LECTURE FIFTEEN

TRANSLOCATION OCCURS IN THE PHLOEM
IT CARRIES THE PRODUCTS OF PHOTOSYNTHESIS
FROM THE SITE OF PHOTOSYNTHESIS IN LEAVES
INTO NON-PHOTOSYNTHETIC TISSUES

TRANSLOCATION ALSO CARRIES MATERIALS FROM
STORAGE IN ROOTS INTO OTHER PARTS OF THE
PLANT

THE PRODUCT CARRIED IS SUCROSE

TRANSPIRATION OCCURS IN THE XYLEM
IT CARRIES WATER AND MINERALS FROM THE
ROOTS THROUGHOUT THE PLANT BODY



THREE FACTORS ARE INVOLVED IN TRANSLOCATION:            

          CYTOPLASMIC STREAMING
          MASS FLOW
          ACTIVE TRANSPORT




TRANSPIRATION IS A FUNCTION OF THE PROPERTIES
OF WATER
   OSMOSIS
   COHESION DUE TO HYDROGEN BONDING




THE EXCRETORY SYSTEM HAS TWO FUNCTIONS
IT REGULATES THE VOLUME AND COMPOSITION
OF BODY FLUIDS
IT HELPS EXCRETE NITROGENOUS WASTES

NITROGENOUS WASTES: AMMONIA, UREA, URIC ACID,
AND CREATINE




PROTOZOA HAVE CONTRACTILE VACUOLES
PLATYHELMINTHES HAVE FLAME CELLS
ANNELIDS HAVE NEPHRIDIA
CRUSTACEANS HAVE GREEN GLANDS
INSECTS HAVE MALPHIGIAN TUBULES
VERTEBRATES HAVE KIDNEYS




THE HUMAN EXCRETORY SYSTEM CONSISTS OF
TWO KIDNEYS, TWO URETERS, THE URINARY BLADDER
AND THE URETHRA

URINE IS PRODUCED CONTINUOUSLY BY THE KIDNEYS
AND TRANSPORTED BY PERISTALSIS DOWN THE
URETERS INTO THE URINARY BLADDER




THE URINARY BLADDER IS HIGHLY DISTENSIBLE

DISTENSION OF THE BLADDER CAUSES
THE MICTURITION REFLEX




INSIDE OF EACH HUMAN KIDNEY IS ABOUT ONE
MILLION FUNCTIONAL SUBUNITS CALLED NEPHRONS

EACH NEPHRON IS MADE UP OF A RENAL TUBULE
AND A BLOOD VESSEL




PARTS OF THE RENAL TUBULE: BOWMAN'S CAPSULE,
PROXIMAL CONVOLUTED TUBULE, DESCENDING TUBULE,
LOOP OF HENLE, ASCENDING TUBULE, DISTAL CONVOLUTED TUBULE, AND COLLECTING TUBULE

THE OUTER REGION OF THE KIDNEY IS THE CORTEX,
THE INNER REGION IS THE MEDULLA

PARTS OF THE BLOOD VESSEL: AFFERENT ARTERIOLE, GLOMERULUS, EFFERENT ARTERIOLE, PERITUBULAR CAPILLARIES, VENULE

THE OPERATION OF THE NEPHRON IS DESCRIBED BY
THREE TERMS:
      FILTRATION
      REABSORPTION
      SECRETION




VARIOUS MOLECULES UNDERGO FILTRATION,
REABSORPTION AND SECRETION TO VARYING DEGREES




THE RENAL THRESHOLD FOR A PARTICULAR WASTE PRODUCT
IS THE CONCENTRATION IN THE BLOOD AT WHICH THE
WASTE PRODUCT BEGINS TO APPEAR IN THE URINE




THE RENAL THRESHOLD REPRESENTS THE ABILITY OF
THE KIDNEY TO RETAIN MATERIALS IN THE BODY




THE RENAL THRESHOLD IS A CONSTANT FOR EACH
PARTICULAR WASTE PRODUCT



THE HUMAN EXCRETORY SYSTEM PRODUCES ABOUT
180 LITERS OF FILTRATE PER DAY

THE KIDNEYS PROCESS THE EQUIVALENT OF 4.5 TIMES
THE TOTAL VOLUME OF BODY FLUID EACH DAY

NORMAL URINE VOLUME IS 1 TO 2 LITERS PER DAY




ANTIDIURETIC HORMONE CONTROLS THE PERMEABILITY
OF THE COLLECTING TUBULE TO WATER
ALDOSTERONE CONTROLS EXCRETION OF SODIUM