Transcript Excretory System

Excretory System
How to make pee …
Renal Artery
Renal Cortex
Renal Vein
Adrenal Gland
Renal Pelvis
Renal Medulla
Kidney
Ureter
Urinary Bladder
Urethra
• Every Cell in your body produces wastes
• Metabolic waste, not feces (undigested
material)
• Skin excretes water and salts in
perspiration
• Lungs excrete CO2 as a gas
• Liver excretes bile pigments
• Kidneys excrete nitrogeneous wastes in
urine
Role of Kidneys
• Important in protein breakdown (proteins
are amino acid based which is nitrogen
based)
• Nucleotides (metabolic products) are
metabolized to form uric acid
• Uric acid is not very soluble - if it
precipitates out of solution, you have gout
Urea
• H2N ---C---NH2
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What do kidneys do?
• 2 kidneys located high up in the abdomal
cavity
• Purposes • filter blood
• maintain blood volume
• remove waste products
• recover vital substances
• Maintains homeostasis in the body
• Little bit of protection by rib cage
• Covered by tough fibrous cap of
connective tissue - surrounded by adipose
tissue (inside fibrous tissue)
Ureters
• Ureters connect bladder to kidney smooth muscle
• Ureters and bladder made of transitional
epithelium
• Urinary bladder can stretch to
accommodate up to 600 ml or more
(sometimes in excess of 1000ml) (600 ml
is conservative)
• has folds - rugae (like folds of stomach) running throughout is smooth muscle
fibers
• Urethra extends from bladder to outside
the body
• Females urethra is about 1-2” - this leads
to more frequent urinary tract infections
• Male urethra is about 6” - prostate in later
years can enlarge (very often does) which
causes an obstruction in urine flow
• Histology of Kidney
• Bean shaped
3 regions
• Cortex
• Medulla which contains renal pyramids
(appear striated)
• Renal Pelvis (or inner space) - continuous
with ureter
Nephron
• Plasma minus the proteins pass through
filtration cells, then you need to recover
vital molecules - glucose, water, etc.
• over 1 million nephrons
• Nephron is the filtration unit of the kidney made of cells that are specialized for
active transport, diffusion, moving
substances across membranes
Nephron
• Structure of nephron
• cup shaped structure - Bowman’s capsule
• Parts of nephron beyond Bowman’s
capsule
• specialized tube
Bowman’s Capsule
Renal Arteriole
Glomerulus
Capillaries
Loop of Henle
Collecting Tubule
Nephron
• part closest to glomerulus is the proximal
convoluted tubule (closest to renal corpuscle
• Loop of Henley or Henley’s Loop - descending
and ascending limb with a hairpin turn
• Distal convoluted tubule - farthest away from
renal corpuscle
• each has a role in recovery of nutrients and
leads away from nephron to collecting duct and
away
Formation of Urine
• Pressure Filtration
• Blood from arteriole is flowing into
glomerulus, due to bp, filtration
• Everything from plasma that is filterable
leaves through glomerulus - water,
glucose, amino acids, salts, urea, uric acid
and creatinine (nitrogen wastes)
• blood cells, platelets and proteins are not
filtered
• Concentration of water is same as plasma
• Body needs to recover water and nutrients
• Selective Reabsorption
• Almost 180 L of filtrate pass into collecting
tubules per day. 90 - 2L bottles!
• Diffusion and active transport (passive and
active processes)
• water glucose amino acids and salts are
reabsorbed. About 99% of the water is
reabsorbed.
• Region most highly specialized for
selective reabsorption is the proximal
convoluted tubule
• Many mitochondria needed - produce atp
for active transport
• Reabsorption of water
• happens in loop of Henle
• Lower part of ascending limb - dealing with
passive diffusion of NaCl
• Regulate pH of blood by regulating
particular ions
• Beside filtration, keeping good stuff and
getting rid of waste
• Maintaining blood volume
• ADH - Produced in Hypothalamus by
neurosecratory cells, stored and secreted
from posterior pituitary gland
• ADH increases the permeability of the
collecting duct to water so more water can
be reabsorbed.
• Increase Blood Pressure and Blood Volume
• Diuresis - increases amount of water in urine
• Alcohol is a diuretic - decreases production of
ADH
• Believed after effects of alcohol (hangover) is
due to dehydration
• Kidney stones - calcium salts or uric acid
precipitate and form kidney stone