Digestion/Nutrition/Kidneys Flashcards
Anatomy of the liver
- 4 Lobes
- Right and left on anterior side
- Caudrate & Quadrate (inferior to caudrate near gallbladder) on posterior side
- Gallbladder sits on underside of liver
Cell Types of the liver
- Hepatocytes - most liver functions belong to these cells
- Kupfter Cells - immune cells of the liver
Blood flow through liver
- Liver recieves blood via :
- Hepatic Portal vein - 75% (blood coming from spleen and GI tract)
- Hepatic Arteries - 25% (arterial blood)
- liver recieves 50% of oxygen demand from both sources
- Portal Vein ⇒ Sinusoids (capillaries of the liver) ⇒ Central vein (drain of the liver) ⇒ IVC (inferior vena cava)
Hepatic Portal System and Portal Hypertension
- Normal Hepatic Portal Pressure = 3-10mmHg
- Portal Hypertension
- Pressure > 10mmHg
- disorder that impeeds or obstructs bloodflow from liver or any part of the portal system (ex: Cirrhosis, chronic hepatitis)
- Chronic Portal Hypertension causes of collateral circulation which allows
- blood flow to bypass the liver
- toxins to move systemically through the body
2ndary problems to Chronic Hepatic Portal hypertension
- varices - distended collateral veins in lower esophagus (common in alcoholics where vomitting agitates skin and varices, contra indicated with combitube), upper stomach and rectum
- Acites - increased hydrostatic pressure in potal vessels of mesentary (Occurs when hydrostatic pressure in portal vessels exceeds osmotic pressure, blood leads out of capillaries and into Interstitial space)
- Splenomegaly - Spleen recieves blood back up from branch of portal vein.
- hepatic encephalopathy - increase in metabolic waste that is bypassing liver, ie. Elevated levels of Amonia, will accumulate systemically and cause altered mental status.
varices
varices - distended collateral veins in lower esophagus (common in alcoholics where vomitting agitates skin and varices, contra indicated with combitube), upper stomach and rectum
Acites
increased hydrostatic pressure in potal vessels of mesentary
Occurs when hydrostatic pressure in portal vessels exceeds osmotic pressure, blood leads out of capillaries and into Interstitial space
Splenomegaly
Spleen recieves blood back up from branch of portal vein.
Symptoms may include abdominal pain, chest pain, chest pain similar to pleuritic pain when stomach, bladder or bowels are full, back pain
hepatic encephalopathy
increase in metabolic waste that is bypassing liver, ie. Elevated levels of Amonia, will accumulate systemically and cause altered mental status by traveling into brain.
Pt’s who have liver failure or hepatic encephalopathy have to take Lactulose which binds amonia and helps excess to be excreted in feces.
Liver Functions
- synthesis & secretion of bile; hepatocytes secrete bile
- storage of lipids & glycogen
- synthesis and conversion of nutrients
- maintains blood levels of glucose, AA’s, and Fatty Acids
- Storage of iron reserves
- Storage of fat soluble vitamins
- inactivation of toxins
- synthesis of plasma proteins, clotting factors, and angiotensinogen
- phagocytosis of damaged RBC’s by kupfter cells
- Blood storage - recieves 25% of systemic volume
- absorption & breakdown of circulating hormones (Insulin, Epinephrine) and immunoglobulins
- absorption & inactivation of lipid soluble drugs
Hepatocytes
secrete bile (released in response to CCK)
Hepatocytes in liver secret bile which travels via Common bile duct to duodenum
Bile wants to go into duodenum,
if hepatic-pancreatic spchinter is closed,
then bile will back up through cystic duct into gallbladder for storage
Bile
bile which is released in presence of CCK, is released into duodenum where emolsification process can occur
Composed of:
Water
bilirubin
ions
cholesterol
bile salts
bilirubin
is the yellow breakdown product of normal heme catabolism, responsible for yellow color of bruises and straw yellow color of urine, brown color of feces and yellow of jaundice.
Pancreatic lipase
&
Emolsification
Lipids that come out of small intestines come in form of large droplets which cannot be broken down by water soluble means
Pancreatic lipase breaks down large droplets into smaler ones
Bile participates in emolsification which breaks droplets down into smaller ones with bile salts to increase the surface area where they can help it be broken down by enzymes
Bile salts forms Phospholipid layers around small lipid particles (called micelle ) that can then diffuse across the cell membrane into intestines where they are broken down further to form Chylomicrons
Micelles
&
Chylomicrons
Bile salts forms Phospholipid layers around small lipid particles (called micelle) that can then diffuse across the cell membrane into intestines where they are broken down further to form Chylomicrons
**Chylomicrons are one of the five major groups of lipoproteins (chylomicrons, VLDL, IDL, LDL, HDL) that enable fats and cholesterol to move within the water-based solution of the bloodstream
**Chylomicrons transport exogenous lipids to liver, adipose, cardiac, and skeletal muscle tissue, where their triglyceride components are unloaded by the activity of lipoprotein lipase
Chylomicron and lacteal in Small intestines
once chylomicron is in lumen of small intestine
can be absorbed into lacteal and travel in lymphatic system until
eventually it dumps into the blood capillary network
Gall Bladder
- Muscular pouch on the underside of the liver
- Primary function is to store bile
- Releases bile in response to CCK
- guarded by hepatopancreatic sphincter
Gallstones (Cholelithias)
&
Cholecystitis
Cholelithias are caused by too much bile
Cholecystitis - inflammation of gallbladder
Large Intestine anatomy
- 5’ Long & 3” in diameter
- 3 basic parts
- Cecum no significant function cecum in cows is for digestion of grass)
- Colon
- Rectum
- Joins with last part of small intestine(illuim) @ ileocecal valve
- Cecum
- Ascending colon (processing speed: Slow)
- Transverse colon (processing speed: Fast)
- Descending colon (processing speed: Fast)
- Sigmond colon
- Rectum
- Anus
Hausta
pouches of Lg Intestine that can expand to accomidate large amounts of fecal matter
Large Instestine Primary Functions
- Reabsorbtion of water and compaction of feces
- Absorbtion of vitamins
- Storage of fecal matter
Large Intestine is responsible for: Absorption, Movement, Defication
5 main things absorbed in Lg intestine
- Water - helps in compaction of feces
- vitamins
- vitamin K (fat soluble; used in synthesis of clotting factors)
- Biotin - water soluble, participates in glucose metabolism
- Vitamin B5 - water soluble; used in steroid synthesis
- Bile Salts - transported back to the liver
- Organic waste
- Toxins
- Amonia
- Hydrogen Sulfide
Rectum
6” long = anal canal
Internal and external anal sphincter
Internal - Involuntary control
External - Voluntary Control
Fat soluble vitamins
A
D
E
K
All others are water soluble
Defication reflex
Positive feedback loop
Arrival of fecal matter causes activation of stretch receptors
Activation of stretch receptors causes Parasympathetic Activation
Parasympathetic activation causes both Distension & Contraction
Which activates Stretch receptors, which activates Contraction & Parasympathetic Activation
Cellular metabolism
chemical reactions that occur in the body occuring in cell
majority of reactions are occuring in either the cytocell or mitochondria
*necessary to maintain life & homeostasis
Anabolism
&
Catabolism
Anabolism and catabolism create a circular series of expectations within the cell drawing from nutrient pool of AA’s, Lipids, Sugars/carbohydrates
Anabolism - creates stored reserves from nutrient pool for maintenance and repair
Prioities for building
- Amino Acids
- Lipids
- Sugars/Carbohydrates
Catabolism - draws from storage for repair and maintenance and production of energy
Priorities for breakdown
- Sugars/Carbohydrates
- Lipids
- Amino Acids
% of energy:
Heat v. ATP
60% of energy is lost to heat in mitochondria
40% is used in production of ATP
ATP is used in body for transport, locomotion, construction, endo/exocytosis, cytokensis
Carbohydrate Metabolism
Areobic Metabolism - O2 is required
vs
Anerobic Metabolism - happens all the time; is able to continue in the absence of O2; it does not require O2 to function
**The whole point of carbohydrate metabolism is breaking down glucose to make ATP
Three Functions of glucose
C6H12O6 ⇒ Heat, 6CO2 + 6H2O, ATP
Three functions of glucose occur in the cytosol and mitochondria of all cells except RBC’s (RBC’s only do glycolosis, because RBC’s transport Oxygen and therefore it cannot use it as well, making system inefficent)
- Glycolosis
- Krebs Cycle (Citric Acid Cycle, Tricarbonic Acid Cycle)
- Oxidative Phosphorylation (electron transport chain, electron transport system)glucose ⇒ ATP
*if glucose is not avaliable we can use fatty acids, glycerol, or AA’s
Glycoloysis
- Breakdown of glucose into pyruvic acid
- Occurs in the cytosol
- problem with glycolosis is it is not fast enough to keep up with the demand for ATP
**all we really need to know**
coenzymes - organic molecules needed to catalyze enzymatic reactions (sometimes vitamins or minerals)
- NAD+ « H
- FAD+ « H
(Hydrogens are added in the process)
C-C-C-C-C-C
6 Carbon chain (passes into cell via facillitated diffusion/carrier mediated diffusion (ie. insulin)
P-C-C-C-C-C-C
Phosphate attached upon entering cell (glucose 6 phosphate) - because it is no longer just glucose, we’ve maintained concentration gradient outside the cell (this way there will always be a higer concentration of glucose out side the cell))
Another Phosphate attaches
P-C-C-C-C-C-C-P
Then splits into two 3 carbon chains where another phosphate is attached to each
P-C-C-C-P P-C-C-C-P
The two phosphates are donated to two ADP molecules per chain to make 4 ATP molecules
Three Carbon chains are known as Pyruvic acid ⇒ used in Krebs Cycle
**If pyruvic acid accumulates it becomes Lactic Acid
Kreb’s cycle
Primary function of Krebs cycle is to remove H atoms from organic molecules and transfer them to coenzymes (NAD, FAD) to be used in Electron Transport Chain
Key Points
- CO2 released
- Hydrogens are borrowed for use in ETC
- a small amount of ATP is made
- Aceytl-CoA is the starting point which is used with other organic molecules instead of glucose
- occurs in the mitochondria
NAD++ and FAD++ carry donated electrons for use in electron transport chain
Effect of cirrculating concentrations of Lactic Acid in the body
can separate Hydrogen ions which can cause acidosis
*Patient who become septic because they have some sort of infection, they have fever, now they poor circulation which will not allow for continuation of Kreb’s cycle leading to accumulation of Pyruvic acid then Lactic acid which will then circulate causing acidosis causing an increase in breathing (hospitals will draw lactate level to determine whether PT is septic or not)
**Rhabdomyolysis - is a condition in which damaged skeletal muscle tissue breaks down quickly; sloughing off of skin, or ruptured blisters; anytime there are cells that are rupturing there is a release of K (party in the cells K) into the blood stream, causing secondary effects
electron transport chain
- is a series of protein complexes embeded in the mitochondrial membrane
- electrons captured from donor molecules in Krebs cycle are transfered through these complexes
- coupled with this transfer is the pumping of hydrogen ions
- this pumping generates the gradient used to synthesize ATP = chemosmosis
**Create H+ = gradient then uses gradient for the synthesis of ATP
Where ETC, Kreb’s cycle and glycolysis occur
- ETC and Kreb’s Cycle occur in the mitochondria
- Glycolosis occurs in the cytosol
If glucose is unavaliable to make ATP
other options:
- Triglycerides can be broken down into fatty acids and glycerol
- 3 fatty acids ⇒ Aceytl CoA
- glycerol (can be converted to) ⇒ pyruvic acid (can be brought into Kreb’s cycle or through backward conversion, made into glucose) ⇒ Acetyl CoA
- Glycogen ⇒ glucose ⇒ pyruvic acid (can be brought into Kreb’s cycle or through backward conversion, made into glucose) ⇒ Acetyl CoA
- Proteins ⇒ Amino acids
- ⇒ Acetyl CoA
- ⇒ pyruvic acid (can be brought into Kreb’s cycle or through backward conversion, made into glucose) ⇒ Acetyl CoA
- ⇒ can be brought directly to Kreb’s cycle
Carbohydrate Synthesis
ie gluconeogenisis - synthesis of glucose from non-carbohydrate precursors
- lactic acid
- pyruvate
- A.A.’s
- glycerol
*once glucose is made we can make glycogen ≈ glycogenesis
*glucose can only be made in certain cells - ie liver & kidney
Lipid Metabolism
Triglycerides are one of the most abundant kind of lipids
Lipolysis - breakdown of lipids
Breakdown of lipids for the sake of making Energy in form of ATP
- Triglycerides are broken down into 3 fatty acids and 1 glycerol
- glycerol ⇒ pyruvic acid ⇒ into mitochondria for use with Aceytl CoA or in Kreb’s cycle
- fatty acid brought into mitochondria via Beta Oxidation to make acytic acid chains (C-C) which can be used in Kreb’s cycle ⇒ 144 ATP from 1 18 Carbon Fatty Acid
(1 glucose molecule = 32-36 ATP) - Byproduct is Ketone Bodies or Ketone Acids
DKA
Ketone Bodies/Ketones ≈ Ketones are acids which will release H+ into the bloodstream causing shift in pH ⇒ CO2
Lipid Synthesis
Fatty Acids + glycerol = Triglycerides
- Fatty acids obtained from either diet or from Acytel CoA
- Glycerol obtainied from intermediates from glycolosis
High Density Lipo-Proteins
vs
Low Density
High-density lipoprotein (HDL) is one of the five major groups of lipoproteins, which, in order of sizes,
largest to smallest, are
chylomicrons
VLDL
IDL
LDL
HDL - densest because of ratio of lipid/protein
which enable lipids like cholesterol and triglycerides to be transported within the water-based bloodstream.
In healthy individuals, about thirty percent of blood cholesterol is carried by HDL
Low density Lipo- Proteins can be transported to peripherial tissues which in transport it has the opportunity to clog arteries and get stuck, causing circulatory problems
High density Lipo-proteins are transported from the peripherial tissues to the liver. Because of the direction of transport they are not as bad
Protein metabolism
- can be metabolized after broken down into amino acids
- directly into the krebs cycle
- brought into mitochondria to be used with Aceytl CoA
- or converted into pyruvic acid and then into Aceytl CoA
- Transamination (or aminotransfer) is a chemical reaction between two molecules. One is an amino acid, which contains an amine (NH2) group. The other is a keto acid, which contains a keto (=O) group. In transamination, the NH2 group on one molecule is exchanged with the =O group on the other molecule. The amino acid becomes a keto acid, and the keto acid becomes an amino acid.
- Deamination - removes amino group from amino acid ⇒ amino group is converted to amonia then to urea by the liver (hepatic encephalopathy - toxic amonia levels in blood stream due to liver failure - Lactulose is medicine that aids in binding amonia for excretion)
- Remainder of amino acid can then be:
- converted to Pyruvic acid (final product of glycolosis/precursor to TCA cycle) or use that for glyconeogenesis (making new glucose from non carbohydrate precursors).
- Converted into Aceytl CoA
- Converted into Keytone Bodies
Protein Synthesis
As Baby
10 essential AA’s (essential in the diet)
8 can be synthesized in the body
20 Total AA’s
As Adult
8essential AA’s (essential in the diet)
12 can be synthesized in the body
Diet and Nutrition
Minerals - inorganic ions - electrolytes salts
ie.sodium, potassium, chloride, calcium,
Many functions: NeuroTransmitter release, blood clotting, action potential, buffer systems,
*Function as cofactors for enzymatic reactions
(ie presence of minerals in Krebs cyle to enable cyle to continue)
Vitamins - essential in the diet, organic nutrients, organically similar to lipids and carbohydrates which can be:
- fat (ADEK) soluble - stored for a long time ie. never are going to run out of them
- or water soluble ( not likely to OD on them, but can develop a toxicity(all others ie B, C, Vitamin H is biotin (synthesis of fatty acids and role in Krebs, B1 Thiamine, B2 Riboflabin, B3 Niacin, B5 pantothenate aka. Aceytl CoA, Muric acid - Vitamin D)
Water
- Suggested to drink 40ml/kg of water daily
- As you increase your body temperature by 1 degree celcius than you are going to lose an extra 200ml of water
- if you increase your metabolic demand you will lose water
- if you increase demands, you must increase intake
Bioenergetics
How organinsms use and aquire energy
usually measured in Calories
cal = Calorie is the amount of energy required to raise the temperature of 1g of water by 1 degree celcius
kcal or Cal = 1000 smaller calories
Lipids ≈ 9 cal/g
Carbs/Proteins ≈ 4 cal/g
Ethanol ≈ 7 cal/g
metabolic rate = sum of anabolic and catabolic reactions that are occuring in body at time of measurment
**Basal Metabolic Rate = ** calculated by height and weight at rest
Thermoregulation
How body mantains homeostasis with regards to temperature
Mechanisms of heat transfer:
Radiation - Transfer of heat in form of infrared radiation
Conduction - physical transfer of heat
Convection - Transfer of heat due to movement of molecules around an object
Evaporation - change of liquid to vapor
Respiration - nose warms air, breathing exchanges warm air with the environment
- insensible respiration - unrealized loss of heat to the environment ie the epithelium and the lungs
- sensible respiration - sensible, something you can feel ie sweating
Hypothalamus
- largely responsible for heat regulation; function is to control fluctuations and keep it stable
- Heat loss center - parasympathetic; when we want to lose heat on purpose
- Heat gain center - sympathetic, to increase in body temperature
If we raise temperature above set point:
Parasympathetic Stimulation
- Vasodilation - widens blood vessels up and brings blood closer to skin to allow radiation & Convection to help bring temperature back down
- Sweating - heat loss via evaporation
- Increase in respiratory rate - more heat from lungs can be lost
If we lower temperature below set point:
Sympathetic Stimulation
*goal = get more heat into body
- vasoconstriction & shunting- tighten bloodvessels down and bring them closer into the body, giving them less opportunity to lose heat with the environment; bring most of blood to the core where it can be kept warm
- Thermogenesis (Shivering) - ie shivering creates heat by violent contraction of skeletal muscles.
- **Dispersion of Hormones (Non-shivering) - ** hormonal stimulation of metabolic rate ie Epi and Thyroxnine
Urinary System aka Renal system
Principal structures & responsibilities
Kidneys - making urine
Ureters - tranfer of urine to bladder via peristalsis
Bladder - stores urine can expand via transitional epithelium
Urethra - expulsion of urine - In/external Sphincters
Renal Functions
Excretion - elimination of stuff we don’t want
Elimination - physical process of getting it out of body
**Homeostatic Regulation ** - regulating BP, Blood volume, Acid-Base Balance, water balance
Regulating that every thing is in the blood in the right concentration or is eliminated accordingly
Some function in terms of detoxification and preservation of nutrients
Location
Top of the kidney is at top of 11th and 12 ribs and remainder is exposed
set retroperitonal in thoracic cavity T12-L3
about the size of a fist
Kidney Gross Anatomy
Direct branch coming off of both the Aorta and IVC for each kidney (Renal Artery and Renal Vein)
Hillum - entrance to the kidney (ie Hillus for lungs)
Nerves -
Ureter - exit for urine from kidneys
Adrenal Glands sit ontop of each kidney - triangle shaped
Outer linings (covering)
Adipose Capsule - fat tissue for cushioning from blows
Renal Fascia - Stabilization of the structure
Renal Capsule - Stabilization of the structure
Internal Kidney Anatomy
Cortex - overall internal structure
Medulla - aka pyramid
Renal Pelvis - dumping basin for urine before it gets moved to ureter
Nephrons straddle cortex and medula
Basic Nephron blood flow
Afferent arteriole (larger)
Enters Bowman’s Capsule, where the Glomerus (capillary network is housed), it exits as the Efferent Arteriole and becomes the peritubular capillaries which surround the proximal and distal tubules the Vasa Recta - are straight capillaries that lie parallel to the loop of Henele.
* There are approximatley 2 Million nephrons in the kidneys
Renal corpuscle
&
Renal Tubule
&
Bowmans Capsule
Renal corpuscle is the initial blood-filtering component of a nephron. It consists of two structures: a glomerulus and a Bowman’s capsule.
Remainder is called Renal Tubules
Proximal Convoluted Tubule (PCT)
Loop of Henele - Decending/Ascending Limb
Distal Convoluted Tubule (DCT)
Collecting duct
Cortical Nephron
Vs
Juxta-Medulliary Nephron
a juxtamedullary nephron is one where the renal corpuscle is close to the medulla, and the proximal convoluted tubule and its associated loop of Henle occur at a deep position compared to most other nephrons.
Tubules are how many cells thick?
How is transport achieved
The tubules are a single layer thick.
Objects must be able to pass through the single cell, or go around, ie inbetween the cells.
25% of blood is routed to the kidneys each minute = 1200-1500 ml’s of blood/minute
in order to filter out
Toxins & Waste Products - kind of big
However we have little stuff that we want to keep
Filtration
Secretion
Reabsorbtion
Filtration - happens in Glomerulus due to hydrostatic pressure exceeding osmotic pressure. It filters out:
- water, salt, glucose, amino acids, and waste products (urea, uric acid, creatitnine);
- we won’t lose plasma proteins (such as hemoglobin and albumin) (negatively charged particals wil pass less frequently than positively charged particles)
Reabsorbtion (into blood vessel out of nephron - ie reabsorbed into the body) - mostly happens in PCT and Loop of Henele
Secretion (into nephron out of blood vessel - ie excretion from body)- mostly happens in the DCT
*Both reabsorbtion happen in both places based on the type of cell that is surrounding that particular tube, better at certain functions than others
Fluids
Once fluid comes out of Bowman’s capsule it is called Filtrate.
Once fluid passes into Proximal Tubule ie is called Tubular Fluid
Once fluid passes through collecting duct it is called Urine.
Primary waste products
Urea
Creatnine
Uric Acid
Things we want to reabsorb/save
Things too large to leave the capillaries
Ions: Ca, Cl, Na, K
Glucose, Amino Acids
Via
Reabsorption = back into the body, ie saving it in the blood vessel
&
Secretion = Excretion from body
*Both can be active and passively transported
Plasma Proteins are too big to leave capillaries which is important because they will help draw back in some of the fluid/stuff we want to keep later
Description of kidney model
Glomerulus - Afferent enters/Efferent exits
Fenestrated Capilary - holes or slits in capillaries, Podocytes exert some control over what is released from capillary.
PCT - Hormone PTH - Ca2+ reabsorbtion
95% of nutrient reabsorbtion & 80% of water reabsorbtion in the loop of Henele
Decending limb of the loop of Henele is permeable only to water
Ascending Limb - Permeable only to salt, concentration of salt wants to leave due to gradient on ascending
**Because of this permeability - concentration gradients work to our advantage
Counter current multiplier allows for continuious reabsorption of water and salt
Countercurrent Multiplier
Phenomenon in the loop of henele that happens because:
Decending limb of the loop of Henele is permeable only to water
Ascending Limb - Permeable only to salt, concentration of salt wants to leave due to gradient on ascending
**Because of this permeability - concentration gradients work to our advantage
Counter current multiplier allows for continuious reabsorption of water and salt
Basic premise of Kidney
to filter out stuff we don’t want in the blood
and get back things that we lost during filtration process
Transport maximum for Glucose
When Blood glucose reaches 180mg/dL, the body cannot physically reabsorb any more glucose, there is an increased loss in glucose causing an increase in water loss.
**glucose given in form of Manitol in hospital setting to draw water out of brain cells, the same way hypertonic saline would, and functions as a diuretic to rid excess water
Reabsorption at Proximal Convoluted Tubule
- Water
- Sodium
- Ca2+
- Cl-
- AA’s
- glucose
- salts
**PCT responsible for most of reabsorbtion
- PTH (parathyroid hormone) is going to promote Ca2+ reabsorption; the absence of PTH promotes additional excretion
Reabsorption in Loop of Henele
- Water reabsorbed in descending limb
- Na reabsorbed in Ascending limb
**Counter current multiplier -
- as we lose water from descending limb, because it is permiable to water and nothing else
- as we move to the ascending limb the salt concentration is now higher realitive to the amount of water
- The salt will now naturally want to fallout of the loop of henele and into the extracellular space
- Because there is now more salt in the extracellular space, water in descending limb will want to move out, causing a continuous circuit of reabsorbtion (positive feedback, more loss of water=greater loss of Na=more loss of water etc)
Distal Convoluted Tubules
(DCT)
- More secretion takes place in DCT than reabsorption
- Primary place for K+ reabsorbtion
- Active secretion of: H+, or Bicarb ions
- if you want to get rid of them on purpose in the Urine
- if we wanted to save more Na we can excrete K or excrete H+ on purpose,
- Can be regulated with the use of hormones - ie. Aldosterone will cause increased Na reabsorption in exchange for secretion of K or hydrogen ion
- (the absence of Aldosterone promotes additional excretion)
**The other half of maintaining Acid-Base balance along with respiration
*Respiratory system is responsible for the minute to minute changes by converting it to carbonic acid then converted to CO2 which can be expelled via respiration.
Collecting Duct
Urine in the collecting duct flows into the renal pelvis, which feeds into the ureter
- In the presence of ADH, aquaporins form to collect water and prevent dieresis.
- The absence of ADH promotes excretion
Glomular Filtration Rate
- approximatley 125ml/min
- volume lost to filtration every minute
- 99% reabsorbed
- indicates efficency of the nephron
*if we have a disruption in bloodflow then it will disrupt the GFR; the bodys interest is to maintain this rate at all costs unless the patient becomes severley hypotensive.
** if drops <80 Systolic; blood flow from nephron goes away completely which leads to kidney failure (approx 2 hours without blood flow)
***Body protects in order (4-6min Heart, Lungs, 10 min Brain, 2hrs Kidneys)
Urine Testing
- Glucose = means bgl is > 180mL/dL
- bilirubin = breakdown of Heme of aging RBC’s
- urobilin = breakdown of Heme of aging RBC’s
- ketones = production of glucose from lipids and Amino Acids
- specific gravity = concentration vs diluted (higher the specific gravity the more concentrated it is)
- pH - 4.8-8 range - how much H+ is excreted
- blood - looked for in trauma
- proteins - indicates a problem with filtration
- nitrates - indicate UTI; presence of bacteria
- leukocytes - indicate UTI; presence of bacteria
Control of Kidney Function
3 ways
- Local
- Neural
- Hormonal
Kidney Function
Local Control
Reactions to minor changes in BP
- Minor Drop in BP
- vasodilation - of the afferent arteriole (increasing the amount of blood flow arriving)
- vasoconstriction of the efferent arteriole (increases hydrostatic pressure and maintains filtration)
- Minor increase in BP
- Stretch causes Vasoconstriction of Afferent arteriole limiting the amount of blood arrival into the glomerulus for filtration
Kidney Function
Neural Control
- any Sympathetic activation causes vasoconstriction of afferent arteriole
- results in decrease in availability of blood; usually as a result as a significant drop in blood pressure (<80systolic) = kidney failure if prolonged
Juxtaglomerular Apparatus
special collection of cells that makes contact with the ascending limb of the loop of Henele, Bowmans capsule and the Afferent arteriole
Contains:
- Mechanical receptors that control SMC in Afferent Arteriole in response to increase in BP
- Chemoreceptors at the Ascending limb of the loop of Henele for reabsorption of NaCl
- Produces Renin enzyme necessary for conversion of Angiotensinogen and activation of Renin-Angiotensin System is activated.
Renin-Angiotensin System (RAS)
or
Renin-Angiotensinogen-Aldosterone system (RAAS)
- is a hormone system that regulates blood pressure and water (fluid) balance
- Angiotensinogen converted to Angiotensin I by enzyme renin
- Angiotensin I is converted to Angiotensin II via ACE (Angiotensin Converting Enzyme)
- Angiotension II is the active hormone that can cause various effects (see Angiotensin II Flashcard)
- Angiotensin II also stimulates the secretion of the hormone aldosterone from the adrenal cortex
*If the renin–angiotensin–aldosterone system is abnormally active, blood pressure will be too high.
There are many drugs that interrupt different steps in this system to lower blood pressure.
These drugs are one of the main ways to control high blood pressure (hypertension), heart failure, kidney failure, and harmful effects of diabetes.
Angiotensin II Effects
- Peripherial Vasoconstriction increases BP systemically, helping to perfuse vital organs
- Constriction of Efferent Arteriole - increases amt of bloodflow to the glomerulus to maintain Glomerular Filtration Rate
- Release of ADH - keeps more water
- Release of Aldosterone/E/NE - keeps more Na ⇒ keeps more water; E/NE promote peripherial vasoconstriction
Atrial Naturertic peptide (ANP)
- opposes Renin-Angiotensin System
- released by cardiac muscle cells in response to Increased BP/Blood Volume
- Decreases reabsorption of Na+ ⇒ increase in Na excreted
- dilation of glomerular capillaries ⇒ increases filtration ⇒ water loss
- inhibits production of renin/aldosterone/ADH
Anatomy and flow of Urine System
From Renal Pelvis (inside Kidneys) urine is moved via peristalsis throught the **Ureter ** (approx 12” long) passes into pelvic cavity to the Bladder where it is stored until expelled
Slits in posterior wall of the bladder allows urine in but does not allow backflow
Bladder consists of 3 layers of muscle called Detrusior Muscle which is responsible via contraction for the expulsion of urine
Urethra is guarded by an internal** (involuntary) and external (voluntary) **sphincter - there must be coordination between voluntary and involuntary muscles for urine to be expelled. Urethra length: 1” in females; 7-8” in males.
Top of Urethra is guarded by the prostate; an enlarged prostate will press on the urethra and make it harder for urine to be expelled ⇒ urine retention
Tissue Layers of the Ureter
From in-to-out
- Layer of transitional epithelium (similar to rugae in stomach which allows for expansion)
- Longitudinal Muscle Layer - similar to intestine
- Circular Muscle Layer - similar to intestine
- *Connective tissue * which is continuious with the Renal Capsule (outer surface of the Kidneys
Micturition (offical name for urination)
Micturition Reflex
- 200ml urine in bladder sends sensory signal via Parasympathetic NS
- Conscious awareness that bladder is full = need to urinate
- Contraction of Detrusior muscle by parasympathetic stimulation
- relaxation of external uretheral sphincter is followed by relaxation of internal uretheral sphincter = urination
If conscious relaxation of external uretheral sphincter does not occcur, detrusior muscles relax, process begins again in 1 Hour
**Capacity of bladder is 1 Liter
Why are diabetics prone to renal failure?
Glucose is caustic to the veins
Chronically high levels of High bgl = increase in excretion of glucose leading to damage in filtration process
Damage casuse fenestrations to enlarge, allowing proteins to pass trough and eventually nothing we want to filter is being filtered leading to need for dialysis to facilitate filtration of blood
