1. Kidney - produces urine

2. Ureters - transports urine fr. the kidney to the bladder

3. Urinary bladder - provides a temporary storage reservoir for urine; 700-800ml capacity

4. Urethra - transports urine fr. the bladder out of the body

- controls composition and volume / pressure of blood by regulating:

- blood ion composition (Na+, Cl-, Ca2+, etc)

- blood osmolarity (+300mOsm/L - dissolved solutes)

- controls blood pH - regulation of H+ and HCO3-

- regulates blood glucose levels (gluconeogenesis)

- removes wastes fr. the blood (urea, uric acid)

- production of hormones (calcitrol and erythopoitin)

1. renal capsule - deep fibrous layer

- continuous w/ outer coat of ureter

- barrier against trauma and infection

- maintains kidney shape

2. adipose capsule

3. renal fascia

1. renal cortex - outer zone of the kidney

- renal columns are portions of cortex that extend bet. renal pyramids

2. renal medulla - inner region

- several renal pyramids

- collecting duct

- papillary duct in renal pyramid

- minor calyx

- major calyx

- renal pelvis

- ureter

- urinary bladder

- renal artery

- segmental arteries

- interlobar arteries

- arcuate arteries

- interlobular arteries

- afferent arterioles

- glomerular capillaries

- efferent arterioles

- peritubular capillaries

- interlobular veins

- arcuate veins

- interlobar veins

- renal vein

- structural and functional units of kidney that form urine

- each kidney contains = 1 mil nephrons

- consists of a vascular and tubular component

1. Renal corpuscle - filters blood plasma

a. glomerulus - capillary network

b. bowman's capsule

2. Renal tubule

a. proximal convoluted tubule

b. loop of Henle (descending & ascending)

c. distal convoluted tubule

1. cortical nephrons - most common

2. juxtamedullary nephrons - loops of Henle extend into the medulla

- formation of very concentrated urine

1. glomerular filtration

- filtration fr. blood plasma into nephron

2. tubular reabsorption

- fr. fluid in renal tubule into blood

3. tubular secretion

- fr. blood into fluid in renal tubule

- the use of pressure to force fluids and solutes through a membrane

- a passive event cause by:

- very efficient because:

- the porous capillaries, along w/ capsule cells (podocytes) are permeable to H2O and small solutes but not to blood cells or large mol. such as plasma proteins

- blood pressure that is greater in capillaries than the fluid pressure in the capsule

- pressure forces fluid (filtrate) into the capsule

1. capillaries present a large surface area

2. the filtration memb. is thin and very permeable

- 105-125 mL/min of fluid that is isotonic to blood

- substances include H2O and all solutes present in blood (except proteins) including ions, glucose, amino acids, creatinine, uric acid

1. constriction or dilation of the AFFERENT and EFFERENT arterioles regulates:

a. blood flow in & out of the glomerulus

b. glomerular capillary surface area available for filtration

2. if the filtration rate is too HIGH

- essential subs. can't be reabsorbed quickly enough and are lost in the urine

3. if the filtration rate is too LOW

- everything is reabsorbed, including wastes that are normally disposed of

1. renal autoregulation

- under normal cond., nephrons can adjust their own filtration rate and blood flow

- this ensures stable fluid & electrolyte bal. in body in spite of significant changes in BP

2. neural regulation

3. hormonal regulation

- 99% of H2O & most of the solutes of the filtrate are returned to the blood stream

- 65% reabsorption takes place in PCT

- 16% of filtrate reabsorbed fr. the loop of Henle

- 10-15% of filtrate is reabsorbed in the DCT

- 5-9% reabsorbed in collecting duct

- all organic nutrients are reabsorbed

- H2O & ion reabsorption is hormonally controlled

- may be an active (requires ATP) or passive process

- Na+ reabsorption almost always active

Proximal Convoluted Tubule

REABSORPTION

- reabsorption (into blood) of filtered:

- H2O = 65% by osmosis

- Na+ = 65% by Na/K pump, symporters, antiporters

- K+   = 65% by diffusion

- Glucose = 100% by symporters & facilitated diffusion

- Amino acids = 100% by same above

- HCO3- = 80-90% by facilitated diffusion

- Urea = 50% by diffusion

Loop of Henle

REABSORPTION

- reabsorption (into blood) of:

- H2O = 15% by osmosis in descending limb

- Na+ = 20-30% by symporters in ascending

Early Distal Convoluted Tubule

REABSORPTION

- reabsorption (into blood) of:

- H2O = 10-15% by osmosis

- Na+ = 5% by symporters

- Cl-   = 5% by symporters

Late DCT and Collecting Duct

REABSORPTION

- reabsorption (into blood) of:

- H2O = 5-9% stimulated by ADH

- Na+ = 1-4% stimulated by aldosterone

- HCO3- = variable amnt., depends on H+ secretion

- Urea = variable

- some subs. are actively secreted fr. blood into tubules for excretion

- H+, K+, ammonia, creatinine, drugs, etc.

1. disposing of subs. not already in the filtrate

2. eliminating unwanted subs. such as urea & uric acid

3. ridding the body of excess K+

4. controlling blood pH

- H+ = variable by antiporters

- NH4+ = variable, increases in acidosis by antiporters

- Urea = variable by diffusion

- Creatinine = small amount

LATE DCT & COLLECTING DUCT

SECRETION

- K+ = variable amount

- H+ = variable amounts to maintain acid/base homeostasis

- ADH levels control concentration of fluid in collecting

LOOP OF HENLE

SECRETION

1. descending

- permeable to H2O

- impermeable to NaCl

2. ascending

- contains active transport mechanisms to reabsorb Na+

- impermeable to H2O

*H2O is not automatically coupled to reabsorption of solutes in this structure

*Independent regulation of both vol. & osmolarity of body fluids

1. Antidiuretic hormone

a. regulates H2O reabsorption by increasing the H2O permeability of cells in DCT & collecting duct

b. produced in the hypothalamus & released by the posterior pituitary

c. main stimulus for ADH release is an increase in plasma osmolarity

2. Aldosterone

a. stimulation of Aldosterone secretion is due to a decrease in blood vol: decrease in plasma Na+, increase in plasma K+

b. juxtaglomerular cells secrete the enzyme RENIN into blood

c. blood pressure decrese: RENIN > angiotensin II > aldosterone

- through NEGATIVE FEEDBACK

- results of ADH action:

- blood vol. increases

- blood osmolarity falls

- urine vol. decreases

- urine solute conc. increases

- so the release of ADH is triggered when osmoreceptor cells in the hypothalamus detect an increase in the osmolarity of the blood

- the osmotic conc. of a solution

- total # of solute particles per liter (mOsm/L)

- body fluids = 300 mOsm/L

- stimulates:

- reabsorption of Na+ and Cl-

- H2O reabsorption

- secretion of K+ & H+ in the collecting ducts

- consequences:

- decreased H2O excretion (urine vol.)

- increased Na+ and Cl- conc. in blood

- an increased blood vol.

*juxtaglomerular apparatus (JGA) responds to low blood vol. or blood p. (due to dehydration or loss of blood)

- both increase H2O reabsorption

- but ADH responds to an increase in blood osmolarity due to dehydration or salty foods

- while Aldosterone responds to a decrease in blood p. / blood v. due to loss of blood through injury or diarrhea

- increase in plasma K+

- filtrate is diluted in the ascending loop of Henle

- created by allowing this filtrate to continue into the renal pelvis

- occurs as long as ADH secretion is kept very low

- due to increase in ADH secretion

- causes an increase in the aquaporins in the memb. of the cells lining the DCT and CD

- in the presence of ADH, 99% of H2O in filtrate is reabsorbed

- 95% H2O and 5% solutes

- nitrogenous wastes: urea, uric acid, creatinine

- normal solutes: Na+, K+, HPO3-, sulfate ions, Ca+, Mg+, HCO3-

1. stretch receptors

- signal micturition center in sacral spinal cord to trigger micturition reflex

2. micturition reflex

- reflex signal to smooth muscle in bladder wall, & to internal sphincter

3. involuntary: bladder wall contracts while internal sphincter relaxes

4. voluntary control: external sphincter relaxes then urine is voided

1. hemodialysis

2. peritoneal dialysis

3. renal transplantation

- when kidneys are impaired the blood needs to be filtered by artificial means to regulate blood composition

- haemodialysis, peritoneal dialysis

- blood is pumped fr. the arteriovenous fistula into a dialyzer

- in the dialyzer, waste products filter fr. the blood thru an artificial memb. into a fuild called the dialysate

- purified blood is pumped fr. the dialyzer into the arteriovenous fistula

- fluid drains or is pumped into the peritoneal space

- fluid and waste products are drained fr. the peritoneal space

- anticoagulants need to be added to the blood

- slow process 15 hr per week

- bet. treatments symp. of uremia reappear

- risk of blood-borne infections

- risk of peritonitis

- placed in the pelvis, below iliac crest

- most satisfactory solution for patients w/ irreversible kidney failure

- tissue typing needs to be done to find a good match bet. donor and recipient

- immunosuppressive drugs are given to reduce tissue rejection

- total absence of urine

- blood in the urine

- urinary stones

- kidney disease

- glomerular infection

- glucose in the urine

- diabetes mellitus

- high blood glucose and ineffective glucose reabsorption

- bile in the urine

- obstruction of bile duct

- increase amnts of bilirubin in blood excreted in urine

- leukocytes & pus in urine

- infection in urinary tract

- infection in reproductive tract in males

- albumin in the urine

- renal disease

- renal complicaitons of hypertension/heart f

- heavy exercise

- fever

- acetone and ketones in urine

- diabetes mellitus

- starvation

- inflammation of the glomerulus

- ff. acute resp. infections in children

- chronic in older people assoc w/hypertension

- accompanied by proteinuria, haematuria, edema & decreased urine output

- degenerative changes in the kidney

- charac. by proteinuria & edema

- common in children

- inflammation of the urinary bladder

- pain

- urgency to urinate

- frequent urination