximal convoluted tubule and nephron loop?
Acid-base balance: secretion of varying proportions of hydrogen and bicarbonate ions helps regulate pH of body fluids
Waste removal: urea, uric acid, bile acids, ammonia, and creatinine are secreted into the tubule
Clearance of drugs and contaminants: morphine, penicillin, aspirin (your kidney disposes of antibiotics fast/multiple doses a day)
Primary function of nephron loop:
Generate salinity gradient that enables collecting duct to concentrate the urine and conserve water
Fluid arriving at the distal convoluted tubule (DST) still contains about ___% of the water and ___% of the salts from glomerular filtrate.
20; 7
Examples of DCT and collecting duct regulation hormones:
Aldosterone, atrial natriuretic, peptide, ADH, parathyroid hormone
The kidney eliminates metabolic wastes from the body, but prevents excessive ______ loss.
Water
As the kidney returns water to the tissue fluid and bloodstream, the fluid remaining in the renal tubules pass as _______, and becomes more concentrated.
Urine
Compares urine sample’s density to that of distilled water
Specific gravity
Ranges from 50 mOsm/L to 1,200 mOsm/L in dehydrated person
Osmolarity
Range 4.5 to 8.2, usually 6 (mildly acidic)
pH
Normal urine volume for average adult:
1 to 2 L/day
Output excess of 2 L/day
Polyuria
Output of less than 500 mL/day
Oliguria
0 to 100 mL/day
Anuria
Retroperitoneal, muscular tubes that extend from each kidney to the urinary bladder
Ureters
What are the 3 layers of the ureters?
Adventitia: connects ureter to surrounding structures
Muscularis: 2 layers of smooth muscle, 3rd layer in lower ureter
Mucosa: transitional epilethium
Muscular sac located on floor of the pelvic cavity
Urinary bladder
Smooth-surfaced triangular area on bladder floor that is marked with openings of ureters and urethra
Trigone
Capacity of urine in the urinary bladder:
500 mL; maximum fullness is 700 to 800 mL
What happens to the urinary bladder if it is not emptied?
Ruptures