I. Basic
urinary system functions
A. Helps maintain homeostasis:
regulate composition of blood/fluids
1) Filter blood
2) Selectively reabsorb
nutrients
3) Excrete remaining water
and dissolved wastes
II.
Invertebrates (tues-thurs class only)
A.
Protonephridia (flatworms)
1. first
specialized excretory system
2. flame
cells and network of tubules perform filtering/reabosorbing/excretion
B. Nephridia
(earthworms: in each segment)
1. Fluids collected
through nephrostome
2. Nutrients reabsorbed,
wastes leave through excretory pore.
III. Verebrates: Mammals
A. True kidneys:
1. Regulate blood
a. ion levels, water content, pH, nutrient retention
2. Secrete hormones
a. Maintain
blood pressure and [O2] in blood
3. Eliminate cellular
waste (eg urea: byproduct of protein metabolism)
IV. Human
urinary system
A. Parts of the human urinary system
1. Kidneys:
a. filter blood,
reabsorb nutrients
2. Ureters
a. Transport urine
away from kidney via peristalsis
3. Bladder
a. Store
urine, capacity about 500 ml
4. Urethra
a. Transport
urine from bladder to outside of body
b. internal (invol) and external (vol) sphincters
B.
Kidney anatomy
1. Renal
Artery: bring blood to be filtered (about 1.25 L per minute)
2. Renal
Veins: carry away filtered blood
3. Solid
outer area where urine is formed (contains neprhons:
1 million/kidney)
1. Renal Cortex
2. Renal Medulla
4. Renal pelvis: collects urine, funnels to ureter
C. Nephron anatomy
1. Glomerulus
2. Bowman’s
capsule
3. Tubule:
Conducting tube (See figure 31-6 in text)
1.
Proximal tubule
2.
Loop of Henle
3.
Distal tubule
4.
Collecting duct
D. Nephron physiology
A. Steps in
function
1.
Filtration: materials forced from glomerulus into bowman’s capsule
a. filtrate: filtered materials
2. Tubular reabsorption
a. water, nutrients returned to blood from proximal tubule,
loop of henle
b. active transport (nutrients), and osmosis by water
3. Tubular secretion
a. wastes, excess substances moved from blood into filtrate
b. happens in distal tubule
4. Concentration
a.
Additional water removed by osmosis from collecting ducts
V. Homeostatic
Functions of the Kidney
A.
Accomplishments of nephrons of kidney:
1. Eliminate waste
2. Balance [Ion]
3. Maintain pH
B. Also
4. Regulate water
balance (see fig 31-8 or 30-8? In old text)
a.
Collecting duct permeability controlled via hormones
1.
ADH from posterior pituitary:
a. increases water reabsorption to
blood
2.
controlled by negative feedback loop
3.
alcohol suppresses ADH production/release
4.
Caffeine interferes with ADH signaling
5. Regulate blood
pressure
a. Low blood
pressureà kidneys release renin
1.
catalyzes formation of angiotensin
a. constricts arterioles, increasing blood pressure
6. Regulate [O2]
in blood
a. Low [O2]
in blood, kidneys release erythropoietin,
1.
increases RBC production in bone marrow