URINARY SYSTEM AND BODY FLUIDS Flashcards
(28 cards)
Organs of urinary system.
Urinary Tract
2 Kidney
Organs that excrete urine
Urinary Tract Organs that eliminate urine:
ureters (paired tubes)
urinary bladder (muscular sac)
urethra (exit tube)
Urination or Micturation
Process of eliminating urine
Contraction of muscular urinary bladder forces urine through urethra, and out of body
Functions of the urinary system
-1.Excretion (eliminates waste)
-2.Regulate blood volume and pressure
Renin is an enzyme secreted by the kidneys which increases blood pressure. If blood flow through the kidneys is reduced, extra rennin is released and may cause high blood pressure
-3.Regulation of the concentration of solutes in the blood (ion concentration)
-4.Help stabilize blood pH:
By controlling loss of hydrogen ions and bicarbonate ions in urine
-5. Regulation of red blood cell synthesis
Erythropoietin (EPO) controls the rate of red blood cell production in bone marrow. Too little EPO causes anemia
-6. Vitamin D production
Vitamin D ingested from food must be “activated” by the liver and the kidneys before it is able to strengthen bones and help the intestine absorb calcium
Excretion
-Separation of wastes from body fluids and eliminating them
respiratory system: CO2
integumentary system: water, salts, lactic acid, urea
digestive system: water, salts, CO2, lipids, bile pigments, cholesterol
urinary system: many metabolic wastes, toxins, drugs, hormones, salts, H+ and water
Location of the kidneys
Bean-shaped, about the size of a tightly clenched fist
Is about 10 cm long, 5.5 cm wide, and 3 cm thick
Weighs about 150 g
-On either side of vertebral column:
left kidney lies superior to right kidney
superior surface capped by adrenal gland
-Position is maintained by:
overlying peritoneum
contact with adjacent visceral organs
supporting connective tissues
-Both protected by the lower rib cage and
located under the muscles of the back and
behind the parietal peritoneum
Structure of the kidney
3 layers of connective tissue:
Inner layer- Renal capsule
Middle layer- Adipose capsule
Outer layer-Renal fascia
-Is protected and stabilized by 3 concentric layers of connective tissue
-Renal capsule covers outer surface of entire organ
-Adipose capsule: a thick layer of adipose tissue
Renal fascia: fibrous outer layer anchors kidney to surrounding structures
-The hilum
Point of entry for renal artery and renal nerves
Point of exit for renal vein and ureter
(Hilum is located on the medial surface)
Structure of the kidney
Internal Anatomy of the Kidneys
Renal cortex: outer 1 cm
Renal medulla: renal columns, pyramids - papilla
Lobe of kidney: pyramid and it’s overlying cortex
-The two layers of the kidney are the cortex and the medulla
The renal columns extension of the cortex into the medulla between the renal pyramids
Renal pyramids- cone-shaped structures in the medulla
The tips of the renal pyramids project to the minor calyces (urine drains)
-The minor calyces open into the major calyces, which merge and open into the renal pelvis
-The renal pelvis leads to the ureter
Structure of the kidney
Internal Anatomy and Histology of the Kidneys
-The functional unit of the kidney is the nephron
-The parts of a nephron are the renal corpuscle, the proximal convoluted tubule, the loop of Henle, distal convoluted tubule and collecting duct
The renal corpuscle = Bowman’s capsule + glomerulus
Fluid leaves the blood in the glomerulus and enters Bowman’s capsule
The nephron empties through the distal convoluted tubule into a collecting duct
The collecting ducts empty into papillary ducts, which empty into minor calyces
Types of Nephrons
Functional Unit of the Kidney – the Nephron
-Cortical nephrons
85% of total nephrons
Located in the cortex
Loops of Henle do not extend deep into medulla
-Juxtamedullary nephrons (J-G)
Are located at the cortex-medulla junction
Have loops of Henle that deeply invade the medulla
Have extensive thin segments
Are involved in the production of concentrated urine
Bowman’s Capsule
A double-walled layer
-Outer parietal layer of squamous epithelium)
-Inner visceral layer consisting of podocytes
-Podocytes wrap around the capillaries of the glomerulus
Filtering the blood and forming filtrate
The filtration membrane consists of
-Endothelium of glomerular capillaries has pores (fenestrae)
-Basement membrane
-Podocytes (with filtration slits)
Capillary Beds of the Nephron
Each glomerulus is:
- Fed by an afferent (incoming) arteriole and refers to glomerular capillaries inside the Bowman’s capsule
- Drained by an efferent (outgoing) arteriole and enters peritubular capillaries around the proximal and distal tubules - Capillary loops called vasa recta dip down into the medulla
Path of Blood Through Kidney
Renal artery
Segmentals- divisions of renal
Interlobars –up renal columns, between lobes
Arcuates –over pyramids in junction of medulla and cortex
Interlobular -up into cortex
Afferent arterioles
Glomerulus
Efferent arterioles
Peritubular capillaries-around PCT and DCT
Vasa recta- around loop of Henle
Interlobular veins Arcuate veins Interlobar veins→ Renal vein
Processes involved in urine formation
The kidneys filter the body’s entire plasma volume 60 times each day
Nephrons remove wastes from the blood and regulate water and electrolyte concentrations
Urine is produced by the processes of
Filtration-Occurs in renal corpuscle (glomerulus)
Tubular reabsorption-Tubular reabsorption occurs via three mechanisms:
Osmosis
Diffusion
Active Transport.
Tubular secretion-Substances are secreted in the proximal or distal convoluted tubules and the collecting ducts
-H+ ions, K+, and some substances not produced in the body are secreted by active or passive transport
Ammonium ions (NH4+) trough diffusion
Creatinine
Urea
Some hormones
Some drugs (e.g. penicillin)
- Filtration is the movement of materials across the filtrationmembrane into the Bowman capsule to form filtrate.
- Tubular reabsorption - solutes are reabsorbed across the wall of the nephron into the interstitial fluid by transport processes, such as active transport and cotransport.
Water is reabsorbed across the wall of thron by osmosis, Water and solutes pass from the interstitial fluid into the peritubular capillaries and vasa recta. - Tubular secretion- solutes are secreted across the wall of the nephron into the filtrate.
Urine Formation
-Filtration
Blood in afferent arteriole is under high pressure
Glomerulus acts as a filter
Filtrate = the substance that is filtered from the blood into the renal tubule
Blood leaves the glomerulus through the efferent arteriole
-Reabsorption
Filtrate contains useful substances which are returned to the blood
Most occurs in the proximal convoluted tubules
-Secretion
Substances move from blood (capillaries) into the filtrate
Important in controlling pH of blood
Urea and Uric Acid Excretion
-Urea
By-product of amino acid catabolism
Plasma concentration reflects the amount or protein in diet
Enters renal tubules through glomerular filtration
Contributes to the reabsorption of water from the collecting duct
-Uric Acid
Product of nucleic acid metabolism
Enters renal tubules through glomerular filtration
Most reabsorption occurs by active transport
~10% secreted and excreted
Urine Composition
0.05% AMMONIA
0.18% SULPHATE
0.12% PHOSPHATE
0.6% CHLORIDE
0.01% MAGNESIUM
0.015% CALCIUM
0.6% POTASSIUM
0.1% SODIUM
0.1% CREATININE
0.03% URIC ACID
2% UREA
95% WATER
- About 95% water
- Usually contains urea, uric acid, and creatinine
- May contain trace amounts of amino acids and varying amounts of electrolytes
- Volume varies with fluid intake and environmental factors
Hormonal regulation of urine: ADH, aldosterone, and ANH
- Pituitary gland and the adrenal glands release hormones
- ADH (antidiuretic hormone) makes the nephron tubules to reabsorb more water back to the blood. As result less water is lost from the body as urine (water retaining hormone)
- Aldosterone (from adrenal gland)- controls the kidney tubules’ reabsorption of salt and water (salt- and water retaining hormone).
- ANH (atrial natriuretic hormone) stimulates the kidney tubules to secrete more sodium and more water (salt- and water losing hormone).
Antidiuretic Hormone (ADH)
-Secreted by the posterior pituitary
-Inhibits diuresis
This equalizes the osmolality of the filtrate and the interstitial fluid
-Increases water permeability in the distal convoluted tubules and collecting ducts by stimulating the insertion
-In the presence of ADH, 99% of the water in filtrate is reabsorbed
Hormonal Regulation of Urine: ADH
ADH regulates blood osmolality by altering water reabsorption
-An increase in blood osmolality or a significant decrease in blood pressure stimulates increased ADH secretion
Increases water reabsorption and as a result
Blood osmolality decreases
Blood volume and blood pressure increase
Urine concentration increases
Urine volume decreases
-A decrease in blood osmolality or a significant increase in blood pressure stimulates decreased ADH secretion
Decreases water reabsorption and as a result
Blood osmolality increases
Blood volume and blood pressure decrease
Urine concentration decreases
Urine volume increases
Hormonal Regulation of UrineRenin—Angiotensin—Aldosterone
- Renin, is an enzyme produced by the juxtaglomerular apparatus, causes the conversion of angiotensinogen to angiotensin I
- Angiotensin-converting enzyme (ACE) converts angiotensin I into angiotensin II, which stimulates aldosterone (steroidal hormone) secretion from the adrenal cortex
Renin—Angiotensin—Aldosterone
Aldosterone regulates the body’s water content by regulating the body’s Na+ content (assuming that ADH maintains blood osmolality)
- A decrease in blood pressure results in increased renin secretion, aldosterone secretion, Na+ reabsorption, blood volume, and blood pressure
- An increase in blood pressure results in decreased renin secretion, aldosterone secretion, Na+ reabsorption, blood volume, and blood pressure
Atrial Natriuretic Hormone - ANH
- Produced by the heart when blood pressure increases and stretches the cardiac muscle
- Inhibits Na+ reabsorption in the kidneys, resulting in increased urine volume and decreased blood volume and blood pressure
- Inhibits ADH secretion and dilates arteries and veins
Effects of Aging on the Kidneys
There is a gradual decrease in the size of the kidney
-Associated with a decrease in renal blood flow
-The number of functional nephrons decreases
Reduced sensitivity to ADH
Renin secretion and vitamin D synthesis decreases
Nephron secretion and absorption declines
Problems with micturition reflex
Homeostasis of Blood Composition
-Excretion of nitrogen-containing compounds
Urea
Uric acid
-Body Fluids: water and electrolyte balance (Na+, Cl-,Ca 2+, K+)
Regulated by hormones
ADH – increases water reabsorption
Aldosterone – increases Na+ reabsorption and amount of K+ secreted
Second effect of aldosterone – increase water reabsorption
Parathyroid hormone-increases extracellular Ca2+
Calcitonin- decreases extracellular Ca2+
-Acid-base balance of blood
Blood pH must be 7.35 – 7.45 (very narrow range)
Tubule cells secrete whatever is necessary into filtrate
Urine pH = 4.5 – 8.0
Body Fluids
- Intracellular fluid is inside cells and makes 2/3 of the total body fluids
- Extracellular fluid is outside cells and includes interstitial fluid (ex: CSF, vitreous humor, synovial fluid) and plasma
