NA. 5.2 Excretion Flashcards
What is Excretion?
Process of removing metabolic wastes from the body
What products must be Excreted?
- carbon dioxide
- nitrogen based by-products
- other compounds like bile and faeces
What is Egestion?
the elimination of faeces from the body
Why is Excretion Important?
the organism to maintain its PH balance and regulate osmotic pressure whiles also removing waste that mat become toxic if it builds up
what are some of the Excretory organs?
- The Lungs (excretes respiratory waste)
- The Liver (excretes metabolic & nitrogenous waste)
- The Kidneys (excretes urea to bladder (to be peed out)
- the Skin (excretes hella stuff)
Why would we NOT want CO2 buildup in the blood?
CO2 reacts with water in the blood plasma or Red blood cells to form carbonic acid
this disassociates into H+ ions and hydrogen carbonate ions. These Hydrogen ions then affect the PH
• In plasma it reduces the PH affecting the blood
• In erythrocytes they affect haemoglobins tertiary structure, decreasing its oxygen affinity
• H+ can bind to haemoglobin forming haemoglobonic acid which cant even carry oxygens
• CO2 can bind to haemoglobin forming carbaminoglobin which cant carry oxygens either
What is the liver?
An ORGAN (1) that breaks down harmful substances and toxic waste into less harmful forms, ready to be disposed
What are Liver cells called?
Hepatocytes, cuboidal shaped cells with lots of microvilli
Describe the gross structure of the Mammalian Liver
Liver lobules (cylinders of hepatocytes arranged in rows & connected at the centre) are connected to:
hepatic vein takes deoxygenated blood away from the liver & is attached to → hepatic portal vein: contains products of digestion & hepatic artery: supplies oxygenated blood via Sinusoid capillaries.
And bile duct: transports bile to gall bladder for storage.
Outline the functions of the Mammalian Liver
- Site of gluconeogenesis, glycolysis, glycogenesis.
- Stores glycogen.
- Deaminates excess amino acids, forming ammonia & organic acids. Acids can be respired or converted into glycogen. Ammonia is detoxified by addition of CO2 in ornithine cycle.
- Detoxifies chemicals e.g. converts alcohol to ethanal then acetic acid.
What does the Hepatic Artery do?
carries oxygenated blood from the heart into the liver
What does the Hepatic Vein do?
carries deoxygenated blood into the liver from the digestive system, this is the blood in need of filtration and contains toxic substances in high concentrations
What does the Hepatic Portal Vein do?
carries deoxygenated blood from the liver into the heart
What is the Bile duct?
consist of bile caniculi which join together to form a vessels that carries bile from the liver to the gall bladder where it is stored until use
What are the Interlobular vessels?
the blood vessels that run between the liver lobules (Hepatic Artery & Hepatic Portal Vein)
What are the intralobular vessels?
the blood vessels that run through the liver lobules (Hepatic Vein)
What are Kupfer cells?
Specialised Macrophages in the liver that move about the sinusoids that breakdown and recycle old red blood cells
Where is Bile made?
in the Liver cells
What happens in the sinusoid?
after blood from the hepatic portal vein and artery mix they pass through the sinusoid which is lined with liver cells that remove and return certain substances to the blood
What is the function of the Gall bladder?
Stores Bile
What is the step by step for detoxification of alcohol?
Ethanol+ Ethanol dehydrogenase → Ethanal + 2H
Ethanal+ Ethanal dehydrogenase → Ethanoic Acid +2H
Ethanoic Acid → ecetyl coenzyme A for respiration
*the 2H produced in steps 1 & 2 are used in reducing NAD and forming NADH(reduced NAD)
What is Deamination?
Provide the equation that accompanies the process
the process of removing the amino group from an amino acid, making ammonia and a Keto acid
Amino Acid + O2 → Ammonia + Keto acid
What is the role of the Ornithine cycle?
By combining the highly toxic ammonia with carbon dioxide it can be converted into the less toxic urea and water
Outline the reactions that occur in the Ornithine cycle
Ammonia + CO2 + Ornithine → citrulline + H20
Ammonia + citrulline → Arginine + H20
Arginine + H20 → Urea + Ornithine
Urea formation process equation?
Amino acid → Ammonia + keto acid → Urea
↑ ↑
Deamination Ornithine
What is the Kidney?
the two organs in the body responsible for excretion, the process of removing waste from the blood and producing urine is done here
Describe the gross structure of a mammalian kidney?
looks like an ear
Fibrous capsule: protects kidney.
Cortex: outer region consists of Bowman’s capsules, convoluted tubules, blood vessels.
Medulla: inner region consists of collecting ducts, loops of Henle, blood vessels.
What is Ultrafiltration?
the filtration of the blood at the molecular level under pressure
What is the Afferent Arteriole?
the arteriole from which blood ENTERS the Bowman Capsule, thicker in size than efferent
What is the Efferent Arteriole?
the arteriole from which blood LEAVES the Bowman Capsule and eventually enters the Renal Vein
What is the Glomerulus?
the knot of capillaries surrounded by the bowman’s capsule
What is the Bowman’s capsule?
the sac that encloses the Glomerulus and is involved in ultrafiltration and passes the filtrate to the proximal convoluted tubule
Why is the Afferent arteriole thicker Efferent arteriole?
the difference in diameters ensures that the blood in the capillaries in the glomerulus is under increased pressure
What is a Podocyte?
specialized epithelial cells with finger like projections that cover the outer surfaces of glomerular capillaries
How does the ‘3 step ultrafiltration’ process occur
the filtrate in the glomerulus passes through the
- endothelium of the capillary through fenestrations
- through the basement membrane which only allows things with a relative molecular mass of 69 000 or less
- through the gaps in the podocyte into the lumen of the bowman’s capsule
Where does the bowman’s capsule lead?
from the lumen→ the Proximal convoluted tubule→ the loop of Henle→ Distal convoluted tubule→ collecting duct
What are some things that may be filtered out of the kidney?
- Water
- Urea
- Glucose
- Amino acids
- Mineral Ions
What occurs in the Bowman’s capsule? (3 steps)
High hydrostatic pressure in glomerulus forces small molecules (urea, water, glucose, mineral ions) out of capillary fenestrations AGAINST osmotic gradient.
↓
Basement membrane acts as filter. Blood cells & large molecules (proteins) remain in capillary
↓
The fluid passes between and under the folded membrane of the podocytes
State what happens during selective reabsorption and where it occurs
Useful molecules from glomerular filtrate
e.g. glucose are reabsorbed into the blood.
Occurs in proximal convoluted tubule
Outline the transport processes involved in selective reabsorption.
- Na+ ions activiy pumped out of tubule
- concentrations Na+ in cytoplasm decreases
- Na+ ions diffuse into through co-transport protein with both amino acids and glucose from proximal convoluted tubule lumen to wall
- water moves in by osmosis 5.glucose& amino acids diffuse into the blood
How does the kidney produce urine?
After selective reabsorption, filtrate passes through Loop of Henle, which acts as countercurrent multiplier & then through distal convoluted tubule, where water & mineral ions are reabsorbed.
What happens in the loop of Henle?
- Active transport of Na+ & Cl- out of ascending limb.
- Na+ & Cl- diffue INTO the descending limb
- Osmosis of water out of descending limb
(ascending limb is impermeable to water). - Water potential of filtrate decreases going down descending limb: lowest in medullary region, highest at top of ascending limb.
Explain the role of the distal convoluted tubule
Reabsorption:
• of water via osmosis
• of ions, via active transport permeability of walls is determined by action of hormones
What happens at the collecting duct?
the fluid has a high water potential so it moves out via osmosis into the capillaries
Define Osmoregulation
maintenance of water potential of body fluids via negative feedback homeostatic mechanisms.
Explain the role of the Hypothalamus in Osmoregulation
- Osmosis of water out of osmoreceptors
in hypothalamus causes them to shrink. - This triggers Hypothalamus to produce more antidiuretic hormone (ADH).
Explain the role of the Posterior Pituitary gland in Osmoregulation
Stores and secretes the ADH produced by the Hypothalamus
Explain the role of ADH in osmoregulation
Forms hormone-receptor complex on surface membrane of cells in collecting duct. Triggers activation of cAMP as secondary messenger.
Triggers cellular processes that increase reabsorption of water. Urine becomes more concentrated.
How does ADH increase reabsorption of water?
1.Makes cells lining collecting duct more permeable to water:
Binds to receptor → activates phosphorylase → vesicles with aquaporins(water channels) on membrane fuse with cell-surface membrane.
What are Osmoreceptors?
sensory receptors that detect water potential changes in the blood and shrink if low, stimulating neurosecretory cells in the Hypothalamus(ADH)
What can cause Kidney failure?
- Kidney stones.
- Uncontrolled Diabetes.
- High blood pressure damages capillaries of glomeruli = larger molecules pass into urine.
- Kidney infections cause inflammatory damage = change in glomerular filtration rate (rate at which filtrate flows through kidney).
Describe the effects of Kidney failure.
- Build-up of toxic waste products e.g. urea causes symptoms such as vomiting.
- If kidneys cannot remove excess water from blood, fluid accumulation leads to swelling.
- Disruption to electrolyte balance can make bones more brittle or increase water retention.
Name potential treatments for Kidney failure.
- Renal dialysis: (short-term solution repeated several times a week so toxic waste products do not accumulate).
- Kidney transplant (long-term solution, but difficult to find suitable donor with same blood/ tissue type & patient requires immunosuppressants).
Describe Haemodialysis.
Removes blood from body & pumps it through a machine.
Blood runs countercurrent to dialysis fluid. Artificial membrane separates fluids = diffusion gradient enables molecules to move.
Add blood thinning agent to avoid clotting outside body
Describe Peritoneal dialysis
surgeon implants permanent tube in abdomen
Dialysis fluid is put into body cavity. Exchange of molecules happens across the body’s own peritoneal membrane.
Fluid must be drained and replaced
Evaluate Haemodialysis
+ More effective and efficient at getting rid of waste than peritoneal
+ possible for at home haemodialysis
- Time consuming, cant multitask whilst getting done
-mostly done in hospitals
-must be balanced with carefully monitored diet
Evaluate Peritoneal dialysis
+can be done from home
+fewer dietary and fluid intake restrictions
-Removes less waste than Haemodialysis
- tube permanently in abdomen
-must be balanced with carefully monitored diet
What are the advantages of a Kidney transplant?
- freedom from dialysis
- Improved self image and physically fitter
- improved quality of life
What are the disadvantages of a Kidney transplant?
- need to take immunosuppressants, possibility of rejection
- need to find a suitable kidney match/donor
- need for major surgery (to transplants organ)
- regular check-ups needed to check for signs of rejection
What may glucose in the urine indicate?
- Diabetes
- kidney disease/ failure
- Pregnancy (hCG)
- Anabolic steroids
What Hormones tested for in a pregnancy test?
hCG (human chorionic gonadotrophin)
How do Pregnancy test work?
with monoclonal antibodies that bind to hCG
- pee on stick
- hCG bind to its complementary antibodies with dye
- this antibody complex moves along test stick with urine
- if hCG present the antibody complex binds to the fixed antibodies with die, a blue line forms(test line)
- mobile antibodies with no hCG bind to another site to show the test is working.(control line)
What are steroids what they do?
they increase protein synthesis within cells which results in buildup of cells, especially muscle. Controversial in sport as provides unfair competitive advantages and dangerous side effects
How does the body get rid of proteins?
• in liver by hepatocytes
• hydrolysed by protease
• deamination→ ornithine cycle using NH3 from deamination→ formation of urea
keto acid from deamination used in metabolic process
How does the body get rid of small molecules?
ultra filtered from the blood as they can pass through the basement membrane and gaps in podocytes
How can urine samples be used to test for drugs such as anabolic steroids?
Gas chromatography measures the time it takes for the urine sample to pass through the column compared to the time taken for a steroid to pass through
