Excretion Flashcards
Describe the role of the loop of Henlé in osmoregulation
- Filtrate moves into the descending limb of the loop of Henlé. Water moves out of the descending limb by osmosis
- At the bottom of the LoH (hairpin bend) the filtrate has a low water potential as it has a very high concentration of solutes
- Ions rapidly diffuse out of the ascending limb into the medulla which creates a very low WP in the medulla tissues
- Further up the ascending limb, ions (Na+, Cl-) are actively transported out of the ascending limb
- At the top of the collecting duct, there is a very high WP so water moves out of the collecting duct by osmosis
Describe the role of ADH in osmoregulation
- osmoreceptors in the hypothalamus detect a low WP
- sends signal to posterior pituitary gland which secretes ADH
- ADH binds to receptors on the cell surface membrane
- Aquaporins fuse to membrane which increases permeability of collecting duct
- WP increases and returns to set point
Describe the gross structure of the kidney
Cortex, medulla, pelvis
- renal artery, renal vein
State the blood vessels of the liver
Hepatic vein (takes blood away)
Hepatic portal vein (wider, blood from intestines/ digestive system)
Hepatic artery (narrow, blood from aorta - into liver)
State 3 functions of the liver
- glycogen storage
- detoxification
- deamination
Define excretion
Removal of metabolic waste products from the body
Explain each function of the liver
Detoxification
- hepatocytes secrete catalase which breaks down hydrogen peroxide
- hepatocytes release alcohol dehydrogenase
Ethanol —> Ethanal Ethanal —> ethanoate
Ethanol is absorbed and transported in the blood until it reaches hepatocytes
Hepatocytes release enzyme alcohol dehydrogenase which converts ethanol into ethanal
Deamination
- remove amine group from amino acid
- forms ammonia (toxic and highly soluble)
- ornithine cycle
- urea is produced
How do freshwater fish, mammals and birds excrete
Freshwater fish- ammonia
Mammals- urea
Birds- uric acid
Where does ultrafiltration occur
Glomerulus
What happens in ultrafiltration
- Salts, water, urea and glucose diffuse out of the glomerulus into the bowman’s capsule
- WBC’s, RBC’s, platelets are too large to pass through fenestrations in B.C
Afferent and efferent arterioles
What makes up glomerular filtrate
Water, urea, amino acids, inorganic ions
Where does selective reabsorption occur
PCT
What 4 things are selectively reabsorbed
Glucose, water, sodium, amino acids
3 adaptations of PCT
- microvili (large SA)
- mitochondria
- Co transporter molecules
3 things DCT does in selective reabsorption
- pH regulation
- ion reabsorption
- water reabsorption
5 causes of kidney failure
- blood loss
- high BP
- overuse of certain drugs
- infection
- diabetes
What happens if kidneys fail
- urea, water, salts, toxins are not excreted
- this leads to a build up toxins in blood
- less blood is filtered, glomerular filtrate rate decreases
- electrolyte balance is disrupted
What problems occur if electrolyte balance is disrupted
K+ = abdominal cramps, muscle spasms, paralysis, cardiac arrest
Na+ = muscle spasms, general weakness, high BP, disorientation
Define dialysis
Filtering of blood through a partially permeable membrane
Describe the process of Haemodialysis
- blood passes through tubes of dialysis membrane surrounded by dialysate
- blood and dialysate flow in opposite directions - maintain concentration gradient
- lasts ~3 hours
- heparin (blood thinner) is given to prevent blood clots
Drawbacks and side effects of haemodialysis
Drawbacks
- required several times a week for 3 hours
- restricts diet (low salt intake)
- decreases lifespan by 5-10 years
Side Effects
- muscle cramps
- low BP
- weakness
- nausea
What is a kidney transplant
One kidney is replaced by a donor
- donor and recipient must have a compatible blood type
Benefits and drawbacks of kidney transplant
Benefits
+ long term
+ better quality of life & freedom
+ no diet restrictions
+ cheaper
drawbacks
- must take immunosuppressants for life
- not enough donors for demand
- risk of rejection
- risks of surgery
- vulnerable to infection
What 4 molecules/ions can urine testing be used for & problems with them
Proteins - high BP, kidney infection
Glucose/ketones -diabetes
Nitrate ions- bacterial infection, UTI
How are anabolic steroids tested for
- gas chromatography
- mass spectrometry
How do pregnancy tests work
First Zone
Mobile monoclonal antibodies bind to hCG bind to layer of fixed antibodies
Second Zone
Antibodies that didn’t bind to hCG bind to a second layer of antibodies (control line)
What substances undergo detoxification in the liver
- alcohol
- hydrogen peroxide
- lactate
- medicinal drugs
