BIOL 30200 Lecture Notes - Lecture 9: Renal Function, Afferent Arterioles, Efferent Arteriole
27 Feb 2017
School
Department
Course
Professor
Urinary System
Chapter 26
Pages 1019-1020; 1029-1046; 1056
1. Functions Fig. 26.1
Regulation of blood ionic composition: Helps regulate Na +
, K +
, Ca 2+
, Cl -
, and HPO42-
ions.
oSubstances that are needed are reabsorbed while anything else is just left
alone.
Regulation of blood pH: Excretes H +
ions and conserves HCO3-
ions (buffer).
oFrom 7.35-7.45 pH
Regulation of blood volume: Conserves or eliminates urine.
Regulation of blood pressure: Increased renin Renin-angiotensin-aldosterone
pathway Increased blood pressure
Maintenance of blood osmolarity: Relatively constant at 300 mOsm/liter.
Produces hormones – calcitrol which increases Ca2+ absorption which increases the
number of RBCs (Erythropoietin)
Regulation of blood glucose level: Uses gluconeogenesis: glutamine glucose
Excretion of wastes and foreign substances: Ammonia and urea (amino acid
metabolism.
oAlso gets rid of bilirubin, creatinine (Creatine Phosphate), Uric acid (nucleic
acid metabolism)
oWe can get gout from uric acid buildup.
1
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2. Renal physiology Fig. 26.7
This helps nephrons maintain the blood’s volume and composition.
About 1200 mL/min of blood goes through the kidneys.
650 mL go into blood plasma – 120 mL forced into renal tubule
Does this about 60 times a day and absorbs about 20% of the oxygen flowing through
the body.
Nephron: The basic unit making up the kidney, and there are about 1 million of these.
a. Glomerular Filtration: Water and solutes in blood plasma move from glomerular
capillaries glomerular capsule Renal Tubule
a. The blood flow occurs in the renal corpuscle and begins in the afferent arterioles
glomerular capillaries (a huge knot of capillaries)
Efferent arteriole
Peritubular capillaries
b. Tubular Reabsorption: As the fluid goes through the renal tubule and collecting duct,
99% of filtered water and many useful solutes are reabsorbed through the tubule cells.
The water and solutes return to the blood via the peritubular capillaries and vasa
recta. Goes to the systemic blood system.
Reabsorbs things that are just necessary.
c. Tubular Secretion: The tubule and duct cells secrete wastes, drugs, and excess ions
into the fluid as it goes through the collecting duct and renal tubule.
Removes substances from the blood. Only when it is necessary.
d. Three Important Equations.
Free Fraction: Object that is not bond to transport protein
2
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3. Glomerular filtration
The fluid that enters the capsular space Filtration Fraction: Blood plasma in the
afferent arterioles (0.16-0.20)
About 160 L/day in adults and 99% is usually reabsorbed with only 1-2 L excreted as
urine.
a. The filtration membrane Fig. 26.8
A leaky barrier that is made up of endothelial cells and podocytes which encircle the
capillaries.
Fenestrations: Makes it quite leaky; 0.07-0.1 µm wide and allows all solutes minus
blood cells and platelets to filter through.
Mesangial cells: Are contractile cells located along the glomerular capillarie and in
the clefts of afferent and efferent arterioles (in between them).
oHelps regulate glomerular filtration.
Basal lamina: A layer of acellular material between the endothelium and podocytes
made of up collagen fiber as and proteoglycans.
oPrevents filtration of larger plasma proteins.
Pedicels: Thousands of footlike processes on each podocyte.
Filtration slits: Spaces between the pedicels.
oSlit membrane: Permits molecules smaller than 0.006-0.007 µm such as
water, glucose, vitamins, amino acids, ammonia, urea, and ions
Other things should be covered in the lab….
Volume of filtrate: Is much larger in the renal corpuscle than in other capillaries of the
body.
Glomerular capillaries present a large surface area for filtration because they are
long and extensive.
oRelaxed = High glomerular filtration; Contraction of mesangial cells = Low
oFiltration α Surface area
Filtration membrane is thin and porous, only 0.1 µm and 50 times leakier than
capillaries in other tissues. Have large fenestrations.
Glomerular capillary blood pressure is high, because of smaller diameter in
efferent arterioles compared to afferent arteriole which increases resistance
(builds up blood pressure).
3
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Document Summary
Regulation of blood ionic composition: helps regulate na. 2- ions: substances that are needed are reabsorbed while anything else is just left alone. Regulation of blood volume: conserves or eliminates urine. Maintenance of blood osmolarity: relatively constant at 300 mosm/liter. Produces hormones calcitrol which increases ca2+ absorption which increases the number of rbcs (erythropoietin) Regulation of blood glucose level: uses gluconeogenesis: glutamine. Excretion of wastes and foreign substances: ammonia and urea (amino acid. Glucose metabolism: also gets rid of bilirubin, creatinine (creatine phosphate), uric acid (nucleic acid metabolism, we can get gout from uric acid buildup. This helps nephrons maintain the blood"s volume and composition. About 1200 ml/min of blood goes through the kidneys. 650 ml go into blood plasma 120 ml forced into renal tubule. Does this about 60 times a day and absorbs about 20% of the oxygen flowing through the body.
