Excretion 5.1.2 Flashcards
What is the difference between excretion and egestion?
-Excretion is the removal of metabolic waste whereas egestion is the elimination of faeces from the body
What are the four main excretory organs?
Lungs, Liver, Skin and Kidneys
How does blood get to and from the liver?
-Oxygenated blood travels to the liver via the aorta and hepatic artery
-Blood removed from the liver to the heart travels along the hepatic vein which joins to the vena cava
-Liver is also supplied by the hepatic portal vein which carries products of digestion from the intestines
What are liver cells called and their adaptations?
-Hepatocytes
-Have large nuclei, prominent Golgi apparatus, many mitochondria (metabolically active cells)
Where is Bile produced and what is it used for?
-Liver
-It is released via bile duct into small intestines to emulsify fats
What do Kupffer cells do?
-Found in the sinusoids(air spaces surrounded by hepatocytes) in the liver
-Act as macrophages ingesting foreign particles
What are the functions of the liver?
-Control blood glucose, amino acid and lipid levels
-Synthesis of bile, plasma proteins and cholesterol
-Storage of vitamins
-Detrofication of alcohol and drugs
-Breakdown of hormones and RBC
Where does the liver store sugars and how does the liver control levels of glucose?
-The liver stores sugars in the form of glycogen granules in the cytoplasm of the hepatocytes
- Homeostatic control, when blood glucose rises, insulin levels rise, stimulating hepatocytes to convert glucose into glycogen and vice versa when they fall except the hormone is glucagon
What enzymes does the liver contain?
-Catalase: converts hydrogen peroxide to oxygen and water
-Cytochrome p450: group of enzymes that breakdown drugs
-Alcohol dehydrogenase: breaks down ethanol into ethanal, ethanal is then converted to ethanoate
What is transamination?
-Conversion of one amino acid to another, this process is carried out by hepatocytes
Describe the process of the ornithine cycle?
-chain of enzyme controlled reactions
1. Ammonia and carbon dioxide combine with ornithine to produce citrulline and water
2. Citrulline is converted to arginine (with the removal of water)
3. Arginine is the re-converted to ornithine by the addition of water and removal of urea
Draw the ornithine cycle?
What does the word renal refer to?
-The kidney
What are the functions of the kidney?
-Osmoregulation
-Excretion
-Filter urea and other mineral ions out the blood excreting them, therefore they help maintain water and ion balance
Draw the gross anatomy of the kidney?
The photo shows a light micrograph of a section through a kidney cortex, label A and B
A-glomerulus
B-Bowemans capsule
Label this cross section of the cortex of a mammal?
A-glomerulus
B-tubule
C-afferent/efferent ateriole
D-Bowemans capsule
Label this photo of a stained section of kidney tissue?
A-microvilli of proximal convoluted tubule
B-lumen of distal convoluted tubule
C-lumen of proximal convoluted tubule
How are hepatocytes adapted?
-Hepatocytes are thin for short diffusion distance
-Fenestrated (tiny openings) to increase permeability
How is blood circulated through the kidney?
-Renal arteries carry unfiltered blood to kidneys, the arteries branch off from the abdominal aorta
-Blood that has been circulated through the kidneys goes out through the renal vein which drains into the inferior vena cava
How does urine collect in the kidney and how does it get to the bladder?
-Urine collects via the renal pelvis
-The ureter carries urine to the bladder where it is stored
What is a Nephron?
-A nephron is a basic structural and functional unit of the kidney
Why is the afferent arteriole larger in diameter than the efferent arteriole and what is the glomerulus?
-This helps maintain a higher hydrostatic pressure in the glomerulus than the bowman’s capsule pushing fluid from the blood in
-The glomerulus is a tangle of capillaries within the bowman’s capsule
What are the three layers of the bowman’s capsule?
-Capillary endothelium: pores allowing blood plasma and dissolved substances to pass out but not RBCs
-Basement membrane: mesh of collagen fibres and glycoproteins that acts as a filter
-Epithelial cells of Bowmans capsule: makes sure cells platelets and plasma proteins don’t enter tubule
What is filtered out of the blood?(Ultrafiltration) and what is left in the cappilary?
-Urea, glucose, Amino acids, water and inorganic mineral ions are filtered out of the blood
-Blood cells and large proteins are left in the cappilary
What is the structure of the proximal convoluted tubule?
-Site of reabsorption
-All of the sugars, most of the mineral ions and most of the water are reabsorbed here
Describe how glucose and amino acids are selectively reabsorbed in the proximal convoluted tubule?
- Sodium ions are actively pumped out of the cells lining the tubule into blood
- Sodium concentration in the cell cytoplasm decreases creating a concentration gradient
- Sodium ions diffuse into a cell through a cotransporter protein- carrying glucose and an amino acid at the same time
4.Water moves into the cell by osmosis - Glucose/amino acids diffuse into the blood and water follows
Draw the structure of a nephron?
What is the structure of the loop of henle?
-A long tubule, the descending limb runs from cortex through medulla to a hairpin at the bottom of the loop
-The ascending limb travels back up through medulla to cortex
What is the structure of the Distal convoluted tubule and the Collecting duct?
-Distal convoluted tubule: permeabillity of walls vary in response to ADH in the blood to regulate water balance, it also contribute to ion and PH balance of the blood
-Collecting duct: Urine passes down duct through medulla to the pelvis, water balance is also controlled as walls are sensitive to ADH
Describe the reabsorption of substances at the proximal convoluted tubule?
-All glucose, amino acids, vitamins and hormones are reabsorbed via active transport
-Some sodium ions are move into medulla tissue by active transport
-Chloride ions and water follow down concentration gradients maintained by the constant flow of blood
Describe the reabsorption of substances in the loop of henle (Descending limb and ascending limb)?
-Descending limb: water moves out of filtrate down a concentration gradient into medulla and capillaries, descending limb is not permeable to sodium and chloride ions
-Thinner ascending limb: very permeable to sodium and chloride ions, they move out by diffusion down a concentration gradient
-Thicker ascending limb: sodium and chloride ions are actively pumped out against a concentration gradient
-The whole ascending limb is impermeable to water
Describe the reabsorption of substances in the distal convoluted tubules?
-Filtrate is very dilute as ascending limb is impermeable to water so water balancing takes place here
-The permeability of tubules vary with concentration of ADH present
-If needed sodium ions can be actively transported out due to the cells lining the distal convoluted tubule containing many mitochondria
What will happen if the body has too much salt and what is the role of collecting duct in reabsorption?
-Excess ions will be excreted in urine
-The collecting duct is the main site where the volume and concentration of urine is determined
Which organ detects changes in water potential in the blood?
Hypothalamus
What is the effect of ADH on the collecting ducts in the kidney?
- Collecting duct has membrane bound receptors for ADH and ADH from blood binds
- The binding causes a chain of enzyme-controlled reactions inside the cell
- This causes vesicles containing water permeable channels (aquaporins) to fuse with cell surface membrane
4.This makes cell more permeable to water so more water is reabsorbed into blood
How do receptors react when water potential falls in the blood?
- Receptors in hypothalamus detect low water potential in blood and stimulate pituatry gland to produce more ADH
- High levels of ADH cause collecting duct to be more permeable to water so more water is reabsorbed and less water reaches bladder
- Small volumes of concentrated urine are produced, reducing water loss
How do receptors react when water potential rises in the blood?
- Receptors in hypothalamus detect high water potential and pituatry gland is stimulated to produce less ADH
- Low levels of ADH cause collecting ducts to become less permeable, so less water is reabsorbed and more water reaches the bladder
- Large volumes of dilute urine is produced, lowering body’s water potential
How and where is ADH produced and how do neurons control when it is released?
-ADH is produced in neurosecretory cells and is stored in vesicles in the posterior pituatry gland
-When osmoreceptor neurones are stimulated nerve impulse are sent from hypothalamus to posterior pituatry gland causing the release of ADH by exocytosis in blood
What kind of control is osmoregulation?
Negative Feedback
What are the causes of kidney failure and which two substances may be detected in urine following kidney damage?
-Causes: Blood loss, high blood pressure, diabetes, overuse of drugs and infection
-Blood and protein will be found in urine following kidney damage
What are some of the effects on the body due to kidney failure?
-Build up of urea, loss of electrolyte balance and high blood pressure
What is GFR and how is it measured?
-The glomerular filtration rate is a measure to indicate kidney disease
-A blood test measuring levels of creatinine can be used to provide an estimate for GFR
What factors affect GFR?
-Diet
-Age (GFR declines with age)
-Gender (men and women have different muscle mass)
What is dialysis?
-A treatment for kidney damage
-Waste products, mineral ions and excess fluids are removed from blood by passing it over a partially permeable membrane, substances diffuse across dialysis membrane down concentration gradient
Describe a kidney transplant?
-Blood vessels of new kidney are joined and ureterer of new kidney is inserted into bladder
-Immunosepressant drugs prevent the immune system from recognising organ as foreign however this reduces its abillity to respond to disease
-Kidney can function for 9-10 years or longer
Which two substances should not be present in urine and what hormone is detected in a pregnants persons urine?
-Glucose and creatine in the urine is a sign of diabetes and kidney damage
-HCG is the hormone found in a pregnant persons urine
How does a pregnancy test work?
Why do athletes use steroids?
-Mimic the action of the male sex hormone, testosterone: which stimulates the growth of muscles
What is the process of testing drugs?
1.Sample is divided into two, first sample is applied to a test strip
2. If positive, the second sample is run through gas chromatography or mass spectrometry to confirm prescence of drug
