Bio 305: Urinary System

Functions of the kidney

1. Regulation of water, inorganic ion balance, acid base balance

2. Removal of metabolic waste

3. Removal of foreign chemicals

4. Gluconeogenesis

5. Production of hormones

Kidneys use a lot of _____

energy

Hormones made in the Kidneys

1. Erythropoietin

2. Renin

3. Conversion of inactive Vitamin D to active Vitamin D (acts on small intestine to increase calcium absorption)

Erythropoietin (EPO)

hormone secreted by the kidney to stimulate the production of red blood cells by bone marrow (secreted when oxygen levels in the blood are low)

blood doping

inject extra red blood cells before competition to improve performance

3 Most common nitrogenous waste

1. Urea - amino acid metabolism waste

2.Creatinine - Breakdown of creatine phosphate

3. Uric Acid- Metabolic processing of nucleotides

Anatomy of the Kidneys

-2 bean shapes that are red-ish brown

- covered by renal capsule

- Renal artery enters; renal veins and ureter exit

Kidneys have over _______ _______ nephrons

1 million

Nephrons

functional unit, filter blood and produce urine

Nephron's empty urine into one __________ ________

collecting duct

Collecting Ducts empty into _________ _________

renal Pelvis (can't be changed at this point)

structure of nephron that filters blood

interstitial fluid in the kidneys are

salty

cortical nephrons

85% of nephrons; almost entirely in cortex

Boman's capsule

surrounds the glomerulus

juxtamedullary nephrons

-Long nephron loops deeply invade medulla

-Ascending limbs have thick and thin segments

-Important in production of concentrated urine

Where does Urine first begin being filtered

Bowman's Capsule

Loop of Henle

the part of a kidney tubule that forms a long loop in the medulla of the kidney, from which water and salts are resorbed into the blood.

Which loop of Henle is longer ?

Juxtamedullary (it makes the saltiness)

Collecting Ducts are shared by ______ to _____ nephrons

6-8

Collecting ducts drain into the _____ ______ and can not be modified

Renal Pelvis

Apparent atrial

carries blood into the glomerulus

Efferent arterial

Carries blood away from the glomerulus

Glomerulus have smooth muscle and can change their diameter due to _______ and ______ ______ in cordial nephrons

Appharent and Efferent arterials

Path of blood in the cordical nephrons

1. Afferent arteriole enters corpuscle

2. Glomerular capillaries

3. Efferent arteriole leave corpuscle

4. Peritubular Capillaries

5. Drain into venules

3 Basic Renal Processes

1. Glomerular filtration

2. Tubular secretion

3. Tubular reabsorption

glomercular filtration

hydrostatic pressure causes fluid to pass through pores of glomerular capillaries and split pores between podocytes to enter the capsule (about 20% of blood is filtered)

Distal convoluted arterial pass .....

between afferent and efferent arterioles.

renal copuscle

glomerulus and bowman's capsule

Podocytes:

cells in the Bowman's capsule in the kidneys that wrap around capillaries of the glomerulus and make the inner wall

filtration slits

Gaps between podocyte processes surrounding the glomerulus

fenestrated capillaries

have pores in vessel wall; found in kidneys, intestines, and endocrine glands

Things small enough to pass through the filter slits

-water

-electrolytes

-glucose

-amino acids

-fatty acids

-vitamins

-urea

-Uric acid

-creatine

tubular secretion

secretion of solutes from blood in peritubular caps into filtrate tubules

Tubular reabsorption

movement material from filtrate in tubules into blood of peritubular caps

Amount Excreted =

amount filtered + amount secreted - amount reabsorbed

filtration =

secretion =

reabsorption +

nonspecific

specific

specific

Hydrostatic (blood) pressure

favors filtration

Osmotic pressure of glomerulus and hydrostatic pressure of filtrate ______ __

oppose it

GFR=

volume fluid filtered/time (180 liters/day)

Favors filtration:

glomerular capillary blood pressure

opposes filtration

-Fluid pressure in Bowmans capsule

-Osmotic force due to protein in plasma

net glomerular filtration pressure

Pgc - Pbs - πgc

What alters blood flow through glomerular capillaries and leads to changes in GFR

Afferent and Efferent Vasodilation and vasoconstriction

Mesangial cells

contractile cells that help regulate glomerular filtration

Filtered load of substance =

GFR x [substance in plasma]

Reabsoprtion occurs by _____ or ___ ______

diffusion ; mediated transport

if a substance is lipid soluble it can be reabsorbed passively by

simple diffusion of facilitated diffusion

Micturition

Release of urine from bladder, coordinated by combination of smooth and skeletal muscle relaxation / contraction

Sodium and water balance are maintained by

varying urine output

Things that trigger aldosterone

- renal sympathetic nerves (increase) to the JGA cells (increase in Renin)

- JGA cells

- Macula densa in DCT

JGA cells

intrarenal baroreceptors that produce renin

(decrease in blood pressure = decrease in stretch = increase in renin)

macula densa of DCT

Glomerular filtrate rate regulation

(decrease in sodium= paracrine factory - JGA secrete renin)

Renin

hormone (enzyme) secreted by the kidney that raises blood pressure by cutting angiotensin to angiotensin 1

ACE

Cuts angiotensin 1 to 2

Aldosterone increases synthesis of Na+ channels and pumps in the ______ ______ _____

cortical collecting ducts

ADH is produced when there is a drop in ________

blood pressure/volume

ADH

Hormone regulating water reabsorption in kidneys. produced by pituitary gland

What causes the secretion of ADH

-osmoreceptors (decrease in water= increase in plasma osmolarity)

-

Thirst center is in the _________

hypothalamus

ANP (atrial natriuretic peptide)

Secreted in response to excess blood volume in the heart ,(stretch) promotes salt and thus water excretion.

ADH is always low unless you have

low blood pressure