Circulatory Circuit
Absorption and delivery of nutrients O2 uptake and delivery Removes wastes (C02) from tissues
Lymphatic circulation
System of channels and nodes
Reabsorbs fluid that leaks from the vascular network into the interstitium and returns it to the general circulation
Vessels
Arterioles - smooth muscles (contract)
Venules - connective
Capillaries - single layer of epithelial
Explain the circulation of blood through the heart
Blood enters into the right atrium from the superior vena cava then goes through the tricuspid valve into the right ventricle then into the pulmonic valve into the pulmonary circulation into the pulmonary artery then pulmonary vein dumps into the left atrium then mitral valve through the left ventricle goes through the aortic valve into the aorta then clean oxygenated blood into the body
3 layer of arteries and veins
Intima - in contact with blood
Media - smooth muscle (thickest section of arteries)
Adventitia - collagenous connective tissue (thickest section in veins)
Characteristics of lymphatic vessels
Lymphatic vessels have valves to keep flow moving in one direction and is able to contract minimally due to contractile fibers
Principles of flow
Blood flow - movement along a pressure gradient within the vascular bed
Pressure - blood moves from a area of higher pressure (ARTERIES) as it comes from the left side of the heart to an area of lower pressure (VEINS) the greater the difference the greater the blood flow
Resistance - more resistance less blood flow
Poiseuille’s law
Vessel length - double the length increases resistance and decreases flow by 50%. Cut length of vessel in 1/2 we reduce resistance and increase flow by 100%
Vessel Radius - most important factor - if you double the diameter (2cm to 4cm) increase flow 160x (decrease the resistance)
Blood Viscosity - more viscous = more resistance
(Polycythemia or dehydration)
Definition of velocity
how fast is the flow
Parabolic profile of laminar flow
The blood in the center moves faster than blood in the outer layers
What changes blood flow
Turbulent flow - something is interrupting the forward flow of blood - Thrombus or Atherosclerosis
Bruit
Turbulent blood flow you can hear with a stethascope
Thrill
Turbulent blood flow you can feel and hear
What is responsible for plasma colloid osmotic pressure (keeping our fluid in our vessels)
Plasma proteins (albumin and proteins)
An obstruction in lymphatic flow (not vascular flow) allowing fluid to collect in the interstitium
Lymphedema
Thoracic pump
when you take a deep breath in expanding your lungs you are increasing pressure in the thoracic cavity sucking blood through the venous side of the body into the right side of the heart
Lymphatic flow is controlled by
Increasing colloid osmotic pressure and stimulation of contractile fibers (lymphatic pumps)
Blood flow is controlled by central mechanisms mediated by:
Autonomic nervous system
Venous system flow controlled by pressure gradient from veins and venous and thoracic pumps
Intrinsic autoregulatory mechanisms
Extrinsic Mechanisms
Mechanisms outside the blood vessels. Sympathetic nervous system
What does the release of norepinephrine do?
Results in vasoconstriction via Alpha 1 receptors
What does the release of epinephrine do?
Results in vasodilation via the Beta 2 adrenergic receptors
Movement of lymph is enhanced by
Lymphatic pumps Compression of lymphatic channels (increased physical activity) Intrathoracic pressure changes (increased respiratory rate) Lymphatic contractions (increased BP)
What are the kidneys responsible for?
Kidneys are responsible for fluid and electrolyte homeostasis, ridding the body of water and soluble wastes
How much fluid is filtered and reabsorbed via the kidneys?
The kidneys filter 7L/hour of fluid and reabsorb 99%
2 important endocrine fx of the kidneys
Production of erythropoietin and activation of vitamin D (cofactor for intestinal calcium absorption)
What are 2 mechanisms that the renal system performs
Degrades insulin (20%) Produces prostaglandins (potent vasodilators to counteract vasoconstriction of Angiotensin and ADH)
What do the kidneys use ADH for
To maintain plasma osmolality (viscosity or fluid balance)
What do the kidneys use Aldosterone for
To maintain electrolyte balance
What is the purpose of nephrons
Nephrons are the functional units of a kidney they perform all filtration, reabsorption, and secretary functions
What percentage of renal fx and nephrons can you lose without being symptomatic
50% - 1 kidney
Losing or damaging 75-90% of nephrons result in
Serious renal impairment
Every time the creatine doubles you lose what percentage of renal function?
50%
CVA
Costovertebral angle is the external landmark for the kidneys
Location of the kidneys
Retroperitoneal space, under the diaphragm. Right kidney is slightly lower than the left
3 Divisions of the Renal Parenchyma
Pelvis - urinary collecting structures (calyces)
Medulla - middle portion, renal pyramids
Cortex - outer portions (glomeruli and nephron tubules)
What are Nephrons composed of
Glomerulus (capillary tuft, Bowman capsule)
Tubules (loop of Henle)
Glomerulus
Site of filtration, basement membrane prevents cells & large proteins from passing
Indicator of basement membrane dysfunction
Proteinuria
What do proximal convoluted tubules do?
Reabsorb water, electrolytes, and all of the glucose, amino acids, proteins and vitamins
Loop of Henle
Thin descending limb receives filtrate from proximal convoluted tubules and delivers to ascending limb and its permeable to water.
Thick descending limb contains NA, K, and CL that pumps ions into the interstitium. It is impermeable to water
Distal convoluted tubules
Remove electrolytes and performs further reabsorption using aldosterone and angiotensin II to stimulate tubule cells to reabsorb Na and H20. Then ANP keeps us from reabsorbing fluid. Process controls how much salt and water we have reabsorbed. If we save Na we are removing K
What two cells are in the collecting duct?
Principle Cells (P) respond to antidiuretic hormone Intercalated Cells (I) participate in acid base balance by regulating the secretion of acid
GFR value
Normal Hospital >90 Community >60 anything over 90 is abnormal GFR provides info on kidney fx
What determines GFR
Filtration pressure and the permeable surface of the glomerular membrane
Capillary hydrostatic pressure and Bowman capsule oncotic pressure favor filtration
Plasma/capillary oncotic pressure and Bowmancapsule hydrostatic pressure which oppose filtration
What is the most important physiologic regulator of GFR
Blood volume
Increased Blood Volume = increased GFR = extra fluid excreeted
Decreased Blood Volume = decreased GFR = fluid is conserved
How does SGLT2
work to reabsorb glucose in the kidney
Glucose is filtered freely across the glomerular membrane. All filtered glucose is reabsorbed in the proximal tubule by a sodium-dependent cotransporter (SGLT2) If these transporters are overwhelmed by excessive tubular loads of glucose glycosuria results
Should glucose be in the urine
NO if it is there hyperglycemia may be present
Regulation of acid-base balance in the kidneys
Kidneys excrete excess H+ and regulate the concentration of HCO3- (bicarb).
HCO3- is filtered freely through the glomerulus and must be efficiently reabsorbed to maintain acid base balance
Where does the secretion of potassium happen and how is it regulated
In the distal tubules and is regulated by aldosterone which increases K excretion. Aldosterone saves Na and excretes K
When PaCO2 is high (acidosis)
The kidney compensate by excreting more H+ and by creating new HCO3-
When PaCO2 is low (alkalosis)
The Kidneys compensate by excreting some of the filtered HCO3-
Explain RAAS
If there is a low BP the kidneys sense that and produce RENIN then is activated with ANGIOTENSINOGEN (liver) to produce ANGIOTENSIN 1 (mild vasoconstrictor) that is activated by a (ACE) CONVERTING ENZYME in the lungs to make ANGIOTENSIN II (strong vasoconstrictor) which causes the systemic arteries to vasoconstrict and increase BP.
What else does Angiotension II do in the RAAS system
Angiotensin II works on the adrenal cortex which puts out Aldosterone which goes into the collecting tubules and tells the body to reabsorb salt and water which then increases blood pressure
Antidiuretic Hormone (ADH)
AKA Vasopressin TAPWATER HORMONE
Secreted from the posterior pituitary
Increases the permeability of the collecting tubule to water, resulting in increased reabsorption of water and reduced blood osmolality (how concentrated blood plasma is). Reabsorbed water dilutes the blood and reduces osmolality, causing the body to decrease ADH release
If osmolality is too low
ADH secretion is completely inhibited and collection tubules become impermeable to water. Results in a large amount of diluted urine. We dump it
Affects blood volume without affecting blood osmolality
Aldosterone, Angiotensin II, and Natriuretic Peptides
Aldosterone and Angiotensin II increase sodium and water reabsorption at the same time. Natriuretic peptides inhibit their reabsorption
When is renin released
decreased blood flow to the kidneys
reduced serum sodium levels
activation of sympathetic nerves to the juxtaglomerular cells
When are natriuretic peptides
Atrial cells in the heart must be overstretched by excessive blood volume
Inhibits the actions of angiotensin II
Results in loss of sodium and water in the urine
ACE Inhibitors
Diuretic agent that inhibits the formation of angiotensin II and aldosterone.
Loop diuretics
Diuretic agent that block the Na, K, Cl pump in the ascending loop of Henle
Thiazide like diuretics
Block Na reabsorption, excrete K
Erythropoietin
Stimulates erythrocyte development in the bone marrow so anytime the kidneys sense a lack of oxygen in the blood stream they think its lack of blood cells so erythropoietin is produced to make more blood cells
Vitamin D
Metabolized in the kidney to make it a active form of vitamin D for calcium reabsorption in the intestine. If the kidneys sense there is a low serum calcium they will activate more Vitamin D to absorb more calcium through the GI system into the plasma system
Age-related changes in the GI system
Infant - Low GFR (has reduced ability to make concentrated urine
Elderly - Decrease GFR,
Kidneys decrease in size and fx in 40’s by the 60’s it is significant. Decreased renal blood flow. Susceptible to fluid and electrolyte imbalances and renal damage
Specific Gravity
1.005 - 1.030
The higher the specific gravity the more concentrated the urine is indicating dehydration. The lower the SP indicated hydration and dilute urine
Serum Creatine
> 1.0 - 1.2
Used for evaluating medications
BUN
10-20
Increased value indicates decreased kidney function or dehydration
Urine should be…
Pale yellow with a pH of 6
Slightly acidic
The urine osmolality and SG changes throughout the day
How so?
In the morning you are slightly dehydrated with a higher SG
What should you NOT see in the blood?
Protein Glucose Epithelial cells Erythrocytes Leukocytes Bacteria Crystals Stones Casts (WBC/RBCs)
WBC casts are r/t?
Pyelonephritis
RBC casts are r/t?
Glomerulonephritis
What is found in the urine specifically in women b/c of anatomy
Leukocytes
What do epithelial cells casts indicate
Sloughing of the tubular cells (acute tubular cells)