2) Structure and functions in living organisms - excretion Flashcards
Waste products in plants
-oxygen
-carbon dioxide
-water/ water vapour
-other unwanted chemical substances
Plants - Waste products in the day
-when there is sufficient light
-rate of photosynthesis > rate of respiration
-more oxygen released by photosynthesis than used in respiration
-less carbon dioxide released by respiration than used in photosynthesis
-oxygen is in access and a waste product
Plants - Waste products in the night
-when there is inefficient light
-no photosynthesis, only respiration
-no carbon dioxide used
-carbon dioxide is in excess and is a waste product
Plant waste products - water vapour
-water that has been drawn up from the roots in the transpiration stream
-not a waste product of metabolism
Plant waste products - chemical substances
-plant cells can break down molecules into chemical substances no longer required by the plant
-some of these substances cannot be converted into another useful compound and should be removed from the plant
-chemical waste materials - can be stored in dying tissues of a plant
-dying tissue falls off the plant the substances are removed
The kidney functions
-regulate water content of the blood
-excrete toxic waste products of metabolism (urea, salts)
Urinary system functions
-filter waste products from the blood, expel it from the body as urine
-control water levels of the body - osmoregulation
Structure of the urinary system
-two kidneys
-joined to the bladder
-by two tubes - ureters
-urethra - carries urine from the bladder to outside the body
-renal artery - from aorta, delivers oxygenated blood to the kidney
-renal vein - delivers deoxygenated blood from kidney to the vena cava
-draw it
Structure of the kidney
Cortex - the outermost region
Medulla - the inner section of the kidney
Renal pelvis - the tube linking the kidney to the ureter
Nephrons - start in the cortex, loop down into medulla, back up the cortex
-contents of the nephron drain into the renal pelvis and collects there before it flow into the ureter to the bladder
The nephron structure
Made up of a kidney tubule which has several sections:
-Bowman’s capsule
-proximal convoluted tubule
-loop of Henle
-distal convoluted tubule
-collecting duct
-surrounding tubule is a network of capillaries with a knotted section - sits inside the Bowman’s capsule
Ultrafiltration
-Arterioles branch off the renal artery and form the glomerulus inside the Bowman’s capsule
-capillaries get narrower further into the glomerulus
-increases blood pressure
-causes smaller molecules (glucose, water, urea, salts) in the blood is forced out of the capillaries and into the Bowman’s capsule and form a filtrate
Process through the nephron
Bowman’s capsule - glucose, water, urea, salts form a filtrate
Proximal convoluted tubule - glucose reabsorbed
Loop of henle - salts, water reabsorbed
Distal convoluted tubule - filtrate travels to collecting duct
Collecting duct - remaining fluid forms urine, leads to the ureter
Kidney - reabsorption of glucose
-glomerular filtrate enters Bowman’s Capsule
-glucose reabsorbed at the proximal convoluted tubule by active transport
-nephron has many mitochondria to do this
Kidney - reabsorption of water
-filtrate drips through loop of henle
-necessary salts reabsorbed back into the blood by diffusion
-water reabsorbed by osmosis in different amounts depending on how much water the body needs at the time
Importance of osmoregulation
-cytoplasm of all cells and blood plasma largely composed of water
-maintaining water levels is vital to prevent harmful changes in cells
-too much water in the blood - cell lysis (bursting)
-too little water in the blood - cells lose water
Need for ADH
-control of water reabsorption in the nephron is negative feedback
-water content of blood is too high, less water reabsorbed
-if too low, more water reabsorbed
This is controlled by the hormone ADH, released by the pituitary gland in the brain
-affects the permeability of the tubules to water
ADH - water content of blood is too high
-pituitary gland releases less ADH
-collecting ducts become less permeable to water
-less water reabsorbed into collecting ducts of the kidney by osmosis
-kidney produces large volume of dilute urine
ADH - water content of blood is too low
-pituitary gland releases more ADH
-collecting ducts become more permeable to water
-more water reabsorbed into collecting ducts of the kidney by osmosis
-kidneys produce a small volume of concentrated urine
