Chapter 11 Flashcards
Urinary systems roles
- the urinary system plays a vital role in maintaining homeostasis
- balancing pH levels in the blood
- regulation of blood pressure
- 85% of erythropoietin (EPO) produced to stimulate RBC produced is produced in the kidneys
- Vitamin D production
ETC! (Electron Transport Chain)
Excretion
Processes that remove wastes and excess materials from the body
Different systems excretions
Digestive system: excretes food residue and wastes produced by the liver
Respiratory system: excretes carbon dioxide
Integumentary system: (skin) excretes water and salt
Urinary system: (kidneys) excretes nitrogenous wastes, excess solutes, and water
Urea: waste product of amino acid metabolism
Creatinine: waster product that results from the breakdown of Creatine phosphate
Uric acid: formed from the metabolic processing of nucleotides (Gout)
The kidney regulate nitrogenous wastes and other solutes
- protein metabolism produces nitrogenous wastes
- initially, NH3 (ammonia) is produced during breakdown of amino acids
- liver detoxifies NH3, producing urea
- urea is transported from the liver to kidneys for disposal
Other added solutes regulated by the kidneys
Sodium
Chloride
Potassium
Calcium
Hydrogen ions
Creatinine
Maintenance of water levels
To maintain homeostasis, water input = water output
Kidneys adjust to water output as necessary
Water input: food, drink, metabolism
Water output: lungs, skin, feces, kidneys
Kidneys modify output based on intake and loss
Output varies from 1/2 liter/day to 1 liter/hour
Water from food
- water from food usually occurs for 20-25% of recommended total fluid intake
- fruits and vegetables contain a high amount of water
- butter, oils, dried meats, chocolate, cookies, and other sweets that have a low water content
- lettuce, raw strawberries, cucumbers, watercress, Swiss chard, boiled squash, green peppers, bean sprouts, watermelon, cantaloupe, celery, and raw peaches
Water from liquids
- on average an individual consumes 41 ounces of water daily
- physical activity and thermals tress can increase fluid needs by 5-6 times.
- In the U.S., majority of water intake is not from plain water ,but from a variety of foods and beverages.
- other beverages: 43.6% of total water intake
- water: 31.4% of total water intake - during activities, increased sweating and temperature can contribute to greater water loss (drink more water)
- young children, pregnant and lactating women, the elderly, and people with certain illnesses require increased fluid intake
Alcohol is what
A diuretic
Metabolic water
- breakdown of macronutrient molecules in energy metabolism form carbon dioxide and water
- metabolic water provides about 14% of daily water requirements for a sedentary person
The principal organ of the urinary system
Kidney: Lima bean like structures
- located on either side of the vertebral column and extend from the level of the las thoracic vertebra to just above the third lumbar vertebra
- between the T12 and L3
Primary functions of the kidney
Process blood and form urine as a waste product
Micturition
Urination or voiding of the bladder and waste products
The three primary structures of the kidney
Cortex: outer portion of the kidney
Medulla: inner region of the kidney
Renal pelvis: hollow space in center of kidney where urine collects
Ureters
Muscular tubes that transport urine from kidneys to the bladder
Urinary bladder
Three layers of smooth muscle, lined with epithelial cells
Stores urine (600-1,000ml)
Urethra
Carries urine from bladder to outside of the body
Two sphincters control urination
Detrusor muscle
Made mostly of smooth muscle
Network of crisscrossing bundles of muscle fibers
- circular
- oblique
- lengthwise
Nephrons
Functional units of the kidney
- 1 million nephrons per kidney
Two main part of nephrons:
Renal corpuscle: glomerulus (capillaries); bowman capsule (glomerular capsule)
Renal tubule: proximal consulates tubule; henle loop (nephron loop); distal convoluted tubule
Special blood vessels supply the tubules
- renal arteries supply the kidneys
- blood vessels associated with tubules
Arterioles
Efferent: leave the glomerular capsule
Afferent: enters the glomerular capsule
Capillaries
Glomerular: network within the glomerular capsule
Peritubular: surround proximal and distal tubule
Vasa recta: parallels the loop of henle
Renal vein
Collects filtered blood from the kidneys
Filtration defined
Movement of water and protein-free volutes from plasma in the glomerulus, across the capsular membrane, and into the capsular space
Tubular reabsorption
Movement of molecules out of the various segments of the tubule and into the peritubular blood
Tubes -> Blood
Tubular secretion
Movement of molecules out of peritubular blood and into the tubule for excretion
Tubes <- Blood
Filtration - kidney physiology
- as blood flows through the glomerulus, water and small solutes filter out of the blood into the Bowman’s capsules
- the only blood constituents that do not have cells and most plasma proteins
ow many liters of glomerular filtrate are formed daily
180 liters of glomerular filtrate are formed each day
- with about 99% being reabsorbed (spoilers)
- meaning about 1 L being excreted daily
This filtration occurs due to pressure gradients (high blood pressure in glomerular capillaries)
The two ways that rate of filtration if regulated
- Resting rate under local control that adjusts diameter of afferent arterioles
- stress causes sympathetic nervous system to reduce blood flow to the kidneys
Percentages of kidney physiology
- 100% of filtered glucose, amino acids, and bicarbonate and 50% or urea are reabsorbed
- most tubular reabsorption occurs in proximal tubules
- water reabsorption
- 65-70% occurs in the proximal tubule
- 25% occurs in loop of Henle
- <10% occurs in distal tubule and collecting duct - but this is where water excretion is regulated
Brush border is what
Brush border of microvilli on proximal tubule cells facilitate reabsorption
- reabsorption process starts in proximal tubule
Characteristics of urine
Urine composition varies:
Water intake, exercise, environmental temperature, nutrient intake, health and disease, etc.
Urinalysis
The analysis of urine
- this often provides a number of clues to an individual’s health and/or disease rate
Urine volume
Urine volume varies daily and typically ranges from 1-2L/day
- the kidneys must produce a minimum urine volume of about 500ml/day to rid the body of waste products
Kidney maintain homeostasis in many ways
6 ways
-contribute to maintenance of water balance
-contribute to maintenance of salt balance
-secrete an enzyme involved in Cornell of blood volume and blood pressure
-maintain acid-base balance and blood pH
-regulate red blood cell production via erythropoietin
- active an inactive form of vitamin D
ADH (antidiuretic hormone) regulates what
Water balance
ADH regulating water balance involved what
Hypothalamus: synthesizes ADH
Posterior pituitary gland: releases ADH
Kidneys: responds to ADH
Negative feedback chain regulates what
The negative feedback chain regulates solute concentration of the blood
- involves increasing or reducing ADH secretion, which will modify water reabsorption by the kidneys
- Involves increasing or decreasing thirst
Blood solute concentration High means?
(Low water concentration)
ADH released:
- increase in permeability of collecting ducts to water
- increase in water reabsorbed by kidneys
- decrease in urine production
- increase in thirst
Blood solute concentration low means?
(High water concentration)
ADH inhibited:
- decrease in permeability of collecting ducts to water
- decrease in water reabsorbed by kidneys
- Increase in urine production
- decrease in thirst
Diuresis
High urine flow rate
Diuretic
Any substance that increase the formation and excretion of urine
- lasix (furosemide): medication that reduce blood volume and blood pressure
- used in treatment of congestive heart failure and hypertension
- Caffeine: inhibits sodium reabsorption
- alcohol: inhibits ADH release
Aldosterone
Adrenal hormone that regulates sodium excretion
- Mechanism: increases Na+ reabsorption from the distal tubule and collecting duct
Aldosterone secretion is controlled by?
The renin-angiotensin system
Atrial natriuretic hormone protects against blood volume excess
- another controller of renal sodium excretion
- high blood volume stretched atria of the heart
- atria secretes ANH(atrial natriuretic hormone) and collecting ducts
- Na+ excretion increases
- water follow the Na+
- effect of ANH is opposite to that of aldosterone
Erythropoietin stimulate production of red blood cells
- decrease in amount of oxygen is detected by certain cells throughout the kidney
- O2 sensitive cells in kidney secrete hormones, erythropoietin, in response to a decrease in oxygen
- erythropoietin triggers increase in red blood cell production in the bone marrow
Kidneys activate Vitamin D
-exposure of skin to sunlight causes production of an inactive form of vitamin D from a precursor found in the skin
- inactive forms of vitamin D is transported to liver, where it is modified
- inactive form of vitamin D is then converted to active forms by kidneys
- conversion to active vitamin D in kidneys is influenced by activity of PTH (parathyroid hormone)
Kidneys help maintain acid-base balance and blood pH
-blood pH must try between 7.35 and 7.45
-pH regulated by kidneys, buffers, lungs
-Role of kidneys in pH maintenance
- reabsorption of filtered bicarbonate
- excretion of acid as ammonium (NH4+)
PH balance
-acids and bases continually enter the blood as a result of absorbed food and the metabolism of nutrients at the cellular level
- therefore, a mechanism for neutralizing or eliminating these substances is necessary if blood pH is to remain constant
Sources of pH-influencing chemicals -> metabolism
Carbonic acid - aerobic glucose catabolism
Lactic acid - anaerobic glucose catabolism
Ketone bodies - incomplete breakdown of fats
Sulfuric acid - oxidation of sulfur containing amino acids
Phosphoric acid - hydrolysis of nucleic acids and phosphoproteins
Sources of pH-influencing chemicals -> foodstuffs
Acid forming minerals:
- chlorine, sulfur, phosphorus
- meat, fish poultry, and eggs (high protein)
- some grains (wheat, corn, oats)
Basic-forming minerals:
- potassium, calcium, sodium, and magnesium
- fruits and vegetables
PH control mechanisms
Chemical buffer
- 1st line of defense
- rapid-acting
-immediately combines with any added acid or alkali that enters the body fluids (preventing drastic changed in hydrogen ion concentration and pH)
Physiological buffer
- 2nd line of defense
- slower
- involve removing hydrogen ions from the body (respiration. Excretion (micturition)
Buffers
A substance tat prevents marked changes in pH of a solution when an acid or a base is added to it
Metabolic acidosis
Occurs when blood is acidic due to too little bicarbonate
- most common cause is excessive ketones in the blood
Metabolic alkalosis
Occurs when blood is too alkaline due to too much bicarbonate
- most common cause is following the ingestion of excessive amount of bicarbonate, citrate or antacids.
Acidosis
PH drop - increased H+
- caused by accumulation of acids or loos of bases
Alkalosis
PH rise - decreased H+
-caused by loss of acids or accumulation of bases
Chemical buffer
- 1st line of defense
- rapid - acting
- immediately combines with any added acid or alkali that enters the body fluids
- preventing drastic changes in hydrogen ion concentration and pH
Physiological buffer
- 2nd line defense
- slower
-involves removing hydrogen ions from the body- respiration
- excretion (micturition)
Respiratory acidosis
Occurs when the blood is overly acidic due to an excess of carbonic acid, resulting from too much CO2 in the blood
- common causes include anything that interfere with respiration
Respiratory alkalosis
Occurs when the blood is overly alkaline due to deficiency in carbonic acid and CO2 levels in the blood
- occurs when too much CO2 is being exhaled from the lunges
- hyperventilation
Kidney stones
Crystallized minerals
Block urine flow
Urinary tract infections
- usually caused by bacteria
- more common in women than men because of a shorter urethra
- if untreated, bladder infections may ascend to involve the kidneys
Acute renal failure
- short-term impairment, may be reversible
- potential causes: sustained very low blood pressure, large kidney stones within renal Elvis, infections, transfusion reactions, severe injury, toxin exposure, drug reactions
chronic renal failure
- also known as end stage renal disease (ESRD)
- ESRD: long-term, irreversible damage leading to >60% reduction in functioning nephrons
- patients may have <10% normal filtering capacity
Results when:
- renal tubular cells do not receive the nutrients they need
- glomerular filtration is blocked for too long - diabetes may lead to diabetic nephropathy, which often progresses to ESRD
Polyuria
Excessive urine production
>2.5 L/day
Oliguria
Decreased urine production
300-500 ml/day
Anuria
Virtual absence of urine production
<50 ml/day
What is ADH
Antidiuretic hormone
Increase or decrease of thirst
Influence water reabsorption in kidneys
