Download CHAPTER 25 Control of the Internal Environment

CHAPTER 25
Control of the Internal
Environment
internal homeostatic mechanisms
Thermoregulation maintains the body
temperature within a tolerable range
Osmoregulation controls the gain and loss of
water and dissolved solutes
Excretion is the disposal of metabolic wastes
Excretion
 Function: Maintain
homeostasis
 *Nitrogenous wastes:
1. ammonia (most
toxic)
2. urea
3.uric acid (least
toxic)
Metabolic
activity
Respiration
Wastes
CO2 + Water
Dehydration
Synthesis
Water
Certain
metabolic
processes
Mineral salts
Protein
metabolism
Nitrogenous
wastes *
Human Excretion
Must remove cellular metabolic wastes because at high
concentration they are toxic.
Organs of excretion:
1. Lungs:
a. Carbon dioxide and water from aerobic cellular
respiration diffuse from blood into lungs. Excreted when
you exhale
2. Skin:
a. sweat glands- water, salts, & some urea diffuse
from the blood into sweat glands & are subsequently
excreted as perspiration
b. major function of skin is to excrete excess heat
(help maintain body temperature)
Human Excretion
Organs of excretion:
3. Liver:
a. breakdown of red blood cells excreted in
bile
b. detoxification of blood (removal of harmful
substances)
c. urea formation -> nitrogenous wastes are
made of ammonia & carbon dioxide
~ Urea is formed by process called deamination
Human Excretion
 Organs of excretion:
4. Kidney: main excretory organ & main
organ of urinary system
a. located just above waist behind
stomach
b. main function~ filter blood to
expel wastes , regulate salt & water
balance & maintain blood pH
c. urine formation
Thus kidneys play a major role in
maintaining homeostasis
Urinary sytem
 Urine pathway:
Kidney->Ureter->Urinary
bladder->Urethra
Ureters: Tubes that carry
urine from kidneys to
urinary bladder
Urinary bladder: smooth
muscle bag that stores
urine
Urethra: urine passes out of
the body through this tube
Kidney
Ureter
Bladder
Urethra
Closer look at Kidney
 3 parts
1. cortex-outer portion
2. medulla-middle
layer
3. renal pelvis- inner
area
Renal
medulla
Renal
pelvis
Ureter
Renal
cortex
Nephrons
 Microscopic functional
unit of kidney (approx.
1million per kidney)
 Each nephron consists of
a folded tubule and
associated blood vessels
 extract a filtrate from the
blood
 refine the filtrate into a
much smaller amount of
urine
Overview: The key functions of the excretory
system are filtration, reabsorption,
secretion, and excretion
 Filtration
Blood pressure forces
water and many solutes
from the blood
(glomerulus) into the
nephron (Bowman's
capsule) filtrate
Reabsorption
The nephron tubule
reclaims valuable
solutes
Bowman’s capsule
Glomerulus
Proximal tubule
Distal
tubule
Loop of
Henle
with capillary
network
Collect
ing
duct
Overview: The key functions of the excretory
system are filtration, reabsorption,
secretion, and excretion
 Secretion
The nephron removes substances and adds them to the
filtrate
 The product of all of the above processes is
urine, which is excreted
Nephron tubule
REABSORPTION
SECRETION
H2O, other small molecules
FILTRATION
Capillary
EXCRETION
Urine
From blood to filtrate to urine: A closer
look
 The proximal tubule reabsorbs
nutrients
salts
water
 Antidiuretic hormone and other hormones
regulate the amount of salt and water the
kidneys excrete
~ How do caffeine and ethyl alcohol effect urine output?
Diuretic chemicals that inhibit antidiuretic hormone
From blood to filtrate to urine: A closer
look
Controlled secretion of H+ and
reabsorption of bicarbonate ions help
regulate blood pH
Secretion also includes the active
transport of drugs and poisons
Reabsorption of salts and urea promote
the osmotic reabsorption of water
Kidney malfunction
 Kidney disease:
various conditions in
which kidneys are
unable to function
effectively in excreting
nitrogenous wastes
may lead to
Dialysis( artificial
kidney)
Kidney transplant